Initiating a Reversible Aqueous Zn/Sulfur Battery through a “Liquid Film”

Sulfur cathodes have been under intensive study in various systems, such as Li/S, Na/S, Mg/S, and Al/S batteries. However, to date, Zn/S chemistry has never been reported. The first reliable aqueous Zn/polysulfide system activated by a “liquid film” comprising 4-(3-butyl-1-imidazolio)-1-butanesulfoni ionic liquid (IL) encapsulated within PEDOT:PSS. CF₃SO₃⁻ anions in the IL operating as Zn²⁺-transfer channels is reported. Moreover, the PEDOT:PSS network retains the IL, which renders Zn²⁺-transfer channels and a polysulfide cathode with enhanced structural stability. The Zn/polysulfide system delivers extraordinary capacity of 1148 mAh g⁻¹ and overwhelming energy density of 724.7 Wh kg⁻¹_cathode at 0.3 Ag⁻¹. During the discharging phase, S₆²⁻ is dominantly reduced by Zn to S²⁻ (S₆ → S²⁻). During the charging phase, these short chains are oxidized to form long-chain Zn_xLi_yS_3-6. A further optimized high-concentrated salt electrolyte is used to improve the reversibility of the battery, demonstrating an extended lifetime over 1600 cycles at 1 Ag⁻¹ with a capacity retention of 204 mAh g⁻¹. This facile approach and the superior performance of the developed aqueous Zn/S chemistry provide a new platform for sulfur-based battery and potentially solve the problems of other metal/sulfur batteries.