纳米氢氧化镍掺杂镍电极的电化学性能

介绍了一种通过合成草酸镍,进而生成纳米Ni(OH)2的新的合成路线.X射线衍射以及红外光谱测试结果表明,得到的Ni(OH)2为β型.通过透射电镜观察到,合成的Ni(OH)2样品呈针状,长度在100～200 nm之间,直径为10～20 nm.对掺杂质量分数8%纳米级氢氧化镍的电极的电化学性能进行了测试,可以发现:放电容量比未掺杂的球形氢氧化镍电极提高了9.6%,且经过10次循环以后放电容量仍能达到原来的94%.     

纳米氢氧化镍制备的最新进展

纳米材料由于其颗粒较小,因此其性能和常规材料相比有较大的改变.随着纳米材料科学技术的迅猛发展,纳米材料的研究逐渐扩展到化学电源领域.氢氧化镍作为Ni-MH二次电池的主要正极活性材料,对电池的容量和寿命起着关键性的作用.但是目前传统方法制备的氢氧化镍容量较低,远没有达到其理论值.随着将纳米材料制备技术引入到氢氧化镍的合成,使其比容量有了质的提升,合成纳米氢氧化镍也成为研究的热点.介绍了纳米材料的一般性知识,同时阐述了纳米氢氧化镍作为Ni-MH电池的正极活性材料所具有的特性和制备方法上的最新进展,以及在制备和应用方面出现的一些问题.     

氢氧化镍纳米片的制备

以硝酸镍为镍源,采用水热法制备N i(OH)2纳米片,通过改变反应物浓度、反应时间、反应温度,研究不同实验条件对N i(OH)2纳米片的影响;通过X-射线衍射、扫描电子显微镜等手段对样品进行了表征。     

Co-Zn复合掺杂纳米氢氧化镍的制备及性能

采用微乳液法合成了Co、Zn复合掺杂的纳米Ni(OH)_2粉体,通过改变温度、pH值对产品堆积密度、比容量的影响, 发现T=50℃、pH=11时,样品电极的性能较好,以50 mA·g~(-1)恒电流充放电,终止电压为1．0V的充放电制度下,其比容量达 282mAh·g~(-1),样品经过50次循环后容衰减率仅为2．5％．     

锂离子电池负极材料纳米SnO2制备及电化学性能研究

利用溶胶-凝胶方法制备出纳米二氧化锡,并对所制备的纳米材料进行扫描电镜SEM、透射电镜TEM、粉末X射线衍射(XRD)、循环伏安(CV)以及循环性能测试.电化学性能测试表明所制备出的纳米电极材料具有较高的放电比容量,在电流密度为0.3mA/cm2、电位区间为0.05～1.2V vs.Li /Li时首次可逆放电比容量可达789mAh.g-1.     

纳米LiMn2O4制备及电化学性能研究

以高能球磨后的MnO2为前躯体,用水热法成功合成了平均粒径为60nm的LiMn2O4纳米微粒。实验结果表明,所合成的纳LiMn2O4在0．2℃倍率放电条件下,首次放电比容量为122mAh／g,样品在经过20次循环后容量下降约为5％左右,表现出较好的电化学性能。     

SnO2纳米球的制备、结构及电化学性能研究

以Na2SnO3.4H2O为原料,CO(NH2)2为表面活性剂,采用水热法制备了SnO2纳米球。利用X射线衍射（XRD)、扫描电子显微镜（SEM)、比表面积测试仪（BET）及电化学测试仪等研究材料的结构、形貌、比表面积及电化学性能。结果表明,制备的SnO2材料具有较好的球体形貌,颗粒分散均匀,形状规准,半径约为400 nm,结构呈典型的金红石相。在电压范围为0.01~3 V, 200 mA/g的电流密度下进行充放电测试,首次放电比容量为2206.6 mAh/g,50次循环后,放电比容量保持在440 mAh/g,具有较好的循环性能。     

高密度氢氧化镍的制备研究

用氨催化液相沉淀法合成了氢氧化镍颗粒。研究了pH、反应时间、反应原料等工艺条件对堆积密度和颗粒形态的影响规律。在50±2℃,pH10.8±0.1下,并流加入Ni(NO_3)_2、KOH和氨水,反应14小时制得堆积密度1.82g/cm~3的球形均匀Ni(OH)_2颗粒。     

SnO_2纳米球的制备及其电化学性能

以Na_2SnO_3·4H_2O为原料,CO(NH_2)_2为沉淀剂,采用水热法制备了SnO_2纳米球。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面积测试仪(BET)及电化学测试仪测试材料的结构、形貌、比表面积及电化学性能。结果表明,所制备的纳米SnO_2材料具有规整的球体形貌,颗粒分散均匀,半径约为400nm,呈典型的金红石相结构。在电压为0.01~3V、电流密度200mA/g的条件下进行充放电测试,首次放电比容量为2206.6mA·h/g,50次循环后,放电比容量保持在440mA·h/g,具有较好的循环性能。     

