Mechanism of Charge–Discharge Process of Graphite/LiCoO2 and Graphite/Li(Ni1/3Co1/3Mn1/3)O2 Batteries

AbstractThrough the structural evolution of positive and negative active materials of graphite/LiCoO2 and graphite/Li(Ni1/3Co1/3Mn1/3)O2 batteries during charge and discharge, including phase structure, microstructure, and the changes of diffraction intensity ratio I104/I101 and I012/I104 in Li(Ni1/3Co1/3Mn1/3)O2, it is found that there is no phase transition in positive active materials LiCoO2 and Li (Ni1/3Co1/3Mn1/3)O2 during charge and discharge. The microstructure parameters vary with the charge–discharge process. On the negative side, LiC6 is not formed at the beginning, but there is a process of C–Li solid solution → LiC24 → LiC12 → LiC6. On the basis of these experimental results, the de-intercalation theory of charge and discharge process for two kinds of battery is proposed, and the de-intercalation behavior of Li atoms in positive and negative electrodes and conductive mechanism during charge and discharge is described in detail.