Textured growth of Cu6Sn5 grains formed at a Sn3.5Ag/Cu interface

The growth orientations of Cu₆Sn₅ grains formed at a Sn3.5Ag/polycrystalline Cu interface were investigated. Similar as reported on Cu single crystals, strong textures in Cu₆Sn₅ layers can also form on polycrystalline Cu, but the texture formation mechanisms differ. The texture formation on polycrystalline Cu occurs during the ripening growth and results from the differences in stability of the interfacial grains with various orientations at different temperatures. A reaction temperature of 240 °C causes the Cu₆Sn₅ layer to form [0001] texture in the direction normal to the substrate, and a special morphology of interfacial Cu₆Sn₅ grains can be formed on this layer to reinforce joint properties.     

Growth behavior of Cu6Sn5 grains formed at an Sn3.5Ag/Cu interface

The growth behavior of Cu₆Sn₅ grains formed at an Sn3.5Ag/Cu interface was investigated. During soldering, Cu₆Sn₅ grains formed at the interface, showing a flattened ovoid shape. During solidification, Cu precipitated from molten solder in the form of Cu₆Sn₅, forming faceted surfaces on existing interfacial grains. The interfacial Cu₆Sn₅ morphology was unrelated to its crystal orientation, which was primarily dependent on reaction temperature. A reaction temperature of 240 °C led to an increase in (002) growth and a decrease in (101) growth with time. However, the (002) plane peak was not detected in the interfacial grains formed at a higher reaction temperature (280 °C).     

Effect of high magnetic field on the morphology of (Cu, Ni)6Sn5 at Sn0.3Ni/Cu interface

The effect of high magnetic field on the microstructure of (Cu, Ni)₆Sn₅ intermetallic compound layer in Sn0.3Ni/Cu couples at 250 °C was examined. The applied magnetic field changed the morphology of outer (Cu, Ni)₆Sn₅ crystals on the Sn side from faceted shape to stick shape. The high magnetic field affected the crystal orientations of (Cu, Ni)₆Sn₅ and reduced the Ni content in the outer layer. The morphology evolution of (Cu, Ni)₆Sn₅ is attributed to the content of Ni solute decreased by magnetic field. The effects of high magnetic field on the liquid convection and phase diagram are considered to be responsible for the Ni content.     

Facile synthesis and electrochemical properties of porous SnO2 micro-tubes as anode material for lithium-ion battery

Porous SnO₂ micro-tubes were synthesized by the thermal decomposition of SnC₂O₄ precursor. The morphology of SnC₂O₄ could be preserved after the controlled heat treatment and a lot of mesopores left due to the release of gases. The mesoporous nature with a range of 3-50 nm was characterized by BET method. SEM images showed that the obtained SnO₂ samples were rhombic tube-like with swallow-tailed nozzles. When the porous SnO₂ micro-tubes were used as anode materials for lithium-ion battery, they exhibited high lithium storage capacity and coulomb efficiency. In addition, CV results demonstrated that the formation of Li₂O at high voltage was partially reversible reactions.     

Porous Si/Cu6Sn5/C composite containing native oxides as anode material for lithium-ion batteries

Journal of Materials Science: Materials in Electronics - Porous Si/Cu6Sn5/C composite containing native oxides was prepared via solid-state mechanical milling and wet chemical etching. This...     

Li3SbO4: A new high rate anode material for lithium-ion batteries

Electrochemical properties of Li₃SbO₄ have been investigated as an anode in lithium-ion coin cells. X-ray powder diffraction of the material, synthesized by the conventional solid state technique with thermal treatment at 800 °C in air, confirmed a monoclinic structure with lattice parameters of a = 5.159 Å, b = 6.048 Å, c = 5.144 Å and β = 109°. Electrochemical measurements in 2032 type coin cells show that Li insertion and extraction in this material take place at 0.72 and 1.05 V vs Li/Li⁺ respectively. Although the material shows a low average reversible capacity of 81 mAhg⁻¹ at a current density of 0.05 mAcm⁻² (C/5), an excellent rate performance with nearly 100% Coulombic efficiency has been observed. Continuous cycling up to 200 cycles at current densities of 0.05, 4.0 and 8.0 mAcm⁻² shows that by increasing the current rate from C/5 to 43 C i.e. 215 times, the average reversible capacity decreases only 10%. Thus, the material might be very useful for applications requiring high rate of charge and discharge.     

