Co-reporter:Jing Bai, Baojuan Xi, Zhenyu Feng, Junhao Zhang, Jinkui Feng, and Shenglin Xiong
ACS Omega October 2017? Volume 2(Issue 10) pp:6415-6415
Publication Date(Web):October 5, 2017
DOI:10.1021/acsomega.7b01146
Integration of bicomponents into a greater object or assemblage is a new avenue to acquire multifunctionality for metal oxide-based anodes for lithium-ion batteries (LIBs). Herein, we report a versatile means by which precursors serve as self-sacrificing templates to form architectures of SnO2 phase and other metal oxides. The vital challenge is the determination of appropriate synthetic system that can benefit the formation of respective precursors in a structure or single-source precursors of tin and other metal species. In the current work, by the aids of synergy action between l-proline and ethylene glycol (EG), precursors containing two metal ions are generally fabricated. Adequate flexibility of the present method has been achieved for SnO2/MxOy hierarchical hybrids, including Mn2O3, Co3O4, NiO, and Zn2SnO4, by calcination of their corresponding SnMn, SnCo, SnNi, and SnZn precursors, respectively. When evaluated as anode materials for LIBs, the obtained SnO2/Mn2O3 homogeneous hybrids, as expected, show higher specific capacity and ultralong cycling stability, gaining a reversible specific capacity of 610.3 mA h g–1 after 600 cycles with only decay of 0.29 mA h g–1 per cycle at 1 A g–1 and 487 mA h g–1 after 1001 cycles at a high current density of 2 A g–1.Topics: Batteries; Composites; Diffraction; Heat treatment; Inorganic chemistry; Mechanical properties; Nanostructured materials; Nanostructures;
Co-reporter:Yong Jiang, Yibo Guo, Wenjun Lu, Zhenyu Feng, Baojuan Xi, Shuangshuang Kai, Junhao Zhang, Jinkui Feng, and Shenglin Xiong
ACS Applied Materials & Interfaces August 23, 2017 Volume 9(Issue 33) pp:27697-27697
Publication Date(Web):August 1, 2017
DOI:10.1021/acsami.7b06572
Herein, we have designed and first synthesized a unique ternary hybrid structure by simultaneously growing SnS2 and MoS2 particles on graphene sheets (denoted as MoS2/SnS2-GS) via one-pot hydrothermal route. The charge incompatibility between MoO42– and graphene oxide with negative charged functional groups on surface can be compromised with the aid of Sn4+ cations, which renders the final formation of SnS2 and MoS2 on GS surface. This is the first report of the cohybridization of MoS2 and SnS2 with GS matrix from anionic and cationic precursors in the absence of premedication of graphene surface. When MoS2/SnS2-GS acts as anodes for lithium-ion batteries, the hybrids exhibit much better cycling stability than MoS2-GS and SnS2-GS counterparts. The compact adhesion of MoS2/SnS2 nanoparticles helps offset the undesired result of destruction of electrode materials resulting from volume expansion during repeated cycles. Furthermore, by combination with their synergetic effect on interface and the presence of discrepant asynchronous electrochemical reactions for SnS2 and MoS2, MoS2/SnS2-GS hybrids are endowed with improvement of electrochemical capabilities. Besides, they also showed outstanding Na-storage ability.Keywords: graphene; Li-ion batteries; MoS2; Na-ion batteries; SnS2;
Co-reporter:Man Huang;Kan Mi;Junhao Zhang;Huili Liu;Tingting Yu;Aihua Yuan;Qinghong Kong
Journal of Materials Chemistry A 2017 vol. 5(Issue 1) pp:266-274
Publication Date(Web):2016/12/20
DOI:10.1039/C6TA09030C
To tackle the issue of the low specific capacity (372 mA h g−1) of graphite as the anode material for lithium-ion batteries (LIBs), an effective and controllable strategy was developed to construct porous bimetallic Co/Zn embedded N-doped carbon (Co–Zn/N–C) polyhedral nanocages via annealing a ZIF-8@ZIF-67 precursor at 800 °C under Ar atmosphere. The results clearly displayed that metallic Co and Zn particles are uniformly dispersed in the carbon matrix. Porous Co–Zn/N–C polyhedral nanocages have a large specific surface area of 349.12 m2 g−1 and contain plenty of micropores and mesopores, which benefit from the carbonization of organic ligands and the catalytic effect of cobalt in the calcination process. As anodes for LIBs, the porous Co–Zn/N–C polyhedral nanocages showed an initial discharge capacity of 809 mA h g−1 and a capacity retention of 702 mA h g−1 after 400 cycles at a current density of 0.2 A g−1. Furthermore, a reversible capacity of 444 mA h g−1 was obtained at a much higher current density of 2 A g−1. The improved electrochemical performance was attributed to the synergistic effect of Zn and Co, the unique porous hollow structure as well as N doping, which relieved the impact of volume changes, maintained perfect electrical conductivity throughout the electrode and enhanced the electrochemical activities of lithium storage.
Co-reporter:Xiaohui Guo;Min Zhang;Jing Zheng;Jingli Xu;Tasawar Hayat;Njud S. Alharbi;Baojuan Xi
Dalton Transactions 2017 vol. 46(Issue 35) pp:11598-11607
Publication Date(Web):2017/09/11
DOI:10.1039/C7DT02095C
In this paper, an extended Stöber method has been developed to fabricate a Ni2+-polydopamine (PDA) complex coated on Co3[Co(CN)6]2@SiO2 composites. After one-step carbonization involving the heat treatment of a Prussian blue analogue (PBA) of Co3[Co(CN)6]2 cores and the PDA-Ni2+ shell under a nitrogen atmosphere, homogeneous Co@SiO2@C/Ni submicrorattles were synthesized. Notably, the silica interlayer played a vital role in the formation of such Co@SiO2@C/Ni submicrorattle structures. Without the protection of SiO2, Co–Ni@C composites were obtained instead and aggregated seriously due to sintering at high temperature. While with the silica layer as the spacer, the obtained Co@SiO2@C/Ni composites were not only well dispersed in the solution, but could also be adjusted in terms of the size and density of Ni nanoparticles (NPs) on the surface. Moreover, the size of core Co and surficial Ni NPs can be facilely modulated via changing the calcination temperature, which can effectively control the catalytic performance of the as-prepared nanocomposites. The as-prepared Co@SiO2@C/Ni submicrorattles were employed as the reaction catalyst for the reduction of 4-nitrophenol (4-NP), and exhibit both superior catalytic activity and cycling stability to Co@SiO2 and Co–Ni@C composites.
Co-reporter:Yong Jiang, Min Wei, Jinkui Feng, Yuchen Ma and Shenglin Xiong
Energy & Environmental Science 2016 vol. 9(Issue 4) pp:1430-1438
Publication Date(Web):09 Feb 2016
DOI:10.1039/C5EE03262H
Room-temperature Na-ion batteries (NIBs) have been generally expected to offer a hopeful perspective for renewable energy storage applications on a large scale. However, a shortage of appropriate anode materials for NIBs has hindered their large-scale applications. Here, we report the strong chemical bonding of tin sulfide on amino-functionalized graphene that is prepared by a facile amine-thermal reaction. In contrast to previous reports on graphene-based composite electrodes, our strategy has the following merits: the one-step formation of amino-functionalized reduced grapheme oxide (RGO) from GO and tight contact of SnS2 nanocrystals at an amino-functionalized graphene interface. This concept has been demonstrated by experimental results which are in congruence with first principles theoretical calculations. When investigated as an anode material for NIBs, the composite maintained a capacity of 680 mA h g−1 after cycling for 100 cycles at a current density of 200 mA g−1, and 480 mA h g−1 after 1000 cycles at 1 A g−1. The outstanding performance results from the unique structure of the hybrid nanosheets.
