Structure, ionic conductivity and electrochemical stability of Li2S–P2S5–LiI glass and glass–ceramic electrolytes

The structures, ionic conductivities and electrochemical stabilities of the (100 − x)(0.7Li2S·0.3P2S5)·xLiI glass and glass–ceramic electrolytes were investigated. The (100 − x)(0.7Li2S·0.3P2S5)·xLiI glasses and glass–ceramics were prepared by mechanical milling in the composition range 0 ≤ x (mol%) ≤ 20. All the glasses and glass–ceramics had P2S74 − and PS43 − ions. The Li7P3S11 crystals were observed in all the glass–ceramics. On the other hand, crystals containing PS43 − ions were mainly precipitated in the glass–ceramics with increasing the LiI content. The conductivities of glasses increased with increasing the LiI content, and the glass at x = 20 showed the highest conductivity of 5.6 × 10− 4 S cm− 1. While the conductivity of glass–ceramics at x = 0 was 4.2 × 10− 3 S cm− 1, it decreased sharply with increasing the LiI content. Cyclic voltammetry indicated that the 80(0.7Li2S·0.3P2S5)·20LiI glasses exhibited a wide electrochemical stability up to 10 V vs. Li+/Li.