Electrochemical performances and structure characteristic of LiMn2O4-xYx（Y=F, Cl, Br） compounds

Spinel LiMn2 O4-x Yx (Y=F, Cl, Br) compounds were prepared by solid-state reaction and the electrochemically galvanostatic charge-discharge cycles were performed using as-prepared compounds as cathode material. The influence of halogens on their lattice constants and the relation of electrochemical properties and their lattice constants were investigated. It is concluded that when the lattice constants are smaller than that of LiMn2O4, the reversible capacity fade is suppressed and the initial capacity sacrifice is observed. When the content of fluorine is 0.05, the lattice constant of LiMn2O3.95 F0.05 is larger than that of LiMn2O4, the initial capacity is improved. An efficient method was found to control the lattice constants of LiMn2O4 through the addition of halogen, and to improve the electrochemical performance of LiMn2O4. The LiMn2O3.95 F0.05 shows excellent electrochemical charge-discharge performance, with high initial capacity of 143 mAh/g and nearly no capacity loss after 116 cycles.     

Effect of ball milling and electrolyte on properties of high-voltage LiNi0.5 Mnl.5O4 spinel

Effect of ball milling and electrolyte on the properties of high-voltage LiNi0.5 Mn1.5 O4 was investigated. Ball milling has significant effect on the synthesis and property of LiNi0.5 Mn1.5O4. The X-ray diffraction（XRD） patterns indicate that LiNio.s Mn1.5O4 can＇t be synthesized without ball milling even calcined at 900 ℃. When synthesized with bail milling, LiNi0.5 Mn1.5O4 almost exhibits only one plateau at around 4.7 V. With the increase of ball milling time, the capacity of LiNi0.5Mn1.5O4 increases, but the cycling performance is not highly affected. The electrochemical property of LiNi0.5 Mn1.5O4 highly depends on the electrolyte. The stable and high-voltage-resistant electrolyte is much beneficial to enhancement of electrochemical property of LiNi0.5 Mn1.5O4, such as coulombic efficiency and cycling performance.     

Dissolution mechanism of solid nickel in liquid zinc saturated with Fe

The dissolution behavior of solid nickel in static liquid zinc saturated with Fe at 723 K was studied. The results show that when immersing solid Ni in liquid Zn saturated with Fe, the intermetallic compound layers consisted of γ and δ phases are formed on nickel substrate, which is the same as that in liquid pure zinc. However, some F2 particles are formed in the liquid near the solid/liquid interface. These Г2 particles can easily heterogeneously nucleate on （particles and grow fast. The dissolution process is governed by diffusion of nickel atom across a concentration boundary layer in liquid Zn saturated with Fe, and is different from a mixed control mechanism of nickel in liquid pure zinc. The participation of Г2 particles makes the dissolution of solid Ni in the liquid accelerated.     

Preparation and characterization of spinel LiMn2O4 nanorods as lithium-ion battery cathodes

The hydrothermal synthesis of single-crystallineβ-MnO2 nanorods and their chemical conversion into single-crystalline LiMn2O4 nanorods by a simple solid-state reaction were reported.This method has the advantages of producing pure,single-phase and crystalline nanorods.The LiMn2O4 nanorods have an diameter of about 300 nm.The discharge capacity and cyclic performance of the batteries were investigated.The LiMn2O4 nanorods show better cyclic performance with a capacity retention ratio of 86.2% after 100 cycles.Battery cyclic studies reveal that the prepared LiMn2O4 nanorods have high capacity with a first discharge capacity of 128.7 mA·h/g.     

Corrosion Behaviors of Pure Titanium and Its Weldment in Simulated Desulfurized Flue Gas Condensates in Thermal Power Plant Chimney

The corrosion behaviors of pure titanium and its weldment welded by tungsten inert gas(TIG) welding in simulated desulfurized flue gas condensates in thermal power plant chimney were investigated using potentiodynamic polarization,electrochemical impedance spectroscopy(EIS) and immersion tests.The effects of heat input and shielding gases on the corrosion behavior of the welded titanium were also studied.Grain coarsening and Widmansta¨tten structure were found in both the fusion zone and the heat-affected zone.The welded titanium exhibited active–passive behavior in the simulated condensates.Both the polarization curves and EIS measurements confirmed that TIG welding process with different parameters had few effects on the corrosion behavior.It was proved that the microstructure changes were not the key material factors affecting the corrosion behavior of pure titanium under the test conditions,while the oxide film had remarkable effect on improving the corrosion resistance.     

