Precisely succinonitrile-functionalized PEO electrolytes toward room-temperature all-solid-state lithium batteries

Polyethylene oxide) (PEO) polymer electrolytes have the potential for the use in all-solid-state lithium-metal batteries (ASSLMBs). However, no effective rules have been proposed to prepare all-solid-state PEO electrolytes that overcome the limitation being unusable at room temperature. In this study, based on the polymer C–H functionalization strategy, we design a highly ion-conductive PEO electrolyte by directly covalently linking succinonitrile functional-groups with lithium coordination activity on the polymer chains. The functional-groups enhance the disorder and mobility of the PEO chains while acting as effective sites for the fast ionic-conduction in the interchain, thus achieving a dual optimization of the free volume around ions and the migration behavior. Due to the precise tuning by functional-groups, the functionalized electrolyte exhibits enhanced ionic conductivity (>10² times), high transference number (~0.51) and wide electrochemical window (~0.47 V). In particular, the functionalized PEO_300k electrolyte with a high ionic conductivity (1.01×10⁻⁴ S cm⁻¹ at 25°C) enables the stable operation at room temperature, providing a path for the development of polymer-based electrolytes with practical applications.