保压时间对储氢合金电极电化学性能的影响

在不同保压时间下制备了Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3储氢合金电极,研究了保压时间对合金电极的活化性能、最大放电容量、放电特性和循环稳定性的影响规律和机制。结果表明,保压时间对合金电极的活化性能基本无影响,而合金电极的其他电化学性能随着保压时间的增大均呈现出先变好后变坏的变化规律,保压时间为15min时,合金展示了最佳的综合电化学性能,电化学性能的改善主要归因于合金电极的电荷转移速度加速和内阻减小。     

保压时间对储氢合金电极电化学性能的影响

在不同保压时间下制备Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3储氢合金电极,研究保压时间对合金电极的活化性能、最大放电容量、放电特性和循环稳定性的影响规律和机制。结果表明,保压时间对合金电极的活化性能基本无影响。合金电极的其它电化学性能随保压时间的增加均呈现出先变好后变坏的变化规律,保压时间为15min时,合金展示了最佳的综合电化学性能,电化学性能的改善主要归因于合金电极的电荷转移速度加速和内阻减小。     

含Sc镁镍储氢合金的电化学性能

采用机械合金化方法制备Mg1-xScxNi(x=0,0.01)系列储氢合金.XRD结构分析表明,该系列合金为非晶态合金.XPS分析结果表明,加入微量Sc可以有效地抑制合金表面的氧化程度和提高合金表面Ni与Mg的原子个数比.电化学测试结果表明,微量Sc改善了合金电极的电化学性能,Mg0.99Sc0.01Ni合金电极的放电容量、容量保持率S10、高倍率放电能力HRD200、交换电流密度I0和极限电流密度,IL分别较MgNi合金电极提高10.5%、14.7%、30.4%、202.7%和77.8%.     

Effects of pH value of reaction solution on structure and electrochemical performance of calcium-containing active material of secondary zinc electrodes

The calcium-containing active material of secondary alkaline zinc electrodes was prepared by a chemical coprecipitation method and characterized by scanning electron microscopy(SEM) and X-ray diffractometry(XRD).Their electrochemical performance was tested by the Galvanstatic charge-discharge method. The experimental results show that the sample synthesized at pH: 11. 15 has a typical calcium zincate crystal. The zinc electrode using this sample as active material shows higher discharge capacity, more negative discharge plateau potential and longer cycle lifetime.     

多孔泡沫铜支撑锡薄膜阳极材料的制备及性能

以三维多孔泡沫铜为基底,采用化学镀的方法制备锂离子电池薄膜Sn负极材料.利用扫描电镜、X射线衍射分析以及恒电流充放电测试等手段研究不同厚度薄膜Sn电极的形态、结构和电化学行为.结果表明:化学镀工艺制备的Sn电极表面的大量微孔和岛状突起不仅增大电极的表面积,而且显著缓解电极在充放电过程中体积的变化;其中镀层较薄的样品C薄膜Sn电极的初始充电(脱锂)容量为660.6 mA·h/g,经100次循环后,容量保持在299.5 mA·h/g,具有较好的循环性能.     

熔体旋淬Ml（NiCoMnAl）5贮氢合金的微结构与电化学行为

研究了熔体旋淬和常规熔铸Ml(NiCoMnAl)5贮氢合金的微结构和电化学行为。SEM和XRD分析表明,熔体旋淬合金由细小的柱状晶组成,它们的晶体结构与铸态一样,都为CaCu5型六方晶休结构。电化学测试表明,旋淬态合金电极初始容量较高（＞210mA.h/g)经1－2次循环就可达到最大放电容量。旋淬速度为10m/s的合金电极的放电容量（294mA.h/g)稍高于铸态合金电极的容量。所有旋淬态合金电极充放电循环稳定性皆优于铸态合金,在600mA/g电流质量密度下,旋流速度为10m/s的合金电极具有较好的高倍率充放电能力,但随着循环次数的增加,其容量稳定性稍次于旋淬速度为25m/s和40m/s的合金电极。     

Effect of Temperature on Structure and Electrode Properties of LaNi3.8Co0.6Mn0.3M0.3 Hydrogen Storage Alloys

