Effects of Ti and Zr Substituted on the Electrochemical Characteristics of MgNi-Based Alloy Electrodes

Mg-based hydrogen storage alloys MgNi, Mg0.9Ti0.1Ni, and Mg0.9Ti0.06Zr0.04Ni were successfully prepared by means of mechanical alloying （MA）. The structure and the electrochemical characteristics of these Mg-based materials were studied. The X-ray diffraction （XRD） result shows that the main phases of the alloys exhibit amorphous structure. The scanning electron microscopy （SEM） photograph shows that the particle size of Ti and Zr substituted alloys was about 2-4 μm in diameter. The cycle lives of the alloys were prolonged by adding Ti and Zr. After 50 charge-discharge cycles, the discharge capacity of Mg0.9Ti0.06Zr0.04Ni was 91.74% higher than that of MgNi alloy and 37.96% higher than that of Mg0.9Ti0.1Ni alloy. The main reason for the electrode capacity decay is the formation of Mg（OH）2 （product of Mg corrosion） at the surface of alloy. The potentiodynamic polarization result indicates that Ti and Zr doping improves the anticorrosion in an alkaline solution. The electrochemical impedance spectroscopy （EIS） results suggest that proper amount of Ti and Zr doping improves the electrochemical catalytic activity significantly.     

Effects of Ti and Co on the Electrochemical Characteristics of MgNi-Based Alloy Electrodes

Mg-based hydrogen storage alloys MgNi, Mg0.9Ti0.1Ni and Mg0.9Ti0.1Ni0.9Co0.1 were successfully prepared by means of mechanical alloying （MA）. The structure and the electrochemical characteristics of these Mg-based materials were also studied. The results of X-ray diffraction （XRD） and scanning electron microscopy （SEM） show that the main phases of the alloys exhibit amorphous structures, and trace of Ni co-exists. The charge-discharge cycle tests indicate these alloys have good electrochemical active characteristics. And the cycle stability of Ti and Co doped alloy was better than that of MgNi alloy. After 50 cycle charge-discharge, the discharge capacity of the Mg0.9Ti0.1Ni0.9Co0.1 alloy was much better than that of MgNi and Mg0.9Ti0.1Ni alloys. The discharge capacity of Mg0.9Ti0.1Ni0.9Co0.1 was 102.8% higher than that of MgNi alloy, and 45.49% higher than that of the Mg0.9Ti0.1Ni alloy. During the process of charge-discharge cycle test, the main reason for the electrode capacity fading is the corrosion of Mg to Mg（OH）2 on the surface of alloys. The Tafel polarization test indicates Ti and Co improve the anticorrosion in an alkaline solution. The EIS results suggest that proper amount of Ti and Co doping improve the electrochemical catalytical activity on the Mg-based alloy surface significantly.     

Methane dry reforming on Ni/La_2Zr_2O_7 treated by plasma in different atmospheres

A series of Ni/La2Zr2O7 pyrochlore catalysts prepared by impregnation method and treated by dielectric barrier discharge(DBD) plasma in different atmospheres and varied sequences were prepared and applied for dry reforming of methane(DRM). It is found that all of the plasma treated catalysts show evidently improved activity and coke resistance in comparison with the non-plasma treated one. The best performance is achieved on Ni/La2Zr2O7–H2P–C,a catalyst treated in H2 plasma before calcination. TGA-DSC and SEM demonstrate that carbon deposition is significantly suppressed on all of the plasma treated samples. Moreover,XRD and TEM results testify that both Ni O and Ni sizes on the calcined and reduced samples treated by plasma are also decreased,which results in higher Ni metal dispersion on the reduced and used catalysts and enhances the interactions between Ni sites and the support. It is believed that these are the inherent reasons accounting for the promotional effects of plasma treatment on the reaction performance of the Ni/La2Zr2O7 pyrochlore catalysts.     

SnO2/ 石墨复合材料作为锂离子电池负极材料研究

Nano-scale SnO₂ powders were prepared by hydrolyzation. Graphite was poured into the SnCl₄ solution during hydrolyzation. After drying and calcining at 360 ℃, the negative electrode composite material of nanosized SnO₂ and graphite was obtained. The composite materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average crystallite size was in the range of 15～20 nm. Electrochemical lithium insertion/extraction was studied preliminarily on the obtained composite. The discharge capacity of nanosized SnO₂ / graphite composite was found to have a high electrochemical reversible capacity for Li-ion insertion and extraction, which possessed the advantages of both higher discharge capacity of SnO₂ and lower discharge potential of graphite. In addition, the cycle capability was also improved due to the inhibiting effect of the composite against pulverization and agglomeration to a certain extent during Li-ion insertion and extraction.     

