锌酸钙制备方法和生成机制及锌枝晶的研究

The Study of the Method and Mechanism Their Formation of Calcium Zincate and Zinc Dendrites

作者: 专业:物理化学 导师:杨长春 年度:2010 学位:硕士  院校: 郑州大学

Keywords

Calcium Zincate, electrolysis, calcium carbonate, synthetic mechanism, electrical gravimetric, dendrite Photos

        本论文简要介绍了当前能源严峻形势以及新能源的研究现状,罗列了各种锌基电池的原理、结构、性能特点并加以对比分析,着重介绍了锌基电池中锌镍电池的研究现状及其长期存在的枝晶、形变等瓶颈问题,并总结了前人提出的解决这些问题一些途径。针对锌酸钙作为替代氧化锌的替代系负极材料的研究做了系统的总结和整理,分析了锌酸钙作为负极材料的研究现状,总结了锌酸钙的制备方法,并对锌酸钙的制备合成方法进行了总结分析,优缺点的讨论。在前人的大量研究成果基础上提出了新的研究思路。在锌酸钙的合成方法探索中,本论文总结了以往的固相合成法、球磨合成法、共沉淀合成法、低温固相法、水热合成法等各种合成方法的制备工艺、合成条件,分析了各种方法的优劣所在。尝试将电解合成工艺与锌酸钙化学合成结合起来,成功的在槽压为2-5V,电解电流为1A-3A的电解槽中合成了锌酸钙晶体,并对电解制备的样品进行了表面形貌、化学结构、电化学性能等方面的试验检测,通过检测证实了该样品为锌酸钙且具有良好的电化学性能;在电解法制备锌酸钙的条件探索上,本论文在影响电解合成的各方面进行了系统探索,对阳极室电解液选用氯化钙(CaCl2)、氢氧化钾(KOH)电解液进行了不同浓度条件下的制备探索,并分别在0.5M CaCl2电解液,20 wt%KOH电解液当中合成了粒径在50-100nm的形貌较好的锌酸钙样品;在添加剂的种类和剂量上也进行了研究,发现阳极室和阴极室内分别加入KCl和KNO3添加剂时分别形成0.05mol/L的溶液为宜。针对不同电解条件下制备的样品分别进行了XRD、EDS、TG-DTG、SEM等物象的表征,分析了各种条件下制备的锌酸钙的形貌、纯度、杂质类型等因素;在电化学性能上进行了粉末电极CV、实验电池Charge-Discharge性能的测试,经过测试发现电解制备的锌酸钙氧化还原电位差在90mV左右,具备良好的电化学可逆性,实验电池显示实际比容量最大可达到243.2mAg-1,循环32周后,容量仍然保持在最大容量的90%以上;利用金属锌粉部分取代电解锌酸钙组成的混合电极材料制成的负极制成方形电池进行1C大倍率下充放电试验,140次后电池容量仍然保持在70%以上在锌酸钙制备反应当中就CO2对反应的影响进行了分析研究,成功的利用碳酸钙(CaCO3)和氧化锌(ZnO)为原料在5 wt%-35 wt%KOH溶液当中固相反应合成了锌酸钙样品,并发现在碱性浓度较弱情况下合成锌酸钙速率较慢,生成的锌酸钙形貌偏向正六边形,碱性浓度较大情况下在较短的时间内便可生成四边形锌酸钙;对于不同碱浓度下合成的锌酸钙同样进行了物象表征和电化学性能的检测分析,发现这种条件下固相合成目标产物同样具有良好的晶体形貌和电化学性能。以氧化锌和氢氧化钙为原料在含有不同浓度碳酸钠的溶液当中分别进行反应,并成功的在低于1M的碳酸钠溶液介质当中合成了目标产物锌酸钙。针对锌酸钙的溶解度进行了络合滴定测试分析,发现了锌酸钙的KSP远远小于碳酸钙和氢氧化钙的相应数值,从热力学角度上解释了以碳酸钙、氢氧化钙为原料制备锌酸钙的理论可行性,并在前人研究的基础上,提出了锌酸钙生成机理的离子表达式为Ca2+2Zn(OH)3-+2H2O(?)Ca(Zn(OH)3)2·2H2O。并设计实验进行了推理论证,从理论和实验事实两方面证明了其合理性,得出了CO2及CO32-在一定浓度的情况下不会阻碍锌酸钙的生成的结论。成功的尝试了应用电重量方法测量锌化合物在碱性溶液当中的溶解度,从理论上分析计算了该种方法的可行性,利用实验结果与实际溶解量对比的方法证明了该种方法的准确性,并将其样品测试结果与络合滴定的方法测试结果进行了对比,证实了电重量法在锌的化合物碱溶液溶解度测试应用的实用性。在此基础上对应用该方法对氧化锌样品和不同类型的锌酸钙在不同碱溶液当中的溶解度进行了测试对比,证实了锌酸钙在碱性溶液当中比氧化锌低得多的实验结论,不同类型的锌酸钙在相同浓度的碱性溶液当中溶解度差别不大,六边形锌酸钙比四边形锌酸钙略低,共沉淀方法制备的锌酸钙最小。利用二维晶体生长的实验方法对锌枝晶生长做了简单的研究,对电解质浓度、电解质种类、电流密度等众多因素对锌枝晶的影响做了系统的实验观测,发现在三类电解质当中相同条件下硫酸锌枝晶最为严重,氯化锌析氢最为严重,硝酸锌相对电沉积效果较好;一定浓度范围内高浓度容易枝晶生长;电流密度影响最为复杂,呈抛物线趋势,在局部范围内容易枝晶生成。
    In this paper, it gives us a brief introduction to the energy crisis in today’s world and the urgency of new energy research. It also gives us an overview of cell structure, principles, purpose, advantages and disadvantages of the clean, environmental friendly zinc-based batteries, as well as the current development. It highlights the reasons for the dendrite and deformation problems of zinc negative electrode in the zinc-based batteries especially Ni/Zn battery, and summarizes the solution to the problems. On this basis, it has a further discussion over Calcium Zincate negative material which replace activated ZnO to solve the dendrite and deformation problems, in addition, some innovative research has been done based on the predecessors’research.In the study of the synthesis of Calcium Zincate, this paper summarizes the preparation techniques, synthesis conditions, advantages and disadvantages of various methods such as solid-phase synthesis method, ball milling synthesis, co-precipitation synthesis, low-temperature solid-phase method, hydrothermal synthesis method, and so on. We boldly combined the electrolytic synthesis with the chemical synthesis of calcium Zincate and successfully synthesized calcium Zincate crystals in the electrolytic cell, whose trough voltage is between 2V and 5V and the trough current is 1A to 3A.The samples have been confirmed as Calcium Zincate and having a good electrochemical performance by