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.

Chiral Magneto-Optical Properties of Supra-Assembled Fe3O4 Nanoparticles

Research on the chiral magneto-optical properties of inorganic nanomaterials has enabled novel applications in advanced optical and electronic devices. However, the corresponding chiral magneto-optical responses have only been studied under strong magnetic fields of ≥1 T, which limits the wider application of these novel materials. In this paper, we report on the enhanced chiral magneto-optical activity of supra-assembled Fe₃O₄ magnetite nanoparticles in the visible range at weak magnetic fields of 1.5 mT. The spherical supra-assembled particles with a diameter of ∼90 nm prepared by solvothermal synthesis had single-crystal-like structures, which resulted from the oriented attachment of nanograins. They exhibited superparamagnetic behavior even with a relatively large supraparticle diameter that exceeded the size limit for superparamagnetism. This can be attributed to the small size of nanograins with a diameter of ∼12 nm that constitute the suprastructured particles. Magnetic circular dichroism (MCD) measurements at magnetic fields of 1.5 mT showed distinct chiral magneto-optical activity from charge transfer transitions of magnetite in the visible range. For the supraparticles with lower crystallinity, the MCD peaks in the 250-550 nm range assigned as the ligand-to-metal charge transfer (LMCT) and the inter-sublattice charge transfer (ISCT) show increased intensities in comparison to those with higher crystallinity samples. On the contrary, the higher crystallinity sample shows higher MCD intensities near 600-700 nm for the intervalence charge transfer (IVCT) transition. The differences in MCD responses can be attributed to the crystallinity determined by the reaction time, lattice distortion near grain boundaries of the constituent nanocrystals, and dipolar interactions in the supra-assembled structures.

Fe3O4/Graphene Composite Anode Material for Fast-Charging Li-Ion Batteries

Composite anode material based on Fe₃O₄ and reduced graphene oxide is prepared by base-catalysed co-precipitation and sonochemical dispersion. Structural and morphological characterizations demonstrate an effective and homogeneous embedding of Fe₃O₄ nanoparticles in the carbonaceous matrix. Electrochemical characterization highlights specific capacities higher than 1000 mAh g^-1 at 1C, while a capacity of 980 mAhg^-1 is retained at 4C, with outstanding cycling stability. These results demonstrate a synergistic effect by nanosize morphology of Fe₃O₄ and inter-particle conductivity of graphene nanosheets, which also contribute to enhancing the mechanical and cycling stability of the electrode. The outstanding capacity delivered at high rates suggests a possible application of the anode material for high-power systems.

Facile Preparation of Fe3O4 Nanoparticles/Reduced Graphene Oxide Composite as an Efficient Anode Material for Lithium-Ion Batteries

Iron oxides are considered promising electrode materials owing to their capability of lithium storage, but their poor conductivity and large volume expansion lead to unsatisfactory cycling stability. In this paper, an inexpensive, highly effective, and facile approach to the synthesis of Fe3O4 nanoparticles/reduced graphene oxide composite (Fe3O4/RGO) is designed. The synthesized Fe3O4/RGO composite exhibits high reversible capability and excellent cyclic capacity as an anode material in lithium-ion batteries (LIBs). A reversible capability of 701.8 mAh/g after 50 cycles at a current density of 200 mA·g−1 can be maintained. The synergetic effect of unique structure and high conductivity RGO promises a well soakage of electrolyte, high structure stability, leading to an excellent electrochemical performance. It is believed that the study will provide a feasible strategy to produce transition metal oxide/carbon composite electrodes with excellent electrochemical performance for LIBs.

