The thermal stability, local structure and electrical properties of lithium-iron phosphate glasses
Résumé
Amorphous analogues of lithium-iron phosphates (LFP), which are promising cathode materials for Li ion batteries, were prepared by the standard press-quenching method and their thermal stability, as well as structural and electrical properties, were studied for the first time. The glass transition temperature, Tg, determined by the differential thermal analysis (DTA) is composition-dependent and lies in the 492–523 °C range. The local structure, studied by the FTIR absorption spectroscopy, and the thermal stability are found to be almost insensitive to the lithium content. Studies on the electrical properties, carried out by impedance spectroscopy, have shown that the total electrical (predominantly polaronic) conductivity at 450 °C approaches 10–2 S·cm–1. The room temperature conductivity of samples after their nanocrystallization (induced by annealing at the temperature of the beginning of crystallization) was higher by a factor of 4–10 (depending on composition) than that of the as-received glass. Therefore, nanocrystallization seems to be a promising way to enhance the electrical conductivity of amorphous lithium-iron phosphates.