CsH2PO4/Epoxy Composite Electrolytes for Intermediate Temperature Fuel Cells

In this study CsH2PO4/epoxy composite electrolytes were prepared by dispersing CsH2PO4 particles, whose sizes were smaller than 10 μm, in a low-viscosity heat-resistant epoxy resin. The epoxy polymerization was promoted by thermal curing. The composite electrolyte consisted of a physical dispersion of CsH2PO4 particles in the cross-linked epoxy matrix. The polymerized epoxy showed a high thermal stability with no weight loss or phase transformation up to 290 °C. The composite electrolyte with 80 wt% CsH2PO4 showed a high conductivity of 11 mS cm−1 at 259 °C under 30% H2O/Ar atmosphere as well as a flexural strength of 7.3 MPa at room temperature. The composite electrolyte with 80 wt% CsH2PO4 showed a stable conductivity at 259 °C under 30% H2O/Ar atmosphere for 50 h. A fuel cell assembled with this electrolyte exhibited an open circuit voltage of 0.95 V and a peak power density of 38 mW cm−2. In addition, the fuel cell produced an output voltage higher than 0.44 V during a 6 h test under an output current density of 70 mA cm−2 with humidified H2 as the fuel and humidified O2 as the oxidant.