Effects of Na+ doping on crystalline structure and electrochemical performances of LiNi0.5Mn1.5O4 cathode material

Pristine LiNi_0.5Mn_1.5O₄ and Na-doped Li_0.95Na_0.05Ni_0.5Mn_1.5O₄ cathode materials were synthesized by a simple solid-state method. The effects of Na⁺ doping on the crystalline structure and electrochemical performance of LiNi_0.5Mn_1.5O₄ cathode material were systematically investigated. The samples were characterized by XRD, SEM, FT-IR, CV, EIS and galvanostatic charge/discharge tests. It is found that both pristine and Na-doped samples exhibit secondary agglomerates composed of well-defined octahedral primary particle, but Na⁺ doping decreases the primary particle size to certain extent. Na⁺ doping can effectively inhibit the formation of Li_xNi_1–xO impurity phase, enhance the Ni/Mn disordering degree, decrease the charge-transfer resistance and accelerate the lithium ion diffusion, which are conductive to the rate capability. However, the doped Na⁺ ions tend to occupy 8a Li sites, which forces equal amounts of Li⁺ ions to occupy 16d octahedral sites, making the spinel framework less stable, therefore the cycling stability is not improved obviously after Na⁺ doping.     

Preparation of a needle probe with a sharp tip and high aspect ratio geometry by an electrochemical etching method

In this study, an electrochemical etching method was used to fabricate a fine needle probe with high aspect ratio. The needle probe was made of quenched and tempered high-carbon tool steel, SK 4. The needle electrode was preformed with turning machine, and then etched in the NH₄HF₂-based etchant. Owing to deactivation at the needle tip through surface adsorption of chemical species, the tip shape and contour of preformed needle can be maintained during anodic dissolution in the etchant. The anodic dissolution behavior of the needle probe can be realized with cyclic voltammetry test and Auger electron spectrometer analysis.     

Solid-state synthesis and electrochemical properties of SmVO4 cathode materials for low temperature SOFCs

A new cathode material fabricated by solid state reaction method was reported. The SmVO4 powder was obtained by firing the mixture of Sm2O3 and V2O5 powders in the temperature range of 700-1200 ℃. Its structure was identified by X-ray diffraction method and the electrochemical properties of SmVO4 as cathodes for solid oxide fuel cells (SOFCs) were investigated in single unit cell at the temperature ranged from 450-550 ℃. The results of the single fuel cell unit show that the maximum current densities are 641, 797, 688 mA·cm-2 and the maximum power output are 165, 268, 303 mW·cm-2 and the open circuit voltage are 1.04,0.96,0.92Vat 450, 500 and 550 ℃, respectively.     

利用新颖的三层电极提高LiFePO4／C正极材料的电化学性能

对常用的两层电极（活性材料层｜集电极）进行改进,提出一种新颖的夹心状三层电极（导电材料层｜活性材料层｜集电极）以提高 LiFePO4/C 的电化学性能。充放电测试表明：相比两层电极,三层电极中 LiFePO4/C 表现出更优的倍率性能。循环伏安和电化学阻抗测试表明：相比两层电极,三层电极中LiFePO4/C材料中的Fe3＋/Fe2＋氧化还原电对表现出更快的氧化还原速度。更好的可逆性能以及更低的电荷转移阻抗。在三层电极中,活性材料层表层中与LiFePO4/C颗粒尺寸相当的孔洞被粒径小得多的乙炔黑微粒填充,形成LiFePO4/C颗粒间的导电连接,为暴露在电解液主体LiFePO4/C颗粒中的LiFePO4晶体提供更多运输电子到达或离开的路径。     

Fabrication of concave micro lens array using laser patterning and isotropic etching

Micro lens arrays are widely used in optical communication and laser-fiber coupling applications. In this paper, a technique to fabricate concave micro lens arrays on glass substrate using a third harmonic Nd:YAG laser direct patterning and followed by chemical wet isotropic etching is presented. The patterning process was done on gold film, which was coated on a glass substrate by using a NC controlled laser ablation tool paths. The glass substrate is then etched by using hydrofluoric acid (HF) solutions whereby the exposed area will be dissolved away by chemical reaction with HF. The type of etching process is an isotropic etching which the etching rate is equal at all direction thus produce hemispherical concave profile on glass. The optimum laser patterning parameters is obtained and the effect of different types of HF solutions on etching efficiency is studied. The surface morphology, 2D and 3D profiles are also measured. Various micro lens diameters are fabricated with different values of lens sag.     

