Preparation of Composites with LiCoPO₄ Electrode and LiTi₂(PO₄)₃ Electrolyte for Bulk-type All-solid-state Lithium Batteries

Abstract

All-solid-state cells with LiCoPO₄ (LCP) active material with high redox potential of 4.8 V (vs. Li⁺/Li) were fabricated and the cells operated as a lithium secondary battery at room temperature. The composite electrodes of LCP active material and LiTi₂(PO₄)₃ (LTP) electrolyte with large contact area were synthesized in the media of oleic acid and paraffin wax by heat treatment at 700°C. The prepared LCP-LTP-Acetylene black (AB) composites were applied to electrochemical cells with a conventional organic liquid electrolyte and a sulfide solid electrolyte. The all-solid-state cells using the positive electrode composed of the LCP-LTP-AB composite and the sulfide electrolyte showed the initial discharge capacity of 50 mAh g⁻¹ at 4.8 V (vs. Li⁺/Li). The cells using the electrodes without LTP and the sulfide electrolyte were difficult to operate, suggesting that formation of close contacts between LCP and LTP, and additional ion conduction paths to LCP-LTP particles are effective in increasing capacities in all-solid-state cells.