Influence of State‐of‐Charge‐Dependent Decomposition Kinetics at the Li6PS5Cl|LiNi0.83Co0.11Mn0.06O2 Interface on Solid‐State Battery Performance

Solid‐state batteries represent a new approach to energy storage, offering superior safety, higher energy density, and extended cycle life compared to conventional liquid electrolyte‐based lithium‐ion batteries. However, the practical application of solid‐state batteries is hindered by degradation phenomena, particularly on interfaces between components, compromising their long‐term performance. In this work, the kinetics of the state‐of‐charge‐dependent electrolyte degradation at the LiNi0.83Co0.11Mn0.06O2│Li6PS5Cl interface, as well as its influence on cycling performance, are systematically studied electrochemically in solid‐state battery half cells. Combining cycling and C‐rate experiments with electrochemical impedance spectroscopy reveals that half cells charged to higher cutoff potentials (≥3.8 V versus In/InLi; ≥4.4 V versus Li+/Li) exhibit significantly faster degradation kinetics. These influence the cycling performance leading to a plateau in the charge capacity at ≥3.8 V versus In/InLi, while the electrolyte degradation does not affect the bulk electrode transport. Overall, this work emphasizes the importance to investigate state‐of‐charge‐dependent decomposition kinetics in composite electrodes to better understand cycling behavior.