Mesoporous Co3O4 nanosheets-3D graphene networks hybrid materials for high-performance lithium ion batteries

Mesoporous multi-valence manganese oxides composite nanotubes boosting long-life lithium-ion batteries

Multi-component nano-oxide composite materials may present special synergistic effects as anode materials for lithium-ion batteries. Mesoporous β-MnO₂/Mn₃O₄ composite nanotubes are built here via controlling the deoxidation process of carbon-coating to induce a partial phase transition of high valence manganese dioxides. Compared to single β-MnO₂ nanotubes or Mn₃O₄@C nanotubes, the mesoporous β-MnO₂/Mn₃O₄@C composite nanotubes exhibit superior electrochemical properties. 679 mA h g^-1 of reversible specific capacity and 86% of capacity retention after 1000 cycles at 1 A g^-1 current density are obtained. The excellent performance is attributed to the unique multiple phase transitions regulation phenomena of manganese oxide occurring in the β-MnO₂/Mn₃O₄ composite material during the electrochemical processes, which significantly extends the cycle life of the β-MnO₂/Mn₃O₄ composite material.

Sodium insertion/extraction investigations into zinc ferrite nanospheres as a high performance anode material

Electrode materials with high fast charging and high capacity are urgently required for the realization of sodium-ion batteries (SIBs). In this work, zinc ferrite (ZnFe₂O₄) nanospheres have been prepared by the simple hydrothermal route and the structural analysis of ZnFe₂O₄ was evaluated by using X-ray diffraction. The morphology and microstructural characterizations are obtained using scanning electron microscopy and transmission electron microscopy. The results indicate that a single phase material was obtained with uniform sphere-like morphology and high crystallinity. The Brunauer–Emmett–Teller method was employed to determine the specific surface area of the ZnFe₂O₄ nanospheres which has been calculated to be 32 m² g⁻¹. The electrochemical results indicate that the composite possesses high sodium storage capability (478 mA h g⁻¹), and good cycling stability (284 mA h g⁻¹ at 100^th cycle) and rate capability (78 mA h g⁻¹ at 2 A g⁻¹). The high sodium storage performance of the ZnFe₂O₄ electrode is ascribed to the mesoporous nature of the ZnFe₂O₄ nanospheres. Further, sodium kinetics and the reaction mechanism in ZnFe₂O₄ nanospheres have been elucidated using electrochemical impedance spectroscopy, galvanostatic intermittent titration technique, ex situ TEM, and XAS. The acquired results indicate sluggish kinetics, reversibility of the material, and the stable structure of ZnFe₂O₄. Therefore, such a structure can be considered to be an attractive contender as a low cost anode for SIBs.

Electrode materials with high fast charging and high capacity are urgently required for the realization of sodium-ion batteries (SIBs).

Hydrothermal-template synthesis and electrochemical properties of Co3O4/nitrogen-doped hemisphere-porous graphene composites with 3D heterogeneous structure

Despite the high capacity of Co₃O₄ employed in lithium-ion battery anodes, the reduced conductivity and grievous volume change of Co₃O₄ during long cycling of insertion/extraction of lithium-ions remain a challenge. Herein, an optimized nanocomposite, Co₃O₄/nitrogen-doped hemisphere-porous graphene composite (Co₃O₄/N-HPGC), is synthesized by a facile hydrothermal-template approach with polystyrene (PS) microspheres as a template. The characterization results demonstrate that Co₃O₄ nanoparticles are densely anchored onto graphene layers, nitrogen elements are successfully introduced by carbamide and the nanocomposites maintain the hemispherical porous structure. As an anode material for lithium-ion batteries, the composite material not only maintains a relatively high lithium storage capacity (the first discharge specific capacity can reach 2696 mA h g⁻¹), but also shows significantly improved rate performance (1188 mA h g⁻¹ at 0.1 A g⁻¹, 344 mA h g⁻¹ at 5 A g⁻¹) and enhanced cycling stability (683 mA h g⁻¹ after 500 cycles at 1 A g⁻¹). The enhanced electrochemical properties of Co₃O₄/N-HPGC nanocomposites can be ascribed to the synergistic effects of Co₃O₄ nanoparticles, novel hierarchical structure with hemisphere-pores and nitrogen-containing functional groups of the nanomaterials. Therefore, the developed strategy can be extended as a universal and scalable approach for integrating various metal oxides into graphene-based materials for energy storage and conversion applications.

