Alginate Fiber-Grafted\nPolyetheramine-Driven High\nIon-Conductive and Flame-Retardant Separator and Solid Polymer Electrolyte\nfor Lithium Metal Batteries

Traditional polymer-based separators and solid polymer\nelectrolytes\n(SPEs) often suffer from inherent poor flame retardancy and unsatisfied\nionic conductivity, which seriously affect the safety and energy storage\nperformance of lithium metal batteries (LMBs). Inspired by the mechanism\nof Li⁺ conductivity, an alginate fiber (AF)-grafted polyetheramine\n(AF-PEA) separator with efficient Li⁺ transport and excellent\nflame retardancy is dedicatedly designed, which also can act as the\nbackbone for PEO-based SPEs (PEO@AF-PEA). Based on the intrinsic flame\nretardancy of the AF, the AF-PEA shows self-extinguishing ability,\nand its Li⁺ transport ability (1.8 mS cm^–1 at 25 °C) is enhanced by grafting the ion-conductive PEA chain\nsegment. By simulating the transport and distribution of Li⁺ in the AF-PEA, the PEA with 7-segment chain lengths can uniformly\nfill the Li⁺ transport space between the alginate backbone\nto promote the Li⁺ adsorption and the utilization of Li⁺ anchoring points in PEA side chains, increasing the Li⁺ transport rate and migration capacity. The LiFePO₄/Li solid-state battery assembled using PEO@AF-PEA SPEs exhibits\nhigh safety and excellent cycling performance (exceeding 100 mAh g^–1 after 1500 cycles at 2 C current density and 80 °C\nwith less than 0.016% capacity decay for each cycle).