Internal Redox Mediation Governs Charge–Discharge Kinetic Asymmetry in Microscale Li‐ and Mn‐Rich Layered Oxides for All‐Solid‐State Batteries

ABSTRACT Integrating Li‐ and Mn‐rich layered oxides (LMRs) into all‐solid‐state batteries (ASSBs) offers a promising route toward high‐energy‐density systems beyond conventional lithium‐ion batteries with Li[Ni 1‒x‒y Co x Mn y ]O 2 (NCM) cathodes and liquid electrolytes. Although microscale LMRs are attractive for practically relevant electrode‐level energy density in sulfide‐based ASSBs, their performance remains limited. Here, we elucidate the asymmetric charge–discharge kinetics of LMRs, originating from kinetically sluggish Mn/O redox in Li 2 MnO 3 ‐derived domains, as a critical bottleneck limiting operation of microscale LMRs (D 50 = 2–12 µm) in ASSBs. During charge, NCM domains facilitate Li 2 MnO 3 delithiation via internal redox mediation, whereas the reverse process is ineffective during discharge, leading to pronounced kinetic asymmetry. This asymmetry results in underutilizat…