Improvement of electrochemical performance of Si thin film anode by rare-earth La PIII technique

Si thin film is considered a good candidate for rechargeable Li-ion thin film battery anode material because it possesses large lithium adsorption capacity, good thermal and chemical stability. However, the fast capacity decay upon charge-discharge cycling has hindered the application of Si thin films. In this investigation, Si thin films were sputtered on Cu foils and characterized. One of the explanations for the bad cycling characteristics is the poor adhesion between the Si film and the Cu substrate. Some Cu foils were treated by Plasma Immersion Ion Implantation (PIII) method using rare-earth La element to improve the adhesion strength between the Si thin films and the Cu substrate in order to enhance the cycling performance. Electrochemical analysis revealed that La PIII surface treatment on the Cu foil substrate was effective in strengthening the interface adhesion between the Si thin films and the Cu substrates. Subsequently, the electrochemical performance of the Si thin film anodes was improved.     

Failure mechanism of bulk silicon anode electrodes for lithium-ion batteries

Silicon has been investigated extensively as a promising anode material for rechargeable lithium-ion batteries. Understanding the failure mechanism of silicon-based anode electrodes for lithium-ion batteries is essential to solve the problem of low coulombic efficiency and capacity fading on cycling and also to further commercialize this very new energetic material in cells. To reach this goal, the structure changes of bulk silicon particles and electrode after cycling were studied using ex-situ scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The SEM images indicated that the microstructural changes of the bulk silicon particles during cycling led to a layer rupture of the electrode and then the breakdown of the conductive network and the failure of the electrode. The result contributes to the basic understanding of the failure mechanism of a bulk silicon anode electrode for lithium-ion batteries.     

Self-assembled sandwich-like NiO film and its application for Li-ion batteries

NiO film with sandwich-like morphology is fabricated on nickel foam by a simple ammonia-evaporation process. Ammonia plays a major role in controlling the final geometry during this template- and surfactant-free synthesis. The obtained NiO film is constructed by regular triangular prisms with side length of 500 nm. Each triangular prism is self-assembled by single crystalline platelets. As an anode for lithium ion battery, this NiO film electrode exhibits high discharge capacity and excellent cycling performance. The reversible capacity of the sandwich-like NiO film sustains 400 mAh g⁻¹ even after 50 cycles at 2 C, much higher than that of the dense NiO film prepared by eletrodeposition (198 mAh g⁻¹). The high rate capability and reversibility of this NiO film can be attributed to its unique sandwich-like architecture.     

Controlled synthesis of uniform ultrafine CuO nanowires as anode material for lithium-ion batteries

A simple solution route is used to synthesize ultrafine Cu(OH)₂ nanowires by restraining the morphology transformation of early formed 1D nanostructure. The obtained ultrafine nanowires can be well preserved at a low temperature structure transformation in solid state. As anode material for lithium-ion batteries, the ultrafine CuO nanowires exhibit high reversible capacity, superior cycling performance and improved rate capability. The improved electrochemical properties of CuO nanowires are ascribed to their ultrafine size which lead to the reduced over-potential, extra reversible reactions at low potentials and improved interface performance between the electrode and electrolyte.     

Constitution, microstructure, and battery performance of magnetron sputtered Li-Co-O thin film cathodes for lithium-ion batteries as a function of the working gas pressure

Li-Co-O thin film cathodes have been deposited onto Si and stainless steel substrates by RF magnetron sputtering from a ceramic LiCoO₂ target at various working gas pressures from 0.15 to 25 Pa. Composition, crystal structure and thin film morphology were examined and properties such as intrinsic stress, conductivity and film density were determined. As-deposited films at 0.15 Pa as well as in the range between 5 Pa and 10 Pa working gas pressure showed a nanocrystalline metastable rocksalt structure with disordered cation arrangement and were nearly stoichiometric. To induce a cation ordering the films were annealed in a furnace at temperatures between 100 and 600 °C for 3 h in argon/oxygen atmosphere (Ar:O₂ = 4.5:5) of 10 Pa. This cation ordering process was observed by XRD and Raman spectroscopy. For the films deposited at 10 Pa gas pressure an annealing temperature of 600 °C leads to the formation of the high temperature phase HT-LiCoO₂ with a layered structure. The Raman spectrum of the films deposited at 0.15 Pa and annealed at 400 °C indicates the formation of the low temperature phase LT-LiCoO₂ with a cubic spinel-related structure, which is assumed to be stabilized due to high compressive stress in the film. The electrochemical characterisation of annealed thin film cathodes revealed that the discharge capacity strongly depends on the crystal structure. Thin Li-Co-O films with a perfect layered HT-LiCoO₂ structure showed the highest discharge capacities.     

