Constructing a multifunctional mesoporous composite of metallic cobalt nanoparticles and nitrogen-doped reduced graphene oxides for high-performance lithium-sulfur batteries

Electrochemical properties of lithium-sulfur (Li-S) batteries are mainly hindered by both the insulating nature of elemental sulfur (i.e., molecular S-8) and the shuttling effect or sluggish redox kinetics of lithium polysulfide intermediates (Li2Sn, 3 <= n <= 8). In this paper, a three-dimensional mesoporous reduced graphene oxide-based nanocomposite, with the embedding of metallic Co nanoparticles and the doping of elemental N (Co/NrGO), and its simply ground mixture with powdered S at a mass ratio of 1:6 (Co/NrGO/S) are prepared and used as cathode-/separator-coated interlayers and working electrodes in assembled Li-S cells, respectively. One of the effective cell configurations is to paste composite Co/NrGO onto both the S-loading cathode and separator, showing good cycling stability (1070 mAh g(-1) in the 100th cycle at 0.2 C), high-rate capability (835 mAh g(-1), 2.0 C), and excellent durability (905 mAh g(-1) in the 250th cycle at 0.5 or 0.2 C). Compared with the experimental results of Co-absent NrGO, electrochemical properties of various Co/NrGO-based cell configurations clearly show multiple functions of Co/NrGO, indicating that the absence of Co/NrGO coatings and/or Co nanoparticles may be inadequate to achieve superior S availability of assembled Li-S batteries.