DTA, FTIR and impedance spectroscopy studies on lithium-iron-phosphate glasses with olivine-like local structure

Amorphous analogs of lithium-iron-phosphates (LFP) with olivine-like local order were prepared by standard press-quenching method and their thermal stabilities as well as structural and electric properties were studied for the first time. Glass transition temperature T, determined by DTA method is equal to 492-523 degrees C depending on the glass composition. Fourier transform infrared (FTIR) absorption spectroscopy was used to study local order. Local structure and thermal properties are almost independent on the lithium content. Electrical properties were studied by impedance spectroscopy. Impedance measurements indicated that the studied lithium-iron-phosphate glasses with olivine-like local order exhibit predominantly electronic (polaronic) conductivity. Total electrical conductivity at 450 degrees C for a glass of nominal composition LiFePO4 approaches 10(-2) S/cm. Electrical conductivity at 25 degrees C of Li0.4FePO4 glass after nanocrystallization (caused by heating up from room temperature to the beginning of crystallization temperature) increased by a factor close to 4. Nanocrystallization seems to be the way for electrical conductivity improvement of olivine-like cathode materials. (c) 2008 Elsevier B.V. All rights reserved.