Co₃Se₄ quantum dots encapsulated with nitrogen-doped porous nanocarbon as ultrastable electrode material for...

Transition metal selenides (TMSe) are considered as potential anode materials for supercapacitors because of their abundant reserves and high safety.However, their poor conductivity limits their high rate performance and stability.In this paper, an N-doped porous nanocarbon-coated Co₃Se₄ quantum dots (NCCS-QDs) composite is prepared as the cathode material of supercapacitor. The formation of Co₃Se₄ quantum dots complies with a size minimization strategy to speed up ion transport. At the same time, the Co_0.85Se nanosheets are converted into Co₃Se₄ quantum dots, avoiding the collapse of the nanosheets during the electrochemical process. In addition, the porous nanocarbon coating increases the number of active sites and the contact area between the electrode and the electrolyte, which can provide more ion transport channels and pore sizes, while avoiding the generation of inactive clusters in the electrochemical reaction of quantum dots. The as-assembled NCCS-QDs-2//AC ASCs devices demonstrate excellent electrochemical performance with an energy density of 84.59 Wh kg^-1 at a power density of 799.99 W kg^-1.At the same time, the ASCs device showed excellent cycle stability, with 95.6% of the initial capacitance still maintained after 15,000 charge and discharge cycles.The excellent electrochemical performance of NCCS-QDs-2//AC ASC device proves that NCCS-QDs composite material has a broad application prospect in the cathode material of supercapacitor.