An 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 for wearable and compact electronic devices. Despite their excellent gravimetric performance, the 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 a monolithic and high-density NiS2/reduced graphene oxide (NiS2/rGO) composite cathode, simultaneously achieving both high volumetric and gravimetric energy densities for Ni-Zn batteries. Taking advantages of fast diffusion of electrolyte ions, 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 m Wh cm(-3) based on the whole volume of the battery) together with high energy density (357.7 Wh kg(-1) based on the total mass of the 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.