Boosting the Rate Performance of Li–S Batteries via Highly Dispersed Cobalt Nanoparticles Embedded into Nitrogen-Doped Hierarchical Porous Carbon

Abstract

Lithium–sulfur (Li–S) batteries are one of the most promising alternatives to lithium–ion batteries because of the advantageous high energy density and low cost. However, the practical applications of Li–S batteries are hampered by a severe shuttle effect and sluggish polysulfide redox conversion. Herein, highly dispersed cobalt nanoparticles (∼0.8 wt %) embedded into nitrogen-doped hierarchical porous carbon (Co@N-HPC) are designed as an effective electrocatalyst for Li–S batteries, which exhibit a synergistic effect of anchoring and dual-directional catalytic conversion of polysulfides. The experimental and theoretical studies reveal that Co@N-HPC not only provides strong chemical affinity to polysulfides but also lowers the Li+ diffusion barrier and facilitates the precipitation and decomposition of Li2S, thus effectively inhibiting the shuttle effect and promoting the reaction kinetics of polysulfides. In addition, the well-dispersed Co nanoparticles in the three-dimensional carbon matrix guarantee the exposure of abundant polysulfide confining sites and catalytically active sites. Accordingly, the Li–S batteries assembled with Co@N-HPC functional separators harvest a high rate performance (808.4 mAh g−1 at 10 C), a long-lasting cycle stability (0.055% decay per cycle over 1000 cycles at 4 C), and a superior areal capacity retention (5.78 mAh cm−2 after 100 cycles with a high sulfur loading of 7 mg cm−2).