How to Consider the Interfacial Phenomenon in All‐Solid‐State Batteries? – Quantitative Analysis using µ‐Cavity Electrode

Abstract Understanding the intrinsic properties of cathode active particles is required to understand how they depend on the charge transfer resistance at solid–liquid or solid‐solid interfaces. Depth‐of‐discharge (DOD)‐dependent charge transport occurs when lithium ions move from the bulk electrolyte to the cathode active particles. However, composite electrodes consist of unevenly distributed active material, conductive additives, and polymeric binder, which complicates the electron/ion conduction path; hence, estimating the DOD‐dependent charge transfer resistance is difficult. However, micro‐sized spherical cathode active particles can be arranged into a cylindrical cavity trap on a microelectrode to evaluate the interfacial behavior of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode active particles in liquid and solid electrolyte systems. The electrochemical parameters calculated from the resultant Tafel plot can encourage meaningful discussions and demonstrate the reliability of the measurement technique.