A healthy charging method based on estimation of average internal temperature using an electrochemical-thermal coupling model for LiFePO<inf>4</inf> battery

Abstract

Constant current-constant voltage (CC-CV) charging and pulse current charging are the usual methods for charging Li-ion batteries. Because we are lack of the direct in-situ measurement of Li-ion battery's internal state, both of the two charging methods are controlled without feedbacks from inside of the battery. A new charging method is proposed in this paper based on electrochemical-thermal coupling model (ECTM), taking its advantage of being able to predict not only external but also internal behaviors of Li-ion batteries with satisfactory accuracy. The benefit of the method lies in that the rate of side reactions evoking degradation can be slowed down by restricting the average internal temperature in the radius direction to be lower than a preset value. To achieve this method, the heat generation rate that significantly influences the average temperature of the battery is controlled by cutting off the charging current. With the proposed charging strategy, the useful lifetime of Li-ion batteries can be prolonged while the charging speed is also guaranteed.