Experimental Investigation on the Temperature Dependence of Open-Circuit Voltage Hysteresis in LiFePO4 Lithium-Ion Batteries

A commercial LiFePO4 Lithium-ion (LFP-LIB) cell was adopted to investigate hysteresis of open circuit voltage (OCV) in Lithium-ion batteries. Experiments were conducted within the typical operating temperature range of 0℃, 10℃, 20℃, 30℃, 40℃ and 45℃, covering state of charge (SOC) from 0% to 100%. The results showed that (i) OCV hysteresis is dependence on temperature and increases as the temperature decreases, and (ii) bimodality appears in certain SOCs. Comparing the impedances confirmed by electrochemical impedance spectroscopy (EIS), we found that charge-transfer resistance (Rct) increases significantly as the temperature decreases. This means that the LFP-LIB operating at lower temperatures suffers a higher polarization. This result indicates that identification of OCV hysteresis is essential for accurate SOC estimation.