Mechanical and magnetic properties of copper dispersed ferrum films under heat treatment

The Cu-containing steels are widely used for nuclear pressure vessel materials because of their good performance under high pressure and high temperature. In this article, magnetron sputtering was used to prepare iron films with various Cu contents. The samples were annealed at temperature range of 300–500 °C, and the structural,mechanical, and magnetic properties were studied. The results show that both hardness and modulus change along with copper content and annealing temperature. The change in coercivity after annealing is similar to that of hardness. The crystal grain growth in matrix ferrum and Cu precipitation during annealing influences both the mechanical and magnetic properties.     

Synthesis and electrochemical properties of novel silicon-based composite anode for lithium-ion batteries

A novel nano-Si dispersed composite containing lithium-rich component (lithium orthosilicate, etc.) has been prepared and investigated as a potential anode material for lithium-ion batteries. The composite was synthesized by mechanochemical reduction of SiO using lithium metal as reducing agent and graphite as grinding aid, further vacuum heat-treatment was performed to improve interfacial stability between different components. Compared with pure SiO and intrinsic silicon electrodes, the as-obtained composite electrode exhibited greatly improved cycling performance with a remarkable value of the first coulombic efficiency. The superior electrochemical properties were attributed to small absolute volume changes of nano-silicon particles, highly distribution of silicon phase and better buffering action of lithium-containing components.     

Influence of Ti^4＋ doping on electrochemical properties of LiFePO4/C cathode material for lithium-ion batteries

To improve the performance of LiFePO4, single phase Li1-4xTixFePO4/C (x=0, 0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy observations(SEM), charge/discharge test, carbon analysis and electrochemical impedance spectroscopy(EIS). The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti~(4+) does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti~(4+) (molar fraction) has good electrochemical performance delivering about an initial specific capacity of 146.7 mA·h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti~(4+).     

Li4Ti5O12/TiN复合材料的制备及电化学性能

以尿素为氮源,采用高温热处理方法在Li4Ti5O12表面自生长一层纳米尺寸厚度的TiN导电包覆膜。利用DSC-TG、Raman、TEM、FT-IR、XRD及恒流充放电等测试手段,研究热处理工艺对材料结构、形貌及电化学性能的影响。结果表明:使用适中的尿素原料含量可以获得均匀连续、厚度适中的TiN导电膜,较高的热处理温度有利于促进TiN的生成,而较短的热处理时间可以保持材料物相的纯净和较高结晶度。在尿素含量10%(质量分数)、热处理温度800℃、热处理时间20 min的工艺条件下,所制备的复合材料的容量和倍率性能最优,0.2C和3C初始放电比容量分别达到162.4和130.2 mA.h/g。     

锂离子电池极材料钽掺杂钛酸锂的制备及电化学性能

通过固相合成制备了钽掺杂材料Li4Ti4.95Ta0.05O12。通过XRD和SEM来表征Li4Ti4.95Ta0.05O12的结构和形貌。钽掺杂并没有改变本体材料的结构和形貌,而且显著提高了材料的循环性能和倍率性能。Li4Ti4.95Ta0.05O12在10C和30C倍率时的放电容量分别是116.1mA.h/g和91.0mA.h/g。Ta掺杂取代了Li4Ti5O12中的Ti的位置,产生了Ti4＋/Ti3＋混合价态,从而提高了钛酸锂的电导率。故具有优异的高倍率性能,是一种优异的锂离子电池负极材料。.     

Preparation and properties of tungsten-doped indium oxide thin films

Tungsten-doped indium oxide (IWO) thin films were deposited on glass substrate by DC reactive magnetron sputtering. The effects of sputtering power and growth temperature on the structure, surface morphology, optical and electrical properties of IWO thin films were investigated. The thickness and surface morphology of the films are both closely dependent on the sputtering power and the substrate temperature. The transparency of the films decreases with the increase of the sputtering power but is not seriously influenced by substrate temperature. All the IWO thin film samples have high transmittance in near-infrared spectral range. With either the sputtering power or the growth temperature increases, the resistivity of the film decreases at the beginning and increases after the optimum parameters. The as-deposited IWO films with minimum resistivity of 6. 4× 10-4 Ω·cm were obtained at a growth temperature of 225 ℃ and sputtering power of 40 W, with carrier mobility of 33. 0 cm2· V-1·s-1 and carrier concentration of 2. 8× 1020 cm-3 and the average transmittance of about 81％ in near-infrared region and about 87％ in visible region.     

