An ultra-dense NiS2/reduced graphene oxide composite cathode for high-volumetric/gravimetric energy density nickel–zinc batteries

Abstract

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.