Regulating solvation shells and interfacial chemistry in zinc-ion batteries using glutaronitrile based electrolyte

Abstract

The dendrite growth, parasitic reactions and dissolution of cathodes caused by numerous free H₂O molecules in aqueous electrolyte can lead to rapid performance degradation, limiting the application of aqueous Zn-ion batteries (AZIBs). Here, a new glutaronitrile (GN) based electrolyte is introduced by coupling a hydrated Zn salt (Zn(ClO₄)₂·6H₂O) and GN to mitigate these issues. Raman spectroscopy and molecular dynamics simulations demonstrate that the strong coordination between Zn²⁺ and GN can effectively regulate solvation shells of Zn²⁺ ions. Moreover, the H₂O molecules mostly exist in the confined state rather than in the free state, ensuring the excellent electrochemical performances. Benefiting from this unique solvation shell of Zn²⁺ ions, Zn‖Zn symmetric cells can operate steadily for more than 800 h without Zn dendrite growth, and Zn‖Cu half-cells achieve extremely reversible zinc plating/stripping with coulombic efficiencies of 99.0%. XPS suggests that the in situ formed ZnO-rich solid electrolyte interface (SEI) in this GN based electrolyte can effectively inhibit the occurrence of parasitic reactions, improving the stability of the battery. Thus, the Zn‖NH₄V₄O₁₀ full cells exhibit a high specific capacity of 239 mA h g⁻¹ at 5C over 2500 cycles without significant capacity decay. The differences in the electrochemical reaction mechanism of the NH₄V₄O₁₀ cathode in between ZHO and ZGN have been discussed in detail.