A high-capacity Si anode is always accompanied by very large volume expansion and structural collapse during the lithium-ion insertion/extraction process. To stabilize the structure of the Si anode, magnesium vapor thermal reduction has been used to synthesize porous Si and SiO2 (pSS) particles, followed by in situ growth of carbon nanotubes (CNTs) in pSS pores through a chemical vapor deposition (CVD) process. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy have shown that the final product (pSS/CNTs) possesses adequate void space intertwined by uniformly distributed CNTs and inactive silica in particle form. pSS/CNTs with such an elaborate structural design deliver improved electrochemical performance, with better coulombic efficiency (70% at the first cycle), cycling capability (1200 mAh g–1 at 0.5 A g–1 after 200 cycles), and rate capability (1984, 1654, 1385, 1072, and 800 mAh g–1 at current densities of 0.1, 0.2, 0.5, 1, and 2 A g–1, respectively), compared to pSS and porous Si/CNTs. These merits of pSS/CNTs are attributed to the capability of void space to absorb the volume changes and that of the silica to confine the excessive lithiation expansion of the Si anode. In addition, CNTs have interwound the particles, leading to significant enhancement of electronic conductivity before and after Si-anode pulverization. This simple and scalable strategy makes it easy to expand the application to manufacturing other alloy anode materials.Keywords: carbon nanotubes; chemical vapor deposition; lithium-ion battery; magnesium vapor thermal reduction; silicon anode;

The severe capacity fading of LiMn2O4 at elevated temperature hinders its wide application in lithium ion batteries despite several advantages over present cathode materials in terms of cost, rate capability, and environmental benignity. In this study, porous nanosized TiO2-coated LiMn2O4 is prepared via a modified sol–gel process of controlling hydrolysis and condensation of titanium tetrabutoxide in ethanol/ammonia mixtures, and the phenomenon of homogeneous nucleation has been almost entirely avoided. The X-ray diffraction patterns and transmission electron microscopy images show that a porous nanosized TiO2 layer is uniformly coated on the surface of spinel LiMn2O4. Electrochemical tests reveal that the optimal coating content is 3 wt % which shows remarkably improved capacity retentions at both room temperature of 25 °C and elevated temperature of 55 °C. Even after long-term charge and discharge cycles, the TiO2 layer is still robust enough to prevent LiMn2O4 particles from the attack of electrolyte. The inductively coupled plasma-atomic emission spectrometry, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy results indicate that the obvious improvement of TiO2-coated LiMn2O4 electrodes is attributed to the suppression of Mn dissolution, as well as the enhancement of kinetics of Li+ diffusion.Keywords: Cathode material; Improved electrochemical performance; Lithium ion battery; Lithium manganese oxide; Surface modification;

Although dimethylsulfoxide (DMSO) solvent has been widely researched in rechargeable lithium-oxygen (Li-O2) batteries, high polarization voltage and low rate capability limited its application. In this work, we reported a DMSO-based electrolyte system by adding N, N-dimethylacetamide (DMA) to adjust its physical and electrochemical properties. The ionic conductivity, viscosity, oxygen solubility and diffusion coefficient of the mixed electrolytes as well as their electrochemical performance in Li-O2 batteries are researched. The electrochemical tests show that the optimized DMSO/DMA volume ratio is 30 to 70 based on the rate performance and polarization voltage of the cell. Compared with that of the pure DMSO-based electrolyte, the cell with the mixed electrolyte shows improved rate capability and reduced charge-discharge over-potential. When increasing current density from 0.2 to 0.5 mA cm−2, the capability retention improves from 32% to 59%. Meanwhile, the charge-discharge voltage gap drops from 1.4V to 0.9V at a current density of 0.2 mA cm−2. The improved electrochemical performance could be attributed to low viscosity, high oxygen solubility and diffusion coefficient as well as the low charge-transfer resistance with the mixed electrolyte.

Li-ion batteries have played a key role in the portable electronics and electrification of transport in modern society. Nevertheless, the limited highest energy density of Li-ion batteries is not sufficient for the long-term needs of society. Since lithium is the lightest metal among all metallic elements and possesses the lowest redox potential of −3.04 V vs. standard hydrogen electrode, it delivers the highest theoretical specific capacity of 3860 mA h g−1 and a high working voltage of full batteries which causes a great interest in electrochemical energy storage systems. Lithium-sulfur, lithium-oxygen and corresponding all solid state batteries based on metal lithium anode have received widely attention owing to their high energy densities. However, the problems in the cathode, electrolyte and anode of these three systems restrict their practical application. In this review, the research status and problems of these three energy storage systems are summarized and the challenges and future perspectives are also outlined.

•An amorphous lithium ion conductor layer was successfully deposited on LiNi0.6Co0.2Mn0.2O2 surface.•The concentration of lithium residues on LiNi0.6Co0.2Mn0.2O2 surface was reduced.•1 mol% LLTO modified LiNi0.6Co0.2Mn0.2O2 exhibits excellent electrochemical performance.•LLTO coating layer alleviates structure degradation and suppresses interfacial resistance increasing.A novel surface modification strategy that could convert lithium residues on the Ni-rich material surface into a lithium ion conductor coating layer was investigated. Various analysis techniques, such as high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS), were used to confirm the formation of an amorphous lithium lanthanum titanate (LLTO) coating layer with a thickness below 10 nm. 1 mol% LLTO modified LiNi0.6Co0.2Mn0.2O2 exhibits the optimized electrochemical performance, with 87.2% capacity retention after 200 cycles at 0.5C, and excellent rate performance compared with that of the pristine LiNi0.6Co0.2Mn0.2O2. The cycling performance at higher charging voltage (4.5 V) and storage characteristics against moisture and air are also improved significantly after LLTO modification. The enhanced electrochemical performance could be attributed to the high ionic conductivity of LLTO and the uniformity of the coating layer. It can not only suppress the interfacial resistance increasing, but also stabilize the crystal structure of the cathode material during charge-discharge cycling.

•Hierarchical porous NiCo2O4 hollow spheres as catalysts for Li-O2 batteries•The NiCo2O4 could boost oxidation kinetics by control the nature of Li2O2.•The NiCo2O4 hollow spheres significantly reduced the charge over-potential.•The catalysts enable the Li-O2 cells extendedly fully cycle over 50 cycles.Hollow NiCo2O4 microspheres with a highly hierarchical porous structure were synthesized and conducted as catalysts for lithium-oxygen batteries. The influence of NiCo2O4 on the discharge products was investigated. The NiCo2O4 showed the capability to promote the formation of lithium deficient Li2 − xO2 and exerted a significant influence on the electrochemical performance of lithium-oxygen batteries with a low charge overpotential and extended full cycling over 50 cycles.Download high-res image (260KB)Download full-size image

In this study, Zn–Fe–O@C hollow microspheres are prepared by chemical vapor deposition (CVD) method with ZnFe2O4 hollow microspheres as precursors which are synthesized via a facile solvothermal method. ZnFe2O4 hollow microspheres and Zn–Fe–O@C hollow microspheres are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The physical analysis shows a fraction of Fe(III) reduced to Fe(II) and the hollow microspheres maintained during the CVD process. Zn–Fe–O@C hollow microspheres can deliver a reversible specific capacity of 1035.6 mA h g−1 after 50 cycles at a current density of 100 mA g−1, and maintain a stable capacity as high as 1000 mA h g−1 at 500 mA g−1 after 200 cycles. Compared with ZnFe2O4 hollow microspheres, Zn–Fe–O@C hollow microspheres present excellent rate performance. The better electrochemical performances of the Zn–Fe–O@C hollow microspheres should be ascribed to the carbon coating, which can elevate electrical conductivity and improve the structural stability of the active materials.

The electrochemical performance of lithium–oxygen (Li–O2) batteries depends largely on the architecture and catalytic effectiveness of the oxygen cathode. Herein, in this study, a graphene aerogel decorated with MoSx nanosheets (MoSx/HRG) with a three-dimensional porous framework synthesized using a one-step hydrothermal reaction followed by freeze-drying is reported. The MoSx/HRG aerogel possesses hierarchical mesopores and micropores, which could facilitate electrolyte impregnation and oxygen diffusion, and provide much more accommodation space for the reaction products. The lithium–oxygen batteries based on this MoSx/HRG aerogel cathode show improved electrochemical performance, with a high initial discharge capacity up to 6678.4 mA h g−1 at a current density of 0.05 mA cm−2 and better cycling capability with a cut-off capacity of 500 mA h g−1 at a current density of 0.1 mA cm−2, compared with the lithium–oxygen batteries based on an HRG aerogel cathode. The enhanced performance is ascribed to the excellent catalytic activity of the MoSx nanosheets and the unique three-dimensional porous architecture.

