Fabrication of Nano‐<scp>CaSO₄</scp> From Phosphogypsum: Effect on the Mechanical, Flame Retardant, and Electrochemical Performance of <scp>PEO</scp> Solid Electrolytes

ABSTRACT Reusing phosphogypsum (PG) is of great significance as the negative effect of increasing PG pollution on the environment is now incontrovertible. Herein, nano‐CaSO 4 particles were fabricated using PG through a facile yet effective solvent‐thermal method, and their influence on the thermomechanical properties and electrochemical properties of polymeric solid electrolytes was further investigated. Results indicated that cubic nano‐CaSO 4 particles could be obtained by regulating the concentrations and types of surfactants and concentrations of H 2 SO 4 and HNO 3 . Furthermore, nano‐CaSO 4 fillers at a content of 10 wt.% could simultaneously improve the mechanical properties, flame retardancy, and ionic conductivity of polyvinyl oxide‐based solid electrolytes. Nano‐CaSO 4 (10 wt.%) could enhance the strength by two times and modulus by more than four times, improve the limiting oxygen index from 19.5% to 23.1%, reduce the total heat release rate from 17.9 to 16.2 kJ/g, and increase ionic conductivity by more than two times at 60°C. This study provides a facile yet economic strategy for fabricating cubic nano‐CaSO 4 using PG and exhibits an excellent utilization prospect for high‐safety all‐solid‐state batteries.