Drift Correction in Operando Electrochemical Impedance Spectroscopy for Batteries Research

Operando Electrochemical Impedance Spectroscopy on a cycling battery involves several challenges. As the battery state is continuously changing during discharge/charge cycling, the fundamental stability criterion is not fulfilled, and certain drift of the impedance data is emerged. In the present study, an algorithm for the drift correction was developed for different sets of synthetic data. Various computational steps were followed once created a given set of impedance data: single-frequency-point hysteresis correction, time-state drift correction, regularization of the Distribution of Relaxation Times using the Levenberg-Marquardt algorithm with a penalty contribution, and validation of the resulting data by two-pole Hilbert Transform. An evaluation of the influence of hysteresis noise proved a robust algorithm for the drift corrections of operando impedance.

I. Introduction

Batteries have multiple applications in mobile devices, electric vehicles, and stationary energy storage systems. They have significantly changed the way we live and use electrical energy worldwide. Further research is needed regarding the improvement of battery properties, such as energy/power density, cycling stability, sustainability, and environmental perspectives. Especially the analysis of degradation mechanisms that lead to severe capacity degradation and premature battery failure can provide relevant information for possible optimizations. One of the research strategies is by operando analysis, which includes spectroscopy and imaging techniques, using photons or neutrons [1]. These measurement techniques can be challenging due to complex sample environments, specialized equipment, or access to large-scale facilities with photon/neutron sources. Therefore, typical operando techniques are not readily accessible.