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

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.