Synthesis of NiCo2O4 microflowers by facile hydrothermal method: Effect of precursor concentration

Microplotter Printing of a Miniature Flexible Supercapacitor Electrode Based on Hierarchically Organized NiCo2O4 Nanostructures

“…For example, in papers [ 63 , 66 ], it was previously shown that electrode materials based on nickel-cobalt spinel with a nanorod structure exhibit increased capacitance values as compared to their analogs consisting of nanoplates and microspheres since they enable stabilization of the material volume change during incorporation/extraction of hydroxide ions into it according to schematic reactions 3–5. At the same time, combining such nanorods into spherical agglomerates, as shown in the studies [ 41 , 67 ], can give an additional increase in the capacitance due to a three-dimensional mesoporous network formation, providing an increased contact area between electrolyte ions and the electrode material surface, as well as ensuring additional pathways of space charge transfer.…”

“…According to the literature, one of the most promising and popular methods for obtaining hierarchically organized oxide nanostructures is hydrothermal synthesis, which enables the formation of the widest range of different morphologies: hollow spheres [ 31 ], nanotubes, nanofibers and nanorods [ 25 , 32 , 33 , 34 ], nanosheets and plate-like structures [ 35 , 36 , 37 ], or nanoflowers [ 26 , 38 , 39 ], both as nanopowders and as coatings. At the same time, a number of papers [ 40 , 41 ] note the high potential of the NiCo 2 O 4 microstructure, consisting of nanorods organized in the form of spheres (“urchin-like” microstructure), with respect to improving the electrochemical characteristics of their supercapacitor electrodes (high specific capacitance values, low charge transfer resistance, and increased cyclic stability).…”

Electrode Materials, Structural Design, and Storage Mechanisms in Hybrid Supercapacitors

“…Generally, multi-metal compounds can be divided into multi-metal oxides, sulfides, and hydroxides. Multi-metal oxides, such as NiCo 2 O 4 [ 121 , 122 , 123 ], ZnCo 2 O 4 [ 124 , 125 , 126 , 127 ], MnMoO 4 [ 128 , 129 , 130 ], and CoMoO 4 [ 131 , 132 , 133 , 134 ], have been widely explored for energy conversion and storage. Among these multi-metal oxides, the NiCo 2 O 4 nanomaterials have attracted increasing attention due to their merits of higher electrical conductivity, and higher electrochemical activity, which would offer richer redox reactions, including contributions from both Ni 2+ /Ni 3+ and Co 3+ /Co 4+ redox couples in the materials [ 121 , 122 , 123 ].…”

“…Multi-metal oxides, such as NiCo 2 O 4 [ 121 , 122 , 123 ], ZnCo 2 O 4 [ 124 , 125 , 126 , 127 ], MnMoO 4 [ 128 , 129 , 130 ], and CoMoO 4 [ 131 , 132 , 133 , 134 ], have been widely explored for energy conversion and storage. Among these multi-metal oxides, the NiCo 2 O 4 nanomaterials have attracted increasing attention due to their merits of higher electrical conductivity, and higher electrochemical activity, which would offer richer redox reactions, including contributions from both Ni 2+ /Ni 3+ and Co 3+ /Co 4+ redox couples in the materials [ 121 , 122 , 123 ]. For example, Shen et al [ 135 ] that reported the highly uniform NiCo 2 O 4 hollow spheres exhibited a high specific capacity of 541 C g −1 at 1 A g −1 , and excellent rate performance (74.8% of capacity retention from 1 A g −1 to 15 A g −1 ).…”