In Situ Network Electrolyte Based on a Functional Polymerized Ionic Liquid with High Conductivity toward Lithium Metal Batteries

A solid-state electrolyte has attracted great interest on energy storage and conversion, especially for lithium metal batteries (LMBs). However, its practical application is limited by poor ionic conductivity at room temperature and dendrite formation. Herein, a polymerized ionic liquid (PIL)-based solid electrolyte with the structure of a semi-interpenetrating polymer network is designed to enhance the ionic conductivity for LMBs. A one-step in situ cross-link [Vmim1O2]­[TFSI] is introduced in the poly­(vinylidene fluoride)–hexafluoropropylene matrix to fabricate the electrolyte. The obtained solid electrolyte exhibits a high ionic conductivity (1.06 × 10^–3 S cm^–1 at 25 °C) and a wide electrochemical window (5.50 V vs Li/Li⁺). The assembled lithium symmetrical cell can maintain a stable voltage range over 1000 h, and the mechanism is confirmed by density functional theory calculations. The employed MD simulations indicate a coordination of the TFSI^– anion with both Li⁺ and the polycation in different systems and demonstrate the feasibility of the Li⁺ transport improvement based on the PIL. Li/LiFePO₄ batteries also show good cycle performance whose reversible capacity is about 153.7 mA h g^–1 with 96.53% Coulombic efficiency at 0.1 C and 25 °C. This research shows that this PIL-based solid electrolyte possessed broad application for next-generation LMBs.