TiN/TiC heterostructures embedded with single tungsten atoms enhance polysulfide entrapment and conversion for high-capacity lithium-sulfur battery applications

The rapid decay of the charge/discharge capacity of lithium-sulfur batteries due to the sluggish reaction kinetics and the shuttling behaviour of soluble polysulfides significantly restricts their practical application in energy storage systems. Herein, two-dimensional TiN/TiC heterostructures embedded with single tungsten atoms (SWA) are developed and introduced as a modified interlayer (SWA-TiN/TiC) in Li-S battery devices. The SWA-TiN/TiC material has a large specific surface area, which provides a physical barrier while supplying numerous active sites for polysulfides reactions. TiN and TiC both demonstrate excellent electronic conductivity and catalytic activity, which facilitate the conversion of polysulfides. Meanwhile, the uniformly-dispersed SWAs significantly enhance the chemical affinity with polysulfides and accelerate their redox reactions. As a result, the sulfur cathodes coated with the SWA-TiN/TiC interlayer achieve excellent rate performance and long-term cycling stability. An ultrahigh specific capacity of up to 1577.7 mAh g−1 at 0.1 C is achieved, and even at high sulfur loading (6.25 mg cm−2), a high areal capacity of 4.63 mAh cm−2 is obtained. This work highlights the potential of single metallic atoms on non-carbonaceous matrix for the development of high-performance catalysts that can achieve strong polysulfides immobilization for practical applications in lithium-sulfur batteries.