Preparation and lithium storage performances of mesoporous Fe₃O₄@C microcapsules

Bionic Capsule Lithium-Ion Battery Anodes for Efficiently Inhibiting Volume Expansion

Magnetite (Fe3O4) has a large theoretical reversible capacity and rich Earth abundance, making it a promising anode material for LIBs. However, it suffers from drastic volume changes during the lithiation process, which lead to poor cycle stability and low-rate performance. Hence, there is an urgent need for a solution to address the issue of volume expansion. Taking inspiration from how glycophyte cells mitigate excessive water uptake/loss through their cell wall to preserve the structural integrity of cells, we designed Fe3O4@PMMA multi-core capsules by microemulsion polymerization as a kind of anode materials, also proposed a new evaluation method for real-time repair effect of the battery capacity. The Fe3O4@PMMA anode shows a high reversible specific capacity (858.0 mAh g-1 at 0.1 C after 300 cycles) and an excellent cycle stability (450.99 mAh g-1 at 0.5 C after 450 cycles). Furthermore, the LiNi0.8Co0.1Mn0.1O2/Fe3O4@PMMA pouch cells exhibit a stable capacity (200.6 mAh) and high-capacity retention rate (95.5 %) after 450 cycles at 0.5 C. Compared to the original battery, the capacity repair rate of this battery is as high as 93.4 %. This kind of bionic capsules provide an innovative solution for improving the electrochemical performance of Fe3O4 anodes to promote their industrial applications.

Yolk-shell porous Fe3O4@C anchored on graphene as anode for Li-ion half/full batteries with high rate capability and long cycle life

Iron oxides have been widely studied as anode materials for lithium-ion batteries (LIBs) due to their high conductivity (5 × 10⁴ S m^-1) and high capacity (ca. 926 mAh g^-1). However, having a large volume change and being highly prone to dissolution/aggregation during charge/discharge cycles hinder their practical application. Herein, we report a design strategy for constructing yolk-shell porous Fe₃O₄@C anchored on graphene nanosheets (Y-S-P-Fe₃O₄/GNs@C). This particular structure can not only introduce sufficient internal void space to accommodate the volume change of Fe₃O₄ but also afford a carbon shell to restrict Fe₃O₄ overexpansion, thus greatly improving capacity retention. In addition, the pores in Fe₃O₄ can effectively promote ion transport, and the carbon shell anchored on graphene nanosheets is capable of enhancing overall conductivity. Consequently, Y-S-P-Fe₃O₄/GNs@C features a high reversible capacity of 1143 mAh g^-1, an excellent rate capacity (358 mAh g^-1 at 10.0 A g^-1), and a prolonged cycle life with robust cycling stability (579 mAh g^-1 remaining after 1800 cycles at 2.0 A g^-1) when assembled into LIBs. The assembled Y-S-P-Fe₃O₄/GNs@C//LiFePO₄ full-cell delivers a high energy density of 341.0 Wh kg^-1 at 37.9 W kg^-1. The Y-S-P-Fe₃O₄/GNs@C is proved to be an efficient Fe₃O₄-based anode material for LIBs.

Synthesis of Novel Magnetic Carbon Microtube-Based Solid Acid and Its Catalytic Activities for Biodiesel Synthesis

Novel magnetic carbon microtube-based solid acid was synthesized via the carbonization of FeCl3-doped willow catkin and benzenediazoniumsulfonate acid-based sulfonation. The biomass willow catkin provided the special microtube structure and the high surface area of 215 m2/g for the novel solid acid. The microtube structure was well conserved during the mild carbonization (400 °C) and sulfonation process. The large number of acidic sites (2.3 mmol/g) on the microtube surface was quite accessible to reactants. Its magnetic properties offered a simple separation process. The novel solid acid showed very high activity for biodiesel synthesis, using cooking oils as raw material, which gave a total yield of 99% and free fatty acid conversion of 98.7% under mild conditions (70 °C). The facile synthetic process, high activity, high stability, and high recovery simplicity were the main properties of the novel magnetic solid acid, which is one of the best choices for biodiesel synthesis.