The Co₃O₄/N-HPGC nanocomposites synthesized by a hydrothermal-template approach with polystyrene microspheres as the template possess excellent electrochemical performance.

Nitrogen-Doped Porous Co3O4/Graphene Nanocomposite for Advanced Lithium-Ion Batteries

A novel approach is developed to synthesize a nitrogen-doped porous Co₃O₄/anthracite-derived graphene (Co₃O₄/AG) nanocomposite through a combined self-assembly and heat treatment process using resource-rich anthracite as a carbonaceous precursor. The nanocomposite contains uniformly distributed Co₃O₄ nanoparticles with a size smaller than 8 nm on the surface of porous graphene, and exhibits a specific surface area (120 m²·g⁻¹), well-developed mesopores distributed at 3~10 nm, and a high level of nitrogen doping (5.4 at. %). These unique microstructure features of the nanocomposite can offer extra active sites and efficient pathways during the electrochemical reaction, which are conducive to improvement of the electrochemical performance for the anode material. The Co₃O₄/AG electrode possesses a high reversible capacity of 845 mAh·g⁻¹ and an excellent rate capacity of 587 mAh·g⁻¹. Furthermore, a good cyclic stability of 510 mAh·g⁻¹ after 100 cycles at 500 mA·g⁻¹ is maintained. Therefore, this work could provide an economical and effective route for the large-scale application of a Co₃O₄/AG nanocomposite as an excellent anode material in lithium-ion batteries.

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.

Metal-Oleate Complex-Derived Bimetallic Oxides Nanoparticles Encapsulated in 3D Graphene Networks as Anodes for Efficient Lithium Storage with Pseudocapacitance

In this manuscript, we have demonstrated the delicate design and synthesis of bimetallic oxides nanoparticles derived from metal-oleate complex embedded in 3D graphene networks (MnO/CoMn₂O₄ ⊂ GN), as an anode material for lithium ion batteries. The novel synthesis of the MnO/CoMn₂O₄ ⊂ GN consists of thermal decomposition of metal-oleate complex containing cobalt and manganese metals and oleate ligand, forming bimetallic oxides nanoparticles, followed by a self-assembly route with reduced graphene oxides. The MnO/CoMn₂O₄ ⊂ GN composite, with a unique architecture of bimetallic oxides nanoparticles encapsulated in 3D graphene networks, rationally integrates several benefits including shortening the diffusion path of Li⁺ ions, improving electrical conductivity and mitigating volume variation during cycling. Studies show that the electrochemical reaction processes of MnO/CoMn₂O₄ ⊂ GN electrodes are dominated by the pseudocapacitive behavior, leading to fast Li⁺ charge/discharge reactions. As a result, the MnO/CoMn₂O₄ ⊂ GN manifests high initial specific capacity, stable cycling performance, and excellent rate capability.

Sintering Temperature Induced Evolution of Microstructures and Enhanced Electrochemical Performances: Sol-Gel Derived LiFe(MoO4)2 Microcrystals as a Promising Anode Material for Lithium-Ion Batteries

A facile sol-gel process was used for synthesis of LiFe(MoO₄)₂ microcrystals. The effects of sintering temperature on the microstructures and electrochemical performances of the as-synthesized samples were systematically investigated through XRD, SEM and electrochemical performance characterization. When sintered at 650°C, the obtained LiFe(MoO₄)₂ microcrystals show regular shape and uniform size distribution with mean size of 1–2 μm. At the lower temperature (600°C), the obtained LiFe(MoO₄)₂ microcrystals possess relative inferior crystallinity, irregular morphology and vague grain boundary. At the higher temperatures (680 and 700°C), the obtained LiFe(MoO₄)₂ microcrystals are larger and thicker particles. The electrochemical results demonstrate that the optimized LiFe(MoO₄)₂ microcrystals (650°C) can deliver a high discharge specific capacity of 925 mAh g⁻¹ even at a current rate of 1 C (1,050 mA g⁻¹) after 500 cycles. Our work can provide a good guidance for the controllable synthesis of other transition metal NASICON-type electrode materials.

