Co 3 Se 4 quantum dots encapsulated with nitrogen-doped porous nanocarbon as ultrastable electrode material for water-based all-solid asymmetric supercapacitors.

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 Co ₃ Se ₄ quantum dots (NCCS-QDs) composite is prepared as the cathode material of supercapacitor. The formation of Co ₃ Se ₄ quantum dots complies with a size minimization strategy to speed up ion transport. At the same time, the Co _0.85 Se nanosheets are converted into Co ₃ Se ₄ 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.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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