Study the fading mechanism of LiMn 2O 4 battery with spherical and flake type graphite as anode materials

Abstract

The fading mechanism of Li ion batteries with two different anode materials was discussed in this study. Anode materials were spherical type of meso-phase carbon micro bead (MCMB) and flake type of pitch coated graphite (PCG). This battery used LiMn 2O 4 as the cathode materials. The LiMn 2O 4/MCMB battery had higher rate capability than the LiMn 2O 4/PCG battery. However, the LiMn 2O 4/PCG battery had only 20% capacity retention after 70 cycling tests, while the LiMn 2O 4/MCMB battery had 95% capacity retention. The X-ray diffraction (XRD) and X-ray photospectroscopy (XPS) were used to analyze the structure of active materials and the solid electrolyte interface (SEI) films on the electrodes. It was found that structure of PCG anode and LiMn 2O 4 cathode was maintained as pristine structure by XRD analysis. The carbonate was easier to decompose on PCG surface than on the MCMB surface by XPS analysis. It was suggested that the electrolyte decomposition on PCG surface might be play a major role for the LiMn 2O 4/PCG battery fading.