Weak H-bond interface environment for stable aqueous zinc batteries

Abstract

Hydrogen evolution reaction and Zn dendrite growth, originating from high water activity and the adverse competition between the electrochemical kinetics and mass transfer, are the main constraints for the commercial applications of the aqueous zinc-based batteries. Herein, a weak H-bond interface with a suspension electrolyte is developed by adding TiO₂ nanoparticles into the electrolytes. Owing to the strong polarity of Ti-O bonds in TiO₂, abundant hydroxyl functional groups are formed between the TiO₂[₁₁₀] active surface and aqueous environment, which can produce a weak H-bond interface by disrupting the initial H-bond networks between the water molecules, thereby accelerating the mass transfer of Zn²⁺ and reducing the water activity. In consequence, the Zn Zn symmetrical cells display reversible Zn plating/stripping behaviors with a high Coulombic efficiency of 99.7% over 700 cycles. Moreover, the TiO₂-based suspension strategy is also applicable to other zinc salt systems and exhibits fast plating/stripping behaviors. The suspension electrolyte enables long-term full cells, including Zn PANI hybrid capacitors and Zn ZnVO full batteries.