液膜电化学刻蚀法制备纳米电极的数学模型

介绍了液膜电化学刻蚀法制备纳米电极的原理及过程。根据钨棒刻蚀后的几何形状、电化学反应的基本原理及液体表面张力相关理论,建立了纳米电极制备的数学模型,为液膜电化学刻蚀法制备纳米电极奠定了理论基础。     

微细阵列群电极电解加工关键技术研究

提出了基于阴极优化的微细阵列圆柱凸台群电极电化学腐蚀加工法。根据电化学腐蚀基本原理,通过有限元方法分析计算群电极电化学腐蚀加工过程中的电极表面电场分布,以电流密度分布均匀性为目标,优化设计阴极形状,并进行阵列群电极制备。在制备出直径均匀的阵列群电极的基础上,探索用局部涂胶保护法制备大长径比的盘状阵列群电极,用于微细孔电解加工,进一步提高电解加工的定域性。     

高容量正极材料Li[Li0.2Ni0.2Mn0.6]O2的合成及电化学性能

以LiOH.H2O、Ni(OH)2和Mn3O4为原料,采用固相法合成锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2。通过X射线衍射(XRD)、扫描电子显微镜(SEM)对所得样品的结构和形貌进行表征,并测试了该材料的倍率性能和高低温性能。结果表明:900℃下烧结10 h后可获得晶粒细小均匀的层状Li[Li0.2Ni0.2Mn0.6]O2材料,并具有良好的电化学性能,放电容量最高可达235.9 mA.h/g;在50℃下测试时该材料的放电容量高达284.4 mA.h/g,并表现出良好的循环性能,其倍率性能和低温性能还有待进一步改善。     

正极材料LiNi0.8Co0.1Mn0.1O2的合成及电化学性能

将液相共沉淀法制备的Ni0.8Co0.iMn0.1(OH)2与LiOH·H2O混合,固相烧结合成微米级的LiNi0.8Co0.1Mn0.1O2正极材料.XRD谱表明,合成的LiNi0.8Co0.1Mn0.1O2正极材料为典型的α-NaFeO2层状结构,无杂质峰;从SEM像可以看出,产物颗粒为类球形,分散性好,由一次粒子紧密堆积而成,平均粒径为3 μm;电化学测试结果表明,在2.8～4.3 V电压范围内,750℃焙烧15h合成的LiNi0.8Co0.1Mn0.1O2材料的电化学性能最优,0.1C时,其首次放电容量为186.748mA·h/g,分别高于700和800℃时的首次放电容量172.947和180.235mA·h/g.材料在0.5和2C时循环40次后,容量保持率分别为98.32％和88.72％,循环性能良好.     

电化学腐蚀法制备倒锥状微细电极的试验研究

以电化学腐蚀加工法为基础,提出了一种加工复杂形状微细电极的工艺方法.利用端面绝缘的方法改变阳极的局部导电性,使阳极和阴极之间的电场分布发生变化,从而得到倒锥状微细电极.通过试验成功地制备出倒锥状微细电极,并结合对比圆柱状电极进行了微孔电解加工试验,结果证明倒锥状电极在微孔电解加工中能获得更好的加工定域性.     

