Three-dimensional aligned mesoporous carbon nanotubes filled with Co3O4 nanoparticles for Li-ion battery anode applications

Co3 O4 Polyhedron@MnO2 Nanotube Composite as Anode for High-Performance Lithium-Ion Batteries

In this work, a novel lollipop nanostructure of Co₃ O₄ @MnO₂ composite is prepared as anode material in lithium-ion batteries (LIBs). Cobalt metal-organic framework (ZIF-67) is grown on the open end of MnO₂ nanotubes via a self-assembly process. The obtained ZIF-67@MnO₂ is then converted to Co₃ O₄ @MnO₂ by a simple annealing treatment in air. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction characterizations indicate that the prepared Co₃ O₄ @MnO₂ takes a lollipop nanostructure with a stick of ≈100 nm in diameter, consisting of MnO₂ nanotube, and a head part of ≈1 µm, consisting of Co₃ O₄ nanoparticles. The charge-discharge tests illustrate that this unique novel configuration endows the resulting Co₃ O₄ @MnO₂ with excellent electrochemical performances, delivering a capacity of 1080 mAh g^-1 at 300 mA g^-1 after 160 cycles, and 696 mAh g^-1 at 1 A g^-1 after 210 cycles, compared with 404 mAh g^-1 and 590 for pure Co₃ O₄ polyhedrons and pure MnO₂ nanotubes at 300 mA g^-1 after 160 cycles, respectively. The lollipop configuration consisting of porous Co₃ O₄ polyhedron and MnO₂ nanotube shows excellent structural stability and facilitates lithium insertion/extraction, leading to excellent cyclic stability and rate capacity of Co₃ O₄ @MnO₂ -based LIBs.

Recent Progress of Electrochemical Energy Devices: Metal Oxide–Carbon Nanocomposites as Materials for Next-Generation Chemical Storage for Renewable Energy

With the importance of sustainable energy, resources, and environmental issues, interest in metal oxides increased significantly during the past several years owing to their high theoretical capacity and promising use as electrode materials for electrochemical energy devices. However, the low electrical conductivity of metal oxides and their structural instability during cycling can degrade the battery performance. To solve this problem, studies on carbon/metal-oxide composites were carried out. In this review, we comprehensively discuss the characteristics (chemical, physical, electrical, and structural properties) of such composites by categorizing the structure of carbon in different dimensions and discuss their application toward electrochemical energy devices. In particular, one-, two-, and three-dimensional (1D, 2D, and 3D) carbon bring about numerous advantages to a carbon/metal-oxide composite owing to the unique characteristics of each dimension.

Alcohol Solvent Effects in the Synthesis of Co3O4 Metal-Oxide Nanoparticles: Disproof of a Surface-Ligand Thermodynamic Effect en Route to Alternative Kinetic and Thermodynamic Explanations

The synthesis of Co₃O₄ core nanoparticles from cobalt acetate is explored in alcohol solvents plus limited water using O₂ as oxidant and NH₄OH as the base, all in comparison to controls in water alone employing the otherwise identical synthetic procedure. Syntheses in EtOH or t-BuOH cosolvents with limited water yield phase-pure and size-controlled (3 ± 1 nm) Co₃O₄-core nanoparticles. In marked contrast, the synthesis in water alone yields mixed phases of Co₃O₄ and β-Co(OH)₂ with a very large particle-size range (14-400 nm). Importantly, acidic reductive digestion of the Co₃O₄ particles followed by ¹H NMR on the resultant solution yields no detectable EtOH in nanoparticles prepared in EtOH, nor any detectable t-BuOH in nanoparticles prepared in t-BuOH (∼5% detection limits for each alcohol), despite the dramatic effect of each alcohol cosolvent on the resultant cobalt-oxide product. Instead, in both cases HOAc is detected and quantified, indicative of OAc^- as a surface ligand-and not EtO^- or t-BuO^- as the surface ligand. The resultant ROH cosolvent-derived particles were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, plus elemental analysis to arrive at an approximate, average molecular formula in the case of the particles prepared in EtOH, {[Co₃O₄(C₂H₃O₂)]^-[(NH₄⁺)_0.3(H⁺_0.7)]⁺·(H₂O)}_∼216. The key finding is that, because EtOH and t-BuOH have a substantial effect on the phase- and size-dispersion of the cobalt-oxide nanoparticle product, yet the intact alcohol does not show up in the final Co₃O₄ nanoparticle product, the effect of these alcohols cannot be a surface-ligand thermodynamic effect on the net nanoparticle formation reaction. A careful search of the literature provided scattered, but consistent, literature in which anions or other additives have large effects on metal-oxide nanoparticle formation reactions, yet also do not show up in the nanoparticle products-that is, where the observed effects are again not due to binding by that anion or other additive in a surface-ligand thermodynamic effect on the overall reaction. Alternative hypotheses are provided as to the origin of ROH solvent effects on metal-oxide nanoparticles.

Rational Design of 1-D Co3O4 Nanofibers@Low content Graphene Composite Anode for High Performance Li-Ion Batteries

Cobalt oxide that has high energy density, is the next-generation candidate as the anode material for LIBs. However, the practical use of Co₃O₄ as anode material has been hindered by limitations, especially, low electrical conductivity and pulverization from large volume change upon cycling. These features lead to hindrance to its electrochemical properties for lithium-ion batteries. To improve electrochemical properties, we synthesized one-dimensional (1-D) Co₃O₄ nanofibers (NFs) overed with reduced graphene oxide (rGO) sheets by electrostatic self-assembly (Co₃O₄ NFs@rGO). The flexible graphene oxide sheets not only prevent volume changes of active materials upon cycling as a clamping layer but also provide efficient electrical pathways by three-dimensional (3-D) network architecture. When applied as an anode for LIBs, the Co₃O₄ NFs@rGO exhibits superior electrochemical performance: (i) high reversible capacity (615 mAh g⁻¹ and 92% capacity retention after 400 cycles at 4.0 A g⁻¹) and (ii) excellent rate capability. Herein, we highlighted that the enhanced conversion reaction of the Co₃O₄ NFs@rGO is attributed to effective combination of 1-D nanostructure and low content of rGO (~3.5 wt%) in hybrid composite.

