A novel thermomechanically stable LaF3CsH5(PO4)2 composite electrolyte with high proton conductivity at elevated temperatures over 150 °C

Abstract

Abstract A facile strategy is introduced to upgrade thermomechanical stability of the cesium pentahydrogen diphosphate (CPD), which is the most efficient inorganic electrolyte among all solid proton conductors, by constructing P OH•••F hydrogen bonds with lanthanum fluoride (LaF3). The optimal combination of the LaF3 CPD composite electrolyte is found to be 1:2 in a molar ratio (LaF3 CPD-2). LaF3 CPD-2 composite maintains robust solid state, even at a temperature up to 200 °C, which is 50 °C higher than the melting temperature of CPD. Meanwhile, the considerable proton conductivity of CPD is achieved in the LaF3 CPD-2 composite electrolyte due to the synergistic effect of the P OH•••F hydrogen bonds and the intrinsic proton conductive property of CPD. Last but not least, the LaF3 CPD-2 composite manifests excellent conductivity durability at 150 °C and low humidity condition with sizeable proton conductivity of 0.0262 S cm−1 after 60 h operation, implying that the LaF3 CPD composite could be a promising candidate for intermediate temperature proton conductors.