Experimental investigation on the characteristics of coulombic efficiency of lithium-ion batteries considering different influencing factors

Coulombic efficiency (CE) can quantitatively reflect the side reactions inside the battery and a long battery cycle life. This study proposes a novel quantitative method for characterizing the side reactions of lithium-ion batteries. The main measuring principle is the open circuit state of the battery is simulated through long-term constant-voltage charging, and an ultra-high precision charger measures the average current to quantify the side effects of the battery. The relationship among battery side reaction current, state-of-charge (SOC), and temperature is accurately measured and investigated in detail. Then, the battery CE is determined under different ageing degrees, temperatures, and SOCs. In particular, the evolution process of battery CE in the low SOC range is discussed. Finally, a battery life model related to CE is proposed and verified. The experimental results show that the proposed model has satisfactory accuracy and does not require a large number of test data, which has the application potential to predict the full-lifespan life of new batteries. The study is valuable for understanding and evaluating the complex side effects in the battery ageing process and also provides a new idea for the ageing prediction of new batteries.