Controlling {001} facet exposure in TiO nanoflakes for enhanced polysulfide trapping in lithium–sulfur batteries

Abstract

The development of lithium–sulfur (Li–S) batteries is considerably limited due to the “shuttle effect” of soluble lithium polysulfides (LiPSs). The introduction of a modified separator at the cathode side has been proven to be one of the effective solutions. In this work, TiO nanoflakes (TiO-NFs) with {001} exposed facets were successfully prepared to block the shuttle of LiPSs and improve the redox kinetics at the same time. The employment of polydopamine (PDA) was helpful in inhibiting the morphology change and exposed facet variation of TiO-NFs during the magnesiothermic reduction reaction process. Through visible adsorption, symmetric cells and Li₂S nucleation testing, the TiO-NFs are confirmed to possess excellent adsorption and catalytic activity toward LiPSs. The assembled batteries using the TiO-NFs@PP modified separator exhibit an initial capacity of 1492 mAh g⁻¹ at 0.1C. When the current density reached 1C, the capacity decay per cycle was as low as 0.067% after 1000 cycles. Even under a high sulfur loading of 5.5 mg cm⁻², a high areal capacity of 4 mAh cm⁻² can be maintained after 100 cycles at 0.2C. This work provides new methods for the design and preparation of non-stoichiometric metal oxides with specific exposed facets toward high-performance Li–S batteries.