Approaching Ultrastable High-Rate Li-S Batteries through Hierarchically Porous Titanium Nitride Synthesized by Multiscale Phase Separation.

Abstract

Porous architectures are important in determining the performance of lithium-sulfur batteries (LSBs). Among them, multiscale porous architecutures are highly desired to tackle the limitations of single-sized porous architectures, and to combine the advantages of different pore scales. Although a few carbonaceous materials with multiscale porosity are employed in LSBs, their nonpolar surface properties cause the severe dissolution of lithium polysulfides (LiPSs). In this context, multiscale porous structure design of noncarbonaceous materials is highly required, but has not been exploited in LSBs yet because of the absence of a facile method to control the multiscale porous inorganic materials. Here, a hierarchically porous titanium nitride (h-TiN) is reported as a multifunctional sulfur host, integrating the advantages of multiscale porous architectures with intrinsic surface properties of TiN to achieve high-rate and long-life LSBs. The macropores accommodate the high amount of sulfur, facilitate the electrolyte penetration and transportation of Li+ ions, while the mesopores effectively prevent the LiPS dissolution. TiN strongly adsorbs LiPS, mitigates the shuttle effect, and promotes the redox kinetics. Therefore, h-TiN/S shows a reversible capacity of 557 mA h g-1 even after 1000 cycles at 5 C rate with only 0.016% of capacity decay per cycle.