Co-reporter:X. P. Gao;Y. Li;G. R. Li;T. Y. Yan;G. L. Pan;H. Y. Zhu
The Journal of Physical Chemistry C March 19, 2009 Volume 113(Issue 11) pp:4386-4394
Publication Date(Web):2017-2-22
DOI:10.1021/jp810805f
Titanate nanofiber, as an important morphology of one-dimensional nanostructured titanate, not only can be regarded as the final product derived from alkaline-hydrothermal treatment of bulk TiO2 but also can serve as initial reactant for fabricating complex functional materials with their parent morphology, which may be difficult to achieve using their bulk material counterparts under mild hydrothermal conditions. Based on titanate nanofiber reactivity, ternary MTiO3 (M = Ca, Sr, and Ba) perovskite oxides with specific morphologies have been fabricated in alkaline solution at low temperature via a soft chemical route. The resulting CaTiO3 products possessed a microtubular structure with rectangular cross-section, while SrTiO3 and BaTiO3 showed the assemblies consisting of aggregated particles in a compact fashion. On the basis of the experimental results, we have proposed two types of growth mechanisms to elucidate the formation processes of CaTiO3, SrTiO3, and BaTiO3 microstructures, respectively. The fabrication of microtubular CaTiO3 undergoes the initial dissolution of titanate nanofibers by Ostwald ripening process to convert into micrometer-sized fiber-bundles, while recrystallization occurs simultaneously until tubular microstrucures are obtained. The formation of SrTiO3 and BaTiO3 microstructures involves ion exchange reaction and in situ growth process at the self-sacrifice of titanate nanofibers framework based on the chemical reactivity. In addition, the photoelectrochemical properties of the as-obtained products are presented, and CaTiO3 microtubes exhibit better photoeletrochemical response relative to SrTiO3 and BaTiO3 microstructures.
Co-reporter:Ye-Zheng Zhang, Zhen-Zhen Wu, Gui-Ling Pan, Sheng Liu, and Xue-Ping Gao
ACS Applied Materials & Interfaces April 12, 2017 Volume 9(Issue 14) pp:12436-12436
Publication Date(Web):March 21, 2017
DOI:10.1021/acsami.7b00389
Microporous carbon polyhedrons (MCPs) are encapsulated into polyacrylonitrile (PAN) nanofibers by electrospinning the mixture of MCPs and PAN. Subsequently, the as-prepared MCPs-PAN nanofibers are employed as sulfur immobilizer for lithium–sulfur battery. Here, the S/MCPs-PAN multicomposites integrate the advantage of sulfur/microporous carbon and sulfurized PAN. Specifically, with large pore volume, MCPs inside PAN nanofibers provide a sufficient sulfur loading. While PAN-based nanofibers offer a conductive path and matrix. Therefore, the electrochemical performance is significantly improved for the S/MCPs-PAN multicomposite with a suitable sulfur content in carbonate-based electrolyte. At the current density of 160 mA g–1sulfur, the S/MPCPs-PAN composite delivers a large discharge capacity of 789.7 mAh g–1composite, high Coulombic efficiency of about 100% except in the first cycle, and good capacity retention after 200 cycles. In particular, even at 4 C rate, the S/MCPs-PAN composite can still release the discharge capacity of 370 mAh g–1composite. On the contrary, the formation of the thick SEI layer on the surface of nanofibers with a high sulfur content are observed, which is responsible for the quick capacity deterioration of the sulfur-based composite in carbonate-based electrolyte. This design of the S/MCPs-PAN multicomposite is helpful for the fabrication of stable Li–S battery.Keywords: electrospinning; lithium−sulfur battery; microporous carbon polyhedrons; polyacrylonitrile; SEI layer;
Co-reporter:Bao Lei, Guo-Ran Li, Peng Chen, Xue-Ping Gao
Nano Energy 2017 Volume 38(Volume 38) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.nanoen.2017.06.001
•A solar rechargeable battery is proposed based on hydrogen storage mechanism.•The hydrogen storage alloy acts as counter electrode and anode in the battery.•The battery shows a new solution of energy conversion, storage and utilization.Solar water splitting is an effective approach to hydrogen production and application of solar energy. However, the photo-generated hydrogen should be initially stored in high pressure cylinder and subsequently applied in hydrogen-oxygen fuel cells. Herein, a solar rechargeable battery is proposed based mainly on hydrogen storage mechanism in dual-phase electrolyte. Specifically, the hydrogen production, storage and utilization are integrated into a hybrid system of the dye-sensitized solar cell and electrochemical cell with the dye-sensitized TiO2 as photo-anode, LiI as the cathode active material in organic electrolyte, AB5-type hydrogen storage alloy as anode in alkaline solution, and PEDOT-modified Nafion membrane as separator. Here, the photo-generated electrons in organic electrolyte pass to the AB5-type hydrogen storage alloy to split water in alkaline aqueous electrolyte for generating hydrogen, which is in situ stored into AB5-type hydrogen storage alloy. Subsequently, the hydrogen stored in the AB5-type hydrogen storage alloy can be oxidized by electrochemical way to generate electricity, coupled with LiI cathode in organic electrolyte. The solar rechargeable battery demonstrates a new solution of the solar energy conversion, hydrogen production, storage, and utilization, achieving the new energy conversion and storage from solar energy to chemical energy, and further to electrical energy.Download high-res image (250KB)Download full-size image
Co-reporter:Chaoyu Wu, Guoran Li, Xueqin Cao, Bao Lei, Xueping Gao
Green Energy & Environment 2017 Volume 2, Issue 3(Volume 2, Issue 3) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.gee.2017.06.002
Carbon nitride (CNx) films supported on fluorine-doped tin oxide (FTO) glass are prepared by radio frequency magnetron sputtering, in which the film thicknesses are 90–100 nm, and the element components in the CNx films are in the range of x = 0.15–0.25. The as-prepared CNx is for the first time used as counter electrode for dye-sensitized solar cells (DSSCs), and show a preparation-temperature dependent electrochemical performance. X-ray photoelectron spectroscopy (XPS) demonstrates that there is a higher proportion of sp2 CC and sp3 CN hybridized bonds in CNx-500 (the sample treated at 500 °C) than in CNx-RT (the sample without a heat treatment). It is proposed that the sp2 CC and sp3 C–N hybridized bonds in the CNx films are helpful for improving the electrocatalytic activities in DSSCs. Meanwhile, Raman spectra also prove that CNx-500 has a relatively high graphitization level that means an increasing electrical conductivity. This further explains why the sample after the heat treatment has a higher electrochemical performance in DSSCs. In addition, the as-prepared CNx counter electrodes have a good light transmittance in the visible light region. The results are meaningful for developing low-cost metal-free transparent counter electrodes for DSSCs.Download high-res image (438KB)Download full-size imageMagnetron sputtered transparent carbon nitride is used as counter electrode in DSSCs, and the electrochemical performance and light transmittance is controllable by preparation temperature.
Co-reporter:Ze Zhang;Ling-Long Kong;Sheng Liu;Guo-Ran Li
Advanced Energy Materials 2017 Volume 7(Issue 11) pp:
Publication Date(Web):2017/06/01
DOI:10.1002/aenm.201602543
Carbon materials have attracted extensive attention as the host materials of sulfur for lithium–sulfur battery, especially those with 3D architectural structure. Here, a novel 3D graphene nanosheet–carbon nanotube (GN–CNT) matrix is obtained through a simple one-pot pyrolysis process. The length and density of CNTs can be readily tuned by altering the additive amount of carbon source (urea). Specifically, CNTs are in situ introduced onto the surface of the graphene nanosheets (GN) and show a stable covalent interaction with GN. Besides, in the GN–CNT matrix, cobalt nanoparticles with different diameters exist as being wrapped in the top of CNTs or scattering on the GN surface, and abundant heteroatoms (N, O) are detected, both of which can help in immobilizing sulfur species. Such a rationally designed 3D GN–CNT matrix makes much more sense in enhancing the electrochemical performance of the sulfur cathode for rapid charge transfer and favorable electrolyte infiltration. Moreover, the presence of dispersed cobalt nanoparticles is beneficial for trapping lithium polysulfides by strong chemical interaction, and facilitating the mutual transformation between the high-order polysulfides and low-order ones. As a result, the S/GN–CNT composite presents a high sulfur utilization and large capacity on the basis of the S/GN–CNT composite as active material.
Co-reporter:Peiyu Hou, Guoran Li and Xueping Gao
Journal of Materials Chemistry A 2016 vol. 4(Issue 20) pp:7689-7699
Publication Date(Web):11 Apr 2016
DOI:10.1039/C6TA01878E
Li-rich layered oxides with large capacity are considered as one of the most promising cathode materials for the next generation lithium-ion batteries (LIBs). However, Li-rich layered oxides usually deliver unsatisfactory volumetric energy density, poor cycle life and inferior thermal stability. Here, a concentration-gradient doping strategy is introduced for the first time to meet the above challenges. Surprisingly, the atomic distribution in micron-sized and spherical Li-rich layered oxides is tailored after concentration-gradient PO43− polyanion doping, in which Ni and Co atoms decrease continually and Mn atoms increase gradually from the center to the surface in a single particle. As expected, the concentration-gradient PO43− doped oxides exhibit a high initial volumetric energy density of 2027 W h L−1, long cycle life with a capacity retention of 88.2% within 400 cycles, and enhanced thermal stability. These improved performances are believed to be attributed to the formation of the stable Mn-rich and PO43−-rich shell layer, which is beneficial to mitigate the interreaction between Ni4+/Co4+ and the electrolyte in the highly delithiated state and suppress the aggregation of primary grains during cycles. These results demonstrate the feasibility of manipulating atomic distribution by the innovative concentration-gradient doping means, which also provides new insights into desired cathode for LIBs.
Co-reporter:Qi-Qi Qiao, Guo-Ran Li, Yong-Long Wang and Xue-Ping Gao
Journal of Materials Chemistry A 2016 vol. 4(Issue 12) pp:4440-4447
Publication Date(Web):25 Feb 2016
DOI:10.1039/C6TA00882H
Li-rich layered oxides with a large discharge capacity have attracted considerable attention as cathodes for high energy lithium-ion batteries. To further enhance the discharge capacity and thermal stability of these Li-rich layered oxides, Mn-based metal–organic frameworks (MOFs) with high surface areas, large pore sizes, and stable architectures are employed as the active coating material. Herein, Mn-based MOFs can partially absorb or store oxygen gas originating from the oxidation of oxygen anions from the host lattice of Li-rich layered oxides in the initial charging stage to above 4.5 V (vs. Li/Li+). Moreover, the structure of the Li-rich layered oxide could be strengthened by the interconnection frameworks between the metal cations and organic ligands. As expected, the Li-rich layered Li(Li0.17Ni0.20Co0.05Mn0.58)O2 oxide modified with a MOF exhibits a large discharge capacity (323.8 mA h g−1 at 0.1C rate), high initial coulombic efficiency (91.1%), and good thermal stability without harming the cycle stability and high-rate capability. Surface modification with MOFs offers a new insight for further enhancing the discharge capacity of Li-rich layered oxides as cathodes for advanced lithium-ion batteries.
Co-reporter:Sheng Liu, Guo-Ran Li, and Xue-Ping Gao
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 12) pp:7783
Publication Date(Web):March 16, 2016
DOI:10.1021/acsami.5b12231
Lithium–sulfur (Li–S) battery is regarded as one of the most promising candidates beyond conventional lithium ion batteries. However, the instability of the metallic lithium anode during lithium electrochemical dissolution/deposition is still a major barrier for the practical application of Li–S battery. In this work, lanthanum nitrate, as electrolyte additive, is introduced into Li–S battery to stabilize the surface of lithium anode. By introducing lanthanum nitrate into electrolyte, a composite passivation film of lanthanum/lithium sulfides can be formed on metallic lithium anode, which is beneficial to decrease the reducibility of metallic lithium and slow down the electrochemical dissolution/deposition reaction on lithium anode for stabilizing the surface morphology of metallic Li anode in lithium–sulfur battery. Meanwhile, the cycle stability of the fabricated Li–S cell is improved by introducing lanthanum nitrate into electrolyte. Apparently, lanthanum nitrate is an effective additive for the protection of lithium anode and the cycling stability of Li–S battery.Keywords: electrolyte additive; lanthanum nitrate; lithium anode; lithium−sulfur battery; surface morphology
Co-reporter:Ling-Long Kong, Ze Zhang, Ye-Zheng Zhang, Sheng Liu, Guo-Ran Li, and Xue-Ping Gao
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 46) pp:31684
Publication Date(Web):November 2, 2016
DOI:10.1021/acsami.6b11188
The lithium–sulfur (Li–S) battery is expected to be the high-energy battery system for the next generation. Nevertheless, the degradation of lithium anode in Li–S battery is the crucial obstacle for practical application. In this work, a porous carbon paper obtained from corn stalks via simple treating procedures is used as interlayer to stabilize the surface morphology of Li anode in the environment of Li–S battery. A smooth surface morphology of Li is obtained during cycling by introducing the porous carbon paper into Li–S battery. Meanwhile, the electrochemical performance of sulfur cathode is partially enhanced by alleviating the loss of soluble intermediates (polysulfides) into the electrolyte, as well as the side reaction of polysulfides with metallic lithium. The Li–S battery assembled with the interlayer exhibits a large capacity and excellent capacity retention. Therefore, the porous carbon paper as interlayer plays a bifunctional role in stabilizing the Li anode and enhancing the electrochemical performance of the sulfur cathode for constructing a stable Li–S battery.Keywords: interlayer; lithium anode; lithium−sulfur battery; porous carbon paper; surface morphology
Co-reporter:Qi-Qi Qiao, Lei Qin, Guo-Ran Li, Yong-Long Wang and Xue-Ping Gao
Journal of Materials Chemistry A 2015 vol. 3(Issue 34) pp:17627-17634
Publication Date(Web):21 Jul 2015
DOI:10.1039/C5TA03415A
Li-rich layered oxides have been intensively investigated as cathodes for high energy lithium-ion batteries. However, oxygen loss from the lattice during the initial charge and gradual structural transformation during cycling can lead to capacity degradation and potential decay of the cathode materials. In this work, Sn4+ is used to partially substitute Mn4+ to prepare a series of Li(Li0.17Ni0.25Mn0.58−xSnx)O2 (x = 0, 0.01, 0.03, and 0.05) samples through a spray-drying method. Structural characterization reveals that the Sn4+ substituted samples with a suitable amount show low cation mixing, indicating an enhanced ordered layer structure. Moreover, the metal–oxygen (M–O) covalency is gradually decreased with increasing Sn4+ amount. It is shown from the initial charge–discharge curves that Sn4+ substituted samples present a shorter charging potential plateau at 4.5 V (vs. Li/Li+), implying that oxidation of the O2− ion to O2 is suppressed by Sn4+ substitution and leads to a minor structural change. Among the Sn4+ substituted samples, the Li(Li0.17Ni0.25Mn0.55Sn0.03)O2 sample exhibits a higher capacity retention of 86% after 400 cycles at 0.1C rate and 92% after 200 cycles at 1C rate, showing excellent cycle stability and high-rate capability as compared with the as-prepared sample. The electrochemical performance improvement can be attributed to the influences of Sn such as enlarging the Li ion diffusion channel due to the large ionic radius of Sn4+ substitution with respect to Mn4+, a higher bonding energy of Sn–O than Mn–O, and weakening the M–O covalency. All the influences are favorable for stabilization of the host lattice in Li-rich layered oxides.