Comparison of the Surface Properties of Hydrothermally Synthesised Fe3O4@C Nanocomposites at Variable Reaction Times

The influence of variable reaction time (tr) on surface/textural properties (surface area, total pore volume, and pore diameter) of carbon-encapsulated magnetite (Fe3O4@C) nanocomposites fabricated by a hydrothermal process at 190 °C for 3, 4, and 5 h was studied. The properties were calculated using the Brunauer-Emmett-Teller (BET) isotherms data. The nanocomposites were characterised using Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetry, and scanning and transmission electron microscopies. Analysis of variance shows tr has the largest effect on pore volume (F value = 1117.6, p value < 0.0001), followed by the surface area (F value = 54.8, p value < 0.0001) and pore diameter (F value = 10.4, p value < 0.001) with R2-adjusted values of 99.5%, 88.5% and 63.1%, respectively. Tukey and Fisher tests confirmed tr rise to have caused increased variations in mean particle sizes (11-91 nm), crystallite sizes (5-21 nm), pore diameters (9-16 nm), pore volume (0.017-0.089 cm3 g-1) and surface area (7.6-22.4 m2 g-1) of the nanocomposites with individual and simultaneous confidence limits of 97.9 and 84.4 (p-adj < 0.05). The nanocomposites' retained Fe-O vibrations at octahedral (436 cm-1) and tetrahedral (570 cm-1) cubic ferrite sites, modest thermal stability (37-60 % weight loss), and large volume-specific surface area with potential for catalytic application in advanced oxidation processes.

Microalgae-Templated Spray Drying for Hierarchical and Porous Fe3O4/C Composite Microspheres as Li-ion Battery Anode Materials

A method of microalgae-templated spray drying to develop hierarchical porous Fe₃O₄/C composite microspheres as anode materials for Li-ion batteries was developed. During the spray-drying process, individual microalgae serve as building blocks of raspberry-like hollow microspheres via self-assembly. In the present study, microalgae-derived carbon matrices, naturally doped heteroatoms, and hierarchical porous structural features synergistically contributed to the high electrochemical performance of the Fe₃O₄/C composite microspheres, enabling a discharge capacity of 1375 mA·h·g^-1 after 700 cycles at a current density of 1 A/g. Notably, the microalgal frameworks of the Fe₃O₄/C composite microspheres were maintained over the course of charge/discharge cycling, thus demonstrating the structural stability of the composite microspheres against pulverization. In contrast, the sample fabricated without microalgal templating showed significant capacity drops (up to ~40% of initial capacity) during the early cycles. Clearly, templating of microalgae endows anode materials with superior cycling stability.

ϵ-FeOOH: A Novel Negative Electrode Material for Li- and Na-Ion Batteries

The demand for eco-friendly materials for secondary batteries has stimulated the exploration of a wide variety of Fe oxides, but their potential as electrode materials remains unknown. In this contribution, ϵ-FeOOH was synthesized using a high-pressure/high-temperature method and examined for the first time in nonaqueous Li and Na cells. Under a pressure of 8 GPa, α-FeOOH transformed into ϵ-FeOOH at 400 °C and then decomposed into α-Fe2O3 and H2O above 500 °C. Here, FeO6 octahedra form [2 × 1] tunnels in α-FeOOH or [1 × 1] tunnels in ϵ-FeOOH. The ϵ-FeOOH/Li cell exhibited a rechargeable capacity (Q recha) of ∼700 mA h·g-1 at 0.02-3.0 V, whereas the ϵ-FeOOH/Na cell indicated a Q recha of less than 30 mA h·g-1 at 0.02-2.7 V. The discharge and charge profiles of ϵ-FeOOH and α-FeOOH were similar, but the rate capability of ϵ-FeOOH was superior to that of α-FeOOH.

Magnetic biochar catalysts from anaerobic digested sludge: Production, application and environment impact

Regulated disposal or re-utilization of dewatered sludge is of economic benefits and can avoid secondary contamination to the environment; however, feasible and effective management strategies are still lacking. In this study, a peroxydisulfate/zero-valent iron (PDS-ZVI) system is proposed to destroy proteins in soluble extracellular polymeric substances (S-EPS) and loosely bound EPS (LB-EPS) in anaerobic digested sludge (ADS) to improve the dewaterability. Moreover, ADS derived biochars supported via iron oxides (Fe-ADSBC) were generated by dewatering and thermal annealing. Intriguingly, the iron species was discovered to gradually transform from Fe₃O₄ to FeO with increased pyrolysis temperatures from 600 to 1000 °C. The manipulated iron species on the biochar can remarkably impact the catalytic activity in PDS activation and degradation of sulfamethazine (SMT). The in situ radical scavenging and capturing tests revealed that the principal reactive oxygen species (ROS) in Fe-ADSBC/PDS system experienced a variation from OH into SO₄^- at higher annealing temperature (1000 °C). In addition, the carbonaceous ADSBC can promote the catalytic activity of iron oxides by synergistically facilitating the adsorption of reactants and charge transfer through COFe bonds at the interfaces. This study enables the first insights into the properties and catalytic performance of Fe-ADSBC, meanwhile unveils the mechanism, reaction pathways, and environmental impacts of the ultimate transformation products (TPs) from SMT degradation in the Fe-ADSBC/PDS system. The study also contributes to developing value-added green biochar catalysts from bio-wastes towards environmental purification.

