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., TMδ+-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.