Composite gradient polymer electrolyte enables stable and rapid lithium-ion transport

Abstract Lithium metal batteries (LMBs) employing sulfurized polyacrylonitrile (SPAN) cathodes offer a compelling pathway toward high energy density, yet their practical application is strictly hindered by insufficient interfacial stability and ion-transport kinetics. While liquid electrolytes facilitate rapid kinetics, they suffer from severe safety risks and active species shuttling. Conversely, uniform gel or solid electrolytes often create a “kinetic bottleneck” at the cathode interface. Herein, we report a composite gradient polymer electrolyte (CGPE) that is engineered via a functionalized separator that spatially modulates the in-situ ring-opening polymerization (ROP) of 1,3-dioxolane (DOL). Raman spectroscopic mapping confirms a well-defined gradient architecture, in which a polymer-dense region at the separator side provides a physical barrier against polysulfide shuttling and dendrite penetration, while a solvent-rich, gel-like environment is preserved at the cathode interface to ensure conformal wetting and rapid desolvation. Consequently, the CGPE-based Li-SPAN cells demonstrate an exceptional rate capability, delivering a specific capacity of 139.9 mAh g –1 at an ultra-high rate of 10 C, while maintaining a capacity retention of 75.1% after 500 cycles at 2 C.