NiCo2O4 Nanoneedle Research Articles

Carbon- and Binder-Free NiCo2O4 Nanoneedle Array Electrode for Sodium-Ion Batteries: Electrochemical Performance and Insight into Sodium Storage Reaction

Sodium (Na)-ion batteries (NIBs) have attracted significant interest as an alternative chemistry to lithium (Li)-ion batteries for large-scale stationary energy storage systems. Discovering high-performance anode materials is a great challenge for the commercial success of NIB technology. Transition metal oxides with tailored nanoarchitectures have been considered as promising anodes for NIBs due to their high capacity. Here, we demonstrate the fabrication of a nanostructured oxide-only electrode, i.e., carbon- and binder-free NiCo2O4 nanoneedle array (NCO-NNA), and its feasibility as an anode for NIBs. Furthermore, we provide an in-depth experimental study of the Na storage reaction (sodiation and desodiation) in NCO-NNA. The NCO-NNA electrode is fabricated on a conducting substrate by a hydrothermal method with subsequent heat treatment. When tested in an electrochemical Na half-cell, the NCO-NNA electrode exhibits excellent Na storage capability: a charge capacity as high as 400 mAh g−1 is achieved at a current density of 50 mA g−1. It also shows a greatly improved cycle life (~215 mAh g−1 after 50 cycles) in comparison to a conventional powder-type electrode (~30 mAh g−1). However, the Na storage performance is still inferior to that of Li, which is mainly due to sluggish kinetics of sodiation–desodiation accompanied by severe volume change.

1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability.

The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo2S4 nanotube array/carbon aerogel and NiCo2O4 nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo2S4 nanotube array/carbon aerogel and NiCo2O4 nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg-1 and 47.5 Wh kg-1 at a power density of 400 W kg-1, respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

Mesoporous NiCo2O4 nanoneedles grown on three dimensional graphene networks as binder-free electrode for high-performance lithium-ion batteries and supercapacitors

Mesoporous nickel cobaltite (NiCo2O4) nanoneedles grown on three dimensional graphene networks have been successfully prepared by a facile solvothermal reaction with subsequent annealing treatment. The NiCo2O4/3DGN hybrid is then used as binder-free electrode for high-performance lithium-ion batteries and supercapacitors. The three dimensional graphene based binder-free electrode is considered more desirable than powder nanostructures in terms of shorter Li+ ion diffusion and electron transportation paths, good strain accommodation, better interfacial/chemical distributions and high electrical conductivity. As a result, when used as an anode material for lithium-ion batteries (LIBs), it exhibits high specific discharge capacity as well as superior cycling stability up to 2000 cycles. When it is used for supercapacitor application, this hybrid delivers a high specific capacitance of 970Fg−1 at a high current density of 20Ag−1 with excellent capacitance retention of ∼96.5% after 3000 cycles. Moreover, this synthesis strategy is simple and effective, which could be extended to the construction of other three dimensional graphene based metal oxides hybrid for energy applications.

Hierarchical three-dimensional NiCo2O4 nanoneedle arrays supported on Ni foam for high-performance supercapacitors

A novel NiCo2O4 nanoneedle arrays with bottom crosslinked nanosheets grew on Ni foam as advanced binder-free electrodes via a facile one-step hydrothermal method followed by annealing in air, which exhibited high electrochemical performance.

Mesoporous NiCo2O4 nanoneedles grown on 3D graphene-nickel foam for supercapacitor and methanol electro-oxidation

Mesoporous NiCo2O4 nanoneedles were directly grown on three dimensional (3D) graphene-nickel foam which was prepared by chemical vapor deposition, labeled as NCO/GNF. The structure and morphology of NCO/GNF were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, element mapping and Raman spectroscopy. The NCO/GNF was employed as electrodes for supercapacitor and methanol electro-oxidation. When used for supercapacitor, the NiCo2O4 nanoneedles exhibit hi exhibit high specific capacitance (1588Fg−1 at 1Ag−1), high power density and energy density (33.88Whkg−1 at 5kWkg−1) as well as long cycling stability. In methanol electro-oxidation, the NiCo2O4 nanoneedles deliver high electro-oxidation activity (93.3Ag−1 at 0.65V) and electro-oxidation stability. The good electrochemical performance of NiCo2O4 nanoneedles is attributed to the 3D structure with large specific area, high conductivity and fast ions/electrons transport.

