Modification of cobalt-containing MOF-derived mesoporous carbon as an effective sulfur-loading host for rechargeable lithium-sulfur batteries

Abstract

Cobalt-containing metal-organic frameworks (MOF) are synthesized, then carbonized and then acid etched to obtain mesoporous carbon for its potential application as lithium-sulfur (Li-S) battery cathode scaffolds. Before etching the resulting mesoporous carbon acquires a specific surface area of 206.5 m2 g−1 and a pore volume of 0.29 cm3 g−1, and in its sulfur-loading composite-1 the S-content is ∼45.2 wt%. After etching the modified mesoporous carbon exhibits a great improvement in porosity (Surface area ∼650.2 m2 g−1 and pore volume ∼ 0.77 cm3 g−1) and/or in sulfur-loading amount (i.e., the S-content of composite-2 ∼ 50.0 wt%). At 0.5 C (1 C = 1675 mA g−1), a composite-2 cathode delivers a high discharge capacity of 925.1 mAh g−1 in 2nd cycle and maintains a specific value of 781.1 mAh g−1 in the 140th cycle, much higher than those of composite-1 cathode. Both of the two composite electrodes display a slight increase of electrolyte-solution resistance and surface-film resistance and an obvious decrease of charge-transfer resistance. By comparison, these resistances of composite-2 are smaller than those of composite-1. This, together with the acid-modified structural parameters reasonably account for the enhanced electrochemical properties of composite-2.