In a battery application, overcharging may occur due to possible inconsistency among the batteries, or failure of the battery management system, thereby accelerating the degradation of the batteries. At low temperatures, the overcharging is more likely to occur, because the charging cut-off voltage is more easily exceeded due to the stronger polarization effect. In this paper, the characteristics and mechanisms of Li(Ni0.5Co0.2Mn0.3)O2/graphite battery degradation caused by overcharging to 4.4-4.8 V at 0.2-1C currents at -10℃ were experimentally investigated. The results show that there are two modes of battery degradation, linear fading at 0.2C charging, and two-stage linear fading with turning points at 0.5C and 1C charging. According to the incremental capacity analysis curve, the loss of active material is the main mechanism leading to battery degradation, followed by the loss of lithium ions, and the conductivity loss is the least.
Keywords Lithium-ion battery, Low temperature, Overcharge, Degradation