纳米（氢）氧化镍的制备及其电化学性能

【作者】 段浩；

【导师】 刘开宇；

【作者基本信息】 中南大学 ， 应用化学， 2009， 硕士

【摘要】 本文在全面综述国内外Ni（OH）₂研究进展的基础上,通过微乳法和微乳/溶剂热法制备了纳米Ni（OH）₂和NiO。采用扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、红外（IR）、热重（TG）等分析手段对产物的形貌及结构进行了表征,初步探讨了Ni（OH）₂的生长机理,并对Ni（OH）₂在MH/Ni电池和NiO在AC/NiO电容器上的电化学性能进行了研究。以TX-100/正己醇/正庚烷/水所形成的微乳液为反应体系,通过微乳法得到了无规则、弱结晶性的六方β-Ni（OH）₂。当ω=10时,Ni（OH）₂电极的0.2C最大放电比容量为196.5 mAh·g^-1,掺杂7%的CoO后增至234.6 mAh·g^-1,电化学性能优于共沉淀和包覆Co（OH）₂两种方式。140℃水热处理1 h后,电极的0.2C放电比容量增至259.2 mAh·g^-1。,且C_1C/C_0.2C和100次循环（1C）放电比容量保持率分别达到89.8%和81.2%。溶剂热反应后,Ni（OH）₂的结晶性提高、粒径增大,具有片状、棒状和纺锤状三种形貌特征。溶剂热反应不改变电极的放电比容量与ω值的变化趋势。随着溶剂热反应时间的延长,电极的高倍率放电性能提高。140℃溶剂热反应18 h时,电极的0.2C最大放电比容量为279 mAh·g^-1,较未溶剂热时提高了44.4 mAh·g^-1。循环伏安和电化学阻抗表明,此时电极的可逆性最好、扩散系数最大和电荷转移电阻最低。以CTAB/正丁醇/正庚烷/水所形成的微乳液为反应体系,通过微乳法得到了针状、六方β-Ni（OH）₂,其长度约为20-40 nm。当ω=28时,Ni（OH）₂电极的0.2C最大放电比容量为222.6 mmh·g^-1,掺杂7%的CoO后增至285.3 mAh·g^-1,电化学性能明显优于共沉淀和包覆Co（OH）₂两种方式。溶剂热反应后,Ni（OH）₂的结晶性提高;具有片状和棒状结构,粒径分别为80-100 nm和100-160 nm。电极的放电比容量与ω值的变化趋势不变,但是放电比容量明显降低。140℃溶剂热反应12 h时,电极的0.2C最大放电比容量为234.6 mmh·g^-1,较未溶剂热时降低了50.7 mAh·g^-1。循环伏安和电化学阻抗表明,此时电极的扩散系数最大、电荷转移电阻最低,电极受电荷转移控制。探讨了Ni（OH）₂的生长机理,推测Ni（OH）₂经表面活性剂诱导、自组装形成棒状和片状结构。通过300℃煅烧由TX-100/正己醇/正庚烷/水微乳体系得到的Ni（OH）₂,得到了无规则、立方NiO。随着煅烧温度的升高,NiO的粒径逐渐增大,在煅烧温度低于600℃时的晶体生长活化能为10.72 KJ·mol^-1。TG曲线分为三部分,分别对应着Ni（OH）₂中的吸附水、残余表面活性剂和晶格水的失去。DSC分析表明,Ni（OH）₂的热分解温度为258℃。在100 mA·g^-1电流密度下,AC/NiO电容器的比电容、比功率和比能量分别为104.4 F·g^-1、75 W·kg^-1和65.3 Wh·kg^-1,200次循环后比电容保持率为87.7%。在0-1.5 V电压范围内,AC/NiO电容器具有良好的电容特性。电化学阻抗结果表明,NiO电极具有较低的电荷转移电阻和良好的电化学电容行为。更多还原