Simultaneous modulation of surface composition, oxygen vacancies and assembly in hierarchical Co3O4 mesoporous nanostructures for lithium storage and electrocatalytic oxygen evolution

We developed a facile solution reductive method to simultaneously tune the surface composition, oxygen vacancies and three dimensional assembly in Co₃O₄ hierarchical nanostructures. The controllable surface composition, oxygen vacancies together with hierarchical micro/nanoarchitectures resulted in superior electrochemical properties when used as the anode materials for lithium-ion batteries and as an electrocatalyst for the oxygen evolution reaction. The excellent electrochemical performance is attributed to the synergistic effects of novel hierarchical morphology, crystal structure of the active materials, the improvement of intrinsic conductivity and inner surface area induced by the oxygen vacancies. The present strategy not only provides a facile method to assemble novel hierarchical architectures, but also paves a way to control surface structures (chemical composition and crystal defects) in other transition-metal compounds, and thus will hold great promise in the fields of energy storage and conversion.

Two-dimensional porous Co3O4nanosheets for high-performance lithium ion batteries

2D porous Co₃O₄nanosheets are synthesizedviaa self-sacrificing template method. When applied as an anode for LIBs, the as-obtained 2D porous Co₃O₄nanosheets exhibit a high discharge specific capacity, good cycling stability, and high rate capability.

Hierarchically porous CoNiO2nanosheet array films with superior sodium storage performance

The hierarchically porous CoNiO₂nanosheet array film preparedviaa low-temperature solvothermal method manifests superior sodium storage performance.

3D Hierarchical Co-Al Layered Double Hydroxides with Long-Term Stabilities and High Rate Performances in Supercapacitors

Three-dimensional (3D) flower-like Co-Al layered double hydroxide (Co-Al-LDH) architectures composed of atomically thin nanosheets were successfully synthesized via a hydrothermal method in a mixed solvent of water and butyl alcohol. Owing to the unique hierarchical structure and modification by butyl alcohol, the electrochemical stability and the charge/mass transport of the Co-Al-LDHs was improved. When used in supercapacitors, the obtained Co-Al-LDHs deliver a high specific capacitance of 838 F g^-1 at a current density of 1 A g^-1 and excellent rate performance (753 F g^-1 at 30 A g^-1 and 677 F g^-1 at 100 A g^-1), as well as excellent cycling stability with 95% retention of the initial capacitance even after 20,000 cycles at a current density of 5 A g^-1. This work provides a promising alternative strategy to enhance the electrochemical properties of supercapacitors.

Computational Analysis of the Optical and Charge Transport Properties of Ultrasonic Spray Pyrolysis-Grown Zinc Oxide/Graphene Hybrid Structures

We demonstrate a systematic computational analysis of the measured optical and charge transport properties of the spray pyrolysis-grown ZnO nanostructures, i.e. nanosphere clusters (NSCs), nanorods (NRs) and nanowires (NWs) for the first time. The calculated absorbance spectra based on the time-dependent density functional theory (TD-DFT) shows very close similarity with the measured behaviours under UV light. The atomic models and energy level diagrams for the grown nanostructures were developed and discussed to explain the structural defects and band gap. The induced stresses in the lattices of ZnO NSCs that formed during the pyrolysis process seem to cause the narrowing of the gap between the energy levels. ZnO NWs and NRs show homogeneous distribution of the LUMO and HOMO orbitals all over the entire heterostructure. Such distribution contributes to the reduction of the band gap down to 2.8 eV, which has been confirmed to be in a good agreement with the experimental results. ZnO NWs and NRs exhibited better emission behaviours under the UV excitation as compared to ZnO NSCs and thin film as their visible range emissions are strongly quenched. Based on the electrochemical impedance measurement, the electrical models and electrostatic potential maps were developed to calculate the electron lifetime and to explain the mobility or diffusion behaviours in the grown nanostructure, respectively.

