Cyano‐Driven Solvation Structure Reconstruction and Interfacial Passivation for 4.5 V Solid‐State Lithium Metal Batteries

ABSTRACT Solid polymer electrolytes hold great promise for high‐energy‐density lithium metal batteries, yet their practical implementation is still hindered by sluggish room‐temperature Li + transport and insufficient high‐voltage tolerance ( i.e ., unstable above 4.3 V) especially when coupled with Ni‐rich layered cathodes. Herein, we report a cyano‐coordinating strategy to reconstruct the Li + solvation environment by precisely regulating the content of cyanoacrylate adhesive. This abandonment of ether‐oxygen polymers as the main material, that is, the competitive Li + –C≡N coordination reorganizes the primary solvation shell of Li + . This regulated solvation sheath simultaneously provides continuous low‐barrier hopping sites of Li + and improves the oxidative stability of the electrolytes. More importantly, the strong coordination anchoring between −C≡N and transition‐metal cations ( i.e ., TM δ+ –N≡C), suppresses irreversible dissolution of transition‐metal cations during cycling. The Li//NCM811 cells retain 88.2% of their initial capacity after 500 cycles at 4.3 V and 3 C and 80.1% after 350 cycles at 4.5 V and 1 C. Meanwhile, the cells exhibited a high operating voltage over 3.85 V, showing great potential for high‐energy‐density solid‐state batteries. This study establishes molecular coordination reconstruction to synergistically regulate the solvation behavior and high‐voltage interfacial chemistry of polymer electrolytes, providing a general design rationale for high‐energy‐density and long‐life solid‐state lithium‐metal batteries.