Co-reporter:Kan Mi;Yong Jiang;Jinkui Feng;Yitai Qian
Advanced Functional Materials 2016 Volume 26( Issue 10) pp:1571-1579
Publication Date(Web):
DOI:10.1002/adfm.201504835
The proposal herein is based on an efficient sulfur host, namely hierarchical microporous–mesoporous carbonaceous nanotubes (denoted as HMMCNT) that feature a thick microporous wall and inner hollow channel. The electrochemical performance of the composite (HMMCNT-S) is studied systematically at different discharge cut-off voltages and at varying sulfur content. The cycling behavior in different voltage windows is compared and the highest specific capacity is shown for HMMCNT-S-50 in the range of 1.4–2.8 V. These results imply that better energy densities can be achieved by controlling the discharge cut-off voltage. Moreover, we show that when the sulfur loading is 50% (HMMCNT-S-50), the cycling and rate performance is better than that of the composite loaded with 40% sulfur (HMMCNT-S–40). Benefiting from the attractive hierarchical micro/mesoporous configuration, the obtained hybrid structure not only promotes electron and ion transfer during the charge/discharge process, but also efficiently impedes polysulfide dissolution. More specifically, the electrode can deliver a specific capacity of 558 mA h g-1 even after 150 cycles at a high rate of 1600 mA g-1 with a decay rate of only 0.13% per cycle. Considering the beneficial structure of these carbon nanotubes, it is very feasible that these structures may also be used in other research fields, including in catalysis, as supercapacitors, in drug-delivery applications, for absorption, and so on.
Co-reporter:Yulin Bai
The Journal of Physical Chemistry C 2016 Volume 120(Issue 5) pp:2984-2992
Publication Date(Web):January 13, 2016
DOI:10.1021/acs.jpcc.5b10222
ZnO and Co(OH)2 are significant functional materials that have been attracting immense interest in recent years because of their great potential application in various fields. Here, we developed a one-pot synthetic method to combine two materials into ZnO@α-Co(OH)2 core–shell hierarchical microspheres (CSHMSs) via the epitaxial growth of α-Co(OH)2 nanosheets on ZnO twin-hemispheres for the first time. By varying the volume ratio of N,N-dimethylformamide (DMF) to ethanol, uniform and well-defined CSHMSs were prepared. Additionally, the appropriate amount of polyvinylpyrrolidone (PVP) with certain molecular weight and the synergistic effect of different anions of precursors were found to be crucial to the formation of ZnO@α-Co(OH)2 CSHMSs. Compared with the bare ZnO twin-hemispheres, these CSHMSs indicated enhanced electrochemical activity, including high reversible capacity, excellent cycling stability, and rate performance, when examined as anodes for lithium-ion batteries. The remarkable electrochemical performance of the CSHMSs is attributed to their unique hierarchical micro/nanostructure, the synergistic effect, and the interface effect of bicomponent active materials.
Co-reporter:Fangfang Wu, Jing Bai, Jinkui Feng and Shenglin Xiong
Nanoscale 2015 vol. 7(Issue 41) pp:17211-17230
Publication Date(Web):18 Sep 2015
DOI:10.1039/C5NR04791A
The relentless pursuit of new electrode materials for lithium ion batteries (LIBs) has been conducted for decades. Structures with either porous or nanostructure configurations have been confirmed as advantageous candidates for energy storage/conversion applications. The integration of the two features into one structure can provide another chance to improve the electroactivities. Recently, single-phased mixed metal oxides (MMOs) containing different metal cations, in particular, have confirmed high electrochemical activities because of their complex chemical composition, interfacial effects, and the synergic effects of the multiple metal species. In this review, we will focus on recent research advances of MMOs with porous architectures as anode materials in the matter of structural arrangement and compositional manipulation. Moreover, the application of self-supported MMO-based porous structures as LIB anodes is also explained herein. More importantly, investigations on the synthetic system and formation mechanism of porous MMOs will be highlighted. Some future trends for the innovative design of new electrode materials are also discussed in this review. The challenges and prospects will draw many researchers' attention.
Co-reporter:Fangfang Wu, Chunhui Yu, Wenxiu Liu, Ting Wang, Jinkui Feng and Shenglin Xiong
Journal of Materials Chemistry A 2015 vol. 3(Issue 32) pp:16728-16736
Publication Date(Web):08 Jul 2015
DOI:10.1039/C5TA03106K
Micro-/nanostructured mixed transition metal oxides (MTMOs) with their unique morphologies have attracted much attention due to their potential applications such as lithium-ion batteries (LIBs). Nevertheless, in contrast to active research for the synthesis of MTMOs (AxB3−xO4 (A, B = Co, Ni, Zn, Mn, Fe)), metal vanadates seem to be an unnoticed group, possibly due to the lack of appropriate synthetic methods. In this work, for the first time, we report a structure- and size-controlled synthesis of pseudohexagonal monoclinic Co2V2O7·nH2O monodisperse hexagonal nanoplatelets (MHNPs) through a facile water bath method via a micelle-assisted assembly-Ostwald ripening process. The amount of hexamethylenetetramine in the reaction was found to be pivotal to the formation of hexagonal nanoplatelets. Additionally, the structure of MHNPs could be retained only in a certain temperature range. By calcination of Co2V2O7·nH2O in air, mesoporous Co2V2O7 MHNPs composed of numerous nanometer-sized subunits could be harvested. Benefiting from the unique structure and probably synergetic effects of different metal ions, the as-prepared Co2V2O7 MHNPs possess high specific capacity, long-term cycling stability, and good rate capability. Specifically, the Co2V2O7 MHNPs exhibit a reversible capacity as high as 866 mA h g−1 with nearly 100% capacity retention after 150 cycles, making them potential electrode materials for LIBs.
Co-reporter:Baosong Li, Jinkui Feng, Yitai Qian and Shenglin Xiong
Journal of Materials Chemistry A 2015 vol. 3(Issue 19) pp:10336-10344
Publication Date(Web):30 Mar 2015
DOI:10.1039/C5TA01229E
Mesoporous single-crystalline NiCo2O4 nanoribbons have been fabricated via a hexamethylenetetramine (HMT)-assisted hydrothermal method applied to Ni–Co precursor nanobelts, followed by annealing in an air atmosphere. The mesoporous single-crystalline feature was demonstrated by field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N2 isotherm analyses. The specific surface area and pore size distribution aspects of the porous profile of the as-obtained spinel NiCo2O4 products could be tuned feasibly by changing the post-treatment temperature of the precursors, which, hence, allowed improvements to the electrochemical performance of the as-obtained products. As expected, when applied as an anode material in lithium-ion batteries, the mesoporous single-crystalline NiCo2O4 nanoribbons delivered a high specific capacity, excellent rate capability, and outstanding cycling performance. The reversible discharge capacity could reach 1198 mA h g−1 after 60 discharge–charge cycles at a current density of 200 mA g−1. The superior electrochemical performance can be attributed to the unique structure, including the suitable pore size distribution, mesoporous single-crystalline feature, enlarged specific surface area, and highly textured nanostructure, as well as synergetic effects of the different metal ions. This synthetic strategy could be extended to synthesize other mesoporous single-crystalline functional materials.
Co-reporter:Yong Jiang, Xiaojian Ma, Jinkui Feng and Shenglin Xiong
Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:4539-4546
Publication Date(Web):06 Jan 2015
DOI:10.1039/C4TA06624C
Selenium, which is in the same group of elements as sulphur and has a higher electrical conductivity and a comparable theoretical volumetric capacity density compared to sulphur, is a prospective candidate for use in cathode materials. Herein, we propose and realise a novel strategy: using selenium in nitrogen-doped microporous carbon spheres for Li–Se batteries. As a new cathode material, the integrated composite can ensure the complete electrochemical reaction of selenium. The abundant micropores uniformly distributed in the carbon matrix and the strong adsorptive power can effectively hold the selenium, while the synergetic effect of the nitrogen heteroatoms, graphitisation, the unoccupied mesopores, and the relatively high conductivity of selenium facilitate the quick transmission of Li ions and electrons. Li–Se batteries based on this concept show excellent electrochemical performance with a high reversible capacity of 570 mA h g−1 over 350 cycles at 0.5 C, outstanding cycling stability at a rate of 2 C over 1600 cycles without capacity loss, and remarkable rate capability.
