TiO2-coated SnO2 hollow spheres as anode materials for lithium ion batteries

TiO2-coated SnO2(TCS) hollow spheres,which are new anode materials for lithium ion(Li-ion) batteries,were prepared and characterized with X-ray diffraction(XRD) ,scanning electron microscopy(SEM) ,transmission electron microscopy(TEM) ,cyclic voltammetry(CV) ,and galvanostatic charge/discharge tests.The results obtained from XRD,SEM,and TEM show that TiO2 can be uniformly coated on the surface of SnO2 hollow spheres with the assistance of anionic surfactant.The cyclic voltammograms indicate that both TiO2 a...     

Electrochemical synthesis of polypyrrole films over each of well-aligned carbon nanotubes

Polypyrrole (PPy) films were uniformly electropolymerized over each carbon nanotube of the well-aligned carbon nanotube arrays. For comparison, PPy films were also coated on flat metallic titanium (Ti) and platinum (Pt) substrates by the same technique. The synthesis and the redox performance of the PPy films were conducted by cyclic voltammetry (CV). The structural characterization including the thickness and uniformity of the PPy films was carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is observed that the coating of the PPy film over carbon nanotubes is much faster than that on flat Ti/Pt surface. Furthermore, the redox performance of the PPy-coated carbon nanotube electrodes over flat Ti/Pt electrodes was significantly improved due to the high accessible surface area of the carbon nanotubes in the aligned arrays, especially in large film formation charge (Q_film). It is very promising that the electrode developed in this study could be used as high performance electrode in rechargeable batteries.     

Preparation and electrochemical performance of copper foam-supported amorphous silicon thin films for rechargeable lithium-ion batteries

Amorphous Si thin films, which have been deposited on copper foam by radio-frequency (rf) magnetron sputtering, are employed as anode materials of rechargeable lithium-ion batteries. The morphologies and structures of the as-prepared Si thin films are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). Electrochemical performance of lithium-ion batteries with the as-prepared Si films as the anode materials is investigated by cyclic voltammetry and charge-discharge measurements. The results show that the electrode properties of the prepared amorphous Si films are greatly affected by the deposition temperature. The film electrode deposited at an optimum temperature of 300 °C can deliver a specific capacity of ∼2900 mAh/g and a coulombic efficiency above 95% at charge/discharge current density of 0.2C after 30 cycles. The Li⁺ diffusion coefficiency in copper foam-supported Si thin films is determined to be 2.36 × 10⁻⁹ cm²/s.     

磷酸铁锂/石墨烯复合材料的低温微波水热法制备及性能

采用喷雾干燥结合低温微波水热法制备了石墨烯/LiFePO₄复合正极材料,利用SEM、XRD、DLS等对其微观形貌、结构、粒度分布进行了表征,并利用恒流充放电、CV、EIS等测试研究了复合正极材料的电化学性能和电极动力学过程。结果表明,与未包覆的样品相比,石墨烯包覆的LiFePO₄具有优异的倍率性能(5C放电比容量为125.4 mAh?g_-1)和循环稳定性(1C条件下100次充放电后容量保持率在95%左右)。包覆石墨烯后LiFePO₄正极材料的电荷迁移电阻减小,电化学可逆性增强,从而提高了材料的倍率性能。本文提供了一条提高磷酸铁锂正极材料电化学性能的简便途径,具有良好的应用前景。     

锂空气电池空气电极层次多孔碳的制备及其性能

在不同表面活性剂浓度下通过溶胶-凝胶自组装方法制备了具有介孔结构的层次多孔碳材料（HPCs）。用场发射扫描电镜（FE-SEM）、透射电镜（TEM）、氮气吸脱附测试和恒流充放电测试对样品进行物理和电化学性能研究。结果表明：所有的HPCs主要为介孔结构并且具有相似的孔径分布。以HPCs为空气电极载体碳材料的锂空气电池具有较高的放电容量。且相似孔径大小的碳材料为载体的锂空气电池放电容量随着碳材料的比表面积增加而增加。在c（CTAB）=0.27 mol/L时制备的HPCs-3样品具有最佳的电化学性能。通过控制放电深度至800 mA·h/g,电池表现出良好的容量保持率,在0.1 mA/cm2电流密度下,首次放电容量为2050 mA·h/g。     

高分散Li4Ti5O12纳米晶的制备及电化学性能（英文）

以月桂酸为分散剂,采用溶胶-凝胶法合成颗粒尺寸为120～250nm的高分散Li4Ti5O12纳米晶。通过研究表面活性剂月桂酸的含量优化制备工艺,制备出电化学性能最佳的样品。采用XRD、FESEM、TEM、激光粒度分析仪、交流阻抗以及恒流充放电测试,对材料的物理和电化学性能进行表征。在800℃下热处理10h后的高分散性Li4Ti5O12纳米晶显示出优异的电化学性能,在1C倍率下,首次放电容量为163.3mA.h/g,50次放电循环后,放电容量无明显衰减。研究表明,高分散性Li4Ti5O12纳米晶可以缩短锂离子的扩散路径,改善样品的电化学动力过程,有效地提高其高倍率性能。     

