Fabrication of Co-Fe-Mn composites with a mixed-dimensional structure for applications in high-performance supercapacitors

Reasonably regulating the dimensionality and interface of an electrode material can effectively improve its surface chemical reactivity, charge transfer rate, and ion transport performance, which is crucial to solving several problems with supercapacitors, including low energy density and poor cycle stability. The multidimensional hybrid morphology of Co-Fe carbonate hydroxide (CH) coupled with Co-Mn layered double hydroxide (LDH) is generated directly on the nickel foam substrate by a two-stage process. The prepared multidimensional hybrid materials with pore morphology with the synergistic effect of 1D nanorods, 2D nanosheets, and 3D “porous coral” not only ensure sufficient contact between the electrolyte and electrode material but also enhance the charge transfer and ion diffusion of the electrolyte. The strong coupling effect of Co, Fe, and Mn metals between the heterojunction surface can produce various ionic valence states and high conductivities, resulting in increased redox activity, which thus improves the electrochemical performance. The results of the electrochemical performance test show that when the current density is 10 mA cm−2, the high area-specific capacitance of 7.33 F cm−2 is two times (3.85 F cm−2) that of a Co-Fe CH electrode and five times that of a Co CH electrode. The quasi-solid state asymmetric supercapacitor with a Co-Fe-Mn positive electrode and an active carbon negative electrode displays an energy density of 0.723 mWh cm−2 at a power density of 8.53 mW cm−2. After 5500 cycles, the apparatus exhibits 101.72 % of the initial capacitance, which can effectively drive small electrical appliances. The results indicate that the supercapacitor exhibits excellent cycle stability and application potential in energy storage.