Cycle Aging Effect on the Open Circuit Voltage of Lithium-Ion Battery

Nowadays, the issues concerning green mobility and energy production are leading researchers to study novel energy storage systems. Among them, lithium-ion batteries are currently one of the most popular technologies under study. Battery modeling and parameter estimation are important challenges to build reliable battery management systems able to allow the battery to work in proper conditions. State of charge (SOC) estimation is one of the most important for predicting the current battery available energy. Many methods to estimate the SOC need knowledge of the open circuit voltage (OCV) curve. In the literature, it is possible to find a lot of OCV models as a function of SOC. Another important aspect is how these curves change as a function of battery degradation. Some studies deal with the correction of the OCV-SOC curve considering the aging, but the dependency of the OCV curve as a function of the exchanged absolute charge on aging seems to be lacking. In the present work, a simple model of the OCV-charge curve that considers the cycle aging is proposed and analyzed. An experimental campaign was carried out to validate the proposed model.