Examination of surface films on aluminium and its alloys by low-voltage scanning and scanning transmission electron microscopy

The potential of low-voltage, high-resolution scanning and scanning transmission electron microscopy (SEM/STEM) for morphological characterization of various surface insulating films on aluminium and its alloys has been assessed by examination of porous anodic films, barrier anodic films and corrosion product layers. The characterization shows clearly the value of the approaches, particularly the ability to image directly fine details of appropriately-prepared aluminium surfaces that have usually required examination by transmission electron microscopy (TEM). Such ready characterization assists mechanistic understanding of the contributions of the macroscopic surface and flaws or second phase to the filming and corrosion processes. Further, the approaches are applicable to other materials where such understanding was limited by the sample preparation routes available for TEM.     

Employment of encapsulated Si with mesoporous TiO2 layer as anode material for lithium secondary batteries

Silicon composite of nano-capsule type is newly applied as an active anode material for lithium ion batteries. TiO₂-encapsulated silicon powders were synthesized by a sol-gel reaction with titanium ethoxide. Silicon nanoparticles were successfully embedded into porous titanium oxide capsules that played as a buffer layer against drastic volume changes of silicon during the charge-discharge cycling, consequently leading to the retardation of the capacity fading of intrinsic silicon materials. The electrochemical and structural properties of silicon nanocomposites with different surface areas of encapsulating TiO₂ layer were characterized by X-ray diffraction(XRD), nitrogen gas adsorption analysis by the Brunauer-Emmett-Teller(BET) equation, transmission electron microscopy(TEM), and galvanostatic charge-discharge experiments.     

锂离子电池正极材料的组合化学设计及相变机理

将组合化学应用于功能电极材料开发 ,设计出锂离子电池正极材料三角形分子库。采用空间标码、高温固相平行合成法 ,以锂、钴、锰、镍 4种元素的化合物为原料 ,合成了锂离子二次电池的正极材料。以所测材料的充放电性能为筛选指标 ,成功地确定了电化学性能优良、组成构型一定的正极材料。实验中发现正极材料中因钴、镍、锰的配比不同而产生的相变现象 ,最后还讨论了材料的相变机理     

High-performance anode materials for Na-ion batteries

Na-ion batteries are considered a promising alternative to Li-ion batteries for large-scale energy storage systems due to their low cost and the natural abundance of Na resource. Great effort is making worldwide to develop high-performance electrode materials for Na-ion batteries,which is critical for Na-ion batteries. This review provides a comprehensive overview of anode materials for Na-ion batteries based on Na-storage mechanism: insertion-based materials, alloy-based materials, conversion-based materials and organic composites. And we summarize the Nastorage mechanism of those anode materials and discuss their failure mechanism. Furthermore, the problems and challenges associated with those anodes are pointed out,and feasible strategies are proposed for designing highperformance anode materials. According to the current state of research, the search for suitable anode materials for Na-ion batteries is still challenging although substantial progress has been achieved. Nevertheless, we believe that high-performance Na-ion batteries would be promising for practical applications in large-scale energy storage systems in the near future.     

Electrochemical properties of NiO/Co-P nanocomposite as anode materials for lithium ion batteries

NiO/Co-P nanocomposite is prepared by an electroless cobalt plating technique. The as-prepared composite is characterized by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images reveal that the NiO particles are about 200 nm in size, which are modified by Co-P nanoparticles of about 30 nm. The electrochemical properties as anode materials for lithium ion batteries are examined by cyclic voltammetry (CV) and discharge-charge tests. The results show that, compared with the bare NiO without electroless cobalt plating, NiO/Co-P nanocomposite exhibits a smaller polarization and a better rate capability, which is attributed to the Co-P nanoparticles.     

Characterizing III–V heteroepitaxial structures

A complementary characterization scheme for high-volume production of III–V heteroepitaxial structures is described, focusing on the cost-effectiveness and utility of the techniques, AlGaAs/InGaAs/GaAs heteroepitaxial layers grown by molecular beam epitaxy were studied by cross-sectional transmission electron microscopy (TEM) and photoluminescence (PL) techniques. The presence of a range of layer thicknesses, fine periodic striation contrast due to Al composition variations, and layer contrasts in the lattice images observed by TEM in selected samples are discussed. The utility of room-temperature PL characterization for AlGaAs/InGaAs/GaAs heteroepitaxial layers is presented. Measures of layer thicknesses and alloy content as well as overall psuedomorphic high-electron-mobility transistor quality and channel sheet charge are derived from the PL signatures.     

Effects of ball-milled graphite in the synthesis of SnO2/graphite as an active material in lithium ion batteries

Nano-sized SnO₂ particles supported on ball-milled graphite were manufactured by the in situ NaBH₄ reduction method and were used as an anode active material in lithium-ion batteries. Their physical and electrochemical characteristics were investigated using various characterization techniques: Raman spectroscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry (CV). From coin half-cell tests, the SnO₂ particles supported on graphite that was ball-milled for 24 hr showed a reversible capacity better than that of commercial graphite and other SnO₂/graphite materials for which the graphite was ball-milled for longer lengths of time.     

