3-dimensional porous NiCo2O4 nanocomposite as a high-rate capacity anode for lithium-ion batteries

Morphology-Tunable Binary Transition Metal Oxide Heterostructure@Carbon Composites for Lithium-Ion Batteries

Heterostructures of binary and unary transition metal oxides (B and UTMOs) have demonstrated excellent electrochemical performance in lithium-ion batteries (LIBs) due to synergistic effects; however, there remains a lack of research combining multiple strategies for synergy enhancement. Herein, we present the development of crystallinity-controlled heterostructures based on nickel and cobalt oxides (NiCo2O4/NiO and NiO/Co3O4) with different morphologies (urchin- and flower-like structures, e.g., U-NiCo2O4/NiO and F-NiCo2O4/NiO) to investigate the influence of heterostructure combinations and morphologies on electrochemical performance in LIBs. The morphologies of the heterostructures were controlled by adjusting the fluoride concentration during the synthesis of the nickel-cobalt (Ni-Co) precursor, while heterostructure combinations were regulated by heat treatment under specific conditions. When used as anodes for LIBs, electrochemical analyses revealed that the carbon-coated urchin-like U-NiCo2O4/NiO (U-NiCo2O4/NiO@C) sample provided more efficient charge transfer and a shorter Li-ion transport pathway compared to its counterpart (F-NiCo2O4/NiO@C) due to its high surface area and distinctive morphological features. In addition, U-NiCo2O4/NiO@C exhibited superior electrochemical performance as an anode in LIBs than U-NiO/Co3O4@C, indicating that the advantageous effects of BTMO over UTMO can effectively enhance LIB performance. This facile synthesis approach provides a foundation for morphology-controlled heterostructures in the development of high-performance anode materials for LIB applications.

Research on Interfacial Construction and Energy Storage Performance of Polymetallic Heterostructure Based on Zn-Ni 3d Orbital Modulation and DFT Study

In this study, ZnCo2O4 nanosheets and NiCo2O4 nanowires were successfully grown on nickel foam as anode materials for lithium-ion batteries by a low-temperature hydrothermal and immersion method. The nanosheets offered an enlarged electrically active surface area, and the nanowires provided support for the nanosheets, thereby forming a heterojunction interface. The ZnCo2O4/NiCo2O4 heterojunction demonstrated favorable electrochemical performance in electrochemical tests. In terms of its rated performance, the capacity of the composite electrode recovered to 1050 mAh g-1 when the current density ranged from 0.1 to 1 A g-1; its capacity was maintained even when the current density returned to 0.1 A g-1 after 60 cycles. The diffusion coefficient of lithium ions (DLi+) increased due to the reduction of the interfacial contact resistance under the interfacial electric field of the heterostructure, and they were continuously activated during repeated cycles. This further significantly enhanced the electrochemical activity of the electrode. The analysis results based on the density functional theory revealed the hybridization of the 3d orbitals of Ni and Zn and the augmented electronic state occupancy of the orbitals near the Fermi energy level. This process was accompanied by the migration of electrons, leading to a decrease in the band gap. Meanwhile, the Li+ diffusion barrier decreased, and the conductivity of the electrode materials was enhanced.

Electronic redistribution through the interface of MnCo2O4-Ni3N nano-urchins prompts rapid In situ phase transformation for enhanced oxygen evolution reaction

One of the most coveted objectives in the realm of energy conversion technologies is the development of highly efficient and economically viable electrocatalysts for the oxygen evolution reaction. The commercialization of such techniques has thus far been impeded by their slow response kinetics. One of the many ways to develop highly effective electrocatalysts is to judiciously choose a coupling interface that maximizes catalyst performance. In this study, the in situ electrochemical phase transformation of MnCo2O4-Ni3N into MnCo2O4-NiOOH is described. The catalyst has an exceptional overpotential of 224 mV to drive a current density of 10 mA cm-2. Strong interfacial contact is seen in the MnCo2O4-Ni3N catalyst, leading to a considerable electronic redistribution between the MnCo2O4 and Ni3N phases. This causes an increase in the valence state of Ni, which makes it an active site for the adsorption of *OH, O*, and *OOH (intermediates). This charge transfer facilitates the rapid phase transformation to form NiOOH from Ni3N. At a higher current density of 300 mA cm-2, the catalyst remained stable for a period of 140 h. DFT studies also revealed that the in situ-formed NiOOH on the MnCo2O4 surface results in superior OER kinetics compared to that of NiOOH alone.