Mechanical alloying synthesis of carbon nanotubes in the presence of AlFe small clusters

Carbon nanotubes and small metallic particles (1-3 nm) have been obtained using mechanical alloying techniques. High resolution electron microscope (HREM) techniques have been employed for the structural characterization of the small metallic particles and for the carbon multiwalled nanotubes. Theoretical simulations based on molecular dynamics and quantum mechanic calculations have been used to get insights on the experimental structural results.     

Facile preparation of TiO2/C nanocomposites as anode materials for lithium-ion batteries

TiO₂/C nanospheres with diameter of 300–400 nm were synthesized by controlled thermal decomposition of titanium glycolate spheres in inert atmosphere. The effect of the calcination temperature and atmosphere on the structure and composition of the product are investigated. The products obtained by calcination of the precursor in nitrogen at 500°C consist of anatase and rutile nanoparticles, and amorphous carbon that is in situ generated from the organic components of glycolate precursor. When used as anode material for lithium-ion batteries, the as-prepared TiO₂/C nanocomposite delivers a capacity of 166 mAh/g after 250 charge/discharge cycles at a current rate of 0.2 C and give a good rate capability. The native carbon not only improves the local conductivity but also prevents the aggregation and growth of TiO₂ nanoparticles during calcination, allowing efficient electronic conductivity and Li ion diffusion.     

Hydrothermal synthesis and electrochemical properties of alpha-manganese sulfide submicrocrystals as an attractive electrode material for lithium-ion batteries

A convenient hydrothermal synthetic route has been successfully developed to prepare stable rock-salt-type structure α-MnS submicrocrystals under mild conditions. In this synthetic system, hydrated manganese chloride (MnCl₄·4H₂O) was used to supply a highly reactive manganese source, thiourea ((NH₂)₂CS) was used to supply the sulfide source and aqueous hydrazine (N₂H₄·H₂O) was used as both alkaline and reducing agent. The results revealed that the electrochemical performance of the α-MnS submicrocrystals may be associated with the degree of crystallinity and particle size of samples. The initial lithiation capacity of the α-MnS submicrocrystals obtained at 120 °C is 1327 mAh g⁻¹ at 0.7 V versus Li/Li⁺, which exhibited α-MnS submicrocrystals is extremely promising anode material for lithium-ion batteries and has great potential applications in the future.     

Synthesis of anode active material particles for lithium-ion batteries by surface modification via chemical vapor deposition and their electrochemical characteristics

The high capacity and optimal cycle characteristics of silicon render it essential in lithium-ion batteries. We have attempted to realize a composite material by coating individual silicon (Si) particles of μm-order diameter with a silicon oxide film to serve as an active material in the anode of a lithium-ion battery and thus improve its charge-discharge characteristics. The particles were coated using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) process that realized a homogeneously coated silicon oxide film on each Si particle. The film was synthesized using tetraethyl orthosilicate (TEOS) with hydrogen (H₂) gas used as a reducing agent to deoxidize the silicon dioxide. This enabled the control of the silicon oxidation number in the layers produced by adjusting the H₂ flow during the silicon oxide deposition by ICP-CVD. The silicon oxide covering the Si particles included both silicon monoxide and suboxide, which served to improve the charge-discharge characteristics. We succeeded in realizing an active material using Si, which is abundant in nature, for the anode of a lithium-ion battery with highly charged, improved cycle properties.     

The microstructure of η′-Cu6Sn5 and its orientation relationships with Cu in the early stage of growth

The microstructure of η′-Cu₆Sn₅ during the early stage of growth was studied. Sn was electroplated onto thin Cu foil at room temperature and the specimen was annealed at 150 °C for 30 s. The Cu and Sn on the η′-Cu₆Sn₅ surfaces were removed electrolytically and the specimens were analyzed by scanning and transmission electron microscopy. The η′-Cu₆Sn₅ grains on the Cu side were as small as 5 nm but grew rapidly to 0.3 to 0.5 μm on the Sn side.The orientation relationships between η′-Cu₆Sn₅ and Cu were studied by a thin-film technique. Cu was evaporated onto the NaCl (001) and (111) surfaces to form epitaxial Cu thin films and Sn was then evaporated onto the Cu films to form η′-Cu₆Sn₅. Two types of orientation relationships were found, i.e., (1) [204]_η′//[001]_Cu (zone axis), (402?)_η′//(110)_Cu, and (020)_η′//(11?0)_Cu, and (2) [204]_η′//[111]_Cu (zone axis), (402?)_η′//(11?0)_Cu, and (020)_η′//(1?1?2)_Cu. The interfaces were analyzed.     

