Carbon-coated cobalt sulfide (CoS) hollow nanoparticles on carbon nanotube (CNT) networks are synthesized by combining three simple approaches: direct growth of Co3O4 nanocrystals on the CNT backbones, chemical conversion of the Co3O4 nanocrystals to CoS hollow nanoparticles, and the spatial introduction of conformal surface modification by carbon. It is noteworthy that the CoS hollow nano particles with inner cavity of <50 nm and an average wall thickness of 6-8 nm are derived from a template-free method. Such a template-free-derived multifunctional nanostructure design achieves the amalgamation of the favorite traits of one-dimensional conducting networks, hollow nanoparticles, and surface modification, thus resulting in much enhanced charge transfer, ion transport, and upholding the integrity of the electrode and electrode/electrolyte interface. When applied the synthesized CoS-based material as anodes in sodium-ion batteries (SIBs), excellent performance is observed. For instance, a reversible specific capacity of 562 mAh g(-1) at 100 mA g(-1) and a capacity retention rate of 90% after 200 cycles at a higher current density of 500 mA g(-1) are obtained. Moreover, a superior rate capability is observed with reversible specific capacities of 341 and 276 mAh g(-1) at 2000 and at 5000 mA respectively. (C) 2016 Elsevier B.V. All rights reserved.