Natural seawater-based electrolytes for zinc-ion batteries

Abstract

Designing high-entropy electrolytes is an effective strategy to promote the electrochemical performances of aqueous zinc-ion batteries (ZIBs). Seawater holds great potential as a natural solvent to configure high-entropy electrolytes due to its complex composition and high salinity. In this study, the electrochemical performances of the zinc anode and the NH₄V₄O₁₀ cathode reinforced by the seawater electrolyte have been comprehensively investigated. Theoretical calculations demonstrate that alkali metal cations (Na⁺, K⁺, Mg²⁺, and Ca²⁺) in the seawater electrolyte confer lower reduction potential and stronger adsorption energy for the zinc anode, which effectively inhibits dendrite growth through the electrostatic shielding effect. In addition, alkali metal cations also guarantee lower desolvation energy and stronger adsorption and insertion energy for the NH₄V₄O₁₀ cathode, which significantly improves the specific capacity through the preferential adsorption/insertion and additional (de)intercalation reactions of alkali metal cations. As expected, the corresponding Zn//Zn cells exhibit low voltage polarization and Zn//Cu cells present a high plating/stripping coulombic efficiency of 99.13%. Furthermore, Zn//NH₄V₄O₁₀ cells deliver a high capacity of 229.8 mA h g⁻¹ at 0.5 A g⁻¹ after 100 cycles and high cycling stability for 500 cycles at 2 A g⁻¹. These satisfactory results verify that the application of seawater electrolytes in ZIBs is practical.