氢氧化镍超微粉的制备研究及微观结构分析

采用沉淀转化法制备了氢氧化镍超微粉 ,并对表面活性剂的浓度、pH值及转化温度等实验参数对氢氧化镍粉末组成和结构的影响作了较细致的研究。实验结果表明 :当转化温度为 60℃ ,表面活性剂浓度为 15ml·L- 1 ,pH值为 11.0～ 12 .0时 ,所得样品为球形 ,粒径约 2 0 0nm左右     

High temperature performances of yttrium-doped spherical nickel hydroxide

The regular and yttrium-doped spherical β-phase nickel hydroxides were synthesized by means of chemically co-precipitation. The yttrium-doping with long needle-like nanocrystallites observed by TEM promoted the formation of the spherical nickel hydroxide with the larger diameter of about 5 μm. The discharge capacity of the yttrium-doped spherical nickel hydroxide was measured to be slightly lower than that of the regular spherical nickel hydroxide at room temperature. At temperatures of above 50 °C, however, the discharge capacity of the yttrium-doped nickel hydroxide is much higher than that of the regular spherical nickel hydroxide. The improvement of discharge capacity at elevated temperatures was contributed to the increase of the charge acceptance of yttrium-doped nickel hydroxide. The formation of an yttrium-rich surface layer on nickel hydroxide particles raised the oxygen evolution over-potential, leading to performance improvements of the nickel hydroxide electrode. The improvement of high temperature charge acceptance of yttrium-doped nickel hydroxide remarkably contributed to the high temperature charge-discharge efficiency of the nickel-metal hydride (Ni-MH) batteries with a commercial AAA size.     

Physical and electrochemical characteristics of aluminium-substituted nickel hydroxide

Substitution of 20 aluminium for nickel in the lattice of nickel hydroxide, prepared by coprecipitation, leads to a hydrotalcite-like compound of formula Ni_0.8Al_0.2(OH)₂(CO₃)_0.1.0.66H₂O. It has been found that the compound has prolonged stability in 6m KOH solution and can be used as the positive electrode material in rechargeable alkaline batteries. The structure, morphology and composition of the compound have been investigated by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. The electrode comprising the aluminium-substituted nickel hydroxide has greater discharge capacity and higher utilization of active material than the -Ni(OH)₂ electrode. Cyclic voltammetry suggest that the aluminium-substituted nickel hydroxide has better reversibility of the Ni(OH)₂/NiOOH redox couple and higher oxygen evolution overpotential than -Ni(OH)₂. The mechanism of the electrode reaction has also been discussed and the proton diffusion coefficient in the compound has been determined.     

Physical and electrochemical characteristics of nanostructured nickel hydroxide powder

Nanostructured nickel hydroxide powder has been synthesized by a chemical precipitation method with the aid of ultrasound radiation, and the physical properties of the synthesized material were characterized by scanning electron microscopy, specific surface area, X-ray diffraction and differential scanning calorimetry. It was found that nanostructured nickel hydroxide was crystalline -Ni(OH)₂ with a nanocrystalline and nanoporous surface structure. The crystallite sizes of nanostructured -Ni(OH)₂ along the c- and a-axis were 2.5 and 2.3 nm, respectively, as calculated from (001) and (100) X-ray diffraction peaks. In comparison with spherical -Ni(OH)₂ which has now been widely used as the active material for pasted nickel electrodes, nanostructured -Ni(OH)₂ possessed a smaller crystallite size, more structural defects, a larger lattice parameter of c₀, a higher specific surface area and lower thermal decomposition temperature. These physical characteristics were advantageous to the improvement of electrochemical activity of the nanostructured nickel hydroxide powder. Studies indicated that the filling property and flowability of nanostructured -Ni(OH)₂, which were characterized by the measurements of tapping density and angle of repose, were inferior to those of spherical -Ni(OH)₂. Pasted nickel electrodes with a porous nickel-foam substrate were prepared using a mixture of the nanostructured and spherical Ni(OH)₂ powders as the active material. Charge/discharge tests showed that the addition of an appropriate amount of nanostructured Ni(OH)₂ powder to spherical Ni(OH)₂ powder could enhance the specific discharge capacity and high-rate capability of the pasted nickel electrodes. This enhancement could be attributed to a lowered electrochemical reaction impedance for the nickel electrode with the addition of nanostructured Ni(OH)₂ relative to the electrode without nanostructured Ni(OH)₂.     

