Fabrication of aluminum phosphate–coated silica: effect on mechanical properties, flame retardancy, and ionic conductivity of PEO composite electrolytes

Polymer solid-state electrolytes hold significant promise for all-solid-state lithium-ion batteries, but they also suffer from critical limitations including high flammability, low ionic conductivity, and poor mechanical properties. In this work, aluminum phosphate (AlPO 4 )-coated silica (SiO 2 ) (SiO 2 @AlPO 4 ) synergistic flame retardant was fabricated, and the influence of SiO 2 @AlPO 4 on the mechanical properties, the flame retardancy, and the ionic conductivity of poly(ethylene oxide) (PEO)/Li salt ionic conductor was studied. For PEO/Li/SiO 2 @AlPO 4 10 composite electrolyte, the strength and the modulus increased by 38.5% and 80.7%, respectively, compared with PEO/Li electrolyte, and the ionic conductivity almost was the highest among all samples in the entire temperature rang. For all PEO composite electrolytes, the limiting oxygen index (LOI) increased and the total heat release (THR) reduced with the increase of SiO 2 @AlPO 4 content. Results show that SiO 2 @AlPO 4 can not only improve the strength, the modulus, and the flame retardancy of PEO but also improve its ionic conductivity, the SiO 2 @AlPO 4 was demonstrated as an excellent synergistic filler for PEO solid-state electrolytes.