Co-reporter:Jing Bai, Kaiqi Wang, Jinkui Feng, and Shenglin Xiong
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 41) pp:22848
Publication Date(Web):October 2, 2015
DOI:10.1021/acsami.5b05303
Mastery over the structure of nanoscale materials can effectively tailor and regulate their electrochemical properties, enabling improvement in both rate capability and cycling stability. We report the shape-controlled synthesis of novel mesoporous bicomponent-active ZnO/CoO hierarchical multilayered bipyramid nanoframes (HMBNFs). The as-synthesized micro/nanocrystals look like multilayered bipyramids and consist of a series of structural units with similar frames and uniform sheet branches. The use of an appropriate straight-chain monoalcohol was observed to be critical for the formation of HMBNFs. In addition, the structure of HMBNFs could be preserved only in a limited range of the precursor ratio. An extremely fast crystal growth process and an unusual transverse crystallization of the ZnCo-carbonate HMBNFs were newly discovered and proposed. By calcination of ZnCo-carbonate HMBNFs at the atmosphere of nitrogen and air, ZnO/CoO and ZnCo2O4 HMBNFs were obtained, respectively. Compared to the ZnCo2O4 HMBNFs, the ZnO/CoO HMBNFs with a uniform distribution of nanocrystal ZnO and CoO subunits exhibited enhanced electrochemical activity, including greater rate capability and longer cycling performance, when evaluated as an anode material for Li-ion batteries. The superior electrochemical performance of the ZnO/CoO HMBNFs is attributed to the unique nanostructure, bicomponent active synergy, and uniform distribution of ZnO and CoO phases at the nanoscale.Keywords: anodes; bipyramid; lithium-ion batteries; nanoframes; synergistic effect
Co-reporter:Yanting Chu, Jinkui Feng, Yitai Qian and Shenglin Xiong
RSC Advances 2015 vol. 5(Issue 51) pp:40899-40906
Publication Date(Web):29 Apr 2015
DOI:10.1039/C5RA06711A
Co3O4 is a potential high-capacity anode material for lithium ion batteries (LIBs), but it usually has poor cycling stability due to its enormous volume variation during the conversion reaction process. A protection strategy has been developed to enhance the electrode performance of Co3O4 through construction of Co3O4@amorphous-TiO2 (Co3O4@a-TiO2) core–shell nanostructures with controllable pore size, realized by precisely regulating the volume ratio of ethanol to water. To our knowledge, this is the first time to use core–shell Co3O4@a-TiO2 as the anode material for the lithium-ion batteries. Noteworthy, electrochemical performances of the materials were found to be strongly correlated with their porous structures. With the excellent stability of TiO2 sheath, high capacity of Co3O4 core, and the optimized porous size, these unique Co3O4@a-TiO2 core–shell microcubes exhibit high capacity, long cycle life and good rate capability as advanced electrode materials for lithium-ion batteries. A high reversible capacity of ∼800 mA h g−1 is obtained at 500 mA g−1, keeping the value stable after 60 cycles. We anticipate that such a demonstration presents a versatile method toward synthesizing other high-performance and multifunctional metal oxides@a-TiO2 nanocomposites for LIBs in near future.
Co-reporter:Yurong Liu, Bochen Zhang, Jinkui Feng and Shenglin Xiong
RSC Advances 2015 vol. 5(Issue 34) pp:26863-26871
Publication Date(Web):03 Mar 2015
DOI:10.1039/C5RA03645C
In this investigation, we designed a general method to manipulate the controlled preparation of Mn-based transition metal oxide materials with the structure of hierarchical twin-microspheres. Initiated by a precursor solvothermal synthesis of metal carbonate twin-microspheres, the formation of hierarchical twin-microspheres of metal oxides was finalized by thermal annealing in laboratory air. The method allows one to prepare binary and ternary hierarchical twin-microspheres constructed by primary ultrathin nanoparticles. By applying the respective metal salts in the synthesis, six oxide species, including Mn3O4, CoMn2O4, ZnMn2O4, NixMn3−xO4, CuxMn3−xO4, and FexMn3−xO4, have been reported herein in order to draw common features via oriented-attachment. Concerning the workability, CoMn2O4 twin-microspheres are evaluated as electrode materials for lithium-ion batteries. As expected, the CoMn2O4 twin-microspheres exhibit excellent rate performance and impressive cycling stability due to their unique assembled architecture and probably synergetic effects of different metal ions.
Co-reporter:Dr. Fangfang Wu; Shenglin Xiong; Yitai Qian; Shu-Hong Yu
Angewandte Chemie International Edition 2015 Volume 54( Issue 37) pp:10787-10791
Publication Date(Web):
DOI:10.1002/anie.201503487
Abstract
Hollow structures of transition-metal oxides, particularly mixed-metal oxides, could be promising for various applications such as lithium-ion batteries (LIBs). Compared to the synthesis of metal oxide hollow spheres by the template method, non-spherical metal oxide hollow hexagonal polyhedra have not been developed to date. Herein, we report the controlled hydrothermal synthesis of a new phase of Co3V2O8⋅n H2O hollow hexagonal prismatic pencils (HHPPs), which is composed of uniform structural units. By varying the amount of NaOH in the presence of NH4+ and without any template or organic surfactant, the hexagonal prismatic pencils gradually transform from solid into hollow structures, with sizes varying from 5 to 20 μm. The structure of pencils can be preserved only in a limited range of the molar ratio of OH−/NH4+. As a new anode material for LIBs, such hollow pencils exhibit impressive lithium storage properties with high capacity, good cycling stability, and superior rate capability.
Co-reporter:Dr. Fangfang Wu; Shenglin Xiong; Yitai Qian; Shu-Hong Yu
Angewandte Chemie 2015 Volume 127( Issue 37) pp:10937-10941
Publication Date(Web):
DOI:10.1002/ange.201503487
Abstract
Hollow structures of transition-metal oxides, particularly mixed-metal oxides, could be promising for various applications such as lithium-ion batteries (LIBs). Compared to the synthesis of metal oxide hollow spheres by the template method, non-spherical metal oxide hollow hexagonal polyhedra have not been developed to date. Herein, we report the controlled hydrothermal synthesis of a new phase of Co3V2O8⋅n H2O hollow hexagonal prismatic pencils (HHPPs), which is composed of uniform structural units. By varying the amount of NaOH in the presence of NH4+ and without any template or organic surfactant, the hexagonal prismatic pencils gradually transform from solid into hollow structures, with sizes varying from 5 to 20 μm. The structure of pencils can be preserved only in a limited range of the molar ratio of OH−/NH4+. As a new anode material for LIBs, such hollow pencils exhibit impressive lithium storage properties with high capacity, good cycling stability, and superior rate capability.
