In situ growth of Co nanoparticles in Ketjen Black for enhanced electrochemical performances of lithium-sulfur battery cathode

Lithium–sulfur (Li−S) batteries have the advantages of ultra-high theoretical energy density, low cost, and being environmentally friendly. However, the low S loading “shuttling” effect of intermediate lithium polysulfides in redox reactions and short cycle life limit their commercial applications. In this study, a facile, low-cost high-temperature reduction method was used to synthesize nano metallic Co particles in situ in Ketjen Black (KB) pores with excellent physical properties for nano Co/KB composites formation. In these composites, the particle size of Co is 5–30 nm, which is helpful to promote the transfer of electronic and ionic charges. Moreover, the catalytic effect of nano Co/KB composites and the strong chemical interactions of the Co–S bond were demonstrated, which significantly prohibits soluble polysulfides from migrating out of the KB skeleton because of the strong adsorption, enhancing the electrochemical performances of Li−S batteries. With a high S areal loading of 3 mg cm−2, the initial discharge specific capacity of the Co/KB/S cathode reached 1249.0 mAh g−1 at 0.05 C, while at 0.5 C the initial specific capacity of 785.5 mAh g−1 was achieved, and after 500 cycles the specific capacity maintained at 352.3 mAh g−1 with a fade rate of only 0.09% per cycle.