State of heath estimation of lithium-ion batteries based on electrochemical impedance spectroscopy and backpropagation neural network

The global electric vehicle (EV) is expanding enormously, foreseeing a 17.4% increase of compound annual growth rate (CAGR) by the end of 2027 [1], the lithium-ion battery is considered as the most widely used battery technology in EV. The accurate and reliable diagnostic and prognostic of battery state guarantee the safe operation of EV and are crucial for durable electric vehicles. Research focusing on lithium-ion battery life degradation has grown more importance in recent years. In this study, a model built for state of health (SoH) estimation for LTO-anode based lithium-ion battery is presented. First, the electrochemical impedance spectroscopy (EIS) is used to study the deterioration in battery performance, measurements such as charge transfer resistance and ohmic resistance are analyzed for different operational conditions and selected as key characteristic parameters for the model. Then, the model based on backpropagation neural network (BPNN) along with the characteristic parameters is trained and validated with a real-life driving profile. The model shows a relatively accurate estimation of SoH with a mean square error (MSE) of 0.002.