•Nano-sized Li4Ti5O12 with B-doped carbon coating layer is prepared.•Effect of B-dopant amount on electrochemical performance is investigated.•A moderate B-dopant amount much improves rate performance.•BC3 dopant species are important for improving electronic conductivity of carbon.•B-O dopant species might hamper the charge transfer.A facile method was developed to synthesize B-doped carbon coated nano-sized Li4Ti5O12 by using glucose and boric acid mixture as the precursor of coating layer, and the effect of B-dopant amounts on electrochemical performance was investigated in detail. It is demonstrated that B-dopant can efficiently improve the electronic conductivity of carbon-coating layer. According to X-ray photoemission spectroscopy analysis and electrochemical investigation, it is also found that, BC3 dopant species are important for improving electronic conductivity and electrochemical performance, whereas the B-O dopant species, which increases with the enhancement of B-dopant amount, might hamper the charge transfer on Li+-insertion process. Therefore, the carbon coated nano-sized Li4Ti5O12 with a moderate B-dopant amount exhibits much higher electrochemical performance. For example, with a low carbon content of ∼3 wt. %, the optimized B-doped carbon coated Li4Ti5O12 can deliver a capacity of around 90 mAh g−1 at a high rate of 20C, which is much higher than that of carbon-coated Li4Ti5O12. The achieved result indicates that approach of B-doped carbon coating is an effective method for improving the performance of Li4Ti5O12.

With the aim to enhance the Li+ ion conductivity, an ionic conductor, LiVO3, has been successfully coated on the surface of lithium-rich layered Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials for the first time. After combining with LiVO3, significantly improved high-rate capability and cyclic stability of the Li-rich cathode have been achieved due to the enhanced lithium ion diffusion and stabilized electrode/electrolyte interface. Moreover, a stable three-dimensional spinel phase has been generated in the surface region during the coating process, which mitigates the structure deterioration and suppresses the voltage decay and energy density degradation. After optimization, 5 wt % LiVO3-coated–Li1.2Mn0.54Ni0.13Co0.13O2 exhibits superior electrochemical performance with a higher reversible capacity of 272 mA h g–1, increased initial Coulombic efficiency of 92.6%, and an excellent high-rate capability of 135 mA h g–1 at 5 C, respectively. The coexistence of an ionic conductor coating layer and the locally transformed spinel structure generated in a one-step approach provides a novel design concept for surface modification on Li-rich Mn-based cathode materials toward high-performance lithium-ion batteries.Keywords: Lithium-ion battery; Lithium-rich cathode material; Phase transformation; Surface modification

Mo4O11 nanoparticles were decorated onto ultralight graphene sheets (HRG) to form a Mo4O11/HRG precursor. Sulfur was then homogeneously dispersed onto the surface of Mo4O11/HRG by self-assembly from a sulfur/carbon disulfide solution to obtain a Mo4O11–HRG/S composite, which was used as the cathode material for a lithium sulfur battery. The morphologies and microstructures of the as-synthesized composites were characterized by electron microscopy and X-ray diffraction/photoelectron spectroscopy. Mo4O11 nanoparticles not only have a strong ability to adsorb to lithium polysulfides but also lead to a high Coulombic efficiency (96%). Furthermore, the incorporation of Mo4O11 on graphene improves the utilization of sulfur and enhances the cycling stability and rate capability of a Li–S battery.Keywords: adsorption ability; cathode materials; lithium−sulfur batteries; Mo4O11 nanoparticles; ultralight graphene

•Pd-based catalysts with complicated exposed facets.•Much enhanced electrocatalytic activity and stability with about 10% noble metal M (M = Ru, Pt, Au) on Pd nanoparticles.•The outstanding electrocatalytic performance of PdAu/C towards ethanol oxidation after the Au modification.In this article, we studied the surface noble metal modification on Pd nanoparticles, other than the homogeneous or core-shell structure. The surface modification will lead to the uneven constitution within the nanoparticles and thus more obvious optimization effect toward the catalyst brought by the lattice deformation. The surface of the as-prepared Pd nanoparticles was modified with Ru, Pt or Au by a moderate and green approach, respectively. XPS results confirm the interactive electron effects between Pd and the modified noble metal. Electrochemical measurements show that the surface noble metal modified catalysts not only show higher catalytic activity, but also better stability and durability. The PdM/C catalysts all exhibit good dispersion and very little agglomeration after long-term potential cycles toward ethanol oxidation. With only 10% metallic atomic ratio of Au, PdAu/C catalyst shows extraordinary catalytic activity and stability, the peak current reaches 1700 mA mg−1 Pd, about 2.5 times that of Pd/C. Moreover, the PdAu/C maintains 40% of the catalytic activity after 4500 potential cycles.

PUVGCF/S microspheres have been prepared using high-heat treatment with partially unzipped vapor-grown carbon fibers (PUVGCF) as the carbon precursor. The PUVGCF structure is formed via peeling and further lengthwise cutting with highly graphitized vapor-grown carbon fibers (VGCF) using a simple solution-based oxidative process. The composites of PUVGCF/S wrapped with polyaniline (PANi) are synthesized via an in situ oxidative polymerization of aniline using a liquid process. The microsphere structure not only shortens the electron and ion transport pathway but also provides mechanical support to accommodate volume expansion during the discharge/charge process. Additionally, the PANi coating layer further enhances conductivity of the electrode and prevents the polysulfides from dissolving in the electrolyte. Electrochemical measurements demonstrate excellent performance.

•Surface Cu removal for CuPdAu/C via chronoamperometric method.•Enhanced electrocatalytic activity and stability due to the surface Cu removal.•Durable catalysis of HCOOH/HCOO− oxidation for CuPdAu/C in both acidic and alkaline media.In this article we innovatively propose a new surface modification strategy which applies a chronoamperometry on CuPdAu/C to get the surface copper removed CuAuPd/C (SCR-CuAuPd/C). Moreover, the chronoamperometric process can also modify the surface constitution with oxides such as PdO2 and Au2O3. The removal of surface Cu will diminish the drawbacks brought by the instability of surface Cu in alkaline media, and the oxides like PdO2 will help oxidize COad and thus reduce catalyst poisoning. The electrochemical measurements confirm the positive effect of chronoamperometric treatment, the SCR-CuPdAu/C achieve objective progress after chronoamperometric treatment, with highest activity and anti-poisoning properties toward formic acid/formate oxidation in both acidic and alkaline media.

•The samples show nanowire morphology and strong interaction with carbon.•CCH/C-based cathode shows reduced overpotential and greater specific capacity.•The cell with CCH/C catalyst shffigows much prolonged cycle life.Cobalt carbonate hydroxide (CCH) composited with XC-72R carbon was synthesized via a simple hydrothermal process. Transmission electron microscopes(TEM) shows that CCH with nanowire morphology is well dispersed in carbon medium. The CCH/C-based oxygen cathode exhibited low polarization with specific capacity of 3500 mA h g−1 at a current density of 0.05 mA cm−2 and prolonged cycling life. The cell with CCH/C catalyst can run for 55 cycles before the terminal potential of discharge declines to 2.0 V with a limited specific capacity of 500 mA h g−1. The improved performance was mainly attributed to the excellent OER activity of CCH/C that Li2O2 can be decomposed in lower potential, which might help avoid generation of undesirable byproducts.