Co-reporter:Jing Bai;Xiaogang Li;Guangzeng Liu;Yitai Qian
Advanced Functional Materials 2014 Volume 24( Issue 20) pp:3012-3020
Publication Date(Web):
DOI:10.1002/adfm.201303442
A facile two-step strategy involving a polyol method and subsequent thermal annealing treatment is successfully developed for the large-scale preparation of ZnCo2O4 various hierarchical micro/nanostructures (twin mcrospheres and microcubes) without surfactant assistance. To the best of our knowledge, this is the first report on the synthesis of ZnCo2O4 mesoporous twin microspheres and microcubes. More significantly, based on the effect of the reaction time on the morphology evolution of the precursor, a brand-new crystal growth mechanism, multistep splitting then in situ dissolution recrystallization accompanied by morphology and phase change, is first proposed to understand the formation of the 3D twin microshperes, providing new research opportunity for investigating the formation of novel micro/nanostructures. When evaluated as anode materials for lithium-ion batteries (LIBs), ZnCo2O4 hierarchical microstructures exhibit superior capacity retention, excellent cycling stability at the 5 A g−1 rate for 2000 cycles. Surprisingly, the ZnCo2O4 twin microspheres show an exceptionally high rate capability up to the 10 A g−1 rate. It should be noted that such super-high rate performance and cycling stability at such high charge/discharge rates are significantly higher than most work previously reported on ZnCo2O4 micro/nanostructures and ZnCo2O4-based heterostructures. The ZnCo2O4 3D hierarchical micro/nanostructures demonstrate the great potential as negative electrode materials for high-performance LIBs.
Co-reporter:Zhongchao bai, Zhicheng Ju, Chunli Guo, Yitai Qian, Bin Tang and Shenglin Xiong
Nanoscale 2014 vol. 6(Issue 6) pp:3268-3273
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3NR05676G
Hierarchically porous materials are an ideal material platform for constructing high performance Li-ion batteries (LIBs), offering great advantages such as large contact area between the electrode and the electrolyte, fast and flexible transport pathways for the electrolyte ions and the space for buffering the strain caused by repeated Li insertion/extraction. In this work, NiO microspheres with hierarchically porous structures have been synthesized via a facile thermal decomposition method by only using a simple precursor. The superstructures are composed of nanocrystals with high specific surface area, large pore volume, and broad pore size distribution. The electrochemical properties of 3D hierarchical mesoporous NiO microspheres were examined by cyclic voltammetry and galvanostatic charge–discharge studies. The results demonstrate that the as-prepared NiO nanospheres are excellent electrode materials in LIBs with high specific capacity, good retention and rate performance. The 3D hierarchical mesoporous NiO microspheres can retain a reversible capacity of 800.2 mA h g−1 after 100 cycles at a high current density of 500 mA g−1.
Co-reporter:Yurong Liu, Jing Bai, Xiaojian Ma, Jingfa Li and Shenglin Xiong
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:14236-14244
Publication Date(Web):09 Jul 2014
DOI:10.1039/C4TA02950J
At present, transition metal oxides (TMOs) have generally been fabricated via annealing carbonates pre-obtained by a precipitation/solvothermal route. We noted that researchers mainly focused on how to get the expected TMOs through calcination. However, study about the formation process of the corresponding precursors is rarely investigated. Instead, it is of much importance for the development of materials chemistry. Herein, as an example, for the first time, we devise a facile polyol-based method to synthesize the quasi-mesocrystal ZnMn2O4 porous twin-microspheres. Formation chemistry and electrochemical properties of the twin spheres have been investigated in detail. A distinctive oriented attachment accompanied by Ostwald ripening is proposed to understand the formation of the 3D carbonate twin microspheres, providing a new research opportunity for investigating the formation of novel micro/nanostructures. Benefitting from the many unique structural advantages, including quasi-mesocrystal architecture, 3D hierarchical porous microstructure, and lithium alloying reaction, the as-prepared ZnMn2O4 twin spheres represent remarkable lithium storage properties when evaluated as anode materials for lithium-ion batteries (LIBs), with high capacity, long cycle life and remarkable rate capability. The 3D porous hierarchical structures demonstrate great potential as anode materials for high-performance LIBs.
Co-reporter:Fangfang Wu, Xiaojian Ma, Jinkui Feng, Yitai Qian and Shenglin Xiong
Journal of Materials Chemistry A 2014 vol. 2(Issue 30) pp:11597-11605
Publication Date(Web):23 May 2014
DOI:10.1039/C4TA01676A
In this work, a rational hydrothermal route is designed to prepare Co(OH)F wall arrays assembled with ultrathin nanosheets on conductive nickel foam (denoted as Co(OH)F–Ni) with robust adhesion properties. Ammonium fluoride is utilized to organize single-crystalline nanosheets into wall arrays constructed from ultrathin nanosheets in this method. The morphological evolution process of this organized product has been investigated by examining different reaction intermediates in detail. A novel growth mechanism, a gradual crystallization self-assembly process via Ostwald ripening, is explored for the first time to understand the formation of wall arrays assembled with nanosheets. Subsequently, mesoporous Co3O4 wall arrays are fabricated via thermal decomposition, maintaining the original morphology of precursor Co(OH)F. Through the next step of chemical vapor deposition (CVD) in an atmosphere of acetylene, carbon has been integrated to form carbon-coated CoO wall arrays on nickel foam (denoted as CoO@C–Ni). Intriguingly, the present CVD process can also produce onion-like graphitic carbon at relatively low temperatures (300–350 °C) near the substrate because of the catalysis of nickel foam. 3D self-supported Co3O4 and CoO@C electrodes allow direct and close contact of electroactive materials and the current collector, greatly improving the system's conductivity and structural stability. Furthermore, the self-supported electrodes consist of wall arrays grown directly on current-collecting substrates, and effectively simplify the preparation process of electrodes without any requirement of other ancillary materials, such as conductive additives or binders. Each wall is fixed to the current collector, resulting in fast charge transfer. Benefitting from the unique structural features, the as-prepared cobalt oxide-based ordered hierarchically porous 3D electrodes, especially CoO@C wall arrays, manifest excellent electrochemical performance with outstanding rate capability and good cycling stability for highly reversible lithium storage.
Co-reporter:Jingfa Li, Jiazhao Wang, Xin Liang, Zhijia Zhang, Huakun Liu, Yitai Qian, and Shenglin Xiong
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 1) pp:24
Publication Date(Web):December 15, 2013
DOI:10.1021/am404841t
We present a general strategy to synthesize uniform MnCo2O4 submicrospheres with various hollow structures. By using MnCo-glycolate submicrospheres as the precursor with proper manipulation of ramping rates during the heating process, we have fabricated hollow MnCo2O4 submicrospheres with multilevel interiors, including mesoporous spheres, hollow spheres, yolk–shell spheres, shell-in-shell spheres, and yolk-in-double-shell spheres. Interestingly, when tested as anode materials in lithium ion batteries, the MnCo2O4 submicrospheres with a yolk–shell structure showed the best performance among these multilevel interior structures because these structures can not only supply a high contact area but also maintain a stable structure.Keywords: binary metal oxides; complex hollow structures; heterogeneous contraction;
Co-reporter:Jincheng Liu, Yuejiao Xu, Xiaojian Ma, Jinkui Feng, Yitai Qian, Shenglin Xiong
Nano Energy 2014 Volume 7() pp:52-62
Publication Date(Web):July 2014
DOI:10.1016/j.nanoen.2014.04.013
•CoO@C metasequoia arrays on Ni foam have been prepared for the first time.•The graphitic carbon can be produced at only 300–350 °C near the nickel foam substrate.•As anode materials for LIBs, the composite exhibited high reversible capacity, excellent cycling and rate capability.Cobalt oxide is a promising high-capacity anode material for lithium ion batteries (LIBs), but its development is limited by poor cycling stability due to its huge volume change happening during repeated conversion processes. In this paper, a robust and rational strategy was designed to improve the electrochemical performance of cobalt oxide (CoO) by preparing self-supported CoO@C core–shell metasequoia-like nanowire arrays on a conducting nickel foam substrate with solid adhesion. Interestingly, the present CVD process can produce onion-like graphitic carbon at a relatively low temperature (300–350 °C) near the substrate due to the catalysis of nickel foam. More importantly, the direct and compact contact of cobalt oxide with the thin carbon layer and the conducting substrate provided an effective pathway for fast charge transfer and ion transport without any requirement of other ancillary materials, such as carbon black or binder, to improve the system׳s conductivity and stability. As an anode material for LIBs, the heterocomposite exhibited a larger reversible capacity, higher rate capability, and excellent cycling stability by comparison with the pristine CoO@C and Co3O4 on nickel foam due to the triple electronically conductive guarantee of carbon shells, conducting nickel foam substrate and the oriented orderly CoO nanowire arrays. The preparation of the orderly 1D nanostructures with conductive coating on conductive substrates has been proven to generate efficient electrode materials, opening up an alternate way to improve the electrochemical stability of LIBs. The present route is expected to be extended to the synthesis of other oxides as electrodes for LIBs.CoO@C metasequoia arrays on Ni foam (CoO@C–Ni) heterocomposites have been successfully prepared for the first time based on rational design and elaborate analysis. As an anode material for LIBs, the heterocomposite exhibited high reversible capacity, excellent cycling and rate capability.
