Breaking the Electronic Reactivity and Ionic Mobility Trade‐off via Confined Water Redistribution for Hydroxide‐ion Storage

ABSTRACT Simultaneously enhancing electronic conductivity/reactivity, and ionic mobility remains a longstanding challenge in electrochemical energy storage. Herein, we report a water‐management‐inspired strategy, that enables the regulation of confined water within the interlayer gallery of hydrous layered transition‐metal hydroxides. As a promising electrode driving the Renaissance of Ni‐Fe batteries, α‐Ni(OH) 2 holds interlayer water that can be coordinated to the NiO 6 slabs via annealing. Based on a series of spectroscopic and theoretical analyses, as a consequence of increasing coordinated water that interacts with NiO 6 slabs, NiO 6 octahedron distortion was intensified, and the e g * band was broadened to enhance electronic reactivity. In contrast, decreasing interlayer water reconstructs hydrogen‐bonding networks, facilitating OH – mobility. At 170°C, the electronic reactivity and ionic mobility are balanced, markedly improving performance (321.8 mAh g −1 at 1 A g −1 ; 167.9 mAh g −1 at 16 A g −1 ), with a 48% increase in cycling stability. Our work highlights a micro‐scale water management paradigm that harmonizes electron reactivity and ion transport for superior electrochemical performance.