•Swelling behavior of LTO/LMO battery stored at elevated temperature is observed.•Swelling degree of LTO/LMO battery are observed at different SOC.•The differences of SEI layer compositions based on EC and PC solvents are discussed.•The reaction mechanisms of LTO electrode with electrolyte solvents are proposed.Gassing behavior of LiMn2O4/Li4Ti5O12 full cell with different electrolytes that stored at elevated temperature of 70 °C is investigated. Scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) are used to study the solid electrolyte interphase (SEI) layer formed in battery formation and storage processes. The results suggest that the SEI film is formed as a consequence of intrinsic reaction between Li4Ti5O12 electrode and electrolyte solvents. A smooth SEI layer is formed on Li4Ti5O12 electrode with full coverage in propylene carbonate (PC) based electrolyte during lithium intercalation process while gradually dissolved with lithium extraction. Moreover, the gas specificities generated in the different electrolyte solvents are also determined by gas chromatography–mass spectrometer (GC–MS) analysis and the reaction mechanisms of LTO electrode with electrolyte solvents are proposed.

A carbon-free, three-dimensional network structured material composed of NiCo2O4 nanowires and Ni foam was synthesized by a facile method. When applied as the air electrode for the lithium–oxygen battery, the unique network structure enables the surface of nanowires highly accessible to the reactants and facilities the electron transport during the charge/discharge processes. A superior electrochemical performance including low charge overpotential and excellent cyclability are obtained. This work suggests the great potential of the carbon-free NiCo2O4@Ni as the air electrodes for lithium–oxygen batteries.

Rechargeable lithium–oxygen batteries have attracted extensive attention for their high energy density. However, the carbon corrosion, the undesired electrolyte decomposition catalyzed by carbon, and the irreversible reaction between carbon and the discharge product Li2O2 limit their performance. Herein we show the synthesis of sea-urchin-like cobalt oxide growing directly on nickel foam by a facile method, exhibiting several features. First, the open structure facilitates electrolyte penetration and the ion/electron transfer. Furthermore, the macrosized voids built up by the 1D nanorods provide sufficient buffer space for Li2O2 deposition without blocking O2 diffusion. As a result, the battery displays high performance, including a high specific capacity of ∼3000 mAh g–1 based on the weight of the whole electrode and long-life (∼1800 h, 60 cycles at a fixed capacity of 500 mAh g–1).Keywords: Carbon-free; Lithium−oxygen batteries; Sea-urchin-like cobalt oxide;

In this study, nano-TiO2(B) coated LiMn2O4 was prepared via a two-step method, combining a hydrothermal method with electrostatic attraction. By adjusting the sintering time, porous and dense nano-TiO2(B) coating structure were formed on the surface of LiMn2O4 particles. Electrochemical test results showed that 2 wt.% porous TiO2(B) coated LiMn2O4 exhibited highest capacity retention at 77.4% after 300 cycles at 55 °C and the best rate capability. Inductively coupled plasma spectroscopy(ICP), charge and discharge curves and electrochemical impedance spectroscopy (EIS) results revealed that the improved electrochemical performances was due to the suppression of the undesired SEI film, as well as suppression of Mn dissolution at the cathode and reduced polarization.

•Li1.2Mn0.54Ni0.13Co0.13O2 is pre-activated by different amounts of Na2S2O8.•40 wt% Na2S2O8-treated sample shows the best electrochemical properties.•Appropriate Na2S2O8-treatment alleviates the structure conversion upon cycling.•Subsequent CaF2 coating further stabilizes the interface structure.To overcome the voltage decay upon cycling and increase the initial coulombic efficiency of the layered Li-rich Mn-based oxides, the double modification combining Na2S2O8 treatment with CaF2 coating has been first proposed in this study. The precondition Na2S2O8 treatment activates the Li2MnO3 phase gently and generates a stabilized three-dimensional spinel structure on the surface of particles, leading to a suppression of surface reaction and structure conversion during the subsequent electrochemical process. The mitigation of phase transformation for Na2S2O8-treated Li1.2Mn0.54Ni0.13Co0.13O2 alleviates the voltage decay and energy density degradation upon long-term charge-discharge cycling. In order to further restrain the capacity loss derived from the HF attack and manganese dissolution, 40 wt% Na2S2O8 treated-sample has been modified by an amorphous CaF2 layer with nano-scale thickness. The first-reported CaF2-coated/40 wt% Na2S2O8 treated-Li1.2Mn0.54Ni0.13Co0.13O2 presents excellent electrochemical properties with a high initial coulombic efficiency of 99.2%, a capacity retention rate of 89.2% after 200 cycles and a high-rate capability of 152.1 mAh g−1 at 3 C. The double surface modification offers a smart design concept for Li-rich Mn-based oxides to meet the practical requirements for advanced lithium ion batteries in electric vehicles.

The exploration for post-carbon electrode materials for lithium-ion batteries has been a crucial way to satisfy the ever-growing demands for better performance with higher energy/power densities, enhanced safety, and longer cycle life. Transition metal oxides have recently received a great deal of attention as very promising anode materials due to their high theoretical capacity, good safety, eco-benignity, and huge abundance. The present work reviews the latest advances in developing novel transition metal oxides, including Fe2O3, Fe3O4, Co3O4, CoO, NiO, MnO, Mn2O3, Mn3O4, MnO2, MoO3, Cr2O3, Nb2O5, and some binary oxides such as NiCo2O4, ZnCo2O4, MnCo2O4 and CoMn2O4. Nanostructuring and hybrid strategies applicable to transition metal oxides are summarized and analyzed. Furthermore, the impacts of binder choice and heat treatment on electrochemical performance are discussed.为了满足锂离子电池的更高能量/功率密度、更长循环寿命、更好安全性能的发展需求,对于碳负极以外的新型负极材料的探索越来越重要。其中,过渡金属氧化物由于具有较高的理论比容量、较好的安全性能、储量丰富和对环境友好等优点而有望成为新一代高能量锂离子电池负极材料。本综述探讨了包括Fe2O3,Fe3O4,Co3O4,CoO,NiO,MnO,Mn2O3,Mn3O4,MnO2,MoO3,Cr2O3和Nb2O5在内的过渡金属氧化物及一些二元氧化物,如NiCo2O4,ZnCo2O4,MnCo2O4和CoMn2O4的最新研究进展。对改善过渡金属氧化物电化学性能的纳米化及合成复合材料的方法进行了总结和分析。同时,关于黏结剂的选择及热处理手段对电化学性能的影响也进行了讨论及研究。

In this study, phenyl sulfonated graphene/sulfur (PhSO3-RG/S) composites were synthesized for the first time via an in situ redox reaction in aqueous solution. These composites were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetry (TG). The results show that sulfur was thoroughly enveloped by functionalized water-soluble phenyl sulfonated graphene, providing a conductive coating for electron transport and functional groups that interact strongly with polysulfides or sulfur to improve trapping. In our study, we found that large amounts of conductive carbon additives and binders were not required when the electrodes were prepared on carbon-coated aluminum foil substrates because phenyl sulfonated graphene has excellent electrical conductivity, and contains functional groups that interact strongly with carbon and sulfur. The electrochemical tests show that the binder-free PhSO3-RG/S electrodes have high reversible capacity, good cycling stability at the current density of 0.2 C, and excellent rate capability.

A carbon-free, three-dimensional network structured material composed of (Co, Mn)3O4 nanowires and Ni foam was synthesized. Without the addition of any binder or conductive additives, it could be employed as the air electrode for lithium–oxygen batteries and delivers a specific capacity of 3605 mA h gelectrode−1 at a current density of 0.05 mA cm−2. Fifty cycles of continuous discharge and charge have been obtained with a cut-off capacity of 500 mA h gelectrode−1. The high reversibility and large capacity of the batteries is largely attributed to the unique features of the as-prepared (Co, Mn)3O4@Ni electrode, which enables the surface of nanowires to become highly accessible to the reactants and provides more void volume for the deposition of discharge products. This work suggests that there is great potential in employing the carbon-free (Co, Mn)3O4@Ni as air electrodes for lithium–oxygen batteries.

