Ultra-Dense NiS2/Reduced Graphene Oxide Composite Cathode for High-Volumetric/Gravimetric Energy Density Nickel-Zinc Batteries

Safe and reliable Zn-based batteries with high volumetric energy density are critical to wearable and compact electronic devices. Despite the excellent gravimetric performance, actual volumetric energy density of developed Zn-based batteries remains far from satisfactory, mainly owing to insufficient active sites and low mass density. Here, a new synthetic strategy is proposed for fabricating monolithic and high-density NiS2/reduced graphene oxide (NiS2/rGO) composite cathode, achieving simultaneously high volumetric and gravimetric energy density for Ni-Zn battery. Taking metrics of fast diffusion of electrolyte ion, high electrical conductivity and abundant active sites, the unique nanopore-in-compact-network structure of NiS2/rGO enables unprecedented gravimetric/volumetric performance. The fabricated Ni-Zn battery delivers exceptionally high volumetric energy density (18.7 mWh cm-3 based on the whole volume of battery) together with high energy density (357.7 Wh kg−1 based on total mass of cathode) and outstanding long-term durability. More interestingly, the battery operates stably under hammering. This work provides new insights into designing reliable energy storage devices with high volumetric energy density for compact electronics.