CsH₂PO₄/Polyvinylidene Fluoride Composite Electrolytes for Intermediate Temperature Fuel Cells

In this study CsH 2 PO 4 /polyvinylidene fluoride (PVDF) composite electrolytes were prepared by a slurry casting method and their application in intermediate temperature fuel cells (ITFCs) was investigated. The composite electrolytes consisted of a physical dispersion of CsH 2 PO 4 particles in the PVDF polymer network and were thin and flexible. The crystalline structure and thermal behavior of CsH 2 PO 4 were not influenced by the PVDF. The composite electrolyte with 70 wt% CsH 2 PO 4 showed a high conductivity of 10 mS cm −1 at 270°C under 30% H 2 O/Ar atmosphere as well as a tensile strength of 7 MPa at room temperature. In addition, the composite electrolytes had area specific resistances of 0.99 and 0.72 Ω cm 2 , for corresponding thicknesses of 101 and 67 μm, which are low values. The composite electrolyte with 70 wt% CsH 2 PO 4 showed stable conductivity at 259°C under 30% H 2 O/Ar atmosphere for 48 h. A fuel cell assembled with this electrolyte exhibited an open circuit voltage of 0.92 V and a peak power density of 86 mW cm −2 , making the composite electrolyte a candidate electrolyte for ITFCs.