Iron and silicon oxide doped/PAN-based carbon nanofibers as free-standing anode material for Li-ion batteries

A Temperature-Tolerant Magnesium-Ion Battery Using Ball Cactus-like MgV2O4 as High-Performance Cathode

Safe and high-performance secondary batteries using for all-climate conditions with different temperatures are highly required. Here, we develop a three-dimensional ball cactus-like MgV2O4 as cathode material for magnesium-ion (Mg-ion) batteries. After cycling 300 times, the capacity maintains 111.7 mAh g-1, while Coulombic efficiency stabilizes at about 100 %. Under temperatures of 45 °C and -5 °C, the capacities remain stable after 200 cycles. After three rounds of rate-performance tests, the capacity keeps quite stable. It is ascribed to the ball cactus-like morphology buffers the volumetric change during Mg2+ insertion/extraction, and provides sufficient pathways for ion diffusion, which has been verified by constant-current intermittent titration technology. It is believed that the good performance enables the Mg-ion batteries to have a all-climate capability.

Investigation of Magnetic Electrodes in Conducting Polymeric Materials: Electrochemical Properties of a Fullerene[C60 ]-Pd Polymer and Iron Oxide Magnetic Nanocomposite

A composite of iron oxide magnetic nanoparticles and coordination fullerene polymer (C60 Pd3 )n is formed by chemical deposition of spherical polymer nanoparticles on iron oxide magnetic nanoparticles in benzene containing C60 and Pd(0) complex. The composition of the composite can be controlled by the amount of magnetite and concentration of polymerization precursors as well as the time of polymerization. The magnetic composite material Fe3 O4 -γFe2 O3 /(C60 Pd3 )n is used as a model system to investigate its deposition on a magnetic electrode and its electrochemical properties. The iron oxide magnetic nanoparticles ensure both the magnetic activity of the composite and its nanostructured morphology. Both of these factors are responsible for the enhancement of the electrochemical activity of the polymer phase forming the composite in comparison to the pure polymer material deposited on the same magnetic electrode. In the magnetic field of the electrode, the composite undergoes permanent and strong bonding with the surface of the electrode. The nanostructured morphology of the Fe3 O4 -γFe2 O3 /(C60 Pd3 )n composite also provides very good capacitive properties.

Microwave-Assisted Silanization of Magnetite Nanoparticles Pre-Synthesized by a 3D Microfluidic Platform

Magnetite nanoparticles (Fe3O4 NPs) are among the most investigated nanomaterials, being recognized for their biocompatibility, versatility, and strong magnetic properties. Given that their applicability depends on their dimensions, crystal morphology, and surface chemistry, Fe3O4 NPs must be synthesized in a controlled, simple, and reproducible manner. Since conventional methods often lack tight control over reaction parameters and produce materials with unreliable characteristics, increased scientific interest has been directed to microfluidic techniques. In this context, the present paper describes the development of an innovative 3D microfluidic platform suitable for synthesizing uniform Fe3O4 NPs with fine-tuned properties. On-chip co-precipitation was performed, followed by microwave-assisted silanization. The obtained nanoparticles were characterized from the compositional and microstructural perspectives by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Moreover, supplementary physicochemical investigations, such as Fourier Transform Infrared Spectroscopy (FT-IR), Kaiser Test, Ultraviolet-Visible (UV-Vis) Spectrophotometry, Dynamic Light Scattering (DLS), and Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) analyses, demonstrated the successful surface modification. Considering the positive results, the presented synthesis and functionalization method represents a fast, reliable, and effective alternative for producing tailored magnetic nanoparticles.

A single-crystalline Co3O4 nanoparticle-assembled three-dimensional chain as an ultra-stable magnesium-ion battery cathode at different temperatures

Engineering optimal cathode materials is significant for developing stable magnesium-ion (Mg-ion) batteries. Here, we present a single-crystalline Co₃O₄ nanoparticle-chain three-dimensional (3D) micro/nanostructure as an Mg-ion battery cathode. The hierarchical morphology is composed of radial nanochains self-assembled by single-crystalline nanoparticles, thus significantly facilitating the transfer of electrons and ions. 3D single-crystalline Co₃O₄ as an Mg-ion battery cathode displays a stable capacity of 111.7 mA h g^-1 after 200 cycles with a decay rate per cycle as low as 0.037%. After four rounds of testing, the rate performance remains stable with a tiny decrease from 125.94 to 124.78 mA h g^-1. At temperatures of 45 °C and -5 °C, the cathode still displays good stability and rate-performance. Galvanostatic intermittent titration technique (GITT) results verify a low energy barrier of the Co₃O₄ cathode. It is expected that the single-crystalline nanoparticle-assembled 3D structure and the stable Mg-storage performance will find broad applications for developing other stable energy-storage materials and their batteries.