Co-reporter:Hang-Kun Jing, Ling-Long Kong, Sheng Liu, Guo-Ran Li and Xue-Ping Gao
Journal of Materials Chemistry A 2015 vol. 3(Issue 23) pp:12213-12219
Publication Date(Web):06 May 2015
DOI:10.1039/C5TA01490E
The performance of the metallic lithium anode is one of the major factors that affect the cycle stability of a lithium–sulfur battery. The protection of the lithium anode is extremely essential, especially for lithium–sulfur full-cells. Here, a porous Al2O3 layer is fabricated on the surface of a metallic lithium anode by using a spin-coating method as protective layer for a lithium–sulfur battery. The porous Al2O3 protective layer acts as a stable interlayer and suppresses the side reactions between soluble lithium polysulfides and lithium anode by direct contact during the charge–discharge process. In addition, the inhomogeneous dissolution–deposition reaction, and the formation of serious cracks on the protected lithium anode are suppressed to a certain extent, which is beneficial to ensure the good and stable electrochemical activity of the lithium anode. Correspondingly, the sulfur cathode with the protected lithium anode exhibits improved electrochemical performance, accompanied simultaneously with relatively homogeneous lithium deposition on the anode surface due to the even distribution of Li ion flux via the Al2O3 protective layer.
Co-reporter:Ze Zhang, Hang-Kun Jing, Sheng Liu, Guo-Ran Li and Xue-Ping Gao
Journal of Materials Chemistry A 2015 vol. 3(Issue 13) pp:6827-6834
Publication Date(Web):06 Feb 2015
DOI:10.1039/C4TA07183B
A hybrid carbon substrate as a sulfur immobilizer is obtained via simple processes to fabricate cathode materials for lithium–sulfur batteries. The microstructure and morphology of the sulfur/carbon composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is demonstrated that commercial carbon black and multi-walled carbon nanotubes (CNTs) in the hybrid substrate cooperate well with each other in an appropriate mass ratio. In particular, a large sulfur content of 81.7 wt% can be loaded into the hybrid carbon substrate forming the sulfur/carbon composite. When the mass ratio of carbon black and CNTs is 1:1, the composite delivers a high initial capacity of 837.3 and 685.9 mA h g−1(composite) at the current densities of 80 and 160 mA g−1(composite) when used as a cathode-active material. The discharge capacity remains at 554.4 mA h g−1(composite) at a current density of 160 mA g−1(composite) after 150 cycles, indicating a low capacity fading of about 0.12% per cycle. Besides, the composite offers a high Coulombic efficiency of about 100%. The significant improvements in the electrochemical performance are associated with the desirable combination of carbon black and CNTs in the hybrid carbon substrate. Therefore, this work proposes a low-cost and effortless approach to prepare sulfur/carbon composites with high performance as cathodes for lithium–sulfur batteries.
Co-reporter:S. Liu, G. L. Pan, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2015 vol. 3(Issue 3) pp:959-962
Publication Date(Web):27 Nov 2014
DOI:10.1039/C4TA04644G
Copper hexacyanoferrate (CuHCF) nanoparticles with Prussian blue structure are prepared via a simple co-precipitation method, which present the ability to insert Al ions reversibly in aqueous solution. CuHCF is verified to be a promising cathode material for aqueous Al-ion batteries.
Co-reporter:P. Y. Hou, L. Q. Zhang and X. P. Gao
Journal of Materials Chemistry A 2014 vol. 2(Issue 40) pp:17130-17138
Publication Date(Web):21 Aug 2014
DOI:10.1039/C4TA03158J
Ni-rich Li[Ni1−xMx]O2 (M = Co, Mn and Al) cathodes have shortcomings of poor thermal stability at the delithiated state and insufficient cycle performance, which are unsatisfied for commercial application in lithium ion batteries. Herein, a nickel-rich lithium transition-metal oxide with the full concentration-gradient structure is designed to overcome those problems. In the full concentration-gradient oxide, the nickel concentration decreases linearly, and the manganese concentration increases gradually, whereas the cobalt concentration remains constant from the center to the surface of each particle based on the energy disperse spectrum (EDS) analysis on the cross-section of a single particle. Firstly, the full concentration-gradient precursor is successfully prepared via a newly developed co-precipitation route. After lithiation at 800 °C, the as-prepared full concentration-gradient and normal oxides could be indexed to a typical layered structure with an Rm space group as detected by X-ray diffraction (XRD). Correspondingly, the full concentration-gradient layered oxide delivers more excellent cycle stability (especially at 55 °C), and thermal stability as compared with the normal layered oxide. It is also found that the Ni dissolution in the electrolyte is more serious, resulting in inferior cycle life for the normal layered oxide. Whereas, the outer layer of the full concentration-gradient oxide is much more stable, contributing to such excellent cycle and thermal stability.
Co-reporter:Ming Zhao, Yu Fu, Ning Xu, Guoran Li, Mengtao Wu and Xueping Gao
Journal of Materials Chemistry A 2014 vol. 2(Issue 36) pp:15070-15077
Publication Date(Web):18 Jul 2014
DOI:10.1039/C4TA03311F
A carbon matrix, for restricting growth of LiMnPO4 crystallites, is built on the small Li3PO4 crystallites precipitated from aqueous solutions, by the pyrolysis of sucrose. LiMnPO4 is prepared using the carbon coated Li3PO4 as one of the reactants (the other reactant is MnSO4) and the nuclei by a solvothermal method. Smaller-crystallite-size (8–12 nm) LiMnPO4 is successfully obtained on the carbon matrix by a crystallite size control method. The as-prepared LiMnPO4/C sample presents the desired electrochemical performance, including higher discharge potential plateau, larger discharge capacity, excellent high-rate capability, and good cycle stability. It is also confirmed that the smaller LiMnPO4 crystallites on the carbon matrix are beneficial for shortening the lithium ion diffusion path and increasing the electrical conductivity of the LiMnPO4/C sample, contributing to an improvement in electrochemical performance. The methodology described in this work could be helpful in the development of LiMnPO4/C cathode materials for lithium ion batteries with high energy density.
Co-reporter:H. Z. Zhang, Q. Q. Qiao, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2014 vol. 2(Issue 20) pp:7454-7460
Publication Date(Web):06 Mar 2014
DOI:10.1039/C4TA00699B
Advanced Li-ion batteries, with Li-rich layered oxides as cathode materials and Si-based composites as anode materials, are considered as high energy battery systems for the next generation of smart communications and electric vehicles (EVs). At the current stage, it is significant to develop Li-rich layered oxides with stable output energy density. However, the gradual capacity degradation and potential decay during cycling lead to the continual decrease in the energy density of Li-rich layered oxides. Therefore, a new strategy should be introduced to block the migration of transition metal cations and maintain the parent layered structure during cycling, in order to stabilize the energy density of oxides. In this work, large tetrahedral PO43− polyanions with high electronegativity with respect to O2− anions are doped into oxides for minimizing the local structure change during cycling. When doping with PO43− polyanions, the parent layered structure is retained during long cycling, due to the strong bonding of PO43− polyanions to transition metal cations (Ni especially). Correspondingly, PO43− polyanion-doped oxides present excellent energy density retention during long cycling, integrated with the discharge capacity and midpoint potential. These results suggest that polyanion-doping can meet the performance requirement of stabilizing the energy density of Li-rich layered oxides for advanced lithium ion batteries.
Co-reporter:Y. Z. Zhang, S. Liu, G. C. Li, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2014 vol. 2(Issue 13) pp:4652-4659
Publication Date(Web):07 Jan 2014
DOI:10.1039/C3TA14914E
Sulfur/polyacrylonitrile(PAN)/carbon multi-composites with different sulfur content are prepared based on dual-mode of fixing sulfur on the matrix of the partially carbonized PAN (cPAN) and activated-conductive carbon black (A-CCB). The electrochemical performance of the as-prepared multi-composites as active materials are tested in the electrolyte with a high concentration lithium salt (LiTFSI) in different mixed solvents of 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME), and 1,3-dioxolane (DOL)/tetraethylene glycol dimethyl ether (TEGDME), respectively. It is demonstrated that the high concentration lithium salt (LiTFSI) and high viscous solvent have a great impact on the cycle stability of the multi-composite by suppressing polysulfide dissolution at the slight expense of the discharge potential plateaus (width and height). The as-prepared multi-composites present the excellent cycle performance in the electrolyte with 5 M LiTFSI in DOL/DME. Meanwhile, when the lower viscous DME solvent is replaced by the higher viscous TEGDME solvent in the electrolyte with 3 M LiTFSI, the optimized cycle stability is still obtained for the as-prepared multi-composites based on the evaluation of the discharge capacity and cycle stability. Therefore, the electrochemical performance of the as-prepared multi-composites is obviously influenced by the common ion effect and viscosity of the electrolyte, which are induced from both the lithium salt and solvent.
Co-reporter:J. T. Zhang, S. Liu, G. L. Pan, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2014 vol. 2(Issue 5) pp:1524-1529
Publication Date(Web):19 Nov 2013
DOI:10.1039/C3TA13578K
Supercapacitors are the most promising energy storage devices by virtue of high power density, long cycle life, short charging time and environmental benignity. In order to enhance the energy density, rate capability and cycle stability for supercapacitors, a α-Ni(OH)2/graphite nanosheet composite is prepared via a homogeneous precipitation method. The morphology and microstructure of the as-prepared composite are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. It is demonstrated that after introducing the graphene oxide nanosheets into α-Ni(OH)2, a 3D hierarchical porous structure of fine α-Ni(OH)2 nanocrystals as building blocks is formed directly on the matrix of graphite nanosheets in the presence of urea as a mild reducing agent. The electrochemical performance of the as-prepared α-Ni(OH)2 and α-Ni(OH)2/graphite nanosheet composites as electro-active materials for supercapacitors is investigated by a galvanostatic charge–discharge method. As expected, the as-prepared α-Ni(OH)2/graphite nanosheet composite exhibits large specific capacitance, good rate capability and long cycle stability as compared to the pure α-Ni(OH)2. Apparently, the unique structure of fine α-Ni(OH)2 nanocrystals fabricated on the matrix of graphite nanosheets is responsible for the improvement of the reaction kinetics and subsequent electrochemical performance of the composite.
Co-reporter:J. J. Hu, G. K. Long, S. Liu, G. R. Li and X. P. Gao
Chemical Communications 2014 vol. 50(Issue 93) pp:14647-14650
Publication Date(Web):03 Oct 2014
DOI:10.1039/C4CC06666A
LiFSI and LiTFSI are combined to form a binary-salt electrolyte with higher ionic conductivity and lower viscosity for a Li–S battery. A high capacity and stable cycle performance of the sulfur-based composite with high sulfur content are realized in the electrolyte, accompanied simultaneously by the homogeneous lithium deposition on the anode.