Fabrication of 3D photonic structure on glass materials by femtosecond laser modification with HF etching process

In this study, a novel method of an array of square columns with high aspect ratio (about 10) on quartz and a pattern of complex multi-layered woodpiles on slide glass are firstly fabricated by femtosecond laser inner modification with hydrofluoric acid (HF) etching. The three-dimension (3D) patterns composted with embedded gratings are scribed by femtosecond laser focused inside the bulk materials with the central wavelength of 517 nm, the repetition rate of 100 kHz, the pulse width of 350 fs and the power of 100 mW. For the quartz glass, a high aspect ratio (about 10) structure of squared column array with the width of 10 μm and the height of 100 μm is formed from a grid pattern etched by 15 wt% HF for 15 min and 5 wt% HF for 90 min. For the slide glass, a 3D piled-octahedron structure with the feature size of 10 μm is developed from a multi-layer woodpile pattern etched by 5 wt% HF for 2 h. Moreover, the optical band structures of both 3D structures are calculated by the plane wave expansion method. And then, the defect effect of light propagation with sample paths on square and piled-octahedron structures are designed to verify the optical characteristics by finite difference time domain (FDTD) simulation in this study.     

电化学法制备铜基超疏水结构及其耐蚀性能研究

目的改善铜在海洋环境中的耐腐蚀性能。方法将化学刻蚀与电化学氧化成膜相结合,在金属铜表面制备超疏水结构,采用单因素实验分别考察了硬脂酸浓度、苯并三氮唑浓度、电沉积电压以及电沉积时间对所制备表面结构接触角的影响规律,通过动电位极化曲线和电化学阻抗谱研究了铜基超疏水结构在3.5%NaCl溶液中的耐蚀性能。结果当硬脂酸浓度为0.02 mol/L,苯并三氮唑质量浓度为40 mg/L,电沉积电压为8 V,腐蚀时间为12 h时,所制备的铜基超疏水膜接触角达到了158°,滚动角为3°。动电位极化测试表明,超疏水表面同时抑制了阳极和阴极反应,经超疏水处理的铜在3.5%NaCl溶液中的自腐蚀电流密度相比未经处理时减小了约2个数量级,缓蚀效率高达99%。电化学阻抗结果表明,电荷转移电阻由1.61 kΩ·cm~2增大至41.3 kΩ·cm~2,铜基超疏水膜具有优异的耐蚀性能。结论通过化学刻蚀与电化学氧化成膜可在铜表面构筑超疏水结构,使其在海洋环境下具有优异的耐蚀性能。     

Surface composition and electrochemical behavior of LiNi1/3Co1/3Mn1/3O2 cathode material with copper additive

LiNi_1/3Co_1/3Mn_1/3O₂（NCM） cathode material containing copper was prepared by co-precipitation method.The material was characterized by X-ray photoelectron spectroscopy（XPS） and galvanostatic cycling.XPS data indicate that surface compositions of the samples containing copper are different from the bare NCM.Copper on surface of particles was enriched,while nickel and lithium content was reduced.The electrochemical performance of NCM was affected by the change of surface compositions.Cycling performance charged to the cutoff voltage of 4.6 V was improved by introducing copper into the material.The effects of copper content on electrochemical behaviors of NCM at 4.5 V were discussed.     

Micro-machinability of monocrystal silicon by direct etching using excimer laser

The high flexibility of laser direct writing and its potential capability of fabricating micro-mechanical structure are discussed. Aiming at providing knowledge for micro-engineering application, experiments on direct etching of monocrystal silicon with focusing KrF excimer laser beam (λ = 248 nm) were carried out. The validity of non-thermal excimer laser material processing was examined by SEM observation on the “heat-affected zone (HAZ)”. An empirical formula establishing the relationship of etching depth versus laser energy per pulse and the number of laser pulses has been derived from the experiments. Impact damage at the underside of silicon wafer has been observed. Its relevant causes are analyzed.     