MOF-derived nitrogen-doped porous carbon nanofibers with interconnected channels for high-stability Li+/Na+ battery anodes

Heteroatom-doped porous carbon materials have been widely used as anode materials for Li-ion and Na-ion batteries, however, improving the specific capacity and long-term cycling stability of ion batteries remains a major challenge. Here, we report a facile based metal-organic framework (MOFs) strategy to synthesize nitrogen-doped porous carbon nanofibers (NCNFs) with a large number of interconnected channels that can increase the contact area between the material and the electrolyte, shorten the diffusion distance between Li+/Na+ and the electrolyte, and relieve the volume expansion of the electrode material during cycling; the doping of nitrogen atoms can improve the conductivity and increase the active sites of the carbon material, can also affect the microstructure and electron distribution of the electrode material, thereby improving the electrochemical performance of the material. As expected, the obtained NCNFs-800 exhibited excellent electrochemical performance with high reversible capacity (for Li+ battery anodes: 1237 mA h g-1 at 100 mA g-1 after 200 cycles, for Na+ battery anodes: 323 mA h g-1 at 100 mA g-1 after 150 cycles) and long-term cycling stability (for Li+ battery anodes: 635 mA h g-1 at 2 A g-1 after 5000 cycles, for Na+ battery anodes: 194 mA h g-1 at 2 A g-1 after 5000 cycles).

Multishelled NiO/NiCo2O4 hollow microspheres derived from bimetal-organic frameworks as high-performance sensing material for acetone detection

Recently, tremendous research interest was stimulated to obtain advanced function materials with hierarchical structure and tailored chemical composition from metal-organic frameworks (MOFs) based precursors. Herein, Bimetal-organic frameworks of Ni-Co-BTC solid microspheres synthesized through hydrothermal method were acted as template to induce multishelled NiO/NiCo₂O₄ hollow microspheres by annealing treatment. When evaluated as gas sensing material, the optimal hybrid of NiO/NiCo₂O₄ (the molar ration of NiCo=1.5) multishelled hollow microspheres endowed a high sensitivity (17.86) to 100 ppm acetone with rapid response/recovery time (11/13 s) under low working temperature (160 °C) and the low detection limit reached 25 ppb. The enhanced mechanism was originated from the following aspects: the multishelled hollow architecture provided efficient diffusion path for gas molecules and sufficient active site for gas sensing reaction; the nanoscale p-p heterojunction created at NiO and NiCo₂O₄ nanoparticles interface amplified the resistance variation by tuning the potential barrier; the potent combination of the "chemical catalytic" effect of NiO and the "electrical catalytic" effect of NiCo₂O₄ improved the selective acetone detection.

Low-cost 3D porous sea-hedgehog-like NiCo2O4/C as anode for Li-ion battery

Carbon is effective additive to improve cyclic performances of transition metal oxides for lithium ion battery, while common graphene or carbon nanotube is expensive. In this study, waste of rice husk is used to prepare low cost carbon. A composite of NiCo₂O₄/carbon is synthesized via hydrothermal method plus calcination. At hydrothermal time of 6 h, the material displays 3-D sea hedgehog-like structure with radial corn cob-shaped nanorod. The NiCo₂O₄/carbon presents better rate performances, coulombic efficiency and cyclic stability than pristine NiCo₂O₄, showing stable capacity of 1018 mAhg^-1 (52.6% higher than NiCo₂O₄) after 100 cycles at 0.1 Ag^-1. For long-term cycling during 500 cycles at 0.5 Ag^-1, the composite anode exhibits a reversible capacity of ∼880 mAhg^-1, with high retention of 92.2%. The capacity is still retained ∼715 mAhg^-1 even after 1000 cycles at 1 Ag^-1.