撞击流制备高纯纳米氢氧化镁技术研究

采用撞击流反应结晶方法，以青海盐湖水氯镁石为原料，制备了高纯纳米氢氧化镁。研究了各种操作条件对氢氧化镁纯度的影响，并确定了控制因素。并采用X射线衍射（XRD）、透射电镜（TEM）对颗粒形态进行表征。结果表明：可以制备出纯度大于99％、平均粒径为13．5nm的氢氧化镁。适宜条件：镁离子浓度0．25mol／L，镁离子与氢氧根浓度比1：2，反应温度40℃，搅拌时间30min，搅拌转速400r／min，撞击流率100mL／min。     

纳米氧化铈的制备及其催化性能

纳米氧化铈是新兴的催化材料,在化学工业和环境污染控制方面有着广泛的应用前景。对近年来国内外制备纳米氧化铈材料的不同方法进行了阐述和比较。其中溶胶-凝胶法和沉淀法工艺已经较为成熟,而其他方法,如共沸精馏法、冰冻脱水法、水解法、气相法、微乳液法、表面修饰法、液-液两相法、熔融法、固相反应法等,都还需要进一步完善。对纳米氧化铈的催化性能进行了研究,研究表明,纳米氧化铈的催化性能大大优于传统的非纳米氧化铈粉体。     

纳米氧化镁的制备研究

研究了由碳酸铵和氯化镁制备纳米氧化镁的方法。以碳酸铵和氯化镁为主要原料，加入有机表面活性剂，经过反应、过滤、水洗、醇洗、干燥和灼烧制得纳米氧化镁。经表观密度、比表面积、孔容积、粒径及透射电镜的测定，粒子大小均在纳米范围。试验结果证明，试验工艺路线及测定方法均适合纳米氧化镁制备。主要原料碳酸铵和氯化镁来源广泛，价格低廉，对纳米氧化镁的工业生产具有重要意义。     

卤水-石灰乳法制备纳米氢氧化镁新工艺研究

以天然盐湖卤块为原料,采用石灰乳为沉淀剂,控制温度在40～90 ℃,采用特殊的除钙技术,使产品中氢氧化镁质量分数大于98%,氧化钙质量分数小于0.2%,分解温度396.93℃,热质量损失30.96%.利用扫描电子显微镜对产品形貌进行表征,结果显示制得的氢氧化镁产品粒径在80 nm左右,粒子呈片状晶体结构.制得的氢氧化镁产品比表面积为39.2 m2/g.此生产工艺简单,生产成本低,是一种比较清洁的合成工艺路线.新工艺生产的产品质量不仅达到国家行业标准,而且达到国外企业标准,可望进行工业性生产.     

Effects of ball milling on the physical and electrochemical characteristics of nickel hydroxide powder

Nickel hydroxide powder was modified by the method of ball milling, and the physical properties of both the ball-milled and un-milled nickel hydroxide were characterized by scanning electron microscopy, specific surface area, particle size distribution and X-ray diffraction. It was found that the ball milling processing could obviously increase the surface area, decrease the particle and crystallite size, and reduce the crystallinity of β-Ni(OH)₂, which was advantageous to the improvement of the electrochemical activity of nickel hydroxide powder. Electrochemical performances of pasted nickel electrodes using the ball-milled nickel hydroxide as an active material were investigated, and were compared with those of the electrodes prepared with the un-milled nickel hydroxide. Charge/discharge tests showed that the ball-milled nickel hydroxide electrodes exhibited better performances in the charging efficiency, specific discharge capacity, active material utilization and discharge voltage. The improvement of the performances of β-Ni(OH)₂ through ball milling could be attributed to the better reaction reversibility, higher coulombic efficiency, higher oxygen evolution potential and lower electrochemical impedance, as indicated by the cyclic voltammetry and electrochemical impedance spectroscopy studies. Thus, ball milling was an effective method to modify the physical properties and enhance the electrochemical performances of nickel hydroxide powder for the active material of rechargeable alkaline nickel batteries.     

二氧化铈纳米粒子的制备方法评述

介绍了目前国内外纳米粉体二氧化铈的主要制备方法，其中包括水热晶化法、溶胶-凝胶法、微乳液和均匀沉淀耦合法、均匀沉淀和炭吸附耦合法、模板剂共沉淀法、室温（湿）固相化学反应法、一步熔融盐分解法等。通过对各方法的实验条件、制备工艺、产品性状等探讨研究，分析评述了各方法的应用及其工业化前景，旨在为高附加值稀土材料的研制开发提供方向。     

浸取铝灰制取纳米氧化铝新工艺

介绍了一条回收铝灰中的铝制备纳米氧化铝的新工艺.用硫酸浸取电解铝工业中产生的铝灰,得到硫酸铝溶液,实验研究各参数对浸取过程的影响,得到适宜工艺条件;将硫酸铝溶液和碳酸氢铵反应生成碳酸铝铵沉淀,过滤、洗涤、焙烧碳酸铝铵得氧化铝粉体.实验研究了分散剂类型、分散剂用量、铝盐浓度对氧化铝粒径的影响,得出优化工艺条件.经X射线衍射分析和扫描电镜检测表明所得产品为粒径约70 nm的α-Al2O3.