Enhanced adsorption of malathion and phoxim by a three-dimensional magnetic graphene oxide-functionalized citrus peel-derived bio-composite

By integrating the steps of direct magnetization and one-pot pyrolysis, a three-dimensional (3D) magnetic graphene oxide-functionalized citrus peel-derived bio-composite (mGOBC) was synthesized and characterized successfully, and it was proved to possess a three-dimensional (3D) porous architecture and graphitic structure. Its potential as an enrichment adsorbent was investigated using adsorption kinetics and adsorption isotherm models to establish an effective analytical method for the determination of organophosphorus pesticides (OPPs) in vegetables. The experimental results indicated that the adsorption was better fitted with the pseudo second order model and Langmuir isotherm model, and the maximum adsorption capacities for malathion and phoxim were 25.26 mg g-1 and 42.31 mg g-1, respectively. It was found that the graphitic structure of mGOBC resulted in π-π EDA (electron donor-acceptor) interaction with the benzene rings, electron-donating N, P, and S atoms in the analytes, which assisted adsorption. Subsequently, Plackett-Burman (P-B) experimental design, central composite design (CCD) and response surface methodology (RSM) were employed to develop an analytical method based on the mGOBC adsorbent. Under optimal conditions, the developed method is accurate and precise. The novel synthesized mGOBC can efficiently achieve removal and trace determination of harmful OPPs.

Impact of the Transition Metal Dopant in Zinc Oxide Lithium-Ion Anodes on the Solid Electrolyte Interphase Formation

Conversion/alloying materials (CAMs) provide substantially higher specific capacities than graphite, the state-of-the-art lithium-ion battery anode material. The ability to host much more lithium per unit weight and volume is, however, accompanied by significant volume changes, which challenges the realization of a stable solid electrolyte interphase (SEI). Herein, the comprehensive characterization of the composition and evolution of the SEI on transition metal (TM) doped zinc oxide as CAM model compound, is reported, with a particular focus on the impact of the TM dopant (Fe or Co). The results unveil that the presence of iron specifically triggers the electrolyte decomposition. However, this detrimental effect can be avoided by stabilizing the interface with the electrolyte by a carbonaceous coating. These findings provide a great leap forward toward the enhanced understanding of such doped materials and (transition) metal oxide active materials in general.

A Guideline for Effectively Synthesizing and Characterizing Magnetic Nanoparticles for Advancing Nanobiotechnology: A Review

The remarkable multimodal functionalities of magnetic nanoparticles, conferred by their size and morphology, are very important in resolving challenges slowing the progression of nanobiotechnology. The rapid and revolutionary expansion of magnetic nanoparticles in nanobiotechnology, especially in nanomedicine and therapeutics, demands an overview of the current state of the art for synthesizing and characterizing magnetic nanoparticles. In this review, we explain the synthesis routes for tailoring the size, morphology, composition, and magnetic properties of the magnetic nanoparticles. The pros and cons of the most popularly used characterization techniques for determining the aforementioned parameters, with particular focus on nanomedicine and biosensing applications, are discussed. Moreover, we provide numerous biomedical applications and highlight their challenges and requirements that must be met using the magnetic nanoparticles to achieve the most effective outcomes. Finally, we conclude this review by providing an insight towards resolving the persisting challenges and the future directions. This review should be an excellent source of information for beginners in this field who are looking for a groundbreaking start but they have been overwhelmed by the volume of literature.

Rational design of multi-walled carbon nanotube@hollow Fe3O4@C coaxial nanotubes as long-cycle-life lithium ion battery anodes

In this work, we report a high-performance anode material created by rationally encapsulating multi-walled carbon nanotubes (MWNTs) within hollow Fe₃O₄ nanotubes followed by applying a carbon coating. When tested for lithium storage, as-prepared MWNT@hollow Fe₃O₄@C coaxial nanotubes present high specific capacity, superior rate performance, and outstanding cycling stability. It is capable of delivering high capacities of 758 mA h g^-1 at 500th cycle at 0.2 A g^-1, and 409 mA h g^-1 after 1000 cycles at a high rate of 1.5 A g^-1. This excellent performance can be attributed to its unique architecture, which provides high electrical conductivity, offers enough void space for volume accommodation, and mitigates the pulverization of Fe₃O₄ during cycles.

