We investigate the principal elements affecting the properties of bimetallic oxide electrodes to reveal the relevant energy storage mechanisms.

Two types of porous cobalt manganese oxide nanowires (MnCo₂O₄ and CoMn₂O₄) with different structures have been successfully synthesized by thermal decomposition of organometallic compounds for the first time. Nitrilotriacetic acid (NA) was used as a chelating agent to coordinate Co(II) and Mn(II) ions in various molar ratios, in a hydrothermal condition. The microstructure of as-synthesized cobalt manganese oxides, composed of numerous nanoparticles, completely retains the 1D network structure of the Co–Mn–NA coordination precursors without structure collapse. Electrochemical properties of the cobalt manganese oxide materials have been tested for supercapacitors at room temperature. Both the MnCo₂O₄ and CoMn₂O₄ electrodes display the outstanding capacitive behaviors and superior electrochemical properties. The CoMn₂O₄ nanowire shows excellent capacitance and desirable rate performance (2108 F g⁻¹ at 1 A g⁻¹ and 1191 F g⁻¹ at 20 A g⁻¹) compared to that of the MnCo₂O₄ nanowire (1342 F g⁻¹ at 1 A g⁻¹ and 988 F g⁻¹ at 20 A g⁻¹). Electrochemical impedance spectra (EIS) results also reconfirm that the CoMn₂O₄ nanowires display more facile electrolyte diffusion and higher capacitor response frequency than MnCo₂O₄ nanowires. This can be ascribed to the facile electrolyte/OH⁻ ion penetration and better Faradaic utilization of the electroactive surface sites that generated by the smaller particle size and higher surface area.

Nitrogen-doped carbon coated Co ₃ O ₄ nanoparticles (Co ₃ O ₄ @NC) with high Na-ion storage capacity and unprecedented long-life cycling stability are reported in this paper.

Three-dimensional flower-like NiCo2O4 hierarchitectures have been successfully prepared on a large scale via a facile solvothermal method followed by an annealing process. The as-synthesized NiCo2O4 flower-like architectures have uniform diameters of about 500 nm assembled by numerous nanosheets radially grown from the center. The possible growth mechanism of the unique structures has been investigated. Both the poly(vinylpyrrolidone) (PVP) surfactant and the formation of metal glycolate play important roles in the formation of these novel three-dimensional flower-like hierarchitectures. With a large surface specific area of 212.6 m2 g−1, this novel NiCo2O4 material exhibited a superior specific capacitance of 1191.2 F g−1 and 755.2 F g−1 at current densities of 1 and 10 A g−1, respectively, which suggests that 63.4% of the capacitance is still retained when the charge–discharge rate is increased from 1 A g−1 to 10 A g−1. This superior electrochemical performance of NiCo2O4 as an electrode material for supercapacitors can be ascribed to the synergetic effect of the porous structure and the small diffusion lengths in the nanosheet building blocks. The simple, versatile and cost-effective route reported here may provide a general methodology for the high-yield synthesis of metal cobaltite nanostructures featuring improved properties and structures.

Ni₂P nanoparticles grown on reduced graphene oxide (rGO) were successfully synthesized via the low-temperature solid state reaction method and investigated as electrochemical pseudocapacitor materials for potential energy storage applications. The specific capacitance of the as-prepared Ni₂P/rGO is 2266 F g⁻¹ and the Ni₂P/rGO composite also exhibits superior cycling performance when they are used as the capacitor materials. The as-prepared Ni₂P/rGO sample demonstrates interesting supercapacitive properties with high capacitance and good cycling performance.