Flexible VO_x Nanosphere@SWCNT Hybrid Films with Dual-Confinement Function of Polysulfides for High-Performance Lithium–Sulfur Batteries

With the rapid development of flexible electronics, a binder-free, flexible sulfur composite material is required to fabricate a cathode for high energy density lithium–sulfur (Li–S) batteries. Here, a facile hydrothermal method is reported to control the synthesis of VO_x hollow nanospheres (VHS) of different sizes. The sulfur-loaded VHSs are further mixed with single-walled carbon nanotubes (SWCNTs) to obtain a flexible binder-free composite. SWCNTs intertwine around the VO_x nanospheres and form an interconnective network to provide conductivity and structural integrity, whereas the small VO_x nanospheres offer strong confinement and excellent adsorption ability for polysulfides, thus yielding good cyclability. Results illustrate that VHS with diameters of ≈200 nm (VHS-200) show an outstanding capacity of 1069 mAh g⁻¹ at 1 C, which is higher than that of VHS with diameters of ≈400 and 900 nm (VHS-400 and VHS-900). Notably, the electrode shows rate performance of 614 mAh g⁻¹ at a high current rate of 20 C. Finally, the assembled flexible Li–S batteries show good bending and cycling stabilities in various bending angles, which is promising for potential applications in flexible electronics.