Kinetic Transitions and Irreversible Changes in OCV Hysteresis of LiFePO4 Batteries under Cold Exposure

Lithium iron phosphate (LiFePO4) batteries exhibit significant open-circuit voltage (OCV) hysteresis between charge and discharge paths, affecting state-of-charge (SOC) estimation accuracy. This study investigates the temperature dependence of OCV hysteresis in commercial LiFePO4 cells down to −20 °C and examines irreversible changes associated with low-temperature exposure. OCV hysteresis increased exponentially with decreasing temperature, exceeding ten times its room-temperature value at −20 °C. Arrhenius analysis showed an apparent change in slope near 0 °C, with the apparent activation energy increasing from approximately 14–32 kJ mol-1 above 0 °C to 41–73 kJ mol-1 below 0 °C. These results are consistent with an increasing contribution from interfacial processes, including lithium-ion desolvation and charge transfer, although other low-temperature kinetic limitations cannot be excluded. Exposure to −20 °C caused an irreversible increase in OCV hysteresis at 25 °C, especially at low SOC. Differential voltage analysis showed changes in the electrochemical response consistent with possible changes in effective reaction area and interfacial properties. Microcracking and subsequent SEI re-formation are proposed as possible contributing mechanisms, while lithium plating cannot be excluded. These findings provide insight into the kinetic and history-dependent characteristics of OCV hysteresis and may support temperature- and history-aware battery management strategies.