Reinforced Lewis covalent bond by twinborn nitride heterostructure for lithium-sulfur batteries

Abstract

The practical application of lithium-sulfur (Li-S) batteries, as promising next-generation batteries, is hindered by their shuttle effect and the slow redox kinetics. Herein, a tungsten and molybdenum nitride heterostructure functionalized with hollow metal-organic framework-derived carbon (W₂N/Mo₂N) was proposed as the sulfur host. The hollow spherical structure provides storage space for sulfur, enhances electrical conductivity, and inhibits volume expansion. The metal atoms in the nitrides bonded with lithium polysulfides (LiPSs) through Lewis covalent bonds, enhancing the high catalytic activity of the nitrides and effectively reducing the energy barrier of LiPSs redox conversion. Moreover, the high intrinsic conductivity of nitrides and the ability of the heterostructure interface to accelerate electron/ion transport improved the Li⁺ transmission. By leveraging the combined properties of strong adsorption and high catalytic activity, the sulfur host effectively inhibited the shuttle effect and accelerated the redox kinetics of LiPSs. High-efficiency Li⁺ transmission, strong adsorption, and the efficient catalytic conversion activities of LiPSs in the heterostructure were experimentally and theoretically verified. The results indicate that the W₂N/Mo₂N cathode provides stable, and long-term cycling (over 2000 cycles) at 3 C with a low attenuation rate of 0.0196% per cycle. The design strategy of a twinborn nitride heterostructure thus provides a functionalized solution for advanced Li-S batteries.