Template-free synthesis of hierarchical mixed-metal cobaltites: Electrocapacitive and Theoretical study

Vertically Aligned ZnCo2O4 Nanoplates on Ti3C2 for High-Efficiency Hybrid Supercapacitors

Electrode materials marking higher structural stability, and electrochemical activity remain the priority in improving the electrochemical performance of supercapacitors (SCs). Herein we report the designed synthesis of novel nanoplate-on-nanosheet architecture...

Proton solvent-controllable synthesis of manganese oxalate anode material for lithium-ion batteries

Manganese oxalates with different structures and morphologies were prepared by the precipitation method in a mixture of dimethyl sulfoxide (DMSO) and proton solvents. The proton solvents play a key role in determining the structures and morphologies of manganese oxalate. Monoclinic MnC2O4·2H2O microrods are prepared in H2O-DMSO, while MnC2O4·H2O nanorods and nanosheets with low crystallinity are synthesized in ethylene glycol-DMSO and ethanol-DMSO, respectively. The corresponding dehydrated products are mesoporous MnC2O4 microrods, nanorods, and nanosheets, respectively. When used as anode material for Li-ion batteries, mesoporous MnC2O4 microrods, nanorods, and nanosheets deliver a capacity of 800, 838, and 548 mA h g-1 after 120 cycles at 8C, respectively. Even when charged/discharged at 20C, mesoporous MnC2O4 nanorods still provide a reversible capacity of 647 mA h g-1 after 600 cycles, exhibiting better rater performance and cycling stability. The electrochemical performance is greatly influenced by the synergistic effect of surface area, morphology, and size. Therefore, the mesoporous MnC2O4 nanorods are a promising anode material for Li-ion batteries due to their good cycle stability and rate performance.

Preparation and electrochemical properties of nanostructured porous spherical NiCo2O4 materials

Porous spherical NiCo2O4 powders with a micro-nano structure were prepared by the spray drying method using citric acid as the chelating agent and soluble salts as cobalt and nickel sources. By calcination at 300 °C, spherical and single-phase spinel-type NiCo2O4 powders were obtained. The powders with particle sizes of 0.5-3 μm were aggregations of nano-sized grains (about 15-30 nm). The electrical property tests demonstrated that the synthesized NiCo2O4 has a specific capacitance of 430.67 F g-1 at a current density of 1 A g-1 and a capacitance retention rate of 100% after 3000 cycles at a current density of 4 A g-1, indicating excellent cycling stability. On assembly into an asymmetric supercapacitor device, a specific capacitance of 37.06 F g-1 and energy density of 13.18 W h kg-1 at a power density of 800 W kg-1 and a current density of 1 A g-1 were demonstrated. The micro-nano structured porous NiCo2O4 powders have a larger specific surface area, which can allow the sample to come in full contact with the electrolyte. The nanopore channels are favourable for releasing the lattice distortion stress during the charge-discharge process, maintaining the structural stability of the crystal and improving the cycle life.