Nanoscale In 2 O 3 Induced Fast Kinetics and Stable Interface for High‐Loading Solid‐State Cathode

Sulfide‐based all‐solid‐state lithium batteries (ASSLBs) with high‐loading cathodes are currently hindered by sluggish Li + /electron kinetics and poor interfacial compatibility. Conventional carbon additives, despite their high conductivity, often trigger detrimental side reactions with sulfide electrolytes. To mitigate these issues, we introduce a multifunctional nanoscale In 2 O 3 conductive agent, integrated via a facile one‐step ball milling process. This nano‐In 2 O 3 effectively mediates interactions between large Li 5.5 PS 4.5 Cl 1.5 (LPSC) and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) particles, enhancing mixing homogeneity and collision efficiency. The resulting composite cathode features a low‐tortuosity Li + transport network and establishes rapid “NCM‐nano In 2 O 3 ‐NCM” electronic pathways within particle gaps. Crucially, In 2 O 3 improves interfacial compatibility between the LPSC and conductive additives, suppressing interfacial degradation. Consequently, a high‐loading cathode (18.34 mg cm −2 ) demonstrates a specific capacity of 131 mAh g −1 at 3C and exhibits excellent cyclability, retaining 97.6% capacity after 500 cycles in NCM811||Li cells. This strategy highlights the potential of nanoscale metal oxide additives for achieving high‐energy‐density ASSLBs through optimized interfacial and transport kinetics.