Experimental Study to Investigate the Effects of Temperature Rise during Discharge on Li-ion Battery Degradation

Abstract

Li-ion batteries with higher discharge C-rates show accelerated capacity fade rates. However, an inherent coupling exists between discharge C-rate and temperature as heat generation is inevitable during discharge. The effects of discharge C-rates on capacity fade under consideration of temperatures have not been investigated. This paper presents an experimental study that separates the temperature rise during discharge from the non-thermal effect of discharge C-rates. A design of experiment including two discharge C-rates (C/2 and 3C) and two controlled temperatures (controlled ambient temperature at 45 °C and controlled surface temperature at 45 °C ) were used to provide cycling conditions. In controlled ambient temperature tests at 45 °C, battery surface temperature increased by 5.2 °C at the discharge rate of C/2 and 20.6 °C at 3C. In controlled surface temperature tests at 45 °C, battery surface temperatures were maintained at 45 ±1 °C . Experiment results show that the battery capacity degradation was the joint contribution of the temperature rise and non-thermal effects. Temperature rise during discharge contributes to the battery capacity degradation, while the non-thermal effect of discharge C-rate dominates the capacity loss.