Preparation of an amorphous 80LiCoO2·20Li2SO4 thin film electrode by pulsed laser deposition

Abstract

An amorphous 80LiCoO2·20Li2SO4 (mol%Li1.2Co0.8S0.2O2.4) thin film electrode is prepared by pulsed laser deposition (PLD). Although the Li1.2Co0.8S0.2O2.4 electrode material has been synthesized via mechanochemistry and includes a cubic LiCoO2 crystalline phase, amorphous Li1.2Co0.8S0.2O2.4 (without the cubic phase active material) is successfully obtained using the PLD method. The atomic ratio of Li/Co in the obtained film as determined by ICP-AES is identical to that of the milled powder. X-ray photoelectron spectroscopy reveals that the thin film mainly contains Co3+ and SO42-. The amorphous Li1.2Co0.8S0.2O2.4 thin film electrode is directly deposited on the 90Li3BO3·10Li2SO4 (mol%) oxide electrolyte to form closely-attached electrode-electrolyte interface. The fabricated all-solid-state cells shows a higher discharge capacity than the cell fabricated using the electrode derived from the mechanochemically prepared Li1.2Co0.8S0.2O2.4, which partially includes electrochemically-inactive cubic LiCoO2 nanoparticles. It is noted that complete amorphization of Li1.2Co0.8S0.2O2.4 is effective in increasing reversible capacities.