Electrochemical behaviour of commercially pure titanium and Co—Cr alloy in Ringer‘s solution

The electrochemical behaviors of commercially pure titanium(CP Ti) and Co-Cr alloy in Ringer‘s solution have been investigated.The results indicate that the electric potential of passive region for CP Ti is up to 3000mV,and its passive current density is 3.078 μA/cm^2,The excellent corrosion resistance of CP Ti can be attributed to the formation of TiO2 oxide film.The passive region of Co-Cr alloy is 770mV,which is narrower than that of CP Ti.However,no hystersis loops are found in the reverse scanning curves of Cu-Cr alloy.A complex oxide film of Co3O4,Co2O3,and Cr2O3 formed on the surface provides Co-Cr alloy with a stable electrochemistry property.The corrosion rates of the crevice samples increase with the pH value of medium decreasing.The electron probe microanalyzer(EPMA) analysis indicates that Ti in CP Ti and Co,Cr in Co-Cr alloy dissolve in crevice area due to the Sealed-Cell effect.     

Wear and corrosion resistance of laser remelted and plasma sprayed Ni and Cr coatings on copper

Nickel and chromium coatings were produced on the copper sheet using plasma spraying and laser remelting. The sliding wear test was achieved on a block-on-ring tester and the corrosion test was carried out in an acidic atmosphere. The corrosive behaviors of both coatings and original copper samples were investigated by using an impedance comparison method. The experimental results show that the nickel and chromium coatings display better wear resistance and corrosion resistance relative to the original pure copper sample. The wear resistance of the coatings is 8 - 12 times as large as original samples, and the wear resistance of laser remelted samples is better than that of plasma sprayed ones. The corrosion resistance of laser remelted nickel and chromium samples is better than that of plasma sprayed samples respectively. The corrosion rate of chromium coatings is less than that of nickel coatings, and the laser remelted Cr coating exhibits the least corrosion rate.     

THE CHARACTERISTICS OF OXIDE SCALE FORMED ON LOW PRESSURE PLASMA SPRAYED NiCrAlY COATING IN THE PRESENCE OF 5% WATER VAPOR

The oxidations of low pressure plasma sprayed (LPPS) NiCrAlY coating on nickel base superalloy were studied at 1050℃ in flows of O2, and mixture of O2 and 5%H2O under atmospheric pressure. Oxide formed on the surface of LPPS NiCrAlY coating after oxidation at 1050℃ in pure O2 consisted of NiCr2O4, whereas oxide formed on the surface of LPPS NiCrAlY coating after oxidation at 1050℃ in a mixture of O2 and 5%H2O is mainly composed of NiO. The effect of water vapor on the characteristics of the oxide scale is attributed to the increase in Ni cation transport.     

Preparation and electrochemical properties of LiMn1.95M0.05O4 （M=Cr, Ni）

The preparation process and electrochemical properties of LiMn2O4 and LiMnl.95M0.05O4 （M = Cr, Ni） were studied. The results show that the decomposition temperature range of xerogel prepared with lithium acetate and manganese acetate as raw rnaterials is large and the decomposition speed is slow. Oxygen consumed is apt to get a prompt supplement during the preparation of LiMn2O4, and carbonization of the organic matter can be reduced or avoided, which is favorable to the combination of lithium and manganese. Using lithium acetate, manganese acetate, chromium nitrate, and nickel nitrate as raw materials and adopting the citric acid complexing method, it has been found that the prepared powders have high purity, high quality stability, and even doping characters. With the increase of sintering temperature, the particle size and crystal lattice constant of LiMn1.95M0.05O4 （M = Cr, Ni） enhance. However, the purity of the product is relatively high and has no obvious change, which is advantageous to the control of the quality of LiMn1.95M0.0504 （M = Cr, Ni）. Doping with a small amount of Cr3. and Ni^2＋ can stabilize the spinel structure of LiMn2O4, suppress the Jahn-Teller effect, and improve the cycling properties but reduce the initial capacity.     

