Designing electrolytes with high solubility of sulfides/disulfides for high-energy-density and low-cost K-Na/S batteries.

Alkaline metal sulfur (AMS) batteries offer a promising solution for grid-level energy storage due to their low cost and long cycle life. However, the formation of solid compounds such as MS and MS (M = Na, K) during cycling limits their performance. Here we unveil intermediate-temperature K-Na/S batteries utilizing advanced electrolytes that dissolve all polysulfides and sulfides (KS, x = 1-8), significantly enhancing reaction kinetics, specific capacity, and energy density.