Incorporating Sodium‐Conductive Polymeric Interfacial Adhesive with Inorganic Solid‐State Electrolytes for Quasi‐Solid‐State Sodium Metal Batteries

Abstract Inorganic solid‐state electrolytes have attracted enormous attention due to their potential safety, increased energy density, and long cycle‐life benefits. However, their application in solid‐state batteries is limited by unstable electrode‐electrolyte interface, poor point‐to‐point physical contact, and low utilization of metallic anodes. Herein, interfacial engineering based on sodium (Na)‐conductive polymeric solid‐state interfacial adhesive is studied to improve interface stability and optimize physical contacts, constructing a robust organic‐rich solid electrolyte interphase layer to prevent dendrite‐induced crack propagation and security issues. The interfacial adhesive strategy significantly increases the room‐temperature critical current density of inorganic Na‐ion conductors from 0.8 to 3.2 mA cm−2 and markedly enhances the cycling performance of solid‐state batteries up to 500 cycles, respectively. Particularly, the Na3V2(PO4)3‐based full solid‐state batteries with high cathode loading of 10.16 mg cm−2 also deliver an excellent cycling performance, further realizing the stable operation of solid‐state laminated pouch cells. The research provides fundamental perspectives into the role of interfacial chemistry and takes the field a step closer to realizing practical solid‐state batteries.