Graphene Preparation Of Modified Lithium-ion Battery Electrode Materials

With the trends of miniaturization, integration in electronic products, micro-battery has wide application prospects in electronic devices in the future. At present, in all the micro-batteries lithium-ion batteries can be widely used in electric vehicles, mobile communication equipment supply, storage and other fields owing to their high energy density, high operating potential, long cycle life, etc. Therefore, lithium-ion batteries have become a research hotspot.The graphite-based anode of batteries have low specific capacity(330mAh/g). However, graphene nanosheets that have a layered structure (single or less than 10 layers) had shown excellent performance as the anode material in lithium-ion battery because of its excellent electrical conductivity. Therefore, this paper discusses the preparation, characterization and the corresponding electrochemical properties of graphene nanosheets that used in lithium-ion battery as the anode material.Graphene nanosheets which were loose and composed by stripping sheet pile were obtained by thermal inflation decomposition method with reduction of graphite oxide that was prepared by Hummers. The micro-charac terization and cycle performance test of Graphene nanosheets show that the specific surface area was 559.3m2/g, their first discharge and charge capacity were 2180 mAh/g and 1472.3mAh/g and the coulombic efficiency was 48%, after 50 laps rechargeable capacity was 620 mAh/g. The data show that the graphene nanosheets as anode material in lithium-ion battery have a good cycling performance.On this basis, the key factors were investigated through changing the oxidation time, the amount of reactant, the temperature of reduction conditions and the optimized conditions were:the time of low, medium, high temperature in oxidation were 2h, 1h, 30min respectively and the optimal reduction temperature was 300℃. The microscopic structure and surface morphology of as-prepared graphene nanosheets and composites were analyzed by elements analysis, IR, TGA, SEM, TEM, Raman, cyclic voltammetry (CV), AC impedance, capacity circulation etc. The result showed that although graphene nanosheets as anode material for lithium-ion battery have high initial capacity and very stable capacity after 50 circles, the high irreversible capacity severely affect the first coulomb efficiency. The mechanism are not obvious and further improvement was needed.In a conclusion, graphene nanosheets material that have high surface area can be prepared by pyrolysis expansion method and also they showed a excellent cycling performance in lithium-ion batteries. Through further research of its working principle and further improvement of its preparation technology, graphene nanosheets are expected to be a kind of excellent electrode materials.