Alginate Fiber-Grafted Polyetheramine-Driven High Ion-Conductive and Flame-Retardant Separator and Solid Polymer Electrolyte for Lithium Metal Batteries

Traditional polymer-based separators and solid polymer electrolytes (SPEs) often suffer from inherent poor flame retardancy and unsatisfied ionic conductivity, which seriously affect the safety and energy storage performance of lithium metal batteries (LMBs). Inspired by the mechanism of Li+ conductivity, an alginate fiber (AF)-grafted polyetheramine (AF-PEA) separator with efficient Li+ transport and excellent flame retardancy is dedicatedly designed, which also can act as the backbone for PEO-based SPEs (PEO@AF-PEA). Based on the intrinsic flame retardancy of the AF, the AF-PEA shows self-extinguishing ability, and its Li+ transport ability (1.8 mS cm–1 at 25 °C) is enhanced by grafting the ion-conductive PEA chain segment. By simulating the transport and distribution of Li+ in the AF-PEA, the PEA with 7-segment chain lengths can uniformly fill the Li+ transport space between the alginate backbone to 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 high safety and excellent cycling performance (exceeding 100 mAh g–1 after 1500 cycles at 2 C current density and 80 °C with less than 0.016% capacity decay for each cycle).