Influence of annealing on ionic transfer and storage stability of Li2S-P2S5 solid electrolyte

In this study, the impact of annealing treatment on the ionic transfer and storage stability of 70Li2S-30P2S5 glass-ceramic solid electrolyte (SE) pellets are investigated. The ionic conductivity is enhanced from 1 to 1.5 mS cm−1, while the total interfacial resistance of Li/SE/Li cell is reduced by over an order of magnitude with increasing annealing temperature up to 250 °C. Higher annealing temperature induced formation of a low conductivity Li4P2S6 phase, which increased ionic and interfacial resistances. Storage stability is also improved by annealing treatments. Preparation of exemplary Li4Ti5O12 (LTO) electrodes involving mechanical milling with SE particles undesirably induces formation of a TiS2 phase at the interfaces. Annealing the cells at 250 °C induces further reaction between LTO and SE, increasing TiS2 content and reducing cell rate performance. High reactivity between metal oxides and sulfide-based SE may be an obstacle for the preparation of high performance rechargeable solid state Li ion batteries.