the tests about surface morphology, chemical structure, electrochemical properties, etc. In order to facilitate commercial batch production of calcium Zincate in the future, we explored systematically of electrolytic preparation of calcium Zincate, including:the type of electrolyte, the concentration of electrolyte, the current density, the cell voltage, the temperature in electrolyzer, the length of time and many other factors that may affect the synthesis. Based on the above, we analyzed and summarized the optimal conditions for electrolytic synthesis, that is, the anode chamber electrolyte we selected is the 0.5M CaCl2 or the 20 wt% KOH solution as the electrolyte,125mA/cm2 as electrolytic current density,6h as appropriate length of time, we get the good quadrilateral crystal.we have a study in the electrolyte additives too,and get a conclusion that the the most appropriate anode electrolyte additives and the cathode electrolyte additives are 0.05M KC1 and 0.05M KNO3.while the temperature makes little difference.The as-synthesized calcium zincate was examined by X-ray powder diffraction pattern, scanning electron microscope, energy dispersive X-ray, and thermogravimetric test. The electrochemical performance of this material was measured by cyclic voltammetry and galvanistatic charge-discharge test showing a good reversibility, a high specific capacity and a good cycling durability.the redox potential difference is about 90mV, the specific capacity can reach 243.2mAhg-1.After the 32th cycle,the specific capcity can retain above 90% of the maximum discharge specific capacity.The Influence of CO2 during the reaction that the preparation of the zincate calcium was analyzed and studyed.we succeed synthesize the zincate calcium with ZnO and CaCO3 in 5 wt %~35 wt % KOH solution.and in the weak alkaline solution the crystal is trend to hexagon crystal,in the strong alkaline solution the production is quadrilateral crystal. We take a lot of tests with this kind of solid powders,and find this powder has good morphology and well electrochemical performance. We take an experiment with ZnO and Ca(OH)2 as reactants in a solution which contain different concentration of CO3-,and succeed synthesis the zincate calcium below the 1M CO3-. The Ksp of zincate calcium also be tested by titration method. Base on the previous research,we propose a new reaction mechanism of zincate calcium.which is expressed as: Ca2++2Zn(OH)3-+2H2O(?)Ca(Zn(OH)3)2·2H2O. In the end,we get the conclusion that the presence of the CO2 and CO3- in certain concentration can’t obstruct the target product.In this paper, an innovation has been carried out in the measurement of solubility of ZnO and Calcium Zincate samples in alkaline solution and electrical gravimetric has been used as method of measurement. After the feasibility of the electric gravimetric method can be proved, the author tested and compared ZnO and Calcium Zincate and the solubility of Calcium zinc samples with different morphologies and preparation methods were compared at the same temperature,the result shows the fact that the solubility of calcium zincate is smaller than ZnO, the solubility of Hexagon calcium zincate is smaller than quadrilateral one.At this late stage of the experiment, the author have studied the factors that have influence on zinc dendrite, such as the concentration of metal solution, the current size and types of solution anions,at the same time recorded experimental photos with digital microscope, and analyzed the results,then obtained a few simple rules.
        

