Abstract: The intercalation and Absorption processes of Li in graphite cathode of Li-secondary battery were discussed by DFT-B3LYP/6-31G(d) method of quantum chemistry.The storage energy curves of the intercalation processes through the routes of arm-chair and zig-zag directions and the adsorption processes of Li on the graphite surface along three typical directions were calculated.The results show that(1) the intercalation process of Li is a process of energy storage;when Li is just located on the projecting position of carbon atom,the system energy is the highest;when Li is located on the projecting position of carbon-carbon bond,the system energy is higher,and when the Li located on the projecting position of benzene ring center,the system possesses the lowest energy and is the most stable.The arm-chair direction is the most probable route for intercalating of Li to graphite cathode;(2) the process of adsorption of Li on the graphite cathode surface is a process of energy storage,too;the position over the center of benzene ring is the most probable adsorption position when Li is close to the graphite surface.The present article provides a very useful image for understanding and improving the charge and discharge properties of the graphite cathode.

Key words: Lithium-ion secondary battery; Graphite; Charge-discharge process; Density function theory(DFT), Lithium-ion secondary battery, Graphite, Charge-discharge process, Density function theory(DFT)