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 S8) 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. Aside from the simple grinding of as‐obtained Co/NrGO with powdered sulfur at a 1:6 mass ratio, an appropriate cell configuration yields multifunctional Co/NrGO for high‐performance Li–S batteries.