Enhanced Linear Kramers-Kronig Validation Method for Battery EIS Data

The validation of electrochemical impedance spectroscopy data is a fundamental step in battery data analysis. Currently, the most widely accepted method for battery impedance data validation is the Linear Kramers-Kronig (LinKK) test, which relies on the analysis of the residuals between the data and the impedance of a circuit model containing several series-connected RC branches. The selection of the number of RC branches is crucial to obtain a reliable and repeatable validation. This work aims to improve the LinKK approach by using an automatic selection of the number of RC branches, based on the sum of the resistance moduli of all RC branches of the model. The enhanced LinKK validation method is successfully used both in simulations and experiments, showing its ability to detect the variation of battery operating point, which is typical of in operando spectroscopy tests. The main advantage of this approach is that the validation does not rely on heuristic thresholds.