Composite Electrode‐Hybrid Electrolyte Integration Strategy for Enhanced Ion Transport and Scalable All‐Solid‐State Lithium Batteries

Achieving both high energy density and long‐term cyclability in all‐solid‐state lithium batteries (ASSBs) remains a formidable challenge, particularly under high‐cathode‐loading conditions, where interfacial instability and through‐plane Li + transport limitations compromise performance. This study reports a synergistic design that combines a hybrid solid electrolyte (HSE) and a composite electrode (CE) incorporating ball‐milled Al‐doped Li 6.28 Al 0.24 La 3 Zr 2 O 11.98 (BM Al‐LLZO) to address these bottlenecks. The HSE, containing 3 wt% BM Al‐LLZO dispersed in a poly (ethylene oxide)‐based, in situ polymerized matrix, exhibits enhanced ionic conductivity (1.04 × 10 −3 S cm −1 ) and a high Li‐ion transference number (t + = 0.661) owing to uniform filler dispersion and strong polymer–ceramic interfacial synergy. However, particle confinement at the electrode surface limits bulk ion percolation. To overcome this issue, a CE architecture with BM Al‐LLZO homogeneously embedded throughout the cathode matrix is proposed. This design significantly reduces ionic resistance and enables continuous transport pathways. Consequently, the CE||SPE||Li cell delivers excellent performance, retaining 71.55 % of its initial capacity after 200 cycles at 0.5C, while a high‐loading pouch cell demonstrates scalable applicability with over 90 % coulombic efficiency. These findings underscore the critical role of interfacial engineering in ASSBs and provide a practical route toward high‐performance, scalable solid‐state battery systems.