Multiphysical model to assess the temperature and state-of-charge dependence of the OCV of a LIB cell

Lithium-ion batteries (LIBs) have shown rapid growth in both the stationary and vehicle electric storage sectors. This is due to their high energy density, low weight, low memory effect, and low maintenance requirements. The performance of LIBs is greatly influenced by the temperature of the environment and the cell itself. At extreme temperatures, whether cold or hot, phenomena are triggered that damage the capacity and durability of the battery and can lead to the riskiest cases to the cell exploding. In recent years, many researchers have investigated these issues to find solutions that could make batteries more efficient and safer in these operating conditions by improving the battery management system (BMS). The OCV open circuit voltage) behaviour of LFP batteries at different states of charge (SOC), placed in a temperature range from -20°C to 60°C, is analyzed. A multiphysics model was developed to simulate the trend of the experimental results. The results showed that the OCV curves generally maintain a fairly constant trend throughout the experiment, demonstrating the fact of thermal stability of the LFP type. Only in the case of full charge, 100% SOC, is a slightly more variable behaviour noticeable, due to the presence of more active material. To bridge these differences, it would therefore be advisable to conduct tests on the batteries to obtain more certain and reliable data on entropic coefficient values to update the model.