Research The Modification Of Electrode Material For Lithium Ion Secondary Battery

Peridot type lithium iron phosphate becomes the focus of research since it was found can be used as lithium battery cathode. At present, this new cathode material has gradually began to realize commercial. Compared to other commercial cathode materials, lithium iron phosphate exhibits more excellent cyclic performance, higher reversible specific capacity, longer cyclic life span and pollution-free. However, it also has some defects and the insufficiency, namely low conductivity, low diffusion rate versus Li+, which leads to low reversible specific capacity. To solve the problem, coprecipitate synthesis method adopted in this work to obtain graphene-coated lithium iron phosphate nanocomposite, graphene coating on the surface to improve the electronic conductivity and diffusion rate for lithium ions of the lithium iron phosphate, so as to achieve the purpose of improving the electrochemical properties of lithium iron phosphate as cathode material for Li-ion secondary battery. Classic Hummer method adopted to synthesize graphene. The microstructure and morphologies of these composites were investigated by SEM, TEM, XRD, FTIR. The electrochemical performances were evaluated by galvanostatic charge-discharge, cyclic voltammogram. The electrochemical performance of LiFePO4/graphene composite with special structure has been greatly improved, the reversible specific capacity reached 149 mAhg-1 at a rate of 0.2 C, and no obvious decay over 100 constant current charge and discharge cycles.At present the commercialization of lithium ion battery anode materials mainly belongs to carbon materials, which is also the most popular on the market at present of the anode materials for lithium ion batteries. However, researches on the new anode materials with low cost and high capacity are the developing trend of conventional anode materials drive by new energy equipment(such as Electric Vehicle, Hybrid Electric Vehicle, Smart House) market strategy. Carbon materials with a specific capacity of 372 mAh/g cannot meet these upsurge demands. In this paper, we mainly study on transition metal oxide Cu2 O modified by conductive polymer. We obtained Cu2O/polypyrrole nanowires with core-shell structure through a hydrothermal method, which used as anode materials for Li-Ion rechargeable batteries. The microstructure and morphologies of these composites were investigated by SEM, TEM, XRD, FTIR and TGA. The electrochemical performances were evaluated by galvanostatic charge-discharge, cyclic voltammogram. The Cu2O/polypyrrole nanowires exhibit excellent reversible capacities and good cyclability with no fading observed over 100 charge and discharge cycles. Incorporation of conduction polymers popyrrole(PPy) improved the conductivity of Cu2 O, and the flexible shell enhances the stability of electrode during cycling.