In-Situ Polymerization Confined PEGDME-Based Composite Quasi-Solid-State Electrolytes for Lithium Metal Batteries

Solid-state lithium metal batteries are under development for higher energy density and better safety. A key is to develop new electrolyte systems that are readily processible and capable to improve electrochemical cycling stability. In this study, A quasi-solid-state composite electrolyte based on low-molecular-weight polyethylene glycol dimethyl ether (PEGDME) in situ confined within polymerized methyl methacrylate (PMMA) backbone is designed and presented. The new design of the polymer matrix, together with Li + -conducting ceramic fillers and appropriate lithium salts, has satisfactory Li-ionic conductivity (1.1 × 10 −4 S cm −1 at 30 C and 1.0 × 10 −3 S cm −1 at 80 °C), good electrochemical stability (>4.7 V vs Li + /Li), and high compatibility with lithium metal anode, enabling room-temperature operation and stable long-term cycling of both Li||Li symmetric cells and lithium-metal full cells (including LiFePO 4 or LiCoO 2 cathode). This work can extend the design boundaries of composite electrolytes meaningfully, and the idea of in situ polymerization limiting applies to almost all low-molecular-weight polymers, high-molecular-weight backbones, ceramic fillers, lithium salts, and additives in future development of room-temperature solid-state lithium metal batteries.