Synthesis and Properties of Polyurethane Resins from Liquefied Benzylated Wood

In this paper, polyurethane resins were synthesized from liquefied benzylated wood and TDI (toluene diisocyanate)-TMP (trihydromethylene propane) prepolymer. And the relation between microphase structure and properties of PU samples were also studied. The results indicated that coatings obtained had good mechanical and thermal properties. The amount of the curing agent has great effect on the degree of phase segregation. In addition, with increased the curing agent amount, the thermal stabilities were also improved.     

Autothermal Reforming of Methane over Ni Catalysts Supported on CuO-ZrO2-CeO2-Al2O3

Ni catalysts supported on various mixed oxides of Al2O3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen over Ni catalysts supported on the mixed oxide ZrxCe30-xAl70Oδ (x=5, 10, 15). The catalytic performance of Ni/Zr10Ce20Al70Oδ was better than that of other catalysts. XRD results showed that the addition of Zr to Ni/Ce30Al70Oδ prevented the formation of NiAl2O4 and facilitated the dispersion of NiO. Effects of CuO addition to Zr10Ce20Al70Oδ were also investigated. The activity of Ni catalyst supported on CuO-ZrO2-CeO2-Al2O3 was somewhat affected and the Ni/Cu5Zr10Ce20Al65Oδ showed the best catalytic performance with the highest CH4 conversion, yield of H2, selectivity for H2 and H2/CO production ratio in operation temperatures ranging from 650 to 750℃.     

Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce0.2Zr0.1Al0.7Oδ Catalyst

The transition metals (Cu, Co, and Fe) were applied to modify Ni/Ce0.2Zr0.1 Al0.7Oδcatalyst. The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1 Al0.7Oδautothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals (Cu and Co) significantly increased the activity of catalyst under the conditions of lower reaction temperature, and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδwas found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts. Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ.     

Effect of 3-Amino-5-mercapto-1,2,4-triazole on Electroless Nickel Deposition

The effects of organic additive, 3-amino-5-mercapto-1,2,4-triazole （AMTA） on bath stability, deposition rate, reaction activation energy, and Ni-P coating composition in acidic electroless nickel plating were investigated. Polarization curve method and infrared reflection spectroscopy were used to analyze the mechanism of the effect of AMTA on electroless nickel deposition. It was observed that AMTA improved bath stability, decreased the deposition rate, and increased the reaction activation energy. It was also revealed that AMTA decreased the phosphorus content and increased the sulfur content in Ni-P coating. In addition, AMTA inhibited the anodic oxidation of hypophosphite and accelerated the cathodic reduction of Ni^2＋. Infrared reflection spectroscopy result indicates that AMTA was adsorbed on the surface of Ni-P and interacted with Ni^2＋ to form an AMTA-Ni^2＋ compound. On the basis of the results of this study, the mechanism of the effect of AMTA on electroless nickel deposition was deduced.     

Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate (MMDS) as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate(MMDS) on the high-temperature(~50℃) cycle performance of LiMn_2O_4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry(EDX) indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn_2O_4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.     

Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate（MMDS） as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate(MMDS) on the high-temperature(~50℃) cycle performance of LiMn_2O_4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry(EDX) indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn_2O_4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.     

Mg1-xTixNi(0≤x≤0.4)系列合金的合成及性能研究

采用机械合金化法成功制备了Mg1-xTixNi(0≤x≤0.4)系列三元合金.XRD结构分析表明,不同成分的合金在相同的球磨时间下非晶化程度有所区别,并且合金的非晶化程度随着球磨时间的增加而趋于完全.少量Ti的加入使得该系列合金的电化学性能及循环稳定性都有所提高.在球磨120h的该系列合金中,Mg0.9Ti0.1Ni合金的最大初始放电容量达到356.85mA·h·g-1(100mA·g-1,-0.5Vvs.Hg/HgO),而Mg0.7Ti0.3Ni合金的循环稳定性最好.Ti的加入亦提高了合金的抗腐蚀性能,使其腐蚀电位正移.     

