Preparation and Electrochemical Properties of Ba1-xLaxF2+x Fluoride Electrolyte

A series of Ba 1- x La x F 2+ x composition powders with different values of x were prepared by water and ethanol mixed solvent method. The effects of different values of x on the phase composition, crystal structure and electrochemical properties of Ba 1- x La x F 2+ x electrolyte were studied. The electrical conductivity of Ba 1- x La x F 2+ x at different temperatures was investigated by electrochemical impedance spectroscopy. The results of transmission electron microscopy showed that the prepared Ba 1- x La x F 2+ x powders ranged in size from 10 to 25nm and dominated by crystalline phases. XRD results show that the Ba 1- x La x F 2+ x electrolyte gradually changes from fluorite structure to tysonite structure with the increase of x value. Electrochemical impedance spectroscopy was used to study the electrical properties at 25, 50, 75, and 100°C. It was found that the ionic conductivity of the Ba 1- x La x F 2+ x electrolyte at the same temperature increased with the increase of temperature. When x is small, the main carrier of Ba 1- x La x F 2+ x electrolyte is F − . When x is too large, it mainly depends on F − vacancy conduction, while the conductivity of the former is lower at lower test temperature. The contribution is much larger than the latter, which is also the main reason for the decrease of conductivity of Ba 1- x La x F 2+ x electrolyte when x is too large. At the same temperature, Ba 0.6 La 0.4 F 2.4 is always the maximum conductivity.