Cycle-life prediction model of lithium iron phosphate-based lithium-ion battery module

The aging rate of Li-ion batteries depends on temperature and working conditions and should be studied to ensure an efficient supply and storage of energy. In a battery module, the thermal energy released by the exothermic reaction occurring within each cell is transferred to its adjacent cells, thus leading to a higher internal temperature than that of a single cell. Therefore, there exists a considerable difference between the internal and external temperatures of the module. Thus, it is essential to study the battery module temperature when developing its cycle life (capacity fade) model. In this study, an accelerated cycle life experiment is conducted on an 8-cell LiFePO₄ battery. Eight thermocouples were placed internally and externally at selected points to measure the internal and external temperatures within the battery module. This model is developed based on the Arrhenius equation, which explains the effect of temperature according to its spatial position. The models are developed according to the ambient, external, internal, and total average temperatures generated in the battery module, which are verified with the collected experimental results. The results indicate that the total average temperature–based model exhibits the lowest average percentage error when compared with the experimental data.