Zn2+ Mediator with Ultrahigh Capacity over 8 m Enabled by H1.07Ti1.73O4 Ion Sieve for Stable Zinc Metal Batteries

Abstract

Interfacial engineering is universally acknowledged as a dependable methodology to address the aqueous zinc metal interface issues. Although it is quite effective, the introduction of a modification layer impedes interfacial ion transport kinetics to some extent. Addressing this trade-off between stability and ion flux is critical for advancing zinc-based energy storage systems. Herein, a layered titanate (H_1.07Ti_1.73O₄, HTO) medium layer enabling fast Zn²⁺ transport and ultrahigh Zn²⁺ concentration on the zinc anode surface is proposed. It is demonstrated that HTO uniquely facilitates Zn²⁺ enrichment through the exchange of interlayer H⁺ ions, achieving an exceptionally high Zn²⁺ adsorption concentration of 8.35 m, far exceeding that of electrolyte (2 m ZnSO₄). The HTO layer serves as a dynamic ion transport bridge, establishing a continuous conductive pathway, and its inherent negative charge to selectively block sulfate anion (SO₄²⁻) penetration, thus exhibiting dual functionality as an ion conductor and anion sieve. The protected anode (Zn@HTO) exhibits exceptional stability, achieving nearly 2300 h cycling stability at a current density of 0.5 mA cm⁻² and over 3900 h at 5 mA cm⁻². Furthermore, Zn@HTO//ZnVO full cell demonstrates prolonged operational stability. This strategy provides a significant stride in breaking through the limitation of electrolyte concentration, thereby enabling fast, stable electrochemical reactions.