Biomass-Derived Carbon Paper to Sandwich Magnetite Anode for Long-Life Li-Ion Battery

Metal oxides can deliver high capacity to Li-ion batteries, surpassing conventional graphite, but they suffer from a huge volume change during charging-discharging and poor cycle life. Herein, we merge the dual strategies of 3D-network support and sandwiching design to tackle such issue. We develop a skillful O₂-NH₃ reactive pyrolysis of cellulose, where the preoxidation and the aminolysis result in the spatially separated charring of cellulose chains. A cellulose fiber is wonderfully converted into several ultrathin twisted graphenic sheets instead of a dense carbon fiber, and consequently, a cellulose paper is directly transformed into a porous flexible carbon paper with high surface area and conductivity (denoted as CP). CP is further fabricated as a 3D-network support into the hybrid CP@Fe₃O₄@RGO, where RGO is reduced graphene oxide added for sandwiching Fe₃O₄ particles. As a binder-free free-standing anode, CP@Fe₃O₄@RGO effectively fastens Fe₃O₄ and buffers the volume changes on cycling, which stabilizes the passivating layer and lifts the Coulombic efficiency. The anode thus presents an ultralong cycle life of >2000 running at a high capacity level of 1160 mAh g^-1. It additionally facilitates electron and ion transports, boosting the rate capability. CP and CP@Fe₃O₄@RGO represent a technological leap underpinning next-generation long-life high-capacity high-power batteries.

Hierarchical porous hollow FeFe(CN)6 nanospheres wrapped with I-doped graphene as anode materials for lithium-ion batteries

Hierarchical porous hollow FeFe(CN)₆ nanospheres were synthesized via a facile anisotropic chemical etching route and integrated with I-doped graphene (IG) to form FeFe(CN)₆@IG composites, which were used as anode materials for the lithium-ion battery (LIB) and exhibited high specific capacities, excellent rate properties, and superior cycling stabilities.

The electrochemical properties of Co3O4 as a lithium-ion battery electrode: a first-principles study

Extensive first principles calculations were performed to study the structural and electrochemical features of Co3O4 during its lithiation process as an anode material for lithium-ion batteries (LIBs). We found that with up to 8 mol Li in Co3O4, the formed LinCo3O4 structures are stable for low Li concentrations of n ≤ 1, but obvious structure distortions and volume expansions occur for LinCo3O4 with n > 1. This may be the reason why Co3O4 has a high Li capability but low cycling life as a LIB anode. The ab initio molecular dynamics simulations for LinCo3O4 (n = 2, 4, 8) further suggest a two-step electrochemistry process of Co3O4 → CoO → Co upon the lithiation process. We detected a distorted surface structure as Li atoms react with the Co3O4(110) surface, which also reduces the rate capability of the Co3O4 anode.

Lithium-ion storage performances of sunflower-like and nano-sized hollow SnO2 spheres by spray pyrolysis and the nanoscale Kirkendall effect

Nanostructured metal selenides with a variety of morphologies are crucial for fabricating porous, hollow metal-oxide nanomaterials by nanoscale Kirkendall diffusion. Herein, SnSe-SnO2 composite powders and SnSe nanospheres were synthesized via one-pot spray pyrolysis by optimizing the concentration of the Se precursor in the spray solution; these were then used to fabricate sunflower-like SnO2 and hollow SnO2 nanospheres, respectively, via nanoscale Kirkendall diffusion. Post-treatment of the SnSe-decorated SnO2 under air produced sunflower-like SnO2, in which ray and disk florets consisting of hollow nanoplates and dense nanospheres, respectively, were present. The mean diameter of the homogeneous hollow SnO2 nanospheres was 150 nm. The hollow morphology shortens the diffusion length, increasing the contact area between the electrolyte and voids and buffering large volume changes during repeated cycling. As anode materials for lithium-ion batteries, the hollow SnO2 nanospheres showed excellent cycling and rate performances. The discharge capacity of the hollow SnO2 nanospheres, after 500 cycles from 0.001 V to 3.0 V, was 1043 mA h g-1, at a current density of 3.0 A g-1. The hollow SnO2 nanospheres showed a high reversible capacity of 638 mA h g-1, even at current density as high as 10 A g-1.

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.

