Mechanistic Insights into the Dissolution Relay for Deep Progression of Active Sites Toward Efficient and Ultralong‐Life Energy Storage

Abstract Transition metal (oxy)hydroxides serve as efficient aqueous cathode materials but suffer from the challenge of structure degradation during long‐term cycling applications. Achieving an ultralong service life, e.g., beyond 100 000 cycles, is highly desired for aqueous energy storage, which necessitates the precise cognition and modulation of the surface/interface microenvironment with prolonged cycling conditions. Herein, to address this issue, we for the first time engineer the competitive bonding and the electrochemical deep progression of NiCoCu medium‐entropy hydroxides. The theoretical and experiment results indicate that Cu is prone to leaching from the medium‐entropy hydroxides with cycling, which elevates the d/p‐band centers to activate the lattice oxygen and Co atoms, triggering a Cu/Co dual‐cation dissolution relay phenomenon. As‐incorporated Co vacancies favor the β‐to‐γ phase transformation of the reconstructed structure, accompanied by the coordination oscillation and the production of ultrafine (∼1.9 nm) nanodomains with improved kinetics and stability. Consequently, capacity retention of 1485 C g −1 was achieved after 150 000 cycles for the reconstructed electrodes, which is superior to many state‐of‐the‐art NiCo‐based materials. This work elucidates the potential of the coordination reorganization and deep progression of the reaction microenvironment to break the performance limit of energy storage and beyond.