Lithium-ion batteries for stationary energy storage

The use of Li-ion batteries for stationary energy storage systems to complement the renewable energy sources such as solar and wind power has recently attracted great interest. Currently available Li-ion battery electrode materials suitable for such stationary applications have been discussed, along with optimum cathode and anode combinations, limitations, and future research directions.     

Neutron diffraction studies of permanent magnetic materials

Neutron diffraction technology as an advanced material research technique has special advantages in studying magnetic materials compared to the conventional techniques such as X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).In this review,the applications of neutron diffraction technology on permanent magnetic materials were briefly reviewed:(1) the determination of the crystal structure and magnetic structure of the typical permanent magnet material,(2) in situ neutron diffraction study of the crystal structure evolution of the permanent magnets,and(3) phase transition in permanent magnetic materials.     

Preparation of tin-oxide nanotubes as anode for Li-ion batteries

The influence of nanostructure on the electrochemical properties of Li-ion battery was investigated. Tin-oxide nanotubes were prepared by combining sol-gel method with polycarbonate template. Scanning electron microscopy and X-ray diffractometry were applied to characterize the obtained material. The electrochemical measurements were conducted on the nanostructured tin-oxides as electrode of Li-ion batteries. The XRD data indicate that the wall of tube is composed of cassiterite crystals of several nanometers. The electrochemical measurements show that the reaction under potential 0.1-0.2 V is possibly related to the tubular structure of the material. It is suggested that the trapping of Li by dangling bonds and defects sites also contributes to the larger irreversible capacity loss in the first discharge.     

Preparation and electrochemical performances of graphite oxide/polypyrrole composites

Graphite oxide/polypyrrole composites (GPys) were prepared by in situ polymerization and reduced by NaBH₄ to prepare reduced graphite oxide/polypyrrole composites (R-GPys). On the basis of the morphological and structural characterization of the composites by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests, the electrochemical performances of the composites were investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance techniques. The experimental results showed that the specific capacitances of the composites before and after reduction (197 and 180 F/g) were highly improved compared with that of pristine graphite oxide (11 F/g) and polypyrrole (112 F/g), respectively. The capacitance retention of about 73% for R-GPys compared with 12% for PPy and 47% for GPys after 1200 cycles indicated the high cycle stability of the R-GPys and its potential as an electrode material for supercapacitor applications.     

Electrochemical performance of carbon nanotube-modified LiFePO_4 cathodes for Li-ion batteries

Carbon nanotubes (CNTs) and acetylene black (AB) were dispersed synchronously or separately between LiFePO4 (LFP) particles as conducting agents during the course of manufacture of LiFePO4 cathodes. The morphology and electrochemical performances of as-prepared LiFePO4 were evaluated by means of transmission electron microscopy (TEM), charge-discharge test, electrochemical impedance spectroscope (EIS) and cyclic voltammetry (CV). CNTs contribute to the interconnection of the isolated LiFePO4 or carbon particles. For the CNTs-modified LiFePO4, it exhibits excellent performance in terms of both specific capacity and cycle life. The initial discharge capacity is 147.9 mA·h/g at 0.2C rate and 134.2 mA·h/g at 1C rate, keeping a capacity retention ratio of 97% after 50 cycles. The results from EIS indicate that the impedance value of the solid electrolyte interface decreases. The cyclic voltammetric peak profiles is more symmetric and spiculate and there are fewer peaks. CNTs are promising conductive additives candidate for high-power Li-ion batteries.     

The TEM characterization of monodispersed particles

In this article, the characterization of internal structures and external surfaces of monodispersed particles by transmission electron microscopy (TEM) is overviewed with typical examples of monodispersed TiO₂ and αFe₂O₃ particles. When monodispersed particles are less than 1 μm in diameter, their internal structure and external surface can be directly analyzed by TEM. On the other hand, particles larger than 1 μm should be sliced by ultramicrotomy to make thin sections for TEM. The complicated internal structure of monodispersed particles, such asαFe₂O₃ particles with a peanut shape, can be clarified through hi-ghresolution electron microscopy, electron diffraction, and energy-dispersive x-ray spectrometer analysis on their sections. Based on the analysis by TEM, the growth mechanism of monodispersed particles such as TiO2 can be understood through the simulation of their growth process.     

热分解法制备RuO2-IrO2/Ta超级电容器薄膜电极材料研究

用溶液涂刷热解法制备了RuO2-IrO2/Ta超级电容器薄膜电极材料。X射线衍射(XRD)、扫描电镜(SEM)对薄膜电极材料的结构和形貌的分析表明制备的电极材料具有纳米尺度和多孔结构。热分析表明(RuO2-IrO2).nH2O/Ta的结晶转化温度约为327℃。在频率为100 Hz时经320℃/30 min处理涂刷5层的热分解法制备的电极在浓度为37%的硫酸溶液中获得最大电容为55mF/143 mm2。