Interaction Induced High Catalytic Activities of CoO Nanoparticles Grown on Nitrogen-Doped Hollow Graphene Microspheres for Oxygen Reduction and Evolution Reactions

Nitrogen doped graphene hollow microspheres (NGHSs) have been used as the supports for the growth of the CoO nanoparticles. The nitrogen doped structure favors the nucleation and growth of the CoO nanoparticles and the CoO nanoparticles are mostly anchored on the quaternary nitrogen doped sites of the NGHSs with good monodispersity since the higher electron density of the quaternary nitrogen favors the nucleation and growth of the CoO nanoparticles through its coordination and electrostatic interactions with the Co(2+) ions. The resulting NGHSs supported CoO nanoparticles (CoO/NGHSs) are highly active for the oxygen reduction reaction (ORR) with activity and stability higher than the Pt/C and for the oxygen evolution reaction (OER) with activity and stability comparable to the most efficient catalysts reported to date. This indicates that the CoO/NGHSs could be used as efficient bi-functional catalysts for ORR and OER. Systematic analysis shows that the superior catalytic activities of the CoO/NGHSs for ORR and OER mainly originate from the nitrogen doped structure of the NGHSs, the small size of the CoO nanoparticles, the higher specific and electroactive surface area of the CoO/NGHSs, the good electric conductivity of the CoO/NGHSs, the strong interaction between the CoO nanoparticles and the NGHSs, etc.

Nanoparticle Decorated Ultrathin Porous Nanosheets as Hierarchical Co3O4 Nanostructures for Lithium Ion Battery Anode Materials

We report a facile synthesis of a novel cobalt oxide (Co₃O₄) hierarchical nanostructure, in which crystalline core-amorphous shell Co₃O₄ nanoparticles with a bimodal size distribution are uniformly dispersed on ultrathin Co₃O₄ nanosheets. When tested as anode materials for lithium ion batteries, the as-prepared Co₃O₄ hierarchical electrodes delivered high lithium storage properties comparing to the other Co₃O₄ nanostructures, including a high reversible capacity of 1053.1 mAhg⁻¹ after 50 cycles at a current density of 0.2 C (1 C = 890 mAg⁻¹), good cycling stability and rate capability.

Three-dimensional macro-structures of two-dimensional nanomaterials

This review summarizes the recent progress and efforts in the synthesis, structure, properties, and applications of three-dimensional macro-structures of two-dimensional nanomaterials.

Facile shape control of nano-coaxial Co3O4/TiO2 arrays and the effect of the microstructure on lithium storage capability

Co₃O₄/TiO₂ nanohybrids fabricated via a layer-by-layer procedure have exhibited excellent electrochemical performance.

Engineering the surface of rutile TiO2 nanoparticles with quantum pits towards excellent lithium storage

Unique rutile TiO₂ nanoparticles with quantum pits have been successfully synthesized by a facile solution and subsequent thermal annealing method. The resultant rutile TiO₂ nanoparticles exhibit excellent lithium storage properties.

One-dimensional porous nanofibers of Co3O4 on the carbon matrix from human hair with superior lithium ion storage performance

One-dimensional (1D) hierarchical porous nanofibers of Co3O4 possessing of (220) facets on the carbon matrix from human hair (H2@Co3O4) with 20-30 nm in width and 3-5 μm in length are prepared by a facile solvothermal and calcination approach. The well crystallized small Co3O4 particles with the diameter of about 8-12 nm were closely aggregated together in the nanofibers. Electrochemical analyses show that the first discharge capacity of H2@Co3O4 electrode is 1368 mAh g(-1) at the current density of 0.1 A g(-1) based on the total mass of composite. A high reversible capacity of 916 mAh g (-1) was obtained over 100 cycles at 0.1 A g(-1), presenting a good cycling stability. When cycled at a high current density of 1 and 2 A g(-1), the specific capacity of 659 and 573 mAh g(-1) could be still achieved, respectively, indicating a superior power capability.

