Ultrafast sodium-ion storage in an interconnected Ni/Ni3S2 nanocomposite with long-term cycling performance

Nickel sulfide (Ni ₃S ₂) is a potential anode candidate for sodium-ion batteries due to its abundance, stable structure, and low price. However, its rate and cycling performance require improvement for practical applications. This paper reports the facile synthesis of a unique composite consisting of an interconnected nickel/nickel sulfide nanocomposite (Ni/Ni ₃S ₂ ) by heating a mixture of nickel nanopowder and sulfur. The interconnected nanostructured backbone of the nickel nanoparticles facilitates continuous electron pathways in the composite, while the embedded nanosized nickel sulfide domain reduces the diffusion length and improves reaction kinetics. The Ni/Ni ₃S ₂ electrode exhibits excellent rate performance in dimethyl ether (DME) electrolyte, with a current density of 80 A g ⁻¹ and capacity of 151 mA h g ⁻¹ ; it also exhibits stable, ultralong cycling performance. Synergism between the unique nanostructure of the composite and the low-viscosity DME electrolyte may be responsible for the extraordinary cycling and rate performance. A full cell with a Na ₃V ₂(PO ₄) ₃ (NVP) electrode delivers a capacity of 111 mA h g ⁻¹ at 100 A g ⁻¹; moreover, the Ni/Ni ₃S ₂–NVP full cell retains 55% of its capacity after 5000 cycles at 20 A g ⁻¹. The developed strategy, which uses a conductive metal-nanoparticle/metal-sulfide nanocomposite, is applicable to other systems and is scalable for practical applications.