Preparation and Electrochemical Properties of Pomegranate-Shaped Fe2O3/C Anodes for Li-ion Batteries

Due to the severe volume expansion and poor cycle stability, transition metal oxide anode is still not meeting the commercial utilization. We herein demonstrate the synthetic method of core-shell pomegranate-shaped Fe₂O₃/C nano-composite via one-step hydrothermal process for the first time. The electrochemical performances were measured as anode material for Li-ion batteries. It exhibits excellent cycling performance, which sustains 705 mAh g^-1 reversible capacities after 100 cycles at 100 mA g^-1. The anodes also showed good rate stability with discharge capacities of 480 mAh g^-1 when cycling at a rate of 2000 mA g^-1. The excellent Li storage properties can be attributed to the unique core-shell pomegranate structure, which can not only ensure good electrical conductivity for active Fe₂O₃, but also accommodate huge volume change during cycles as well as facilitate the fast diffusion of Li ion.

Carbothermal Synthesis of Nitrogen-Doped Graphene Composites for Energy Conversion and Storage Devices

Metal oxides and carbonaceous composites are both promising materials for electrochemical energy conversion and storage devices, such as secondary rechargeable batteries, fuel cells and electrochemical capacitors. In this study, Fe₃O₄ nanoparticles wrapped in nitrogen-doped (N-doped) graphene nanosheets (Fe₃O₄@G) were fabricated by a facile one-step carbothermal reduction method derived from Fe₂O₃ and liquid-polyacrylonitrile (LPAN). The unique two-dimensional structure of N-doped graphene nanosheets, can not only accommodate the volume changes during lithium intercalation/extraction processes and suppress the particles aggregation but also act as an electronically conductive matrix to improve the electrochemical performance of Fe₃O₄ anode, especially the rate capability. What's more, by etching Fe₃O₄@G to remove the iron-based oxide template, porous N-doped graphene composites (NGCs) were prepared and presented abundant pore structure with high specific surface area, delivering a specific capacitance of 172 F·g^-1 at 0.5 A·g^-1. In this way, Fe₂O₃ was both template and activator to adjust the pore size of graphene. And the effect of specific surface area and pore size tuned by the Fe₂O₃ activator were also revealed.

Low-Cost Carbothermal Reduction Preparation of Monodisperse Fe3O4/C Core-Shell Nanosheets for Improved Microwave Absorption

This paper demonstrates a facile and low-cost carbothermal reduction preparation of monodisperse Fe₃O₄/C core-shell nanosheets (NSs) for greatly improved microwave absorption. In this protocol, the redox reaction between sheet-like hematite (α-Fe₂O₃) precursors and acetone under inert atmosphere and elevated temperature generates Fe₃O₄/C core-shell NSs with the morphology inheriting from α-Fe₂O₃. Thus, Fe₃O₄/C core-shell NSs of different sizes ( a) and Fe₃O₄/C core-shell nanopolyhedrons are obtained by using different precursors. Benefited from the high crystallinity of the Fe₃O₄ core and the thin carbon layer, the resultant NSs exhibit high specific saturation magnetization larger than 82.51 emu·g^-1. Simultaneously, the coercivity enhances with the increase of a, suggesting a strong shape anisotropy effect. Furthermore, because of the anisotropy structure and the complementary behavior between Fe₃O₄ and C, the as-obtained Fe₃O₄/C core-shell NSs exhibit strong natural magnetic resonance at a high frequency, enhanced interfacial polarization, and improved impedance matching, ensuring the enhancement of the microwave absorption. The 250 nm NSs-paraffin composites exhibit reflection loss (RL) lower than -20 dB (corresponding to 99% absorption) in a large frequency ( f) range of 2.08-16.40 GHz with a minimum RL of -43.95 dB at f = 3.92 GHz when the thickness is tuned from 7.0 to 1.4 mm, indicating that the Fe₃O₄/C core-shell NSs are a good candidate to manufacture high-performance microwave absorbers. Moreover, the as-developed carbothermal reduction method could be applied for the fabrication of other composites based on ferrites and carbon.

