摘要
层状双氢氧化物（LDHs）具有独特的片层结构，可以同时提供双电层电容和法拉第赝电容两种储能机制，有利于提高电容器的比电容值。本文采用水热合成法，以硝酸钴、硝酸锌、硝酸铝和尿素为原料，制备CoZnAl-LDH。探讨了尿素含量、反应温度、反应时间和Co2+、Zn2+金属离子比例对CoZnAl-LDH结构和形貌的影响，以及碱刻蚀时间对CoZnAl-LDH结构及电化学性能的影响。通过XRD、SEM、TEM、FT-IR、BET、EPR、XPS等手段对材料的物相组成及微观结构进行表征，并将其用作电极材料，利用电化学工作站分析了其电化学性能。主要工作及结论如下：
（1）采用水热法制备CoZnAl-LDH，探究了尿素含量、反应温度、反应时间和Co2+、Zn2+金属离子比例等实验条件对CoZnAl-LDH结构和形貌的影响。结果表明：在尿素含量为三价金属离子（Al3+）的10倍，反应温度为120℃，反应时间为12 h，Co2+：Zn2+=2:1时，通过水热法直接合成出三维结构的CoZnAl-LDH。（2）探索了碱刻蚀作用对三元层状双氢氧化物结构与性能的影响。采用水热法制备的CoZnAl-LDH，利用5 mol·L-1的NaOH碱性溶液对材料进行不同时间的刻蚀。结果表明：碱刻蚀可以去除LDH层板间部分金属离子，造成缺陷的产生；碱刻蚀可以改变Co2+的配位环境，降低了带隙，提高LDH的导电性，并导致晶体的部分结构改变；碱刻蚀提高了LDH主体层板中Co2+/Co3+与OH-之间可逆反应的电化学活性。
（3）碱刻蚀CoZnAl-LDH的电化学性能。通过交流阻抗、循环伏安、恒流充放电等测试方法，分析了其电化学性能。三电极测试结果表明：CoZnAl-LDH刻蚀8 h后在6 A·g-1的电流密度下具有601 F·g-1的优异比电容和良好的循环稳定性（4000次循环后电容保持率约为92.3 %）。未刻蚀和刻蚀16 h后，其电化学性能较差，在6 A·g-1的电流密度下分别为304 F·g-1（4000次循环后电容保持率约为76.9 %）和383 F·g-1（4000次循环后电容保持率约为66.3 %）。
（4）刻蚀8 h后的CoZnAl-LDH//AC混合型超级电容器的电化学性能。以刻蚀8 h后的CoZnAl-LDH样品为正极材料、以活性炭（AC）为负极材料，水性电解液为2 mol·L-1的KOH。结果表明：刻蚀8 h后的CoZnAl-LDH//AC在2 mA·cm-2的电流密度下，比电容为103.4 F·g-1，能量密度为36.75 Wh·kg-1，功率密度为0.4 kW·kg-1；当电流密度达到20 mA·cm-2时，比电容为86.6 F·g-1，能量密度为30.78 Wh·kg-1，功率密度为4 kW·kg-1，比电容保持率为83.7 %。其在6 mA·cm-2恒流充放电8000圈的电容保持率为72.7 %。
关键词：层状双氢氧化物，碱刻蚀，电化学性能，混合型超级电容器
Abstract
Layered double hydroxides (LDHs) as layered material with unique lamellarstructure and the redox of transition metal ions in metal hydroxide layer are promising for next-generation supercapacitors in that
electrical double layered capacitance and faradaic pseudocapacitance can be simultaneously acquired.
CoZnAl-LDH was synthesized by hydrothermal method with cobalt nitrate, zinc nitrate,aluminum nitrate, urea as raw materials. The effect of urea content, reaction temperature, reaction time and the proportion of Co2+and Zn2+metal ions on the structure and morphology of CoZnAl-LDH, and alkali etching on the structure and electrochemical performance of CoZnAl-LDH were discussed. The XRD、SEM、TEM 、FT-IR、BET、EPR、XPS and electrochemical workstation were employed to characterize the materials. The results are as follows:
(1) CoZnAl-LDH was prepared by hydrothermal method. The influence of experimental conditions such as urea content, reaction temperature, reaction time and the ratio of metal ions such as Co2+and Zn2+ on the structure and morphology of CoZnAl-LDH was investigated. The results showed that three-dimensional structure of CoZnAl-LDH was directly synthesized by hydrothermal method when the urea content was 10 times that of trivalent metal ions (Al3+), reaction temperature was 120°C, reaction time was 12 h, and Co2+:Zn2+=2:1.
(2) The effects of alkaline etching on the structure and properties of the ternary layered double hydroxi
des were explored. CoZnAl-LDH prepared by the hydrothermal method was used to etch the materials at different times with 5 mol·L-1 NaOH alkaline solution. The results show that alkali etching can remove some metal ions between LDH laminates and cause defects. Alkali etching can change the coordination environment of Co2+, reduce the bandgap, increase the conductivity of LDH, and lead to partial structural changes in the crystals. Alkali etching enhances the electrochemical activity of the reversible reaction between Co2+/Co3+ and OH- in the LDH host laminate.