In this study, three-dimensional flower-shaped activated porous carbon/sulfur composites (FA-PC/S) are fabricated for the first time via a simple method utilizing flower-shaped ZnO as a template and pitch as the carbon precursor, followed by carbonization activation and thermal treatment. The composites are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, Raman spectroscopy, X-ray powder diffraction (XRD), and thermogravimetric (TG) measurements. The results show that sulfur is well dispersed and encapsulated homogeneously in the micropores of the flower-shaped activated porous carbon (FA-PC) with excellent electrical conductivity, high surface area, and large pore volume. The electrochemical tests show that the FA-PC/S composites with 60 wt % S have a high initial discharge capacity of 1388 mA h g–1 at 100 mA g–1, good cycling stability (reversible discharging capacity of approximately 600 mA h g–1 at 1600 mA g–1), and excellent rate capability.Keywords: Cathode material; Flower-shaped activated porous carbon; Lithium−sulfur cell; Micropores;

Nitrogen-doped porous carbon nanofiber webs-sulfur composites (N-CNFWs/S) were synthesized for the first time with sulfur (S) encapsulated into nitrogen-doped porous carbon nanofiber webs (N-CNFWs) via a modified oxidative template route, carbonization-activation and thermal treatment. The composites were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD), and thermogravimetry (TG) measurements. The results show that sulfur is well dispersed and immobilized homogeneously in the micropores of nitrogen-doped porous carbon nanofiber webs (N-CNFWs) with high electrical conductivity, surface area and large pore volume. The electrochemical tests show that the N-CNFWs/S composites with 60 wt. % of S have a high initial discharge capacity of 1564 mA h g−1, a good cycling stability at the current density of 175 mA g−1, and excellent rate capability (reversible discharging capacity of above 400 mA h g−1 at 1600 mA g−1).

•Two step sol–gel method to synthesize nano-sized LiMn0.6Fe0.4PO4/C composite.•The composite shows good discharge capacity as well as cycling ability.•Aging test reveals lower surface reactivity of the particles.Fe-substituted lithium manganese phosphate (LiMn0.6Fe0.4PO4/C), with a small particle size of 50 nm in diameter, is successfully prepared using a two-step sol–gel method. TEM analysis reveals that LiMn0.6Fe0.4PO4 particles are embedded in a porous carbon matrix, and carbon interconnected particles to form a secondary spherical-like morphology. The composite prepared in this study exhibits excellent electrochemical behavior in terms of specific capacities and rate cycling ability. Furthermore, the XPS spectral studies before and after aging test reflect the much lower surface reactivity of the LiMn0.6Fe0.4PO4/C towards 1.5 M LiPF6 solutions. And the results also reveal the good stability of electrolyte/carbon interface.

Here we prepare the CuPt/PUVGCF catalyst made of surface platinum-rich CuPt nanoparticles anchored on partially unzipped vapor grown carbon fibers (PUVGCFs) as an anode catalyst for fuel cells. Longitudinal unzipping of vapor grown carbon fibers (VGCFs) can result in a combination structure of one-dimensional VGCF and two-dimensional graphene, inheriting good solubility and dispersity from VGCFs and large surface area from graphene, thus a more integrated combination with CuPt nanoparticles. Electrochemical measurements show the CuPt/PUVGCF catalyst has superior catalytic activity and stability for methanol and ethanol electrooxidation compared to that of CuPt/VGCF, which may be a consequence of the mutual effects of the CuPt bimetallic interaction and the excellent properties of PUVGCFs.

Molybdenum-doped titanium dioxide obtained using a facile hydrothermal process delivers a high reversible capacity of 408 mA h g–1 at 60 mA g–1 after 200 cycles, which is more than twice of that of undoped TiO2. In addition, this material also exhibits a better rate capability. Structural and surface analyses indicate that doping with Mo6+ has significant effects on the transformation of brookite to anatase and on the electronic structure, thereby improving the electrical conductivity. Remarkably, Mo6+ doping also induces a substantial decrease in particle size and lattice distortion, which greatly ameliorates the lithium diffusion and enhances the interfacial lithium storage. In combination with the extra lithium storage capacity through the conversion reaction of Mo6+ with Li+, the electrochemical performance of molybdenum-doped titanium dioxide dramatically improves.

Carbon coated TiO2–SiO2 nanocomposites (CTSO) with high grain boundary density fabricated by a simple hydrothermal approach have been investigated as anode materials for lithium-ion batteries. The CTSO anode exhibits superior high-rate capability and excellent cycling performance. The specific capacity of CTSO is much higher than that of pure TiO2 and silica-modified TiO2 without carbon nanocoating (TSO), indicating a positive synergistic effect of the material and structural hybridization on the enhancement of the electrochemical properties. The possible contributing factors include the formation of the Ti–O–Si bonding, which facilitates the reaction between SiO2 and Li; the presence of carbon layering on each nanocrystal; high grain boundary density among the nanoparticles and grain boundary interface areas embedded in a carbon matrix, where electronic and ionic transport properties are tuned by interfacial design and by varying the spacing of interfaces down to the nanoscale regime. The grain boundary interface embedded in the carbon matrix can also store electrolyte and allows more channels for the insertion/extraction reaction of Li ions. The composites exhibit strong potential as a promising anode for lithium-ion batteries.

In this work, hierarchically porous honeycomb-like carbon (HCC) was prepared and used in the fabrication of the air electrode for lithium–oxygen batteries. The HCC-based electrode was found to yield an obviously higher specific capacity of 3233 mA h g−1 without the addition of catalysts and an improved cycle efficiency with a higher discharge voltage plateau (2.75 V vs. 2.50 V) than conventional carbon. The enhanced performance is largely ascribed to its unique porous structure, which consists of large tunnels for oxygen diffusion into the inner electrode and nanosized pores, which serve as reactive sites for oxygen reduction reactions and provide more room for accumulation of deposits. Furthermore, HCC samples with different pore sizes of 400 and 100 nm were investigated in lithium–oxygen batteries. There is a significant relationship between the discharge performance and the diameter.

Nano-sized lithium manganese phosphate (LiMnPO4) is successfully prepared using a mild solvothermal method in ethylene glycol solvent. The particle size, observed by Scanning Electron Microscopy (SEM), is approximately 100 nm using C6H5COOLi as the starting material. Further TEM characterization reveals that the decomposition of benzoyloxy in this lithium salt leads to a favorable configuration, with LiMnPO4 particles embedded in carbon and a distinct in situ carbon layer formed even on partial particles. Using subsequent heat-treatment with a certain amount of sucrose, LiMnPO4/C composites that display a good two-phase plateau during the discharge process can be formed, with a specific capacity over 130 mAh g−1 at 0.1 C.Highlights► Nano-sized LiMnPO4 was synthesized via mild solvothermal method. ► A favorable configuration with LiMnPO4 particles embedded in carbon was formed. ► The composite displayed a specific capacity of over 130 mAh g−1 at 0.1 C. ► The lithium diffusion constants were estimated by EIS measurements.

•A novel material of TiO2 nanowire array/Si composite has been fabricated.•TiO2 nanowire framework separates Si bulk apart and accommodates Si volume expansion.•Mass ratio of Si to TiO2 is tuned to achieve the best electrochemical performance.•Composite with 75% Si owns the highest capacity of 802.3 mA h g−1 after 200 cycles.A novel material of Si/TiO2 nanowire array (TNA) composite has been designed and fabricated, to be used as anode material for lithium ion batteries. Firstly, Self-assembled and well-aligned rutile TiO2 nanowire arrays are synthesized on pretreated titanium substrate by solvothermal route. Subsequently, Si film is introduced into the interspace of the nanowires, forming a Si/TNA composite. The field-emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM) images indicate that the dimension of TiO2 nanowires is 10 ± 2 nm wide. The TEM and Raman results reveal that Si contains amorphous and nanocrystalline phases. The composite with 75% Si content owns the best electrochemical performance, the first charge capacity reaches as high as 1480 mA h g−1, and remains at 802.3 mA h g−1 after 200 cycles.

A novel material of Sn/TiO2 nanowire array (TNA) composite has been designed and fabricated to be used as anode material for lithium-ion batteries. Firstly, highly ordered, vertically oriented rutile TiO2 nanowire array is synthesized directly on titanium substrate by solvothermal procedure without any template. Subsequently, tin metal is chemically deposited into the interspace of the film, forming a TNA/Sn composite. By calcinations in atmosphere, the skin-deep Sn is oxidized to SnO2, and further turns to Li2O in Li-ion insertion process. The field-emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM) images indicate that the dimensions of TiO2 nanowires and Sn particles are 10 ± 2 nm and 8 ± 1 nm wide, respectively. The energy-dispersive X-ray spectroscopy (EDX) result reveals that the weight ratio of tin to TiO2 is 0.22. The first charge capacity reaches as high as 1610 mA h cm−3, and the capacity retention is 62.3% after 300 cycles.Highlights► A novel material of TiO2 nanowire array/Sn composite has been fabricated. ► The TNA–Li2O framework ensures excellent cycling stability of the composites. ► Tin component brings high capacity and outstanding rate capability.

