Bi doping induces the quantum dots to improve the supercapacitor performance of cobalt carbonate hydroxide hydrate

Cobalt carbonate hydroxide has been widely used in supercapacitor electrodes because of its excellent theoretical electrochemical properties and easy synthesis. However, in actual synthesis, its excellent electrochemical properties are often weakened due to its oxide-like properties, which restricts its further development. Herein, the Bi heteroatoms are introduced into the Co(CO3)0.5(OH)·0.11H2O, which not only modifies the microstructure, but also induces the formation of quantum dots, thus improving the performance of supercapacitors. By regulating the doping amount of Bi, the optimized Co/Bi-3:1 exhibits a specific capacitance of 680 F g−1 at 1 A g−1, which is 5.74 times than the pristine Co(CO3)0.5(OH)·0.11H2O. Furthermore, the assembled Co/Bi-3:1//activated carbon soft-pack asymmetric supercapacitor has a relatively superior power density (10547.58 W kg−1, relative to 14.06 Wh kg−1 energy density) and energy density (17.83 Wh kg−1, relative to 2146.76 W kg−1 power density). The present study demonstrates that Bi doping not only facilitates the formation of quantum dots and enhances electron conduction ability, but also regulates the microscopic morphology, thereby enhancing the electrochemical energy storage capacity of cobalt carbonate hydroxide hydrate electrode materials. [Display omitted] •Bi doping induced the formation of Bi2O2CO3 quantum dots.•The deposition of quantum dots significantly improves the conductivity.•The microstructure of Co(CO3)0.5(OH)·0.11H2O was regulated by Bi doping.•The optimized Co/Bi-3:1 exhibits specific capacitance of 680 F g−1.