Preparation of TiO2 nanoparticles decorated porous carbon via a pseudo co-templating strategy and their application as substrates for high performance cathode of LiS batteries

Abstract

Lithium‑sulfur batteries (LSBs) with a high theoretical specific capacity are considered as one of the most promising energy storage devices for next-generation. However, issues such as the insulation of pristine sulfur, the shuttle effect of polysulfides (LiPSs), and the volume change of sulfur cathode during cycling hinder their commercial applications. In this work, composite microspheres of TiO₂@p-C consisting of porous carbon decorated with TiO₂ nanoparticles, have been designed and synthesized aiming to confine and trap the polysulfides inside the porous substrates and to improve the kinetics of the electrochemical reaction therein. TiO₂ particles with size of a few nanometers are prepared by a tetraethyl ammonium hydroxide assisted sol-gel method. Composite microspheres of TiO₂@p-C are created through spray drying technique using chitosan as carbon source, and nanoparticles of SiO₂ with TiO₂ as co-template while selectively etching of the former. The confinement effects via the pores in the TiO₂@p-C microspheres and the affinity between the polar TiO₂ moieties and the polysulfide species work synergistically, alleviating the effusion of the polysulfides and promoting the conversion reaction of them as well. As a result, the shuttle effect of polysulfides can be inhibited obviously. Significantly, the S@TiO₂@p-C-2 composite cathode exhibits excellent cyclic performance of 1263 mAh g⁻¹ at 0.2C and maintains still a discharge capacity of 809 mAh g⁻¹ after 100 charge and discharge cycles. At a current density of 2C, it still delivers an outstanding specific capacity of 772 mAh g⁻¹. In the case of high sulfur load up to 90 wt%, the discharge capacity of S@TiO₂@p-C-2 composite electrode could still maintain at 469.5 mAh g⁻¹ after 100 cycles under current density of 0.2C.