Carbon nanotube entangled Mn3O4 octahedron as anode materials for lithium-ion batteries

A nanocomposite of Mn₃O₄ octahedrons entangled by carbon nanotubes (CNTs) was synthesized by a hydrothermal method assisted with a non-ionic surfactant. The integration of octahedral structure and CNTs could offer many critical features, which are needed for high activity anodes, such as fast ion diffusion, good electronic conductivity, and skeleton supporting function, thus enabling the nanocomposite-based anodes with excellent electrochemical performance. In addition, CNTs can not only serve as the conductive network and structure skeleton to improve the anode performance, but also play an indispensable role in the formation of more uniform Mn₃O₄ octahedrons. The lithium-ion batteries based on the CNTs-entangled Mn₃O₄ octahedrons delivered a high capacity of over 800 mAh g^-1 at a current density of 0.2 C for 200 cycles, and even as high as 678.4 mAh g^-1 when cycled at 0.5 C after 400 cycles, exhibiting a high capability and ultralong cycle life.

A Tunable 3D Nanostructured Conductive Gel Framework Electrode for High-Performance Lithium Ion Batteries

This study develops a tunable 3D nanostructured conductive gel framework as both binder and conductive framework for lithium ion batteries. A 3D nanostructured gel framework with continuous electron pathways can provide hierarchical pores for ion transport and form uniform coatings on each active particle against aggregation. The hybrid gel electrodes based on a polypyrrole gel framework and Fe₃ O₄ nanoparticles as a model system in this study demonstrate the best rate performance, the highest achieved mass ratio of active materials, and the highest achieved specific capacities when considering total electrode mass, compared to current literature. This 3D nanostructured gel-based framework represents a powerful platform for various electrochemically active materials to enable the next-generation high-energy batteries.

Evaluation of electrochemical performances of ZnFe2O4/γ-Fe2O3 nanoparticles prepared by laser pyrolysis

ZnFe₂O₄/Fe₂O₃ nanocomposites obtained by laser pyrolysis were evaluated for lithium-ion batteries application.

Porous 3D carbon decorated Fe3O4 nanocomposite electrode for highly symmetrical supercapacitor performance

Fe₃O₄ coated porous hydrochar nanocomposite for high performance supercapacitors with a wide potential window (1.8 V) and high energy density.

Fluorescence Probe Based on an Amino-Functionalized Fluorescent Magnetic Nanocomposite for Detection of Folic Acid in Serum

A new fluorescence probe constructed with a multifunctional nanocomposite, Fe₃O₄-ZnS:Mn²⁺/SiO₂-NH₂, was successfully synthesized and then used to detect folic acid in real serum samples. The nanocomposite was characterized by fluorescence spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, and physical property measurement system. With the addition of analyte, the Fe₃O₄-ZnS:Mn²⁺/SiO₂-NH₂ composite and folic acid formed a new complex because cross-linking of the amino and carboxyl groups participated in the condensation reaction. Then, the energy of quantum dots was transferred to the complex and led to quenching of the fluorescence. Moreover, the fluorescence intensity decreased significantly as the concentration of folic acid increased, and the fluorescence quenching ratio F₀/F was related to the folic acid concentration in the range from 0.1 to 5 μg mL^-1. This method was used for detecting folic acid in real serum samples and gave recoveries in the range of 89.0%-96.0%, with relative standard deviations of 1.2%-3.9%. The detection limit was 9.6 ng mL^-1 (S/N = 3). These satisfactory and simple results showed the great potential of this fluorescence probe in the field of pharmaceutical analysis.

Designed Construction of a Graphene and Iron Oxide Freestanding Electrode with Enhanced Flexible Energy-Storage Performance

In this work, a bendable graphene@iron oxide hybrid film (GFeF) electrode was fabricated through a filtration-assisted self-assembly method. Morphological characterization of GFeF revealed a uniform distribution of iron oxide nanoparticles between graphene nanosheets. Surface chemical characterization confirmed that graphene oxide in the as-prepared hybrid film was effectively reduced after thermal reduction. The electrochemical performance of a GFeF half-cell versus Li/Li(+) exhibited high gravimetric capacity (855.2 mAh g(-1) at 0.02 A g(-1)), high volumetric capacity (1949.9 mAh cm(-3) at 0.02 A g(-1)), and superior cycling stability (93% capacitance retention after 500 cycles). On the basis of such a bendable electrode, a hybrid Li-ion supercapacitor that offers an operation voltage of 3.5 V and delivers a high energy density (129.6 Wh kg(-1)) like a Li-ion battery combined with a high power density (1870 W kg(-1)) like a supercapacitor was fabricated. In addition to the superior energy-storage capability, the as-fabricated prototype pouch cell also exhibited excellent mechanical flexibility and stable electrochemical performances under dynamic bending. The viability of such an energy-storage device provides a possible design pathway for future wearable electronics.

