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Ding Y.H.,Xiangtan University | Ren H.M.,Xiangtan University | Huang Y.Y.,BTR New Energy Materials Inc. | Chang F.H.,Xiangtan University | Zhang P.,Xiangtan University
Materials Research Bulletin | Year: 2013

Three-dimensional graphene/LiFePO4 nanostructures for flexible lithium-ion batteries were successfully prepared by solvent evaporation method. Structural characteristics of flexible electrodes were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrochemical performance of graphene/LiFePO4 was examined by a variety of electrochemical testing techniques. The graphene/LiFePO4 nanostructures showed high electrochemical properties and significant flexibility. The composites with low graphene content exhibited a high capacity of 163.7 mAh g-1 at 0.1 C and 114 mAh g-1 at 5 C without further incorporation of conductive agents. © 2013 Elsevier Ltd. All rights reserved.

Liu Y.F.,Harbin Institute of Technology | Liu Y.F.,Heilongjiang University | Yuan G.H.,Harbin Institute of Technology | Jiang Z.H.,Harbin Institute of Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2014

Ni(OH)2-graphene sheet-carbon nanotube composite was prepared for supercapacitance materials through a simple two-step process involving solvothermal synthesis of graphene sheet-carbon nanotube composite in ethanol and chemical precipitation of Ni(OH)2. According to N2adsorption/desorption analysis, the Brunauer-Emmett-Teller surface area of graphene sheet-carbon nanotube composite (109.07 m2g-1) was larger than that of pure graphene sheets (32.06 m2g-1), indicating that the added carbon nanotubes (15 wt.%) could prevent graphene sheets from restacking in the solvothermal reaction. The results of field emission scanning electron microscopy and transmission electron microscopy showed that Ni(OH)2nanosheets were uniformly loaded into the three-dimensional interconnected network of graphene sheet-carbon nanotube composite. The microstructure enhanced the rate capability and utilization of Ni(OH)2. The specific capacitance of Ni(OH)2-graphene sheet-carbon nanotube composite was 1170.38 F g-1at a current density of 0.2 A g-1in the 6 mol L-1KOH solution, higher than those provided by pure Ni(OH)2(953.67 Fg-1) and graphene sheets (178.25 F g-1). After 20 cycles at each current density (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 A g-1), the capacitance of Ni(OH)2-graphene sheet-carbon nanotube composite decreased 26.96% of initial capacitance compared to 74.52% for pure Ni(OH)2. © 2014 Elsevier B.V. All rights reserved.

Pang C.,Sun Yat Sen University | Pang C.,BTR New Energy Materials Inc. | Song H.,Sun Yat Sen University | Li N.,Sun Yat Sen University | Wang C.,Sun Yat Sen University
RSC Advances | Year: 2015

Si with high theoretical capacity has long suffered from its large volume variation and low electrical transport linked to poor cycling stability and rate performance. Here, a facile approach is reported to mass produce nanostructured Si@carbon with a tunable size of silicon nanoparticles. We performed carbon coating of Si nanoparticles by polyacrylonitrile (PAN) emulsifying and then carbonization. The hollow Si@C nanostructure was obtained via direct etching of Si nanoparticles with HF solution which is more advanced and has better controllability. When evaluated as an anode material for lithium-ion batteries, the C-Si nanocomposites exhibit excellent reversibility and cycling performance. A high capacity of 700 mA h g-1 can be retained after 100 cycles at current densities of 250 mA g-1. The rate capability of the C-Si microfibers is also improved. The special structure is believed to offer better structural stability upon prolonged cycling and to improve the conductivity of the material. This simple strategy could also be applied to prepare other carbon coatings of hollow energy materials. © The Royal Society of Chemistry 2015.

Ren J.-G.,BTR New Energy Materials Inc.
32nd Annual International Battery Seminar and Exhibit | Year: 2015

BTR has dominated the global graphite anode materials market and will continue to expand the business towards other new energy and new materials. SiO is a promising anode material alternative to graphite due to its intrinsic properties of high energy density, low expansion and long cycle life. Carbon-coated SiO by pitch or by CVD has the capacity and efficiency of >1600 mAh/g and 77.0%, respectively. For SiO-contained pouch cell, the energy density can reach ∼700 Wh/L and the capacity retention can reach 86.5% @ 300 cycles; The cylindrical cells comprising SiO work very well for high energy (3.4 Ah) and high power (10C) applications. The current industrial situation of SiO raw materials cannot meet the requirement of SiO anode materials with respect to production capacity, quality control and R&D capability. BTR has achieved the technology innovation of SiO raw materials synthesis and reached the production capacity of 100t/m now.

Yang Y.,City University of Hong Kong | Ren J.-G.,City University of Hong Kong | Ren J.-G.,BTR New Energy Materials Inc. | Wang X.,City University of Hong Kong | And 4 more authors.
Nanoscale | Year: 2013

Anode materials play a key role in the performance, in particular the capacity and lifetime, of lithium ion batteries (LIBs). Silicon has been demonstrated to be a promising anode material due to its high specific capacity, but pulverization during cycling and formation of an unstable solid-electrolyte interphase limit its cycle life. Herein, we show that anodes consisting of an active silicon nanowire (Si NW), which is surrounded by a uniform graphene shell and comprises silicon carbide nanocrystals, are capable of serving over 500 cycles in half cells at a high lithium storage capacity of 1650 mA h g -1. In the anodes, the graphene shell provides a highly-conductive path and prevents direct exposure of Si NWs to electrolytes while the SiC nanocrystals may act as a rigid backbone to retain the integrity of the Si NW in its great deformation process caused by repetitive charging-discharging reactions, resulting in a stable cyclability. © 2013 The Royal Society of Chemistry.

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