Construction of NiS Nanosheets Anchored on the Inner Surface of Nitrogen-Doped Hollow Carbon Matrixes with Enhanced Sodium and Potassium Storage Performances

Although nickel sulfides with high theoretical capacities have been demonstrated as promising anodes for sodium/potassium ion batteries (SIBs/KIBs), they always suffer from large volume expansion and inferior electronic conductivity, resulting in irreversible capacity loss. In this work, we design and prepare NiS nanosheets attached to the inner surface of the hole in nitrogen-doped carbon matrixes (h-NiS@N-C), which could provide much more exposed active sites for electrochemical reactions for SIBs and KIBs. The void space in nitrogen-doped carbon matrixes not only could largely buffer volume expansion of NiS nanosheets but also could store the electrolyte and shorten the diffusion distance for ions during the discharge/charge process. The h-NiS@N-C exhibits a reversible capacity of 510 and 500 mA h g(-1) after 200 cycles at 100 mA g(-1) for SIBs and KIBs, respectively. When tested at a high current density of 1 A g(-1), it displays a long-term cycling stability over 1000 cycles with a capacity of 290 and 260 mA h g(-1) for SIBs and KIBs, respectively. Furthermore, the sodium full battery performance suggests that the h-NiS@N-C has application potential for energy-storage devices.