Leaching and recycling of zinc from liquid waste sediments

The selective leaching and recovery of zinc in a zinciferous sediment from a synthetic wastewater treatment was investigated. The main composition of the sediment includes 6% zinc and other metal elements such as Ca, Fe, Cu, Mg. The effects of sulfuric acid concentration, temperature, leaching time and the liquid-to-solid ratio on the leaching rate of zinc were studied by single factor and orthogonal experiments. The maximum difference of leaching rate between zinc and iron, 89.85%, was obtained by leaching under 170 g/L H2SO4 in liquid-to-solid ratio 4.2 mL/g at 65 ℃ for 1 h, and the leaching rates of zinc and iron were 91.20% and 1.35%, respectively.     

锂离子电池正极材料锰酸锂派生物LiMn1.75Me0.25O4(Me=Ti, Fe, Ni)的制备与表征

在合成纯相尖晶石型锰酸锂的基础上 ,采用固相分段法制备了锰酸锂派生物LiMn1.75Ti0 .2 5O4 ,LiMn1.75Fe0 .2 5O4 和LiMn1.75Ni0 .2 5O4 。用XRD ,SEM和粒度测试仪分别对试样进行了表征。电化学检测表明 ,Fe和Ni元素能够提高锰酸锂的放电平台电压 ,Ti元素不能改善锰酸锂的电化学性能。从结构化学角度初步探讨了Fe ,Ni和Ti元素对纯相尖晶石型锰酸锂结构的影响。     

掺Cr对LiMnO2的影响

采用固相反应合成了LiMnO2和LiMn0.9Cr0.1O2，Cr的加入改变了LiMnO2的结构，与LiMnO2正交结构(空间群Pmnm)相比，LiMn0.9Cr0.1O2具有单斜结构(空间群C2／m)。充放电过程中，LiMnO2和LiMn0.9Cr0.1O2结构产生向尖晶石结构的不可逆转变。在首次放电过程中，LiMnO2只存在2．9V的电压平台，随着循环次数的增加，在2．9V和4V电压平台容量都有所增加。与LiMnO2不同，LiMn0.9Cr0.1O2在首次放电过程中存在有2．9V和4V电压平台，随着循环次数的增加，4V电压平台容量逐渐减小，在一定循环次数下，只有2．9V的电压平台存在。因此，Cr的掺杂不仅改变了LiMnO2的结构，而且改变其电化学行为。     

Preparation of modified LiMn2O4 by solid-state reaction

Modified lithium manganese oxides were prepared by solid-state reaction of LiMn2O4 and LiCoO2 as raw materials. A study was carried out by TG-DSC,XRD, DSC and electrochemical to analyse the reaction process and structural characterization of products. The results show that the LiMn2O4 reacts chemically with LiCoO2 at high temperature. All of Li and partial Co atoms can insert into the LiMn2O4 crystal lattice and a newly formed spinel phase-modified LiMn2O4 was obtained. The distribution of Co content is even in modified LiMN2O4 compound. The modified LiMn2O4 compound exhibits improved cycling stability at room and elevated temperature in comparison with the pure LiMn2O4.     

SYNTHESIZING KINETICS AND MICRO-CHARACTERIZATIONOF SPINEL LiMn2O4 FOR LITHIUM-ION BATTERYCATHODE MATERIAL

1. IntroductionLithiumion cells are the third generation of rechargeable batteries following by nickel-cadmium cells and nickel-hydrogen cells. They could be named aJs "green batteries" byvirtue8 of lower self resistance, little self discharge, no memorizing effect and no pollution.Recently, cathode materials has been much more studied such as lithiumrich transitionmetal oxides that are lithium-cobalt system, lithium-nickel system and lithium-manganesesystem[1l21. The consumption of cobalt is…     