A novel lysine-assisted hydrothermal process is first developed to produce hierarchically porous Fe2O3 microspheres assembled by well-crystalline nanoparticles. The fabrication process is very simple, without employing any surfactants or templates. A possible growth mechanism of the nano/microspherical superstructure is further discussed. The contribution of lysine to the formation of the unique microspheres is also tentatively proposed. Furthermore, as an anode electrode material for rechargeable lithium-ion batteries, the Fe2O3 microsphere displays excellent electrochemical performance. It also exhibits the feature of capacity increase upon cycling and shows a stable and reversible capacity of 705 mA h g−1 after 430 cycles. The outstanding electrochemical performance of the Fe2O3 microsphere can be attributed to the hierarchical porosity, ordered microstructure, good electron pathways and easy penetration of the electrolyte.Highlights► Fe2O3 microspheres were prepared by a simple, template-free hydrothermal method. ► Hierarchical porous Fe2O3 microspheres are assembled by uniform nanoparticles. ► Lysine acts as a hydrolysis-controlling agent. ► The Fe2O3 microspheres have a high capacity of 705 mA h g−1 at 430th cycle.

•Porous Pd and Pd–Ni catalysts are prepared using hydrogen bubble dynamic template.•The catalysts have 3D hierarchical pores and interconnected dendrite walls.•The porous catalysts show good catalytic performance towards methanol oxidation.•The enhancement can be ascribed to the porous structure and the Ni doping effect.Pd and Pd–Ni catalysts with three-dimensional hierarchical pores consisting of interconnected dendrite walls are successfully fabricated by cathodic deposition using hydrogen dynamic bubble template. The as-prepared catalysts are characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, element analysis mapping, X-ray photoelectron spectroscopy and typical electrochemical measurements. It is found that the porous structure enlarges the electro-active surface area; the Ni doping modifies the electronic structure of the catalysts and improves their stability. Thus the porous catalysts exhibit excellent catalytic activity and stability towards methanol oxidation.

The surface of LiMn2O4 was coated with a nano-layer of FePO4 by the co-precipitation method followed by heat treatment at different temperatures in air. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the FePO4 coatings remained in the amorphous phase from 300 °C to 400 °C, whereas crystalline FePO4 was obtained above 500 °C. In addition, the diffusion of Fe ions into the LiMn2O4 lattice was promoted at higher temperatures. The results of the cycle capacity test showed that 3 wt% FePO4-coated LiMn2O4 heat treated at 400 °C exhibited optimum cyclability, with cycle retention of 90.3% after 100 cycles at elevated temperature (55 °C). The electrochemical impedance spectroscopy (EIS) results indicated that 3 wt%–400 °C FePO4-coated LiMn2O4 showed the lowest charge transfer resistance (Rct) value and the highest diffusion coefficient of the lithium ion of 9.85E−10 cm2 s−1. These results indicated that heat treatment at the proper temperature could maintain FePO4 in the amorphous phase, thereby facilitating Li ion transport and prevent the detachment of FePO4 and LiMn2O4, which was caused by the diffusion of Fe ions into LiMn2O4 lattice.

Li-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by a sol–gel method and coated with CaF2 layer via a wet chemical process. The pristine and CaF2-coated samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). An amorphous nanolayer coating of CaF2 is obtained on the surface of layered pristine material. The CaF2-coated Li1.2Mn0.54Ni0.13Co0.13O2 material exhibits excellent electrochemical performance. The initial coulombic efficiency is enhanced to 89.6% with high initial discharge capacity of 277.3 mAh g−1 after CaF2 coating. Galvanostatic charge–discharge tests at 0.2 C display faster activation of Li2MnO3 phase and higher capacity retention of 91.2% after 80 cycles for CaF2-coated material. Meanwhile it also shows higher rate capability with the capacity of 141.5 mAh g−1 at the 3 C-rate and stable cyclic performance above 190 mAh g−1 after 100 cycles at the 1 C-rate. The analysis of dQ/dV plots and electrochemical impedance spectroscopy (EIS) indicates that the obvious improvement of CaF2 coating is mainly attributed to the accelerated phase transformation from layered phase to spinel phase and stable electrolyte/electrode interfacial structure due to the suppression of the electrolyte decomposition.

Here we prepared Cu@Pt core–shell nanoparticles (NPs) anchored on the reduced graphene oxide (rGO) via a sequential wet chemical process. The morphologies and structures of the as-prepared catalysts were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD) and ultraviolet–visible (UV) absorption spectrum. The electrochemical measurements show that the Cu@Pt/rGO catalysts have superior catalytic activity and stability for methanol electrooxidation compared to Cu@Pt/Vulcan XC-72(XC-72) with the same Pt content, which may be a consequence of mutual effect of the Cu@Pt core–shell NPs and rGO support.

This work introduces an effective, inexpensive, and large-scale production approach to the synthesis of Fe2O3 nanoparticles with a favorable configuration that 5 nm iron oxide domains in diameter assembled into a mesoporous network. The phase structure, morphology, and pore nature were characterized systematically. When used as anode materials for lithium-ion batteries, the mesoporous Fe2O3 nanoparticles exhibit excellent cycling performance (1009 mA h g− 1 at 100 mA g− 1 up to 230 cycles) and rate capability (reversible charging capacity of 420 mA h g− 1 at 1000 mA g− 1 during 230 cycles). This research suggests that the mesoporous Fe2O3 nanoparticles could be suitable as a high rate performance anode material for lithium-ion batteries.Highlights► The extremely simple method only uses Fe(NO3)3·9H2O and H2O as starting materials. ► Fe2O3 nanoparticles with a diameter of 5 nm are assembled into a porous network. ► The Fe2O3 nanoparticles have a high capacity of 1009 mA h g− 1 at 230th cycle.

Pd–MoOx catalysts supported on glassy carbon electrode were co-deposited using cyclic voltammetry. The influence of two key deposition parameters (i.e. scanning potential range and concentration of sodium molybdate in the electrolyte) on the catalysts was investigated by X-ray diffraction, energy dispersive X-ray spectroscopy, element analysis mapping, scanning electron microscopy, X-ray photoelectron spectroscopy and typical electrochemical measurements, respectively. It was found both of the parameters had great effect on the morphology, chemical states, composition and electrochemical performance of the catalysts. By tuning the electrodeposition parameters, we found the optimal condition to prepare the catalysts. The as-prepared catalysts showed much improved catalytic activity and stability for formic acid electrooxidation. The enhanced performance can be attributed to the fine porous structure composed of small particles, hydrogen spillover effect and unique element distribution (different composition between surface and bulk).

Highly conductive polyaniline (PANI) membranes synthesized by a proton doping method are used as waterproof barriers for lithium air batteries. When the membrane is attached to the air cathode, it promotes lithium ion transport into the electrode and blocks the moisture entrance, which can protect the lithium anode from erosion. Electrolyte evaporation from the battery is also greatly reduced. Electrochemical tests show that lithium air cells with this design deliver a much higher specific capacity, 3241 mAh g−1 (referring to carbon), under high relative humidity (RH > 20%) conditions; the cells also have an excellent rate capability.