锂离子电池负极墨水的制备及性能研究

钛酸锂因零应变特性已成为性能优异的锂离子电池负极材料,在锂离子电极负极材料有良好的应用前景,确保后期3D打印出性能良好的微电池棒状电极.选取钛酸锂作为棒状电极的负极材料,与溶剂、增稠剂、分散剂和保湿剂等按一定比例制备打印墨水,随后通过以挤压为基础的3D打印技术打印电极,并在氮气保护下高温烧结获得的棒状电极。本文主要探究了钛酸锂掺杂石墨、钛酸锂质量分数以及烧结温度对棒状电极的性能影响,其次通过打印墨水的流变特性模拟分析来探究墨水黏度对挤压过程中流动速度的影响.结果表明:掺杂10%石墨的钛酸锂棒状电极相比未掺杂石墨的电极,其充放电容量提高了18%,表现出较好的循环性能;当钛酸锂质量分数为59%,打印墨水黏度为26.53 Pa·s,所制备棒状电极的电阻率为221 kΩ·cm,打印墨水具有良好的打印及导电性能;当烧结温度为950℃,棒状电极电阻率较小,为205 kΩ·cm,与基板有良好的附着力,膜层表面平整、致密且有许多孔洞,有助于电解液的渗透.对打印墨水的黏度进行模拟分析可知,随黏度的增减而使墨水流动速度变化明显.     

Polycrystalline SnO2 nanowires coated with amorphous carbon nanotube as anode material for lithium ion batteries

One-dimensional (1D) SnO₂ nanowires, coated by in situ formed amorphous carbon nanotubes (a-CNTs) with a mean diameter of ca. 60 nm, were synthesized by annealing the anodic alumina oxide (AAO) filled with a sol of SnO₂. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns revealed that the prepared SnO₂ nanowires exist in polycrystalline rutile structure. The coating of carbon nanotubes has some defects on the wall after the internal SnO₂ nanoparticles were removed. The 1D SnO₂ nanowires present a reversible capacity of 441 mAh/g and an excellent cycling performance as an anode material for lithium ion batteries. This suggests that 1D nanostructured materials have great promise for practical application.     

Synthesis and electrochemical properties of nanostructured LiMn2O4 for lithium-ion batteries

Spinel LiMn₂O₄ crystal with the grain sizes of about 15 nm is firstly synthesized by hydrothermal route at 180 °C using MnO₂ as a precursor. The LiMn₂O₄ powders synthesized by hydrothermal technique and sol-gel reaction were investigated by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The LiMn₂O₄ samples were used as cathode materials for lithium-ion battery, whose electrochemical properties were investigated. The results show that the sample obtained by hydrothermal route has higher capacity than that prepared by sol-gel method.     

Interfacial reaction during fabricating of full Cu3Sn joints in microelectronic packaging

Two copper substrates electroplated with Sn, both consisted of Cu/Sn?+?Sn/Cu structures, but they were bonded over different times in order to investigate the interfacial reaction. The growth morphologies of Cu₆Sn₅ and Cu₃Sn were analysed, respectively. The growth mechanisms for Cu₆Sn₅ and Cu₃Sn were investigated. The results show that the growth of Cu₆Sn₅ is primarily controlled by grain boundary-diffusion. However, the growth Cu₃Sn is controlled by the reaction of Cu-Cu₆Sn₅ at the beginning of the reaction, and then controlled by volume-diffusion as the thickness of the Cu₃Sn layer increases.     