锌酸钙制备方法和生成机制及锌枝晶的研究

摘要4-6
Abstract6-8
目录9-11
第一章 综述11-20
    1.1 能源危机及新能源研究现状11-12
    1.2 锌基电池的分类及特点对比12-14
    1.3 锌镍电池研究现状及存在的问题和解决途径14-17
        1.3.1 国内外锌镍电池研究现状14-15
        1.3.2 锌镍电池存在的问题15-16
        1.3.3 改善锌镍电池的有效途径16-17
    1.4 锌酸钙的研究现状17-18
        1.4.1 溶液反应法17-18
        1.4.2 微波水热法18
        1.4.3 固相球磨法18
        1.4.4 悬浮液反应法18
    1.5 本论文研究思路及主要研究内容18-20
第二章 实验研究内容及方法20-28
    2.1 实验药品和实验仪器20
        2.1.1 主要实验药品20
        2.1.2 主要实验检测仪器20
    2.2 电解法制备锌酸钙20-22
        2.2.1 电解合成法20-21
        2.2.2 以CaCl_2为阳极室电解液电解合成锌酸钙21
        2.2.3 不同浓度的KOH溶液为阳极室电解液电解合成锌酸钙21
        2.2.4 阳极室添加不同钙反应物电解合成锌酸钙21-22
    2.3 以碳酸钙为反应物固相法合成锌酸钙22
        2.3.1 用碳酸钙和氧化锌在不同浓度的碱溶液中制备锌酸钙22
        2.3.2 氢氧化钙和氧化锌在含有不同碳酸钠浓度的苛性溶液中反应制备锌酸钙22
    2.4 不同制备方法制得的锌酸钙的表征22-23
        2.4.1 锌酸钙样品的粉末X射线衍射检测22
        2.4.2 锌酸钙样品EDS测试22-23
        2.4.3 锌酸钙样品的差热-热重检测23
    2.5 电重量方法测碱溶液中锌化合物的溶解度23-24
        2.5.1 电重量方法及恒流电解法23-24
        2.5.2 电重量方法测锌盐溶解性可行性的证明实验24
        2.5.4 电重量方法测氧化锌在不同碱溶液当中的溶解度24
        2.5.5 电重量方法测不同制备方法获得的锌酸钙的溶解度24
        2.5.6 锌酸钙的K_(SP)的测量24
    2.6 锌酸钙的电化学性能测试24-27
        2.6.1 锌酸钙样品的循环伏安实验25
        2.6.2 锌酸钙简易方形电池实验25-26
        2.6.3 锌酸钙圆柱电池性能测试26-27
    2.7 锌枝晶的初步探索27-28
        2.7.1 不同浓度锌盐溶液下锌枝晶的研究27
        2.7.2 电流密度大小对锌枝晶影响的研究27-28
第三章 实验结果及讨论28-58
    3.1 电解法制备锌酸钙的实验结果及讨论28-39
        3.1.1 电解制备样品的表征及分析28-33
        3.1.2 电解制备锌酸钙电化学性能测试33-37
        3.1.3 电解制备锌酸钙实验条件的讨论37-38
        3.1.4 电解法制备工艺其他制备方法的比较38-39
    3.2 碳酸钙固相法合成锌酸钙的实验结果及讨论39-46
        3.2.1 碳酸钙固相法合成固体粉末样品的表征及分析39-43
        3.2.2 碳酸钙固相法合成锌酸钙样品的充放电化学测试结果及讨论43-46
    3.3 锌酸钙生成机理的讨论46-49
        3.3.1 锌酸钙K_(SP)值测试实验结果与讨论46-47
        3.3.2 饱和与非饱和氧化锌的大量浓碱溶液当中反应结果与讨论47-48
        3.3.3 碳酸根离子对锌酸钙生成的影响48
        3.3.4 锌酸钙生成机理假设及论证48-49
    3.4 电重量方法测碱溶液中锌化合物的溶解度的结果与讨论49-54
        3.4.1 电重量法可行性实验结果与讨论49-52
        3.4.2 电重量法测试不同浓度碱溶液中氧化锌ZnO的溶解度结果与讨论52
        3.4.3 电重量法测试不同碱浓度下锌酸钙的溶解度结果与讨论52-53
        3.4.4 不同锌酸钙样品溶解度对比53-54
    3.5 锌枝晶实验结果及讨论54-58
        3.5.1 锌离子浓度对锌枝晶生长的影响54-55
        3.5.2 锌离子对应阴离子种类对锌枝品生成的影响55-56
        3.5.3 电流大小对锌枝品生长的影响56-58
第四章 结论与展望58-60
    4.1 主要结论58-59
    4.2 展望59-60
参考文献60-65
致谢65
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