Co-reporter:Jingfa Li, Jiazhao Wang, David Wexler, Dongqi Shi, Jianwen Liang, Huakun Liu, Shenglin Xiong and Yitai Qian
Journal of Materials Chemistry A 2013 vol. 1(Issue 48) pp:15292-15299
Publication Date(Web):23 Oct 2013
DOI:10.1039/C3TA13787B
Mixed metal oxides have been attracting more and more attention recently because of their advantages and superiorities, which can improve the electrochemical performance of single metal oxides. These advantages include structural stability, good electronic conductivity, and reversible capacity. In this work, uniform yolk-shelled ZnCo2O4 microspheres were synthesized by pyrolysis of ZnCo-glycolate microsphere precursors which were prepared via a simple refluxing route without any precipitant or surfactant. The formation process of the yolk-shelled microsphere structure during the thermal decomposition of ZnCo-glycolate is discussed, which is mainly based on the heterogeneous contraction caused by non-equilibrium heat treatment. The performances of the as-prepared ZnCo2O4 electrodes using sodium carboxylmethyl cellulose (CMC) and poly-vinylidene fluoride (PVDF) as binders are also compared. Constant current and rate charge–discharge testing results demonstrated that the ZnCo2O4 electrodes using CMC as the binder had better performance than those using PVDF as the binder. It was worth pointing out that the electrode using CMC as the binder nicely yields a discharge capacity of 331 mA h g−1 after 500 cycles at a current density of 1000 mA g−1, which is close to the theoretical value of graphite (371 mA h g−1). Furthermore, the obtained synthetic insights on the complex hollow structures will be of benefit to the design of other anode materials for lithium ion batteries.
Co-reporter:Zhongchao Bai, Na Fan, Zhicheng Ju, Chunli Guo, Yitai Qian, Bin Tang and Shenglin Xiong
Journal of Materials Chemistry A 2013 vol. 1(Issue 36) pp:10985-10990
Publication Date(Web):19 Jul 2013
DOI:10.1039/C3TA11910F
Because of the low cost and operating potential, Mn3O4 is highly noticeable among transition metal oxides as an anode material for Li-ion batteries. Here, mesoporous Mn3O4 nanotubes with a high surface area of 42.18 m2 g−1 and an average pore size of 3.72 nm were synthesized for the first time through the hydrogen reduction of β-MnO2 nanotubes under a H2/Ar atmosphere at 280 °C for 3 h. Electrochemical results demonstrate that the reversible capacity of mesoporous Mn3O4 nanotubes is 641 mA h g−1 (much higher than the theoretical capacity of graphite, ∼372 mA h g−1) after 100 cycles at a high current density of 500 mA g−1. The superior electrochemical performance can be attributed to the unique 1D mesoporous nano-tubular structure, which offers fast and flexible transport pathways for electrolyte ions, and also provides sufficient free space to buffer the large volume change of anodes based on the conversion reaction during the repeated lithium-ion insertion/extraction. The improved electrochemical performance makes such a mesoporous Mn3O4 tubular structure promising as an anode material for next-generation lithium-ion batteries.
Co-reporter:Jingfa Li, Shenglin Xiong, Xiaowei Li and Yitai Qian
Nanoscale 2013 vol. 5(Issue 5) pp:2045-2054
Publication Date(Web):01 Feb 2013
DOI:10.1039/C2NR33576J
A facile and general way for the synthesis of porous and hollow complex oxides is highly desirable owing to their significant applications for energy storage and other fields. In this contribution, uniform Mn0.33Co0.67CO3 and Co0.33Mn0.67CO3 microspheres are firstly fabricated solvothermally just by tuning the molar ratio of Mn and Co. Subsequently, the growth of multiporous MnCo2O4 and CoMn2O4 quasi-hollow microspheres by topotactic chemical transformation from the corresponding precursors are realized through a non-equilibrium heat treatment process. Topotactic conversion further demonstrated that the much larger CoMn2O4 pores than those of MnCo2O4 are possibly due to the longer transfer distance of ions. When evaluated as anode materials for LIBs (lithium ion batteries), after 25 cycles at a current density of 200 mA g−1, the resultant MnCo2O4 and CoMn2O4 quasi-hollow microspheres possessed reversible capacities of 755 and 706 mA h g−1, respectively. In particular, the MnCo2O4 samples could deliver a reversible capacity as high as 610 mA h g−1 even at a higher current density of 400 mA g−1 with excellent electrochemical stability after 100 cycles of testing, indicating its potential application in LIBs. We believe that such good performance results from the appropriate pore size and quasi-hollow nature of MnCo2O4 microspheres, which can effectively buffer the large volume variation of anodes based on the conversion reaction during Li+ insertion/extraction. The present strategy is simple but very effective, and due to its versatility, it can be extended to other binary, even ternary complex metal oxides with high-performance in LIBs.
Co-reporter:Jingfa Li, Shenglin Xiong, Yurong Liu, Zhicheng Ju, and Yitai Qian
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 3) pp:981
Publication Date(Web):January 16, 2013
DOI:10.1021/am3026294
Binary metal oxides have been regarded as ideal and potential anode materials, which can ameliorate and offset the electrochemical performance of the single metal oxides, such as reversible capacity, structural stability and electronic conductivity. In this work, monodisperse NiCo2O4 mesoporous microspheres are fabricated by a facile solvothermal method followed by pyrolysis of the Ni0.33Co0.67CO3 precursor. The Brunauer–Emmett–Teller (BET) surface area of NiCo2O4 mesoporous microspheres is determined to be about 40.58 m2 g–1 with dominant pore diameter of 14.5 nm and narrow size distribution of 10–20 nm. Our as-prepared NiCo2O4 products were evaluated as the anode material for the lithium-ion-battery (LIB) application. It is demonstrated that the special structural features of the NiCo2O4 microspheres including uniformity of the surface texture, the integrity and porosity exert significant effect on the electrochemical performances. The discharge capacity of NiCo2O4 microspheres could reach 1198 mA h g–1 after 30 discharge–charge cycles at a current density of 200 mA g–1. More importantly, when the current density increased to 800 mA·g–1, it can render reversible capacity of 705 mA h g–1 even after 500 cycles, indicating its potential applications for next-generation high power lithium ion batteries (LIBs). The superior battery performance is mainly attributed to the unique micro/nanostructure composed of interconnected NiCo2O4 nanocrystals, which provides good electrolyte diffusion and large electrode–electrolyte contact area, and meanwhile reduces volume change during charge/discharge process. The strategy is simple but very effective, and because of its versatility, it could be extended to other high-capacity metal oxide anode materials for LIBs.Keywords: complex metal oxides; lithium-ion battery; mesoporous structures; spinel structure;
Co-reporter:Jingfa Li, Shenglin Xiong, Yurong Liu, Zhicheng Ju, Yitai Qian
Nano Energy 2013 Volume 2(Issue 6) pp:1249-1260
Publication Date(Web):November 2013
DOI:10.1016/j.nanoen.2013.06.003
•Uniform LiNi1/3Co1/3Mn1/3O2 hollow microspheres were synthesized for the first time.•Topotactical transformation from Mn1.5Co1.5O4 to LiNi1/3Co1/3Mn1/3O2 was discussed.•LiNi1/3Co1/3Mn1/3O2 hollow microspheres showed excellent electrochemical performance.In this work, we designed a facile in-situ template-sacrificial route to prepare LiNi1/3Co1/3Mn1/3O2 hollow microspheres with an average diameter of 2.0 μm for the first time through using porous spinel Mn1.5Co1.5O4 hollow microspheres as the template, the formation of which could originate from a synergic effect of the contraction and adhesion action generated during the oxidative decomposition of the Mn0.5Co0.5CO3 precursors. The walls of the as-prepared hollow microspheres are ~300 nm in thickness, and composed of numerous primary particles with size of hundreds of nanometers. The as-synthesized nanocrystal-assembled hollow structure showed singnificantly enhanced electrochemical performance with high capacity, excellent cycling stability and good rate capability, compared with the bulk counterparts, when used as a cathode material for Li ion batteries (LIBs), which can be attributed to the unique nano/micro hierarchical structure. Specifically, the resulting LiNi1/3Co1/3Mn1/3O2 hollow microspheres achieve a high discharge capacity of 157.3 mAh g−1 at 0.2 C after 100 cycles and 120.5 mAh g−1 at 0.5 C after 200 cycles with an excellent cycle life. Interestingly, it exhibits a high rate capacity of 114.2 mAh g−1 even at a current of 1 A g−1 (5 C). On the basis of this work, the pesent preparation strategy could provide an effective and general approach to improve the cyclability and rate capability of high-capacity cathode materials with hollow interiors for the application of LIBs.