Recent advances in graphene and its metal-oxide hybrid nanostructures for lithium-ion batteries

Today, one of the major challenges is to provide green and powerful energy sources for a cleaner environment. Rechargeable lithium-ion batteries (LIBs) are promising candidates for energy storage devices, and have attracted considerable attention due to their high energy density, rapid response, and relatively low self-discharge rate. The performance of LIBs greatly depends on the electrode materials; therefore, attention has been focused on designing a variety of electrode materials. Graphene is a two-dimensional carbon nanostructure, which has a high specific surface area and high electrical conductivity. Thus, various studies have been performed to design graphene-based electrode materials by exploiting these properties. Metal-oxide nanoparticles anchored on graphene surfaces in a hybrid form have been used to increase the efficiency of electrode materials. This review highlights the recent progress in graphene and graphene-based metal-oxide hybrids for use as electrode materials in LIBs. In particular, emphasis has been placed on the synthesis methods, structural properties, and synergetic effects of metal-oxide/graphene hybrids towards producing enhanced electrochemical response. The use of hybrid materials has shown significant improvement in the performance of electrodes.

Well-constructed single-layer molybdenum disulfide nanorose cross-linked by three dimensional-reduced graphene oxide network for superior water splitting and lithium storage property

A facile one-step solution reaction route for growth of novel MoS2 nanorose cross-linked by 3D rGO network, in which the MoS2 nanorose is constructed by single-layered or few-layered MoS2 nanosheets, is presented. Due to the 3D assembled hierarchical architecture of the ultrathin MoS2 nanosheets and the interconnection of 3D rGO network, as well as the synergetic effects of MoS2 and rGO, the as-prepared MoS2-NR/rGO nanohybrids delivered high specific capacity, excellent cycling and good rate performance when evaluated as an anode material for lithium-ion batteries. Moreover, the nanohybrids also show excellent hydrogen-evolution catalytic activity and durability in an acidic medium, which is superior to MoS2 nanorose and their nanoparticles counterparts.

Cobalt oxide-carbon nanosheet nanoarchitecture as an anode for high-performance lithium-ion battery

To improve the electrochemical performance of cobalt oxide owing to its inherent poor electrical conductivity and large volume expansion/contraction, Co3O4-carbon nanosheet hybrid nanoarchitectures were synthesized by a facile and scalable chemical process. However, it is still a challenge to control the size of Co3O4 particles down to ∼5 nm. Herein, we created nanosized cobalt oxide anchored 3D arrays of carbon nanosheets by the control of calcination condition. The uniformly dispersed Co3O4 nanocrystals on carbon nanosheets held a diameter down to ∼5 nm. When tested as anode materials for lithium-ion batteries, high lithium storage over 1200 mAh g(-1) is achieved, whereas high rate capability with capacity of about 390 mAh g(-1) at 10 A g(-1) is maintained through nanoscale diffusion distances and interconnected porous structure. After 500 cycles, the cobalt oxide-carbon nansheets hybrid display a reversible capacity of about 970 mAh g(-1) at 1 A g(-1). The synergistic effect between nanosized cobalt oxide and sheetlike interconnected carbon nanosheets lead to the greatly improved specific capacity and the initial Coulombic efficiency of the hybrids.

Green synthesis of 3D SnO2/graphene aerogels and their application in lithium-ion batteries

3D SnO₂/GAs were constructed by a simple, facile and environmental friendly process, and show excellent performance when used as anode material in lithium ion batteries.

A novel shuttle-like Fe3O4–Co3O4 self-assembling architecture with highly reversible lithium storage

An unprecedented shuttle-like Fe₃O₄–Co₃O₄ self-assembling architecture is obtained through a facile hydrothermal method. Obviously, the electrochemical performance of the obtained composite is large enhanced in comparison with that of pristine Co₃O₄.

Ultra-small Co3O4 nanoparticles–reduced graphene oxide nanocomposite as superior anodes for lithium-ion batteries

A facile solution-based method was reported to prepare ultra-small Co₃O₄ nanoparticles–reduced graphene oxide (Co₃O₄–RGO) nanocomposite as anode material for lithium-ion batteries. This Co₃O₄–RGO nanocomposite showed good electrochemical performance.