Flame-retardant AEMs based on organic-inorganic composite polybenzimidazole membranes with enhanced hydroxide conductivity

Efficient anionic conductivity accompanied with flam-resistance is of great importance for solid electrolyte. Herein, anion exchange membranes (AEMs) based on polybenzimidazole (PBI) and 1-butyl-3-methyl imidazolium phosphotungstate (PWA-IL) have been prepared. The obtained PWA-IL can be dispersed in PBI matrix uniformly aiming to enhance the anion conductivity. Especially, it is found that PWA-IL endows the composite membranes with flame-resistance features. Such a phenomenon may be rooted from the nature of non-flammable of 1- butyl-3-methylimidazolium bis (trifluoromethylsulfony)imide (IL) and phosphotungstic acid (PWA), which constitute the organic-inorganic filler PWA-IL. Simultaneously, the anionic conductivity of the obtained composite membranes improved from 48.9 mS cm−1 to 75.8 mS cm−1 under fully hydrated conditions at 80 °C. Enlarged elongation and small decline in tensile strength was observed due to the plasticization from 1-butyl-3-methyl imidazolium phosphotungstate. Polybenzimidazole backbones provide tough mechanical properties (strength more than 60 MPa and elongation more than 6%) and good thermal stability, which meet the need of wide applications.