Improving Polysulfides Adsorption and Redox Kinetics by the Co4N Nanoparticle/N-Doped Carbon Composites for Lithium-Sulfur Batteries

Improved conductivity and suppressed dissolution of lithium polysulfides is highly desirable for high-performance lithium-sulfur (Li-S) batteries. Herein, by a facile solvent method followed by nitridation with NH3, a 2D nitrogen-doped carbon structure is designed with homogeneously embedded Co4N nanoparticles derived from metal organic framework (MOF), grown on the carbon cloth (MOF-Co4N). Experimental results and theoretical simulations reveal that Co4N nanoparticles act as strong chemical adsorption hosts and catalysts that not only improve the cycling performance of Li-S batteries via chemical bonding to trap polysulfides but also improve the rate performance through accelerating the conversion reactions by decreasing the polarization of the electrode. In addition, the high conductive nitrogen-doped carbon matrix ensures fast charge transfer, while the 2D structure offers increased pathways to facilitate ion diffusion. Under the current density of 0.1C, 0.5C, and 3C, MOF-Co4N delivers reversible specific capacities of 1425, 1049, and 729 mAh g(-1), respectively, and retains 82.5% capacity after 400 cycles at 1C, as compared to the sample without Co4N (MOF-C) values of 61.3% (200 cycles). The improved cell performance corroborates the validity of the multifunctional design of MOF-Co4N, which is expected to be a potentially promising cathode host for Li-S batteries.