Aging modeling and lifetime optimization of Li-ion LiFePO4-graphite batteries according to the vehicle use.

Secondary batteries are the electrochemical systems that store electricity onboard ofelectrified vehicles. Understanding battery aging mechanisms impact on power/energyperformances is of significant importance to design safe, cost-efficient and durable energystorage systems. This research and development approach relies on numerical models. In thisPhD work, a simplified electrochemical and thermal battery model including agingmechanisms is developed for a commercial LiFePO4-graphite (LFP/C) Li-ion cell. Theoreticalpower and capacity fade correlations are developed and experimentally validated.Comparisons between model predictions and experimental data on various operatingconditions point out the limits of the approach adopted in this work under high-load cyclingtests. The model is nevertheless able to provide qualitative and quantitative information aboutthe battery lifetime under various operating conditions until the End-Of-Life. Parametricstudies on the negative electrode design parameters are performed to discuss the dispersion inthe EOL state occurrence. Finally, simulations are performed to investigate the batterylifetime under calendar and fast charging operations. According to the vehicle usage, anoptimum of the battery lifetime is numerically demonstrated.