Protecting Li Metal Anode While Suppressing “Shuttle Effect” of Li-S Battery Through Localized High-Concentration Electrolyte

Li-S batteries are widely studied due to their superior theoretical energy density. However, the “shuttle effect” on the cathode and the unstable Li metal anode hinder their practical application. During cycling, the “shuttle effect” leads to severe self-discharge and accelerates the capacity decay. Moreover, the shuttled polysulfides aggravate the growth of dendrites and the loss of Li, causing a low Coulombic efficiency. Considering electrolyte plays a crucial role in the polysulfides solvation behavior and solid electrolyte interphase (SEI)-formation process, a well-designed electrolyte is required. Here, we report a local high-concentration electrolyte for Li-S batteries. This electrolyte is prepared by adding “diluent” 1,1,2,2-tetrafluoroethyl methyl ether (TME) to the conventional electrolyte. The reduction of free solvent in the Li-ion solvation sheath suppresses the dissolution of the polysulfides, and more anion-derived SEI can be formed. Our work simultaneously restrains the “shuttle effect” of the cathode and builds a stable SEI on the anode to protect the Li metal. Without any LiNO3 additive, the average Coulombic efficiency of the Li anode can reach 98.87% after 120 cycles, and Li-S batteries with superior capacity retention of 60% after 400 cycles at 0.5 C can be achieved.