A Sintering‐Free Cathode for Garnet‐Based All‐Solid‐State Li Metal Batteries

Abstract Garnet‐based solid electrolytes (SEs), which have both high ionic conductivity and great stability with Li metal anodes, are at the center of an ever‐increasing research effort in all‐solid‐state lithium metal batteries (ASSLMBs) toward high safety and high energy density. However, the performance of garnet‐based ASSLMBs is limited by the poor ionic conduction on the cathode side, mainly attributed to the inherent rigidity of oxide ceramic nature. Here, a sintering‐free strategy to boost the ionic conduction of the composite cathode via the use of a soft halide SE is presented. The inclusion of the cathode‐compatible halide SE facilitates efficient and stable Li + conduction within the composite cathode and at the cathode/garnet pellet interface. Compared to the conventional co‐sintered method, the issues associated with element diffusion between solid particles during high‐temperature processes are circumvented, a factor responsible for the degradation and irreversible capacity reduction of the cathode active material. When combined with a lithium metal anode, the new cathode configuration exhibits decent discharge capacity, superior Coulombic efficiency, and enhanced cycle stability. The findings demonstrate the promise of this composite cathode design as a viable pathway for achieving high‐performance garnet‐based ASSLMBs.