Surfactant-Assisted Growth of a Conversion-Type Binary Metal Oxide-Based Composite Electrode for Boosting the Reversible Lithium Storage

High-performance anode materials play a crucial role in paving the development of next-generation lithium-ion batteries (LIBs). NiCo₂O₄, as a typical binary metal oxide, has been extensively demonstrated to possess higher capacity and electrochemical activity compared with a monometal oxide such as NiO or Co₃O₄. However, the advances in the application of LIBs are usually limited by the relatively low electrical conductivity and large volume change during repeated charging/discharging processes. Herein, a NiCo₂O₄@carbon nanotube (CNT) composite electrode with advanced architecture is developed through a facile surfactant-assisted synthetic strategy. The introduced polyvinyl pyrrolidone can greatly facilitate the heterogeneous nucleation and growth of the NiCo precursor on CNTs and thus benefit the uniform transformation to a well-confined NiCo₂O₄@CNT composite. The CNTs combined with NiCo₂O₄ tightly act as both a conductive network for enhancing the ion/electron transfer and a support for mitigating the volume expansion of NiCo₂O₄. As a result, the NiCo₂O₄@CNT electrode exhibits a high initial capacity of 830.3 mA h g^-1 and a good cycling stability of 608.1 mA h g^-1 after 300 cycles at 2000 mA g^-1.

An oriented laterally-growing NiCo2O4 nanowire array on a Fe2O3 microdisc as a high-capacity and excellent rate-performance secondary battery anode

A novel hierarchical composite consisting of an ordered NiCo2O4 nanowire array growing on the lateral side of a Fe2O3 microdisc is presented, which was confirmed by X-ray holography technology on a synchrotron radiation station. The composite-based Li-ion battery anode exhibits a high capacity of 1528 mA h g-1 after 200 cycles at 0.2C, a recoverable rate-performance after repeated tests, and robust mechanical properties.

MOF-derived hollow NiCo2O4 nanowires as stable Li-ion battery anodes

Although binary metal oxides with high theoretical specific capacities and power densities are widely investigated as promising anode materials for lithium-ion batteries (LIBs), their poor cycling stability and huge volume expansion largely limit their extensive application in practical electrode materials. Herein, we report a facile strategy to synthesize hollow NiCo2O4 nanowires through direct calcination of binary metal-organic frameworks (MOFs) in air. When evaluated as an anode material for LIBs, NiCo2O4 nanowires deliver a reversible capacity of 1310 mA h g-1 at a current density of 100 mA g-1 after 100 cycles. Even at a high current density of 1 A g-1, NiCo2O4 nanowires exhibit long-term cycling stability with a capacity of 720 mA h g-1 after 1000 cycles. The outstanding lithium-storage performance can be attributed to the unique structures with 1D porous channels, which are beneficial for the fast transfer of Li+ ions and electrolyte and alleviate the strain caused by the volume expansion during cycling processes.

Surfacing amorphous Ni-B nanoflakes on NiCo2O4 nanospheres as multifunctional bridges for promoting lithium storage behaviors

Transition metal oxides (TMOs) have gained enormous research interests as negative materials of next generation lithium-ion batteries due to their higher energy density, lower cost, and better eco-friendliness. However, they are prone to low electronic conductivities and dramatic volume change during charge/discharge and there is also a great challenge in realizing TMO electrodes with satisfactory LIB performances. In this study, for the first time, amorphous nickel-boride (Ni-B) was introduced into porous NiCo2O4 nanospheres by an in situ solution growth route to overcome the existing issues. The coated Ni-B component could not only function as anchors for NiCo2O4 nanospheres to suppress the severe volume expansion but could also act as effective electron-conducting bridges to promote fast electron/charge transfer. Furthermore, the existence of abundant mesopores centered at ∼6.5 nm in this composite could effectively suppress the severe volume variations in the lithiation/delithiation process. As expected, the NiCo2O4@Ni-B composites delivered a high reversible capacity of 1221 mA h g-1 at 0.2 A g-1 and 865 mA h g-1 at 0.5 A g-1 over 500 cycles; more impressively, at the high rate of 5 A g-1, a capacity of 648 mA h g-1 could be also obtained, showing its good rate capability. As a result, these results demonstrated an effective and facile way to design conversion-type negative electrode materials with superior lithium storage properties.

