Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility

Significance Sulfur as an anode coupled with a lithium-ion intercalation cathode in the superconcentrated aqueous electrolyte creates a unique Li-ion/sulfur chemistry, realizing the highest energy density ever achieved in aqueous batteries, along with high safety and excellent cycle-life. Mechanism investigation finds that the reversible sulfur lithiation/delithiation in such an aqueous electrolyte proceeds with fast kinetics that significantly differ from that in nonaqueous systems, whereas polysulfides’ insolubility in such an aqueous electrolyte essentially eliminates the parasitic shuttling. The excellent performances of Li-ion/sulfur cells not only find an application of “water-in-salt” electrolyte for beyond Li-ion chemistries, more importantly, an alternative pathway is provided to solve the “polysulfide shuttling” that has been plaguing the sulfur chemistries in nonaqueous electrolytes.