Revealing the Aging Mechanism of the Whole Life Cycle for Lithium-ion Battery Based on Differential Voltage Analysis at Low Temperatures

The degradation of low-temperature cycle performance in lithium-ion batteries impacts the utilization of electric vehicles and energy storage systems in cold environments. To investigate the aging mechanism of battery cycle performance in low temperatures, this paper conducts aging experiments throughout the whole life cycle at −10 ℃ for lithium-ion batteries with a nominal capacity of 1 Ah. Three different charging rates (0.3 C, 0.65 C, and 1 C) are employed. Additionally, capacity calibration tests are conducted at 25 ℃ every 10 cycles, along with a 10 s internal resistance test at 50% state of charge, and a low-rate charging/discharging test to obtain the differential voltage curve. The experimental results reveal a non-linear characteristic in the rate of battery capacity decay throughout the whole life cycle process. Initially, the decay rate is relatively slow but accelerates once the capacity reaches approximately 0.75 Ah. Differential voltage analysis and correlation analysis demonstrate that the loss of lithium inventory dominates the aging process, while the accelerated decay rate in the later stage is associated with the loss of active positive electrode material and a significant increase in the internal resistance of the battery. This study provides crucial guidance for the low-temperature utilization of lithium-ion batteries.