Tandem Chemistry with Janus Mesopores Accelerator for Efficient Aqueous Batteries

A reliable solid electrolyte interphase (SEI) on the metallic Zn anode is imperative for stable Zn-based aqueous batteries. However, the incompatible Zn-ion reduction processes, scilicet simultaneous adsorption (capture) and desolvation (repulsion) of Zn²⁺(H₂O)₆, raise kinetics and stability challenges for the design of SEI. Here, we demonstrate a tandem chemistry strategy to decouple and accelerate the concurrent adsorption and desolvation processes of the Zn²⁺ cluster at the inner Helmholtz layer. An electrochemically assembled perforative mesopore SiO₂ interphase with tandem hydrophilic -OH and hydrophobic -F groups serves as a Janus mesopores accelerator to boost a fast and stable Zn²⁺ reduction reaction. Combining in situ electrochemical digital holography, molecular dynamics simulations, and spectroscopic characterizations reveals that -OH groups capture Zn²⁺ clusters from the bulk electrolyte and then -F groups repulse coordinated H₂O molecules in the solvation shell to achieve the tandem ion reduction process. The resultant symmetric batteries exhibit reversible cycles over 8000 and 2000 h under high current densities of 4 and 10 mA cm^-2, respectively. The feasibility of the tandem chemistry is further evidenced in both Zn//VO₂ and Zn//I₂ batteries, and it might be universal to other aqueous metal-ion batteries.