Co-reporter:J. Song, G.R. Li, C.Y. Wu, X.P. Gao
Journal of Power Sources 2014 Volume 266() pp:464-470
Publication Date(Web):15 November 2014
DOI:10.1016/j.jpowsour.2014.05.062
•Group VIIIB metal sulfides thin films are prepared by a solution-process strategy.•The sulfide electrodes achieve optical transparency and high electrochemical activity.•The DSSC using nickel sulfide shows a higher efficiency than using Pt electrode.Dye-sensitized solar cells (DSSCs) have obtained exciting progress in improving energy conversion efficiency and cutting material cost in recent years. It is found that many kinds of inorganic compounds have promising potential to replace platinum as counter electrode materials for DSSCs. Actually, to a thin film electrode, preparation of the thin film is the same important as choice of active materials, because quality of the films has a direct effect on electrochemical and optical performance of the final counter electrodes. In this paper, a general strategy is developed to prepare transparent and high-efficient metal sulfide counter electrodes. In the route, the Group VIIIB metal sulfides are formed as compact, homogenous and stable films on fluorine-doped tin oxide conductive glass from a precursor organic solution by spin coating, and the film thickness can be readily converted to reach the balance between optical transparency and electrochemical activity. Among the Group VIIIB metal sulfides, the nickel sulfide film with the thickness of 100 nm shows the high transparency and energy conversion efficiency of 7.37%, higher than that of the DSSC using platinum electrode. The results provide a new and facile alternative to prepare high-efficient and transparent sulfide counter electrodes for DSSCs.
Co-reporter:C.W. Xiao, Y. Ding, J.T. Zhang, X.Q. Su, G.R. Li, X.P. Gao, P.W. Shen
Journal of Power Sources 2014 Volume 248() pp:323-329
Publication Date(Web):15 February 2014
DOI:10.1016/j.jpowsour.2013.09.131
•The substitution of lithium ions by sodium ions leads to the phase transformation.•The Li2Na2Ti5O12 presents the low and sloped potential plateau.•The Li2Na2Ti5O12 delivers the good high-rate capability and cycle stability.In this work, the unique effect of the substitution of lithium ions by sodium ions in Li4Ti5O12 on the structure, crystalline size and electrochemical performance is investigated in details. The Li4−xNaxTi5O12 materials are by high temperature calcination of titania, anhydrous lithium carbonate and anhydrous sodium carbonate. It is shown from the structure analysis that the phase structure transformation is found with gradually increasing the molar ratio of sodium ions to lithium ions in the as-prepared Li4−xNaxTi5O12 samples, accompanied with the evident growth of the crystallites. Because of the phase structure transformation from a cubic structure to an orthorhombic structure whose open relatively tunnel structure along the b-axis makes for the lithium ion insertion/extraction, the Li2Na2Ti5O12 sample presents the low and sloped potential plateau as expected, distinguished from the high and flat potential plateau of Li4Ti5O12. Meanwhile, the Li2Na2Ti5O12 sample delivers the good high-rate capability and cycle stability during cycling. The results clarify the positive effect of the suitable substitution of lithium ions by sodium ions in Li4Ti5O12 anode material with the low operation potential for insuring the high working voltage of lithium ion batteries.
Co-reporter:Q. Q. Qiao, H. Z. Zhang, G. R. Li, S. H. Ye, C. W. Wang and X. P. Gao
Journal of Materials Chemistry A 2013 vol. 1(Issue 17) pp:5262-5268
Publication Date(Web):15 Mar 2013
DOI:10.1039/C3TA00028A
Enhancement of the discharge capacity, high-rate capability, and cycle stability of the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide with a large specific capacity is highly significant for high energy lithium-ion batteries. In this work, the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide is prepared by a spray-drying method. The surface modification with the Li–Mn–PO4 is introduced onto Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide for the first time. It is demonstrated that the surface of Li(Li0.17Ni0.25Mn0.58)O2 grains is coated with the thin amorphous Li–Mn–PO4 layer (5 wt%). With increasing calcination temperature after the surface coating, a strong interaction can be induced on the interface between the amorphous Li–Mn–PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O2 grains. As anticipated, the discharge capacity and high-rate capability are obviously improved for the Li–Mn–PO4-coated sample after calcination at 400 °C, while excellent cycle stability is obtained for the Li–Mn–PO4-coated sample after calcination at 500 °C as compared with the as-prepared Li(Li0.17Ni0.25Mn0.58)O2 oxide during cycling. Apparently, the interface interaction between the amorphous Li–Mn–PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O2 grains is responsible for the improvement of the reaction kinetics and the electrochemical cycle stability of Li–Mn–PO4-coated samples.
Co-reporter:N. F. Yan, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2013 vol. 1(Issue 24) pp:7012-7015
Publication Date(Web):01 May 2013
DOI:10.1039/C3TA11360D
A solar rechargeable redox flow battery is fabricated with Li2WO4 as anode in aqueous electrolyte, LiI as cathode in organic electrolyte, and LISICON film as membrane to separate liquid anode/cathode-active species. The as-fabricated battery presents feasible solar rechargeable capability.
Co-reporter:Y. Ding, G.R. Li, C.W. Xiao, X.P. Gao
Electrochimica Acta 2013 Volume 102() pp:282-289
Publication Date(Web):15 July 2013
DOI:10.1016/j.electacta.2013.04.002
Li4Ti5O12/carbon composites have shown promising high rate capability as anode materials for lithium ion batteries. In this paper, unique effects of graphene in Li4Ti5O12/carbon composites on electrochemical performances are focused by means of comparing Li4Ti5O12/graphene with Li4Ti5O12/conductive carbon black (CCB) and Li4Ti5O12. The investigated anode materials are synthesized by a facile hydrothermal method. The amount of graphene or CCB in the Li4Ti5O12/carbon composites is about 3 wt% measured by thermogravimetric (TG) analysis. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that Li4Ti5O12/graphene consists of small sized Li4Ti5O12 nanocrystals supported on graphene nanosheets, while Li4Ti5O12/CCB comprises Li4Ti5O12 nanocrystal aggregates coated nearly by graphited carbon. The electrochemical performances of these samples as anode materials for lithium ion batteries are investigated by galvanostatic charge–discharge method. Li4Ti5O12/graphene provides a superior rate capability. At the high current density of 1600 mA g−1, the reversible capacity after 200 cycles is still more than 120 mAh g−1, which is about 40% higher than that of Li4Ti5O12/CCB. Cyclic voltammetry (CV) demonstrates that stronger pseudocapacitive effect occurs on Li4Ti5O12/graphene than on Li4Ti5O12/CCB. This derived from the structure features that graphene-supported small Li4Ti5O12 nanocrystals provide more surface active sites for the lithium ion insertion/extraction. The strong pseudocapacitive effect is responsible for the improvements of capacity and high-rate capability. Further, electrochemical impedance spectra (EIS) show that Li4Ti5O12/graphene electrode have lower charge transfer resistance and smaller diffusion impedance, indicating the obvious advantages in electrode kinetics over Li4Ti5O12 and Li4Ti5O12/CCB. The results clarify the positive effects of graphene in Li4Ti5O12/carbon composites as anode materials for lithium ion batteries.
Co-reporter:J. P. Huang, D. D. Yuan, H. Z. Zhang, Y. L. Cao, G. R. Li, H. X. Yang and X. P. Gao
RSC Advances 2013 vol. 3(Issue 31) pp:12593-12597
Publication Date(Web):31 May 2013
DOI:10.1039/C3RA42413H
Exploring new anode materials is important for developing sodium ion batteries. In this work, TiO2(B) nanotubes are prepared by hydrothermal reaction in concentrated NaOH solution and subsequent calcination at 300 °C in air, and investigated for the first time as anodes for sodium ion batteries. It is demonstrated that TiO2(B) nanotubes are several hundred nanometers in length with an outer diameter of about 10–15 nm. Moreover, the interference fringe spacings of the nanotubes are derived from the TEM image, being about 0.56 and 0.34 nm, which are consistent with the interplanar distances of the (001) and (110) planes in the TiO2(B) phase, respectively. As anticipated, the interlayer spacing of the (001) plane in the TiO2(B) nanotubes is large enough to accommodate sodium ions. Meanwhile, the tubular morphology can ensure the good high rate capability and cycle stability. Therefore, TiO2(B) nanotubes present feasible electrochemical sodium storage, offering possibilities to develop new anode materials for sodium ion batteries.
Co-reporter:Ping Liu;Yu-liang Cao;Guo-Ran Li;Xin-Ping Ai; Han-Xi Yang
ChemSusChem 2013 Volume 6( Issue 5) pp:802-806
Publication Date(Web):
DOI:10.1002/cssc.201200962
Co-reporter:S. Liu, J. J. Hu, N. F. Yan, G. L. Pan, G. R. Li and X. P. Gao
Energy & Environmental Science 2012 vol. 5(Issue 12) pp:9743-9746
Publication Date(Web):01 Oct 2012
DOI:10.1039/C2EE22987K
The electrochemical aluminum storage of anatase TiO2 nanotube arrays in AlCl3 aqueous solution is investigated. It is firstly demonstrated that aluminum ions can be reversibly inserted/extracted into/from anatase TiO2 nanotube arrays in AlCl3 aqueous solution due to the small radius steric effect of aluminum ions, indicating a potential application in aluminum ion batteries.
Co-reporter:Guo-Chun Li;Guo-Ran Li;Shi-Hai Ye
Advanced Energy Materials 2012 Volume 2( Issue 10) pp:1238-1245
Publication Date(Web):
DOI:10.1002/aenm.201200017
Abstract
Polyaniline-coated sulfur/conductive-carbon-black (PANI@S/C) composites with different contents of sulfur are prepared via two facile processes including ball-milling and thermal treatment of the conductive carbon black and sublimed sulfur, followed by an in situ chemical oxidative polymerization of the aniline monomer in the presence of the S/C composite and ammonium persulfate. The microstructure and electrochemical performance of the as-prepared composites are investigated systematically. It is demonstrated that the polyaniline, with a thickness of ≈5–10 nm, is coated uniformly onto the surface of the S/C composite forming a core/shell structure. The PANI@S/C composite with 43.7 wt% sulfur presents the optimum electrochemical performance, including a large reversible capacity, a good coulombic efficiency, and a high active-sulfur utilization. The formation of the unique core/shell structure in the PANI@S/C composites is responsible for the improvement of the electrochemical performance. In particular, the high-rate charge/discharge capability of the PANI@S/C composites is excellent due to a synergistic effect on the high electrical conductivity from both the conductive carbon black in the matrix and the PANI on the surface. Even at an ultrahigh rate (10C), a maximum discharge capacity of 635.5 mA h per g of sulfur is still retained for the PANI@S/C composite after activation, and the discharge capacity retention is over 60% after 200 cycles.
Co-reporter:J. Song, G. R. Li, F. Y. Xiong and X. P. Gao
Journal of Materials Chemistry A 2012 vol. 22(Issue 38) pp:20580-20585
Publication Date(Web):14 Aug 2012
DOI:10.1039/C2JM34878K
As a counter electrode for dye-sensitized solar cells (DSSCs), MoN presents a high intrinsic electrocatalytic activity for the reduction of triiodide ions. However, the photovoltaic performance of DSSCs with a MoN counter electrode is hindered by the large diffusion impedance of the MoN electrode. In response to this problem, a MoN–carbon nanotube (CNT) composite is prepared by nitridation of the precursor MoO2–CNTs, fabricated via a hydrothermal reaction of ammonium molybdate and carboxyl-functionalized CNTs. In the composite, MoN nanoparticles are well and stably dispersed on the surface of the CNTs, with a particle size of several tens of nanometers. Employing the composite as a counter electrode, the DSSC shows an energy conversion efficiency of 6.74%, which is much higher than that (5.57%) of the DSSC using pure MoN nanoparticles. The improvement is mainly attributed to a synergistic effect between the MoN nanoparticles and CNTs on ion diffusion and electrocatalysis. Electrochemical impedance spectra (EIS) indicate that the MoN–CNTs electrode has a lower ion diffusion impedance. It is believed that the smaller size of the MoN nanoparticles and the abundant porous structure in the MoN–CNTs composite are able to shorten the ion diffusion path and improve ion diffusion flux.
Co-reporter:H. Z. Zhang, Q. Q. Qiao, G. R. Li, S. H. Ye and X. P. Gao
Journal of Materials Chemistry A 2012 vol. 22(Issue 26) pp:13104-13109
Publication Date(Web):02 May 2012
DOI:10.1039/C2JM30989K
A Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide is prepared by a combination of co-precipitation and solid-state reaction. The surface nitridation is introduced into a Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 for the first time via heating at 400 °C in the ammonia atmosphere. The microstructure and morphology of the two samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that the nitrogen exists with a trace amount in the surface layer of the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide after the nitridation treatment. Electrochemical performances of the electrodes are measured by galvanostatic charge–discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). As expected, the discharge capacity, high-rate capability and cycle stability of the nitrided sample are improved dramatically as compared with the as-prepared sample, which is further confirmed by the high electrocatalytic activity and accelerated lithium diffusion process. Apparently, the existence of nitrogen in the surface layer is responsible for the improvement of the reaction kinetics and electrochemical performance of the nitrided sample.
Co-reporter:P. Liu, H.X. Yang, X.P. Ai, G.R. Li, X.P. Gao
Electrochemistry Communications 2012 Volume 16(Issue 1) pp:69-72
Publication Date(Web):March 2012
DOI:10.1016/j.elecom.2011.11.035
A solar rechargeable battery is constructed by use of a hybrid TiO2/poly(3,4-ethylenedioxythiophene, PEDOT) photo-anode and a ClO4− doped polypyrrole counter electrode. Here, the dye-sensitized TiO2/PEDOT photo-anode serves for positive charge storage and a p-doped PPy counter electrode acts for electron storage in LiClO4 electrolyte. The proposed device demonstrates a rapid photo-charge at light illumination and a stable electrochemical discharge in the dark, realizing an in situ solar-to-electric conversion and storage.Highlights► A solar rechargeable battery (SRB) is developed based on hole and electron storage. ► The SRB demonstrates an effective solar-to-electric conversion and storage. ► The photo-charge/discharge reactions proceed via reversible doping/de-doping of ClO4−.
