Cobalt Nitride Nanoparticles Encapsulated in N-Doped Carbon Nanotubes Modified Separator of Li-S Battery Achieving the Synergistic Effect of Restriction-Adsorption-Catalysis of Polysulfides.

Abstract

Although lithium-sulfur (Li-S) batteries have broad market prospects due to their high theoretical energy density and potential cost-effectiveness, the practical applications still face serious shuttle effects of polysulfides (LiPSs) and slow redox reactions. Therefore, in this paper, cobalt nitride nanoparticles encapsulated in nitrogen-doped carbon nanotube (CoN@NCNT) are prepared as a functional layer for the separator of high-performance Li-S batteries. Carbon nanotubes with large specific surface areas not only promote the transport of ions and electrons but also weaken the migration of LiPSs and confine the dissolution of LiPSs in electrolytes. The lithiophilic heteroatom N adsorbs LiPSs by strong chemical adsorption, and the CoN particles with high catalytic activity greatly improve the kinetics of the conversion between LiPSs and Li2S2/Li2S during the charge-discharge process. Due to these advantages, the battery with CoN@NCNT modified separator has superior rate performance (initial discharge capacity of 834.7 mAh g-1 after activation at 1 C) and excellent cycle performance (capacity remains 729.7 mAh g-1 after 200 cycles at 0.2 C). This work proposes a strategy that can give the separator a strong ability to confinement-adsorption-catalysis of LiPSs in order to provide more possibilities for the development of Li-S batteries.