Organoboron- and Cyano-Grafted Solid Polymer Electrolytes Boost the Cyclability and Safety of High-Voltage Lithium Metal Batteries

Solid-state polymer electrolytes (SPEs) are deemed as a class of sought-after candidates for high-safety and high-energy-density solid-state lithium metal batteries, but their low ionic conductivity, narrow electrochemical windows, and severe interfacial deterioration limit their practical implementations. Herein, an organoboron- and cyano-grafted polymer electrolyte (PVNB) was designed using vinylene carbonate as the polymer backbone and organoboron-modified poly(ethylene glycol) methacrylate and acrylonitrile as the grafted phases, which may facilitate Li-ion transport, immobilize the anions, and enlarge the oxidation voltage window; therefore, the well-tailored PVNB exhibits a high Li-ion transference number (tLi+ = 0.86), a wide electrochemical window (>5 V), and a high ionic conductivity (σ = 9.24 × 10–4 S cm–1) at room temperature (RT). As a result, the electrochemical cyclability and safety of the Li|LiFePO4 and Li|LiNi0.8Co0.1Mn0.1O2 cells with in situ polymerization of PVNB are substantially improved by forming the stable organic–inorganic composite cathode electrolyte interphase (CEI) and the Li3N–LiF-rich solid electrolyte interphase (SEI).