四元Mg0.9Ti0.1Ni0.9X0.1(X=Mn,Zn,Co,Fe)系列合金的制备及性能研究

用机械合金化法合成了Mg0·9Ti0·1Ni0·9X0·1(X=Mn,Zn,Co,Fe)系列合金.X射线衍射(XRD)结构分析表明,用X部分替代Ni后,促进了Mg0·9Ti0·1Ni合金的非晶化过程.用Co和Fe部分替代Ni提高了合金的放电容量,但却降低了合金的循环稳定性.用Zn和Mn部分替代Ni提高了合金电极的循环寿命,尤其是Mg0·9Ti0·1Ni0·9Zn0·1合金电极经10个充放电循环后,其放电容量仍可达到313·8mA·h/g.对添加Co后的合金进行p-c-T测试发现,Mg0·9Ti0·1Ni0·9Co0·1合金的吸放氢容量明显比Mg0·9Ti0·1Ni合金高,这与电化学所测到的结果一致.     

Mg0.9Ti0.1Ni1－xCox (x＝0.05, 0.1, 0.15, 0.2)合金的合成及电化学性能研究

采用机械合金化法合成了Mg_0.9Ti_0.1Ni_1－xCo_x (x＝0.05, 0.1, 0.15, 0.2)系列四元合金, 并对该系列合金的结构和电化学性能等方面进行了研究. 球磨100 h的该系列合金, XRD结果表明, X射线衍射峰均呈现宽化趋势, 基本呈非晶态. 充放电结果表明, 该系列合金具有较好的活化性能, 它们的循环稳定性明显好于MgNi合金, 其中Mg_0.9Ti_0.1Ni_0.8Co_0.2最大放电容量最高, 为427.5 mAh•g^－1. 在充放电循环过程中, Mg在合金表面形成了Mg(OH)₂是合金电极衰减的主要原因. 腐蚀曲线的测试结果表明, Co的添加可以提高合金电极在碱液中的抗腐蚀能力, 从而提高了电极的循环稳定性.     

熔体旋淬合金Zr0.9Ti0.1(Ni,Co,Mn,V)2.1的微结构与电化学性能

对比研究了熔体旋淬和常规熔铸合金Zr0.9Ti0.1(Ni,Co,Mn,V)2.1的微结构和电化学性能,XRD分析表明,熔体旋淬合金在退火前后的晶体结构和铸态合金一样,均为面心立方结构,由LaveC15相组成;并且随旋淬速度的增加,旋淬合金中的非晶成分越多,电化学测试表明：旋淬合金有较好的活化性能,但其最大放电容量较低,小于280mAh/g,而退火后的旋淬合金需经30次循环才能完全活化,其最大放电容量皆为340mAh/g左右,高于铸态合金和退火前的旋淬合金;在电流密度为300mA/g下进行充放电循环,发现退火后的旋淬合金循环稳定性明显高于铸态合金电极,并且随旋淬速度的增加,循环稳定性越好,经过800次循环后,退火后的40m/s合金容量保持率高达85％,容量衰减率只有6．9％。     

Mg0.9Ti0.1Ni0.85Co0.15合金的石墨粉及镍粉球磨表面包覆性能

选用非晶态的Mg0.9Ti0.1Ni0.85Co0.15合金粉末与石墨粉及镍粉进行球磨表面包覆。SEM分析结果表明,己包覆石墨和镍粉的合金表面上吸附着一层小的颗粒,形成薄层将原来的合金表面包覆起来。使用XPS分析了合金表面元素。结果表明,包覆石墨粉后,合金表面碳元素的质量分数和原子分数均增加,Mg的质量分数从22.74%减小至22.23%,原子分数从36.43%减小到32.94%,从而减小了Mg在碱液中的腐蚀几率,提高合金的抗腐蚀性能;包覆镍粉后,合金表面Ni的质量分数由59.89%增加到60.04%,原子分数由40.63%增加到41.02%,形成合金表面富Ni的保护层,提高了合金的抗腐蚀性能。充放电循环测试表明,循环30周后,包覆石墨粉的合金电极容量保持率为32.05%,包覆镍粉的合金电极容量保持率为41.26%,而未包覆的电极容量保持率仅为17.88%。合金电极极化曲线测试结果表明,石墨或镍粉的包覆提高了Mg0.9Ti0.1Ni0.85Co0.15合金电极的循环稳定性和在KOH碱液中的抗腐蚀性能。     