(3) Alkaline etching of the electrochemical properties of CoZnAl-LDH. The electrochemical performance was analyzed by the test methods of AC impedance, cyclic voltammetry, and galvanostatic charge and discharge. The results of the three-electrode test show that the CoZnAl-LDH has an excellent specific capacitance of 601 F·g-1 and good cycle stability at a current density of 6 A·g-1 after 8 h etching
(ca.92.3% capacitance retention after 4000 cycles). Unetched and etched for 16 h, the electrochemical performance was poor, with 304 F·g-1 at a current density of 6 A·g-1 (ca.76.9% capacitance retention after 4000 cycles) and 383 F·g-1(ca.66.3% capacitance retention after 4000 cycles).
(4) Electrochemical performance of CoZnAl-LDH//AC hybrid supercapacitors after etching for 8 h. The
CoZnAl-LDH sample after etching for 8 h was used as a positive electrode material and activated carbon (AC) as a negative electrode material. The aqueous electrolyte was 2 mol·L-1KOH. The results show that the specific capacitance of the current density of 2 mA·cm-2 is 103.4 F·g-1, the energy density is 36.75 Wh·kg-1, and the power density is 0.4 kW·kg-1; when the current density reaches 20 mA·cm-2, the specific capacitance is 86.6 F·g-1, the energy density is 30.78 Wh·kg-1, and the power density is 4 kW·kg-1(The Specific capacitance retention rate is 83.7%). The capacitance retention rate of 8000 cycles at 6 mA·cm-2constant current charge and discharge was 72.7%.
Key words: Layered double hydroxide, alkaline etching, electrochemical performance, hybrid supercapacitor
目录
摘要 ............................................................................................................................................ I Abstract ..................................................................................................................................... II 第一章绪论 .. (1)
1.1超级电容器概述 (1)
1.1.1 超级电容器特性及应用前景 (1)
1.1.2 超级电容器的分类及储能机理 (2)
1.1.3 超级电容器电极材料 (3)
1.2层状双氢氧化物 (4)
1.2.1层状双氢氧化物的结构 (4)
1.2.2层状双氢氧化物的主要性质 (5)
1.2.3层状双氢氧化物的主要应用 (5)
1.2.4层状双金属氢氧化物的制备方法 (7)
1.2.5层状双金属氢氧化物在超级电容器中的应用 (8)
1.3本论文的立题依据、研究内容及研究意义 (9)
1.3.1 本论文的立题依据 (9)
1.3.2 本论文的研究意义 (10)
1.3.3 本论文的研究内容 (11)
第二章 CoZnAl-LDH合成条件的探究 (12)
2.1 引言 (12)
2.2 实验原料及仪器 (12)
2.3 材料的制备 (13)
2.4 材料的表征方法 (14)
2.5 结果与讨论 (15)
2.5.1 尿素含量对CoZnAl-LDH结构的影响 (15)
2.5.2 反应温度对CoZnAl-LDH结构的影响 (17)
2.5.3 反应时间对CoZnAl-LDH结构的影响 (19)
2.5.4 Co2+、Zn2+不同比例对CoZnAl-LDH结构的影响 (21)
2.6 本章小结 (22)
第三章碱刻蚀作用对CoZnAl-LDH结构及性能的影响 (23)
3.1 引言 (23)
3.2 实验原料及仪器 (23)
3.3材料的制备 (24)
3.4 材料的表征方法 (25)
3.5 结果与讨论 (26)
3.5.1 碱刻蚀CoZnAl-LDH材料碱源浓度的影响 (26)
3.5.2 碱刻蚀CoZnAl-LDH材料的物相与微观结构分析 (27)
3.5.3 碱刻蚀CoZnAl-LDH材料的FT-IR与Raman图谱分析 (29)
3.5.4碱刻蚀CoZnAl-LDH材料的电子顺磁光谱（EPR）分析 (30)
3.5.5碱刻蚀CoZnAl-LDH材料的比表面积及孔结构分析 (31)
3.6本章小结 (32)
第四章碱刻蚀作用对CoZnAl-LDH电化学性能的影响 (33)
4.1 引言 (33)
4.2 电极材料的制备 (33)
4.3 碱刻蚀CoZnAl-LDH材料的电化学测试 (34)
4.3.1 碱刻蚀CoZnAl-LDH材料的电化学性能分析 (35)
4.3.2碱刻蚀CoZnAl-LDH材料的XPS数据分析 (38)
4.3.3碱刻蚀CoZnAl-LDH材料的导电性和UV-vis光谱分析 (40)
4.3.4刻蚀8 h后的CoZnAl-LDH//AC非对称超级电容器（ACS）的性能研究 (41)
4.4 本章小结 (43)
第五章结论与展望 (44)
5.1 总结 (44)
5.2 展望 (45)
参考文献 (46)
个人简介和攻读硕士期间的研究成果 (52)
reaction研究
致谢 (53)

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。