Synthsis Of Graphene Based Composites For Lithium Ion Batteries With Improved Reversible Capacity

Recently, lithium ion batteries(LIBs) have attracted extensive attention and be used almost everywhere. Normal LIBs anode material includes graphite, silicon, SnO2, tin-based alloy, Li2TiO3, etc. The advantages and disadvantages of these materials are obvious. For example, the electrochemical stability of graphite is quite well. However, its capacity is relatively low. Metal oxides exhibits a high specific capacity, but they suffer from rapid capacity fading because of large volume expansion occuring during cycling process. As a result, graphene has been used in the composites as an additive.Graphene-based composites have been synthesized through solvothermal and ultrasonic method. Co3O4nanorods/graphene nanocomposites,3D-hierarchical NiO-graphene composites and Ni-doped NiO/graphene composites have been characterized by XRD, TGA, Raman, SEM and TEM. Electrochemical performance including charge-discharge curves, rate performance, CV curves and electrochemical impedance spectra reveals that these graphene-based composites exhibit remarkably high reversible lithium storage capacities. Co3O4nanorods/graphene nanocomposites get a capacity of1310mAh g-1after40cycles at a current density of100mA g-1.1100mAh g-1are retained for3D-hierarchical NiO-graphene composites after50cycles at a current density of200mA g-1. It has a superior rate performance and get a capacity of823mAh g-1when the current density is1000mA g-1. When metal Ni particles are doped in the composites, such as the synthesized Ni-doped NiO/graphene composites, the composite also exhibit improved cycling stability and remarkably high reversible lithium storage capacity. A capacity of792mAh g-1is retained in the50th cycle under a current density of200mA g-1.Electrochecial performances reveal that graphene adding into the composites will improve the stability of its cycling performance. The metal oxide itself will reduce the stacking degree of graphene nanosheets and graphene will improve the conductivity of the electrode. Graphene could serve as a useful mechanical framework for activity materials and reduce the inner impedance of LIBs. The physical aggregation of metal oxide can be blocked during cycling process when metal oxide is distributed on the graphene nanosheets. Fast transport channels for electronic conduction could be provided and electrochemical performance will further improved.