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

摘要

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.