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

Abstract

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.