All-solid-state lithium secondary batteries using LiCoO 2 particles with pulsed laser deposition coatings of Li 2S–P 2S 5 solid electrolytes

Abstract

Electrode–electrolyte composite materials were prepared by coating a highly conductive Li 2S–P 2S 5 solid electrolyte onto LiCoO 2 electrode particles using pulsed laser deposition (PLD). Cross-sections of the composite electrode layers of the all-solid-state cells were observed using a transmission electron microscope to investigate the packing morphology of the LiCoO 2 particles and the distribution of solid electrolyte in the composite electrode. All-solid-state cells based on a composite electrode composed entirely of solid-electrolyte-coated LiCoO 2 were fabricated, and their performance was investigated. The coating amounts of Li 2S–P 2S 5 solid electrolytes on LiCoO 2 particles and the conductivity of the coating material were controlled to increase the capacity of the resulting all-solid-state cells. All-solid-state cells using LiCoO 2 with thick solid electrolyte coatings, grown over 120 min, had a capacity of 65 mAh g −1, without any addition of Li 2S–P 2S 5 solid electrolyte particles to the composite electrode. The capacity of the all-solid-state cell increased further after increasing the conductivity of the Li 2S–P 2S 5 solid electrolyte coating by heat treatment at 200 °C. Furthermore, an all-solid-state cell based on a composite electrode using both a solid electrolyte coating and added solid electrolyte particles was fabricated, and the capacity of the resulting all-solid-state cell increased to 95 mAh g −1.