二元锰基复合金属氧化物锂离子电池负极材料的研究进展

在现有的各类锂离子电池(LIBs)负极材料中,二元锰基过渡金属氧化物材料(AMn_2O_4,A=Zn,Co,Ni等)已经被证明是较为理想的锂离子负极材料,以ZnMn_2O_4、CoMn_2O_4、NiMn_2O_4 3种负极材料为例,介绍了AMn_2O_4负极材料的储能机理、合成方法、以及结构-储锂性能之间构效关系,并提出了各材料目前存在的问题和相应的解决方案,以促进其在锂离子电池市场上的进一步推广和应用。     

碳源对Fe2O3储锂性能的影响

过渡金属氧化物具有高的理论比容量,作为锂离子电池负极材料具有潜在的应用前景.金属氧化物Fe2O3的理论容量高,成本低,然而其电子传导性较差.为加快Fe2O3的电子传导,以不同形式的碳为碳源,制备了 Fe2O3/碳复合材料,并研究了其电化学性能.结果表明:Fe2O3/碳纳米管(CNTs)复合材料中的碳含量最高,为20.4...     

锂离子电池纳米Co3O4-PTFE复合负极材料的循环性能

采用在加温的水溶液中电沉积然后烧结方法制备锂离子电池的纳米Co3O4-PTFE复合负极材料.XRD分析表明,电沉积的物质在245℃真空热处理后转变为Co3O4-PTFE.SEM观察可以发现,Co3O4-PTFE中的Co3O4呈现蜂窝结构,其厚度为30～50nm;PTFE则形成交联的柱状体吸附在片状Co3O4两侧,其直径为50～100nm.这种纳米Co3O4-PTFE复合沉积层具有结构稳定、抗粉化的特点.充放电实验结果表明,Co3O4掺杂PTFE可明显提高负极材料的可逆比容量和循环性能,其首次放锂比容量为920.1mAh·g-1,20次循环后放锂比容量为685.6mAh·g-1;而没有掺杂PTFE的试样对应的数据分别为865.1mAh·g-1和180.4mAh·g-1.     

SnO2/Ni复合锂离子电池负极材料的制备及其电化学性能

采用机械球磨法将纳米SnO2和Ni粉末复合,作为锂离子电池负极材料。采用XRD、SEM、TEM和EDS分析球磨过程中材料结构和形貌的变化。对SnO2/Ni复合负极材料的首次库仑效率、循环稳定性及CV曲线等进行测试分析。结果表明:将复合粉末球磨适当时间后,SnO2和Ni可形成结合充分、颗粒尺寸细小、分布均匀的复合材料;SnO2和Ni的复合可有效提高SnO2的首次库仑效率和循环稳定性;SnO2/Ni复合负极材料的循环稳定性随球磨时间的延长而增加,但电极的首次库仑效率随球磨时间的延长呈先增加后下降的趋势;Ni的引入有效减小了SnO2在首次充放电循环过程中生成Li2O的不可逆反应程度,并在随后的循环过程中部分以Li-O化合物的形式进行可逆反应。     

锂钛氧嵌锂负极材料的研究进展

目前锂离子电池主要受制于安全性能、大功率性能和制造成本,新型高性能锂钛氧基负极材料有望解决这些问题,在动力型和储能型锂离子电池中获得应用。本文对Li4Ti5O12、Li Ti2O4、Li2Ti3O7、Li2Ti6O13等系列锂钛氧嵌锂化合物的晶体结构、电化学性能、制备方法、化学改性、应用研究等方面的重要成果进行了较全面的阐述,并指出了未来研究发展方向。     

铌基氧化物锂离子电容器负极材料研究进展

在现有的各类锂离子电容器(LICs)负极材料中,铌基氧化物被认为是很有前景的电极材料.本文以Nb2O5、M-Nb-O(M= Ti,Cr,Ga,Fe,Zr,Mg,Li,Na,K等)和(H,Li,K)-Ti-Nb-O等负极材料为例,介绍了铌基氧化物作为锂离子电容器负极材料的优势、储锂机制和常见的合成方法,并提出了该材料目前...     

硅基锂离子电池负极材料研究进展

作为锂离子电池负极材料,硅基材料具有较高的理论比容量、适中的嵌/脱锂电位、与电解液反应活性低等特点,成为最有前景的锂离子电池负极材料之一。然而由于其巨大的体积效应和较低的导电性导致其商业化应用具有相当的挑战性。本文综述了近年来为改善硅基材料的缺点而做的一些研究,展望了硅基材料作为锂离子电池负极材料的发展趋势。     

Zn掺杂对LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2结构与电化学性能的影响

用溶胶凝胶法制备了Li Ni1/3Co1/3-x Mn1/3Znx O2(x=0,1/24,2/24,4/24)锂离子电池正极材料。由X射线衍射和扫描电镜对其分析结果表明,Zn掺杂不改变Li Ni1/3Co1/3Mn1/3O2的α-Na Fe O2层状结构,当掺杂量达到4/24时,杂相产生。电化学研究表明,当Zn掺杂量为2/24时,Li Ni1/3Co1/3Mn1/3O2首次放电容量由未掺杂的169.2 m Ah·g-1降低为160.1m Ah·g-1,但循环性能明显提高,30次循环后的容量保持率由未掺杂的89.2%升至97%。并且在20、40、60和80 m A·g-1不同的电流密度下继续循环20次后,当再次恢复到20 m A·g-1的电流密度时,放电容量可恢复到150.3 m Ah·g-1。     

共沉积Co3O4-石墨负极材料及其在锂离子电池中的循环性能

在0.5 mol/L Co(NO3)2溶液中添加石墨粉,在铜箔集流体的表面电化学共沉积前驱体薄膜,然后在245℃真空热处理使之形成Co3O4-石墨粉复合负极材料.研究了共沉积Co3O4-石墨负极材料在锂离子电池中的循环性能.XRD分析和SEM观察表明,该电极材料结构由蜂窝状的Co3O4包覆石墨粉复合而成,Co3O4晶粒尺寸为0.7～2.2 nm.0.5C充放电倍率测试表明,在0.5 mol/L Co(NO3)2电解液中添加5%石墨粉形成的Co3O4-石墨复合材料负极的性能最好,该电极的初始充电比容量为872.7 mA·h/g,第20周循环的充电比容量为732.7mA·h/g,第50周循环的充电比容量为545.2 mA·h/g,比容量保持率分别为83.96%和62.47%;而纯Co3O4电极的初始充电比容量为665.3 mA·h/g,经过20次循环后充电比容量为407.9 mA·h/g,第50周循环的充电比容量为124.5mA·h/g,保持率仅分别为61.31%和18.31%.     

钛酸锂表面碳包覆改性研究进展

尖晶石结构的Li4Ti5O12由于电压平台平稳、循环寿命长、"零应变"和安全性高等优点,成为锂离子电池的热门负极材料。然而纯Li4Ti5O12本身为绝缘体,导电性很差,倍率性能不佳,这限制了它的实际应用。研究表明,对Li4Ti5O12表面进行碳包覆可以有效改善其电化学性能。结合最近国内外研究情况,综述了表面碳包覆对Li4Ti5O12负极材料改性的研究进展,分析了不同的碳包覆方法、碳层厚度、碳结构和碳含量对Li4Ti5O12/C复合材料电化学性能的影响,希望促进Li4Ti5O12/C复合电极材料在锂离子电池领域的应用。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。