High-mass-loading NiCo-LDH hollow nanoflower for high-performance alkaline aqueous zinc batteries

• Abundant oxygen vacancies are confirmed in the NiCo-LDH nanoflower. • Hollow hierarchical structure facilitates fast ion transport and structural integrity. • High areal mass loading (13 mg cm -2 ) is realized for NiCo-LDH electrodes.. Nickel/cobalt-based materials are promising cathode owing to its high redox potential, high specific capacity, and long cycling performance. However, with the mass-loading of the electrode increasing, it greatly hinders the ion diffusion and charge transport, resulting in serious decrease of the electrode capacity. Herein, a hierarchical nickel-cobalt-based porous nanoflower structure (NiCo-Nanoflower) composed of numerous ultrathin nanosheets is synthesized, which significantly enhances the surface area and provides additional active sites. Besides, the abundant oxygen defects in NiCo-Nanoflower significantly enhance its electrical conductivity. Therefore, the NiCo-Nanoflower electrode exhibits a high reversible capacity of up to 210.4 mAh g −1 at 0.5 A g −1 and excellent rate retention of 180.4 mAh g −1 at 8 A g −1 (104 mA cm −2 ) even under high areal mass loading of 13 mg·cm −2 . Upon assembly in a NiCo//Zn battery system, the configuration demonstrates exceptional electrochemical stability, maintaining 74.3% capacity retention after 5000 cycles. This work demonstrates that NiCo-Nanoflower, equipped with three-dimensional microstructure and oxygen-enriched defects, holds significant potential for application in high-mass-loading cathodes for alkaline aqueous zinc batteries. Hollow spherical porous nanoflower-structured NiCo-LDH with enlarger surface area and active sites was synthesized. The abundant oxygen vacancies endow high conductivity, which facilitates rapid electrolyte ion diffusion into the interior and accelerates redox reactions. Notably, the exceptional electrochemical performance of NiCo-Nanoflower electrodes even under high areal mass loading (13 mg cm -2 ) is mainly due to the synergistic effect between hollow structural design and abundant oxygen vacancies.