A study on half‐cell equivalent circuit model of lithium‐ion battery based on reference electrode

Abstract

Lithium-ion battery accidents occur frequently, and thermal runaway accidents are common. Lithium plating may occur in batteries at different temperatures, state of charge (SOCs), charging rates, etc., and lithium plating at the anode is one of the important incentives for thermal runaway of batteries. The plating of lithium metal is closely related to the anode potential of the battery. In this paper, based on the anode potential sensor, the anode potential of the battery under various working conditions is detected in real-time, and the direct anode equivalent circuit model (DAECM) and the indirect anode equivalent circuit model (IDAECM) are proposed. The DAECM directly estimates the anode potential based on identifying anode parameters. Therefore, the IDAECM is proposed to estimate the cathode potential directly based on cathode parameter identification, to estimate the anode potential indirectly. First, the high-precision P2D model is used to simulate the cathode, anode, and full cell potentials under various working conditions. According to the 1/50C discharge rate test, the open circuit voltage (OCV)-SOC curve of the cell is obtained. The NEDC conditions are used to identify the parameters of the model, and the values of each parameter of the two models under different SOCs are obtained. According to the parameter identification results above, the anode potential under multirate constant current charging (MRCC) test conditions is estimated. Based on the method above, the IDAECM model is suitable for estimating the anode potential in the early stage of fast charging with large rate constant current, while the DAECM model is suitable for the final stage of fast charging with small rate constant current.