CsH₂PO₄/polyvinylidene fluoride composite electrolytes for intermediate temperature fuel cells

In this study CsH₂PO₄/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 CsH₂PO₄ particles in the PVDF polymer network and were thin and flexible. The crystalline structure and thermal behavior of CsH₂PO₄ were not influenced by the PVDF. The composite electrolyte with 70 wt% CsH₂PO₄ showed a high conductivity of 10 mS cm^-1 at 270°C under 30% H₂O/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 cm², for corresponding thicknesses of 101 and 67 μm, which are low values. The composite electrolyte with 70 wt% CsH₂PO₄ showed stable conductivity at 259°C under 30% H₂O/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.