Expanding the lifetime of Li-ion batteries through optimization of charging profiles

The increasing penetration of renewable energy sources, incentivized by government policies and decreasing costs, brings the challenge of making electricity supply and consumption meet, as these energy sources are intermittent by nature. Li-ion battery systems integrated in the grid will provide much needed ancillary services, such as frequency regulation, peak shaving and load levelling, so that the challenges of future cleaner grids can be properly addressed. Therefore, efforts on all fronts are being made to further reduce the price of operation, materials and production of Li-ion battery systems. In this research, we propose an optimization of the conventional CC-CV charging protocol typically used in Li-ion batteries. The proposed protocol aims at expanding the lifetime of the system. A reduced-order electrochemical model for a Li-ion cell is used to simulate its dynamic behavior. Additionally, an optimization algorithm is developed and coupled to the dynamic model to obtain optimal charging-discharging profiles that maximizes the cell lifetime. A charging protocol that combines two different charging profiles proved to be an easily implementable and effective way of increasing the cell life time by ca. 27% in these simulations, in comparison to the standard CC-CV protocol.