本文選題：鋰空氣電池 + 樹葉狀氧化石墨烯��； 參考：《復(fù)旦大學(xué)》2014年碩士論文

【摘要】：非水系鋰空氣電池的理論能量密度是現(xiàn)有鋰離子電池的5到10倍,可與汽油相媲美,因此近幾年來鋰空氣電池受到了人們的廣泛關(guān)注。鋰空氣電池主要由三部分組成：負(fù)極金屬鋰,電解液和空氣催化電極。鋰空氣電池的儲能原理是基于金屬鋰與氧氣的反應(yīng)。然而由于鋰空氣電池體系中所發(fā)生的反應(yīng)是氣液固三相參與的反應(yīng),因此影響鋰空氣電池的電池性能的因素有很多。本論文以開發(fā)高性能的鋰空氣電池為目標(biāo),對鋰空氣電池的主要組成進(jìn)行了研究,并運用非原位的XRD,紅外以及SEM等分析測試手段對鋰空氣電池充放電過程中的反應(yīng)機(jī)理進(jìn)行了分析與探討,對于發(fā)展鋰空氣電池具有極其重要的意義。而在這篇論文中我們主要研究以下幾個方面：空氣催化電極碳材料,離子液體電解液及濕度的影響。論文的三部分工作內(nèi)容如下：1.空氣電極碳材料的研究以VGCF為原料,采用傳統(tǒng)的Hummers法制備了一種新型的含碳納米管中脈的樹葉狀氧化石墨烯,作為鋰空氣電池的空氣催化電極材料進(jìn)行了研究。并且與含商業(yè)的碳納米管和普通的氧化石墨烯以及兩者質(zhì)量比1：1的簡單混合物的鋰空氣電池進(jìn)行了電性能比較。采用改進(jìn)的Hummers法制備的樹葉狀氧化石墨烯能夠有效綜合氧化石墨烯和碳納米管的優(yōu)點,因此具有了碳納米管的優(yōu)良導(dǎo)電性和氧化石墨烯的多反應(yīng)活性位點性,從而表現(xiàn)出極其優(yōu)異的循環(huán)性能和大容量性能。因此得出結(jié)論,具有優(yōu)良導(dǎo)電性和多反應(yīng)活性位點的材料具有更高的催化活性,能夠使Li202和O2之間相互轉(zhuǎn)換,從而提高鋰空氣電池的性能。另外,材料的孔道結(jié)構(gòu)也會影響鋰空氣電池的性能。研究表明,有序的介孔通道可以為電解液的浸潤和鋰離子的傳輸提供了便利,而大孔則不僅有利于氧氣的擴(kuò)散,也為Li2O2和O2之間的相互轉(zhuǎn)換提供了空間。因此我們采用模板法合成了介孔大孔多級孔的碳球陣列。由于鋰空氣電池充放電過程中發(fā)生的反應(yīng)是氣液固三相參與的反應(yīng),而我們合成的產(chǎn)物的分層次多孔結(jié)構(gòu)可以為其提供有序的三相反應(yīng)活性界面,從而提高鋰空氣電池的性能。另外,其有序的分層次多孔結(jié)構(gòu)在充放電過程中能夠較好地保持其原有的形貌,而這種結(jié)構(gòu)上的穩(wěn)定性改善了鋰空氣電池的循環(huán)性能。以不同含量的介孔大孔多級孔碳為活性物質(zhì)的鋰氧電池在相同條件下均獲得高于用Super P炭黑為活性物質(zhì)的鋰氧電池的比容量。綜合考慮循環(huán)和容量性能,該材料的最佳含量為30%。另外,其含量為30%時在不同電流密度下電壓極化差值均小于Super P炭黑的。并運用非原位的XRD,紅外以及SEM等手段對充放電過程進(jìn)行分析,也證實了上述推測的介孔大孔多級孔碳性能優(yōu)異的原因。2.一種離子液體電解液的研究鋰空氣電池的電解液主要包含電解質(zhì)和溶劑兩部分組成,其中溶劑的不穩(wěn)定性是限制鋰空氣電池發(fā)展的一大障礙。有機(jī)電解液是目前鋰空氣電池中研究最多的電解液體系。然而,最近的研究表明,高催化活性的氧自由基能夠分解大部分的有機(jī)電解液,包括在鋰離子電池中最常用的有機(jī)電解液。而離子液體由于其固有的低揮發(fā)性,不易燃性和對氧高穩(wěn)定性等特點而有可能成為鋰空氣電池電解液的希望。我們以γ-MnOOH納米棒為催化劑,在新型的EMIMBF4-LiNTf2離子液體對鋰空氣電池的電池性能進(jìn)行測試。結(jié)果表明,在EMIMBF4-LiNTf2離子液體中,鋰空氣電池表現(xiàn)超大的放電容量和較好的循環(huán)穩(wěn)定性。同時我們還在該電解液中,對以γ-MnOOH納米棒和α-MnO2納米棒為催化劑以及沒有催化劑的鋰空氣電池進(jìn)行了比較,發(fā)現(xiàn)含γ-MnOOH納米棒催化劑的鋰空氣電池在相同電流密度下表現(xiàn)出優(yōu)于含α-MnO2納米棒催化劑或不含催化劑的鋰空氣電池的放電容量以及放電電壓平臺。因此,我們得出初步結(jié)論以EMIMBF4-LiNTf2離子液體為電解液,用γ-MnOOH納米棒為催化劑,兩者的綜合實用能夠有效地改善鋰空氣電池的電化學(xué)性能。其超長的循環(huán)穩(wěn)定性歸因于該離子液體對氧氣的穩(wěn)定性和較寬的電化學(xué)耐壓窗口,而且γ-MnOOH納米棒能夠催化離子液體中的氧氣還原進(jìn)程,從而提高了鋰空氣電池的放電電壓平臺和放電容量。這一結(jié)果表明合適的離子液體電解液和高催化性能的催化劑對發(fā)展可充放鋰空氣電池十分重要。3.濕度對鋰氧電池電化學(xué)性能的影響為了發(fā)展真正意義上的鋰空氣電池,即氧氣來自于周圍空氣中,所以研究濕度對鋰氧電池性能的影響是十分必要的。因此,我們分別在干燥的純氧中,相對濕度為15%的純氧中以及相對濕度為50%的空氣中比較了鋰氧電池性能,并分析了濕度對碳基空氣催化電極所發(fā)生的反應(yīng)的影響。電化學(xué)研究表明鋰空氣電池的放電容量隨著相對濕度數(shù)值的升高而增大,而循環(huán)性能和倍率性能卻隨相對濕度數(shù)值的升高而變差。而非原位的XRD,紅外以及SEM測試結(jié)果表明濕度不僅影響Li2O2/O2,LiCO3/O2的轉(zhuǎn)換以及LiOH的形成,也直接影響著充放電過程中多孔催化電極上放電產(chǎn)物的形貌。此外,根據(jù)上述研究結(jié)果可以明顯地看出不同濕度對負(fù)極的腐蝕影響不同,從而逐漸加重了這些電池的電化學(xué)性能之間的差別,而濕度對負(fù)極的影響將是我們下一步研究的方向。上述結(jié)果對發(fā)展鋰空氣電池十分重要。
[Abstract]:The theoretical energy density of the non-aqueous lithium air battery is 5 to 10 times that of the existing lithium ion battery, which is comparable to that of the gasoline. Therefore, the lithium air battery has attracted wide attention in recent years. The lithium air battery consists mainly of three parts: anode metal lithium, electrolyte and air accelerating electrode. The energy storage principle of lithium air battery is based on gold. However, there are many factors affecting the performance of lithium air batteries because of the reaction in the lithium air battery system because of the reaction of the gas-liquid solid three-phase. This paper aims at developing the high performance