High mass loading flower-like crystalline/amorphous NiCo-P/POx/NF as self-supporting cathode for ultra-high-performance nickel-zinc batteries

Abstract

The aqueous nickel-zinc battery combines the advantages of battery-level energy density and capacitor-level power density, which has been anticipated since its advent. However, given the limitations imposed by the relatively low capacity and subpar conductivity of the cathode, Ni-Zn batteries have unsatisfactory energy density and cycle life. This work has fabricated in situ a flower-like crystalline/amorphous nickel-cobalt phosphide/phosphate on nickel foam (NiCo-P/PO_x/NF), which acts as a binder-free cathode for the advanced aqueous Ni-Zn battery. NiCo-P/PO_x/NF inherits the flower-like structure of its predecessor, which can expose more active sites. Amorphous NiCoPO_x encases isolated crystalline NiCoP nanoparticles, and this particular structure can handle the volume expansion caused by long-term cycling. Consequently, the NiCo-P/PO_x/NF electrode achieves an ultra-high areal capacitance of 23.4 F·cm⁻² at a high mass loading of 12.0 mg·cm⁻² and demonstrates excellent cycling stability, retaining 80 % after 8000 cycles. The NiCo-P/PO_x/NF//Zn battery exhibits an area energy density of 4.05 mWh·cm⁻² and a peak power density of 32.57 mW·cm⁻², which are considerably higher than the values for most of the previously reported aqueous Ni-Zn batteries. This work offers a feasible strategy for developing aqueous alkaline Ni-Zn batteries featuring high energy and power densities.