Water Oxidation on Spinel NiCo2O4 Nanoneedles Anode: Microstructures, Specific Surface Character, and the Enhanced Electrocatalytic Performance

Aiming to improve the electrochemical catalytic performance of the spinel NiCo2O4 as water oxidation catalyst, solvothermal method was employed in this work to fabricate NiCo2O4 directly on conductive substrate FTO as integrated anode. By simply altering the solvent in the precursor solution, NiCo2O4 with different morphology was obtained. The electrocatalytic water oxidation behavior of both NiCo2O4 nanoneedles (NNs) and NiCo2O4 nanosheets (NSs) were investigated in analytical scale, and the results showed that NiCo2O4 NNs exhibited enhanced catalytic performance with lower onset potential, larger current density, and faster kinetics in water oxidation process compared with NiCo2O4 NSs. Meanwhile, both the anodes presented excellent stability in the basic conditions which favored oxygen evolution. The reasons for the superior catalytic activity of NiCo2O4 NNs were also discussed in depth by investigating the surface elements composition and distribution, as well as the different chemical state of the surface adsorbed oxygen. It suggested that the NiCo2O4 NNs anode surface which was better hydroxylated and had more physic- and chemisorbed water was beneficial for enhanced water oxidation performance. It was believed that the present work may provide valuable experimental foundation and an exemplary method for improving the activity of water oxidation catalyst.

Hierarchical mesoporous nickel cobaltite nanoneedle/carbon cloth arrays as superior flexible electrodes for supercapacitors

Hierarchical mesoporous NiCo2O4 nanoneedle arrays on carbon cloth have been fabricated by a simple hydrothermal approach combined with a post-annealing treatment. Such unique array nanoarchitectures exhibit remarkable electrochemical performance with high capacitance and desirable cycle life at high rates. When evaluated as an electrode material for supercapacitors, the NiCo2O4 nanoneedle arrays supported on carbon cloth was able to deliver high specific capacitance of 660 F g-1 at current densities of 2 A g-1 in 2 M KOH aqueous solution. In addition, the composite electrode shows excellent mechanical behavior and long-term cyclic stability (91.8% capacitance retention after 3,000 cycles). The fabrication method presented here is facile, cost-effective, and scalable, which may open a new pathway for real device applications.

NiCo2O4 nanostructure materials: morphology control and electrochemical energy storage.

Three types of NiCo2O4 nanostructure, homogeneous NiCo2O4 nanoneedle arrays, heterogeneous NiCo2O4 nanoflake arrays and NiCo2O4 nanoneedle-assembled sisal-like microspheres are synthesized via facile solution methods in combination with thermal treatment. The NiCo2O4 nanoneedle arrays are evaluated as supercapacitor electrodes and demonstrate excellent electrochemical performances with a high specific capacitance (923 F g(-1) at 2 A g(-1)), good rate capability, and superior cycling stability. The superior capacitive performances are mainly due to the unique one dimensional porous nanoneedle architecture, which provides a faster ion/electron transfer rate, improved reactivity, and enhanced structural stability. The fabrication method presented here is facile, cost-effective and scalable, which may open a new pathway for real device applications.

Single-crystalline NiCo2O4 nanoneedle arrays grown on conductive substrates as binder-free electrodes for high-performance supercapacitors

In this work, we have successfully grown single-crystalline nanoneedle arrays of NiCo2O4 on conductive substrates such as Ni foam and Ti foil through a simple solution method together with a post-annealing treatment. Remarkably, the NiCo2O4–Ni foam binder-free electrode exhibits greatly improved electrochemical performance with very high capacitance and excellent cycling stability.