本文關(guān)鍵詞：磺化聚酰亞胺膜在全釩液流電池中的應(yīng)用及穩(wěn)定性研究　出處：《西南科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 磺化聚酰亞胺 膜 全釩氧化還原液流電池 降解機(jī)理 殼聚糖

【摘要】：全釩氧化還原液流電池(VRFB)是一種新型綠色二次電池,具有容量可調(diào)、可深度充放電、效率高、操作維護(hù)簡(jiǎn)單、使用壽命長(zhǎng)、成本低廉等優(yōu)點(diǎn)。隔膜是VRFB的三大組件之一,起分隔正負(fù)極電解液以防止電池自放電、讓質(zhì)子透過(guò)以導(dǎo)通整個(gè)回路的作用。理想的VRFB隔膜應(yīng)該具有質(zhì)子傳導(dǎo)率及化學(xué)/電化學(xué)穩(wěn)定性高、釩滲透及價(jià)格低等特點(diǎn)。目前廣泛使用的VRFB隔膜是全氟磺酸膜如美國(guó)杜邦公司生產(chǎn)的Nafion系列膜,其質(zhì)子電導(dǎo)率及化學(xué)/電化學(xué)穩(wěn)定性均較高,但釩滲透及價(jià)格均過(guò)高。因此,必須研發(fā)新型隔膜,使之滿足在VRFB大規(guī)模產(chǎn)業(yè)化推廣應(yīng)用中的迫切需求。在眾多的面向VRFB應(yīng)用的新型隔膜研發(fā)中,合成并制備非氟高分子膜是一個(gè)重要的研究方向。與Nafion膜相比,非氟高分子膜通常具有釩滲透低、價(jià)格低的優(yōu)勢(shì)。然而,非氟高分子膜的穩(wěn)定性問(wèn)題是制約其在VRFB中長(zhǎng)期使用的瓶頸。因此,迫切需要進(jìn)行非氟高分子膜在VRFB中的降解機(jī)理研究,以闡明導(dǎo)致此類膜穩(wěn)定性下降的根本原因。本文以磺化聚酰亞胺(SPI)膜為非氟高分子膜代表,通過(guò)原位和離線測(cè)試方法研究其在VRFB中的降解機(jī)理。對(duì)SPI膜及其低聚物在降解前后的形貌、結(jié)構(gòu)、機(jī)械性能、理化特性等進(jìn)行表征。光學(xué)照片和SEM圖像結(jié)果顯示,經(jīng)過(guò)原位降解的SPI膜比經(jīng)過(guò)離線降解顯示出更嚴(yán)重的表面形貌破壞。經(jīng)不同浸泡液浸泡后,SPI膜的機(jī)械性能和黏均分子量均不同程度地下降,且H+和V(V)均起到加速降解的作用。FTIR結(jié)果表明SPI膜上的磺酸基團(tuán)在VRFB應(yīng)用中未被降解,1H-NMR譜證實(shí)降解后的SPI膜發(fā)生了聚合物分子鏈斷裂和酰亞胺環(huán)水解。XPS譜顯示SPI的水解產(chǎn)物 NH2基團(tuán)被氧化�；谒袑�(shí)驗(yàn)研究結(jié)果,提出了SPI膜在VRFB中可能的兩步降解機(jī)理,即水解和氧化步驟。為增加SPI膜的穩(wěn)定性,制備了一系列磺化度從30%變化至70%的磺化聚酰亞胺/殼聚糖(SPI/CS)復(fù)合膜,并研究了它們的的VRFB性能。膜的結(jié)構(gòu)和形貌通過(guò)ATR-FTIR和AFM表征,膜的理化性質(zhì)被分別測(cè)試。研究結(jié)果顯示,SPI30/CS膜具有最低的質(zhì)子傳導(dǎo)率和低到可忽略的釩滲透率。使用SPI30/CS膜的VRFB在10 m A cm~(-2)電流密度下性能較穩(wěn)定,而在20、30 m A cm~(-2)及更高電流密度下均不能正常充放電,因SPI30/CS膜的質(zhì)子傳導(dǎo)率太低。盡管SPI70/CS膜的質(zhì)子傳導(dǎo)率最高(4.88×10~(-2) S cm-1),但是,使用SPI70/CS膜的VRFB在20~80 m A cm~(-2)電流密度下卻具有最低的庫(kù)倫效率,因?yàn)槟さ拟C滲透率亦最高(10.47×10-7 cm2min-1)。將SPI40/CS膜在50 m A cm~(-2)電流密度下進(jìn)行了100個(gè)充放電循環(huán),顯示出較穩(wěn)定的庫(kù)倫效率(99.3%)和能量效率(70.5%)。綜合考慮它們較高的質(zhì)子選擇性、較好的化學(xué)穩(wěn)定性以及優(yōu)異的VRFB性能,SPI40/CS及SPI50/CS膜均為面向VRFB應(yīng)用的潛在選擇。
[Abstract]:Total vanadium redox liquid flow battery (VRFB) is a new green secondary battery with adjustable capacity, deep charge and discharge, high efficiency, simple operation and maintenance, long service life. The diaphragm is one of the three major components of VRFB, separating the positive and negative electrolyte to prevent the self-discharge of the battery. The ideal VRFB diaphragm should have high proton conductivity and chemical / electrochemical stability. Vanadium permeation and low price. At present, the widely used VRFB membrane is perfluorinated sulfonic acid membrane, such as the Nafion series membrane produced by DuPont Company of the United States, its proton conductivity and chemical / electrochemical stability are relatively high. However, vanadium permeation and price are too high. Therefore, it is necessary to develop new diaphragm to meet the urgent need in the large-scale industrial application of VRFB. In many new diaphragm research and development for VRFB applications. Synthesis and preparation of non-fluorinated polymer membranes is an important research direction. Compared with Nafion