A three‐way electrolyte with ternary solvents for high‐energy‐density and long‐cycling lithium–sulfur pouch cells

Abstract Lithium–sulfur (Li–S) batteries promise high‐energy‐density potential to exceed the commercialized lithium‐ion batteries but suffer from limited cycling lifespan due to the side reactions between lithium polysulfides (LiPSs) and Li metal anodes. Herein, a three‐way electrolyte with ternary solvents is proposed to enable high‐energy‐density and long‐cycling Li–S pouch cells. Concretely, ternary solvents composed of 1,2‐dimethoxyethane, di‐isopropyl sulfide, and 1,3,5‐trioxane are employed to guarantee smooth cathode kinetics, inhibit the parasitic reactions, and construct a robust solid electrolyte interphase, respectively. The cycling lifespan of Li–S coin cells with 50 µm Li anodes and 4.0 mg cm−2 sulfur cathodes is prolonged from 88 to 222 cycles using the three‐way electrolyte. Nano‐heterogeneous solvation structure of LiPSs and organic‐rich solid electrolyte interphase are identified to improve the cycling stability of Li metal anodes. Consequently, a 3.0 Ah‐level Li–S pouch cell with the three‐way electrolyte realizes a high energy density of 405 Wh kg−1 and undergoes 27 cycles. This work affords a three‐way electrolyte recipe for suppressing the side reactions of LiPSs and inspires rational electrolyte design for practical high‐energy‐density and long‐cycling Li–S batteries.