Controllable Preparation of Hollow Spheroidal Nickel-Based Metal–Organic Frameworks Microparticles for Aqueous Nickel–Zinc Batteries

Metal-organic frameworks (MOFs) have garnered increasing interest due to their porous structure, high surface area, and rich redox active metal ions that can be exploited as good electrode materials for electrochemical energy storage. Herein, nickel-based MOFs materials with different morphological structures of solid spheres (Ni-BTC-0), hollow spheroidal microparticles (Ni-BTC-5), and hollow spheres (Ni-BTC-10) have been facilely synthesized by using water as a regulator. Among them, the unique structure of hollow spheroidal Ni-BTC-5 microparticles with the largest surface area can provide abundant channels for fast electron and electrolyte transport as well as expose more active sites. As a result, the Ni-BTC-5 electrode displays a higher specific capacity of 177.8 mA h/g than the Ni-BTC-0 (110.6 mA h/g) and Ni-BTC-10 (129.9 mA h/g) electrodes at a current density of 1.0 A/g. Furthermore, the assembled aqueous nickel-zinc battery based on the Ni-BTC-5 cathode and Zn anode delivers a high capacity of 210.6 mA h/g, a remarkable energy density of 362.3 W h/kg, and a good capacity retention rate of 80.2% over 3000 cycles. This study provides a new way to regulate the morphological structures of MOFs, also demonstrating that regulating the structure of MOFs is one of the effective approaches to improve their energy storage performances.