Spatially Confined Edge-to-Edge Strategy for Achieving Compact Na+/K+ Storage: Constructing Hetero-Ni/Ni3S2 in Densified Carbons

Transition metal sulfides (TMS) are considered as promising anodes for sodium/potassium ion batteries (SIBs/PIBs), and compositing TMS with conductive nanocarbons is an effective mitigation for improving rate performance and cycling stability. However, such a coupling strategy often decreases the tap density and therefore the volumetric energy of electrode. To achieve fast electron/ion transport and high volumetric capacity simultaneously, herein, a compact nanostructure with hetero Ni-Ni3S2 nanoparticles embedded in a densified S-doped carbon matrix (Ni-Ni3S2@SC) is constructed via a spatially confined edge-to-edge strategy. Experimental and theoretical results confirm that the carbon matrix and metallic Ni nanoparticles provide fast electron transport pathways at two scales, while the abundant heterojunctions with strong electric fields promote the ion migration and Na/K adsorption. As an anode in SIBs/PIBs, the Ni-Ni3S2@SC exhibits superior rate capability (289/197 mA h g(-1) at 2 A g(-1)), stable cycling performance (88.1/86.2% capacity retention after 100 cycles), and exceptional volumetric capacity (1048/850 mAh cm(-3) at 0.05 A g(-1)). The impressive energy-power characteristics for Ni-Ni3S2@SC anode are further confirmed in full cell batteries and hybrid capacitors. The reported spatially confined edge-to-edge strategy might be adapted to the construction of various binary and/or ternary metal sulfide dense electrodes for advanced energy storage devices.

Automated summary

In this study, a compact nanostructure with embedded Ni-Ni3S2 nanoparticles in S-doped carbon matrix was constructed for fast electron/ion transport and high volumetric capacity. The Ni-Ni3S2@SC anode exhibited superior rate capability, stable cycling performance, and exceptional volumetric capacity in sodium/potassium ion batteries. The spatially confined edge-to-edge strategy could be applied to construct various metal sulfide dense electrodes for advanced energy storage devices.