Co-reporter:Xiangpeng Fang, Chunxiu Hua, Xianwei Guo, Yongsheng Hu, Zhaoxiang Wang, Xueping Gao, Feng Wu, Jiazhao Wang, Liquan Chen
Electrochimica Acta 2012 Volume 81() pp:155-160
Publication Date(Web):30 October 2012
DOI:10.1016/j.electacta.2012.07.020
Transition metal sulfides are regarded as another type of high-performance anode materials following the transition metal oxides for lithium ion batteries. However, the lithium storage mechanisms of these sulfides are complicated. This work is intended to evaluate the electrochemical performances of molybdenum disulfide (MoS2) and find out its lithium storage mechanism at different lithium insertion stages. It is found that although the MoS2 shows excellent cycling stability in different voltage ranges, its structural transition is irreversible in the initial cycling. In contrast to the traditional beliefs, metallic Mo is found inert and Li2S/S is the redox couple in a deeply discharged MoS2/Li cell (0.01 V vs. Li/Li+). The metallic Mo nanoparticles are believed to be responsible for the enhanced cycling stability of the cell and act as the electronically conducting phase in the capacitive energy storage on the interfaces or grain boundaries of Mo/Li2Sx nanocomposite. In addition, the Mo/Li2S nanocomposite can be used as a cathode material for lithium–sulfur batteries.
Co-reporter:G.R. Li, X. Feng, Y. Ding, S.H. Ye, X.P. Gao
Electrochimica Acta 2012 Volume 78() pp:308-315
Publication Date(Web):1 September 2012
DOI:10.1016/j.electacta.2012.05.142
Li-rich layered oxide is prepared and coated with an AlF3 layer by a chemical deposition method. The as-prepared and AlF3-coated Li-rich materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-prepared Li-rich oxide has a typical layered structure with the chemical formula of Li(Li0.17Ni0.25Mn0.58)O2, and the AlF3 layer with a thickness of about 5–7 nm is coated on the surface of the Li(Li0.17Ni0.25Mn0.58)O2 grains. Galvanostatic charge–discharge tests at various rates show that the AlF3-coated Li(Li0.17Ni0.25Mn0.58)O2 has an obviously enhanced electrochemical performance compared with the as-prepared sample. At 0.2 C rate, the AlF3-coated sample provides a large capacity of more than 250 mAh g−1. The coulombic efficiency in the initial cycle is improved to 89.5% from 76.4%. At 5 C rate, the reversible capacity of the AlF3-coated sample is stable at above 104 mAh g−1 after 200 cycles, much higher than that of the as-prepared sample. According to the analysis from electrochemical impedance spectra (EIS), the improvements of the electrochemical performance are mainly attributed to the pre-activation of the Li-rich layered oxide induced by the AlF3 coating and the maintenance of more active sites for the lithium ion intercalation/extraction in the AlF3-coated sample.Highlights► The AlF3 layer with a thickness of 5–7 nm is coated on the surface of the Li-rich oxide. ► The AlF3-coated Li(Li0.17Ni0.25Mn0.58)O2 delivers the excellent high-rate capability. ► The AlF3 coating can pre-activate the Li-rich layered oxide.
Co-reporter:Y. Y. Dou, G. R. Li, J. Song and X. P. Gao
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 4) pp:1339-1342
Publication Date(Web):29 Nov 2011
DOI:10.1039/C2CP23775J
Nickel phosphide-embedded graphene, prepared by the hydrothermal reaction of red phosphorus, nickel chloride, and graphene oxide in a mixture of ethylene glycol–water, is investigated as the counter electrode of DSSCs. It is demonstrated that the DSSC with the nickel phosphide-embedded graphene as the new counter electrode presents an excellent performance competing with that of the Pt electrode.
Co-reporter:G. R. Li, J. Song, G. L. Pan and X. P. Gao
Energy & Environmental Science 2011 vol. 4(Issue 5) pp:1680-1683
Publication Date(Web):31 Mar 2011
DOI:10.1039/C1EE01105G
Pt-like electrocatalytic activity of MoN, WN, and Fe2N for dye-sensitized solar cells (DSSCs) is demonstrated in this work. Among the transition metal nitrides, MoN has superior electrocatalytic activity and a higher photovoltaic performance. This work presents a new approach for developing low-cost and highly-efficient counter electrodes for DSSCs.
Co-reporter:X. Li, C. Lai, C.W. Xiao, X.P. Gao
Electrochimica Acta 2011 Volume 56(Issue 25) pp:9152-9158
Publication Date(Web):30 October 2011
DOI:10.1016/j.electacta.2011.07.101
The dual-phase Li4Ti5O12–TiO2 nanocomposite is successfully synthesized by a hydrothermal route with adding thiourea. The electrochemical performance of the dual-phase nanocomposite as anode for lithium-ion batteries is investigated by the galvanostatic method, cyclic voltammetry and electrochemical impedance spectra. It is demonstrated that the dual-phase Li4Ti5O12–TiO2 nanocomposite presents the improved electrochemical performance over individual single phase Li4Ti5O12 and anatase TiO2 samples. After 300 cycles at 1 C, the dual-phase Li4Ti5O12–TiO2 nanocomposite can still maintain the large discharge capacity of 116 mAh g−1. It indicates that the as-prepared nanocomposite can endure great changes of various discharge current densities to retain a good stability. The large discharge capacity of 132 mAh g−1 is also obtained at the large current density of 1600 mA g−1 upon cycling. In particular, as verified by the cyclic voltammetry, the pseudocapacitive effect is induced due to the presence of abundant phase interfaces in the dual-phase Li4Ti5O12–TiO2 nanocomposite, which is beneficial to the enhanced high rate capability and good cycle stability.Highlights► The dual-phase Li4Ti5O12–TiO2 nanocomposite with abundant phase interfaces is successfully synthesized by a hydrothermal route with adding thiourea. ► The dual-phase Li4Ti5O12–TiO2 nanocomposite presents the improved electrochemical performance over individual single phase Li4Ti5O12 and anatase TiO2 samples. ► The dual-phase nanocomposite can endure great changes of various discharge current densities to retain a good stability. ► The pseudocapacitive effect induced is beneficial to the enhanced high rate capability and good cycle stability of the dual-phase nanocomposite.
Co-reporter:B. Zhang, X. Qin, G. R. Li and X. P. Gao
Energy & Environmental Science 2010 vol. 3(Issue 10) pp:1531-1537
Publication Date(Web):16 Aug 2010
DOI:10.1039/C002639E
To enhance the long stability of sulfur cathode for a high energy lithium–sulfur battery system, a sulfur–carbon sphere composite was prepared by encapsulating sulfur into micropores of carbon spheres by thermal treatment of a mixture of sublimed sulfur and carbon spheres. The elemental sulfur exists as a highly dispersed state inside the micropores of carbon spheres with a large surface area and a narrow pore distribution, based on the analyses of the X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), thermogravimetry (TG) and local element line-scanning. It is demonstrated from galvanostatic discharge–charge process, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) that the sulfur–carbon sphere composite has a large reversible capacity and an excellent high rate discharge capability as cathode materials. In particular, the sulfur–carbon sphere composite with 42 wt% sulfur presents a long electrochemical stability up to 500 cycles, based on the constrained electrochemical reaction inside the narrow micropores of carbon spheres due to strong adsorption. Therefore, the electrochemical reaction constrained inside the micropores proposed here would be the dominant factor for the enhanced long stability of the sulfur cathode. The knowledge acquired in this study is important not only for the design of efficient new electrode materials, but also for understanding the effect of the micropores on the electrochemical cycle stability.
Co-reporter:S. Liu, G. L. Pan, N. F. Yan and X. P. Gao
Energy & Environmental Science 2010 vol. 3(Issue 11) pp:1732-1735
Publication Date(Web):29 Sep 2010
DOI:10.1039/C0EE00170H
A new aqueous TiO2/Ni(OH)2 rechargeable battery system with a high voltage, consisting of α-phase nickel hydroxides as the cathode and TiO2 nanotube arrays as the anode, is proposed for the first time. It is a feasible strategy to combine two different reaction mechanisms in an aqueous alkaline electrolyte: proton and lithium insertion/extraction reactions.
Co-reporter:J. Qu, G. R. Li and X. P. Gao
Energy & Environmental Science 2010 vol. 3(Issue 12) pp:2003-2009
Publication Date(Web):13 Oct 2010
DOI:10.1039/C003646C
To overcome kinetic limitations of nanoparticles and one-dimensional nanostructures, and enhance fast reaction kinetics of photoanode materials for dye-sensitized solar cells, one-dimensional hierarchical titanate was prepared by coating protonated titanate nanoparticles on one-dimensional protonated titanate nanorods. The one-dimensional hierarchical titania was obtained subsequently after calcination at different temperatures, and was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The photoelectrochemical and electrochemical performance of the one-dimensional hierarchical titania was then carried out by photocurrent–voltage curves, electrochemical impedance spectroscopy (EIS), intensity-modulated photovoltage spectroscopy (IMVS) and intensity-modulated photocurrent spectroscopy (IMPS). It is clear that titania nanoparticles grow uniformly on the surface of titania nanorods. The one-dimensional hierarchical titania obtained subsequently can not only provide a matrix similar to the hybrid structure matrix but also avoid forming a large amount of grain boundaries, since the hierarchical structure forms by growth of nanoparticles on nanorods. In particular, the titania with such hierarchical structures after calcination at 600 and 700 °C show optimized fast reaction kinetics: low charge-transfer resistance, fast electron transport and long electron lifetime. The knowledge acquired in this work is important for the design of efficient photoanode materials of dye-sensitized solar cells.
Co-reporter:C. Lai, Y.Y. Dou, X. Li, X.P. Gao
Journal of Power Sources 2010 Volume 195(Issue 11) pp:3676-3679
Publication Date(Web):1 June 2010
DOI:10.1016/j.jpowsour.2009.12.077
Hierarchical structured Li4Ti5O12, assembling from randomly oriented nanosheets with a thickness of about 10–16 nm, is fabricated by a facile hydrothermal route and following calcination. It is demonstrated that the as-prepared sample has good cycle stability and excellent high rate performance. In particular, the discharge capacity of 128 mAh g−1 can be obtained at the high current density of 2000 mA g−1, which is about 87% of that at the low current density of 200 mA g−1 upon cycling, indicating that the as-prepared sample can endure great changes of various discharge current densities to retain a good stability. In addition, the pseudocapacitive effect based on the hierarchical structure, also contributes to the high rate capability of Li4Ti5O12, which can be confirmed in cyclic voltammograms.
Co-reporter:C. Lai, G.R. Li, Y.Y. Dou, X.P. Gao
Electrochimica Acta 2010 Volume 55(Issue 15) pp:4567-4572
Publication Date(Web):1 June 2010
DOI:10.1016/j.electacta.2010.03.010
A functional composite as anode materials for lithium-ion batteries, which contains highly dispersed TiO2 nanocrystals in polyaniline matrix and well-defined mesopores, is fabricated by employing a novel one-step approach. The as-prepared mesoporous polyaniline/anatase TiO2 nanocomposite has a high specific surface area of 224 m2 g−1 and a predominant pore size of 3.6 nm. The electrochemical performance of the as-prepared composite as anode material is investigated by cyclic voltammograms and galvanostatic method. The results demonstrate that the polyaniline/anatase nanocomposite provides larger initial discharge capacity of 233 mAh g−1 and good cycle stability at the high current density of 2000 mA g−1. After 70th cycles, the discharge capacity is maintained at 140 mAh g−1. The excellent electrochemical performance of the polyaniline/TiO2 nanocomposite is mainly attributed to its special structure. Furthermore, it is accessible to extend the novel strategy to other polymer/TiO2 composites, and the mesoporous polypyrrole/anatase TiO2 is also successfully fabricated.
Co-reporter:Q.W. Jiang, G.R. Li, F. Wang, X.P. Gao
Electrochemistry Communications 2010 Volume 12(Issue 7) pp:924-927
Publication Date(Web):July 2010
DOI:10.1016/j.elecom.2010.04.022
Highly ordered mesoporous carbon arrays are prepared by a facile carbonization of the natural bamboo and oak wood in argon atmosphere. The as-prepared oak mesoporous carbon arrays have good electrocatalytic activity and high conductivity, based on their well connected framework, highly ordered microtexture, wider mesopores and larger surface area. Consequentially, the photovoltaic performance of the DSSC with the oak mesoporous carbon array film as counter electrode is excellent and comparable to that of the DSSC with FTO/Pt counter electrode. In addition, it is a simple method for a mass production of mesoporous carbon arrays with natural wood materials.
