Promoted Lithium Polysulfides Conversion and Immobilization by Conductive Titanium oxynitride-Carbon Architecture Design toward Advanced Lithium-sulfur Batteries

In this work, a multifunctional deficient titanium oxynitride skeleton featured with Co-metal-decorated three-dimensional ordered macroporous (3DOM) structure and embedded with N-doped carbon nanotubes (Co@TiOxNy/N-CNTs) is fabricated as sulfur host in lithium-sulfur (Li-S) batteries. The unique 3DOM framework provides abundant space for sulfur accommodation, and effective pathways for electrolyte infiltration. The robust titanium oxynitride skeleton also ensures a good structural integrity during the repeated charge/discharge cycling. Meanwhile, introduction of oxygen-defects not only improves the intrinsic conductivity of the TiO2 skeleton, but also enhances its capability for LiPSs trapping. The N-CNT embedded in the macroporous framework forms an ultra-high conductive network, and it also provides rich micropores for sulfur distribution and physical confinement. The highly dispersed Co nanoparticles uniformly anchored on TiOxNy, and N-CNTs act as electrocatalyst promoting the conversion of LiPSs. Attributed to these features, the Co@TiOxNy/N-CNTs/S electrode presents good rate capability and excellent cycling performance. Even under sulfur loading of 6.34 mg cm-2 and low electrolyte to sulfur ratio (E/S = 8 µL mg-1) condition, a high area capacity of 5.05 mAh cm-2 can be achieved after 50 cycles. The flexible pouch cell also delivers an impressive discharge capacity of 972 mAh g-1 after 100 cycles under sulfur loading of 4 mg cm-2. This work offers a rational strategy for the design of advanced sulfur cathode in Li-S batteries.