A versatile electrolyte additive enabling highly reversible Zn anode in aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have a great application prospect in large-scale energy storage, but rampant dendrite growth and continuous side reactions cause the deterioration of zinc electrode performance. Herein, a distinctive additive, sodium p-toluene sulfonate (STS) is shown to enable stable and reversible zinc deposition. Both density functional theory (DFT) calculation and experimental observation demonstrate that STS additive not only can modulate solvation structure to reduce the number of active water molecules, but also is preferentially adsorbed on the Zn(101) plane and guide the preferentially growth of the Zn(002) plane. Moreover, the water-poor electric double layer (EDL) formed on the Zn anode and the reduction of pH value of the electrolyte caused by STS have a positive effect on the inhibition of side reactions. Moreover, the formation of hydrophobic layer and the regulation of pH have a positive effect on the inhibition of side reactions. Consequently, the cycle life of corresponding Zn//Zn symmetric battery with STS additive can reach up to 3500 h at 1 mA cm −2 /1 mAh cm −2 , and >900 h at 5 mA cm −2 /5 mAh cm −2 . Moreover, the STS additive endows the Zn//MnO 2 full cell to achieve an excellent capacity retention rate of 78 % over 800 cycles at 1 A g −1 .