Synergistically Stabilizing Zinc Anodes by Molybdenum Dioxide Coating and Tween 80 Electrolyte Additive for High-Performance Aqueous Zinc-Ion Batteries.

Recently, aqueous zinc-ion batteries (ZIBs) have become increasingly attractive as grid-scale energy storage solutions due to their safety, low cost, and environmental friendliness. However, severe dendrite growth, self-corrosion, hydrogen evolution, and irreversible side reactions occurring at Zn anodes often cause poor cyclability of ZIBs. This work develops a synergistic strategy to stabilize the Zn anode by introducing a molybdenum dioxide coating layer on Zn (MoO 2 @Zn) and Tween 80 as an electrolyte additive. Due to the redox capability and high electrical conductivity of MoO 2 , the coating layer can not only homogenize the surface electric field but also accommodate the Zn 2+ concentration field in the vicinity of the Zn anode, thereby regulating Zn 2+ ion distribution and inhibiting side reactions. MoO 2 coating can also significantly enhance surface hydrophilicity to improve the wetting of electrolyte on the Zn electrode. Meanwhile, Tween 80, a surfactant additive, acts as a corrosion inhibitor, preventing Zn corrosion and regulating Zn 2+ ion migration. Their combination can synergistically work to reduce the desolvation energy of hydrated Zn ions and stabilize the Zn anodes. Therefore, the symmetric cells of MoO 2 @Zn∥MoO 2 @Zn with optimal 1 mM Tween 80 additive in 1 M ZnSO 4 achieve exceptional cyclability over 6000 h at 1 mA cm -2 and stability (>700 h) even at a high current density (5 mA cm -2 ). When coupling with the VO 2 cathode, the full cell of MoO 2 @Zn∥VO 2 shows a higher capacity retention (82.4%) compared to Zn∥VO 2 (57.3%) after 1000 cycles at 5 A g -1 . This study suggests a synergistic strategy of combining surface modification and electrolyte engineering to design high-performance ZIBs.