钒电池用质子交换朠的制备及其性质

IMR OpenIR

	钒电池用质子交换朠的制备及其性质
	贾传坤
学位类型	博士
导师	严川伟 ; 刘建国
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	腐蚀科学与防护
关键词	钒氧化还原液流电池质子交换膜 Nafion 磺化聚醚醚酮纳米碳管 Vanadium Redox Flow Battery Proton Exchange Membrane Nafion Sulfonated Poly(Ether Ether Ketone) Nanotubes
摘要	"全钒氧化还原液流电池（钒电池）是一种新型的大规模电化学储能装置，作为最具潜力解决风能、太阳能等新能源发电过程不连续、不稳定等难题的配套储能装置，以其储能规模大、循环寿命长等优点，成为目前大规模储能装置研究的热点。钒电池正负极电解液分别为含VO2+/VO2+与V2+/V3+离子的硫酸水溶液。其中，质子交换膜是目前制约钒电池产业化的关键材料之一。它的作用是传递质子以完成电池反应，同时阻隔正负极电解液渗透以减少自放电现象。理想的质子交换膜应具备质子传导率高、化学稳定性好、机械性能好、钒离子渗透少以及成本低廉等优点。目前，钒电池应用最广的全氟磺酸型Nafion 系列膜，具有质子传导率高，化学稳定性好等优点。但是其高的钒离子渗透和高昂的价格，阻碍其在钒电池商业化中的应用。因此，开发阻钒性能好且成本低廉的质子交换膜成为钒电池研究的重点。本论文以探索开发性能优良成本低廉的钒电池用磺化聚醚醚酮基质子交换膜为核心，采用溶液浇铸法，制备不同结构的质子交换膜。对这几类质子交换膜机械性能、溶胀性、含水率、微观结构、阻钒性能、电池性能进行系统测试和分析，主要研究结论如下： 1：通过控制反应条件制备不同磺化度的磺化聚醚醚酮。对不同磺化度磺化聚醚醚酮性能进行研究对比，结果显示磺化度在60%左右的磺化聚醚醚酮适合钒电池的应用。 2：成功制备不同功能化纳米碳管改性的磺化聚醚醚酮复合膜。功能化纳米碳管在复合膜中分散均匀。磺化聚醚醚酮/羧基化多壁纳米碳管复合膜具有良好的机械性能，溶胀性能，含水率。羧基化纳米碳管的加入，能够减小钒离子渗透通道的尺寸，从而提高复合膜的阻钒性，减少复合膜在单个钒电池中自放电现象，使其充电容量衰减降低，电池库仑效率、能量效率均高于装有Nafion 212 膜的单个钒电池。磺化聚醚醚酮/羟基化纳米碳管复合膜机械性能和含水率均比磺化聚醚醚酮膜提高很多，这种复合膜具有良好的阻钒性、充电容量衰慢、库仑效率高、能量效率高等优点。 3：以聚丙烯隔膜作为中间增强层，镶嵌了磷钨酸的磺化聚醚醚酮为基膜，制备的三明治结构磺化聚醚醚酮/聚丙烯/磷钨酸复合膜，这类复合膜三层之间结合紧密，具有良好的机械性能。磺化聚醚醚酮/磷坞酸渗入到聚丙烯隔膜内部孔隙中，能够降低钒离子在复合膜中通道的尺寸，进而提高复合膜的阻钒性能。单个钒电池性能测试显示，复合膜具有良好的库仑效率和能量效率。充电容量衰减远低于装有Nafion 212膜的单个钒电池。"
其他摘要	"Vanadium redox flow battery (VRB) is attractive for its potential to solve the intermittence of wind and solar energy by serving as a large-scale electrochemical energy storage system due to its various advantages particularly such as high storage capacity, long cycle life, quick response time and flexible design. VRB employs V (II)/V (III) and V (IV)/V (V) redox couples in its negative and positive electrolytes, respectively. In the VRB, a proton exchange membrane is a critical component that separates the anode and cathode electrolytes while allowing the transport of ions. An ideal membrane for a VRB should possess high proton conductivity, good chemical stability, high tensile strength, low permeability for vanadium ions and low cost. Among ion exchange membranes, perfluorosulfonic acid (PFSA) such as Nafion (DuPont) is most commonly used due to their high chemical stability and proton conductivity. However, PFSA membranes usually suffer from high cost and especially high permeability of vanadium ions when used in VRB. In order to reduce the migration of V ions, many approaches such as inorganic doping, surface modification, and layering have been put forward to modify the Nafion membranes. Although some modified Nafion membranes were found to have lower vanadium species migration than the pure ones, they are far too expensive to be afforded, hence limit their commercial application for VRB systems. Therefore, it is of crusial importance for the researchers to develop a proton exchange membrane with reduced vanadium ions permeation as well as low cost. Resent works have shown that polyether ether ketone (PEEK) is of particularly significant promise as it possesses a good thermal stability, appropriate mechanical properties and some conductivity when sulfonated. It has been shown that sulfonated polyether ether ketone (SPEEK) has been widely used in fuel cell as a proton exchange membrane due to its excellent properties such as good mechanical properties, low cost and low methanol crossover. In this regard, SPEEK shows potential for VRB applications with better vanadium selectivity and low cost. However, the chemical stability and the long term stability of these membranes for VRB applications still need to be further improved. Especially for the membranes with a high degree of sulfonation (DS), their mechanical properties tend to progressively deteriorate, which would lower their long term stability. As to the membranes with low DS, their mechanical property is suitable, yet their proton conductivity does not suffice the requirements for VRB. The core for this thesis is to exploit proton exchange membrane with good performance and low cost for VRB applications. In order to prepare a SPEEK membrane with suitable DS used in VRB, some composite membranes based on the traditional SPEEK have been prepared and characterized. The