Composite number

Engineering

Endocrinology

Carbon fibers

Physical chemistry

Composite material

Catalysis

Electrode

Organic chemistry

Inorganic chemistry

Chemistry

Materials science

Lithium (medication)

Bifunctional

Graphene

Electrocatalyst

Chemical engineering

Cobalt

Sulfur

Electrochemistry

Nitrogen

Medicine

Gravimetric analysis

Journal of the American Chemical Society

Because of their high theoretical energy density and low cost, lithium-sulfur (Li-S) batteries are promising next-generation energy storage devices. The electrochemical performance of Li-S batteries largely depends on the efficient reversible conversion of Li polysulfides to Li2S in discharge and to elemental S during charging. Here, we report on our discovery that monodisperse cobalt atoms embedded in nitrogen-doped graphene (Co-N/G) can trigger the surface-mediated reaction of Li polysulfides. Using a combination of operando X-ray absorption spectroscopy and first-principles calculation, we reveal that the Co-N-C coordination center serves as a bifunctional electrocatalyst to facilitate both the formation and the decomposition of Li2S in discharge and charge processes, respectively. The S@Co-N/G composite, with a high S mass ratio of 90 wt %, can deliver a gravimetric capacity of 1210 mAh g-1, and it exhibits an areal capacity of 5.1 mAh cm-2 with capacity fading rate of 0.029% per cycle over 100 cycles at 0.2 C at S loading of 6.0 mg cm-2 on the electrode disk.

Cobalt in Nitrogen-Doped Graphene as Single-Atom Catalyst for High-Sulfur Content Lithium–Sulfur Batteries