Carbon quantum dots modified and Y³⁺ doped Ni₃(NO₃)₂(OH)₄ nanospheres with excellent battery-like supercapacitor...

Supercapacitor is an important energy storage device widely used in the automobile industry, military production, and communication equipment because of its fast charge-discharge rate, and high power density. Herein, carbon quantum dots modified and Y³⁺ doped Ni₃(NO₃)₂(OH)₄ (NiY@CQDs) nanospheres are prepared by a solvothermal method and used as an electrode material. The electrochemical properties of NiY@CQDs were measured in a three-electrode system. An asymmetric supercapacitor (ASC) cell was assembled with activated carbon (AC) as the anode and NiY@CQDs as the cathode. The electrochemical properties of the ASC device were measured in a two-electrode system. Experimental results show the shape of NiY@CQDs is petal-shaped and the introducing carbon quantum dots and doping Y³⁺ significantly increases the specific surface area, conductivity, and specific capacitance of Ni₃(NO₃)₂(OH)₄. The mass-specific capacitance of NiY@CQDs reaches up to 2944 F g^-1 at a current density of 1 A g^-1. The asymmetric supercapacitor of NiY@CQDs//AC has a high energy density of 138.65 Wh kg^-1 at a power density of 1500 W kg^-1, displaying a wide range of application prospects in the energy storage area.