Novel Nanohybrid Expandable Graphite Flame Retardant on Enhancing the Fire Safety and Conductivity of Poly(Vinyl Alcohol) Solid Electrolytes

Obtaining a good balance between fire safety and conductivity in a poly(vinyl alcohol) (PVA)-based solid electrolyte still faces an enormous challenge, primarily due to the flammability and lower conductivity of the PVA material. Herein, to address this concern, a nano novel silica@expandable graphite (SiO2@EG) hybrid was fabricated by a hydrothermal method, showcasing a promising potential in constructing flame retardant and conductive polyaniline@PVA (PANI@PVA) composite films. The impact of the SiO2@EG hybrid with different hybridization ratios on the structure, flame retardancy, and conductivity of PANI@PVA composite films was investigated in detail. Good compatibility between SiO2@EG and PANI@PVA is observed based on the results of scanning electron microscopy (SEM). Remarkably, PANI@PVA composite films with only 15 phr SiO2@EG2 raise the limiting oxygen index (LOI) of PANI@PVA to 59.2%. Additionally, PANI@PVA/SiO2@EG composite films cannot be ignited during combustion testing, indicating the excellent flame retardancy. Subsequently, the electrical conductivity of PANI@PVA/SiO2@EG2 composite films with 15 phr SiO2@EG2 increases to 150.54 S/m from 11.09 S/m of PANI@PVA composite films. Notably, PANI@PVA/SiO2@EG2 composite films also exhibit excellent mechanical flexibility. In short, this work provides a new perspective for scientific research or industry in the investigation of EG flame retardants for solid polymer electrolytes.