3D hollow reduced graphene oxide coated TiO2 heterostructures as an advanced host-interlayer integrated electrode for enhanced Li[sbnd]S batteries

Abstract

Owing to the short of comprehensive and detailed design of both interlayer and sulfur host, the inherent shortcomings of shuttle effect and sluggish redox chemistry of sulfur cathodes makes the capacity of Lithium-sulfur (LiS) batteries decreasing rapidly. Herein, a three-dimensional (3D) hollow heterostructure, constructed by reduced graphene oxide coated hollow TiO2 microspheres (noted as H-TiO2@rGO heterostructures), is developed as progressive host-interlayer integrated electrodes for LiS batteries. It is noteworthy that the hollow TiO2 microspheres provide a applicable space for loading and trapping sulfur nanoparticles, and the shell formed by TiO2 particles ensures enrichment of catalytic active sites, thus effectively trapping and promoting the transformation of soluble polysulfides. The elastic rGO layer can greatly promote the electrical conductivity of S host, as well as to significantly buffer volume expansion during charge/discharge process. Furthermore, the H-TiO2@rGO heterostructures modified integrated electrode can effectively improve the diffusion of lithium ions while preventing the shuttle effect due to the excellent trapping effect to polysulfides and the presence of continuous shell with holes composed of TiO2 small particles. Therefore, the rational designed host-interlayer integrated electrode of H-TiO2@rGO heterostructures not only confine the sulfur/polysulfides in 3D hollow microspheres, but also achieve catalytic transition of the polysulfides dissolved in electrolyte to solid Li2S2/Li2S, both of which synergistically achieves an extremely fading rate of 0.025% per cycle over 1000 times at 1C. The H-TiO2@rGO heterostructures proposed in this paper may supply a fresh idea for the fine design of LiS battery integrated electrodes.