Synthesis of NiS/carbon composites as anodes for high-performance sodium-ion batteries

We demonstrate a general solid-state synthesis of nickel sulfide (NiS) and carbon-based composites (NiS/C) via simple thermal decomposition of nickel dibutyldithiocarbamate (C18H36N2NiS4) under ambient atmosphere, which can be applied to various carbon-based materials such as 2D graphene nanosheets (GNSs), 1D carbon nanotubes (CNTs), and 0D carbon black (CB). When used as anode materials for sodium-ion batteries (SIBs), the as-prepared NiS/C composites demonstrate excellent sodium storage properties including superior cycle stability and rate capability, delivering reversible capacities of 483 (for NiS/GNSs), 394 (for NiS/CNTs), and 413 mAh/g (for NiS/CB) at a current density of 200 mA/g after 100 cycles, respectively, which are much higher than that of the bare NiS counterpart (136 mAh/g at 200 mA/g after 100 cycles). Moreover, reversible capacities of 372 mAh/g for NiS/GNSs, 331 mAh/g for NiS/CNTs, and 317 mAh/g for NiS/CB are realized at a high rate of 2 A/g. The excellent electrochemical performance can be attributed to the introduction of the carbon-based materials, which not only serve as efficient buffering matrixes to tolerate the volume changes of NiS upon sodiation/desodiation but also improve the electrode conductivity. More importantly, this work provides a straightforward and general synthetic approach for designing various NiS/C composites as high-performance anodes for electrochemical energy storage.