An encapsulating lithium-polysulfide electrolyte for practical lithium–sulfur batteries

Practical lithium–sulfur batteries are severely hindered by parasitic reactions between lithium metal anodes and soluble lithium polysulfide (LiPS) intermediates. The solvation structure of LiPSs is pivotal in dictating the reaction kinetics. Herein, an encapsulating LiPS electrolyte (EPSE) is proposed to suppress parasitic reactions based on a nano-heterogeneous solvation structure design of LiPSs. In EPSE, with di-isopropyl sulfide (DIPS) as a co-solvent, soluble LiPSs are encapsulated into two concentric solvent shells with different solvating power and reduction stability. Reduction-stable DIPS in the outer solvent shell significantly suppresses the parasitic reactions between encapsulated LiPSs and lithium metal. A 1.2 Ah pouch cell under demanding conditions undergoes 103 cycles in the EPSE. This work provides two crucial criteria for constructing EPSE, that is, poor solvating power and high reduction stability of the solvent in outer solvent shell, and it opens up new frontiers in modulating the solvation structure of LiPSs toward long-cycling lithium–sulfur batteries.