Ion Pathways Optimized via Interlayer Channels in Bimetallic Hydroxides Enable Ultra‐Stable Solid‐State Batteries

ABSTRACT Solid polymer electrolytes (SPEs) from electrospinning offer robust mechanical frameworks but often require complex post‐treatments and suffer from low room‐temperature ionic conductivity and sluggish Li + transport, hindering the development of solid‐state batteries. Here, we propose a surface‐grown protective fiber strategy: growing CoMn‐layered double hydroxide (LDH) nanosheets on polyacrylonitrile (PAN) nanofibers to anchor residual propylene carbonate (PC) molecules, forming a composite SPE (LDH@PAN SPE) with interfacial stabilization. Abundant LDH hydroxyl groups immobilize PC via hydrogen bonding, while metal sites electrostatically interact with the lithium salt anions (TFSI − ), promoting Li salt dissociation and optimizing [Li(PC) x ] + solvation. Additionally, hydrogen bonding between PAN cyano‐groups and LDH creates continuous radial Li + pathways. The LDH@PAN SPE achieves high ionic conductivity (1.36 mS cm −1 ), Li + transference number (0.80 at 20°C), and a 4.9 V window. Li||Li symmetric cells cycle for 1600 h at 0.2 mA cm −2 with a critical current density of 1.8 mA cm −2 . LiFePO 4 ||Li full cells deliver excellent rate capability (110.2 mAh g −1 at 5 C) and long‐term cycling (81.3% retention after 1100 cycles at 1 C) at room temperature, alongside flexibility and flame retardancy. This work offers a new interfacial engineering and ion‐transport strategy for high‐performance solid‐state lithium metal batteries.