一维纳米材料在锂离子电池中的研究进展

主要评述了近年来纳米棒、纳米管、纳米带、纳米纤维等一维纳米材料在锂离子电池正负极、隔膜及全固态电池固态电解质中的应用。一维纳米材料的比表面积大、孔隙率高,能为锂离子提供更短的嵌入脱出路径,还能有效缓解电池工作时产生的体积效应,从而大大提高锂离子电池的性能。介绍了不同方法制备的一维纳米材料在锂离子电池中对电化学性能的优化及提升,并重点介绍了具有产业化前景的静电纺丝法制备用于锂离子电池的一维材料近年的发展;展示了一维纳米材料在锂离子电池中的研究进展,并展望了其发展方向。     

LiNi0.8 Co0.15 A10.05 O2正极材料的表面包覆改性研究

LiNi_0.8 Co_0.15 A1_0.05 O₂正极材料具有容量高、价格低等优点,被认为是最具发展前景的锂离子电池正极材料之一.但LiNi 0.8Co 0.15A1 0.05O₂材料本身存在充放电过程中容量衰减较快、倍率性能差和储存性能差等缺陷,影响了其进一步发展.本文以 LiNi 0.8Co 0.15A1 0.05O₂为研究对象,采用共沉淀法制备氢氧化物前驱体,在前驱体的表面包覆一层Ni 1/3Co 1/3 Mn 1/3(OH)₂,制备成具有核壳结构的正极材料.通过XRD、SEM、EDX、电化学测试等分析手段,系统地研究了其结构、形貌以及电化学性能.分析表明:包覆改性后,LiNi 0.8Co 0.15Al 0.05O₂正极材料在0.1、0.2、0.5、1 C倍率下,材料的首次充放电比容量分别为167.6,160.1,0.4,8.5 mAhg -1.由0.1到1 C,包覆改性前后的正极材料的放电比容量衰减量由34.7 mAhg -1降为29.1 mAhg -1,容量衰减百分比由22.1%降低到17.4%.综合性能分析认为,包覆改性后电化学性能有一定的改善.     

Nanostructured Li3V2(PO4)3 Cathodes

To further increase the energy and power densities of lithium‐ion batteries (LIBs), monoclinic Li₃V₂(PO₄)₃ attracts much attention. However, the intrinsic low electrical conductivity (2.4 × 10^?7 S cm^?1) and sluggish kinetics become major drawbacks that keep Li₃V₂(PO₄)₃ away from meeting its full potential in high rate performance. Recently, significant breakthroughs in electrochemical performance (e.g., rate capability and cycling stability) have been achieved by utilizing advanced nanotechnologies. The nanostructured Li₃V₂(PO₄)₃ hybrid cathodes not only improve the electrical conductivity, but also provide high electrode/electrolyte contact interfaces, favorable electron and Li⁺ transport properties, and good accommodation of strain upon Li⁺ insertion/extraction. In this Review, light is shed on recent developments in the application of 0D (nanoparticles), 1D (nanowires and nanobelts), 2D (nanoplates and nanosheets), and 3D (nanospheres) Li₃V₂(PO₄)₃ for high‐performance LIBs, especially highlighting their synthetic strategies and promising electrochemical properties. Finally, the future prospects of nanostructured Li₃V₂(PO₄)₃ cathodes are discussed.     

喷雾干燥法制备富锂正极材料及其电化学性能

用喷雾干燥法制备Li_1.2Mn_0.54Ni_0.13Co_0.13O₂富锂正极材料并表征其结构、形貌以及电化学性能,研究了烧结温度对材料电化学性能的影响。结果表明：这种正极材料具有良好的层状结构,一次颗粒粒径为100 nm左右且分布均匀,样品的首次放电比容量为220.2 mAh/g,库伦效率为72.5%,18个循环后容量保持率为96.8%。电化学阻抗和循环伏安特性的测试结果表明,这种正极材料具有良好的电化学性能。     

An Approach to Synthesize Thick α- and γ-Al2O3 Coatings by High-Speed Physical Vapor Deposition

