Flexible hybrid carbon nanotube sponges embedded with SnS2 from tubular nanosheaths to nanosheets as free-standing anodes for lithium-ion batteries

Flexible carbon nanotube sponges (CNT sponges) are excellent three-dimensional (3D) porous substrates to fabricate free-standing electrodes applied in lithium-ion batteries, but the low energy density needs to be improved urgently. Hybrid, hierarchical structures designed towards high-performance electrodes have been reported as an efficient route. Here, SnS2 with controllable mass ratios and various morphologies from tubular nanosheaths to nanosheets has been grown in situ on carbon nanotubes in CNT sponges by a facile solvothermal method, taking thiourea as the medium. We propose the formation mechanism for diverse morphologies of SnS2. Also, we demonstrate that the tubular SnS2 nanostructure can be restrictively and directionally grown using CNTs as templates, and has much better reversible capacity and cyclability than its nanoparticle or nanosheet structures on CNTs. Meanwhile, CNT@SnS2 sponges could be used as free-standing and binder-free electrodes with significantly improved areal capacity than bare CNT sponges.