Co-reporter:Xiaowei Li;Jingfa Li;Xin Liang;Jiazhao Wang;Jing Bai;Yitai Qian
Chemistry - A European Journal 2013 Volume 19( Issue 34) pp:11310-11319
Publication Date(Web):
DOI:10.1002/chem.201203553
Abstract
A facile method is presented for the large-scale preparation of rationally designed mesocrystalline MnO@carbon core–shell nanowires with a jointed appearance. The nanostructures have a unique arrangement of internally encapsulated highly oriented and interconnected MnO nanorods and graphitized carbon layers forming an external coating. Based on a comparison and analysis of the crystal structures of MnOOH, Mn2O3, and MnO@C, we propose a sequential topotactic transformation of the corresponding precursors to the products. Very interestingly, the individual mesoporous single-crystalline MnO nanorods are strongly interconnected and maintain the same crystallographic orientation, which is a typical feature of mesocrystals. When tested for their applicability to Li-ion batteries (LIB), the MnO@carbon core–shell nanowires showed excellent capacity retention, superior cycling performance, and high rate capability. Specifically, the MnO@carbon core–shell nanostructures could deliver reversible capacities as high as 801 mA h g−1 at a high current density of 500 mA g−1, with excellent electrochemical stability after testing over 200 cycles, indicating their potential application in LIBs. The remarkable electrochemical performance can mainly be attributed to the highly uniform carbon layer around the MnO nanowires, which is not only effective in buffering the structural strain and volume variations of anodes during repeated electrochemical reactions, but also greatly enhances the conductivity of the electrode material. Our results confirm the feasibility of using these rationally designed composite materials for practical applications. The present strategy is simple but very effective, and appears to be sufficiently versatile to be extended to other high-capacity electrode materials with large volume variations and low electrical conductivities.
Co-reporter:Changzhou Yuan;Long Yang;Linrui Hou;Jiaoyang Li;Yaxin Sun;Xiaogang Zhang;Laifa Shen;Xiangjun Lu;Xiong Wen (David) Lou
Advanced Functional Materials 2012 Volume 22( Issue 12) pp:2560-2566
Publication Date(Web):
DOI:10.1002/adfm.201102860
Abstract
A facile one-step hydrothermal method is developed for large-scale production of well-designed flexible and free-standing Co3O4/reduced graphene oxide (rGO)/carbon nanotubes (CNTs) hybrid paper as an electrode for electrochemical capacitors. Densely packed unique Co3O4 monolayer microsphere arrays uniformly cover the surface of the rGO/CNTs film. The alkaline hydrothermal treatment leads to not only the deposition of Co3O4 microspheres array, but also the reduction of the GO sheets at the same time. The unique hybrid paper is evaluated as an electrode for electrochemical capacitors without any ancillary materials. It is found that the obtained hybrid flexible paper, composed of Co3O4 microsphere array anchored to the underling conductive rGO/CNTs substrate with robust adhesion, is able to deliver high specific capacitance with excellent electrochemical stability even at high current densities, suggesting its promising application as an efficient electrode material for electrochemical capacitors.
Co-reporter:Jingfa Li, Shenglin Xiong, Xiaowei Li and Yitai Qian
Journal of Materials Chemistry A 2012 vol. 22(Issue 43) pp:23254-23259
Publication Date(Web):17 Sep 2012
DOI:10.1039/C2JM35607D
Transition metal oxides are important functional materials that have gained enormous research interest in recent years. In this work, porous cubic manganese cobalt spinel Mn1.5Co1.5O4 core–shell microspheres were first prepared via a urea-assisted solvothermal route followed by pyrolysis of the carbonate precursor. The microsphere is composed of the shell of 400 nm thickness and the core with a 2.5 μm diameter. Nitrogen sorption isotherms show that this structure possesses a high surface area of 27.0 m2 g−1 with an average pore diameter of 30 nm. Compared with a simple spherical nanopowder, such a core–shell like porous structure is expected to improve the electrochemical performance, due to its higher resistance against separation or isolation during the electrochemical reaction. The as-prepared Mn1.5Co1.5O4 core–shell microspheres show an excellent cyclic performance at high current density with more than 90% capacity retention in a testing range of 300 cycles when used as an anode material for lithium ion batteries (LIBs), which can be attributed to the appropriate pore size and unique core–shell structures. Therefore, the Mn1.5Co1.5O4 core–shell microspheres prepared by the present synthetic route could be identified as a potential anode candidate for the near future development of LIBs.
Co-reporter:Xiaowei Li, Shenglin Xiong, Jingfa Li, Jing Bai and Yitai Qian
Journal of Materials Chemistry A 2012 vol. 22(Issue 28) pp:14276-14283
Publication Date(Web):21 May 2012
DOI:10.1039/C2JM32559D
Low-cost controlled strategies for the synthesis of mesoporous nickel oxide materials are highly desirable owing to its significant applications for power storage and other fields. In this contribution, we develop a novel hydrothermal route to synthesize α-Ni(OH)2, in which urea has not only been utilized to produce hydroxyl anions, but also to organize ultrathin nanowires/nanosheets into a network-like hierarchical assemblage. The morphological evolution process of this organized product has been investigated by examining different reaction intermediates during the synthesis. The growth and thus final assemblage of α-Ni(OH)2 can be finely tuned by selecting preparative parameters such as the molar ratio of starting chemicals. Based on the topotactic transformation from α-Ni(OH)2, various mesoporous NiO hierarchical microspheres from ultrathin nanowires/nanosheets self-assembly have been prepared via thermal decomposition in an air atmosphere. The electrochemical performances of the typical nickel oxide products are evaluated. It is demonstrated that tuning of the surface texture and the pore size of the NiO products is very significant for electrochemical capacitor and water treatment applications. The mesoporous NiO network-like hierarchical microspheres exhibit excellent cyclic performance with nearly 100% capacity retention at a current density of 10 A g−1 in a testing range of 2000 cycles. Moreover, the mesoporous NiO network-like hierarchical microspheres have excellent ability to remove organic pollutants from wastewater by their wonderful surface adsorption ability.
