Mn3O4 nano-octahedrons embedded in nitrogen-doped graphene oxide as potent anode material for lithium-ion batteries.

Mn3O4 nano-octahedrons embedded in N-doped graphene oxide (MNGO) nanosheets were synthesized using a simple, energy-efficient, and rapid microwave-digested hydrothermal route in a single step. The structural and morphological aspects of synthesized materials were evaluated by XRD, IR, Raman, FE-SEM, and HR-TEM techniques. Then, the composite MNGO was tested for its Li-ion storage properties and compared with reduced graphene oxide (rGO) and Mn3O4 materials. The MNGO composite exhibited superior reversible specific capacity, excellent cyclic stability, and outstanding structural integrity throughout the electrochemical studies. The MNGO composite showed a reversible capacity of 898 mA h g-1 after 100 cycles at 100 mA g-1 and Coulombic efficiency of 97.8%. Even at a higher current density of 500 mA g-1, it exhibits a higher specific capacity of 532 mA h g-1 (~1.5 times higher than commercial graphite anode). These results demonstrate that Mn3O4 nano-octahedrons embedded on N-doped GO are a highly durable and potent anode material for LIBs. Supplementary Information: The online version contains supplementary material available at 10.1007/s11581-023-05035-6.

Facile hydrothermal synthesis of urchin-like cobalt manganese spinel for high-performance supercapacitor applications.

A facile hydrothermal method has been adopted to synthesize the spherical urchin-like hierarchical CoMn2O4 nanostructures on the nickel foam substrate. The as-synthesized urchins have an average diameter of ∼3-7µm with numerous self-assembled nanoneedles grown radically in all the directions from its center with a huge void space between them. For comparison, we have also studied the electrochemical as well as other physicochemical properties of parent simple Co3O4 and MnO2 materials, which were also synthesized by a similar hydrothermal method. The results show that CoMn2O4 electrode displayed significantly higher (more than two times) areal and specific capacitances compared to Co3O4 and MnO2 electrodes with excellent capacitance retention and Coulombic efficiency. Moreover, the energy and power densities obtained for CoMn2O4 electrode are also far higher than the parent Co3O4 and MnO2. Long-term cycling tests of CoMn2O4 electrode shows the improved capacitance with high rate capability up to 6000 cycles indicating their potential for high performance supercapacitor applications. The better electrochemical performance of CoMn2O4 electrode can be attributed to the smart urchin-like nanostructures, which has several advantages like, more electroactive sites for faradic reactions emerging from the two metal ions, higher electronic/ionic conductivity and fast electrolyte transportation kinetics promoted by unique morphology.