Poly( Ethylene Oxide)-Based Solid Polymer Electrolytes for Solid-State Sodium Ion Batteries

One of the most promising candidates for large-scale energy storage applications is the solid-state sodium ion battery, which replaces conventional organic liquid electrolytes with solid electrolytes and has the advantages of high safety, high energy density, and extended cycle life. Among many solid electrolyte materials, Poly ( ethylene oxide) ( PEO )-based polymer solid electrolytes are considered promising solid electrolyte materials because of their high safety, easy manufacturing, low cost, high energy density, favorable electrochemical stability, and excellent solubility in sodium salts. However, the high crystallinity of the ethylene oxide (EO) chain segment results in low ionic conductivity at room temperature, which is unable to meet the requirements of practical application. To overcome the aforementioned limitations, researchers have used a variety of strategies to lessen the crystallinity of PEO-based polymer electrolyte and hence increase its ionic conductivity. Common techniques include polymer block copolymerization, blending, crosslinking, adding plasticizers, and adding inorganic fillers. In the review, the physical and chemical properties, preparation methods, and modification techniques of PEO-based polymer electrolytes are evaluated, and the most recent advancements on PEO-based polymer electrolytes are reviewed.