Flexible free-standing Fe2O3/graphene/carbon nanotubes hybrid films as anode materials for high performance lithium-ion batteries

Microtexture analysis of copper-doped iron oxide thin films prepared by air pneumatic spray

The stereometric and fractal concepts are crucial tools to analyze, to verify, to report 3-D microtexture of thin film surfaces on the nanometer scale, and thereby to generate useful topographic characteristics for better understanding and steering them toward further improvements and rational use in modern applications. At first, the present work aimed to prepare hematite α-Fe₂ O₃ thin films with (0, 2, 4, 6 and 8 wt%) of Cu doping by using the air pneumatic spray method. Subsequently, the obtained pure α-Fe₂ O₃ and Cu-doped α-Fe₂ O₃ thin films were characterized by XRD device, which determines their polycrystalline nature with the rhombohedral hematite structure. Analysis by UV-vis absorption showed that the transmittance of the thin films is extinct in the wavelength from approximately 500 nm to 800 nm, revealing that the films have good optical absorbance in the visible region. The obtained bandgap values varied between 2.23 and 2.21 eV. At second stage, the stereometric and fractal analysis are applied on 3-D image data of pure α- Fe₂ O₃ and Cu-doped α- Fe₂ O₃ thin films, which in prior generated using AFM device. Accordingly, the obtained statistical parameters such as surface roughness, density distribution of peaks, and depths, etc. were used to understand the influence of Cu doping on the 3D microtexture of pure α- Fe₂ O₃ and Cu-doped α- Fe₂ O₃ thin film surfaces. This article is protected by copyright. All rights reserved.

Reduced graphene oxide (rGO) supported and p yrolytic carbon (PC) coated γ-Fe2O3/PC-rGO composite anode material with enhanced Li-storage performance

As a high-capacity anode material for lithium ion batteries, γ-Fe 2 O 3 is a promising alternative to conventional graphite among multifarious transition metal oxides owing to its high theoretical specific capacity (1007 mAh g -1 ), abundant reserves, good safety and low cost. However, improving the electrical conductivity and overcoming the morphological damage caused by the severe volume expansion during cycling are still the tricky problems to be solved. Herein, a three-dimensional heterostructure composite (γ-Fe 2 O 3 /PC-rGO 60 ) was prepared by a facile solvothermal reaction followed by heat treatment in inert atmosphere. This composite material exhibits a reversible charge specific capacity of 1035 mAh g -1 at the current density of 0.1 A g -1 . After 100 cycles at 0.2 A g -1 , the capacity is increased from 966.2 to 1091.1 mAhg -1 . Even cycled for 200 cycles at 1 A g -1 , the capacity is only decreased from 751.4 to 670.6 mAh g -1 , giving capacity retention of 89.3%. The rGO network supported flexible composite architecture is beneficial for accommodating the volume expansion of the γ-Fe 2 O 3 active material during the lithiation/delithiation process. Besides, the conductive rGO network and the in-situ formed pyrolytic carbon (PC) can provide a smooth electron transmission path and a favorable lithium ion transport channel.

Iron oxides/graphene hybrid structures - Preparation, modification, and application as fillers of polymer composites

The current status of knowledge regarding magnetic hybrid structures based on graphene or carbon nanotubes with various forms of iron oxides is reviewed. The paper starts with a summary of the preparation and properties of iron oxide nanoparticles, both untreated and coated with silica or polymer layers. In the next section, organic-inorganic hybrid materials obtained as a result of a combination of graphene or carbon nanotubes and iron chemical compounds are characterized and discussed. These hybrids constitute an increasing percentage of all consumable high performance biomedical, electronic, and energy materials due to their valuable properties and low production costs. The potential of their application as components of materials used in corrosion protection, catalysis, spintronics, biomedicine, photoelectrochemical water splitting and groundwater remediation, as well as magnetic nanoparticles in polymer matrices, are also presented. The last part of this review article is focused on reporting the most recent developments in design and the understanding of the properties of polymer composites reinforced with nanometer-sized iron oxide/graphene and iron oxide/carbon nanotubes hybrid fillers. The discussion presents comparative analysis of the magnetic, electromagnetic shielding, electrical, thermal, and mechanical properties of polymer composites with various iron oxide/graphene structures. It is shown that the introduction of hybrid filler nanoparticles into polymer matrices enhances both the macro- and microproperties of final composites as a result of synergistic effects of individual components and the simultaneous formation of an oriented filler network in the polymer. The reinforcing effect is related to the structure and geometry of hybrid nanoparticles applied as a filler, the interactions between the filler particles, their concentration in a composite, and the method of composite processing.

Preparation and microwave absorption performance of a flexible Fe3O4/nanocarbon hybrid buckypaper and its application in composite materials

Graphene oxide (GO) and carbon nanotubes are promising microwave-absorbing materials. Herein, ferroferric oxide (Fe₃O₄)/multiwall carbon nanotube (MWCNT) and Fe₃O₄/GO hybrid buckypapers with excellent flexibility and manoeuvrability were coated on the surface of an epoxy substrate to fabricate microwave-absorbing composites. Fe₃O₄/GO buckypapers show a unique layered structure that differs from the complex network structure of Fe₃O₄/MWCNT buckypapers. Therefore, the Fe₃O₄/GO buckypapers exhibit lower tensile strength and toughness than the Fe₃O₄/MWCNT buckypapers, and the minimum electromagnetic reflection loss of Fe₃O₄/GO buckypapers is higher than that of Fe₃O₄/MWCNT buckypapers. Further, Fe₃O₄/GO buckypapers have a wider effective absorption-frequency band than Fe₃O₄/MWCNT buckypapers at 2.0–18.0 GHz. Although the mechanical properties of epoxy resin composites coated with Fe₃O₄/MWCNT or Fe₃O₄/GO buckypapers show a slight deterioration in comparison with those of the epoxy resin substrate, both buckypapers exhibit improved microwave-absorption performance compared with the epoxy resin substrate.

