本文關(guān)鍵詞：多孔鈷酸鐵非碳正極的制備及其在鋰空氣電池中的應(yīng)用研究　出處：《深圳大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鈷酸鐵 非碳正極 金 催化劑 鋰空氣電池

【摘要】：新型鋰空氣電池由于具備極高的理論能量密度而受到了廣泛的關(guān)注。但是,鋰空氣電池離實(shí)際應(yīng)用還存在著很大的差距,其較大的充放電過電勢導(dǎo)致了較差的循環(huán)性能和倍率性能,這與空氣正極的氧還原反應(yīng)(ORR)和氧析出反應(yīng)(OER)過程的鈍化密切相關(guān)。通過改善空氣正極的結(jié)構(gòu)并結(jié)合催化劑的使用是促進(jìn)鋰空氣電池ORR與OER過程的有效途徑。本文中,為避免碳基正極的各種弊端,采用水熱法和熱處理法使金屬氧化物催化劑鈷酸鐵(FeCo_2O_4)薄片原位生長在泡沫鎳(Ni)上構(gòu)筑大孔/介孔并存的多孔非碳正極FeCo_2O_4@Ni并應(yīng)用到鋰空氣電池中,大孔提供放電產(chǎn)物L(fēng)i2O2儲(chǔ)存的空間和O2的擴(kuò)散通道;而FeCo_2O_4薄片上的介孔則為ORR/OER提供充足的催化活性位點(diǎn)。而后通過使用貴金屬金(Au)來修飾FeCo_2O_4@Ni,制備出新型復(fù)合空氣正極Au/FeCo_2O_4@Ni,以進(jìn)一步降低充放電過電勢,提升電池循環(huán)性能。兩種非碳正極具體的性能考察如下:(1)通過水熱反應(yīng)和熱處理兩個(gè)過程制備非碳正極FeCo_2O_4@Ni,并通過改變水熱溶劑和煅燒溫度(300-400℃)來調(diào)控FeCo_2O_4的形貌、結(jié)構(gòu)。采用SEM、BET、XRD等手段對材料的理化性能進(jìn)行表征,最后將空氣正極分別組裝成CR2032型扣式電池,并進(jìn)行多種電化學(xué)性能測試。結(jié)果表明乙二醇能夠起到減少催化劑堆疊和團(tuán)聚的作用,350℃下煅燒得到的空氣正極FeCo_2O_4@Ni具有較大的比表面積和最大孔容,并且結(jié)晶程度良好,同時(shí)擁有最大的放電容量和最優(yōu)的充放電平臺(tái)。因此,確定水熱溶劑中含有乙二醇和煅燒溫度為350℃是制備大孔/介孔并存的FeCo_2O_4@Ni的最佳條件,后續(xù)的FeCo_2O_4@Ni均在此條件下制備。(2)繼續(xù)對非碳正極FeCo_2O_4@Ni在鋰空氣電池中的應(yīng)用進(jìn)行深入的研究。經(jīng)TEM和XPS表征進(jìn)一步確認(rèn)了FeCo_2O_4@Ni為大孔/介孔并存的三維多孔結(jié)構(gòu)和其氧空位的存在。將所制備的非碳正極FeCo_2O_4@Ni與碳基正極KB/FeCo_2O_4/Ni進(jìn)行電化學(xué)性能比較,發(fā)現(xiàn)前者的充放電過電勢低于后者,前者的循環(huán)運(yùn)行次數(shù)也高于后者,充分證明了非碳正極FeCo_2O_4@Ni對ORR和OER過程的促進(jìn)作用。通過SEM形貌表征發(fā)現(xiàn),空氣正極FeCo_2O_4@Ni的放電產(chǎn)物主要為無定形的低維度的Li2O2,并且相較于結(jié)晶型的Li2O2,無定形的Li2O2在充電過程中更容易被分解。然而,盡管非碳正極FeCo_2O_4@Ni在一定程度上緩解空氣正極的鈍化問題,但隨著電池的循環(huán)運(yùn)行,放電電壓下降較快,這是由于非碳正極FeCo_2O_4@Ni的導(dǎo)電性比較差,需要進(jìn)一步改善電極的導(dǎo)電性。(3)最后,將所制備的FeCo_2O_4@Ni浸泡在四氯金酸溶液中形成新型復(fù)合空氣正極Au/FeCo_2O_4@Ni。經(jīng)SEM、XRD和XPS表征,確認(rèn)復(fù)合電極上貴金屬金(Au)的成功添加和FeCo_2O_4結(jié)構(gòu)的保留。此外,通過電化學(xué)性能測試,表明了添加貴金屬金后提高了電極的導(dǎo)電性,穩(wěn)定了電極的放電電壓,并且在循環(huán)充放電的中后期過程中顯著降低了充放電過電勢,提高了電池循環(huán)性能。綜上所述,本論文制備了兩種以鈷酸鐵催化劑為主體的多孔非碳正極,并系統(tǒng)地研究了其在鋰空氣電池中的催化機(jī)理和電化學(xué)性能,證實(shí)了相較于對應(yīng)的碳基正極,兩種非碳正極有效降低了電池的充放電過電勢和提高了電池的循環(huán)性能。
[Abstract]:The new lithium air batteries have attracted much attention due to the theory of energy density with very high. However, lithium air battery from practical application there are still a large gap between the large overpotential leads to the charge discharge cycle performance and rate performance is poor, and the air cathode oxygen reduction reaction (ORR) and oxygen precipitation the reaction (OER) process of passivation is closely related. By improving the structure of air cathode and combined with the use of catalysts is an effective way to promote the lithium air battery ORR and OER process. In this paper, in order to avoid the disadvantages of carbon based anode, by hydrothermal method and heat treatment method of the metal oxide catalyst of cobalt iron (FeCo_2O_4) in situ growth on nickel foam sheet (Ni) on the structure of porous macroporous / mesoporous carbon cathode FeCo_2O_4@Ni non coexist and applied to lithium air battery, macroporous diffusion discharge products Li2O2 storage space and O2. Tao; provide adequate catalytic active sites of mesoporous FeCo_2O_4 thin sheet is ORR/OER. Then through the use of precious metal (Au) modified FeCo_2O_4@Ni prepared Au/FeCo_2O_4@Ni composite cathode air, to further reduce the charge discharge potential, enhance the cycle performance of battery. Two kinds of non carbon anode performance of specific investigation are as follows: (1) through hydrothermal reaction and heat treatment process of the preparation of two non carbon anode FeCo_2O_4@Ni, and by changing the hydrothermal solvent and calcination temperature (300-400 DEG C) to control the morphology, the structure of FeCo_2O_4. Using SEM, BET, physicochemical properties are characterized by means of XRD material, the air cathode respectively. Assemble type CR2032 button battery, and various electrochemical performance test. The results showed that ethylene glycol can reduce stacking and agglomeration effects of the catalysts calcined at 350 FeCo_2O_4@Ni with a positive air The large surface area and maximum pore volume, and the crystallization degree is good, the charge and discharge platform also has the largest discharge capacity and optimal. Therefore, determination of hydrothermal solvents containing ethylene glycol and calcination temperature to 350 degrees is the best conditions for preparing macroporous / mesoporous FeCo_2O_4@Ni coexistence, subsequent FeCo_2O_4@Ni here under the condition of preparation. (2) to continue in-depth study on the application of non carbon anode in lithium air battery in FeCo_2O_4@Ni. The TEM and XPS characterization confirmed the three-dimensional porous structure of FeCo_2O_4@Ni macroporous / mesoporous coexist and the presence of oxygen vacancies. The preparation of non carbon anode and carbon FeCo_2O_4@Ni comparison of KB/FeCo_2O_4/Ni based cathode electrochemical performance, found that the former charge discharge potential is lower than the latter, cycle running times are higher than the former to the latter, fully proved that the non carbon anode FeCo_2O_4@Ni on ORR and OER in the process of promoting The role of the SEM morphology characterization shows that the discharge products mainly for air cathode FeCo_2O_4@Ni amorphous low dimension Li2O2, and compared with crystalline Li2O2, amorphous Li2O2 more easily in the process of charging is decomposed. However, despite the non carbon anode passivation of FeCo_2O_4@Ni to some extent alleviate the air anode, but with the circulation of the battery, the discharge voltage decreases rapidly, this is because the conductivity of non carbon anode FeCo_2O_4@Ni is relatively poor, need to further improve the conductivity of the electrode (3). Finally, the FeCo_2O_4@Ni prepared by immersion in four gold chloride acid solution to form a new type of composite air cathode Au/FeCo_2O_4@Ni. by SEM, XRD and XPS. Confirm, composite electrode precious metal (Au) retained successfully added and FeCo_2O_4 structure. In addition, the electrochemical performance tests show that the addition of conductive, precious metal after high electrode Stable discharge voltage, electrode, and in the later process of charge discharge cycle in significantly reduced the charge discharge potential, improve the cycle performance of battery. To sum up, this thesis synthesized two cobalt iron catalyst as the main body of the non porous carbon cathode, and studied its catalytic mechanism in a lithium air battery and the electrochemical properties, demonstrated that carbon based cathode compared to the corresponding to the two kinds of non carbon anode effectively reduces the battery charge and discharge overpotential and improve the cycle performance of the battery.

【學(xué)位授予單位】：深圳大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O643.36;TM911.41

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 Junjun Shi;Xiulan Hu;Jianbo Zhang;Weiping Tang;Hongtao Li;Xiaodong Shen;Nagahiro Saito;;One-step facile synthesis of Pd nanoclusters supported on carbon and their electrochemical property[J];Progress in Natural Science:Materials International;2014年06期

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本文編號：1431866