对LaNi3.8Co0.6Mn0.3M0.3 (M=Ni, Al, Cu)储氢合金在238,273,303和323 K温度下的结构和电化学性能进行了一系列的实验研究。A,B,C分别代表LaNi4.1Co0.6Mn0.3（Ni替代）,LaNi3.8Co0.6Mn0.3Al0.3（Al替代）和LaNi3.8Co0.6Mn0.3Cu0.3（Cu替代）3种储氢合金,通过X射线衍射仪分别对样品A,B,C的结构进行了研究,对样品A,B,C合金粉末制成的电极进行了模拟电池测试。结果证实,制备的合金均由具有CaCu5型六方晶格结构的LaNi5相构成。3种合金中,Cu替代的合金电极低温性能得到改善,Al替代的合金电极高温放电能力得到提高。交流阻抗图谱分析表明,B合金电极样品的高温放电能力提高是由于合金电极表面形成的致密氧化膜层减缓了合金腐蚀所致,样品B,C的高倍率性能衰退是由于电极表面的充放转移反应和氢原子扩散速率下降造成的,而样品C的优良低温性能则是合金电极表面高的充放电转移反应速率所致。     

Electrochemical hydrogen storage properties of non-stoichiometric La0.7Mg0.3−xCaxNi2.8Co0.5 (x = 0-0.10) electrode alloys

The microstructure and electrochemical hydrogen storage characteristics of La_0.7Mg_0.3−xCa_xNi_2.8Co_0.5 (x = 0, 0.05 and 0.10) alloys prepared by arc-melting and subsequent powder sintering method are investigated. The electrochemical measurement results show that the cycle stability after 100 charge/discharge cycles first increases from 46.4% (x = 0) to 54.3% (x = 0.05), then decreases to 43.2% (x = 0.10), and the high rate dischargeability increases from 64.5% (x = 0) to 68.5% (x = 0.10) at the discharge current density of 1200 mA/g. The electrochemical impedance spectroscopy analysis indicates that the electrochemical kinetics of the alloy electrodes is improved by increasing Ca. The entire results exhibit that a suitable content of Ca (x = 0.05) can improve the overall electrochemical hydrogen storage characteristics of the alloys.     

动力型贮氢合金的研究

研制了5个LaNi5型贮氢合金试样，分别对5种合金试样电极的电化学放电容量、高倍率充放电和宽温度范围内充放电性能、循环稳定性及其相结构进行了测试和分析。结果表明：Sn及Si的搀杂增加了合金的非化学计量比，稳定了合金的循环稳定性并改善了合金的高倍率充放性能；合金样(Ml0．90Nd0.10)Ni3.60Co0.50Mn0.40Al0.18Si0.42的容量较高，5C充电效率大于95％，5C放电效率大于90％，400次充放循环后容量保持率大于70％；所设计合金晶型均为CaCu5相，充放电循环后合金主相仍是CaCu5相，同时发生氧化和粉化现象。     

A2B7型La0.75Mg0.25Ni3．5-xAlx（x=0-0．3）合金相结构及电化学性能

采用感应熔炼方法制备了A2B7型La0.75Mg0.25Ni3．5-xAlx（x=0，0．02，0．06 0.1，0．3）四元贮氢合金，系统研究了Al元素部分替代Ni对A2B7型La0.75Mg0.25Ni3．5合金相结构及电化学性能的影响。X射线衍射（XRD）分析表明：La0.75Mg0.25Ni3．5由单一La2Ni7相组成：Al元素加入后，开始出现CaCu5型LaNi5相，当x=0．3时，LaNis相成为合金的主相。Rietveld分析表明：随着Al含量的增加，LaNi5相逐渐增多，Al的加入利于CaCu5型LaNi5相的形成。电化学测试表明：Al替代Ni对A2B7型合金La0.75Mg0.25Ni3．5电极活化性能影响不大：而最大放电容量随Al在La0.75Mg0.25Ni3．5-xAlx，合金中替代量的增加而减小。当放电电流密度为1600mA／g时，合金的倍率放电性能由68.8％（x=0）增加到81．16％（x=0．1）然后减小到65．67％（x=0.3）。此外，La0.75Mg0.25Ni3．5-xAlx合金电极循环稳定性先增加而后下降。x=0．06时合金电极容量保持率最大（S100=85.21．％）。     

Effects of surface modification on electrochemical performance of MnO2

The MnO2 samples coated with Ca（OH）2 were prepared by a liquid-phase surface treatment method. The physical properties of the samples were examined by SEM, EDAX and chemical analysis, and their electrochemical performances were investigated by means of galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy （EIS）. The SEM results show that the samples coated with Ca（OH）2 display a porous surface structure. The electrochemical experiments indicate that the surface modification decreases the polarization of MnO2 electrodes and improves their discharge potentials and discharge capacities.     