Co-reporter:Q. W. Jiang, G. R. Li, S. Liu and X. P. Gao
The Journal of Physical Chemistry C 2010 Volume 114(Issue 31) pp:13397-13401
Publication Date(Web):July 19, 2010
DOI:10.1021/jp1035184
Surface-nitrided nickel foil and particle films were prepared through the nitridation of metallic nickel foil and particle films in ammonia atmosphere. The microstructure of the obtained surface nitrided nickel foil and particle films was characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It is shown that only a thin nitrided layer can be formed on the surface of the metallic nickel after the nitridation, while the bulk phase still remains the stable metallic nickel structure. Surface-nitrided nickel film is directly investigated as a low cost counter electrode material for dye-sensitized solar cells. Clearly, the surface-nitrided nickel layer shows high electrocatalytic activity for reduction of triiodide, and the bulk metallic phase provides good electrical conductivity. Correspondingly, the assembly of these two important functions makes surface-nitrided nickel present an excellent photovoltaic performance of dye-sensitized solar cells (DSSCs), competing with the conventional Pt counter electrode. Therefore, the surface-nitrided Ni with a bifunctional structure as presented in this work is a potential low-cost alternative to the expensive noble metal Pt in future applications of dye-sensitized solar cells.
Co-reporter:Guo-ran Li Dr.;Feng Wang;Qi-wei Jiang Dr., ;Pan-wen Shen
Angewandte Chemie 2010 Volume 122( Issue 21) pp:3735-3738
Publication Date(Web):
DOI:10.1002/ange.201000659
Co-reporter:Guo-ran Li Dr.;Feng Wang;Qi-wei Jiang Dr., ;Pan-wen Shen
Angewandte Chemie International Edition 2010 Volume 49( Issue 21) pp:3653-3656
Publication Date(Web):
DOI:10.1002/anie.201000659
Co-reporter:Xue-Ping Gao, Su-Mei Yao, Tian-Ying Yan and Zhen Zhou
Energy & Environmental Science 2009 vol. 2(Issue 5) pp:502-505
Publication Date(Web):23 Mar 2009
DOI:10.1039/B901934K
It is demonstrated that β-Co(OH)2 has a high discharge capacity and good high-rate discharge ability as a negative electrode material. A new rechargeable battery system with higher energy density, consisting of α-phase nickel hydroxides as the positive electrode material and β-cobalt hydroxides as the negative electrode material, is proposed on the basis of multi-electron reactions.
Co-reporter:Q. W. Jiang, G. R. Li and X. P. Gao
Chemical Communications 2009 (Issue 44) pp:6720-6722
Publication Date(Web):25 Sep 2009
DOI:10.1039/B912776C
TiN nanotube arrays, prepared by the anodization of metallic Ti foil substrate and subsequent simple nitridation in an ammonia atmosphere, were investigated as low-cost counter electrodes in dye-sensitized solar cells for the first time. It is found that the highly ordered TiN nanotube arrays on the metallic Ti foil substrate show an excellent performance, comparable with typical Pt counter electrodes.
Co-reporter:Xue Bin Ke, Ren Fu Shao, Huai Yong Zhu, Yong Yuan, Dong Jiang Yang, Kyle R. Ratinac and Xue Ping Gao
Chemical Communications 2009 (Issue 10) pp:1264-1266
Publication Date(Web):15 Jan 2009
DOI:10.1039/B819292H
Ceramic membranes were fabricated by in situ synthesis of aluminananofibres in the pores of an alumina support as a separation layer, and exhibited a high permeation selectivity for bovine serum albumin relative to bovine hemoglobin (over 60 times) and can effectively retain DNA molecules at high fluxes.
Co-reporter:G. Wang, X.P. Gao, P.W. Shen
Journal of Power Sources 2009 Volume 192(Issue 2) pp:719-723
Publication Date(Web):15 July 2009
DOI:10.1016/j.jpowsour.2009.02.074
Cubic spinel Co2SnO4 nanocrystals are successfully synthesized via a simple hydrothermal reaction in alkaline solution. The effect of alkaline concentration, hydrothermal temperature, and hydrothermal time on the structure and morphology of the resultant products were investigated based on X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is demonstrated that pure Co2SnO4 nanocrystals with good crystallinity can be obtained in NaOH solution (2.0 M) at 240 °C for 48 h. The galvanostatic charge/discharge and cyclic voltammetry were conducted to measure the electrochemical performance of the Co2SnO4 nanocrystals. It is shown that Co2SnO4 nanocrystals exhibit good electrochemical activity with high reversible capacity (charge capacity) of 1088.8 mAh g−1 and good capacity retention as anode materials for Li-ion batteries, much better than that of bulk Co2SnO4 prepared by high temperature solid-state reaction.
Co-reporter:Z. Su, Z.W. Lu, X.P. Gao, P.W. Shen, X.J. Liu, J.Q. Wang
Journal of Power Sources 2009 Volume 189(Issue 1) pp:411-415
Publication Date(Web):1 April 2009
DOI:10.1016/j.jpowsour.2008.07.069
The indium- and sulfur-doped LiMnO2 samples with orthorhombic structure as cathode materials for Li-ion batteries are synthesized via hydrothermal method. The microstructure and composition of the samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma atom emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS) analysis. It is shown that these samples with the orthorhombic structure have irregular shapes with a grain size of about 100–200 nm. The electrochemical performance of these samples as cathode materials was studied by galvanostatic method. All doped materials can offer improved cycling stability and high rate discharge ability as compared with the un-doped Li0.99MnO2. Moreover, dual In/S doping can slow down the capacity decay to a great extent, although the transformation to spinel occurs undesirably for all the doped samples during electrochemical cycling.
Co-reporter:Q.D. Wu, S. Liu, L. Li, T.Y. Yan, X.P. Gao
Journal of Power Sources 2009 Volume 186(Issue 2) pp:521-527
Publication Date(Web):15 January 2009
DOI:10.1016/j.jpowsour.2008.09.112
Al-α-Ni(OH)2 microspheres are modified with metallic Co and Y(OH)3, respectively, in order to improve the high-temperature electrochemical performance. The microstructure, morphology, and surface chemical state of the as-prepared and the modified Al-α-Ni(OH)2 microspheres are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Metallic cobalt nanoparticles are distributed on the nanosheets of the microsphere edges. The existence of metallic Co and Y(OH)3 can be further verified from ICP and XPS results. The effect of metallic Co or Y(OH)3 on high-temperature performance of the Al-α-Ni(OH)2 microspheres is measured by galvanostatic charge–discharge experiments and cyclic voltammetric (CV) measurements. The discharge capacities of the Al-α-Ni(OH)2 microspheres, with optimized 5 wt% Co and 1 wt% Y(OH)3, are 283.5 mAh g−1 and 315 mAh g−1, respectively, much higher than that of the as-prepared Al-α-Ni(OH)2 (226.8 mAh g−1) at 0.2 C and 60 °C. Furthermore, the high-rate discharge capability at high temperature can be also improved for both the modified samples.
Co-reporter:B. Zhang, C. Lai, Z. Zhou, X.P. Gao
Electrochimica Acta 2009 Volume 54(Issue 14) pp:3708-3713
Publication Date(Web):30 May 2009
DOI:10.1016/j.electacta.2009.01.056
A sulfur–acetylene black (AB) composite was synthesized by thermally treating a mixture of sublimed sulfur and AB. The sulfur–AB composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) tests. From the results, we confirmed that sulfur was well dispersed on nano-scale and embedded inside nano-pores of the acetylene black with the steric chain structure in the composite. The electrochemical performance of the composite as cathode materials was evaluated by the galvanostatic method, cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). The sulfur–AB composite, which can effectively confine the diffusion of dissolved polysulfides in organic electrolyte and stabilize the structure during the charge and discharge process, showed high capacity and good cycle performance. The discharge capacity of the sulfur–AB composite was maintained at 500 mAh/g after 50 cycles.
Co-reporter:Y. Li, K. Xi, X.P. Gao
Materials Letters 2009 Volume 63(Issue 2) pp:304-306
Publication Date(Web):31 January 2009
DOI:10.1016/j.matlet.2008.10.018
The layered nanotubes of Li–Ti–O compound were prepared by ultrasonic treatment of sodium titanate nanotubes in LiOH solution, which was involved in the ion-exchange process. It was found that Li–Ti–O compound maintained layered structure below 400 °C and underwent phase transition to a mixture of Li-poor anatase LixTiO2 and spinel Li4Ti5O12 as the main phases at 500 and 600 °C. The lithium titanate nanotubes calcined at 400 °C exhibited the large capacity and good high rate capability.
Co-reporter:C. Lai, X. P. Gao, B. Zhang, T. Y. Yan and Z. Zhou
The Journal of Physical Chemistry C 2009 Volume 113(Issue 11) pp:4712-4716
Publication Date(Web):2017-2-22
DOI:10.1021/jp809473e
Sulfur/highly porous carbon (HPC) composites were synthesized by thermally treating a mixture of sublimed sulfur and HPC. The microstructure of the HPC and the composite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer−Emmett−Teller (BET) surface area. The specific surface area of HPC reaches up to 1472.9 m2/g, which is sharply reduced to 24.4 m2/g in the sulfur/HPC composite with 57 wt % sulfur. The electrochemical performance of the composites as cathode materials in organic electrolytes was studied by the galvanostatic method and cyclic voltammetry. The sulfur/HPC composite with 57 wt % sulfur delivers the initial high specific capacity up to 1155 mAh/g and a stable capacity of 745 mAh/g after 84 cycles at the current density of 40 mA/g. In addition, it is demonstrated that the excellent cycling stability of the sulfur/HPC composite can be obtained at different current densities. On the basis of the analysis of the microstructure and electrochemical performance, it is confirmed that HPC can effectively prevent the shuttle behavior of the lithium/sulfur battery.
Co-reporter:J. Qu, X. P. Gao, G. R. Li, Q. W. Jiang and T. Y. Yan
The Journal of Physical Chemistry C 2009 Volume 113(Issue 8) pp:3359-3363
Publication Date(Web):2017-2-22
DOI:10.1021/jp810692t
Hydrothermally synthesized titanate nanotubes are calcined at different temperatures (400−700 °C) in air to obtain TiO2(B) nanotubes, anatase nanorods, and anatase nanoparticles. The morphology and structure of the prepared samples are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). These samples with different morphologies and structures are used to fabricate photoelectrodes for dye-sensitized solar cells (DSSCs). It is found from current−voltage curve (I−V) measurements that the DSSC with anatase nanorods calcined at 600 °C shows much better photoelectrochemical performance than those using other samples, with a photovoltaic conversion efficiency of 7.71%. Electrochemical impendence spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS), and intensity-modulated voltage spectroscopy (IMVS) are used to further investigate the kinetics process of TiO2 film electrodes. The results indicate that the charge-transfer resistance and lifetime depend on the morphology and structure transformation of the synthesized TiO2 samples. The anatase nanorods, obtained from the calcination of titanate nanotubes at 600 °C, have a lower charge-transfer resistance and a longer electron lifetime, implying lower electron-hole recombination and a higher charge-collection efficiency.
Co-reporter:S.M. Yao, K. Xi, G.R. Li, X.P. Gao
Journal of Power Sources 2008 Volume 184(Issue 2) pp:657-662
Publication Date(Web):1 October 2008
DOI:10.1016/j.jpowsour.2008.01.077
Cobalt nanoparticles on an amorphous Si3N4 matrix were synthesized by direct ball-milling of Co and Si3N4 powders for an improvement of their electrochemical performance. The microstructure, morphology and chemical state of the ball-milled Co–Si3N4 composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical performance of Co–Si3N4 composites was investigated by galvanostatic charge–discharge process and cyclic voltammetry (CV) technique. It is found that metallic Co nanoparticles of 10–20 nm in size are highly dispersed on the amorphous inactive Si3N4 matrix after the ball-milling. The composite with a Co/Si molar ratio of 2/1 shows the optimized electrochemical performance, including discharge capacity and cycle stability. The formation of Co nanoparticles with a good reaction activity is responsible for the discharge capacity of the composites. The reversible faradic reaction between Co and β-Co(OH)2 is dominant for ball-milled Co–Si3N4 composite. The surface modification of the hydrogen storage PrMg12–Ni composites using Co–Si3N4 composites can enhance the initial discharge capacity based on the hydrogen electrochemical oxidation and Co redox reaction.
Co-reporter:L.P. An, X.P. Gao, G.R. Li, T.Y. Yan, H.Y. Zhu, P.W. Shen
Electrochimica Acta 2008 Volume 53(Issue 13) pp:4573-4579
Publication Date(Web):20 May 2008
DOI:10.1016/j.electacta.2007.12.075
The nanotubes of mixed TiO2(B) and anatase phases, obtained by hydrothermal synthesis and subsequent calcination, are modified with NiO nanoparticles. In the modified products, NiO nanoparticles with poor crystallinity exist inside titania tubes and are attached to the outside surface of the nanotubes according to X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectra (EDS) analysis. The titania nanotubes, modified with 5 wt.% NiO in which NiO nanoparticles were distributed homogenously, exhibit the optimal cycle performance and a good capability for high rate discharge. The lithium ion diffusion is mainly related to the anatase phase, while the electrochemical reaction activity is attributed to the TiO2(B) phase. Relative to titania nanotubes, NiO-modified nanotubes have a better electrochemical reaction activity, which is beneficial for the improvement of the high rate charge–discharge capability.
