Tailoring solvation sheath and desolvation processes of weakly solvated Zn2+ through heterointerfaces built-in electric field effects for ultra-stable aqueous zinc batteries

Abstract

Solvated zinc ions are prone to undergo desolvation at the electrode/electrolyte interfaces, and unstable H₂O molecules within the solvated sheaths tend to trigger hydrogen evolution reaction (HER), further accelerating interfaces decay. Herein, we propose for the first time a novel strategy to enhance the interfacial stabilities by in-situ dynamic reconstruction of weakly solvated Zn²⁺ during the desolvation processes at heterointerfaces. Theoretical calculations indicate that, due to built-in electric field effects (BEFs), the plating/stripping mechanism shifts from [Zn(H₂O)₆]²⁺ to [Zn(H₂O)₅(SO₄)^2-]²⁺ without additional electrolyte additives, reducing the solvation ability of H₂O, enhancing the competitive coordination of SO₄²⁻, essentially eliminating the undesirable side effects of anodes. Hence, symmetric cells can operate stably for 3000 ​h (51.7-times increase in cycle life), and the full cells can operate stably for 5000 cycles (51.5-times increase in cycle life). This study provides valuable insights into the critical design of weakly solvated Zn²⁺ and desolvation processes at heterointerfaces.