Structure and Electrochemical Properties of Rapidly Quenched Mm0.3Ml0.7Ni3.55Co0.75Mn0.4Al0.3 Hydrogen Storage Alloy

The as-cast Mm_0.3Ml_0.7Ni_3.55Co_0.75Mn_0.4Al_0.3 alloy has been treated using rapid-quenching technique at different quenching speeds to improve the electrochemical hydrogen storage properties of the alloys. The morphologic and microstructural characterizations of alloys were studied using x-ray diffraction and transmission electron microscopy. It is observed that the quenched alloy is composed of two main phases, LaNi₅ and LaNi₃, and one minor phase of La₂Ni₃. The microstructures of the alloys vary with the quenching speeds, as well as contain microcrystalline, nanocrystalline, and amorphous structures. The electrochemical hydrogen storage properties were measured using a battery test system. The results indicate that the discharge capacity of the alloy increases initially and then decreases with the rising quenching speeds. The quenched alloy at a speed of 15 m/s exhibits the maximum discharge capacity (388 mAh/g), which is much higher than that of the AB₅-type rare earth-based hydrogen storage alloy reported in previous studies. However, the stability of the electrochemical cycle of the quenched alloy exhibits inverse trends compared with the discharge capacity. The best electrochemical cyclic stability of the quenched alloy can be obtained at a speed of 25 m/s.     

硼添加对(Ti0.65Zr0.35)1.10(V0.5Mn0.3Cr0.4Ni0.8)Bx合金结构和电化学性能的影响

采用X射线衍射仪、扫描电镜和电化学测试设备,研究添加不同含量硼对(Ti0.65Zr0.35)1.10(V0.5Mn0.3Cr0.4Ni0.8)Bx (x=0,0.01,0.05,0.1,0.2)储氢合金组织结构和电化学性能的影响。结果表明,由于硼的添加,合金中出现了不易形成氢化物的棒状VB相,降低了合金的可逆放电容量,提高了合金的活化性能、循环稳定性和合金的倍率性能。分析表明,主要是由于棒状VB相增加了氢在合金中的扩散通道,增加了相界面,减小了合金在充放电过程中的晶格应力。合金电极的反应阻抗随着硼含量的增加而减小,合金的倍率性能和循环性能明显优化。     

Structure and electrochemical properties of low-cobalt La1- xLixNi3.2Co0.3Al0.3(0≤x≤0.2) hydrogen storage electrode alloys

The structure and electrochemical properties of a new low cobalt hydrogen storage electrode alloys La1-xLixNi3.2Co0.3Al0.3(0≤ x ≤0.2) were investigated with a different additions of Li in replacement of La. With the increase of Li contents the maximum discharge capacity increases from 240 mAh·g -1 ( x =0) to 328.4 mAh·g -1(x=0.1) and the cycle stability is improved correspondingly. The capacity decay can remaiN28.6% ( x =0.2) after 230 charge/discharge cycles. The high rate discharge(HRD) ability of the alloys( x≤0.1) is improved and the best HRD is 34.1%( x =0.1) under the discharge current density 1200 mA·g -1 . It is found that the prepared alloys are basically composed of LaNi5 as matrix phase and LaNi3 as second phase( x ≤0.1). But the abundance of LaNi3 phase dramatically decreases with increasing x . When x =0.2, a new phase Al(NiCo)3 is formed.     

Effect of germanium on electrochemical performance of chain-like Co–P anode material for Ni/Co rechargeable batteries

Co–P (4.9% P) powders with a chain-like morphology were prepared by a novel chemical reduction method. The Co–P and germanium powders were mixed at various mass ratios to form Co–P composite electrodes. Charge and discharge test and electrochemical impedance spectroscopy (EIS) were carried out to investigate the electrochemical performance, which can be significantly improved by the addition of germanium. For instance, when the mass ratio of Co–P powders to germanium is 5:1, the sample electrode shows a reversible discharge capacity of 350.3 mA·h/g and a high capacity retention rate of 95.9% after 50 cycles. The results of cyclic voltammmetry (CV) show the reaction mechanism of Co/Co(OH)₂ within Co–P composite electrodes and EIS indicates that this electrode shows a low charge-transfer resistance, facilitating the oxidation of Co to Co(OH)₂.     