Structural characteristics and optical properties of plasma assisted reactive magnetron sputtered dielectric thin films for planar waveguiding applications

Thin films of aluminum oxide (Al₂O₃), tantalum pentoxide (Ta₂O₅), titanium oxide (TiO₂), yttrium oxide (Y₂O₃) and zirconium oxide (ZrO₂) were deposited by plasma assisted reactive dual magnetron sputtering to determine their suitability as a host for a rare earth doped planar waveguide upconversion laser. The effect of deposition parameters such as cathode, plasma power and oxygen gas flows were studied and the operational working points were determined. Both power and lambda control were used to optimize the optical quality of each material. By using lambda control feedback system, the magnetron power fluctuates to sustain a fixed oxygen flow in the target area reducing the compound layer growth on the material and maintaining a healthy deposition rate. The optical properties, structure and crystalline phase of each film were found to be dependent on the process parameters. X-ray diffraction (XRD) analysis revealed that the thin films varied from amorphous to highly crystalline depending on the deposition conditions. X-ray photoelectron spectroscopy (XPS) was utilized for surface compositional analysis revealing that films had varying stoichiometric ratios which are controlled for each material by the deposition parameters chosen. The waveguide loss for the thin film layers was investigated and Ta₂O₅ was shown to have a slab waveguide loss of ~ 1 dB/cm at both visible and infra-red wavelengths making it ideal for planar waveguide and laser applications. TiO₂, Y₂O₃ and ZrO₂ were found to deposit in a highly crystalline phase. Waveguiding in the TiO₂ layers was not possible at 633 nm or in the infrared region. The Y₂O₃ samples gave low loss (2–4 dB/cm) at the 1.3 and 1.5 μm wavelengths but no waveguiding at 633 nm or 833 nm was possible. Atomic force microscopy showed rough surface topography for TiO₂, Y₂O₃ and ZrO₂ akin to their crystalline growth with the SEM images confirming the regular crystalline columnar structure for the case of Y₂O₃ and ZrO₂.     

Nd-Fe-B薄膜的磁控溅射法制备与组织结构

对直流磁控溅射法制备Nd-Fe-B薄膜工艺进行了研究.在不同的溅射功率、溅射气压、溅射时间等条件下制备薄膜,并对薄膜进行了AFM、XRD分析.结果表明,Nd-Fe-B薄膜的沉积速率、表面形貌及相结构与溅射功率、溅射气压、溅射时间密切相关.薄膜的沉积速率随磁控溅射功率的增加而增加,薄膜表面晶粒尺寸和表面粗糙度随溅射功率增加而增大.沉积速率随溅射气压的升高先增大后减小.低功率溅射时,薄膜中出现α-Fe、Nd2Fe14B相相对较少,随溅射功率增加,α-Fe相消失,Nd2Fe14B相增多.综合考虑各种因素,最佳溅射功率为100～130 W.     

碳化钙骨架碳负极材料的制备及电化学性能

以碳化钙为原料、新鲜氯气为刻蚀剂,在400～700℃范围内制备碳化钙骨架碳作为锂离子电池新型负极材料.用X射线衍射(XRD)、扫描电镜(SEM)、氮气吸附实验、恒流充放电、交流阻抗(EIS)等对碳化钙骨架负极材料进行表征及电化学性能测试,并探讨制备温度对碳化钙骨架碳结构和电化学性能的影响.结果表明:所有温度下制备的碳化钙骨架碳均为无定形碳材料,但随着制备温度的升高,材料出现部分石墨化倾向;600℃制备的碳化钙骨架碳具有良好的电化学性能,在0.1 C充放电时,首次放电比容量为890.9 mA·h/g,可逆容量为335.4mA·h/g,循环30次后的可逆容量为266.8 mA·h/g.     

多孔泡沫铜支撑锡薄膜阳极材料的制备及性能

以三维多孔泡沫铜为基底,采用化学镀的方法制备锂离子电池薄膜Sn负极材料.利用扫描电镜、X射线衍射分析以及恒电流充放电测试等手段研究不同厚度薄膜Sn电极的形态、结构和电化学行为.结果表明:化学镀工艺制备的Sn电极表面的大量微孔和岛状突起不仅增大电极的表面积,而且显著缓解电极在充放电过程中体积的变化;其中镀层较薄的样品C薄膜Sn电极的初始充电(脱锂)容量为660.6 mA·h/g,经100次循环后,容量保持在299.5 mA·h/g,具有较好的循环性能.     

Multi-functional ECR plasma sputtering system for preparing amorphous carbon and Al–O–Si films

A design of cylindrical double-target source with shutter slider which can continuously change the target area ratio was applied to the divergent and mirror-confinement Electron Cyclotron Resonance (ECR) plasma sputtering system in the present study. The deposition process feasibility of several types of films (single-layer of pure and composite film as well as multi-layer film) can be realized by using this multi-functional system. The highly concerned amorphous carbon films were prepared with the Divergent ECR (DECR) and Mirror-Confinement ECR (MCECR) plasma sputtering systems. The tribological properties were compared, which both showed a normally friction coefficient around 0.15. Through adding substrate heating during film preparation, the tribological properties of DECR carbon films were improved with an obvious decreasing of friction coefficient to 0.05 and a much longer wear lifetime. The designed double-target source with shutter slider was used to prepare Al–O–Si films, by which the target area ratio of silicon to aluminum was changed from 0.5 to 2. A composite structure of Al–O–Si film with high transmittance up to 89% at 193 nm wavelength was obtained with the multi-functional ECR plasma sputtering system.     

