An efficient electrochemical optimizer for the distribution of relaxation times of lithium-ion batteries

The distribution of relaxation times (DRT) analysis based on Tikhonov regularization is widely used to analyze the battery electrochemical impedance spectroscopy (EIS), but the selection of the regularization parameter has always been a problem. This paper proposes an Optimization Pre-calculation DRT-tool of EIS (OPDEIS) which not only completes the full-frequency EIS fitting with the insertion capacitor and inductance but also obtains the optimal regularization parameter and the fitting kernel function width through a multi-objective optimization algorithm. In particular, it can resolve the DRT parameter selection for EIS above 0.1 Hz in lithium-ion batteries effectively. This optimizer is suitable for lithium-ion battery EIS data with different states of charge (SOCs) and frequency points. It provides a reference for selecting the regularization parameter and full width at half maximum (FHWM) automatically, enabling the DRT process based on Tikhonov regularization to perfectly avoid overfitting or underfitting.