Cycle Aging Effect on the Open Circuit Voltage of a LiFePO4 Battery

Lithium-ion batteries (LiBs) are the most recent technologies among rechargeable batteries. Currently, different types of LiBs are available on the market, differing based on the kind of electrodes and electrolyte they use. In any case, LiBs are employed in many applications in both stationary and mobile devices. On the other hand, LiBs degrade in function of the storage and working conditions. Therefore, it is very important to build accurate models that can predict the battery behavior and estimate its parameters. Among the latter, the state of charge (SOC) is one of the most important, which allows the battery to work within its safety limits and prevent its aging. In the literature, it is possible to find many methods for SOC estimations. Most of them require modeling the open circuit voltage (OCV) curve of LiBs, and several OCV-SOC models have been developed as well. Moreover, it is important to model how aging affects these OCV curves. In a previous work, a simple aging model was proposed for a lithium cobalt oxide battery. This model considers how the OCV curve changes as a function of the cycle aging. In the present work, the aim is to extend the latter model to a lithium iron phosphate battery.