Self-assembled non-flammable poly(arylene ether sulfone)-grafted poly(ethylene glycol) solid electrolyte with improved lithium-ion transport for lithium–sulfur batteries

The advancement of lithium–sulfur batteries (LSBs) is impeded by issues such as polysulfide dissolution, flammability, and limited lithium-ion transport in conventional liquid electrolytes. This study addresses these challenges by developing a self-assembled solid polymer electrolyte based on poly(arylene ether sulfone)-graft-poly(ethylene glycol) (PAES-g-PEG), combined with a trimethyl phosphate (TMP) and ethylene carbonate (EC) co-solvent system. The PAES-g-PEG spontaneously forms nanostructured domains, where PAES-rich regions impart mechanical robustness and PEG-rich regions provide efficient Li-ion transport pathways. The 6:4 TMP–EC ratio is identified as optimal, achieving high ionic conductivity (1.58 mS cm⁻¹ at 30 °C), a high Li-ion transference number (t_Li⁺ = 0.614), and low interfacial resistance (890 Ω), while maintaining excellent flame retardancy and thermal stability (>300 °C). The solid-state membrane also demonstrates enhanced flexibility, interfacial stability with Li metal, and a wide electrochemical window (4.84 V). When applied in LSBs, the PAES-g-PEG membrane supports high sulfur utilization (∼950 mAh g⁻¹ at 0.2 C) and stable cycling, even at elevated rates and temperatures. These results highlight the potential of microphase-separated, flame-retardant polymer electrolytes for enabling safe, high-performance solid-state LSBs and contribute to the development of next-generation energy storage technologies.