Hollow multishelled structural TiN as multi-functional catalytic host for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery has attracted extensive attention because of its ultrahigh theoretical energy density and low cost. However, its commercialization is seriously hampered by its short cycling life, mainly due to the shuttle of soluble lithium polysulfides (LiPSs) and poor rate capability due to sluggish reaction kinetics. Although significant efforts have been devoted to solving the problems, it is still challenging to simultaneously address all the issues. Herein, titanium nitride hollow multishelled structure (TiN HoMS) sphere is designed as a multi-functional catalytic host for sulfur cathode. TiN, with good conductivity, can effectively catalyze the redox conversion of S and LiPSs, while its surficial oxidation passivation layer can strongly anchor LiPSs. Besides, HoMS enables TiN nanoparticle subunits to expose abundant active sites for anchoring and promoting conversion of LiPSs, while the multiple shells provide physical barriers to restrict the shuttle effect. In addition, HoMS can buffer the volume expansion of sulfur and shorten the charge transport pathway. As a result, the sulfur cathode based on triple-shelled TiN HoMS exhibits an initial specific capacity of 1016 mAh·g⁻¹ at a high sulfur loading of 2.8 mg·cm⁻² and maintains 823 mAh·g⁻¹ after 100 cycles. Moreover, it shows a four times higher specific capacity than the one without TiN host at 2 C.