A sintering-free cathode for garnet-based all-solid-state Li metal batteries

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. (© 2024 Wiley‐VCH GmbH)