lithium air battery, and studies the main composition of the lithium air battery, and uses the insitu. XRD, infrared and SEM analysis methods have been analyzed and discussed for the reaction mechanism of lithium air battery charging and discharging. It is of great significance for the development of lithium air batteries. In this paper, we mainly study the following aspects: the influence of the air catalytic electrode carbon material, the ionic liquid electrolyte and the humidity. The three parts of the work are as follows: 1. the study of air electrode carbon materials is made of VGCF as the raw material. A new type of leaf like graphite oxide in the middle vein of carbon nanotubes is prepared by the traditional Hummers method. It is studied as the air catalytic electrode material of the lithium air battery. The electrical properties of the fossil graphene and the lithium air batteries with a simple mixture of 1:1 are compared. The leaves like graphene oxide prepared by the improved Hummers method can effectively integrate the advantages of the oxidation of graphene and carbon nanotubes, thus having the excellent conductivity of the carbon nanotubes and the multi reaction active site of the graphene oxide. Therefore, it is concluded that materials with excellent conductivity and reactive active sites have higher catalytic activity, can make Li202 and O2 convert to each other, thus improve the performance of lithium air batteries. The study shows that the ordered mesoporous channels can provide convenience for the infiltration of electrolyte and the transfer of lithium ion. The large pore is not only beneficial to the diffusion of oxygen, but also provides space for the mutual conversion between Li2O2 and O2. Therefore, we use template method to synthesize the carbon sphere array of mesoporous large pore and multistage holes. The reaction in the charging and discharging process is the reaction of the gas-liquid solid three-phase, and the hierarchical porous structure of the synthesized products can provide an orderly three-phase reactive interface, thus improving the performance of the lithium air battery. In addition, the ordered hierarchical porous structure can keep its original in the charge and discharge process. The structural stability improves the cycle performance of lithium air batteries. Lithium oxygen cells with different content of mesoporous macroporous carbon as active substances obtain the specific capacity of lithium oxygen batteries with Super P carbon black as active substances under the same conditions. The optimum content of the material is comprehensive considering the cycle and capacity properties. For 30%., the voltage polarization difference at 30% at different current densities is less than Super P carbon black. The charge discharge process is analyzed by using non in-situ XRD, infrared and SEM methods. It is also proved that the above speculated that the high carbon performance of the mesoporous macroporous multistage pores is studied by.2. an ionic liquid electrolyte. The electrolyte of a gas battery consists mainly of two parts of electrolyte and solvent, in which the instability of solvent is a major obstacle to the development of lithium air batteries. Organic electrolyte is the most important electrolyte system in lithium air batteries. However, recent