Flame-Retardant ADP/PEO Solid Polymer Electrolyte for Dendrite-Free and Long-Life Lithium Battery by Generating Al, P‑rich SEI Layer

The poly­(ethylene oxide) solid polymer electrolyte (PEO SPE) has recently received much attention, however, the organic components in the SPE are still flammable. In this paper, we find that the high efficiency halogen-free aluminum (Al) diethyl hypophosphite flame retardant (ADP) is effective in reducing the flammability of PEO SPE. The SEI layer containing Al and phosphorus (P) inhibits the growth of lithium dendrite and enhances the cycle life of the battery. The capacity of a LiFePO₄/SPE/Li battery containing ADP is still 123.2 mAh g^–1 at 1.0 C and the Coulombic efficiency is as high as 99.95% after 1000 cycles (60 °C). At the same time, Al, P-rich SEI can inhibit the growth of lithium dendrite and the cycle stability of the battery is further enhanced.