Mg、F复合掺杂尖晶石LiMg0.1Mn1.9O3.95F0.05的合成和电化学行为研究

以己二酸为配位体采用溶胶-凝胶法合成了LiMn2O4,Mg掺杂或Mg和F复合掺杂的尖晶石锂镁氧化物正极材料.对合成出的样品采用X-射线衍射仪、X-光电子能谱、扫描显微电子镜、循环伏安测试和充放电测试仪进行了详细的研究.X-射线衍射结果表明,所有的样品都具有相同的纯尖晶石相,LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05与LiMn2O4的样品相比,具有较小的晶格参数和晶胞体积.X-光电子能谱试验结果表明,在LiMn2O4中,Mn3 和Mn4 的相对量分别为50.2%和49.8%,而LiMg0.1Mn1.9O3.95F0.05中Mn3 和Mn4 的相对量分别为48.4%和51.6%.扫描电镜结果显示,LiMg0.1Mn1.9O3.95F0.05颗粒尺寸略小、尺寸分布窄,形态结构更为规整.循环伏安实验显示,Mg和F复合掺杂的尖晶石具有更好的可逆性.LiMn2O4,LiMg0.1Mn1.9O4,LiMg0.1Mn1.9O3.95F0.05样品的首次放电能量和能量保持率分别为123、111、114 mAh·g-1和86.5%、92.3%、90.9%,且LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05具有比LiMn2O4更高的库仑效率.     

Synthesis and character of spinel LiMn2O4

1　INTRODUCTIONTheincreasingconcernsonportableelectricele mentsdemandmoreandmoreelectrochemicalener gy .Countriesallovertheworldhaveputlargequan tityofmanuallabors ,materialresourcesandfinancialresourcesonbasicresearchanddevelopmentonnewtypeofrechargeablebatteries[1,2 ] .However ,thisnewtypeofbatteriesisbasedonstudyinganddevel opingperfectperformanceofmaterials ,especiallyonmaterialsofthelithiumbatteries.LixMn2 O4 cathodematerialshavebeenwidelystudiedoverthelasttwodecadesasapotentialcand…     

钛金属表面微弧氧化处理制备抗菌性生物活性涂层

在电解液配方中,采用微弧氧化(MAO)工艺处理纯钛金属表面,构建含有钙、磷、锌、钛、氧元素的粗化、活化种植体表面。用扫描电子显微镜、X射线衍射仪、表面粗糙度轮廓仪、万能电子试验机分别观察其形貌特点、晶相结构、表面粗糙度及测定其结合强度,并进行抗菌性试验测定其抑菌率。结果表明:经过微弧氧化工艺处理后的钛种植体表面主要有二氧化钛晶相,存在少量氧化锌和钙磷盐;纯钛金属表面生成了内层致密外层疏松多孔的氧化膜,微孔似火山丘状,直径约1～5μm;试样表面粗糙度明显增加,轮廓算术平均偏差值(Ra)为(1.627±0.054)μm,相对于纯钛金属(0.685±0.012)μm提高了两倍多。涂层与基体结合紧密达(40.34±0.014)MPa。氧化锌的存在,抑菌率接近90%,抗菌活性良好。采用微弧氧化技术,通过改变电解液的成分,可得到不同生物活性的涂层,以提高种植的成功率。     

Das Korrosionsverhalten von Eisen,Zink, Aluminium und Chromnickelstahl im System Methanol-Wasser-Chlorwasserstoff

Corrosion behaviour of iron, zinc, aluminium and chromium nickel steel in the system methanol/water/hydrogen chloride The influence of water on the corrosion behaviour of pure iron, zinc, aluminium and normal 18 9 CrNi steel in hydrogen chloride containing methanol has been studied. The immersion tests and the tracing of potential dynamic current density potential curves were carried out at 20°C, oxygen being excluded. Even small quantities of water may give rise to a considerable decrease of corrosion rates. This effect is attributed in the case of iron, zinc and chromium nickel steel to increased hydrogen overvoltage, which exhibits a sudden jump between 0 and 15 Vol.-% water. Heterogenous cathodic limiting reaction currents are observed on iron. In the case of aluminium the change in corrosion rates toward lower values is caused by the inhibited anodic partial reaction. Addition of 5 Vol.-% water gives rise to a displacement of the pitting potential by approx. 400 mV in the positive direction, accompanied by a decreasing corrosion rate by about three orders. Anodic polarization of chromium nickel steel reveals that this steel can be passivated only beyond a critical water content of approx. 50 Vol.-%. A further increase of the water content gives rise to a sudden decrease of the critical passivation current density and the passivity current density. Simultaneously, the passivation potential moves toward more negative values.