Simple fabrication of Fe3O4/C/g-C3N4 two-dimensional composite by hydrothermal carbonization approach with enhanced photocatalytic performance under visible light

The construction of a multifunctional two dimensional (2D) composite photocatalyst is of great significance as it exhibits enhanced catalytic performance and improved practical usability in contrast to a single component catalyst.

Synthesis of coral-globular-like composite Ag/TiO2-SnO2 and its photocatalytic degradation of rhodamine B under multiple modes

Taking cetyltrimethylammonium bromide (CTAB) as the template and using TiO₂ as the substrate, coral-globular-like composite Ag/TiO₂-SnO₂ (CTAB) was successfully synthesized by the sol-gel combined with a temperature-programmed treatment method. X-ray diffraction, scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, SEM combined with X-ray energy dispersive spectroscopy, and N₂ adsorption-desorption tests were employed to characterize samples' crystalline phase, chemical composition, morphology and surface physicochemical properties. Results showed that composites not only had TiO₂ anatase structure, but also had some generated SnTiO₄, and the silver species was metallic Ag⁰. Ag/TiO₂-SnO₂ (CTAB) possessed a coral-globular-like structure with nanosheets in large quantities. The photocatalytic activity of Ag/TiO₂-SnO₂ (CTAB) had studied by degrading organic dyes under multi-modes, mainly using rhodamine B as the model molecule. Results showed that the coral-globular-like Ag/TiO₂-SnO₂ (CTAB) was higher photocatalytic activity than that of commercial TiO₂, Ag/TiO₂-SnO₂, TiO₂-SnO₂ (CTAB), and TiO₂-SnO₂ under ultraviolet light irradiation. Moreover, Ag/TiO₂-SnO₂ (CTAB) composite can significantly affect the photocatalytic degradation under multi-modes including UV light, visible light, simulated solar light and microwave-assisted irradiation. Meanwhile, the photocatalytic activity of Ag/TiO₂-SnO₂ (CTAB) was maintained even after three cycles, indicating that the catalyst had good usability.

Microwave-assisted synthesis and prototype oxygen reduction electrocatalyst application of N-doped carbon-coated Fe3O4 nanorods

Fe₃O₄ nanorods coated with nitrogen-doped mesoporous carbon (ND-Fe₃O₄@mC) shells of defined thicknesses have been prepared via a new microwave-assisted approach. Microstructural characterization of these ND-Fe₃O₄@mC structures was performed using x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. Following identification, the electrochemical performance of the catalysts was evaluated using linear sweep voltammetry with a rotating disc electrode system. The present investigation reveals enhanced oxygen reduction reaction catalytic activity and the carbon layer thickness influences oxygen diffusion to the active Fe₃O₄ nanorod core.

Effect of Graphene Modified Cu Current Collector on the Performance of Li4Ti5O12 Anode for Lithium-Ion Batteries

Interface design between current collector and electroactive materials plays a key role in the electrochemical process for lithium-ion batteries. Here, a thin graphene film has been successfully synthesized on the surface of Cu current collector by a large-scale low-pressure chemical vapor deposition (LPCVD) process. The modified Cu foil was used as a current collector to support spinel Li₄Ti₅O₁₂ anode directly. Electrochemical test results demonstrated that graphene coating Cu foil could effectively improve overall Li storage performance of Li₄Ti₅O₁₂ anode. Especially under high current rate (e.g., 10 C), the Li₄Ti₅O₁₂ electrode using modified current collector maintained a favorable capacity, which is 32% higher than that electrode using bare current collector. In addition, cycling performance has been improved using the new type current collector. The enhanced performance can be attributed to the reduced internal resistance and improved charge transfer kinetics of graphene film by increasing electron collection and decreasing lithium ion interfacial diffusion. Furthermore, the graphene film adhered on the Cu foil surface could act as an effective protective film to avoid oxidization, which can effectively improve chemical stability of Cu current collector.

Electrochemical possibility of iron compounds in used disposable heating pads and their use in lithium ion batteries

In this study, iron oxides obtained from used disposable heating pads are used as an anode material in lithium ion batteries. Fe3O4 and Fe2O3 phases are identified using XRD. Additionally, the existence of other substances, such as carbon and NaCl, are determined using EDS dot mapping. Purified powder (PP) is prepared by washing the obtained powder (OP) with distilled water and ethanol. Heat-treated powder (HP) is prepared by heating PP at 600 °C. The electrochemical result shows that PP delivers a discharge capacity of ∼700 mAh g(-1) after 50 cycles. HP delivers a higher initial capacity of 1170 mAh g(-1); however, the discharge capacity decreases drastically to 500 mAh g(-1). These results were similar to those determined for commercial iron oxide in previous studies.

