Heterostructured NiS/TiO2 Nanosheets Assembled into Microflowers with Enhanced Cycling Stability for Sodium-Ion Storage

Transition metal sulfides are characterized by their low price and strong capacity performance and show a great potential for development as materials for anodes in sodium-ion batteries (SIBs). However, the structure instability and inherently poor conductivity limit their practical application. In this work, heterostructured NiS/TiO2 microflower composite materials assembled by nanosheets are synthesized through a hydrothermally assisted postsulfidation method. Meanwhile, the nanosheets are further coated by N, S double-doped carbon using pyrolytic dopamine to increase their electrical conductivity. It is demon-strated that the unique heterostructure not only narrows the band gap of composite materials but also generates an electron-concentrated region on the heterointerface, which significantly enhances the rate of charge transfer, Na+ diffusion ability, and reaction kinetic properties. As a consequence, the composites reveal superior electrochemical properties for Na+ storage; the specific capacity is 632.1 mA h g(-1) after 100 cycles at 0.1 A g(-1) and even up to 1.0 A g(-1), while a capacity of 514.2 mA h g(-1) is maintained after 250 cycles. The full battery is assembled by NiS/TiO2, and Na4Fe3(PO4)(2)P2O7 also displays a good capacity and stability performance. These results provide a direction for the exploration of anode materials for SIBs.