Graphene-Embedded Co3O4 Rose-Spheres for Enhanced Performance in Lithium Ion Batteries

Co₃O₄ has been widely studied as a promising candidate as an anode material for lithium ion batteries. However, the huge volume change and structural strain associated with the Li⁺ insertion and extraction process leads to the pulverization and deterioration of the electrode, resulting in a poor performance in lithium ion batteries. In this paper, Co₃O₄ rose-spheres obtained via hydrothermal technique are successfully embedded in graphene through an electrostatic self-assembly process. Graphene-embedded Co₃O₄ rose-spheres (G-Co₃O₄) show a high reversible capacity, a good cyclic performance, and an excellent rate capability, e.g., a stable capacity of 1110.8 mAh g^-1 at 90 mA g^-1 (0.1 C), and a reversible capacity of 462.3 mAh g^-1 at 1800 mA g^-1 (2 C), benefitted from the novel architecture of graphene-embedded Co₃O₄ rose-spheres. This work has demonstrated a feasible strategy to improve the performance of Co₃O₄ for lithium-ion battery application.

Rectangular Co3O4 with micro-/nanoarchitectures: charge-driven PDDA-assisted synthesis and excellent lithium storage performance

The charge-driven hydrothermal strategy is successfully applied to the synthesis of two dimensional (2D) rectangular Co₃O₄ with micro-/nanoarchitectures, which demonstrate excellent lithium storage performance for batteries.

Designing Heterogeneous 1D Nanostructure Arrays Based on AAO Templates for Energy Applications

In order to fulfill the multiple requirements for energy production, storage, and utilization in the future, the conventional planar configuration of current energy conversion/storage devices has to be reformed, since technological evolution has promoted the efficiency of the corresponding devices to be close to the theoretical values. One promising strategy is to construct multifunctional 1D nanostructure arrays to replace their planar counterparts for device fabrication, ascribing to the significant superiorities of such 1D nanostructure arrays. In the last three decades, technologies based on anodic aluminium oxide (AAO) templates have turned out to be valuable meaning for the realization of 1D nanostructures and have attracted tremendous interest. In this review, recent progress in energy-related devices equipped with heterogeneous 1D nanostructure arrays that fabricated through the assistance of AAO templates is highlighted. Particular emphasis is given on how to develop efficient devices via optimizing the componential and morphological parameters of the 1D nanostructure arrays. Finally, aspects relevant to the further improvement of device performance are discussed.

Hollow Ball-in-Ball CoxFe3-xO4 Nanostructures: High-Performance Anode Materials for Lithium-Ion Battery

The intrinsic electronic conductivity can be improved by doping efficiently. CoxFe3-xO4 nanostructures have been synthesized for the first time to improve the conductivity of lithium battery electrode. The solid solution CoxFe3--xO4 were characterized by X-ray diffraction pattern (XRD), Raman spectrum, scanning electron microscopy (SEM), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results show that the doping enlarge the lattice spacing but the structure of Co3O4 is stable in the Li-ion intercalation/deintercalation process. The AC impedance spectrum reveals the conductivity is well improved. In addition, the solid solution CoxFe3-xO4 exhibit excellent electrochemical characteristics. The electrodes with 20% molar ratio of Fe ions own a reversible capacity of 650.2 mA h g(-1) at a current density of 1 A g(-1) after 100 cycles.

Yolk bishell Mn(x)Co(1-x)Fe2O4 hollow microspheres and their embedded form in carbon for highly reversible lithium storage

The yolk-shell hollow structure of transition metal oxides has many applications in lithium-ion batteries and catalysis. However, it is still a big challenge to fabricate uniform hollow microspheres with the yolk bishell structure for mixed transition metal oxides and their supported or embedded forms in carbon microspheres with superior lithium storage properties. Here we report a new approach to the synthesis of manganese cobalt iron oxides/carbon (MnxCo1-xFe2O4 (0 ≤ x ≤ 1)) microspheres through carbonization of Mn(2+)Co(2+)Fe(3+)/carbonaceous microspheres in N2, which can be directly applied as high-performance anodes with a long cycle life for lithium storage. Furthermore, uniform hollow microspheres with a MnxCo1-xFe2O4 yolk bishell structure are obtained by annealing the above MnxCo1-xFe2O4/carbon microspheres in air. As demonstrated, these anodes exhibited a high reversible capacity of 498.3 mAh g(-1) even after 500 cycles for Mn0.5Co0.5Fe2O4/carbon microspheres and 774.6 mAh g(-1) over 100 cycles for Mn0.5Co0.5Fe2O4 yolk bishell hollow microspheres at the current density of 200 mA g(-1). The present strategy not only develops a high-performance anode material with long cycle life for lithium-ion batteries but also demonstrates a novel and feasible technique for designed synthesis of transition metal oxides yolk bishell hollow microspheres with various applications.

In situ and ex situ carbon coated Zn2SnO4 nanoparticles as promising negative electrodes for Li-ion batteries

Zinc stannate, Zn₂SnO₄ nanoparticles are successfully synthesized by a facile hydrothermal method.

Solution synthesis of metal oxides for electrochemical energy storage applications

This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.