Co-reporter:H. Zhang, X.P. Gao, G.R. Li, T.Y. Yan, H.Y. Zhu
Electrochimica Acta 2008 Volume 53(Issue 24) pp:7061-7068
Publication Date(Web):15 October 2008
DOI:10.1016/j.electacta.2008.05.036
Layered hydrated sodium titanate nanotubes are synthesized via a hydrothermal reaction in alkaline solution. The as-prepared nanotubes are calcined at different temperatures (300–600 °C) in air. The microstructure of obtained samples is characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is observed that the calcined products maintain their parent tubular morphologies below 500 °C. After calcinations at 600 °C, the hollow tubular morphology could completely be converted to the short solid nanorod morphology. In the meanwhile, the monoclinic sodium hexatitanate as a main phase is formed in nanorods, coexisted with sodium trititanate as a residual phase. The electrochemical lithium storage of obtained samples is studied by galvanostatic method and cyclic voltammetry. It is demonstrated that the nanotubes calcined at 500 °C have relatively large reversible capacity, good reversibility and excellent high rate discharge capability. The lithium intercalation process is shown to have pseudocapacitive feature caused by their layered structure and open lithium insertion tunnels, which is in favor of the high rate charge/discharge capability of sodium titanate nanotubes.
Co-reporter:G. R. Li ; T. Hu ; G. L. Pan ; T. Y. Yan ; X. P. Gao ;H. Y. Zhu
The Journal of Physical Chemistry C 2008 Volume 112(Issue 31) pp:11859-11864
Publication Date(Web):July 15, 2008
DOI:10.1021/jp8038626
The relationship between morphology and function of ZnO is demonstrated by investigating its polar planes, oxygen vacancies, and catalytic activity for N-formylation. ZnO with various morphologies is controllably synthesized via simple hydrothermal reactions. Scanning electron microcopy images exhibit a variety of the as-prepared hexagonal zinc oxides: rods, disks, rings, and screw caps as a new member of ZnO morphology family. Each of the morphologies is remarkably different from the others in the proportion of the (0001) and (0001̅) polar planes in the outside surfaces of ZnO crystals. The analysis of photoluminescence spectra shows that there exist more oxygen vacancies in the samples with large polar planes. The synthesized samples are used as a catalyst for the N-formylation of aniline and show a morphology-dependent activity: ZnO with large polar planes is more catalytically active for the N-formylation reaction. This is attributed to the fact that the polar planes generate easily oxygen vacancies, which are considered as the favored sites for catalyzing the N-formylation reaction. The results suggest a positive relationship among polar planes, oxygen vacancies, and catalytic activity for N-formylation.
Co-reporter:Xi Chen Dr.;Huai-Yong Zhu ;Jin-Cai Zhao ;Zhan-Feng Zheng
Angewandte Chemie International Edition 2008 Volume 47( Issue 29) pp:5353-5356
Publication Date(Web):
DOI:10.1002/anie.200800602
Co-reporter:X. B. Ke;H. Y. Zhu;X. P. Gao;Z. F. Zheng;J. W. Liu
Advanced Materials 2007 Volume 19(Issue 6) pp:785-790
Publication Date(Web):19 FEB 2007
DOI:10.1002/adma.200601984
Layers of randomly oriented fibers arranged in a hierarchical structure as the separation layer in ceramic membranes (see figure) are shown to greatly improve the separation efficiency compared to conventionally fabricated ceramic membranes, and remove the problems of cracks, pinholes, and serious sintering. The membranes have many potential applications, for example, removing viruses and waterborne pathogens.
Co-reporter:Y. Lan;X. P. Gao;H. Y. Zhu;Z. F. Zheng;T. Y. Yan;F. Wu;S. P. Ringer;D. Y. Song
Advanced Functional Materials 2005 Volume 15(Issue 8) pp:
Publication Date(Web):25 JUL 2005
DOI:10.1002/adfm.200400353
Various sized hollow nanotubes and solid nanorods are synthesized from rutile powder (particle size ≈ 120–280 nm) using a relatively simple chemical approach in alkaline solution. The nanotubes and nanorods occur as hydrated phases: TiO2·1.25H2O and TiO2·1.0H2O, respectively. The rutile particles react in concentrated NaOH solution under hydrothermal conditions, yielding layered sodium titanate in the form of either polycrystalline nanotubes or single-crystal nanorods. The form of the product depends on the temperature and time of hydrothermal reaction: Therefore, this is a report of the template-free control of the degree of crystallinity, crystal structure, and morphology of these types of nanoscale sodium titanate products. By treating the nanotubes and nanorods with dilute HCl, the sodium ions within them could be exchanged for protons, and the morphology of the nanotubes and nanorods is retained, resulting in hydrogen titanate nanotubes and nanorods. The electrochemical performance of dehydrated hydrogen titanate nanotubes and nanorods is explored in terms of their potential performance as anode materials for lithium-ion batteries. The discharge capacity is higher for thin anatase nanorods converted from hydrogen titanate nanotubes when compared to the calcined (at 500 °C and 700 °C) products of hydrogen titanate nanorods. The significance of these findings is the possibility of fabricating delicate, nanostructured materials directly from industrial raw materials, because the natural mineral of titanium dioxide and most of the raw industrial TiO2 products exist in the rutile phase.
Co-reporter:Y. Wang, X.P. Gao, Z.W. Lu, W.K. Hu, Z. Zhou, J.Q. Qu, P.W. Shen
Electrochimica Acta 2005 Volume 50(Issue 11) pp:2187-2191
Publication Date(Web):1 April 2005
DOI:10.1016/j.electacta.2004.10.041
Nanocrystalline LaMg12–Ni composites were prepared by ball-milling a LaMg12 alloy and Ni powders with additions of small amounts of metal oxides (TiO2, Fe3O4, La2O3 and CuO). The composites with additions of small amounts of metal oxides were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the effects of the addition of the metal oxides on the electrochemical hydrogen storage were investigated. It is demonstrated that the initial discharge capacities of the composites with additions of small amounts of metal oxides were significantly higher than that of the original composite. The additions of TiO2 and Fe3O4 as catalysts improved the electrochemical hydrogen storage properties more effective than additions of La2O3 and CuO. Analysis of the electrochemical impedance spectra (EIS) showed that the function of the metal oxides was considered to reduce the electrochemical reaction resistance as catalysts and to increase the specific surface area as impurities. However, more extensive investigation is still necessary in order to improve the cyclic stability of these materials for practical application in Ni/MH batteries.
Co-reporter:X. P. Gao, Z. F. Zheng, H. Y. Zhu, G. L. Pan, J. L. Bao, F. Wu and D. Y. Song
Chemical Communications 2004 (Issue 12) pp:1428-1429
Publication Date(Web):18 May 2004
DOI:10.1039/B403252G
Rotor-like ZnO was grown from a mixture of rod-like ZnO powder and a saturated Zn(OH)42− solution under moderate hydrothermal conditions at 100 °C, in which the precursor rod-like ZnO crystal plane acts as a matrix core, and the branched nanorods showed fast epitaxial growth on the six directions around the prism core.
Co-reporter:X.P. Gao, Y. Zhang, X. Chen, G.L. Pan, J. Yan, F. Wu, H.T. Yuan, D.Y. Song
Carbon 2004 Volume 42(Issue 1) pp:47-52
Publication Date(Web):2004
DOI:10.1016/j.carbon.2003.09.015
A facile method is proposed to use LaNi2 hydrogen storage alloy as a catalyst precursor to produce metallic nickel filled carbon nanotubes. Multi-walled carbon nanotubes filled with long continuous nickel nanowire with several microns in length are synthesized through chemical vapor deposition at low temperature (550 °C). It is more efficient to fill Ni nanowires into nanotubes after the oxidation treatment of LaNi2 alloy at low temperatures, while the oxidation treatment at high temperature results in the forming of herringbone carbon nanofibers with tips of Ni nanoparticles. The metallic Ni nanowires inside the cores of carbon nanotubes could not be eliminated during the purification process in concentrated hydrochloric acid. The analysis of transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) reveals that the metallic nickel nanowires filled inside carbon nanotubes exist as a single crystalline with fcc structure.
Co-reporter:X Mi, X.P Gao, C.Y Jiang, M.M Geng, J Yan, C.R Wan
Electrochimica Acta 2004 Volume 49(Issue 20) pp:3361-3366
Publication Date(Web):30 August 2004
DOI:10.1016/j.electacta.2004.03.005
The regular and yttrium-doped spherical β-phase nickel hydroxides were synthesized by means of chemically co-precipitation. The yttrium-doping with long needle-like nanocrystallites observed by TEM promoted the formation of the spherical nickel hydroxide with the larger diameter of about 5 μm. The discharge capacity of the yttrium-doped spherical nickel hydroxide was measured to be slightly lower than that of the regular spherical nickel hydroxide at room temperature. At temperatures of above 50 °C, however, the discharge capacity of the yttrium-doped nickel hydroxide is much higher than that of the regular spherical nickel hydroxide. The improvement of discharge capacity at elevated temperatures was contributed to the increase of the charge acceptance of yttrium-doped nickel hydroxide. The formation of an yttrium-rich surface layer on nickel hydroxide particles raised the oxygen evolution over-potential, leading to performance improvements of the nickel hydroxide electrode. The improvement of high temperature charge acceptance of yttrium-doped nickel hydroxide remarkably contributed to the high temperature charge–discharge efficiency of the nickel–metal hydride (Ni–MH) batteries with a commercial AAA size.
Co-reporter:S.H. Ye, J.Y. Lv, X.P. Gao, F. Wu, D.Y. Song
Electrochimica Acta 2004 Volume 49(9–10) pp:1623-1628
Publication Date(Web):15 April 2004
DOI:10.1016/j.electacta.2003.12.001
LiMn2O4 spinel phase having a single crystal structure with the grain sizes of 20–30 nm is synthesized at lower temperature of 500 °C after a ball-milling promoted solid-state reaction. The interplanar spacing of LiMn2O4 is calculated to be ca. 0.47 nm, which is corresponding to the same orientation of atomic plane (1 1 1). TG, SEM, XRD and TEM are used to measure the process of the heat treatment and microstructure of synthesized LiMn2O4. The high rate discharge capability is improved due to the strong interaction of nanomaterials with lithium ion occurred mostly at the surface rather than bulk. The improvement of the high rate discharge capability of electrodes is confirmed further by comparing electrochemical reaction activity and diffusion property of the electrode with nanostructure. However, the cyclic performance of LiMn2O4 spinel phase with nanostructure declined rapidly to a certain extent.
Co-reporter:S Li, G.L Pan, X.P Gao, J.Q Qu, F Wu, D.Y Song
Journal of Alloys and Compounds 2004 Volume 364(1–2) pp:250-256
Publication Date(Web):11 February 2004
DOI:10.1016/S0925-8388(03)00535-8
The MmNi3.6Co0.7Al0.3Mn0.4 alloy surface is modified with multiwalled carbon nanotubes and carbon black (10 wt.%) by ball milling for 50 min. The microstructures of the obtained materials are examined and analyzed by X-ray diffraction, SEM and TEM. It is confirmed that the surface of AB5 alloy is modified by shorter carbon nanotubes and thin carbon flake, respectively, when carbon nanotubes and carbon black are added. The electrochemical properties of the obtained materials are measured and compared with those of the original AB5 alloy. It is found that high rate discharge ability of the alloys after surface modification by carbon nanomaterials increases to some extent due to the decrease of electrochemical reaction resistance and the increase of double capacitance as obtained by electrochemical impedance spectra. In particular, the modified alloy with the carbon nanotubes shows a superior performance to carbon black, especially in the discharge rate of 2000 mA/g. Besides, the addition of carbon nanomaterials reduces the extent of the amorphism of the AB5 alloy during ball milling.
Co-reporter:X. Chen, Y. Zhang, X.P. Gao, G.L. Pan, X.Y. Jiang, J.Q. Qu, F. Wu, J. Yan, D.Y. Song
International Journal of Hydrogen Energy 2004 Volume 29(Issue 7) pp:743-748
Publication Date(Web):July 2004
DOI:10.1016/j.ijhydene.2003.08.010
The partially aligned carbon nanotubes are successfully prepared by catalytic decomposition of methane at the surface of wafer consisting of the oxidized and reduced product of LaNi5 hydrogen storage alloy with Ni powder. The CNTs are straight with a larger inner hollow core of 20–, whereas the long CNFs are curved with an inner hollow core of 6–. In addition, the long continuous metallic Ni nanowires with several microns in length are observed inside nanotubes after purification in concentrated hydrochloric acid. The purified partially aligned carbon nanotubes show a high electrochemical discharging capacity up to , corresponding to a hydrogen storage capacity of , while the maximal discharge capacity of carbon nanofiber electrode is , indicating that the partially aligned carbon nanotubes with open tips obtained provide a potential way to improve their electrochemical hydrogen storage due to the different structure.
Co-reporter:Shang Li, Guiling Pan, Ying Zhang, Xueping Gao, Jingqiu Qu, Jie Yan, Feng Wu, Deying Song
Journal of Alloys and Compounds 2003 Volume 353(1–2) pp:295-300
Publication Date(Web):7 April 2003
DOI:10.1016/S0925-8388(02)01296-3
MmNi3.6Co0.7Al0.3Mn0.4 alloys containing carbon nanotubes were prepared by an arc-melting method. It was confirmed by SEM images that a few carbon nanotubes coated or uncoated with AB5 alloy stuck out of the surface of the alloy. The effects of the addition of carbon nanotubes on the structure and the electrochemical characteristics of AB5-type alloy were investigated by XRD and electrochemical measurements. Discharge plateau curves of sigmoid shape were clearly observed for AB5-CNT electrodes during the initial activation, which was different from the original AB5 electrode. In addition, the results indicate that, with the addition of carbon nanotubes, the unit cell volume decreased resulting in a decrease of the stability of the metal hydride and an increase in the discharge plateau potential. The discharge capacity for the alloys decreased with decreasing stability of the metal hydride due to the decrease of maximum amount of the absorbed hydrogen, but the high-rate dischargeability was improved due to the increase in the rate of hydrogen diffusion in the alloys. The capacity retaining ability of the alloys did not remarkably decrease with the addition of carbon nanotubes.
