High-Performance Alginate-Poly(ethylene oxide)-Based Solid Polymer Electrolyte

Solid polymer electrolytes (SPEs) have gained tremendous attention because they are expected to solve the safety problems caused by liquid electrolytes. However, the low ion-transport capacity, insufficient mechanical strength, and unsatisfying flame-retardant properties greatly limit their further application. Here, we designed a poly(ethylene oxide) (PEO)-based SPE by introducing a calcium alginate (CA) nanofiber membrane obtained by electrospinning as a framework. The abundant C═O and -OH groups in the CA macromolecules not only effectively weakened the coordination environment of lithium ions (Li⁺) but also promoted the dissociation of LiTFSI, assisting in the transfer of Li⁺ along PEO polymer chains and providing an effective pathway for Li⁺ transfer. The introduction of calcium ions (Ca⁺) during the cross-linking process improved the flame-retardant property of the SPE. The obtained SPE exhibited a high ion conductivity (3.86 × 10^-4 S cm^-1, 30 °C), excellent mechanical strength (2.01 MPa), and a wide electrochemical window (5.32 V). The assembled lithium-symmetric battery could undergo stable lithium plating/stripping for 3000 h at 30 °C. Meanwhile, LiFePO₄ (LFP)/Li all-solid-state lithium metal battery showed excellent cycle stability over 300 cycles with a high discharge capacity (141.2 mAh g^-1) and retention rate (92.5%) at 0.3 and 30 °C.