Mg0.9－xTi0.1PdxNi(x=0.04～0.1)贮氢合金电极腐蚀行为研究

研究了Pd部分替代Mg对Mg0.9－xTi0.1PdxNi(x=0.04～0.1)贮氢合金腐蚀性能的影响. 利用机械合金化方法制备了Mg0.9－xTi0.1PdxNi(x=0.04～0.1)贮氢合金. XRD和TEM分析表明经120 h球磨后该合金完全非晶化. 循环充放电测试结果表明, Pd的替代有效地延长了Mg0.9－xTi0.1PdxNi(x=0.04～0.1)合金的循环寿命. 采用开路电位测量, 阳极极化, 电化学阻抗和X射线光电子能谱研究了该合金的腐蚀行为. 结果表明, 随着Pd含量增加, 合金腐蚀电位正移, 初始腐蚀电流下降, 腐蚀电流增加的速度变缓. 采用本文提出的等效电路模型较好地拟合了合金的电化学阻抗谱. 分析表明, 随着Pd含量的增加, 合金表面钝化膜厚度和电阻逐渐增大. X射线光电子能谱分析表明, Pd的加入减弱了合金在充放电过程中的氧化程度. 当Pd含量达到0.1时, Mg0.9－xTi0.1PdxNi(x=0.04～0.1)合金的耐腐蚀性能最好, 其放电容量保持率最高.     

Synthesis and Electrochemical properties of Phospho-olivine Type LiFexM(1-x)PO4(1 ≥x≥0) Compounds

Olivine-type LiFePO4 appears to be the best candidate for large size Lithium ion batteries compared with conventional cathode materials such as LiCoO2, LiNiO2 and LiMnO4 based on cost,environmental benign and safety. In addition, LiFePO4 has a large theoretical capacity of 170 mAhg-1, good cycle stability, and a flat discharge potential of 3.4V versus Li/Li+. However, its low ionic/electronic conductivity limits the electrochemical prosperities of this material, especially its rate capability. Many efforts have been devoted to increase and optimize the conductivity of LiFePO4 besides minimizing the particle size and making an intimate carbon coating around the particles, though it is not the way to change intrinsically the electrical conductivity of LiFePO4.In this research, LiFePO4 was synthesized by solid-state reaction. A discharge capacity of around 110mAhg-1 was achieved under a low current density of 17mAg-1 at room temperature. In order to compounds were prepared, respectively. As an example, LiFe0.9Ti0.1PO4 had the same XRD pattern as LiFePO4 but more developed crystalline intensity. The charge-discharge capacities of LiFe0.9Ti 0.1PO4 at the first cycle were 134mAhg-1 and 129 mAhg-1, respectively. The efficiency of charge-discharge was larger than 96%. A reversible capacity of 110 mAhg-1 was obtained after 20cycles and the capacity retention was over 85%. Moreover, the discharge voltage flat was maintained at 3.4V verse Li/Li+ after the first cycle. At even higher rates, it also exhibited good electrochemical performances.     

V2.1TiNi0.4Zr0.06Cux(x=0-0.12)储氢合金的微结构及电化学性能

采用磁悬浮感应熔炼方法制备了V2.1TiNi0.4Zr0.06Cux (x=0-0.12)储氢合金, 经XRD、SEM、EDS和电化学测试等系统研究了Cu添加量对合金微结构及电化学性能的影响. 结果表明, 所有合金均由V基固溶体主相和C14型Laves第二相组成, 且第二相沿主相晶界形成三维网状分布; 合金主相和第二相的晶胞体积均随着Cu含量x的增加而增大. 电化学性能测试表明, 添加适量(x=0.03-0.06)的Cu可以提高合金的最大放电容量, 并对活化性能基本没有影响; 而过高的Cu添加量(x≥0.09)会降低合金的放电容量. 此外, 添加Cu可使合金的高倍率放电性能得到明显改善, 充放电循环稳定性有所提高. 在所研究的合金样品中, V2.1TiNi0.4Zr0.06Cu0.03合金具有最佳的综合性能.