Facile Fabrication of Fe3O4@TiO2@C Yolk–Shell Spheres as Anode Material for Lithium Ion Batteries

Transition metal oxides have been actively exploited for application in lithium ion batteries due to their facile synthesis,high specific capacity,and environmental-friendly.In this paper,Fe3O4@TiO2@C yolk-shell(Y-S)spheres,used as anode material for lithium ion batteries,were successfully fabricated by Stober method.XRD patterns reveal that Fe3O4@TiO2@C Y-S spheres possess a good crystallinity.But the diffraction peaks’intensity of Fe3O4 crystals in the composites is much weaker than that of bare Fe3O4 spheres,indicating that the outer anatase TiO2@C layer can cover up the diffraction peaks of inner Fe3O4 spheres.The yolk-shell structure of Fe3O4@TiO2@C spheres is further characterized by TEM,HAADFSTEM,and EDS mapping.The yolk-shell structure is good for improving the cycling stability of the inner Fe3O4 spheres during lithium ions insertion-extraction processes.When tested at 200 mA/g,the Fe3O4@TiO2@C Y-S spheres can provide a stable discharge capacity of 450 mAh/g over 100 cycles,which is much better than that of bare Fe3O4 spheres and TiO2@C spheres.Furthermore,cyclic voltammetry curves show that the composites have a good cycling stability compared to bare Fe3O4 spheres.

A ternary phased SnO_2-Fe_2O_3/SWCNTs nanocomposite as a high performance anode material for lithium ion batteries

A new SnO2-Fe2O3/SWCNTs（single-walled carbon nanotubes） ternary nanocomposite was first synthesized by a facile hydrothermal approach.SnO2 and Fe2O3 nanoparticles（NPs） were homogeneously located on the surface of SWCNTs,as confirmed by X-ray diffraction（XRD）,transmission electron microscope（TEM） and energy dispersive X-ray spectroscopy（EDX）.Due to the synergistic effect of different components,the as synthesized SnO2-Fe2O3/SWCNTs composite as an anode material for lithium-ion batteries exhibited excellent electrochemical performance with a high capacity of 692 mAh·g-1 which could be maintained after 50 cycles at 200 mA·g-1.Even at a high rate of2000 mA·g-1,the capacity was still remained at 656 mAh·g-1.

Synthesis of well-defined Fe3O4 nanorods/N-doped graphene for lithium-ion batteries

The geometric size and distribution of magnetic nanoparticles are critical to the morphology of graphene （GN） nanocomposites, and thus they can affect the capacity and cycling performance when these composites are used as anode materials in lithium-ion batteries （LiBs）. In this work, Fe304 nanorods were deposited onto fully extended nitrogen-doped GN sheets from a binary precursor in two steps, a hydrothermal process and an annealing process. This route effectively tuned the Fe3O4 nanorod size distribution and prevented their aggregation. The transformation of the binary precursor was characterized by X-ray diffraction （XRD）, Fourier transform infrared （FTIR） spectroscopy, X-ray photoelectron spectroscopy （XPS）, thermogravimetric analysis （TGA）, and transmission electron microscopy （TEM）. XPS analysis indicated the presence of N-doped GN sheets, and that the magnetic nanocrystals were anchored and uniformly distributed on the surface of the flattened N-doped GN sheets. As a high performance anode material, the structure was beneficial for electron transport and exchange, resulting in a large reversible capacity of 929 mA·h·g^-1, high-rate capability, improved cycling stability, and higher electrical conductivity. Not only does the result provide a strategy for extending GN composites for use as LiB anode materials, but it also offers a route for the preparation of other oxide nanorods from binary precursors.

Synthesis of Co3O4 Nanoparticles Wrapped Within Full Carbon Matrix as an Anode Material for Lithium Ion Batteries

A facile polyol-assisted pyro-synthesis method was used to synthesize Co3O4 nanoparticles embedded into carbon matrix without using any conventional carbon source. The surface analysis by scanning electron microscopy showed that the Co3O4 nanoparticles（-20 ± 5 nm） are tightly enwrapped within the carbon matrix. CHN analysis determined the carbon content was only 0.11% in the final annealed sample. The Co3O4@carbon exhibited high capacities and excellent cycling performance as an anode at various current rates（such as 914.4 and 515.5 mAh g^-1 at 0.25 and1.0 C, respectively, after 50 cycles; 318.2 mAh g^-1 at a high current rate of 5.0 C after 25 cycles）. This superior electrochemical performance of the electrode can be attributed to the various aspects, such as,（1） the existence of carbon matrix, which acts as a flexible buffer to accommodate the volume changes during Li^＋ion insertion/deinsertion and facilitates the fast Li^＋and electron transfer and（2） the anchoring of Co3O4 nanoparticles within the carbon matrix prevents particles agglomeration.