Co-reporter:Xiaoqi Yan, Xueping Gao, Ying Li, Zhanquan Liu, Feng Wu, Yutian Shen, Deying Song
Chemical Physics Letters 2003 Volume 372(3–4) pp:336-341
Publication Date(Web):29 April 2003
DOI:10.1016/S0009-2614(03)00427-5
Abstract
The tube-like CNFs with cone-shaped structure were synthesized by catalytic pyrolysis of methane. The outer surface of purified CNFs was decorated with Ni–P alloy particles having polycrystalline or nanocrystalline structure instead of amorphous structure. The low Ni–P content appeared to be more efficient to cover the outer surface of CNFs. The electrochemical discharge capacity increased with increasing the Ni–P content on the outer surface of CNFs owing to the synergistic effect between metal and carbon in the electrochemical reaction. The heat treatment contributed to the higher crystallization of surface alloy and improvement of the electrochemical capacity of the composite.
Co-reporter:Yunyun Gui, Yuliang Cao, Guoran Li, Xinping Ai, Xueping Gao, Hanxi Yang
Energy Storage Materials (October 2016) Volume 5() pp:165-170
Publication Date(Web):1 October 2016
DOI:10.1016/j.ensm.2016.07.004
Solar fuels and fuel cells are two of the key enabling technologies for clean and sustainable electricity generation. However, photo-synthesis of hydrocarbon or hydrogen fuels is kinetically slow and low efficient, while the current fuel cells use pure hydrogen fuel and precious metal electro-catalysts, which pose severe cost and resource restraints for commercial application. Here, we propose and construct a solar storable fuel cell (SSFC) based on the photo-oxidation of organic wastes and the oxygen reduction reaction at the MnO2 air cathode, which generates electricity with simultaneous photo-degradation of organic contaminants in waste water. As a proof-of-principle device, the SSFC delivers a stable voltage of +0.6 V at constant current of 20 μA cm−2 with almost complete degradation of methyl orange in aqueous solution in an hour, demonstrating an effective utilization of the organic waste for direct electricity generation.
Co-reporter:Lu Wang, Guo-Ran Li, Qian Zhao, Xue-Ping Gao
Energy Storage Materials (April 2017) Volume 7() pp:40-47
Publication Date(Web):1 April 2017
DOI:10.1016/j.ensm.2016.11.007
Usually, perovskite solar cells employ gold or silver as counter electrode materials. The use of the precious metals is a serious obstacle to the practical application of perovskite solar cells. In this work, low-cost non-precious transition metals are investigated to replace gold or silver as counter electrode materials in perovskite solar cells. Under optimized conditions, perovskite solar cells with Cu, Ni, W, and Mo films, prepared by magnetron sputtering deposition, present satisfactory performance with the power conversion efficiency of 13.04, 12.18, 12.38, and 11.38%, respectively, as compared with that (15.97%) of the perovskite solar cell with Ag counter electrode. Even though a slightly loss in efficiency, these non-precious transition metals are the promising candidates to the counter electrode of perovskite solar cells on the aspect of the practicality and cost performance ratio.Perovskite solar cells with non-precious metal (Cu, Ni, W, and Mo) films as low-cost counter electrode materials present satisfactory performance with the power conversion efficiency.Download high-res image (163KB)Download full-size image
Co-reporter:Y. Y. Dou, G. R. Li, J. Song and X. P. Gao
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 4) pp:NaN1342-1342
Publication Date(Web):2011/11/29
DOI:10.1039/C2CP23775J
Nickel phosphide-embedded graphene, prepared by the hydrothermal reaction of red phosphorus, nickel chloride, and graphene oxide in a mixture of ethylene glycol–water, is investigated as the counter electrode of DSSCs. It is demonstrated that the DSSC with the nickel phosphide-embedded graphene as the new counter electrode presents an excellent performance competing with that of the Pt electrode.
Co-reporter:Q. Q. Qiao, H. Z. Zhang, G. R. Li, S. H. Ye, C. W. Wang and X. P. Gao
Journal of Materials Chemistry A 2013 - vol. 1(Issue 17) pp:NaN5268-5268
Publication Date(Web):2013/03/15
DOI:10.1039/C3TA00028A
Enhancement of the discharge capacity, high-rate capability, and cycle stability of the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide with a large specific capacity is highly significant for high energy lithium-ion batteries. In this work, the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide is prepared by a spray-drying method. The surface modification with the Li–Mn–PO4 is introduced onto Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide for the first time. It is demonstrated that the surface of Li(Li0.17Ni0.25Mn0.58)O2 grains is coated with the thin amorphous Li–Mn–PO4 layer (5 wt%). With increasing calcination temperature after the surface coating, a strong interaction can be induced on the interface between the amorphous Li–Mn–PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O2 grains. As anticipated, the discharge capacity and high-rate capability are obviously improved for the Li–Mn–PO4-coated sample after calcination at 400 °C, while excellent cycle stability is obtained for the Li–Mn–PO4-coated sample after calcination at 500 °C as compared with the as-prepared Li(Li0.17Ni0.25Mn0.58)O2 oxide during cycling. Apparently, the interface interaction between the amorphous Li–Mn–PO4 layer and the top surface of Li(Li0.17Ni0.25Mn0.58)O2 grains is responsible for the improvement of the reaction kinetics and the electrochemical cycle stability of Li–Mn–PO4-coated samples.
Co-reporter:H. Z. Zhang, Q. Q. Qiao, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 20) pp:NaN7460-7460
Publication Date(Web):2014/03/06
DOI:10.1039/C4TA00699B
Advanced Li-ion batteries, with Li-rich layered oxides as cathode materials and Si-based composites as anode materials, are considered as high energy battery systems for the next generation of smart communications and electric vehicles (EVs). At the current stage, it is significant to develop Li-rich layered oxides with stable output energy density. However, the gradual capacity degradation and potential decay during cycling lead to the continual decrease in the energy density of Li-rich layered oxides. Therefore, a new strategy should be introduced to block the migration of transition metal cations and maintain the parent layered structure during cycling, in order to stabilize the energy density of oxides. In this work, large tetrahedral PO43− polyanions with high electronegativity with respect to O2− anions are doped into oxides for minimizing the local structure change during cycling. When doping with PO43− polyanions, the parent layered structure is retained during long cycling, due to the strong bonding of PO43− polyanions to transition metal cations (Ni especially). Correspondingly, PO43− polyanion-doped oxides present excellent energy density retention during long cycling, integrated with the discharge capacity and midpoint potential. These results suggest that polyanion-doping can meet the performance requirement of stabilizing the energy density of Li-rich layered oxides for advanced lithium ion batteries.
Co-reporter:Ming Zhao, Yu Fu, Ning Xu, Guoran Li, Mengtao Wu and Xueping Gao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 36) pp:NaN15077-15077
Publication Date(Web):2014/07/18
DOI:10.1039/C4TA03311F
A carbon matrix, for restricting growth of LiMnPO4 crystallites, is built on the small Li3PO4 crystallites precipitated from aqueous solutions, by the pyrolysis of sucrose. LiMnPO4 is prepared using the carbon coated Li3PO4 as one of the reactants (the other reactant is MnSO4) and the nuclei by a solvothermal method. Smaller-crystallite-size (8–12 nm) LiMnPO4 is successfully obtained on the carbon matrix by a crystallite size control method. The as-prepared LiMnPO4/C sample presents the desired electrochemical performance, including higher discharge potential plateau, larger discharge capacity, excellent high-rate capability, and good cycle stability. It is also confirmed that the smaller LiMnPO4 crystallites on the carbon matrix are beneficial for shortening the lithium ion diffusion path and increasing the electrical conductivity of the LiMnPO4/C sample, contributing to an improvement in electrochemical performance. The methodology described in this work could be helpful in the development of LiMnPO4/C cathode materials for lithium ion batteries with high energy density.
Co-reporter:Y. Z. Zhang, S. Liu, G. C. Li, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 13) pp:NaN4659-4659
Publication Date(Web):2014/01/07
DOI:10.1039/C3TA14914E
Sulfur/polyacrylonitrile(PAN)/carbon multi-composites with different sulfur content are prepared based on dual-mode of fixing sulfur on the matrix of the partially carbonized PAN (cPAN) and activated-conductive carbon black (A-CCB). The electrochemical performance of the as-prepared multi-composites as active materials are tested in the electrolyte with a high concentration lithium salt (LiTFSI) in different mixed solvents of 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME), and 1,3-dioxolane (DOL)/tetraethylene glycol dimethyl ether (TEGDME), respectively. It is demonstrated that the high concentration lithium salt (LiTFSI) and high viscous solvent have a great impact on the cycle stability of the multi-composite by suppressing polysulfide dissolution at the slight expense of the discharge potential plateaus (width and height). The as-prepared multi-composites present the excellent cycle performance in the electrolyte with 5 M LiTFSI in DOL/DME. Meanwhile, when the lower viscous DME solvent is replaced by the higher viscous TEGDME solvent in the electrolyte with 3 M LiTFSI, the optimized cycle stability is still obtained for the as-prepared multi-composites based on the evaluation of the discharge capacity and cycle stability. Therefore, the electrochemical performance of the as-prepared multi-composites is obviously influenced by the common ion effect and viscosity of the electrolyte, which are induced from both the lithium salt and solvent.
Co-reporter:Qi-Qi Qiao, Lei Qin, Guo-Ran Li, Yong-Long Wang and Xue-Ping Gao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 34) pp:NaN17634-17634
Publication Date(Web):2015/07/21
DOI:10.1039/C5TA03415A
Li-rich layered oxides have been intensively investigated as cathodes for high energy lithium-ion batteries. However, oxygen loss from the lattice during the initial charge and gradual structural transformation during cycling can lead to capacity degradation and potential decay of the cathode materials. In this work, Sn4+ is used to partially substitute Mn4+ to prepare a series of Li(Li0.17Ni0.25Mn0.58−xSnx)O2 (x = 0, 0.01, 0.03, and 0.05) samples through a spray-drying method. Structural characterization reveals that the Sn4+ substituted samples with a suitable amount show low cation mixing, indicating an enhanced ordered layer structure. Moreover, the metal–oxygen (M–O) covalency is gradually decreased with increasing Sn4+ amount. It is shown from the initial charge–discharge curves that Sn4+ substituted samples present a shorter charging potential plateau at 4.5 V (vs. Li/Li+), implying that oxidation of the O2− ion to O2 is suppressed by Sn4+ substitution and leads to a minor structural change. Among the Sn4+ substituted samples, the Li(Li0.17Ni0.25Mn0.55Sn0.03)O2 sample exhibits a higher capacity retention of 86% after 400 cycles at 0.1C rate and 92% after 200 cycles at 1C rate, showing excellent cycle stability and high-rate capability as compared with the as-prepared sample. The electrochemical performance improvement can be attributed to the influences of Sn such as enlarging the Li ion diffusion channel due to the large ionic radius of Sn4+ substitution with respect to Mn4+, a higher bonding energy of Sn–O than Mn–O, and weakening the M–O covalency. All the influences are favorable for stabilization of the host lattice in Li-rich layered oxides.
Co-reporter:Ze Zhang, Hang-Kun Jing, Sheng Liu, Guo-Ran Li and Xue-Ping Gao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 13) pp:NaN6834-6834
Publication Date(Web):2015/02/06
DOI:10.1039/C4TA07183B
A hybrid carbon substrate as a sulfur immobilizer is obtained via simple processes to fabricate cathode materials for lithium–sulfur batteries. The microstructure and morphology of the sulfur/carbon composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is demonstrated that commercial carbon black and multi-walled carbon nanotubes (CNTs) in the hybrid substrate cooperate well with each other in an appropriate mass ratio. In particular, a large sulfur content of 81.7 wt% can be loaded into the hybrid carbon substrate forming the sulfur/carbon composite. When the mass ratio of carbon black and CNTs is 1:1, the composite delivers a high initial capacity of 837.3 and 685.9 mA h g−1(composite) at the current densities of 80 and 160 mA g−1(composite) when used as a cathode-active material. The discharge capacity remains at 554.4 mA h g−1(composite) at a current density of 160 mA g−1(composite) after 150 cycles, indicating a low capacity fading of about 0.12% per cycle. Besides, the composite offers a high Coulombic efficiency of about 100%. The significant improvements in the electrochemical performance are associated with the desirable combination of carbon black and CNTs in the hybrid carbon substrate. Therefore, this work proposes a low-cost and effortless approach to prepare sulfur/carbon composites with high performance as cathodes for lithium–sulfur batteries.