A comparison between the corrosion behavior of nanostructured copper thin films deposited on oxidized silicon and copper sheet in alkaline media

Copper thin films were deposited on oxidized silicon at a substrate temperature of 70 °C and 150 °C using EB-PVD technique. The morphology and crystal orientation of the deposited film were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Corrosion behavior of films was studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, immersion test, and cathodic chronopotentiography. Additionally, the crystalline structure of corroded samples immediately after polarization was examined by XRD. Corrosion current density for copper deposits was higher than copper sheet by polarization tests, while the data obtained by the EIS technique emphasized higher corrosion current density for copper sheet. However there was a conflict between polarization and EIS data, the other results obtained by immersion and cathodic chronopotentiography tests proved that the corrosion resistance of copper deposits was higher than copper sheet in the same alkaline media, which can be attributed to chemical composition and higher thickness of the passive layer formed on copper deposits. On the other hand, breakdown potential (E_bp) for copper sheet was about 0.3 V_SCE, while a distinct E_bp was not found for copper deposits. This was a sign of higher stability of the passive layer formed on copper deposits. The XRD patterns of samples immediately after polarization showed a higher content of Cu(OH)₂ on copper deposits in comparison with copper sheet. The stable morphology formed on the surface of copper after polarization was monoclinic CuO, which is assumed to have a significant effect on copper protection in alkaline media. This morphology was more compact on copper deposits in comparison with copper sheet. This was due to higher ability of deposits to react with hydroxyl ions.     

Growth of conformal copper films on TaN by electrochemical deposition for ULSI interconnects

Seedless copper electrochemical deposition (ECD) becomes a potential interconnect technology while device dimension keeps shrinking in ULSI design. In seedless copper ECD on TaN, which is a widely used diffusion barrier, uniform growth of copper film on TaN is hindered because a robust native Ta₂O₅ exists on TaN surface. Complete removal of the native Ta₂O₅ can be attained using a saturated KOH solution that is assisted by an anodic voltage. This then permits that copper film grows on the pretreated TaN surface in a copper-citrate (Cu-Cit) complex electrolyte. Its growing morphology and deposition rate are dependent on the etching depth of as-deposited TaN in the KOH solution. Even for a very short etching time of 0.8 s, thin Ta₂O₅ is totally etched off and the activated TaN surface appears. Thin and conformal copper films grown in a layer-by-layer mode on the TaN surface are proper to function as an ECD seed or metal lines for ULSI interconnects.     

锂离子电池微孔Sn-Co-C负极的制备及其性能

采用模板-电沉积法制备锂离子电池Sn-Co-C微孔负极。首先,采用聚合法制备PS球乳液。然后,再以柠檬酸、EDTA为络合剂,CoCl2、SnCl4为主盐,添加甲酸和PS球乳液的电解液中,电沉积制备Sn-Co-C微孔复合电极材料。随后采用EDS、XRD和SEM分析其元素成分、晶体结构和表面形貌。最后采用恒流充放电和交流阻抗测试其电化学性能。结果表明,电极表面的微孔可以缓解锂电池充放电过程中产生的体积变化所导致的活性物质脱落,提高循环性能和寿命。Sn-Co-C负极组成的电池首次充放电比容量分别为705.4和1105 mA.h.g-1,循环126次后充放电比容量分别为393.3和403.2 mA.h.g-1。     

Synthesis and electrochemical performances of spherical LiFePO4 cathode materials for Li-ion batteries

Spherical LiFePO4 and LiFePO4/C composite powders for lithium ion batteries were synthesized by a novel processing route of co-precipitation and subsequent calcinations in a nitrogen and hydrogen atmosphere. The precursors of LiFePO4, LiFePO4/C composite and the resultant products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and the electrochemical performances were investigated by galvanostatic charge and discharge tests. The precursors composed of amorphous Fe3(PO4)2·xH2O and crystalline Li3PO4 obtained in the co-precipitation processing have a sphere-like morphology. The spherical LiFePO4 derived from the calcinations of the precursor at 700 ℃ for 10 h in a reduction atmosphere shows a discharge capacity of 119 mAh·g -1 at the C/10 rate, while the LiFePO4/C composite with 10wt.% carbon addition exhibits a discharge capacity of 140 mAh·g -1.The electrochemical performances indicate that the LiFePO4/C composite has a higher specific capacity and a more stable cycling performance than the bare olivine LiFePO4 due to the carbon addition enhancing the electronic conductivity.