Fabrication of electrode–electrolyte interfaces in all-solid-state rechargeable lithium batteries by using a supercooled liquid state of the glassy electrolytes

Abstract

The softening behavior of a 80Li₂S·20P₂S₅ (mol%) glass electrolyte was investigated and a favorable electrode–electrolyte interface was fabricated by sticking the supercooled liquid state of the 80Li₂S·20P₂S₅ electrolyte on active material particles. A dense pellet of the glass electrolyte without an obvious grain boundary or any voids was prepared by softening the 80Li₂S·20P₂S₅ glass by means of a hot press. The electrical conductivity of the pellet was 8.8 × 10⁻⁴ S cm⁻¹ at room temperature. Sticking the solid electrolyte on the Li₄Ti₅O₁₂ active material particles increased the contact area at the electrode–electrolyte interface and the utilization of the active material was increased in the all-solid-state cells. However, LiCoO₂ reacted with the solid electrolyte during the hot press and the electrochemical performance of the cells using hot-pressed LiCoO₂ with the glass electrolyte degraded. LiNbO₃ coating suppressed the reaction of LiCoO₂ with the solid electrolyte. The all-solid-state full-cell Li₄Ti₅O₁₂/80Li₂S·20P₂S₅ glass/LiNbO₃-coated LiCoO₂ prepared by hot press showed a larger reversible capacity of 120 mAh g⁻¹ at 0.064 mA cm⁻² compared with the full-cell prepared by cold press. The softening of the 80Li₂S·20P₂S₅ glass electrolyte is an effective way for increasing the contact area between the active materials and solid electrolyte.