Zn²⁺ Mediator with Ultrahigh Capacity over 8 <scp>m</scp> Enabled by H_1.07Ti_1.73O₄ 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 1.07 Ti 1.73 O 4 , HTO) medium layer enabling fast Zn 2+ transport and ultrahigh Zn 2+ concentration on the zinc anode surface is proposed. It is demonstrated that HTO uniquely facilitates Zn 2+ enrichment through the exchange of interlayer H + ions, achieving an exceptionally high Zn 2+ adsorption concentration of 8.35 m , far exceeding that of electrolyte (2 m ZnSO 4 ). 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 (SO 4 2− ) 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.