纳米级氢氧化镍制备及电化学性能研究

介绍了一种通过合成草酸镍,进而生成β型纳米氢氧化镍的新的合成路线,从而达到大幅度提高镍氢电池正极放电容量的目的。使用X射线衍射（XRD）分析产品的晶型结构。从产品谱图中可以得知：由于特征衍射峰的出现可以判定该产品为β型,且由于（001）峰的宽化可以初步判定其为纳米级。通过透射电镜（TEM）可以看出产品粒径和形貌的具体特征,即产品为针状,长度为100～200 nm,直径为10～20 nm。将纳米级氢氧化镍制成电极,经过充放电测试可以发现电容量约为400 mA.h/g,远远高于球形微米级氢氧化镍的放电容量。     

非晶态氢氧化镍复合碳纳米管电极材料的电化学性能

采用快速冷冻化学共沉淀法制备非晶态Ni(OH)2粉体,将其作为电化学活性物质复合碳纳米管合成镍电极材料,研究了其电化学性能. 结果表明,加入碳纳米管有效减少了镍电极的电荷转移电阻,增大了电极反应过程的质子扩散系数. 复合0.5%(w)碳纳米管合成的非晶态氢氧化镍电极材料在1 C充放电制度下,放电终止电压为1.0 V时,其放电比容量高达336.5 mA×h/g,放电中值电压为1.251 V,充放电循环30次,放电比容量保持率为96.74%,表现出较好的高倍率充放电性能.     

氢氧化镍电极的修饰及电化学性能的研究

镍系列二次电池的正极活性物质Ni（OH）2的晶型和镍电极的制备工艺对电池的性能具有较大的影响。文章以镍-氢电池作为对象,着重研究作为电池正极的氢氧化镍电极。通过不同的方法制备电极的活性物质Ni（OH）2,以Co、Zn和稀土作为掺杂剂对电极进行修饰,并对不同掺杂方式构成的电池进行了测试。用金相显微镜来观察Ni（OH）2的外观、颗粒大小;通过恒电流放电曲线比较各电极的放电性能,并通过XRD谱图了解样品的晶型结构。电池性能测试结果表明：采用配位沉淀法制备的Ni（OH）2晶体为最佳;在添加剂方面,Zn、Co、Sm均对镍电极的电化学性能影响较大。     

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％．     

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.     

非晶相氢氧化镍电极材料的研究进展

非晶态材料原子排列无序性强、结构缺陷多,内部含有大量配位不饱和原子和表面活性中心,是理想的高性能电极材料.本文综述了非晶相氢氧化镍电极材料的制备方法,描述了非晶相氢氧化镍作为电极活性材料的电化学特性.提出了非晶相氢氧化镍进一步的研究方向.     

活性镍纳米电极的制备及其电化学性能

针对海水防污技术研究了两种镍电极在海水中的析氢性能.采用交流电在阳极氧化铝(AAO)模板上沉积镍纳米线与化学镀结合的方法制备了镍纳米电极,用机械抛光的方法制备了镍本体电极.用SEM表征了AAO模板与镍纳米线阵列,用XRD表征了两种电极的结构.循环伏安、极化曲线和交流阻抗的测试表明纳米电极具有较大的活性面积,更好的析氢催化活性和更小的析氢反应电阻.尤其在电流密度为100mA/cm2时,纳米电极的极化电位比镍本体电极正移约357mV,表现出更好的析氢性能.     

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。     

石墨毡原位生长TiN纳米棒及其作为钒电池电极的电化学性能研究

利用水热合成和高温退火方法,将氮化钛纳米棒原位生长在石墨毡表面,成功构建了兼具高催化活性和高导电性的碳纤维复合电极材料.用扫描电子显微镜对复合电极的表面形貌和结构进行了表征.利用接触角测试仪对电极表面的浸润性进行了考察.采用三电极体系并通过小幅电位阶跃法和循环伏安法对电极的电化学表面积和电化学性能进行了分析.最后,通过...     

