Integrated multicomponent design strategies to enhance the electrochemical performance of solid-state lithium metal batteries on interfacial stability of composite polymer electrolytes

All-solid-state lithium metal batteries (ASSLMBs) have emerged as attractive candidates for high-energy and safer energy-storage technologies. Nevertheless, their development is hindered by sluggish ion transport and unstable electrode–electrolyte interfaces. Although polymer electrolytes offer flexibility and good interfacial contact, their limited ionic conductivity and insufficient interfacial robustness remain critical challenges. Herein, we report a multifunctional composite polymer electrolyte (CPE) that simultaneously enhances ionic transport and interfacial stability via a synergistic, multiscale design. The electrolyte is fabricated through ultraviolet (UV)-induced polymerization of a crosslinked poly(ethylene glycol) diacrylate (PEGDA) network, plasticized by tetraethylene glycol dimethyl ether (TEGDME), and integrated with a dual-Li salt system (LiTFSI/LiDFOB). To further regulate the solvation structure and interfacial chemistry, polydopamine-modified ceramic fillers Li 6.4 La 3 Zr 2 Al 0.2 O 12 (PDA@LLZAO) and functional additives, including fluoroethylene carbonate (FEC), sulfolane (SUL), and Mg(TFSI) 2 , are incorporated. This integrated design effectively regulates both ionic transport and interfacial chemistry within the electrolyte system. As a result, the optimized CPE achieves an ionic conductivity of ∼1.81 × 10 −4 S cm −1 and a Li + transference number of ∼0.38 at room temperature. Moreover, the electrolyte shows a broadened electrochemical stability window approaching 5.21 V (vs. Li/Li + ), indicating good compatibility with high-voltage cathodes. The symmetric Li||Li cell demonstrates stable lithium plating/stripping for more than 600 h at 0.1 mA cm −2 /0.1 mAh cm −2 , while LiFePO 4 -based full cells maintain approximately 95% capacity retention after 600 cycles at room temperature. By simultaneously tailoring the solvation structure, polymeric matrix, and interfacial chemistry, the developed electrolyte platform offers a promising pathway for next-generation solid-state lithium metal batteries.