In Situ Cross-Linked Solid Polymer Electrolytes with Synergistic Dissociation–Coordination Modulation for Stable Solid-State Lithium Batteries

Abstract Solid polymer electrolytes possess excellent flexibility and superior interface compatibility, which can effectively adapt to electrode volume changes and reduce interface resistance. However, they are impeded by the intrinsic incompatibility between lithium salt dissociation and Li+ coordination, along with the unavoidable trade-off between mechanical durability and Li+ conductive kinetics. To address this, an in situ multifunctional cross-linked copolymer electrolyte (TGDODT) is constructed. The crosslinking center promotes the dissociation of lithium salts to deliver more free Li+, while the thioether segment provides weak coordination with Li+ to reduce the transport barrier. Moreover, the cross-linked network ensures excellent mechanical/thermal stability and provides a three-dimensional continuous Li+ diffusion channel. Therefore, this collaborative design provides a Li+ transport highway, induces a stable inorganic SEI to suppress lithium dendrites, and provides flame retardancy. As a result, the TGDODT electrolyte shows high ionic conductivity (1.31 × 10–4 S cm–1), a high Li+ transference number (0.75), and exceptional electrode compatibility. Li||TGDODT||LFP batteries show great cycling stability after 660 cycles at 1 C with 88.2% capacity retention. This study demonstrates a coherent design principle for integrating mechanical stability, rapid ion transport, and interfacial safety, providing a promising avenue for developing high-performance solid-state lithium metal batteries.