Cation‐in‐Mesopore Complex for 20 Ah‐Level Aqueous Battery

Abstract Metallic Zn‐based aqueous batteries (ZABs) have arisen as one of the most promising safe energy storage solutions, yet practical development, especially for the Ah‐level ZABs, is severely plagued by unmanageable side reactions and notorious dendrite proliferation. Here, we propose a cation‐in‐mesopore (CiM) complex chemistry by confining Zn 2+ within single‐mesopore cavities to construct a novel paradigm of 20 Ah‐level ZABs. Molecule dynamic and X‐ray absorption near‐edge structure analyses reveal that the single‐mesopore SiO 2 (smSiO 2 ) traps Zn 2+ , replacing H 2 O molecules in the primary sheath and forming Zn 2+ –smSiO 2 complexes. In situ electrochemical digital holography, in situ interface Fourier‐transform infrared spectroscopy, and H‐bonds density analyses clearly confirm that Zn 2+ –smSiO 2 complexes migrate and adhere onto the metallic Zn, facilitating the formation of mesopore weak H‐bonds interface by disrupting the aggregation of solvated H 2 O. Consequently, the Zn anode operates over 800 h under 55% depth of discharge, effectively suppressing H 2 O degradation and dendrite growth. The Zn//VO 2 pouch battery demonstrates capacities of 20.5 Ah at 0.2 A g −1 and 8.59 Ah at 1 A g −1 , and energy density of 65 Wh kg −1 and 96 Wh L −1 . The proposed cation‐in‐mesopore complex chemistry may mark a substantial step forward towards more sustainable and reliable ZABs.