Preparation and characterization of thermally stable proton-conducting composite sheets composed of phosphosilicate gel and polyimide

Thermally stable proton-conducting composite sheets of 50–100 μm thick have been prepared from phosphosilicate gel (P/Si=1 molar ratio) powders and polyimide precursor. The proton conductivity of the composite sheet increased with an increase in the phosphosilicate gel content. The composite sheet containing 70 wt.% of the gel showed a tensile strength of about 170 N cm−2 at 150 °C and a conductivity of 2×10−4 S cm−1 at 150 °C and 0.4% relative humidity (RH). The open circuit potential of the test cell using the composite sheet as an electrolyte was about 0.9 V at 30 °C and 60% RH, and the power density was maximized to be about 30 mW cm−2 at around 90 mA cm−2.