Electro‐Chemo‐Mechanical Coupling in Composite Cathodes of Sulfide‐Based All‐Solid‐State Batteries: Pathways, Degradation, and Design Rules

By replacing flammable organic liquid electrolytes with rigid solid ones, all-solid-state batteries (ASSBs) promise higher pack-level energy density and improved thermal safety than conventional lithium-ion batteries (LIBs). However, their rigidity accompanies elevated significance of mechanical solid-solid contact on charge-transport interfaces during electrochemical operation of cells, which complicates accurate failure diagnosis and obscures rational design rules. This review integrates current understanding of reaction mechanisms and failure pathways of sulfide-based ASSBs, mapping the critical conduction networks, including intra-/inter-CAM transport, CAM|SE interfaces and transport among SE particles in layered oxide composite cathodes and how each is disrupted by electro-chemo-mechanical processes during operation. Beyond cathode volume change during charge and discharge, we highl…