State of health (SoH) estimation and degradation modes analysis of pouch NMC532/graphite Li-ion battery

Electrochemical voltage spectroscopy (EVS), which includes differential voltage analysis (DVA) and incremental capacity analysis (ICA), has been used extensively in revealing the aging mechanism and evaluating the operating state of Li-ion batteries. The EVS technique is conventionally limited to low-charging-rate scenarios such that the polarization effect has a negligible influence on the spectral characteristics. This makes EVS analysis both time-consuming and unfeasible in real-world scenarios. In this work, for the first time, we have expanded the EVS to realistic C-rate operating conditions by combining it with a programmed electromotive-force (EMF) extraction method to adapt the EVS-based SoH estimation model to any arbitrary charging scenarios. By tracking the features in the EVS curves, the model can properly estimate cell SoH even with partial (dis)charging data, with a maximum error of less than 3%. Furthermore, an electrochemical model is established to identify the thermodynamic attributes on capacity loss. The degradation performance of the NMC532/graphite battery system under different operating conditions was comprehensively studied based on the comparison analysis between the modeling and experimental results