Unique hollow Fe3O4 spheres are prepared by a simple template-free solvothermal reaction. In the reaction, ethylene glycol (EG) and polyvinylpyrrolidone (PVP) serve as the reducing agent and surface stabilizer, respectively. NH4Ac plays the role of the structure-directing agent, which combines with the Ostwald ripening process, resulting in the favored formation of hollow structures. The morphologies and structures are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The hollow Fe3O4 spheres exhibit excellent cycling and rate performance as anode material for lithium-ion batteries, delivering reversible specific capacities of 870 mA h g−1 even after 50 cycles at 100 mA g−1 and 836 mA h g−1 at 500 mA g−1. The excellent electrochemical performance can be attributed to their hollow nanostructure and excellent structural stability.Graphical abstractUnique hollow Fe3O4 spheres assembled by Fe3O4 nanoparticles prepared by a simple template-free solvothermal reaction are tested as anode material for lithium-ion batteries. The results show that the material delivers reversible specific capacities of 870 mA h g−1 even after 50 cycles at 100 mA g−1 and 836 mA h g−1 at 500 mA g−1. The excellent electrochemical performance can be attributed to their hollow nanostructure and excellent structural stability.Highlights► Uniform hollow Fe3O4 spheres were prepared by a template-free solvothermal method. ► The hollow Fe3O4 spheres have the capacity of 870 mA h g−1 at 50th cycle. ► The specific capacity can be well maintained at a large current density. ► The hollow Fe3O4 spheres exhibit enhanced rate capability. ► Electrochemical performance of hollow Fe3O4 spheres is better than Fe3O4 powders.

Nano-sized La0.8Sr0.2MnO3 prepared by the polyethylene glycol assisting sol–gel method was applied as oxygen reduction catalyst in nonaqueous Li/O2 batteries. The as-synthesized La0.8Sr0.2MnO3 was characterized by X-ray diffraction (XRD), scanning electron microscopy, and Brunauer–Emmet–Teller measurements. The XRD results indicate that the sample possesses a pure perovskite-type crystal structure, even sintered at a temperature as low as 600 °C, whereas for solid-state reaction method it can only be synthesized above 1,200 °C. The as-prepared nano-sized La0.8Sr0.2MnO3 has a specific surface area of 32 m2 g−1, which is much larger than the solid-state one (1 m2 g−1), and smaller particle size of about 100 nm. Electrochemical results show that the nano-sized La0.8Sr0.2MnO3 has better catalytic activity for oxygen reduction, higher discharge plateau and specific capacity.

Cu6Sn5-coated TiO2 nanotube arrays, a novel design for an anode material in lithium ion batteries, were prepared by electroless plating techniques. In this design, a Cu6Sn5 layer was coated on to the inner wall surface of TiO2 nanotubes. The hollow structure of the nanotubes was still retained, although the inner diameter of the nanotubes decreased from 100 nm to 50 nm. The as-prepared Cu6Sn5-coated TiO2 nanotube arrays combine the merits of the high specific capacity of tin and the structural stability of TiO2 nanotubes. The nanotubular structure allows both facile strain relaxation of tin and rapid mass transport, leading to greatly enhanced electrochemical performance in terms of specific capacity, cycle life and rate capability.

A simple approach is proposed to prepare C-SiO2 composites as anode materials for lithium ion batteries. In this novel approach, nano-sized silica is soaked in sucrose solution and then heat treated at 900 °C under nitrogen atmosphere. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis shows that SiO2 is embedded in amorphous carbon matrix. The electrochemical test results indicate that the electrochemical performance of the C-SiO2 composites relates to the SiO2 content of the composite. The C-SiO2 composite with 50.1% SiO2 shows the best reversible lithium storage performance. It delivers an initial discharge capacity of 536 mAh g−1 and good cyclability with the capacity of above 500 mAh g−1 at 50th cycle. Electrochemical impedance spectra (EIS) indicates that the carbon layer coated on SiO2 particles can diminish interfacial impedance, which leads to its good electrochemical performance.Highlights► Carbon-coated SiO2 was prepared by covering the nano-SiO2 with pyrolysed sucrose. ► The C-SiO2 composite has the capacity of above 500 mAh g−1 at 50th cycle. ► Electrochemical performance of carbon-coated SiO2 is better than carbon mixed SiO2.

Pd–Ni alloys with different compositions (i.e. Pd2Ni, PdNi, PdNi2) dispersed on multi-walled carbon nanotubes (MWCNTs) are prepared by ultrasonic-assisted chemical reduction. The X-ray diffraction (XRD) patterns indicate that all Pd and Pd–Ni nanoparticles exist as Pd face-centered cubic structure, while Ni alloys with Pd. The transmission electron microscopy (TEM) images show the addition of nickel decreases the particle size and improves the dispersion. The X-ray photoelectron spectroscopy (XPS) spectra demonstrate the electronic modification of Pd by nickel doping. The electrochemical measurements reveal that the PdNi catalysts have better catalytic activity and stability for formic acid electrooxidation, among them PdNi/MWCNTs is the best. The performance enhancement is ascribed to the increase of electroactive surface area (EASA) and nickel doping effect which might modify the electronic structure.

Highly ordered, vertically oriented TiO2 nanowire arrays (TNAs) are synthesized directly on transparent conducting substrate by solvothermal procedure without any template. The X-ray diffraction (XRD) pattern shows that TiO2 array is in rutile phase growing along the (0 0 2) direction. The field-emission scanning electron microscopy (FE-SEM) images of the samples indicate that the TiO2 array surface morphology and orientation are highly dependent on the synthesis conditions. In a typical condition of solvothermal at 180 °C for 2 h, the TNAs are composed of nanowires 10 ± 2 nm in width, and several nanowires bunch together to form a larger secondary structure of 60 ± 10 nm wide. Dye-sensitized solar cell (DSSC) assembled with the TNAs grown on the FTO glass as photoanode under illumination of simulated AM 1.5G solar light (100 mW cm−2) achieves an overall photoelectric conversion efficiency of 1.64%.

A simple one-step route using gas template method is applied to synthesize macroporous LiNi0.5Mn0.5O2 which is characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Telle (BET) surface area, charge–discharge tests and electrochemical impedance spectroscopy (EIS) measurements. The as-synthesized material shows pure crystalline phase of LiNi0.5Mn0.5O2, while the microstructure is comprised of macrospores ranging from 0.2 to 0.5 μm. The first discharge capacity is of 174 mAh g−1 at 0.1 C rate, which is much higher than that of the material synthesized by the conventional solid state reaction method. Furthermore, the macroporous LiNi0.5Mn0.5O2 material shows remarkable rate capacity and cycle stability, which may be attributed to the shorter lithium ion diffusion distance and better electrolyte penetration.Research highlights► The intrinsic poor electronic conductivity of layered LiNi0.5Mn0.5O2 cathode material limits its wide application. ► In this study, pure phase, well-crystallized macroporous LiNi0.5Mn0.5O2 was prepared by a simple one-step route using gas template. ► The as-synthesized LiNi0.5Mn0.5O2 has much higher first discharge capacity than the material synthesized by conventional solid state reaction method. ► Furthermore, the macroporous LiNi0.5Mn0.5O2 material also possesses remarkable rate capacity and cycle stability.

A hierarchical porous MnO2-based electrode was prepared and its electrochemical performance for electrochemical capacitors was investigated. In this work, porous MnO2 film with pore size of 2–3 nm in diameter was deposited on a three-dimensional porous current collector by cathodic electrodeposition associated with subsequent controlled heat treatment at 200°C for 2 h. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the heat treatment has a great effect on the formation of the porous structure of MnO2 layer, and the disordered porous structure was caused by dehydration during the heat treatment. Cyclic voltammetry and galvanostatic charge–discharge tests showed that both energy and power densities are enhanced due to the unique hierarchical porous structure. The electrode delivers a high specific capacitance of 385 F g−1 at a high current density of 5 A g−1 within a potential window of −0.05 ∼ 0.85 V, and also exhibits excellent rate capability and electrochemical stability.

Hydrophobic ionic liquid–silica–PVdF-HFP polymer composite electrolyte is synthesized and employed in lithium air batteries for the first time. Discharge performance of lithium air battery using this composite electrolyte membrane in ambient atmosphere shows a higher capacity of 2800 mAh g−1 of carbon in the absence of O2 catalyst, whereas, the cell with pure ionic liquid as electrolyte delivers much lower discharge capacity of 1500 mAh g−1. When catalyzed by α-MnO2, the initial discharge capacity of the cell with composite electrolyte can be extended to 4080 mAh g−1 of carbon, which can be calculated as 2040 mAh g−1 associated with the total mass of the cathode. The flat discharge plateau and large discharge capacity indicate that the hydrophobic ionic liquid–silica–PVdF-HFP polymer composite electrolyte membrane can effectively protect lithium from moisture invasion.