Porous γ-Fe2O3 spheres coated with N-doped carbon from polydopamine as Li-ion battery anode materials

Nitrogen doping has been demonstrated to play a crucial role in controlling the electronic properties of carbon-based composites. In this paper, nitrogen-doped carbon coated γ-Fe2O3 (NC@γ-Fe2O3) composite was successfully fabricated through a facile and high-yield strategy, including a hydrothermal reaction process for porous γ-Fe2O3 and a subsequent coating of nitrogen-doped carbon by using dopamine as precursor. The resulting composite combines the superior properties of porous Fe2O3 and heteroatom-doped conductive carbon layer derived from polydopamine. When used as the anode material of the lithium-ion battery, the as-prepared NC@γ-Fe2O3 composite exhibits excellent lithium storage properties in terms of high capacity, stable cycling performance (869.6 mAh g(-1) at the current density of 0.5 A g(-1) after 150 cycles) and excellent rate capability.

Facile Hydrothermal Synthesis of Fe3O4/C Core-Shell Nanorings for Efficient Low-Frequency Microwave Absorption

Using elliptical iron glycolate nanosheets as precursors, elliptical Fe3O4/C core-shell nanorings (NRs) [25 ± 10 nm in wall thickness, 150 ± 40 nm in length, and 1.6 ± 0.3 in long/short axis ratio] are synthesized via a one-pot hydrothermal route. The surface-poly(vinylpyrrolidone) (PVP)-protected-glucose reduction/carbonization/Ostwald ripening mechanism is responsible for Fe3O4/C NR formation. Increasing the glucose/precursor molar ratio can enhance carbon contents, causing a linear decrease in saturation magnetization (Ms) and coercivity (Hc). The Fe3O4/C NRs reveal enhanced low-frequency microwave absorption because of improvements to their permittivity and impedance matching. A maximum RL value of -55.68 dB at 3.44 GHz is achieved by Fe3O4/C NRs with 11.95 wt % C content at a volume fraction of 17 vol %. Reflection loss (RL) values (≤-20 dB) are observed at 2.11-10.99 and 16.5-17.26 GHz. Our research provides insights into the microwave absorption mechanism of elliptical Fe3O4/C core-shell NRs. Findings indicate that ring-like and core-shell nanostructures are promising structures for devising new and effective microwave absorbers.

Bifunctional Ag/Fe/N/C Catalysts for Enhancing Oxygen Reduction via Cathodic Biofilm Inhibition in Microbial Fuel Cells

Limitation of the oxygen reduction reaction (ORR) in single-chamber microbial fuel cells (SC-MFCs) is considered an important hurdle in achieving their practical application. The cathodic catalysts faced with a liquid phase are easily primed with the electrolyte, which provides more surface area for bacterial overgrowth, resulting in the difficulty in transporting protons to active sites. Ag/Fe/N/C composites prepared from Ag and Fe-chelated melamine are used as antibacterial ORR catalysts for SC-MFCs. The structure-activity correlations for Ag/Fe/N/C are investigated by tuning the carbonization temperature (600-900 °C) to clarify how the active-constituents of Ag/Fe and N-species influence the antibacterial and ORR activities. A maximum power density of 1791 mW m(-2) is obtained by Ag/Fe/N/C (630 °C), which is far higher than that of Pt/C (1192 mW m(-2)), only having a decline of 16.14% after 90 days of running. The Fe-bonded N and the cooperation of pyridinic N and pyrrolic N in Ag/Fe/N/C contribute equally to the highly catalytic activity toward ORR. The ·OH or O2(-) species originating from the catalysis of O2 can suppress the biofilm growth on Ag/Fe/N/C cathodes. The synergistic effects between the Ag/Fe heterojunction and N-species substantially contribute to the high power output and Coulombic efficiency of Ag/Fe/N/C catalysts. These new antibacterial ORR catalysts show promise for application in MFCs.

Water-dispersible and magnetically recoverable Fe3O4/Pd@nitrogen-doped carbon composite catalysts for the catalytic reduction of 4-nitrophenol

Water-dispersible and magnetically recoverable Fe₃O₄/Pd@nitrogen-doped carbon catalysts were prepared. The catalysts have good catalytic activity and can be magnetically separated from the reaction solution.

