Phase‐Transition‐Promoted Interfacial Anchoring of Sulfide Solid Electrolyte Membranes for High‐Performance All‐Solid‐State Lithium Battery

Abstract Solvent‐free manufacturing is crucial for fabricating high‐performance sulfide‐electrolyte‐based all‐solid‐state lithium batteries (ASSLBs), with advantages including side reaction inhibition, less contamination, and practical scalability. However, the fabricated sulfide electrolytes commonly suffer from brittleness, limited ion transport, and unsatisfactory interfacial stability due to the uncontrolled dispersion of the sulfide particles within the polymer binder matrix. Herein, a “solid‐to‐liquid” phase transition strategy is reported to fabricate flexible Li 6 PS 5 Cl (LPSCl) electrolytes. The polycaprolactone (PCL)‐based binder (PLI) with phase‐transition characteristics fills the gap of LPSCl particles and tightly grafts on the particle surface via ion‐dipole interaction, bringing a thin and compact electrolyte membrane (80 µm). The simultaneously high Li‐ion conducting and electron insulating nature of PLI binder facilitates Li‐ion transport and ensures good interfacial stability between electrolyte and anode. Consequently, the sulfide electrolyte membrane exhibits high ionic conductivity (8.5 × 10 −4 S cm −1 ), enabling symmetric and full cells with 10 and 2.5 times longer cycling life compared with that of the cells with pristine LPSCl electrolyte, respectively. The demonstrated strategy is versatile and can be extended to ethylene vinyl acetate copolymer (EVA) that also brings enhanced electrochemical performance. The thin sulfide electrolyte with high interfacial stability potentially facilitates dendrite‐free ASSLBs with high energy density.