【摘要】：在現(xiàn)有的電池體系中,鋰空氣電池因具有最高的理論容量密度(約為鋰離子電池的10倍以上),將有望可以解決電動車續(xù)航能力嚴重不足的難題,甚至可以極大緩解目前所面臨的能源與環(huán)境危機。盡管如此,對處于實驗室研發(fā)階段的鋰空氣電池來說,仍然有很多問題(如大倍率性能、循環(huán)壽命、放電深度等)亟待解決。為此研究人員主要從兩個方面出發(fā),一是開發(fā)性能優(yōu)異的電極材料/催化劑,一是尋找綜合性能優(yōu)異的電解液/質(zhì)。在電極材料的研究方面,以往的研究主要集中于質(zhì)輕、孔豐富、導電性好、化學性質(zhì)穩(wěn)定的碳基材料。經(jīng)過微觀架構(gòu)、層次孔的設(shè)計,鋰空電池的電化學性能確實得到了飛躍的提高。但是隨著研究的深入,發(fā)現(xiàn)碳基材料的孔利用率并不如預期那么高,并且其化學穩(wěn)定性也不夠理想。因此,尋找廉價、活性高、穩(wěn)定性好的空氣電極材料顯得尤為必要。導電聚吡咯因具有導電性可調(diào)、微觀形貌可控、電化學活性高等優(yōu)點,可被用作鋰空電池的電極材料。因此,通過微觀形貌、電導率的調(diào)制,研究導電聚吡咯基空氣電極在鋰空氣電池中的應用具有比較重要的理論意義。本課題主要通過一維納米結(jié)構(gòu)聚吡咯基空氣電極材料的微觀結(jié)構(gòu)和電導率的設(shè)計來研究其電化學響應,研究內(nèi)容主要包括一維納米結(jié)構(gòu)聚吡咯形成機理的研究;具有典型微觀形貌聚吡咯基空氣電極的電化學行為研究。得出以下結(jié)論:(1)系統(tǒng)研究了自組裝軟模板甲基橙濃度對聚吡咯微觀形貌和電導率的影響。發(fā)現(xiàn),隨甲基橙模板濃度升高,聚吡咯的微觀形貌經(jīng)歷了一個由顆粒轉(zhuǎn)變?yōu)榘魻畹难莼?并且隨濃度增加聚吡咯納米棒直徑逐漸減小;模板濃度的增加有利于吡咯單體α-α位的聚合,從而導致了聚吡咯導電率的上升。當甲基橙模板的濃度達到5 mM時,其導電率達到最大值為16.7 S/cm,比顆粒狀聚吡咯的電導率高一個數(shù)量級。(2)系統(tǒng)研究了氧化劑用量對聚吡咯微觀形貌和電導率的影響。發(fā)現(xiàn),隨氧化劑(FeCl3)加入量的增加,聚吡咯形貌由殘缺的管狀結(jié)構(gòu)發(fā)育為完整的管狀結(jié)構(gòu),在結(jié)構(gòu)上的共軛程度呈先增加后減小的趨勢,表現(xiàn)在導電率上為先上升后下降。當氧化劑(FeCl3)與單體(Py)的物質(zhì)的量之比為3:2,聚吡咯導電率達到最大值49.7 S/cm。(3)系統(tǒng)研究了吡咯(Py)單體用量對聚吡咯微觀形貌的影響。發(fā)現(xiàn),隨Py增加,聚吡咯的微觀形貌由片狀和殘缺的管狀結(jié)構(gòu)逐漸聚合為完整的棒狀結(jié)構(gòu),并且隨著Py量的增加,聚吡咯納米棒直徑基本保持不變。聚吡咯在模板上的生長具有一定的取向性,在垂直方向上由外及內(nèi)逐漸生長,在水平方向上沿管壁方向生長。(4)初步研究了具有典型微觀形貌(開口管狀和多針狀)一維納米結(jié)構(gòu)聚吡咯空氣電極的電化學響應。發(fā)現(xiàn),在100 mA/g的電流密度下,開口結(jié)構(gòu)的聚吡咯納米管空氣電極的放電比容量高達2300 m Ah/g,在電流密度提高到300 mA/g時容量損失只有5%,表現(xiàn)出了良好的倍率性能,在所有形貌的一維聚吡咯中擁有最高的氧還原(ORR)和氧氧化(OER)活性,但其循環(huán)性能需要進一步改善。
[Abstract]:In the existing battery system, lithium-air batteries with the highest theoretical capacity density (about 10 times more than lithium-ion batteries), will hopefully be able to solve the problem of insufficient endurance of electric vehicles, and even greatly alleviate the current energy and environmental crisis. There are still many problems to be solved urgently for gas batteries, such as high-rate performance, cycle life, discharge depth, etc. Therefore, researchers mainly start from two aspects, one is to develop excellent electrode materials / catalysts, the other is to find electrolytes / materials with excellent comprehensive performance. The electrochemical performance of lithium-air batteries has been improved by leaps and bounds after the design of micro-structure and layered pore. However, with the further study, it is found that the pore utilization rate of carbon-based materials is not as high as expected, and their chemical stability is not ideal. Therefore, it is necessary to find a cheap, active and stable air electrode material. Conducting polypyrrole can be used as electrode material for lithium-air batteries because of its adjustable conductivity, controllable micro-morphology and high electrochemical activity. In this paper, the electrochemical response of one-dimensional nanostructured polypyrrole-based air electrode materials was studied by designing the microstructure and conductivity of the materials. The research contents mainly include the formation mechanism of one-dimensional nanostructured polypyrrole; typical micro-morphology of polypyrrole-based holes The results are as follows: (1) The effect of the concentration of methyl orange on the morphology and conductivity of polypyrrole was studied systematically. It was found that the morphology of polypyrrole changed from particle to rod with the increase of the concentration of methyl orange template. When the concentration of methyl orange template reached 5 mM, the conductivity of polypyrrole was 16.7 S/cm, which was one order of magnitude higher than that of granular polypyrrole. It is found that the morphology of polypyrrole develops from incomplete tubular structure to intact tubular structure with the increase of the amount of oxidant (FeCl3). The degree of conjugation increases first and then decreases. The conductivity increases first and then decreases. When the amount of oxidant (FeCl3) and monomer (Py) is added, the morphology of polypyrrole develops from incomplete tubular structure to intact tubular structure. (3) The effect of the amount of pyrrole monomer on the morphology of polypyrrole was studied systematically. It was found that with the increase of Py, the morphology of polypyrrole gradually polymerized from lamellar and incomplete tubular structures to complete rod-like structures, and with the increase of Py content, the polypyrrole nanorods were straight. The diameter of the polypyrrole is basically unchanged. The growth of the polypyrrole on the template has a certain orientation, growing from outside to inside in the vertical direction, and growing along the wall of the tube in the horizontal direction. (4) The electrochemical response of the polypyrrole air electrode with typical micro-morphology (open tubular and multi-needle) has been studied preliminarily. At the current density of mA/g, the discharge specific capacity of the open-ended polypyrrole nanotube air electrode is as high as 2300 m Ah/g. When the current density is increased to 300 mA/g, the capacity loss is only 5%. The polypyrrole exhibits good rate performance, and has the highest oxygen reduction (ORR) and oxygen oxidation (OER) activity in all morphologies of the one-dimensional polypyrrole, but its cyclicity is good. It needs further improvement.
【學位授予單位】：深圳大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ317;TM911.41

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相關(guān)期刊論文 前1條

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本文編號：2238921