Multifunctional iron oxide–carbon hybrid microrods

Fe_xO_y–C microrods with superior dye adsorption and drug loading abilities were obtained by solvothermal synthesis with annealing.

Facile synthesis of an Fe3O4/FeO/Fe/C composite as a high-performance anode for lithium-ion batteries

An Fe₃O₄/FeO/Fe/C nanocomposite is prepared via a facile and scalable in situ-reduction solid synthesis route and is used as a high-performance LIB anode.

Synthesis of α-Fe2O3, Fe3O4 and Fe2N magnetic hollow nanofibers as anode materials for Li-ion batteries

As-prepared α-Fe₂O₃, Fe₃O₄ and Fe₂N hollow nanofibers are used as anode materials for Li-ion batteries and exhibit excellent electrochemical performances.

Facile one-pot synthesis of carbon/calcium phosphate/Fe3O4 composite nanoparticles for simultaneous imaging and pH/NIR-responsive drug delivery

We report herein a facile one-pot synthesis of carbon/calcium phosphate/Fe₃O₄ composite nanoparticles, which were employed as pH/NIR-responsive drug delivery vehicles for simultaneous MRI and chemo-photothermal therapy.

Ultrafine ferroferric oxide nanoparticles embedded into mesoporous carbon nanotubes for lithium ion batteries

An effective one-pot hydrothermal method for in situ filling of multi-wall carbon nanotubes (CNT, diameter of 20–40 nm, length of 30–100 μm) with ultrafine ferroferric oxide (Fe₃O₄) nanoparticles (8–10 nm) has been demonstrated. The synthesized Fe₃O₄@CNT exhibited a mesoporous texture with a specific surface area of 109.4 m² g⁻¹. The loading of CNT, in terms of the weight ratio of Fe₃O₄ nanoparticles, can reach as high as 66.5 wt%. Compared to the conventional method of using a Al₂O₃ membrane as template to fill CNT with iron oxides nanoparticles, our strategy is facile, effective, low cost and easy to scale up to large scale production (~1.42 g per one-pot). When evaluated for lithium storage at 1.0 C (1 C = 928 mA g⁻¹), the mesoporous Fe₃O₄@CNT can retain at 358.9 mAh g⁻¹ after 60 cycles. Even when cycled at high rate of 20 C, high capacity of 275.2 mAh g⁻¹ could still be achieved. At high rate (10 C) and long life cycling (500 cycles), the cells still exhibit a good capacity of 137.5 mAhg⁻¹.

Effect of Carbon Coating on the Physicochemical and Electrochemical Properties of Fe2O3 Nanoparticles for Anode Application in High Performance Lithium Ion Batteries

Nanoparticulate Fe2O3 and Fe2O3/C composites with different carbon proportions have been prepared for anode application in lithium ion batteries (LIBs). Morphological studies revealed that particles of Fe2O3 in the composites were well-dispersed in the matrix of amorphous carbon. The properties of the γ-Fe2O3 nanoparticles and the correlation with the particle size and connectivity were studied by electron paramagnetic resonance, magnetic, and Mössbauer measurements. The electrochemical study revealed that composites with carbon have promising electrochemical performances. These samples yielded specific discharge capacities of 1200 mAh/g after operating for 100 cycles at 1C. These excellent results could be explained by the homogeneity of particle size and structure as well as the uniform distribution of γ-Fe2O3 nanoparticles in the in situ generated amorphous carbon matrix.

Sustainable synthetic route for γ-Fe2O3/C hybrid as anode material for lithium-ion batteries

A facile, high-yield and sustainable method is developed to synthesize iron oxide/C hybrids. Starch is chosen as the carbon source due to its superior gelatinization property and natural abundance, and ferric nitrate is used as the iron salt for the sustainable synthesis. The iron oxide in the final products exists in the γ-Fe2O3 phase. The γ-Fe2O3/C hybrids are used as anode materials for lithium-ion batteries. The batteries exhibit better cyclability as the content of γ-Fe2O3 decreases, but in turn the reversible capacity declines. The γ-Fe2O3/C hybrid with 63.96 wt% of γ-Fe2O3 has an initial discharge capacity of 1149 mA h g(-1) and after the 80(th) cycle the reversible capacity is maintained at over 720 mA h g(-1) at a current density of 0.5 A g(-1). Even when tested at a current density of 5 A g(-1), a substantial discharge capacity of ∼300 mA h g(-1) can be obtained.