Controllable morphological transformations of nickel metal–organic frameworks for nickel–zinc batteries

Constructing hierarchical nanostructures with highly exposed surfaces is a promising strategy for developing advanced cathode materials in aqueous batteries. Herein, we employed a competitive coordination strategy to optimize the characteristics of nickel metal–organic framework (Ni-MOF). Specifically, the acetate ions were employed as precise regulators, exerting a distinct influence on the morphology of the Ni-MOF and leading to a structural transition from a block structure to a two-dimensional (2D) layered structure. The optimized Ni-MOF exhibits a unique superstructure composed of hierarchical 2D layers assembled into flower-like architectures. This distinctive superstructure increases the electrochemically active surface area of Ni-MOF (N-2) and provides abundant pathways for electron/ion transfer, thereby facilitating efficient electrochemical reactions. Remarkably, the assembled aqueous alkaline N-2//Zn battery demonstrated enhanced specific capacity (0.446 mAh·cm⁻² at 1 mA·cm⁻²) and excellent maximum energy/power density (0.789 mWh·cm⁻²/17.262 mW·cm⁻²). This work not only offers valuable insights into regulating MOF morphology, but also makes a contribution toward enhancing the application potential of MOFs in aqueous batteries.