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.