Biotemplated synthesis of three-dimensional porous MnO/C-N nanocomposites from renewable rapeseed pollen: An anode material for lithium-ion batteries

Lithium-ion batteries (LIBs) are currently recognized as one of the most popular power sources available. To construct advanced LIBs exhibiting long-term endurance, great attention has been paid to enhancing their poor cycle stabilities. As the performance of LIBs is dependent on the electrode materials employed, the most promising approach to improve their life span is the design of novel electrode materials. We herein describe the rational design of a three-dimensional (3D) porous MnO/C-N nanoarchitecture as an anode material for long cycle life LIBs based on their preparation from inexpensive, renewable, and abundant rapeseed pollen (R-pollen) via a facile immersion-annealing route. Remarkably, the as-prepared MnO/C-N with its optimized 3D nanostructure exhibited a high specific capacity (756.5 mAh·g^?1 at a rate of 100 mA·g^?1), long life span (specific discharge capacity of 513.0 mAh·g^?1, ~95.16% of the initial reversible capacity, after 400 cycles at 300 mA·g^?1), and good rate capability. This material therefore represents a promising alternative candidate for the high-performance anode of next-generation LIBs.

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Synthesis and electrochemical properties of Co3O4 nanofibers as anode materials for lithium-ion batteries

Co₃O₄ nanofibers as anode materials for lithium-ion batteries were prepared from sol precursors by using electrospinning. The morphology, structure and electrochemical properties of Co₃O₄ nanofibers were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and charge-discharge experiments. The results show that Co₃O₄ nanofibers possessed typical spinel structure with average diameter of 200 nm. The initial capacity of Co₃O₄ nanofibers was 1336 mAhg^− 1 and the capacity reached 604 mAhg^− 1 up to 40 cycles. It was suggested that the high reversible capacity could be ascribed to the high surface area offered by the nanofibers' structure.     

Effects of MoS2 doping on the electrochemical performance of FeF3 cathode materials for lithium-ion batteries

Orthorhombic structure FeF₃ was synthesized by a liquid-phase method. The FeF₃/MoS₂ for the application of cathode material of lithium-ion battery was prepared through mechanical milling with molybdenum bisulfide. The structure and morphology of the FeF₃/MoS₂ were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of FeF₃/MoS₂ was studied by charge/discharge, cyclic voltammetry and electrochemical impedance spectra measurements. The results show that the prepared FeF₃/MoS₂ was typical orthorhombic structure, uniform surface morphology, better particle-size distribution and excellent electrochemical performances. The initial discharge capacity of FeF₃/MoS₂ was 169.6 mAh·g^− 1 in the voltage range of 2.0-4.5 V, at room temperature and 0.1 C charge-discharge rate. After 30 cycles, the capacity retention is still 83.1%.     

Superconducting YBa2Cu3O7-δ thick films on Ba2RETaO6 (RE = Pr5 Nd, Eu, and Dy) substrates

Thick films of YBa₂Cu₃O_7-δ fabricated on polycrystalline Ba₂RETaO₆ (where RE = Pr, Nd. Eu, and Dy) substrates by dip-coating and partial melting techniques are textured and oaxis oriented, showing predominantly (00/) orientation. All the thick films show a superconducting zero resistance transition of 90 K. SEM studies clearly indicate platelike and needlelike grain growth over a wide area of the thick films. The values of the critical current density for these thick films are ∼10⁴ A/cm² at 77 K as determined by the nonresonant R.F. absorption method. Various processing conditions that affect the critical current density of thick films are also discussed.     

Synthesis and electrochemical properties of Nb-doped Li3V2(PO4)3/C cathode materials for lithium-ion batteries

Li₃V_2−xNb_x(PO₄)₃/C cathode materials were synthesized by a sol-gel method. X-ray diffraction patterns demonstrated that the appropriate addition of Nb did not destroy the lattice structure of Li₃V₂(PO₄)₃, and enlarged the unit cell volume, which could provide more space for lithium intercalation/de-intercalation. Transmission electron microscopy and energy dispersive X-ray spectroscopy analysis illustrated that Nb could not only be doped into the crystal lattice, but also form an amorphous (Nb, C, V, P and O) layer around the particles. As the cathode materials of Li-ion batteries, Li₃V_2−xNb_x(PO₄)₃/C (x ≤ 0.15) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5C, the initial discharge capacity of Li₃V_1.85Nb_0.15(PO₄)₃/C was 162.4 mAh/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Li₃V_2−xNb_x(PO₄)₃/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Nb doping in Li₃V₂(PO₄)₃ system by enhancing structural stability and electrical conductivity.