Crystalline α- and γ-Al₂O₃ exhibit in many applications high wear resistance, chemical resistance, and hot hardness, making them interesting materials for production engineering. To synthesize α-Al₂O₃ with high coating thickness of s ≥ 10 μm, chemical vapor deposition at temperatures T > 1000 °C is well established. However, there are almost no studies dealing with the synthesis of thick α-Al₂O₃ by physical vapor deposition (PVD) at high temperatures T > 700 °C. High-temperature deposition of thick coatings can be realized by means of the dense hollow cathode plasma, combined with the transport function of the plasma gas in high-speed (HS) PVD. Herein, crystalline α- and γ-Al₂O₃ films are deposited on cemented carbides at substrate temperatures T _s ≈ 570 °C and T _s ≈ 780 °C by HS-PVD. These coatings exhibit a thickness up to s = 20 μm. Moreover, phase analysis presents α-phases in coatings synthesized at substrate temperature of T _s ≈ 780 °C with significant higher hardness than films by T _s ≈ 570 °C. These release the potential of HS-PVD to synthesize α-Al₂O₃ coatings with high thickness. Thereby, a higher thickness of these coatings is beneficial for the wear protection of turning and die casting tools.     

Synthesis of solid NMC622 particles by spray drying,post-annealing and lithiation

Layered lithium-nickel-manganese-cobalt oxide (NMC) cathode materials are widely used in Li-ion batteries that require high energy densities, such as those used in plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). Here we studied the synthesis of NMC622 particles by spray pyrolysis, which is a simple one-step process for production of spherical particles. However, synthesising NMC powder using spray pyrolysis has a tendency to produce hollow NMC particles. To gain insight into the mechanism behind the formation of the hollow particles, one dimensional numerical simulation of the physical and chemical phenomena taking place during spray drying were carried out. The effects of several process parameters, including drying air temperature, drying air mass flow rate, and liquid feed mass flow rate, on the evaporation and particle formation process were studied. The increased evaporation rate at higher temperatures was found to result in crust formation on the droplet surface during the particle formation, and thus, in lower solid volume fractions in the dried particles. However, by optimizing the process parameters production of solid NMC622 sulphate particles by spray drying was achieved. The produced NMC622 sulphate particles were then oxidised and lithiated in air at 850 °C via the conventional thermal treatment process. Four lithium precursors, LiOH, Li₂CO₃, Li₂SO₄ and LiNO_3, were tested for the lithiation of the oxidized NMC particles. The degree of lithiation and the crystalline phase of the powders were determined using ICP-OES and XRD, respectively.     

Discharge properties and chemical stability of SrZrO films

Abstract— MgO thin film is currently used as a surface protective layer for dielectric materials because MgO has a high resistance during ion sputtering and exhibits effective secondary electron emission. The secondary‐electron‐emission coefficient γ of MgO is high for Ne ions; however, it is low for Xe ions. The Xe content of the discharge gas of PDPs needs to be raised in order to increase the luminous efficiency. Thus, the development of high‐γ materials replacing MgO is required. The discharge properties and chemical surface stability of SrO containing Zr (SrZrO) as the candidate high‐γ protective layer for noble PDPs have been characterized. SrZrO films have superior chemical stability, especially the resistance to carbonation because of the existence of a few adsorption sites due to their amorphous structure. The firing voltage is 60 V lower than that of MgO films for a discharge gas of Ne/Xe = 85/15 at 60 kPa.     

Modeling of axis-symmetric steam plasma flow in a non-transferred torch

This paper discusses the numerical modeling of steam plasma in a DC non-transferred torch equipped with well-type cathode, where the non-trivial azimuthal velocity component and turbulent effect are both taken into account. In order to investigate the complicated flow characteristics of thermal plasma due to the interaction between steam and electric arc, the flow filed inside the plasma torch is modeled by the magnetic–hydrodynamic (MHD) equations. The governing equations are then solved numerically using a non-staggered finite volume discretization based on Cartesian grid system. The anode location and maximum current density at cathode are fixed by the corresponding experimental measurement at a given flow rate. The predicted result suggests that the steam plasma can be accelerated to a mean velocity of 1500 m/s at torch outlet with the mass flow rate of 5 g/s and the system current of 180 A. A strong vortex flow structure is found inside the torch due to the introduction of azimuthal velocity at the gas inlet, which should help to stabilize the rotating arc during the torch operation.     

CRT and LCD monitor and process materials evaluated for environmental improvement

Decision rules have been developed and applied to the bills of materials of a color cathode‐ray tube (CRT) and a liquid‐crystal‐display (LCD) desktop monitor to determine which product and process materials will be evaluated in an environmental life‐cycle assessment. Materials of significant mass, of technological importance, and of potential environmental impact are targeted. The list of materials identified are those for which life‐cycle inventory data will be obtained for the materials extraction and materials processing life‐cycle stages of a CRT and an LCD. Additionally, materials identified will also be used to represent life‐cycle impact in terms of resource consumption, as well as surrogates for occupational health impacts.