Flexible nanofilms are used as wave absorbing coatings for fiber/epoxy matrix to prepare lightweight wave-absorbing composites.

FeO x -Based Materials for Electrochemical Energy Storage

Iron oxides (FeO x ), such as Fe2O3 and Fe3O4 materials, have attracted much attention because of their rich abundance, low cost, and environmental friendliness. However, FeO x , which is similar to most transition metal oxides, possesses a poor rate capability and cycling life. Thus, FeO x -based materials consisting of FeO x , carbon, and metal-based materials have been widely explored. This article mainly discusses FeO x -based materials (Fe2O3 and Fe3O4) for electrochemical energy storage applications, including supercapacitors and rechargeable batteries (e.g., lithium-ion batteries and sodium-ion batteries). Furthermore, future perspectives and challenges of FeO x -based materials for electrochemical energy storage are briefly discussed.

Rational Design of Three-Dimensional Graphene Encapsulated with Hollow FeP@Carbon Nanocomposite as Outstanding Anode Material for Lithium Ion and Sodium Ion Batteries

Transition metal phosphides have been extensively investigated owing to their high theoretical capacities and relatively low intercalation potentials vs Li/Li⁺, but their practical applications have been hindered by low electrical conductivity and dramatic volume variation during cycling. In this work, an interesting strategy for the rational design of graphene (GR) encapsulated with a hollow FeP@carbon nanocomposite (H-FeP@C@GR) via a combination of a hydrothermal route, a carbon-coating process, phosphidation treatment, and carbothermic reaction is reported. The hollow FeP (H-FeP) nanospheres shelled with thin carbon layers are wonderfully incorporated into the GR matrix, interconnecting to form a three-dimensional (3D) hierarchical architecture. Such a design offers distinct advantages for FeP-based anode materials for both lithium ion batteries (LIBs) and sodium ion batteries (SIBs). For example, the 3D omnibearing conductive networks from the GR skeleton and outer coating carbon can provide an open freeway for electron/ion transport, promoting the electrode reaction kinetics. In addition, the wrapping of an H-FeP nanosphere in a thin carbon layer enables the formation of a solid electrolyte interphase (SEI) on the carbon layer surface instead of on the individual H-FeP surface, preventing the continual re-forming of the SEI. When used as anode materials for LIBs and SIBs, H-FeP@C@GR exhibited excellent electrochemistry performances.

Stabilizing the Nanostructure of SnO2 Anodes by Transition Metals: A Route to Achieve High Initial Coulombic Efficiency and Stable Capacities for Lithium Storage

To dramatically stabilize the nanostructure of Sn and achieve ultrahigh reversibility of conversion reactions in lithiated SnO₂ , a series of SnO₂ -transition metal-graphite ternary nanocomposites are produced by ball milling, demonstrating high initial Coulombic efficiencies up to 88.6%, high reversible capacity (>700 mAh g^-1 at 2 A g^-1 ), and ultralong cycling life (90.3% of capacity retention after 1300 cycles).

Carbon nanotube-wrapped Fe2O3 anode with improved performance for lithium-ion batteries

Metall oxides have been proven to be potential candidates for the anode material of lithium-ion batteries (LIBs) because they offer high theoretical capacities, and are environmentally friendly and widely available. However, the low electronic conductivity and severe irreversible lithium storage have hindered a practical application. Herein, we employed ethanolamine as precursor to prepare Fe₂O₃/COOH-MWCNT composites through a simple hydrothermal synthesis. When these composites were used as electrode material in lithium-ion batteries, a reversible capacity of 711.2 mAh·g^-1 at a current density of 500 mA·g^-1 after 400 cycles was obtained. The result indicated that Fe₂O₃/COOH-MWCNT composite is a potential anode material for lithium-ion batteries.

Flexible, Freestanding, and Binder-free SnO(x)-ZnO/Carbon Nanofiber Composites for Lithium Ion Battery Anodes

Here, we demonstrate the production of electrospun SnO(x)-ZnO polyacrylonitrile (PAN) nanofibers (NFs) that are flexible, freestanding, and binder-free. This NF fabric is flexible and thus can be readily tailored into a coin for further cell fabrication. These properties allow volume expansion of the oxide materials and provide shortened diffusion pathways for Li ions than those achieved using the nanoparticle approach. Amorphous SnO(x)-ZnO particles were uniformly dispersed in the carbon NF (CNF). The SnO(x)-ZnO CNFs with a Sn:Zn ratio of 3:1 exhibited a superior reversible capacity of 963 mA·h·g(-1) after 55 cycles at a current density of 100 mA·g(-1), which is three times higher than the capacity of graphite-based anodes. The amorphous NFs facilitated Li2O decomposition, thereby enhancing the reversible capacity. ZnO prevented the aggregation of Sn, which, in turn, conferred stable and high discharge capacity to the cell. Overall, the SnO(x)-ZnO CNFs were shown to exhibit remarkably high capacity retention and high reversible and rate capacities as Li ion battery anodes.

Direct planting of ultrafine MoO2+δ nanoparticles in carbon nanofibers by electrospinning: self-supported mats as binder-free and long-life anodes for lithium-ion batteries

Three-dimensional interconnected carbon nanofibrous mats containing well-dispersed MoO_2+δ nanocrystals are fabricated through electrospinning for high-performance Li-ion battery anodes.