Electrochemically Activated Nickel-Carbon Composite as Ultrastable Cathodes for Rechargeable Nickel-Zinc Batteries

Aqueous rechargeable nickel-zinc batteries are highly attractive for large-scale energy storage for their high output voltage, low cost, and excellent safety; however, their inferior cycling durability due to the degradation of the Ni-based cathode is a major obstacle for their applications. In this context, we develop a new kind of porous electrochemically activated Ni nanoparticle/nitrogen-doped carbon (Ni/NC) composite material as ultrastable cathodes for advanced aqueous rechargeable nickel-zinc batteries. The in situ formation of a highly active NiO _x(OH) _y layer on Ni nanoparticles and a unique hydrophilic porous architecture endow the activated Ni/NC composite with high accessible area, abundant active sites, easy electrolyte permeation, and shortened charge/ion transport pathway. Consequently, a high capacity of 381.2 μAh cm^-3 with an outstanding rate capability is achieved by the Ni-Zn battery using the optimized activated Ni/NC composite as the cathode (about 30-fold enhancement compared to that with the pristine Ni/NC composite as the cathode). More impressively, the as-assembled Ni-Zn battery achieves an unprecedented cyclic stability with no capacity loss after 36 000 charge/discharge cycles. This is the highest cyclic durability ever for Ni-Zn batteries and other aqueous rechargeable batteries. This novel efficient electrochemical activation strategy to achieve a high-performance cathode and demonstration of an ultrastable aqueous rechargeable Ni-Zn battery may open up new vistas on the development of more advanced and reliable energy storage materials and devices.