Hierarchical NiSe₂ Nanosheet Arrays as a Robust Cathode toward Superdurable and Ultrafast Ni-Zn Aqueous Batteries

Zn-based aqueous batteries are enjoying the hotspots of worldwide research as their significant merits in economic cost and safety. However, the lack of a robust cathode (positive electrode) owning excellent rate ability, high capacity, and stability challenges their practical application. Herein, we propose hierarchical NiSe₂ nanosheet arrays as a robust cathode toward high-performance Ni-Zn aqueous batteries. Attributed to in situ anion exchange and Kirkendall effects, the nanosheet arrays are hierarchically constructed by NiSe₂ nanoparticles and abundant mesopores, which fully expose the active sites and accelerate the electrode kinetics. This unique structure endows the NiSe₂ electrode with remarkable specific capacity (245.1 mAh g^-1) and extraordinary high-rate ability (maintains 58% at 72.8 A g^-1) together with 10,000 cycles without any obvious capacity degeneration. As a result, based on the total active weight, our NiSe₂//Zn battery is capable of record-high power density (91.22 kW kg^-1/639.1 mW cm^-2), imposing energy density (328.8 Wh kg^-1/2.303 mWh cm^-2), and ultralong lifespan (only 8.3% capacity loss after 10,000 cycles), surpassing most of the aqueous batteries and supercapacitors recently reported. Moreover, this NiSe₂//Zn battery is also affordable (US$40 per kWh) and safe. These results open a new avenue for developing superdurable and ultrafast high-energy Ni-Zn batteries toward affordable and practical energy storage.