Co-reporter:Man Huang, Kan Mi, Junhao Zhang, Huili Liu, Tingting Yu, Aihua Yuan, Qinghong Kong and Shenglin Xiong
Journal of Materials Chemistry A 2017 - vol. 5(Issue 1) pp:NaN274-274
Publication Date(Web):2016/11/14
DOI:10.1039/C6TA09030C
To tackle the issue of the low specific capacity (372 mA h g−1) of graphite as the anode material for lithium-ion batteries (LIBs), an effective and controllable strategy was developed to construct porous bimetallic Co/Zn embedded N-doped carbon (Co–Zn/N–C) polyhedral nanocages via annealing a ZIF-8@ZIF-67 precursor at 800 °C under Ar atmosphere. The results clearly displayed that metallic Co and Zn particles are uniformly dispersed in the carbon matrix. Porous Co–Zn/N–C polyhedral nanocages have a large specific surface area of 349.12 m2 g−1 and contain plenty of micropores and mesopores, which benefit from the carbonization of organic ligands and the catalytic effect of cobalt in the calcination process. As anodes for LIBs, the porous Co–Zn/N–C polyhedral nanocages showed an initial discharge capacity of 809 mA h g−1 and a capacity retention of 702 mA h g−1 after 400 cycles at a current density of 0.2 A g−1. Furthermore, a reversible capacity of 444 mA h g−1 was obtained at a much higher current density of 2 A g−1. The improved electrochemical performance was attributed to the synergistic effect of Zn and Co, the unique porous hollow structure as well as N doping, which relieved the impact of volume changes, maintained perfect electrical conductivity throughout the electrode and enhanced the electrochemical activities of lithium storage.
Co-reporter:Yong Jiang, Xiaojian Ma, Jinkui Feng and Shenglin Xiong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 8) pp:NaN4546-4546
Publication Date(Web):2015/01/06
DOI:10.1039/C4TA06624C
Selenium, which is in the same group of elements as sulphur and has a higher electrical conductivity and a comparable theoretical volumetric capacity density compared to sulphur, is a prospective candidate for use in cathode materials. Herein, we propose and realise a novel strategy: using selenium in nitrogen-doped microporous carbon spheres for Li–Se batteries. As a new cathode material, the integrated composite can ensure the complete electrochemical reaction of selenium. The abundant micropores uniformly distributed in the carbon matrix and the strong adsorptive power can effectively hold the selenium, while the synergetic effect of the nitrogen heteroatoms, graphitisation, the unoccupied mesopores, and the relatively high conductivity of selenium facilitate the quick transmission of Li ions and electrons. Li–Se batteries based on this concept show excellent electrochemical performance with a high reversible capacity of 570 mA h g−1 over 350 cycles at 0.5 C, outstanding cycling stability at a rate of 2 C over 1600 cycles without capacity loss, and remarkable rate capability.
Co-reporter:Baosong Li, Jinkui Feng, Yitai Qian and Shenglin Xiong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 19) pp:NaN10344-10344
Publication Date(Web):2015/03/30
DOI:10.1039/C5TA01229E
Mesoporous single-crystalline NiCo2O4 nanoribbons have been fabricated via a hexamethylenetetramine (HMT)-assisted hydrothermal method applied to Ni–Co precursor nanobelts, followed by annealing in an air atmosphere. The mesoporous single-crystalline feature was demonstrated by field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N2 isotherm analyses. The specific surface area and pore size distribution aspects of the porous profile of the as-obtained spinel NiCo2O4 products could be tuned feasibly by changing the post-treatment temperature of the precursors, which, hence, allowed improvements to the electrochemical performance of the as-obtained products. As expected, when applied as an anode material in lithium-ion batteries, the mesoporous single-crystalline NiCo2O4 nanoribbons delivered a high specific capacity, excellent rate capability, and outstanding cycling performance. The reversible discharge capacity could reach 1198 mA h g−1 after 60 discharge–charge cycles at a current density of 200 mA g−1. The superior electrochemical performance can be attributed to the unique structure, including the suitable pore size distribution, mesoporous single-crystalline feature, enlarged specific surface area, and highly textured nanostructure, as well as synergetic effects of the different metal ions. This synthetic strategy could be extended to synthesize other mesoporous single-crystalline functional materials.
Co-reporter:Xiaowei Li, Shenglin Xiong, Jingfa Li, Jing Bai and Yitai Qian
Journal of Materials Chemistry A 2012 - vol. 22(Issue 28) pp:NaN14283-14283
Publication Date(Web):2012/05/21
DOI:10.1039/C2JM32559D
Low-cost controlled strategies for the synthesis of mesoporous nickel oxide materials are highly desirable owing to its significant applications for power storage and other fields. In this contribution, we develop a novel hydrothermal route to synthesize α-Ni(OH)2, in which urea has not only been utilized to produce hydroxyl anions, but also to organize ultrathin nanowires/nanosheets into a network-like hierarchical assemblage. The morphological evolution process of this organized product has been investigated by examining different reaction intermediates during the synthesis. The growth and thus final assemblage of α-Ni(OH)2 can be finely tuned by selecting preparative parameters such as the molar ratio of starting chemicals. Based on the topotactic transformation from α-Ni(OH)2, various mesoporous NiO hierarchical microspheres from ultrathin nanowires/nanosheets self-assembly have been prepared via thermal decomposition in an air atmosphere. The electrochemical performances of the typical nickel oxide products are evaluated. It is demonstrated that tuning of the surface texture and the pore size of the NiO products is very significant for electrochemical capacitor and water treatment applications. The mesoporous NiO network-like hierarchical microspheres exhibit excellent cyclic performance with nearly 100% capacity retention at a current density of 10 A g−1 in a testing range of 2000 cycles. Moreover, the mesoporous NiO network-like hierarchical microspheres have excellent ability to remove organic pollutants from wastewater by their wonderful surface adsorption ability.
Co-reporter:Jingfa Li, Shenglin Xiong, Xiaowei Li and Yitai Qian
Journal of Materials Chemistry A 2012 - vol. 22(Issue 43) pp:NaN23259-23259
Publication Date(Web):2012/09/17
DOI:10.1039/C2JM35607D
Transition metal oxides are important functional materials that have gained enormous research interest in recent years. In this work, porous cubic manganese cobalt spinel Mn1.5Co1.5O4 core–shell microspheres were first prepared via a urea-assisted solvothermal route followed by pyrolysis of the carbonate precursor. The microsphere is composed of the shell of 400 nm thickness and the core with a 2.5 μm diameter. Nitrogen sorption isotherms show that this structure possesses a high surface area of 27.0 m2 g−1 with an average pore diameter of 30 nm. Compared with a simple spherical nanopowder, such a core–shell like porous structure is expected to improve the electrochemical performance, due to its higher resistance against separation or isolation during the electrochemical reaction. The as-prepared Mn1.5Co1.5O4 core–shell microspheres show an excellent cyclic performance at high current density with more than 90% capacity retention in a testing range of 300 cycles when used as an anode material for lithium ion batteries (LIBs), which can be attributed to the appropriate pore size and unique core–shell structures. Therefore, the Mn1.5Co1.5O4 core–shell microspheres prepared by the present synthetic route could be identified as a potential anode candidate for the near future development of LIBs.
