Cobalt-Based Double Catalytic Sites on Mesoporous Carbon as Reversible Polysulfide Catalysts for Fast-Kinetic Li-S Batteries.

Li-S batteries are considered to be the most promising next-generation advanced energy-storage systems. However, the sluggish reaction kinetics and the "shuttle effect" of lithium polysulfides (LiPSs) severely limit their battery performances. To overcome the complex and multiphase sulfur redox chemistry of LiPSs, in this study, we propose a new type of cobalt-based double catalytic sites (DCSs) codoped mesoporous carbon to immobilize and reversibly catalyze the LiPS intermediates in the cycling process, thus eliminating the shuttle effect and improving the charge-discharge kinetics. The theoretical calculation shows that the well-designed DCS configuration endows LiPSs with both strong and weak binding capabilities, which will facilitate the synergistic and reversible catalytic conversion. Furthermore, the experimental results also confirm that the DCS structure shows significantly enhanced catalytic kinetics than the single catalytic sites. The Li-S battery equipped with the DCS structure displays an extremely high discharge capacity of 918 mA h g at a current density of 0.2 C and can reach a capacity of 867 mA h g after 200 cycles with an ultralow capacity attenuation rate of 0.028% for each cycle. This study opens new avenues to address the catalytic requirements both in discharging and charging processes.