Efficient Suppression of Dendrites and Side Reactions by Strong Electrostatic Shielding Effect via the Additive of Rb2SO4 for Anodes in Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention due to their low cost and environmental friendliness. However, the rampant dendrite growth and severe side reactions during plating/stripping on the surface of zinc (Zn) anode hinder the practicability of AZIBs. Herein, an effective and non-toxic cationic electrolyte additive of Rb2SO4 is proposed to address the issues. The large cation of Rb+ is preferentially adsorbed on the surface of Zn metal to induce a strong shielding effect for realizing the lateral deposition of Zn2+ ions along the Zn surface and isolating water from Zn metal to effectively inhibit side reactions. Consequently, the Zn parallel to Zn symmetric cell with the addition of 1.5 mm Rb2SO4 can cycle more than 6000 h at 0.5 mA cm(-2)/0.25 mAh cm(-2), which is 20 times longer than that without Rb2SO4. Besides, the Zn parallel to Cu asymmetric cell with Rb2SO4 achieves a very high average Coulombic efficiency of 99.16% up to 500 cycles. Moreover, the electrolyte with Rb2SO4 well matches with the VO2 cathode, achieving high initial capacity of 412.7 mAh g(-1) at 5 A g(-1) and excellent cycling stability with a capacity retention of 71.6% at 5 A g(-1) after 500 cycles for the Zn//VO2 full cell.