membranes, non-fluorinated polymer membranes usually have the advantages of low vanadium permeation and low price. The stability of non-fluorinated polymer membrane is the bottleneck of its long-term use in VRFB. Therefore, it is urgent to study the degradation mechanism of non-fluorinated polymer membrane in VRFB. In order to elucidate the fundamental cause of the decrease of the stability of this kind of membrane, the sulfonated polyimide (SPI) membrane is represented by the non-fluorinated polymer membrane in this paper. The degradation mechanism of SPI film in VRFB was studied by in-situ and off-line measurements. The morphology, structure and mechanical properties of SPI film and its oligomer before and after degradation were studied. The results of optical photos and SEM images showed that the SPI films degraded in situ showed more serious surface morphology damage than those after offline degradation and were soaked in different soaking solutions. The mechanical properties and viscosity average molecular weight of SPI films decreased in varying degrees. The results of FTIR showed that the sulfonic groups on SPI films were not degraded in the application of VRFB. The 1H-NMR spectra confirmed that the degradation of SPI film resulted in the polymer molecular chain break and the hydrolysis of imide ring. XPS spectra showed that the hydrolyzed product of SPI was produced. The NH2 group is oxidized based on all experimental results. The possible two-step degradation mechanism of SPI membrane in VRFB, i.e. hydrolysis and oxidation steps, was proposed to increase the stability of SPI film. A series of sulfonated polyimide / chitosan / spi / CS composite membranes with sulfonation degree ranging from 30% to 70% were prepared. The structure and morphology of the films were characterized by ATR-FTIR and AFM, and the physicochemical properties of the films were tested. The SPI30/CS membrane has the lowest proton conductivity and negligible vanadium permeability. The VRFB using SPI30/CS membrane is 10 Ma / cm ~ (-2). The performance is stable at current density. But the charge and discharge can not be normal at 20 ~ 30 Ma / cm ~ (-2) and higher current density. Because the proton conductivity of SPI30/CS membrane is too low, although the highest proton conductivity of SPI70/CS membrane is 4.88 脳 10 ~ (-2) S cm ~ (-1), however. The VRFB using SPI70/CS film has the lowest Coulomb efficiency at the current density of 20 ~ 80 Ma / cm ~ (-2). Because the vanadium permeability of the membrane is also 10. 47 脳 10 ~ (-7) cm ~ (-2) min ~ (-1). The SPI40/CS membrane is 50 Ma / cm ~ (-2). 100 charge-discharge cycles were carried out at current density. It shows stable Coulomb efficiency (99.3) and energy efficiency (70.5%). Their higher proton selectivity, better chemical stability and excellent VRFB properties are considered. Both SPI40/CS and SPI50/CS films are potential options for VRFB applications.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM912

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