Binder-free C@NiCo2O4 on Ni foam with ultra-stable pseudocapacitive lithium ion storage

Carbon-coated nickel cobaltate on nickel foam (C@NCO@NF) with stable pseudocapacitive lithium storage capacity was prepared via a two-step strategy. NiCo hydroxide was initially grown on Ni foam via electrodeposition. Subsequent glucose soaking and annealing converted the intermediate into C@NCO@NF. Carbon coating could significantly improve the cycling stability and rate performance of the binder-free anode. The C@NCO@NF electrode could stably deliver a reversible capacity of 513 mAh · g^-1 after 500 cycles at a current density of 500 mA · g^-1. It could even stably cycle at a high current density of 5000 mA · g^-1 for 3000 cycles, with a reversible capacity of 115 mAh · g^-1. Kinetic analysis revealed that surface-controlled pseudocapacitance plays a dominant role in the lithium ion storage. Improved electrochemical performance is attributed to the synergetic effect of pseudocapacitance and carbon coating.

3D plum candy-like NiCoMnO4@graphene as anodes for high-performance lithium-ion batteries

3D plum candy-like NiCoMnO4 microspheres have been prepared via ultrasonic spraying and subsequently wrapped by graphene through electrostatic self-assembly. The as-prepared NiCoMnO4 powders show hollow structures and NiCoMnO4@graphene exhibits excellent electrochemical performances in terms of rate performance and cycling stability, achieving a high reversible capacity of 844.6 mA h g-1 at a current density of 2000 mA g-1. After 50 cycles at 1000 mA g-1, NiCoMnO4@graphene delivers a reversible capacity of 1045.1 mA h g-1 while the pristine NiCoMnO4 only has a capacity of 143.4 mA h g-1. The hierarchical porous structure helps to facilitate electron transfer and Li-ion kinetic diffusion by shortening the Li-ion diffusion length, accommodating the mechanical stress and volume change during the Li-ion insertion/extraction processes. Analysis from the electrochemical performances reveals that the enhanced performances could be also attributed to the reduced charge-transfer resistance and enhanced Li-ion diffusion kinetics because of the graphene-coating. Moreover, Schottky electric field, due to the difference in work function between graphene and NiCoMnO4, might be favorable for the redox activity of the NiCoMnO4. In light of the excellent electrochemical performance and simple preparation, we believe that 3D plum candy-like NiCoMnO4@graphene composites are expected to be applied as a promising anode materials for high-performance lithium ion batteries.

Porous Hollow Superlattice NiMn2O4/NiCo2O4 Mesocrystals as a Highly Reversible Anode Material for Lithium-Ion Batteries

As a promising high-capacity anode material for Li-ion batteries, NiMn₂O₄ always suffers from the poor intrinsic conductivity and the architectural collapse originating from the volume expansion during cycle. Herein, a combined structure and architecture modulation is proposed to tackle concurrently the two handicaps, via a facile and well-controlled solvothermal approach to synthesize NiMn₂O₄/NiCo₂O₄ mesocrystals with superlattice structure and hollow multi-porous architecture. It is demonstrated that the obtained NiCo_1.5Mn_0.5O₄ sample is made up of a new mixed-phase NiMn₂O₄/NiCo₂O₄ compound system, with a high charge capacity of 532.2 mAh g⁻¹ with 90.4% capacity retention after 100 cycles at a current density of 1 A g⁻¹. The enhanced electrochemical performance can be attributed to the synergistic effects of the superlattice structure and the hollow multi-porous architecture of the NiMn₂O₄/NiCo₂O₄ compound. The superlattice structure can improve ionic conductivity to enhance charge transport kinetics of the bulk material, while the hollow multi-porous architecture can provide enough void spaces to alleviate the architectural change during cycling, and shorten the lithium ions diffusion and electron-transportation distances.

Three-dimensional porous self-assembled chestnut-like nickel-cobalt oxide structure as an electrochemical sensor for sensitive detection of hydrazine in water samples

Three-dimensional NiCo₂O₄ is a kind of superior sensing material owing to its high electron transfer capability, large available surface area and numbers of active sites. In this work, NiCo₂O₄ of the three-dimensional chestnut-like structure were easily achieved through a one step hydrothermal process. Afterwards, the morphology and structure were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Based on the three-dimensional porous chestnut-like NiCo₂O₄, an electrochemical sensor for hydrazine (N₂H₄) detection is fabricated. This electrochemical platform can realize good selectivity, excellent stability, high sensitivity (∼2154.4 μA mM^-1 cm^-2), and low detection limit (0.3 μM), as well as a wide linear range from 1 μM to 1096 μM. The synergistic effect of nickel-cobalt in such mixed transition metal oxides which Co in Co₃O₄ is partially replaced by Ni are beneficial for enhancing sensing properties. This study proves that three-dimensional porous chestnut-like NiCo₂O₄ is electrochemically active for catalytic performance which is particular and promising material for good application in the practical detection of N₂H₄.