research shows that most of the oxygen free radicals of high catalytic activity can be decomposed. Electromechanical solution, including the most commonly used organic electrolyte in lithium ion batteries, and the ionic liquid may be the hope of the lithium air battery electrolyte due to its inherent low volatility, non flammability and high oxygen stability. We use gamma -MnOOH nanorods as the catalyst in the new EMIMBF4-LiNTf2 ionic liquid to the lithium air The performance of the battery was tested. The results showed that the lithium air battery showed great discharge capacity and good cyclic stability in the EMIMBF4-LiNTf2 ionic liquid. Meanwhile, we also compared the lithium air batteries with gamma -MnOOH nanorods and alpha -MnO2 nanorods as well as the lithium air batteries without catalyst in the electrolyte. The lithium air battery containing a gamma -MnOOH nanorod catalyst shows the discharge capacity of the lithium air battery with an alpha -MnO2 nanorod catalyst or no catalyst at the same current density, as well as the discharge voltage platform. Therefore, we draw a preliminary conclusion that the EMIMBF4-LiNTf2 ionic liquid is used as the electrolyte, and the gamma -MnOOH nanorods as the catalyst, two The comprehensive utility can effectively improve the electrochemical performance of the lithium air battery. Its ultra long cycle stability is attributed to the stability of the ionic liquid to oxygen and the wide electrochemical voltage resistance window, and the gamma -MnOOH nanorods can catalyze the process of oxygen reduction in the ionic liquid, thus increasing the discharge voltage of the lithium air battery. The results show that the suitable ionic liquid electrolyte and the high catalytic performance catalyst are very important for the development of the lithium air battery. The influence of.3. humidity on the electrochemical performance of the lithium oxygen cell is the real significance of the lithium air battery, that is, the oxygen comes from the ambient air, so the humidity is studied on the lithium oxygen. The effect of the battery performance is very necessary. Therefore, we compare the performance of the lithium oxygen battery in the dry oxygen, the relative humidity of 15% and the relative humidity of 50%, and analyze the effect of the humidity on the reaction of the carbon based air catalytic electrode. With the increase of relative humidity, the cyclic performance and multiplying performance varies with the increase of relative humidity. The results of XRD, IR and SEM show that humidity not only affects the conversion of Li2O2/O2, LiCO3/O2 and the formation of LiOH, but also affects the discharge production on the porous catalytic electrode in the process of charging and discharging. In addition, according to the above results, it is obvious that the influence of different humidity on the corrosion of the negative electrode is different, which gradually aggravates the difference between the electrochemical properties of these batteries, and the influence of humidity on the negative electrode will be our next research direction. The above results are very important for the development of the lithium air battery.
【學(xué)位授予單位】：復(fù)旦大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM911.41

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本文編號：1932075