Hollow Nanobarrels of α-Fe2O3 on Reduced Graphene Oxide as High-Performance Anode for Lithium-Ion Batteries

Alpha-phase iron oxide nanoparticles (α-NPs), α-iron oxide hollow nanobarrels (α-HNBs), and α-HNBs on reduced graphene oxide (α-HNBs/RGO) for Li-ion batteries (LIBs) were synthesized by a time-efficient microwave method to improve the low electrical conductivity of iron oxide and exploit the porous structure of RGO, which prevents the volume expansion of α-Fe2O3 during the insertion/extraction. On the other hand, α-HNBs (∼200 nm in diameter, ∼360 nm in length) provide a short diffusion path for Li ions and accommodate the strain generated by the volume change. The α-HNBs/RGO hybrid structure was synthesized by a one-step microwave-assisted hydrothermal method to bond α-HNBs with RGO. The as-prepared α-HNBs/RGO electrode exhibited a superior reversible capacity of 1279 mA h g(-1) at 0.5 C after the first cycle; such a capacity was nearly recovered after numerous cycles (2nd to 100th cycle, 95%). The long-term cyclability of α-HNBs/RGO shows 478 mA h g(-1) after 1000 cycles. Moreover, the α-HNBs/RGO electrode shows a high rate capacity of 403 mA h g(-1) even at 10 C. The α-HNBs/RGO exhibited a better electrochemical performance that could be attributed to the absence of nanoparticle agglomeration and RGO restacking, which provided a buffer effect against the volume expansion, promoted electrical conductivity and high structural integrity.

Porous Mn2O3 microcubes with exposed {001} facets as electrode for lithium ion batteries

Porous Mn₂O₃ microcubes with exposed {001} facets have been obtained and the Li-ion batteries in which they are applied deliver a high reversible capacity.

Preparation of light core/shell magnetic composite microspheres and their application for lipase immobilization

Fe₃O₄@P(GMA-DVB-MAA) magnetic composite microspheres were prepared by facile one-pot distillation–precipitation polymerization and were modified with amino groups for the immobilization of lipase.

Electrochemical energy storage in Mn2O3 porous nanobars derived from morphology-conserved transformation of benzenetricarboxylate-bridged metal–organic framework

MOF-derived Mn₂O₃ shows a high capacity of ∼410 mA h g⁻¹ as a 2 V anode and an ultrahigh energy density of 147.4 W h kg⁻¹ as a supercapacitor.

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.

Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications

This review focuses on the recent development and various strategies in the preparation, microstructure, and magnetic properties of bare and surface functionalized iron oxide nanoparticles (IONPs); their corresponding biological application was also discussed. In order to implement the practical in vivo or in vitro applications, the IONPs must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of IONPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The new functionalized strategies, problems and major challenges, along with the current directions for the synthesis, surface functionalization and bioapplication of IONPs, are considered. Finally, some future trends and the prospects in these research areas are also discussed.

Self-organized sheaf-like Fe3O4/C hierarchical microrods with superior lithium storage properties

Functional nanomaterials with three-dimensional hierarchical structures are of high interest for many practical applications including lithium-ion batteries (LIBs). In this work, self-organized sheaf-like Fe3O4/C microrods constructed by porous nanowires have been synthesized by a facile solvothermal method combined with a subsequent annealing treatment. The morphology of the building blocks could be easily tuned by varying the synthesis parameters. When applied as an anode material for LIBs, these sheaf-like Fe3O4/C porous microrods manifest superior electrochemical lithium storage properties in terms of high reversible capacity, stable cycling capacity retention and good rate capability.