Pd–Pb hollow nanospheres dispersed on carbon black were developed by a galvanic replacement reaction between sacrificial cobalt nanoparticles and Pd2+, Pb2+ ions. The as-prepared catalysts were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The electrochemical measurements show that the as-prepared catalysts have excellent catalytic activity for formic acid electrooxidation, which is attributed to the large surface area caused by the hollow structure and the lead doping effect which might modify the electronic structure of the catalysts.

Nanosized Sn–Co prepared by ultrasonic-assisted chemical reduction is milled with artificial graphite (AG) to form Sn–Co–AG composite. The as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrometry and Brunauer–Emmett–Telle (BET) surface area measurement. XRD patterns show that Sn–Co particles are poorly crystallized and artificial graphite has a typical hexagonal graphite structure phase. The diffraction peaks of Sn–Co particles remain the same but some of AG obviously change after milling Sn–Co with AG. BET areas of AG, Sn–Co and Sn–Co–AG are 1.569, 13.187 and 6.754 m2 g−1, respectively. SEM images display the as-prepared Sn–Co particles have a size distribution ranging from 20 to 70 nm in diameter. After milling Sn–Co with AG, Sn–Co particles keep similar morphology but there is a perceptible change in AG. Electrochemical tests show that Sn–Co–AG composite possesses much improved electrochemical performance than the state-of-the-art graphite. This composite has great potential as an alternative material for improving the energy density of a lithium ion secondary battery.

A binder-free three-dimensional (3D) porous Cu6Sn5 anode was prepared for lithium-ion batteries. In this novel approach, tin was deposited by electroless-plating on copper foam which was served as anode current collector as well as the source of copper for Cu6Sn5 alloy formation. With optimized post-treatment condition, Cu6Sn5 alloy with thickness of 1.2 μm was formed on the surface of copper foam network. 3D porous Sn–Cu6Sn5 and Cu3Sn–Cu10Sn3–Cu6Sn5 composite anodes were also prepared for comparison. Electrochemical tests showed that 3D porous Cu6Sn5 anode exhibits the best electrochemical performance in terms of specific capacitance and cycleability, which delivers a rechargeable capacity of 404 mAh g−1 over 100 cycles.

Pt nanocatalysts supported on glassy carbon (GC) were electrochemically deposited by cyclic voltammetry (CV) with different scanning potential ranges. The lower limit of potential was fixed at −0.25 V vs. saturated calomel electrode, whereas the upper limit of potential was adjusted to be 0.0, 0.20, 0.60, and 1.0 V. Scanning electron microscopy images showed that Pt microparticles are uniformly dispersed on the GC substrate and the agglomerated microparticles are composed of numerous nanoparticles. In addition, the catalytic capabilities of Pt/GCs for methanol electrooxidation were examined by CV, chronoamperometry, and electrochemical impedance spectroscopy in a solution of 0.5 M CH3OH and 0.5 M H2SO4. The results demonstrate that the catalytic activities and stabilities of Pt catalysts prepared by the potential ranges from −0.25 to both 0.60 and 1.0 V for methanol electrooxidation were higher than the others, which may be due to their higher electrochemical active surface area, lower charge transfer resistance, and more preferred Pt crystallographic orientation.

TiO2 array film fabricated by potentiostatic anodization of titanium is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge–discharge measurements. The XRD results indicated that the TiO2 array is amorphous, and after calcination at 500 °C, it has the anatase form. The pore size and wall thickness of TiO2 nanotube arrays synthesized at different anodization voltages are highly dependent on the applied voltage. The electrochemical performance of the prepared TiO2 nanotube array as an electrode material for lithium batteries was evaluated by galvanostatic charge–discharge measurement. The sample prepared at 20 V shows good cyclability but low discharge capacity of 180 mA h cm−3, while the sample prepared at 80 V has the highest discharge capacity of 340 mA h cm−3.

PtRuMoOx and PtRuWOx catalysts supported on multi-wall carbon nanotubes (MWCNTs) are prepared by ultrasonic-assisted chemical reduction method. XRD measurements indicate that Pt exists as face-centered cubic structure, Ru is alloyed with platinum, and the metal oxides exist as an amorphous structure. TEM pictures show that PtRuMoOx and PtRuWOx catalysts are well dispersed on the surface of MWCNTs with the particle size of about 3 nm and a narrow particle size distribution. The electrochemical properties of the catalysts for methanol electrooxidation are studied by cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP). The onset potentials for methanol oxidation on PtRuMoOx and PtRuWOx are more negative than that of pure Pt catalyst, shifting negatively by about 0.20 V and have better electrocatalytic activities than PtRu/MWCNTs.

LiFePO4 has attracted broad attention as a promising cathode material for lithium ion batteries. One of the key issues related to LiFePO4 performance lies on the intrinsic characteristic of Li/Fe inter-site mixing. To explore the effect of the defect chemistry on electrochemical behavior, LiFePO4 is synthesized by hydrothermal method with pH value varying from 11.04 to 5.40. The results show that pure phase of LiFePO4 could only be obtained at slightly basic and neutral conditions, and Rietveld refinements reveal that the degree of vacancies and inter-site mixing increase with decreasing pH value. The amounts of Fe on Li sites is nearly zero at pH value of 8.19, whereas 3.5% at 6.30. EIS measurements confirm that the occupation of Fe on Li sites will block the one-dimensional tunnel for lithium ion diffusion. It is vital to prevent the defect chemistry of LiFePO4 by optimizing the synthesis conditions.

Nanostructured MnO2 was synthesized by co-precipitation in the presence of Pluronic P123 surfactant and characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The sample without surfactant was spherical with particle size on the submicron scale, whereas P123-assisted samples were all loose clew shapes, consisting of MnO2 nanowires, 8–20 nm in diameter and 200–400 nm in length. The electrochemical performances of the as-prepared MnO2 as the electrode materials for supercapacitors were evaluated by cyclic voltammetry and galvanostatic charge–discharge measurements in a solution of 1 M Na2SO4. The sample without surfactant exhibited a relatively low specific capacitance of 77 F g−1, whereas the nanostructured MnO2 prepared with 0.02% (wt%) P123 exhibited excellent pseudocapacitive behavior, with a maximum specific capacitance of 176 F g−1.

PtRuSnOx supported on multi-wall carbon nanotubes (MWCNTs) was prepared by ultrasonic-assisted chemical reduction method. The as-prepared catalyst was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns indicate that Pt exists as the face-centered cubic structure, Ru is alloyed with platinum, while non-noble metal oxide SnOx exists as an amorphous state. From TEM observation, PtRuSnOx is well dispersed on the surface of MWCNTs with the particle size of several nanometers. The electrochemical properties of the as-prepared catalyst for methanol electrooxidation were studied by cyclic voltammetry (CV) and chronoamperometry (CA). The onset potential of methanol oxidation on PtRuSnOx and PtRu catalysts is much more negative than that on Pt catalyst, shifting negatively by about 0.20 V, while the peak current density of methanol oxidation on PtRuSnOx is higher than that on PtRu. Electrochemical impedance spectroscopy (EIS) studies also show that the reaction kinetics of methanol oxidation is improved with the presence of SnOx. The addition of non-noble metal oxide SnOx to PtRu promotes the catalytic activity for methanol electrooxidation and the possible reaction mechanism is proposed.

Poor crystallined α-MnO2 grown on multi-walled carbon nanotubes (MWCNTs) by reducing KMnO4 in ethanol are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer–Emmett–Telle (BET) surface area measurement, which indicate that MWCNTs are wrapped up by poor crystalline MnO2 and BET areas of the composites maintain the same level of 200 m2 g−1 as the content of MWCNTs in the range of 0–30%. The electrochemical performances of the MnO2/MWCNTs composites as electrode materials for supercapacitor are evaluated by cyclic voltammetry (CV) and galvanostatic charge–discharge measurement in 1 M Na2SO4 solution. At a scan rate of 5 mV s−1, rectangular shapes could only be observed for the composites with higher MWCNTs contents. The effect of additional conductive agent KS6 on the electrochemical behavior of the composites is also studied. With a fixed carbon content of 25% (MWCNTs included), MnO2 with 20% MWCNTs and 5% KS6 has the highest specific capacitance, excellent cyclability and best rate capability, which gives the specific capacitance of 179 F g−1 at a scan rate of 5 mV s−1, and remains 114.6 F g−1 at 100 mV s−1.

