Functionless cobalt toward functional cobalt nitride: Catalytic sulfur carrier for lithium-sulfur pouch batteries

Sulfur cathodes can be paired with lithium metal anodes to construct lithium-sulfur (Li-S) batteries. However, the dissolution of high-order lithium polysulfides (Li2Sn, 4 ≤ n ≤ 8) and the poor conductivity of sulfur cathodes must be addressed before they can be successfully commercialized. In this paper, we report a metal-organic framework (MOF)-derived composite, Co4N&CoNx@Ti3C2, as a catalytic sulfur carrier to moderate the interconversion of S species to achieve a high-performance Li-S battery. Heavy and functionless metallic Co particles derived from MOF pyrolysis were converted to functional Co4N to construct porous catalytic sites. Electrons can be rapidly transported through the electronic conductor Ti3C2 substrate. The mechanism of the Co4N&CoNx to catalyze the interconversion reaction of polysulfides was both quantitatively and qualitatively revealed from a molecular orbital vision. The prepared Co4N&CoNx@Ti3C2 cathode battery can generate a high reversible capacity of 978.2 mAh g−1 at 2C and demonstrates excellent stability. The assembled Co4N&CoNx@Ti3C2/S electrode Li-S pouch battery can deliver up to 396 Wh kg−1 actual energy density and can stably function for more than 250 cycles.