Solid electrolytes for practical all-solid-state lithium batteries: integrating ion transport, interfacial mechanics, and scalable manufacturing.

All-solid-state lithium batteries are increasingly viewed as a route toward safer and higher-energy rechargeable batteries, yet the transition from highly conductive electrolyte materials to practically competitive cells remains difficult. The central challenge is no longer simply to maximize bulk ionic conductivity. Solid electrolytes must simultaneously provide continuous ion-transport pathways, stable electrode contact, limited electronic leakage, sufficient mechanical compliance or fracture resistance, and compatibility with manufacturing processes that produce thin electrolyte layers and high-loading electrodes. This review examines solid electrolytes from this integrated materials-mechanics perspective. Oxide, sulfide, halide, nitride, polymer, and composite electrolytes are compared according to the relationship between transport behavior, chemical stability, mechanical response, interface evolution, and processability. Particular attention is given to contact loss, interphase formation, void generation, lithium penetration, and the role of external stack pressure. Recent progress in low-temperature ceramic processing, fluorinated sulfides and halides, structured composite electrolytes, and advanced polymer electrolytes illustrates how these traditionally coupled limitations can be partly decoupled. Manufacturing strategies including dry processing, thin electrolyte fabrication, melt infiltration, and pressure-efficient cell architectures are further discussed. Finally, practical electrolyte design is proposed to shift from optimizing isolated material properties toward balancing conductivity, thickness, interfacial stability, mechanical reliability, and scalable processing under realistic cell conditions.