Co-reporter:Jingfa Li, Jiazhao Wang, David Wexler, Dongqi Shi, Jianwen Liang, Huakun Liu, Shenglin Xiong and Yitai Qian
Journal of Materials Chemistry A 2013 - vol. 1(Issue 48) pp:NaN15299-15299
Publication Date(Web):2013/10/23
DOI:10.1039/C3TA13787B
Mixed metal oxides have been attracting more and more attention recently because of their advantages and superiorities, which can improve the electrochemical performance of single metal oxides. These advantages include structural stability, good electronic conductivity, and reversible capacity. In this work, uniform yolk-shelled ZnCo2O4 microspheres were synthesized by pyrolysis of ZnCo-glycolate microsphere precursors which were prepared via a simple refluxing route without any precipitant or surfactant. The formation process of the yolk-shelled microsphere structure during the thermal decomposition of ZnCo-glycolate is discussed, which is mainly based on the heterogeneous contraction caused by non-equilibrium heat treatment. The performances of the as-prepared ZnCo2O4 electrodes using sodium carboxylmethyl cellulose (CMC) and poly-vinylidene fluoride (PVDF) as binders are also compared. Constant current and rate charge–discharge testing results demonstrated that the ZnCo2O4 electrodes using CMC as the binder had better performance than those using PVDF as the binder. It was worth pointing out that the electrode using CMC as the binder nicely yields a discharge capacity of 331 mA h g−1 after 500 cycles at a current density of 1000 mA g−1, which is close to the theoretical value of graphite (371 mA h g−1). Furthermore, the obtained synthetic insights on the complex hollow structures will be of benefit to the design of other anode materials for lithium ion batteries.
Co-reporter:Zhongchao Bai, Na Fan, Zhicheng Ju, Chunli Guo, Yitai Qian, Bin Tang and Shenglin Xiong
Journal of Materials Chemistry A 2013 - vol. 1(Issue 36) pp:NaN10990-10990
Publication Date(Web):2013/07/19
DOI:10.1039/C3TA11910F
Because of the low cost and operating potential, Mn3O4 is highly noticeable among transition metal oxides as an anode material for Li-ion batteries. Here, mesoporous Mn3O4 nanotubes with a high surface area of 42.18 m2 g−1 and an average pore size of 3.72 nm were synthesized for the first time through the hydrogen reduction of β-MnO2 nanotubes under a H2/Ar atmosphere at 280 °C for 3 h. Electrochemical results demonstrate that the reversible capacity of mesoporous Mn3O4 nanotubes is 641 mA h g−1 (much higher than the theoretical capacity of graphite, ∼372 mA h g−1) after 100 cycles at a high current density of 500 mA g−1. The superior electrochemical performance can be attributed to the unique 1D mesoporous nano-tubular structure, which offers fast and flexible transport pathways for electrolyte ions, and also provides sufficient free space to buffer the large volume change of anodes based on the conversion reaction during the repeated lithium-ion insertion/extraction. The improved electrochemical performance makes such a mesoporous Mn3O4 tubular structure promising as an anode material for next-generation lithium-ion batteries.
Co-reporter:Fangfang Wu, Xiaojian Ma, Jinkui Feng, Yitai Qian and Shenglin Xiong
Journal of Materials Chemistry A 2014 - vol. 2(Issue 30) pp:NaN11605-11605
Publication Date(Web):2014/05/23
DOI:10.1039/C4TA01676A
In this work, a rational hydrothermal route is designed to prepare Co(OH)F wall arrays assembled with ultrathin nanosheets on conductive nickel foam (denoted as Co(OH)F–Ni) with robust adhesion properties. Ammonium fluoride is utilized to organize single-crystalline nanosheets into wall arrays constructed from ultrathin nanosheets in this method. The morphological evolution process of this organized product has been investigated by examining different reaction intermediates in detail. A novel growth mechanism, a gradual crystallization self-assembly process via Ostwald ripening, is explored for the first time to understand the formation of wall arrays assembled with nanosheets. Subsequently, mesoporous Co3O4 wall arrays are fabricated via thermal decomposition, maintaining the original morphology of precursor Co(OH)F. Through the next step of chemical vapor deposition (CVD) in an atmosphere of acetylene, carbon has been integrated to form carbon-coated CoO wall arrays on nickel foam (denoted as CoO@C–Ni). Intriguingly, the present CVD process can also produce onion-like graphitic carbon at relatively low temperatures (300–350 °C) near the substrate because of the catalysis of nickel foam. 3D self-supported Co3O4 and CoO@C electrodes allow direct and close contact of electroactive materials and the current collector, greatly improving the system's conductivity and structural stability. Furthermore, the self-supported electrodes consist of wall arrays grown directly on current-collecting substrates, and effectively simplify the preparation process of electrodes without any requirement of other ancillary materials, such as conductive additives or binders. Each wall is fixed to the current collector, resulting in fast charge transfer. Benefitting from the unique structural features, the as-prepared cobalt oxide-based ordered hierarchically porous 3D electrodes, especially CoO@C wall arrays, manifest excellent electrochemical performance with outstanding rate capability and good cycling stability for highly reversible lithium storage.
Co-reporter:Yurong Liu, Jing Bai, Xiaojian Ma, Jingfa Li and Shenglin Xiong
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN14244-14244
Publication Date(Web):2014/07/09
DOI:10.1039/C4TA02950J
At present, transition metal oxides (TMOs) have generally been fabricated via annealing carbonates pre-obtained by a precipitation/solvothermal route. We noted that researchers mainly focused on how to get the expected TMOs through calcination. However, study about the formation process of the corresponding precursors is rarely investigated. Instead, it is of much importance for the development of materials chemistry. Herein, as an example, for the first time, we devise a facile polyol-based method to synthesize the quasi-mesocrystal ZnMn2O4 porous twin-microspheres. Formation chemistry and electrochemical properties of the twin spheres have been investigated in detail. A distinctive oriented attachment accompanied by Ostwald ripening is proposed to understand the formation of the 3D carbonate twin microspheres, providing a new research opportunity for investigating the formation of novel micro/nanostructures. Benefitting from the many unique structural advantages, including quasi-mesocrystal architecture, 3D hierarchical porous microstructure, and lithium alloying reaction, the as-prepared ZnMn2O4 twin spheres represent remarkable lithium storage properties when evaluated as anode materials for lithium-ion batteries (LIBs), with high capacity, long cycle life and remarkable rate capability. The 3D porous hierarchical structures demonstrate great potential as anode materials for high-performance LIBs.
Co-reporter:Fangfang Wu, Chunhui Yu, Wenxiu Liu, Ting Wang, Jinkui Feng and Shenglin Xiong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 32) pp:NaN16736-16736
Publication Date(Web):2015/07/08
DOI:10.1039/C5TA03106K
Micro-/nanostructured mixed transition metal oxides (MTMOs) with their unique morphologies have attracted much attention due to their potential applications such as lithium-ion batteries (LIBs). Nevertheless, in contrast to active research for the synthesis of MTMOs (AxB3−xO4 (A, B = Co, Ni, Zn, Mn, Fe)), metal vanadates seem to be an unnoticed group, possibly due to the lack of appropriate synthetic methods. In this work, for the first time, we report a structure- and size-controlled synthesis of pseudohexagonal monoclinic Co2V2O7·nH2O monodisperse hexagonal nanoplatelets (MHNPs) through a facile water bath method via a micelle-assisted assembly-Ostwald ripening process. The amount of hexamethylenetetramine in the reaction was found to be pivotal to the formation of hexagonal nanoplatelets. Additionally, the structure of MHNPs could be retained only in a certain temperature range. By calcination of Co2V2O7·nH2O in air, mesoporous Co2V2O7 MHNPs composed of numerous nanometer-sized subunits could be harvested. Benefiting from the unique structure and probably synergetic effects of different metal ions, the as-prepared Co2V2O7 MHNPs possess high specific capacity, long-term cycling stability, and good rate capability. Specifically, the Co2V2O7 MHNPs exhibit a reversible capacity as high as 866 mA h g−1 with nearly 100% capacity retention after 150 cycles, making them potential electrode materials for LIBs.