Co-reporter:Hang-Kun Jing, Ling-Long Kong, Sheng Liu, Guo-Ran Li and Xue-Ping Gao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 23) pp:NaN12219-12219
Publication Date(Web):2015/05/06
DOI:10.1039/C5TA01490E
The performance of the metallic lithium anode is one of the major factors that affect the cycle stability of a lithium–sulfur battery. The protection of the lithium anode is extremely essential, especially for lithium–sulfur full-cells. Here, a porous Al2O3 layer is fabricated on the surface of a metallic lithium anode by using a spin-coating method as protective layer for a lithium–sulfur battery. The porous Al2O3 protective layer acts as a stable interlayer and suppresses the side reactions between soluble lithium polysulfides and lithium anode by direct contact during the charge–discharge process. In addition, the inhomogeneous dissolution–deposition reaction, and the formation of serious cracks on the protected lithium anode are suppressed to a certain extent, which is beneficial to ensure the good and stable electrochemical activity of the lithium anode. Correspondingly, the sulfur cathode with the protected lithium anode exhibits improved electrochemical performance, accompanied simultaneously with relatively homogeneous lithium deposition on the anode surface due to the even distribution of Li ion flux via the Al2O3 protective layer.
Co-reporter:S. Liu, G. L. Pan, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2015 - vol. 3(Issue 3) pp:NaN962-962
Publication Date(Web):2014/11/27
DOI:10.1039/C4TA04644G
Copper hexacyanoferrate (CuHCF) nanoparticles with Prussian blue structure are prepared via a simple co-precipitation method, which present the ability to insert Al ions reversibly in aqueous solution. CuHCF is verified to be a promising cathode material for aqueous Al-ion batteries.
Co-reporter:Q. W. Jiang, G. R. Li and X. P. Gao
Chemical Communications 2009(Issue 44) pp:NaN6722-6722
Publication Date(Web):2009/09/25
DOI:10.1039/B912776C
TiN nanotube arrays, prepared by the anodization of metallic Ti foil substrate and subsequent simple nitridation in an ammonia atmosphere, were investigated as low-cost counter electrodes in dye-sensitized solar cells for the first time. It is found that the highly ordered TiN nanotube arrays on the metallic Ti foil substrate show an excellent performance, comparable with typical Pt counter electrodes.
Co-reporter:Xue Bin Ke, Ren Fu Shao, Huai Yong Zhu, Yong Yuan, Dong Jiang Yang, Kyle R. Ratinac and Xue Ping Gao
Chemical Communications 2009(Issue 10) pp:NaN1266-1266
Publication Date(Web):2009/01/15
DOI:10.1039/B819292H
Ceramic membranes were fabricated by in situ synthesis of aluminananofibres in the pores of an alumina support as a separation layer, and exhibited a high permeation selectivity for bovine serum albumin relative to bovine hemoglobin (over 60 times) and can effectively retain DNA molecules at high fluxes.
Co-reporter:J. J. Hu, G. K. Long, S. Liu, G. R. Li and X. P. Gao
Chemical Communications 2014 - vol. 50(Issue 93) pp:NaN14650-14650
Publication Date(Web):2014/10/03
DOI:10.1039/C4CC06666A
LiFSI and LiTFSI are combined to form a binary-salt electrolyte with higher ionic conductivity and lower viscosity for a Li–S battery. A high capacity and stable cycle performance of the sulfur-based composite with high sulfur content are realized in the electrolyte, accompanied simultaneously by the homogeneous lithium deposition on the anode.
Co-reporter:Qi-Qi Qiao, Guo-Ran Li, Yong-Long Wang and Xue-Ping Gao
Journal of Materials Chemistry A 2016 - vol. 4(Issue 12) pp:NaN4447-4447
Publication Date(Web):2016/02/25
DOI:10.1039/C6TA00882H
Li-rich layered oxides with a large discharge capacity have attracted considerable attention as cathodes for high energy lithium-ion batteries. To further enhance the discharge capacity and thermal stability of these Li-rich layered oxides, Mn-based metal–organic frameworks (MOFs) with high surface areas, large pore sizes, and stable architectures are employed as the active coating material. Herein, Mn-based MOFs can partially absorb or store oxygen gas originating from the oxidation of oxygen anions from the host lattice of Li-rich layered oxides in the initial charging stage to above 4.5 V (vs. Li/Li+). Moreover, the structure of the Li-rich layered oxide could be strengthened by the interconnection frameworks between the metal cations and organic ligands. As expected, the Li-rich layered Li(Li0.17Ni0.20Co0.05Mn0.58)O2 oxide modified with a MOF exhibits a large discharge capacity (323.8 mA h g−1 at 0.1C rate), high initial coulombic efficiency (91.1%), and good thermal stability without harming the cycle stability and high-rate capability. Surface modification with MOFs offers a new insight for further enhancing the discharge capacity of Li-rich layered oxides as cathodes for advanced lithium-ion batteries.
Co-reporter:Peiyu Hou, Guoran Li and Xueping Gao
Journal of Materials Chemistry A 2016 - vol. 4(Issue 20) pp:NaN7699-7699
Publication Date(Web):2016/04/11
DOI:10.1039/C6TA01878E
Li-rich layered oxides with large capacity are considered as one of the most promising cathode materials for the next generation lithium-ion batteries (LIBs). However, Li-rich layered oxides usually deliver unsatisfactory volumetric energy density, poor cycle life and inferior thermal stability. Here, a concentration-gradient doping strategy is introduced for the first time to meet the above challenges. Surprisingly, the atomic distribution in micron-sized and spherical Li-rich layered oxides is tailored after concentration-gradient PO43− polyanion doping, in which Ni and Co atoms decrease continually and Mn atoms increase gradually from the center to the surface in a single particle. As expected, the concentration-gradient PO43− doped oxides exhibit a high initial volumetric energy density of 2027 W h L−1, long cycle life with a capacity retention of 88.2% within 400 cycles, and enhanced thermal stability. These improved performances are believed to be attributed to the formation of the stable Mn-rich and PO43−-rich shell layer, which is beneficial to mitigate the interreaction between Ni4+/Co4+ and the electrolyte in the highly delithiated state and suppress the aggregation of primary grains during cycles. These results demonstrate the feasibility of manipulating atomic distribution by the innovative concentration-gradient doping means, which also provides new insights into desired cathode for LIBs.
Co-reporter:J. T. Zhang, S. Liu, G. L. Pan, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 5) pp:NaN1529-1529
Publication Date(Web):2013/11/19
DOI:10.1039/C3TA13578K
Supercapacitors are the most promising energy storage devices by virtue of high power density, long cycle life, short charging time and environmental benignity. In order to enhance the energy density, rate capability and cycle stability for supercapacitors, a α-Ni(OH)2/graphite nanosheet composite is prepared via a homogeneous precipitation method. The morphology and microstructure of the as-prepared composite are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. It is demonstrated that after introducing the graphene oxide nanosheets into α-Ni(OH)2, a 3D hierarchical porous structure of fine α-Ni(OH)2 nanocrystals as building blocks is formed directly on the matrix of graphite nanosheets in the presence of urea as a mild reducing agent. The electrochemical performance of the as-prepared α-Ni(OH)2 and α-Ni(OH)2/graphite nanosheet composites as electro-active materials for supercapacitors is investigated by a galvanostatic charge–discharge method. As expected, the as-prepared α-Ni(OH)2/graphite nanosheet composite exhibits large specific capacitance, good rate capability and long cycle stability as compared to the pure α-Ni(OH)2. Apparently, the unique structure of fine α-Ni(OH)2 nanocrystals fabricated on the matrix of graphite nanosheets is responsible for the improvement of the reaction kinetics and subsequent electrochemical performance of the composite.
Co-reporter:P. Y. Hou, L. Q. Zhang and X. P. Gao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 40) pp:NaN17138-17138
Publication Date(Web):2014/08/21
DOI:10.1039/C4TA03158J
Ni-rich Li[Ni1−xMx]O2 (M = Co, Mn and Al) cathodes have shortcomings of poor thermal stability at the delithiated state and insufficient cycle performance, which are unsatisfied for commercial application in lithium ion batteries. Herein, a nickel-rich lithium transition-metal oxide with the full concentration-gradient structure is designed to overcome those problems. In the full concentration-gradient oxide, the nickel concentration decreases linearly, and the manganese concentration increases gradually, whereas the cobalt concentration remains constant from the center to the surface of each particle based on the energy disperse spectrum (EDS) analysis on the cross-section of a single particle. Firstly, the full concentration-gradient precursor is successfully prepared via a newly developed co-precipitation route. After lithiation at 800 °C, the as-prepared full concentration-gradient and normal oxides could be indexed to a typical layered structure with an Rm space group as detected by X-ray diffraction (XRD). Correspondingly, the full concentration-gradient layered oxide delivers more excellent cycle stability (especially at 55 °C), and thermal stability as compared with the normal layered oxide. It is also found that the Ni dissolution in the electrolyte is more serious, resulting in inferior cycle life for the normal layered oxide. Whereas, the outer layer of the full concentration-gradient oxide is much more stable, contributing to such excellent cycle and thermal stability.
Co-reporter:N. F. Yan, G. R. Li and X. P. Gao
Journal of Materials Chemistry A 2013 - vol. 1(Issue 24) pp:NaN7015-7015
Publication Date(Web):2013/05/01
DOI:10.1039/C3TA11360D
A solar rechargeable redox flow battery is fabricated with Li2WO4 as anode in aqueous electrolyte, LiI as cathode in organic electrolyte, and LISICON film as membrane to separate liquid anode/cathode-active species. The as-fabricated battery presents feasible solar rechargeable capability.
Co-reporter:J. Song, G. R. Li, F. Y. Xiong and X. P. Gao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 38) pp:NaN20585-20585
Publication Date(Web):2012/08/14
DOI:10.1039/C2JM34878K
As a counter electrode for dye-sensitized solar cells (DSSCs), MoN presents a high intrinsic electrocatalytic activity for the reduction of triiodide ions. However, the photovoltaic performance of DSSCs with a MoN counter electrode is hindered by the large diffusion impedance of the MoN electrode. In response to this problem, a MoN–carbon nanotube (CNT) composite is prepared by nitridation of the precursor MoO2–CNTs, fabricated via a hydrothermal reaction of ammonium molybdate and carboxyl-functionalized CNTs. In the composite, MoN nanoparticles are well and stably dispersed on the surface of the CNTs, with a particle size of several tens of nanometers. Employing the composite as a counter electrode, the DSSC shows an energy conversion efficiency of 6.74%, which is much higher than that (5.57%) of the DSSC using pure MoN nanoparticles. The improvement is mainly attributed to a synergistic effect between the MoN nanoparticles and CNTs on ion diffusion and electrocatalysis. Electrochemical impedance spectra (EIS) indicate that the MoN–CNTs electrode has a lower ion diffusion impedance. It is believed that the smaller size of the MoN nanoparticles and the abundant porous structure in the MoN–CNTs composite are able to shorten the ion diffusion path and improve ion diffusion flux.
Co-reporter:H. Z. Zhang, Q. Q. Qiao, G. R. Li, S. H. Ye and X. P. Gao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 26) pp:NaN13109-13109
Publication Date(Web):2012/05/02
DOI:10.1039/C2JM30989K
A Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide is prepared by a combination of co-precipitation and solid-state reaction. The surface nitridation is introduced into a Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 for the first time via heating at 400 °C in the ammonia atmosphere. The microstructure and morphology of the two samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that the nitrogen exists with a trace amount in the surface layer of the Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2 oxide after the nitridation treatment. Electrochemical performances of the electrodes are measured by galvanostatic charge–discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). As expected, the discharge capacity, high-rate capability and cycle stability of the nitrided sample are improved dramatically as compared with the as-prepared sample, which is further confirmed by the high electrocatalytic activity and accelerated lithium diffusion process. Apparently, the existence of nitrogen in the surface layer is responsible for the improvement of the reaction kinetics and electrochemical performance of the nitrided sample.
![1H-Pyrrole-2-carboxamide, N-(aminoiminomethyl)-5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-, hydrochloride (1:1)](http://img.cochemist.com/data/images/1363380-39-5.png)
![1H-Pyrrole-2-carboxamide, N-(aminoiminomethyl)-5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-, hydrochloride (1:1)](http://img.cochemist.com/data/images/1363380-39-5_b.png)
![Carbamic acid, N-[[[[5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-1H-pyrrol-2-yl]carbonyl]amino]iminomethyl]-, 1,1-dimethylethyl ester](/data/chemimg/140000/1363380-38-4.png)
![Carbamic acid, N-[[[[5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-1H-pyrrol-2-yl]carbonyl]amino]iminomethyl]-, 1,1-dimethylethyl ester](/data/chemimg/140000/1363380-38-4_b.png)
![1H-Pyrrole-2-carboxylic acid, 5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-, methyl ester](/data/chemimg/140000/1363380-36-2.png)
![1H-Pyrrole-2-carboxylic acid, 5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-, methyl ester](/data/chemimg/140000/1363380-36-2_b.png)
![1H-Pyrrole-2-carboxylic acid, 5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-](/data/chemimg/140000/1363380-37-3.png)
![1H-Pyrrole-2-carboxylic acid, 5-[4-[[bis(2-pyridinylmethyl)amino]methyl]benzoyl]-](/data/chemimg/140000/1363380-37-3_b.png)
![1H-Pyrrole-2-carboxylic acid, 5-[4-(bromomethyl)benzoyl]-, methyl ester](/data/chemimg/140000/1363380-35-1.png)
![1H-Pyrrole-2-carboxylic acid, 5-[4-(bromomethyl)benzoyl]-, methyl ester](/data/chemimg/140000/1363380-35-1_b.png)
