A sandwich-structured TiN/BN-C composite interlayer with enhanced performance for Li[sbnd]S batteries

Aiming to commercialize Li[sbnd]S battery, it is very important to achieve high sulfur loading alongside superior electrochemical performance. In this work, a novel composite material with sandwich structure constructed by titanium nitride nanoparticles and boron nitride‑carbon nanofibers (BNC-TiN-BNC), has been successfully prepared through electrospinning and spraying method, and applied as the interlayer in Li[sbnd]S batteries. Compared with the BNCNF interlayer, the sandwich-like BNC-TiN-BNC interlayer shows more excellent chemical adsorption for soluble lithium polysulfides (LiPSs) via the polar effects of the Ti[sbnd]S and S[sbnd]N bonds, and furthermore, the uniform distribution of TiN nanoparticles, filling in the pores between the nanofibers as packing layer of the BNC-TiN-BNC interlayer, can retard the migration of LiPSs more effectively by physical barriers. By introducing the BNC-TiN-BNC interlayer, the electron transfer, capacity and cycling life of Li[sbnd]S batteries have been improved significantly, especially at high current density. With the sulfur loading of 2.5 mg cm⁻², the cell with BNC-TiN-BNC interlayer delivers a high initial discharge capacity of 642.3 mA h g⁻¹ at high current density of 2.0C, and the capacity remains 594 mA h g⁻¹ with only the decay rate of 0.025% over 300 cycles.