【Abstract】 In this paper, based on the review of the research and development of Ni（OH）₂, nanometer Ni（OH）₂ and NiO were synthesized by micro-emulsion method and micro-emulsion/solvent-thermal method. The morphology and structure of the products were characterized by means of scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, infrared absorption spectroscopy （IR） and thermo-gravimetry （TG）. The growth mechanism of Ni（OH）₂ was investigated preliminarily, the electrochemical properties of Ni（OH）₂ in the MH/Ni and NiO in the AC/NiO capacitor were also studied.The hexagonalβ-Ni（OH）₂, which had irregular morphology and poor crystallinity, was prepared in micro-emulsion solution formed by TX-100/n-hexanol/ n-heptane/water. Whenω=10, the Ni（OH）₂ electrode exhibited the maximum discharge specific capacity 196.5 mAh·g^-1 at 0.2C, and the specific capacity reached to 234.6 mAh·g^-1 after doping CoO with the content of 7%. The electrochemical properties were superior to Ni（OH）₂ prepared by co-precipitation and coated with Co（OH）₂. When hydrothermally treated for 1 h at 140℃, the discharge specific capacity of the Ni（OH）₂ electrode was 259.2 mAh·g^-1, the capacity retention of C_1C/C_0.2C and 100 cycles at 1C were 89.8% and 81.2% respectively. After solvent-thermal reaction, the crystallinity and diameter of the Ni（OH）₂, which had flake, rod and spindle morphologies, were increased, and the law betweenωvalues and discharge specific capacity was not changed. As the time of solvent-thermal reaction was prolonged, the high-rate discharge ability of the Ni（OH）₂ electrode was improved. When the solvent-thermal reaction was 18 h at 140℃, the Ni（OH）₂ electrode showed the maximum discharge specific capacity 279 mAh·g^-1 at 0.2C, and was enhanced by 44.4 mAh·g^-1. CV and EIS tests indicated that the Ni（OH）₂ electrode had the best reversibility, the highest diffusion coefficient and the lowest charge transfer resistance.The hexagonalβ-Ni（OH）₂, whose morphology was needle with the diameter of 20-40 run, was prepared in micro-emulsion solution formed by CTAB/n-butanol /n-heptane/water. Whenω=28, the Ni（OH）₂ electrode exhibited the maximum discharge specific capacity 222.6 mAh·g^-1 at 0.2C, and increased to 285.3 mAh·g^-1after doping CoO with the content of 7%. The electrochemical properties was superior to Ni（OH）₂ prepared by co-precipitation and coated with Co（OH）₂. The crystallinity of the Ni（OH）₂ was increased after solvent-thermal reaction. The diameter of flake and rod Ni（OH）₂ was 80-100 nm and 100-160 nm, respectively. The regularity betweenωvalues and discharge specific capacity was not changed, but the discharge specific capacity was decreased significantly. When solvent-thermal reaction was 12 h at 140℃, the Ni（OH）₂ electrode exhibited the maximum discharge specific capacity 234.6 mAh·g^-1 at 0.2C, and was decreased by 50.7 mAh·g^-1. CV and EIS tests showed that the Ni（OH）₂ electrode had the highest diffusion coefficient and the lowest charge transfer resistance, the electrode was controlled by charge transfer resistance. The growth mechanism of Ni（OH）₂ was investigated. And we inferred the structure of rod and flake Ni（OH）₂ was formed by the induction of surfactant and self-assemble.NiO with cubic crystalline and irregular shape was prepared by calcining Ni（OH）₂ at 300℃. The Ni（OH）₂ was made by micro-emulsion method using TX-100/n-hexanol/n-heptane/water. As the calcination temperature was increased, the diameter of NiO increased gradually. The activation energy for nanocrystallite growth was 10.72 kJ·mol^-1. The TG curve was divided into three segments, which corresponded to the loss of adsorbed water, residual surfactant and crystal water of Ni（OH）₂, respectively. The result of DSC curve showed that the thermal decomposition temperature was 258℃.The specific capacitance, power and energy of AC/NiO capacitor were 104.4 F·g^-1, 75 W·kg^-1 and 65.3 Wh·kg^-1 and the capacity retention was 87.7% after 200 cycles. AC/NiO capacitor exhibited excellent capacitance performance with the potential range from 0 to 1.5 V. The EIS result indicated that the NiO electrode had lower charge transfer resistance and better electrochemical capacitance performance.更多还原