Three-Dimensional Co-S-P Nanoflowers as Highly Stable Electrode Materials for Asymmetric Supercapacitors

Three-dimensional P-doped Co₉S₈/CoO (denoted as Co-S-P) nanoflowers are designed and synthesized via a phosphor doping method. Because of the novel structures and the ultrathin nanosheets, the electrode materials supply rapid charge transmission rate, shortened ion diffusion length, and large electroactive specific area, resulting in outstanding electrochemical performance. As a supercapacitor electrode active material, the Co-S-P exhibits outstanding pseudocapacitive performance with a specific capacitance of 969.5 F g^-1 at 1 A g^-1 and 775 F g^-1 at 20 A g^-1 and approximately 105% capacity retention after 30※000 cycles at 20 A g^-1. As expected, an asymmetric supercapacitor was configured on the basis of the obtained Co-S-P and activated carbon electrode, which showed a high energy density of 17.9 Wh kg^-1 at 266 W kg^-1 and remained 97.9% of initial specific capacitance after 10※000 cycles.