Nitrogen-Doped Graphene-Supported Mixed Transition-Metal Oxide Porous Particles to Confine Polysulfides for Lithium-Sulfur Batteries

The intricate charge-discharge reactions and bad conductivity nature of sulfur determine the extreme importance of cathode engineering for Li-S batteries. Herein, spinel ZnCo2O4 porous particles@N-doped reduced graphene oxide (ZnCo2O4@N-RGO) are prepared via the combined procedures of refluxing and hydrothermal treatment, consisting of interconnected uniform ZnCo2O4 nanocubes with an average size of 5 nm anchored on graphene nanosheets. The as-obtained composite can act as an inimitable cathode scaffold to suppress the shuttling of polysulfides by chemical confinement of ZnCo2O4 and N-RGO for the first time, as demonstrated by the adsorption energy of ZnCo2O4 to Li2S4 via the strong chemical bonding between Zn or Co and S. The RGO nanosheets with a relatively high specific surface area provide a good conductive network and structural stability. The introduction of doped N atoms and numerous ZnCo2O4 porous nanoparticles can inhibit the transfer of lithium polysulfides between the cathode and anode. Due to the unique structural and compositional features, the as-obtained hybrid materials with the high sulfur loading of 71% and even 82% still deliver high specific capacity, good rate capability, and enhanced cycling stability with exceptionally high initial Coulombic efficiency, which displays a high utilization of sulfur.