Research on mechanism of insertion/deinsertion lithium for graphite negative electrode of lithium ion batteries

The mechanism of insertion/deinsertion of lithium ion in graphite electode means of cyclic vohammetry technique and electrochemical impedance spectroscopy. was investigated by The results showed that the rate-limiting step of the electrode process was the diffusion of lithium in the graphite. There were three distinct charge-discharge platforms respectively at 0.20/0.22 V, 0. 11/0. 14 V, 0.08/0. 10 V (vs·Li/Li⁺) in the process of insertion and deinsertion of lithium ion. Each platform is a two-phase coexistence region, may be corresponding to the phase transition process of three lithium-graphite intercalation compounds:LiC₇₂(8 steps)⇔LiC₃₆(4 steps),LiC₃₆(4 steps)⇔LiC₁₂(2 steps),LiC₁₂(2 steps)⇔LiC₆(1 steps).