Air-stable, high-conduction solid electrolytes of arsenic-substituted Li4SnS4

Abstract

Lithium-ion-conducting solid electrolytes show promise for enabling high-energy secondary battery chemistries and solving safety issues associated with conventional lithium batteries. Achieving the combination of high ionic conductivity and outstanding chemical stability in solid electrolytes is a grand challenge for the synthesis of solid electrolytes. Herein we report the design of aliovalent substitution of Li₄SnS₄ to achieve high conduction and excellent air stability based on the hard and soft acids and bases theory. The solid electrolyte of composition Li_3.833Sn_0.833As_0.166S₄ has a high ionic conductivity of 1.39 mS cm⁻¹ at 25 °C. Considering the high Li⁺ transference number, this phase conducts Li⁺ as well as carbonate-based liquid electrolytes. This research also addresses the compatibility of the sulfide-based solid electrolytes through chemical passivation.