Research progress on polymer solid-state electrolytes for high-safety lithium-ion batteries

【Objective】The rapid advancement of electric vehicles and energy storage technologies has heightened the demand for high-safety lithium-ion batteries. Conventional liquid electrolytes are volatile, flammable, and thermally unstable, posing severe safety risks under extreme conditions. Solid-state electrolytes, particularly polymer-based systems, offer enhanced thermal stability, mechanical robustness, and improved interfacial compatibility. This review aims to systematically summarize recent progress in polymer solid-state electrolytes for high-safety lithium-ion batteries, with a focus on their safety enhancement mechanisms, initiator-based in situ polymerization strategies, and self-polymerizing electrolyte systems.
【Method】This review surveys the literature on polymer solid-state electrolytes, emphasizing three key aspects: (1) The fundamental mechanisms by which polymer electrolytes improve battery safety, including thermal stabilization, lithium dendrite suppression, and interfacial stabilization. (2) The design and application of initiator-based in situ polymerization systems, categorized into thermal, photo, and redox initiation methods. (3) Emerging self-polymerization approaches that operate without external initiators, including lithium salt-induced ring-opening polymerization and electrochemically triggered polymerization.
【Result】Polymer solid-state electrolytes significantly mitigate thermal runaway risks through multiple synergistic mechanisms. The incorporation of thermally stable polymer backbones, functional groups , and three-dimensional crosslinked networks enhances thermal stability and flame retardancy. High mechanical modulus and anion-immobilizing structures effectively suppress lithium dendrite growth. In situ polymerization using thermal initiators or photoinitiators enables the formation of intimate electrode/electrolyte interfaces, improving cycling stability and delaying thermal runaway. Self-polymerizing systems, such as LiPF₆-induced ring-opening polymerization of 1,3-dioxolane, achieve high ionic conductivity and stable interface formation without exogenous initiators, simplifying fabrication and enhancing safety.
【Conclusion】Polymer solid-state electrolytes represent a promising pathway toward high-safety lithium-ion batteries. While significant progress has been made in enhancing ionic conductivity and interfacial stability through in situ and self-polymerization strategies, challenges remain in precisely controlling the reactivity of liquid precursors prior to polymerization. Future research should focus on developing low-reactivity, high-stability precursors that can be polymerized under mild conditions after cell assembly, thereby improving both safety and processability for practical applications.