Fabrication of Sn-Ni alloy film anode for Li-ion batteries by electrochemical deposition

Sn-Ni alloy films for Li-ion batteries were fabricated by electrochemical deposition with rough copper foils as current collectors. The influence of electrochemical-deposition temperature and heat treatment were also investigated. By galvanostatic cell cycling the film anodes can deliver a steady specific capacity. The morphological changes cause the differences in capacity retention. After farther heat treatment, the film anodes present a better cycle performance, with a specific capacity of 314 mA·h/g after 100 cycles. This high capacity retention can be due to its smooth, compact surface formed in the heat treatment process.     

Synthesis and electrochemical properties of Li[NixCoyMn1-x-y]02 (x, y=2/8, 3/8) cathode materials for lithium ion batteries

The uniform layered Li(Ni2/8Co3/8Mn3/8)O2, Li(Ni3/8Co2/8Mn3/8)O2, and Li(Ni3/8Co3/8Mn2/8)O2 cathode materials for lithium ion batteries were prepared using the hydroxide co-precipitation method. The effects of calcination temperature and transition metal contents on the structure and electrochemical properties of the Li-Ni-Co-Mn-O were systemically studied. The results of XRD and electrochemical performance measurement show that the ideal preparation conditions were to prepare the Li(Ni3/8Co3/8Mn2/8)O2 cathode material calcined at 900℃ for 10 h. The well-ordered Li(Ni3/8Co3/8Mn2/8)O2 synthesized under the optimal conditions has the I003/I104 ratio of 1.25 and the R value of 0.48 and pedance of 558 Ω after the first cycle. The decrease of Ni content results in the decrease of discharge capacity and the bad cycling perform-ance of the Li-Ni-Co-Mn-O cathode materials, but the decreases of Mn content and Co content to a certain extent can improve the electro-chemical properties of the Li-Ni-Co-Mn-O cathode materials.     

Effects of synthesis conditions on the structural and electrochemical properties of layered LiNi1/3Co1/3Mn1/3O2 cathode material via oxalate co-precipitation method

The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using (Ni1/3Co1/3Mn1/3)C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/3O2 were 950°C for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.     

Selective removal technology using chemical etching and excimer assistance in precision recycle of color filter

Color filters are produced using semiconductor production techniques although problems with low yield remain to be addressed. This study presents a new means of selective removal using excimer irradiation, chemical etching, or electrochemical machining on the fifth generation TFT LCDs. The selective removal of microstructure layers from the color filter surface of an optoelectronic flat panel display, as well as complete removal of the ITO thin-films, RGB layer, or resin black matrix (BM) layer from the sub...     

锂离子导体包覆镍锰酸锂正极材料的制备及其电化学性能

采用原位包覆法制备表面包覆Li1.3Al0.3Ti1.7(PO4)3(LATP)的Li Ni0.5Mn1.5O4(LNMO),即LNMO@LATP正极材料。采用X-射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)及电化学测试等手段对其物相结构、表面形貌及电化学性能进行研究。结果表明:LATP以无定型态紧密包覆于Li Ni0.5Mn1.5O4的表面,包覆层厚度约为5 nm。由于LATP包覆层具有保护电极材料表面和提高锂离子导电的双重作用,减少了电极过程的副反应,降低了电化学极化,提供了更多的锂离子扩散通道,导致LNMO@LATP具有比LNMO更稳定的循环性能和更好的倍率性能,特别是在高温的情况下。室温下在0.2C放电时,LNMO@LATP和LNMO的首次放电容量分别为141.5和142.6m A·h/g,经80次循环后,二者放电容量保持率分别达到99.2%和98.0%;而在10.0C放电时,LNMO@LATP和LNMO的首次放电容量分别为93.5和70.6 m A·h/g,经80次循环后,二者放电容量保持率分别达到66.1%和49.5%。当循环温度提高到55℃时,LNMO@LATP和LNMO在0.2C循环80次后的放电容量保持率分别为95.5%和79.2%;而在10.0C放电循环80次后,放电容量保持率分别为88.0%和51.0%。