Cobalt-doped hierarchical porous carbon materials with spherical chrysanthemum-like structures that are derived from the PVP-assisted synthesis of metal organic frameworks for advanced Li-S batteries

Porous carbon materials with spherical chrysanthemum-like structures can be self-doped with low-cost cobalt (Co-SCPC) by carbonizing metal organic framework materials (MOFs) at high temperatures with PVP (polyvinyl pyrrolidone) as a template in an inert atmosphere. The unique multilevel structure of zero-dimensional hollow spheres and two-dimensional overlapping lamellae effectively alleviates the shuttle effect of polysulfides by physical encapsulation. The optimized porous carbon material exhibits a high specific surface area and abundant mesopores and macropores, which is conducive to the dispersion of active materials, rapid transfer of Li+ and improvement of the utilization of elemental sulfur. Moreover, cobalt doping with coordinately unsaturated metal sites can enhance the interaction between the matrix material and polysulfides, further catalyze the conversion reaction of active materials and improve the rate performance of Li-S batteries. Co-SCPC as the cathode matrix material exhibits high initial capacities of 1292.5 and 992.7 mAh g−1 at 0.1 C and 1 C, respectively. The remaining capacity is 402.1 mAh g−1 after 1500 cycles at 1 C. Furthermore, the battery also shows an outstanding rate performance, with an initial capacity of 416.4 mAh g−1 and a remaining capacity of 339.7 mAh g−1 after 500 cycles at a rate of 5 C.