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

Abstract 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 Y 3+ doped Ni 3 (NO 3 ) 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 Y 3+ significantly increases the specific surface area, conductivity, and specific capacitance of Ni 3 (NO 3 ) 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.