纳米金修饰电极的电化学传感性能研究

在氯金酸(HAuCl₄)溶液中采用电化学沉积的方法,在磨好的玻碳电极(GCE)上沉积金得到金修饰电极(Au/GCE)。采用循环伏安法以、差分脉冲伏安法等电化学分析方法对修饰电极进行性能研究。经实验表明金修饰电极在适当的沉积条件下有比较好的电催化效果,且对邻苯二酚和对苯二酚的检测较为灵敏。     

层间阴离子对铝取代氢氧化镍电化学性能的影响

采用化学共沉淀法制备出层间分别含有SO42-和NO3-的铝取代氢氧化镍样品。利用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)和扫描电子显微镜(SEM)对样品的微观结构和表面形貌进行了分析。采用循环伏安(CV)、交流阻抗(EIS)和充放电测试表征了样品的电化学性能。结果表明,层间含有NO3-的铝取代氢氧化镍比层间含有SO2-的铝取代氢氧化镍具有更好的电化学反应可逆性、更高的质子传递系数和放电比容量。     

Non-equilibrium effects in the nickel hydroxide electrode

The electrochemical reaction Ni(OH)₂=NiOOH+H⁺+e occurring under potentiodynamic conditions in 1 N KOH using complex triangular potential sweep revealed the existence of non-equilibrium effects of both reactant and products which cause the splitting of the anodic current peak already known. By a suitable choice of the perturbation variables, the rate of the chemical change the Ni(OH)₂ species undergoes can be estimated. The reaction presenting the nickel hydroxide electrode is interpreted as two parallel electron transfer steps coupled to two chemical reactions through a square-type reaction model.     

Liquid-phase synthesized mesoporous electrochemical supercapacitors of nickel hydroxide

Electrochemical supercapacitive (ES) properties of liquid-phase synthesized mesoporous (pore size distribution centered ∼12 nm) and of 120 m²/g surface area nickel hydroxide film electrodes onto tin-doped indium oxide substrate are discussed. The amounts of inner and outer charges are calculated to investigate the contribution of mesoporous structure on charge storage where relatively higher contribution of inner charge infers good ion diffusion into matrix of nickel hydroxide. Effect of different electrolytes, electrolyte concentrations, deposit mass and scan rates on the current-voltage profile in terms of the shape and enclosed area is investigated. Specific capacitance of ∼85 F/g at a constant current density of 0.03 A/g is obtained from the discharge curve.     

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.     

The effect of the interlayer anions on the electrochemical performance of layered double hydroxide electrode materials

Both high energy density and high power density are vitally required for new applications such as electric vehicles. Here we present a comparison of two well-crystallised layered double hydroxides, [Ni₄Al(OH)₁₀]OH and [Ni₄Al(OH)₁₀]NO₃, which shows that the former can maintain a better discharge capacity, 294-299 mAh g⁻¹, than the latter, 233-287 mAh g⁻¹ at a current density of 2000 mA g⁻¹ within about 300 cycles, although both electrodes deliver a similar capacity of 326 mAh g⁻¹ at 200 mA g⁻¹ initially. It is believed that both the more watery interlayer space in [Ni₄Al(OH)₁₀]OH than in [Ni₄Al(OH)₁₀]NO₃ and the morphologic changes induced by anion exchange of NO₃⁻ by OH⁻ during electrochemical cycles play key roles in their behaviour.     

Structure and electrochemical properties of nickel hydroxide electrodes with cobalt additives

In this article,cobalt additives are introduced into nickel hydroxide electrodes by two incorporation methods—co-precipitated cobalt hydroxide during the nickel hydroxide synthesis or post-added CoO with nickel hydroxide. The results of X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge tests indicate that (i) the diffraction peaks show a decrease in intensity and increase in the half peak breadths for Ni(OH)₂ with co-precipitated cobalt hydroxide; (ii) the electrochemical activity of nickel hydroxide can be improved by both incorporated cobalt and the effects of post-added CoO are more notable; (iii) CoOOH derived from post-added CoO is not stable in the KOH electrolyte when the potential of the Ni(OH)₂ electrode is lowered and its reduction product may be inactive, thus results in an irreversible capacity loss of nickel-metal-hydride battery after over-discharge-state storage.     

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.