Preparation of NaV1−xAlxPO4F cathode materials for application of sodium-ion battery

The effects of Al doping on the electrochemical properties of NaVPO4F as a cathode material for sodium-ion batteries were investigated. Al-doped NaV1-xAlxPO4F （x=0, 0.02） samples were prepared by a simple high temperature solid-state reaction involving VPO4 and NaF for the application of cathode material of sodium-ion batteries. The crystal structure and morphology of the material were studied by Flourier-infrared spectrometry（FT-IR）, X-ray diffractometry（XRD） and scanning electron microscopy（SEM）. The results show that NaV1-xAlxPO4F （x=0, 0.02） has a typical monoclinic structure. The effects of Al doping on the performance of the cathode material were analyzed in terms of the crystal structure, charge-discharge curves and cycle performance. It is found that NaV0.98Al0.02PO4F shows an improved cathodic behavior and discharge capacity retention compared with the undoped samples in the voltage range of 3.0-4.5 V. The electrodes prepared from NaV0.98Al0.02PO4F deliver an initial discharge capacity of 80.4 mA.h/g and an initial coulombic efficiency of 89.2%, and the capacity retention is 85% after 30th cycle. Though the Al-doped samples have lower initial capacities, they show better cycle performance than Al-free samples.     

Study on the preparation and electrochemical characteristics of MgNi–CoB alloys

To improve the electrochemical performance of MgNi hydrogen storage electrode in alkaline solution, the cobalt boride powder which was prepared by mechanical alloying (MA) method was introduced. MgNi–CoB composites were prepared also by MA. The XRD patterns show they have amorphous structures. SEM photographs suggest the particle size of the composite is about 2–3 μm. It is found that the cycle stability is improved by adding small amount of CoB. The relationship of the mass ratio of MgNi:CoB and electrochemical properties was also studied. After 50 charge–discharge cycles, the discharge capacity of the MgNi–CoB composite was 29.65% higher than MgNi alloy. The cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and anticorruption test (potentiodynamic polarization) were also carried out. The results show that the cycle stability and the anticorrosion behavior of MgNi alloy in alkaline solution benefit from CoB doping.     

快淬对La-Mg-Ni系A_2B_7型电极合金循环稳定性的影响

用熔体快淬工艺制备了La-Mg-Ni系A2B7型La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1（x=0,0.05,0.1,0.15,0.2）电极合金。用XRD、SEM、TEM分析了铸态及快淬态合金的微观结构,用程控电池测试设备测试了铸态及快淬态合金电极的电化学循环稳定性,研究了快淬工艺对合金结构及电化学循环稳定性的影响,探讨了电极合金的失效机理。结果表明,快淬态合金均具有多相结构,包括两个主相（La,Mg）Ni3及LaNi5和一个残余相LaNi2。快淬处理可以显著改善合金的电化学循环稳定性。导致合金失效的主要原因是电极表面被电解液剧烈腐蚀以及合金电极在电化学循环过程中的粉化。     

Effects of rapid quenching on structure and electrochemical characteristics of La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx （x=0-0.4） electrode alloys

The La-Mg-Ni system PuNi3-type La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the rapid quenching on the structure and electrochemical characteristics of the alloys were studied. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases, (La,Mg)Ni3 and LaNi5, as well as a residual phase LaNi. The rapid quenching does not exert an obvious influence on the phase composition of the alloys, but it leads to an increase of the LaNi5 phase and a decrease of the (La, Mg)Ni3 phase. The as-quenched alloys have a nano-crystalline structure, and the grain sizes of the alloys are in the range of 20-30 nm. The results by the electrochemical measurements indicate that both the discharge capacity and the high rate discharge(HRD) ability of the alloy first increase and then decrease with the variety of quenching rate and obtain the maximum values at the special quenching rate which is changeable with the variety of Mn content. The rapid quenching significantly improves the cycle stabilities of the alloys, but it slightly impairs the activation capabilities of the alloys.     

热处理对超级电容器MnO2电极电化学性能的影响

采用阳极电沉积法制备MnO2粉末,并在不同温度(200～450℃)下对MnO2热处理,通过XRD分析热处理温度对MnO2粉末物相结构的影响,采用循环伏安法、恒流充放电法测试热处理温度对MnO2电极电化学性能的影响。结果表明:随着温度的升高,MnO2由原始的γ-MnO2逐渐变为β-MnO2,MnO2电极的比容量先增加后减小;当温度为300℃时,MnO2电极的比容量达到最高,在0.5 mol/L Na2SO4溶液中循环伏安扫描速度为10 mV.s-1条件下,电极比容量为156 F.g-1,且此时电极的稳定性良好,在10000个循环充放电内MnO2电极比容量几乎无衰减。