In Situ Partial-Cyclized Polymerized Acrylonitrile-Coated NCM811 Cathode for High-Temperature ≥ 100 °C Stable Solid-State Lithium Metal Batteries

• Uniform and stable interfacial layer with both ionic and electronic conduction on the surface of solid-state composite cathode by in situ polymerization cyclization treatment. • Theoretical calculations demonstrate that cPAN can effectively inhibit transition metal dissolution and uneven cyclic stress distribution and improve the stability of the crystal structure. • In-cPAN-260@NCM811 has excellent cycling performance with 86.8% retention after 300 cycles and thermally safe stability at high-temperature extremes. • The facile and scalable surface engineering approach represents significant progress in developing high-performance solid-state lithium metal batteries.