Hydrothermal Preparation of Homogeneous Cobalt Oxide Nanomaterials as Stable Anodes for Superior Lithium Ion Batteries

In this study,uniform Co_(3)O_(4) nanoparticles are prepared via a simple and facile hydrothermal synthesis without calcination treatment.When the Co_(3)O_(4)nanomaterials are investigated as anodes for lithium ion batteries,a good electrochemical property is achieved.Particularly,the reversible capacity of the as-synthesized Co_(3)O_(4) nanoparticle has a significant growth from383 mAh g^(-1)of the initial cycle to 471 mAh g^(-1)of the 300 th cycle at 2 A g^(-1).Moreover,when it recovers to 50 mA g^(-1)after different current densities,a superior reversible capacity of 695 mAh g^(-1)can be reached.Such favorable electrochemical properties will make the as-obtained Co_(3)O_(4) have a good application prospect as anode material for lithium ion batteries.

Unique Double Carbon Protection Structured Co₃O₄Anode for Lithium Ion Battery

In this study, novel Carbon aerogel (CA)/Co3O4/Carbon (C) composites with a double protective structure are synthesized through a solvothermal method and in-situ polymerization. The morphology and structure are characterized by X-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Fourier transform infrared spectroscopy (FTIR). The loading content of active anode material Co3O4 in the composite is investigated by thermogravimetry, and the electrochemical properties of the composite are characterized by electrochemical impedance spectroscopy (EIS). The SEM results show that the nano-sized spherical Co3O4 particle is adhered to the inner Carbon aerogel (CA). The HRTEM result indicates the thickness of the prepared Carbon (C) up to 40 nm. Nano-sheet is coated on the surface of the Co3O4 particle. Compared with the pure Co3O4 anode materials, the Carbon aerogel (CA)/Co3O4/Carbon (C) composites have better transport kinetics for both electron and lithium-ion in EIS testing results, which may contribute to its higher specific capacity and higher first coulomb efficiency. Due to the unique structure of the composite material with double protection against the volume expansion of Co3O4 when charged, the Carbon aerogel (CA)/Co3O4/Carbon (C) composite material exhibits better cycle stability with a discharge capacity of 1180 mAh/g after 50 cycles. Therefore, the double protection strategy is verified as an effective method to improve the electrochemical performance of transition metal oxide with carbon composite as an anode material in lithium battery.

Preparation and electrochemical performance of spherical Fe_3O_4 as anode materials for Li-ion batteries

Fe3O4 nano-powder was prepared by the hydrothermal method. The structure and morphology of the product were characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The as-prepared powder has regularly spherical morphology, and the average size of product is about 25 nm. The possible application use of this material as the active mass of anode for rechargeable Li batteries was examined by cyclic voltammeter (CV), galvanostatic charge/discharge.The experimental results showed that this material exhibited large specific capacity at the first cycle, and the discharge and charge capacity retention of this electrode are 37.04% and 48.76%, respectively. Furthermore, the impedance change of Fe3O4 electrode under different cycle number and potential was examined.

Sn_(4)P_(3)-G@C负极在锂离子电池中的应用

磷化锡(Sn_(4)P_(3))作为锂离子电池负极材料,虽然理论比容量(1.255×10^(3) mA⋅h/g)较高,但是在充放电过程中会产生巨大的体积膨胀和颗粒团聚现象,导致容量衰减严重。将石墨烯作为骨架、无定形碳材料作为包覆层,成功地制备了碳包覆Sn_(4)P_(3)-石墨烯复合材料(Sn_(4)P_(3)-G@C)。Sn_(4)P_(3)-G@C在电流密度为0.05 A/g时,循环70次后放电比容量可达0.521×10^(-3) mA⋅h/g;在电流密度为0.10 A/g时,循环150次后放电比容量可达0.433×10^(-3) mA⋅h/g;在电流密度为0.50 A/g时,稳定循环300次,放电比容量可达0.330×10^(-3) mA⋅h/g。片层石墨烯和碳包覆层的共同存在不仅使Sn_(4)P_(3)的结构更加稳定且导电性提升,而且有效缓解体积膨胀,防止颗粒之间的团聚,使Sn_(4)P_(3)-G@C表现出了良好的储锂性能。

具有介孔壳层的空心Fe3O4/碳MOFs衍生材料用于储锂

空心MOFs及其衍生物因其高比表面积和完美的框架结构而受到越来越多的关注,这些特性决定了MOFs材料在储能和催化领域具有极大的应用潜力.然而,目前很少有研究针对空心MOFs的壳层进行修饰,如对壳层表面进行介孔修饰,这将赋予MOFs衍生材料一些新的性能.本文以50 nm尺寸的二氧化硅纳米球为模板,通过配位聚合诱导自组装工艺成功地合成了具有介孔壳层的空心MOFs(MIL-53(Fe)).紧密修饰的介孔结构使空心MOFs的壳层非常薄,从而实现了从MOFs到空心Fe3O4/碳材料的转化.将空心Fe3O4/碳材料作为阳极活性材料用于锂离子电池,该材料表现出优异的电化学性能.即使在0.1 A/g电流密度条件下循环200次,电容量仍可保持在1270 mA h/g.本研究为能源领域多功能化MOFs及其衍生物的设计和制备提供了新的思路.