Bi₂O₃@Bi₂O₂CO₃ Heterostructure Electrode for Significant Enhancement of Electrochemical Capacity

Bi 2 O 3 is increasingly used in supercapacitors because of its high theoretical specific capacitance, but poor inherent conductivity and poor ion diffusion limit its actual capacitance. Therefore, the rational design of the surface and structure of Bi 2 O 3 is the key to improve the specific capacitance of Bi 2 O 3 . Here, we report the fabrication of high-performance negative electrodes from Bi 2 O 2 CO 3 nanosheets wrapped around Bi 2 O 3 arrays (Cu foam@Bi 2 O 3 @Bi 2 O 2 CO 3 ) by a combination of electrical substitution, oxidative calcination, and hydrothermal methods. The realized Cu foam@Bi 2 O 3 @Bi 2 O 2 CO 3 presents a surface cross-linked laminar structure, which shortens the electrolyte penetration path. The direct replacement growth of Bi on copper substrates to obtain subsequent composites allows for enhanced adhesion between the electrode material and the collector, facilitates charge transfer to the electrode material, and achieves ultrahigh loadings (13.2 mg cm –2 ). In addition, the constructed asymmetric supercapacitor has a maximum energy density of 1.6 mW h cm –2 (45.5 W h kg –1 ) at a power density of 6.2 mW cm –2 (175.9 W kg –1 ). This work provides a simple design strategy to enhance the electrochemical performance of Bi 2 O 3 .