Dual-Parasitic Effect Enables Highly Reversible Zn Metal Anode for Ultralong 25,000 Cycles Aqueous Zinc-Ion Batteries

The use of electrolyte additives is an efficient approach to mitigating undesirable side reactions and dendrites. However, the existing electrolyte additives do not effectively regulate both the chaotic diffusion of Zn2+ and the decomposition of H2O simultaneously. Herein, a dual-parasitic method is introduced to address the aforementioned issues by incorporating 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMImOTf) as cosolvent into the Zn(OTf)2 electrolyte. Specifically, the OTf– anion is parasitic in the solvent sheath of Zn2+ to decrease the number of active H2O. Additionally, the EMIm+ cation can construct an electrostatic shield layer and a hybrid organic/inorganic solid electrolyte interface layer to optimize the deposition behavior of Zn2+. This results in a Zn anode with a reversible cycle life of 3000 h, the longest cycle life of full cells (25,000 cycles), and an extremely high initial capacity (4.5 mA h cm–2), providing a promising electrolyte solution for practical applications of rechargeable aqueous zinc-ion batteries.