Fibriform polyaniline/nano-TiO2 composite is prepared by one-step in situ oxidation polymerization of aniline in the presence of nano-TiO2 particles, which contains 80% conducting polyaniline by mass, with a conductivity of 2.45 S/cm at 25 °C. Its maximum specific capacitance is 330 F g−1 at a constant current density of 1.5 A g−1, and can be subjected to charge/discharge over 10,000 cycles in the voltage range of 0.05–0.55 V.

PtRuMe (Me = Fe, Co, Ni) catalysts dispersed on multi-wall carbon nanotubes (MWCNTs) were prepared by ultrasonic-assisted chemical reduction. X-ray diffraction (XRD) showed that Pt existed as face-centered cubic structure, while Ru and Me alloyed with Pt. The calculated particle sizes from XRD data are of 3.40, 3.40, 2.61 and 3.06 nm for PtRu, PtRuFe, PtRuCo and PtRuNi, respectively, and are consistent with TEM results. The electrochemical measurements showed that the addition of Me to PtRu enhances the electrocatalytic properties for methanol oxidation and PtRuNi has the best catalytic activity and stability.

Pt-MoOx supported on glassy carbon was co-deposited by cyclic voltammetry (CV). The lower limit of potential was fixed at −0.25 V (vs. SCE), whereas the upper limit was adjusted to be 0.0, 0.10, 0.40, 0.60 and 1.0 V. The as-prepared catalysts were characterized by X-ray photoelectron microscopy, scanning electron microscopy and transmission electron microscopy. The results show that Pt-MoOx particles are uniformly dispersed on the substrate and the agglomerated microparticles are composed of numerous nanoparticles with a size of several nanometers. The catalytic capabilities of Pt-MoOx for methanol oxidation were examined by CV and chronoamperometry. Electrochemical measurements demonstrate that the catalytic activities and stabilities of Pt-MoOx prepared in the potential ranges from −0.25 to both 0.60 and 1.0 V were higher than the others, which may due to the higher active surface area, more appropriate Pt/Mo ratio and more preferred Pt crystallographic orientation.

•PDA with polar functional group was coated onto the surface or interspace of ultralight graphene sheets.•PDA layer are used as bifunctional materials for adsorption agent and buffer.•The PDA-HRG/S electrode shows outstanding cycling stability and rate capability.The soft polydopmine (PDA) layer with polar functional group was coated onto the ultralight graphene sheets (HRG) using a simple approach in a mixture of ethanol and water solution. Sulfur was further dispersed onto the surface of PDA-HRG sheets by S/CS2 solution impregnation method to obtain PDA-HRG/S composite as the cathode material for lithium sulfur batteries. The resulting composites are characterized by SEM, TEM, XRD and so on. The ultralight graphene matrix could improve the conductivity of the electrode and offer a large surface for deposition of sulfur, while the coating of hydrophilic soft PDA layer can adsorb polar polysulfides on-site and accommodate the volume change of S during the discharging processes, resulting in an excellent electrochemical performance.

•Porous PdAu foam catalysts are successfully fabricated using hydrogen bubble dynamic template.•The catalysts have 3D hierarchical pores and numerous interconnected dendrite walls.•Pd and Au uniformly distribute in the porous catalysts and form an alloy structure.•The porous PdAu catalysts show higher catalytic performance and stability for methanol oxidation than pure porous Pd.Pd–Au porous foam films with three-dimensional hierarchical pores consisting of interconnected dendrite walls are obtained by using the hydrogen bubble dynamic template. The films are characterized by scanning electron microscope, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, as well as electrochemical techniques. The CV curves have confirmed that the Pd–Au catalysts have high catalytic activity toward methanol oxidation. The catalytic activities of these Pd–Au catalysts are strongly dependent on the atomic ratio of Pd/Au. Among all the Pd–Au catalysts, the Pd1Au1 catalyst is found to possess superior catalytic activity and stability toward methanol oxidation.

The electrochemical performance of lithium–oxygen (Li–O2) batteries depends largely on the architecture and catalytic effectiveness of the oxygen cathode. Herein, in this study, a graphene aerogel decorated with MoSx nanosheets (MoSx/HRG) with a three-dimensional porous framework synthesized using a one-step hydrothermal reaction followed by freeze-drying is reported. The MoSx/HRG aerogel possesses hierarchical mesopores and micropores, which could facilitate electrolyte impregnation and oxygen diffusion, and provide much more accommodation space for the reaction products. The lithium–oxygen batteries based on this MoSx/HRG aerogel cathode show improved electrochemical performance, with a high initial discharge capacity up to 6678.4 mA h g−1 at a current density of 0.05 mA cm−2 and better cycling capability with a cut-off capacity of 500 mA h g−1 at a current density of 0.1 mA cm−2, compared with the lithium–oxygen batteries based on an HRG aerogel cathode. The enhanced performance is ascribed to the excellent catalytic activity of the MoSx nanosheets and the unique three-dimensional porous architecture.

Carbon coated TiO2–SiO2 nanocomposites (CTSO) with high grain boundary density fabricated by a simple hydrothermal approach have been investigated as anode materials for lithium-ion batteries. The CTSO anode exhibits superior high-rate capability and excellent cycling performance. The specific capacity of CTSO is much higher than that of pure TiO2 and silica-modified TiO2 without carbon nanocoating (TSO), indicating a positive synergistic effect of the material and structural hybridization on the enhancement of the electrochemical properties. The possible contributing factors include the formation of the Ti–O–Si bonding, which facilitates the reaction between SiO2 and Li; the presence of carbon layering on each nanocrystal; high grain boundary density among the nanoparticles and grain boundary interface areas embedded in a carbon matrix, where electronic and ionic transport properties are tuned by interfacial design and by varying the spacing of interfaces down to the nanoscale regime. The grain boundary interface embedded in the carbon matrix can also store electrolyte and allows more channels for the insertion/extraction reaction of Li ions. The composites exhibit strong potential as a promising anode for lithium-ion batteries.

Cu6Sn5-coated TiO2 nanotube arrays, a novel design for an anode material in lithium ion batteries, were prepared by electroless plating techniques. In this design, a Cu6Sn5 layer was coated on to the inner wall surface of TiO2 nanotubes. The hollow structure of the nanotubes was still retained, although the inner diameter of the nanotubes decreased from 100 nm to 50 nm. The as-prepared Cu6Sn5-coated TiO2 nanotube arrays combine the merits of the high specific capacity of tin and the structural stability of TiO2 nanotubes. The nanotubular structure allows both facile strain relaxation of tin and rapid mass transport, leading to greatly enhanced electrochemical performance in terms of specific capacity, cycle life and rate capability.

In this work, hierarchically porous honeycomb-like carbon (HCC) was prepared and used in the fabrication of the air electrode for lithium–oxygen batteries. The HCC-based electrode was found to yield an obviously higher specific capacity of 3233 mA h g−1 without the addition of catalysts and an improved cycle efficiency with a higher discharge voltage plateau (2.75 V vs. 2.50 V) than conventional carbon. The enhanced performance is largely ascribed to its unique porous structure, which consists of large tunnels for oxygen diffusion into the inner electrode and nanosized pores, which serve as reactive sites for oxygen reduction reactions and provide more room for accumulation of deposits. Furthermore, HCC samples with different pore sizes of 400 and 100 nm were investigated in lithium–oxygen batteries. There is a significant relationship between the discharge performance and the diameter.

In this study, phenyl sulfonated graphene/sulfur (PhSO3-RG/S) composites were synthesized for the first time via an in situ redox reaction in aqueous solution. These composites were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetry (TG). The results show that sulfur was thoroughly enveloped by functionalized water-soluble phenyl sulfonated graphene, providing a conductive coating for electron transport and functional groups that interact strongly with polysulfides or sulfur to improve trapping. In our study, we found that large amounts of conductive carbon additives and binders were not required when the electrodes were prepared on carbon-coated aluminum foil substrates because phenyl sulfonated graphene has excellent electrical conductivity, and contains functional groups that interact strongly with carbon and sulfur. The electrochemical tests show that the binder-free PhSO3-RG/S electrodes have high reversible capacity, good cycling stability at the current density of 0.2 C, and excellent rate capability.