Development of nitrogen-containing sulfide solid electrolytes with high ionic conductivity and water resistance

In general, sulfide-type solid electrolytes exhibit superior ionic conductivity among inorganic solid electrolytes but have low water resistance. The objective of this study was to develop sulfide-type solid electrolytes with superior ionic conductivity and water resistance using nitrides. Among sulfide-type solid electrolytes, the 70Li 2 S·30P 2 S 5 glass-ceramic (GC) has high Li-ion conductivity but poor stability against moisture. In this study, composite solid electrolytes containing this GC and Li 3 AlN 2 were prepared to improve stability against moisture while maintaining high ionic conductivity. GC solid electrolytes with the composition (100– x )(0.70Li 2 S·0.30P 2 S 5 )· x Li 1.5 Al 0.5 N were synthesized via mechanical milling and consecutive heat treatment above their crystallization temperatures. The 80(0.70Li 2 S·0.30P 2 S 5 )·20Li 1.5 Al 0.5 N (LPASN20) GC exhibited a conductivity of 1.7 mS cm −1 at 25 °C and excellent stability against moisture. Compositions with halide substitutions in the LPASN20 GC were investigated to increase ionic conductivity. The 80{0.80(0.70Li 2 S·0.30P 2 S 5 )·0.20Li 1.5 Al 0.5 N}·12LiBr·8LiI (LPASNBrI) GC exhibited a superior conductivity of 4.7 mS cm −1 at 25 °C and excellent stability against moisture. The charge–discharge performance of an LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode with the LPASNBrI GC was evaluated. The LPASNBrI GC was sufficiently stable for application to NCM cathodes, featuring superior ionic conductivity and excellent chemical stability. • Sulfide solid electrolytes with high ionic conductivity and water resistance. • Stability against moisture improved while maintaining high ionic conductivity. • Glass-ceramic with high ionic conductivity and excellent chemical stability. • New possibility for nitride substitution in sulfide solid electrolytes.