Constructing a Low-Cost Si-NSs@C/NG Composite by a Ball Milling-Catalytic Pyrolysis Method for Lithium Storage

Silicon-based composites are promising candidates as the next-generation anode materials for high-performance lithium-ion batteries (LIBs) due to their high theoretical specific capacity, abundant reserves, and reliable security. However, expensive raw materials and complicated preparation processes give silicon carbon anode a high price and poor batch stability, which become a stumbling block to its large-scale practical application. In this work, a novel ball milling-catalytic pyrolysis method is developed to fabricate a silicon nanosheet@amorphous carbon/N-doped graphene (Si-NSs@C/NG) composite with cheap high-purity micron-size silica powder and melamine as raw materials. Through systematic characterizations such as XRD, Raman, SEM, TEM and XPS, the formation process of NG and a Si-NSs@C/NG composite is graphically demonstrated. Si-NSs@C is uniformly intercalated between NG nanosheets, and these two kinds of two-dimensional (2D) materials are combined in a surface-to-surface manner, which immensely buffers the stress changes caused by volume expansion and contraction of Si-NSs. Attributed to the excellent electrical conductivity of graphene layer and the coating layer, the initial reversible specific capacity of Si-NSs@C/NG is 807.9 mAh g^-1 at 200 mA g^-1, with a capacity retention rate of 81% in 120 cycles, exhibiting great potential for application as an anode material for LIBs. More importantly, the simple and effective process and cheap precursors could greatly reduce the production cost and promote the commercialization of silicon/carbon composites.

Superhydrophobic polyurethane sponge based on sepiolite for efficient oil/water separation

Massive oil leakage accidents and illegal discharge of oily wastewater have not just destroyed the sustainability of the ecological environment but caused permanent damage to marine ecosystems, which makes it urgent to handle it. In this paper, by means of sol-gel, micro-nan silica that grew from the surface of fibrous sepiolite was organically modified with 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane (PFDS). The superhydrophobic sepiolite/silica firmly attached to the surface of polyurethane sponge under the action of oily epoxy resin with strong adhesion. The sponge exhibited superhydrophobicity and excellent selective oil adsorption capacity (19.98-40 times of their own weight). More importantly, besides the effective separation of immiscible oil-water mixtures (the separation rate reached 98.72%), it could also efficiently separate oil with water and oil with salt solution emulsions. In addition, the sponges kept hydrophobic even after floating in extremely corrosive liquids for 20 h, showing a strong resistance to strong acidic as well as alkaline liquids. After 100 times of mechanical compression, the three-dimensional structure of sponge held still and the water contact angle was greater than 144°, demonstrating an excellent mechanical stability, which provided a reference for its practical application in oil-water separation.

Effect of Copper Selenide Modification on the Conductivity of PA6, PA66, PAN, and PES Fibers

Textile production has been steadily increasing for a few decades and, as a result, the amount of industrial textile waste is also increasing. This waste can be reused as raw material to produce new functional composites. Such materials can be used for special purposes with varying combinations of physical and chemical properties by using polymers modified with thin semiconductive or electrically conductive layers of binary inorganic compounds. In this paper, a study of the possibilities of altering the properties of synthetic fiber conductivity by modification with copper selenide is presented. A two-step adsorption/diffusion method was used for the copper selenide layer forming on the surface of the fibers. The treatment process was repeated cyclically. To evaluate the morphological properties of Cu_xSe treated fibers, scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) were performed. The study showed that the chosen modification method is more suitable for PA and PAN fibers. Dense layers of copper selenides were successfully formed on their surface, which significantly reduced their electrical resistance.

Ultrafast Kinetics in a PAN/MgFe2O4 Flexible Free-Standing Anode Induced by Heterojunction and Oxygen Vacancies

Flexibility and power density are key factors restricting the development of flexible lithium-ion batteries (FLIBs). Interface and defect engineering can modify the intrinsic ion/electron kinetics by regulating the electronic structure. Herein, a polyacrylonitrile/MgFe₂O₄ (PAN-MFO) electrode with heterojunction and oxygen vacancies was first designed and synthesized as a flexible free-standing anode of FLIBs by electrostatic spinning technology. The PAN carbon nanofiber (PAN-CNF) as the skeleton structure provides fast conductive channels, buffers the volume expansion, and enhances the cycle stability. The heterostructure constructs the internal electric field, facilitates the Li⁺/charge transfer, intensifies the Li⁺ adsorption energy, and enhances the interfacial lithium storage. Oxygen vacancies improve the intrinsic conductivity, lower the Li⁺ diffusion barrier, weaken the Fe-O bonding, and facilitate the conversion reaction. Because of the synergistic effect of the multifunctional structure, the PAN-MFO shows superior cycle and rate performance with ultrafast kinetics. Flexible LiCoO₂/PAN-MFO full pouch cells were also assembled that demonstrated a stable cycle performance and power supply in both the plain and bent states.

