Recently, lithium ion batteries which have a Li1-xMn2O4 and LiMO2 (M = Co, Ni and Mn) cathode are used as an energy storage device for electric vehicles. However, the effect of the composition of cathodes for performance degradation remains unclear. In this study, we conducted systematic calendar life tests at two temperatures (25°C, 60°C) and six SOCs (0%, 40%, 60%, 70%, 80%, 100%) using commercial 18650-type lithium-ion batteries with Li1-xMn2O4 and Li1-yNi0.5Co0.2Mn0.3O2 composite cathodes. To understand the degradation mechanism, we adopted non-destructive dV/dQ curve analyses. We clarified that cathode/anode reaction region slip mainly caused cell capacity fade, and were accelerated by both temperature and SOC. In addition, the degradation of cathodes also caused cell capacity fade at the specific SOCs of 60% and 70% at 60°C. This is probably due to the manganese dissolution of Li1-xMn2O4 in the electrolyte which occurs when x is around 0.2.

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[in Japanese]

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[in Japanese]

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