| 题名 | 原位电化学方法研究炭电极材料在电化学电容器中的储能机理 |
| 作者 | 高继超 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 中国科学院长春应用化学研究所 |
| 导师 | 王宏宇 |
| 关键词 | 电化学电容器 原位方法 储能机理 |
| 中文摘要 | 电化学电容器作为一种清洁高效的储能器件，因具有功率密度高、循环寿命长等诸多突出的优点而受到广泛关注。炭材料是电化学电容器最经典的电极材料，主要通过离子在表面的吸附或层间的插嵌来存储电量。在之前的工作中，我们发现溶剂对离子的吸/脱附、插/脱嵌过程有很大的影响。为了揭示其中的微观机理，我们开展了以下几部分工作： 1、以电化学石英晶体微天平（EQCM）为主要工具，研究了不同浓度NaClO4水溶液中活性炭电极/电解质溶液界面上离子的水合状态。结果表明，随着NaClO4浓度的增加，活性炭电极孔隙中吸附的离子的水合数不断减小。本体溶液中Na+水合数大于电极/溶液界面上的Na+水合数，即Na+在从本体溶液被吸附到活性炭孔隙的过程中发生了去溶剂化。另外，活性炭电极孔隙中Na+的水合数与活性炭负极的比电容有明显的线性关系。 2、利用EQCM研究了5 M NaClO4水溶液中的防冻添加剂（甲醇、乙醇）对Na+在活性炭表面吸附过程的影响。结果表明，甲醇、乙醇分子与Na+形成了溶剂化离子，随Na+一起吸附到了活性炭孔隙中；随着本体溶液中甲醇、乙醇浓度的增加，与吸附到活性炭孔隙中的每个Na+络合的甲醇、乙醇分子越来越多；随Na+吸附到活性炭孔隙中的甲醇、乙醇分子挤占了一定的孔隙，同时降低了双电层的介电常数，从而降低了Maxsorb电极在负电势区的比电容。 3、采用原位X射线衍射（XRD）和EQCM研究了BF4?在EC、GBL、PC中插嵌石墨电极的过程。结果表明，EC抑制了BF4?在石墨层间的插嵌。EC、GBL、PC分子都随BF4?一起嵌入了石墨电极，但嵌入的方式各不相同。同时，BF4?在石墨层间的溶剂化状态与对应的活性炭/石墨电容器的循环性能密切相关。 4、采用非原位XRD和原位Raman研究了ClO4?在EC、GBL、PC中插嵌石墨的过程。非原位XRD的测试结果表明，在PC和GBL中，ClO4?嵌入了石墨中并形成了长程有序的ClO4?-GICs，而且GBL分子极有可能也随ClO4?一起嵌入了石墨层间。而在EC中，ClO4?也嵌入了石墨中但没能形成长程有序的ClO4?-GICs，即EC抑制了ClO4?在石墨层间的插嵌。当提高测试温度时，EC对ClO4?的抑制作用会大大减弱。原位Raman结果还表明ClO4?在EC中插嵌石墨的速度要比在GBL和PC中慢很多，可逆性也差很多。 5、采用原位XRD、原位Raman和EQCM研究了PF6?在GBL中插嵌石墨的过程，并与在PC和EC中的插嵌行为进行了比较。结果表明，GBL对PF6?的插嵌也有抑制作用，尽管要比EC的抑制作用弱。同时，我们还发现PF6?在GBL中与BF4?在EC中的插嵌行为十分相似，这进一步说明GBL与EC的抑制作用在本质上是一样的。与此同时，实验结果再次表明，溶剂对活性炭/石墨电容器的性能具有决定性的影响。 |
| 英文摘要 | As a clean and highly efficient electric storage device，electrochemical capacitors have drawn widespread attention due to their numerous merits, such as high power density, long cycle life etc. Carbon materials are the most classical electrode materials for electrochemical capacitors. The charge storage of carbon materials is mainly by ions’ adsorption on the interfaces or intercalation into graphene layers. In our previous work, solvents were found to have great influence on the adsorption/desorption and intercalation/de-intercalation of ions. In order to throw light on its mechanism, following work has been done by us: (1) Electrochemical Quartz Crystal Microbalance (EQCM) was used to study the mass changes on activated carbon electrodes in various NaClO4 aqueous solutions during the course of ions adsorption into the pores of the electrode. Results indicated the hydration number of ions absorbed into the pores decreased with the concentration increase of NaClO4. The hydration number of Na+ in the bulk solutions is much larger than that in the pores of activated carbon electrodes, which demonstrated desolvation occurred during the migration of Na+ from the bulk solutions into the pores. Moreover, the specific capacitance of activated carbon negative electrodes is linearly dependent on the hydration number of Na+ in the pores of activated carbon electrodes. (2) EQCM was used to investigate the adsorption of Na+ into the micropores of activated carbons in 5 M NaClO4 aqueous solutions with different concentrations of methanol or ethanol. Molecule numbers of methanol or ethanol associated with each Na+ at the interfaces were estimated. Results showed that methanol and ethanol were adsorbed into the micropores together with Na+; the more concentrated methanol and ethanol in bulk solutions, the more molecule numbers of methanol or ethanol associated with each Na+ adsorbed into the pores; methanol and ethanol adsorbed into the pores occupied some space of the micropores and lower the dielectric constant of the double layers, which suppressed the specific capacitance of Maxsorb negative electrodes. (3) in situ XRD and EQCM techniques were adopted to probe the intercalation scenario of solvated BF4? into graphite electrodes in PC, GBL and EC. EC suppresses the insertion of BF4? into graphite. All the solvent molecules co-intercalated into graphite electrodes with BF4?，nevertheless，they are in different ways. Moreover, the solvation states of BF4? were in close relation to the cycle performance of corresponding AC/graphite capacitors. (4) ex situ XRD and in situ Raman were utilized to investigate the intercalation of ClO4? from PC-, GBL-, EC-based electrolyte solutions into graphite electrodes. ex situ XRD measurements showed ClO4? intercalated into graphite electrodes from GBL and PC, and generated ClO4?-GICs with long-range order; GBL co-intercalated with ClO4? into the space between graphene layers. In the EC-based solution, ClO4? also succeeded to insert graphite electrodes, but no ClO4?-GICs with long-range order came into being, which indicated the intercalation of ClO4? was suppressed by EC. Elevating temperature weakened the suppression effect of EC. In situ Raman demonstrated the intercalation of ClO4? from EC was slower and less reversible than that from GBL and PC. (5) in situ XRD, in situ Raman and EQCM were employed to study the intercalation of PF6? from GBL-based solution. The cases of PC- and EC-based solutions were used for comparision. Results proved the intercalation of PF6? was suppressed by GBL, even though the suppression effect of GBL was weaker than that of EC. Moreover, the intercalation behavior of PF6? in GBL was similar to that of BF4? in EC, which further demonstrated the suppression effects of GBL and EC were identical in nature. At the same time, results also proved the crucial effect of solvents on the performance of AC/graphite capacitors. |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ciac.jl.cn/handle/322003/64476]  |
| 专题 | 长春应用化学研究所_长春应用化学研究所知识产出_学位论文 |
| 推荐引用方式 GB/T 7714 | 高继超. 原位电化学方法研究炭电极材料在电化学电容器中的储能机理[D]. 中国科学院长春应用化学研究所. 中国科学院研究生院. 2015. |
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