Vertically Aligned n-Type Silicon Nanowire Array as a Free-Standing Anode for Lithium-Ion Batteries

Due to its high theoretical specific capacity, a silicon anode is one of the candidates for realizing high energy density lithium-ion batteries (LIBs). However, problems related to bulk silicon (e.g., low intrinsic conductivity and massive volume expansion) limit the performance of silicon anodes. In this work, to improve the performance of silicon anodes, a vertically aligned n-type silicon nanowire array (n-SiNW) was fabricated using a well-controlled, top-down nano-machining technique by combining photolithography and inductively coupled plasma reactive ion etching (ICP-RIE) at a cryogenic temperature. The array of nanowires ~1 µm in diameter and with the aspect ratio of ~10 was successfully prepared from commercial n-type silicon wafer. The half-cell LIB with free-standing n-SiNW electrode exhibited an initial Coulombic efficiency of 91.1%, which was higher than the battery with a blank n-silicon wafer electrode (i.e., 67.5%). Upon 100 cycles of stability testing at 0.06 mA cm⁻², the battery with the n-SiNW electrode retained 85.9% of its 0.50 mAh cm⁻² capacity after the pre-lithiation step, whereas its counterpart, the blank n-silicon wafer electrode, only maintained 61.4% of 0.21 mAh cm⁻² capacity. Furthermore, 76.7% capacity retention can be obtained at a current density of 0.2 mA cm⁻², showing the potential of n-SiNW anodes for high current density applications. This work presents an alternative method for facile, high precision, and high throughput patterning on a wafer-scale to obtain a high aspect ratio n-SiNW, and its application in LIBs.

Multiscale Understanding of Covalently Fixed Sulfur-Polyacrylonitrile Composite as Advanced Cathode for Metal-Sulfur Batteries

Metal-sulfur batteries (MSBs) provide high specific capacity due to the reversible redox mechanism based on conversion reaction that makes this battery a more promising candidate for next-generation energy storage systems. Recently, along with elemental sulfur (S8 ), sulfurized polyacrylonitrile (SPAN), in which active sulfur moieties are covalently bounded to carbon backbone, has received significant attention as an electrode material. Importantly, SPAN can serve as a universal cathode with minimized metal-polysulfide dissolution because sulfur is immobilized through covalent bonding at the carbon backbone. Considering these unique structural features, SPAN represents a new approach beyond elemental S8 for MSBs. However, the development of SPAN electrodes is in its infancy stage compared to conventional S8 cathodes because several issues such as chemical structure, attached sulfur chain lengths, and over-capacity in the first cycle remain unresolved. In addition, physical, chemical, or specific treatments are required for tuning intrinsic properties such as sulfur loading, porosity, and conductivity, which have a pivotal role in improving battery performance. This review discusses the fundamental and technological discussions on SPAN synthesis, physicochemical properties, and electrochemical performance in MSBs. Further, the essential guidance will provide research directions on SPAN electrodes for potential and industrial applications of MSBs.

Magnetite nanoparticles: Synthesis methods - A comparative review

Iron oxide-based nanoparticles have gathered tremendous scientific interest towards their application in a variety of fields. Magnetite has been particularly investigated due to its readily availability, versatility, biocompatibility, biodegradability, and special magnetic properties. As the behavior of nano-scale magnetite is in direct relation to its shape, size, and surface chemistry, accurate control over the nanoparticle synthesis process is essential in obtaining quality products for the intended end uses. Several chemical, physical, and biological methods are found in the literature and implemented in the laboratory or industrial practice. However, non-conventional methods emerged in recent years to bring unprecedented synthesis performances in terms of better-controlled morphologies, sizes, and size distribution. Particularly, microfluidic methods represent a promising technology towards smaller reagent volume use, waste reduction, precise control of fluid mixing, and ease of automation, overcoming some of the major drawbacks of conventional bulk methods. This review aims to present the main properties, applications, and synthesis methods of magnetite, together with the newest advancements in this field.

Scalable Synthesis of Porous SiFe@C Composite with Excellent Lithium Storage

Utilizing cost-effective raw materials to prepare high-performance silicon-based anode materials for lithium-ion batteries (LIBs) is both challenging and attractive. Herein, a porous SiFe@C (pSiFe@C) composite derived from low-cost ferrosilicon is prepared via a scalable three-step procedure, including ball milling, partial etching, and carbon layer coating. The pSiFe@C material integrates the advantages of the mesoporous structure, the partially retained FeSi₂ conductive phase, and a uniform carbon layer (12-16 nm), which can substantially alleviate the huge volume expansion effect in the repeated lithium-ion insertion/extraction processes, effectively stabilizing the solid-electrolyte interphase (SEI) film and markedly enhancing the overall electronic conductivity of the material. Benefiting from the rational structure, the obtained pSiFe@C hybrid material delivers a reversible capacity of 1162.1 mAh g^-1 after 200 cycles at 500 mA g^-1 , with a higher initial coulombic efficiency of 82.30 %. In addition, it shows large discharge capacities of 803.1 and 600.0 mAh g^-1 after 500 cycles at 2 and 4 A g^-1 , respectively, manifesting an excellent electrochemical lithium storage. This work provides a good prospect for the commercial production of silicon-based anode materials for LIBs with a high lithium-storage capacity.