Elementary process analysis of charge transfer processes of lithium-ion batteries through the distribution of relaxation times method

Electrochemical impedance spectra were analysed for laminated and commercially available cylindrical batteries with varying electrode materials and degrees of cycle degradation. The distribution of relaxation times method was used to isolate the elementary processes, enabling an investigation into how cathode materials and cycle degradation impact battery impedance. It was observed that batteries, irrespective of their cathode material, exhibited four impedance components within the frequency range of the charge transfer process, with distinctions in the charge transfer process of the cathode manifesting at lower frequencies. The consistent presence of four primary impedance components was also noted in batteries subjected to varying degradation cycles. The results indicate that the number of significant elementary processes within the battery remains unchanged across different cathode materials and degrees of cycle degradation. The observed increase in the electrochemical impedance owing to degradation was ascribed to the charge transfer process originating from the cathode material.