Preparation of an Amorphous 80LiCoO₂·20Li₂SO₄ Thin Film Electrode by Pulsed Laser Deposition

Abstract

An amorphous 80LiCoO₂·20Li₂SO₄ (mol%; Li_1.2Co_0.8S_0.2O_2.4) thin film electrode is prepared by pulsed laser deposition (PLD). Although the Li_1.2Co_0.8S_0.2O_2.4 electrode material has been synthesized via mechanochemistry and includes a cubic LiCoO₂ crystalline phase, amorphous Li_1.2Co_0.8S_0.2O_2.4 (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 Li_1.2Co_0.8S_0.2O_2.4 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 Li_1.2Co_0.8S_0.2O_2.4, which partially includes electrochemically-inactive cubic LiCoO₂ nanoparticles. It is noted that complete amorphization of Li_1.2Co_0.8S_0.2O_2.4 is effective in increasing reversible capacities.