simple SPEEK membranes have been characterized concerning their mechanical property, swelling ratio, water uptake, area resistance and vanadium ions permeability. Functional carbon nanotubes (CNTs)-modified SPEEK membranes have been prepared. Novel sandwich-type sulfonated poly(ether ether ketone)/tungstophosphoric acid/polypropylene and sulfonated poly(ether ether ketone)/ polypropylene / perfluorosulfonic acid layered composite membranes have been developed and polypropylene for a Ni-MH battery is used to enhance the mechanical strength of the membranes. The mechanical property, proton conductivity, swelling ratio, water uptake, microstructure and permeability of vanadium ions of the above-mentioned membranes have been investigated and the performance of vanadium redox flow battery single cell with these membranes are also measured. The main conclutions are shown as follows: 1: Varying the reaction temperature, the reaction time and the ratio of PEEK can control the DS. The swelling ratio, the water uptake and the permeability of vanadium ions increase continuously with the DS accompany by the reduction of the mechanical property and area resistance. The SPEEK membranes with high and low DS are both unsuitable for VRB application due to its weak mechanical property and high area resistance, respectively. With the DS around 60%, the SPEEK membranes are suitable for VRB application due to their acceptable mechanical strength and proton conductivity. 2: Membrane with low capacity loss is prepared for their application in VRB. It is based on a traditional SPEEK membrane, which is embedded with short-carboxylic multi-walled carbon nanotubes and short- hydroxylation multi-walled carbon nanotubes, respectively. Results show that the functional carbon nanotubes particles are well dispersed in the SPEEK membrane and functional carbon nanotubes-modified SPEEK membranes present good mechanical strength, high water uptake, low swelling ratio. The permeability of vanadium ions of modified SPEEK membranes is lower than that of Nafion 212 membrane, which will give rise to a reduction in the charge capacity loss, self-discharge and consequently result in high columbic efficiency and energy efficency. This may result from a decrease in the pore size since CNTs particles being embedded in the hole of the SPEEK membrane, and thus reduce the channel size for V(IV) ions diffusion. 3: In order to increase the mechanical strength and reduce the vanadium ions permeability of membranes used in VRB, a novel sandwich-type SPEEK/tungstophosphoric acid/polypropylene layered composite membrane (S/T/P) has been developed and polypropylene for a Ni-MH battery is used to enhance the mechanical strength of the membranes. The vanadium ion permeability of the S/T/P composite membrane was significantly lower than that of a Nafion 212 membrane. A VRB single cell with an S/T/P membrane has higher columbic efficiency, energy efficency and a lower self-discharge rate than the cell with a Nafion 212 membrane. A sandwich-type SPEEK/ polypropylene (PP) / perfluorosulfonic acid (PFSA) composite membrane (S/P/P) consisting of a PFSA layer, the transition central layer and a layer of SPEEK has been prepared by solution casting. The PFSA layer and the SPEEK layer were tightly linked with improved interface stability due to the effect of the porous PP layer. The PFSA layer of the S/P/P membrane serves as a shield preventing the oxidation degradation of the composite membrane by VO2+ ions in the positive half-cell electrolyte of the VRB while the SPEEK layer is expected to block the vanadium ions permeation. The S/P/P membrane displays much lower vanadium ions permeability compared to Nafion 212 one. The VRB single cell with an S/P/P membrane has higher CE, EE, and a lower self-discharge rate than that with a Nafion 212 membrane. In summary, these novel types of membranes have shown excellent cell performance and are expected to have commercial prospects as a separator for VRB systems."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64502
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	贾传坤. 钒电池用质子交换朠的制备及其性质[D]. 北京. 中国科学院金属研究所,2012.