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