Facile preparation of monodisperse NiCo2O4 porous microcubes as a high capacity anode material for lithium ion batteries

Monodisperse NiCo₂O₄ porous microcubes were used as anode materials for lithium-ion batteries, and they exhibit outstanding rate capability and cycling stability.

Ordered Mesoporous NiCo2O4 Nanospheres as a Novel Electrocatalyst Platform for 1-Naphthol and 2-Naphthol Individual Sensing Application

The novel ordered mesoporous NiCo₂O₄ (meso-NiCo₂O₄) nanospheres were synthesized by the nanocasting strategy followed by a calcination process for 2-naphthol (2-NAP) and 1-naphthol (1-NAP) individual sensing application. The as-obtained meso-NiCo₂O₄ material possesses mesoporous structure in spinel crystalline type with a larger specific surface area than other structures. The meso-NiCo₂O₄-modified carbon paste electrode exhibited excellent electrocatalytic performance for NAP detection by amperometry measurement. The fabricated sensor of 2-NAP and 1-NAP has a wide linear detection range (0.02-300 and 0.02-20 μM) with high sensitivity (1.822 and 1.510 μA μM^-1 cm^-2) and low limit of detection (0.007 and 0.007 μM), respectively. In addition, the NAP sensors possess excellent reproducibility, stability, and selectivity.

Surfactant-assisted solvothermal synthesis of NiCo2O4 as an anode for lithium-ion batteries

The as-prepared NiCo₂O₄ nanoparticles through microemulsion-solvothermal growth and subsequent calcination in air exhibits excellent rate performance and cyclic stability.

Hierarchical flower-like NiCo2O4@TiO2hetero-nanosheets as anodes for lithium ion batteries

Flower-like NiCo₂O₄consisting of nanosheets are synthesized by hydrothermal technique and subsequently surface-modified with a TiO₂ultrathin layer by a hydrolysis process at low temperature.

Facile Synthesis of Core/Shell-like NiCo2O4-Decorated MWCNTs and its Excellent Electrocatalytic Activity for Methanol Oxidation

The design and development of an economic and highly active non-precious electrocatalyst for methanol electrooxidation is challenging due to expensiveness of the precursors as well as processes and non-ecofriendliness. In this study, a facile preparation of core-shell-like NiCo₂O₄ decorated MWCNTs based on a dry synthesis technique was proposed. The synthesized NiCo₂O₄/MWCNTs were characterized by infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and selected area energy dispersive spectrum. The bimetal oxide nanoparticles with an average size of 6 ± 2 nm were homogeneously distributed onto the surface of the MWCNTs to form a core-shell-like nanostructure. The NiCo₂O₄/MWCNTs exhibited excellent electrocatalytic activity for the oxidation of methanol in an alkaline solution. The NiCo₂O₄/MWCNTs exhibited remarkably higher current density of 327 mA/cm² and a lower onset potential of 0.128 V in 1.0 M KOH with as high as 5.0 M methanol. The impressive electrocatalytic activity of the NiCo₂O₄/MWCNTs is promising for development of direct methanol fuel cell based on non-Pt catalysts.

The design and synthesis of porous NiCo2O4 ellipsoids supported by flexile carbon nanotubes with enhanced lithium-storage properties for lithium-ion batteries

The as-prepared 3D porous NiCo₂O₄ ellipsoids supported by flexile carbon nanotubes nanowire arrays show high reversible capacity, excellent cycling stability, and good rate capability when used as an anode material for LIBs.

A bubble-template approach for assembling Ni–Co oxide hollow microspheres with an enhanced electrochemical performance as an anode for lithium ion batteries

A bubble-template approach was developed to assemble Ni–Co oxide hollow microspheres with an enhanced electrochemical performance as an anode for lithium ion batteries.

An overview of AB2O4- and A2BO4-structured negative electrodes for advanced Li-ion batteries

Energy-storage devices are state-of-the-art devices with many potential technical and domestic applications.