Cobalt nanoparticles to cobalt sulfide: catalytic surface evolution for outstanding performance lithium-sulfur...

Urgent requirements for lithium‑sulfur batteries with high theoretical energy to overcome the limitations of the low reaction kinetics and shuttle effect before they reach commercialization at high yields. Transition metals are considered to be potent catalysts for accelerating polysulfide transformation, thus enhancing electrochemical performance. However, the transition reaction in the catalysts has yet to be explored further. Herein, a type of porous carbon loaded with cobalt nanoparticles is developed as catalysts for lithium‑sulfur batteries. Ultimately, superior cycling performance is realized at a current density of 1C (1C = 1675 mA g^-1), with a reversible capacity of up to 1133 mAh g^-1 and stabilized 1000 cycles. Specifically, the cobalt nanoparticles undergo surface conversion into cobalt sulfide during electrochemical reactions, resulting in a heterogeneous structure of Co@Co_xS_y.