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 LiNi_0.83Co_0.11Mn_0.06O₂│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.