A technique for separating the impact of cycle aging and temperature on Li-ion battery capacity

Reduction of battery capacity is a well-known symptom of aging, making it a universally accepted indicator of the state of health. Capacity also significantly depends on temperature, therefore, separating the effect of temperature from that due to aging has utmost important for a proper state of health assessment. However, according to the latest literature, there is a lack of information about how the temperature dependency of capacity changes with battery aging. In this respect, the study presented in this paper is based on an experimental campaign aimed at measuring battery capacity at different temperatures and cycling levels. Starting from the obtained results, an analytical model describing how the variation law of battery capacity with temperature is affected by cycling was proposed and validated. The achieved accuracy is better than 0.6 % for all the considered operating conditions.