本文選題：超級(jí)電容器　切入點(diǎn)：中孔納米碳纖維　出處：《華東理工大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：超級(jí)電容器是一種介于電池和傳統(tǒng)電容器間的新型儲(chǔ)能設(shè)備,具有功率密度高、使用壽命長(zhǎng)、溫度特性好、綠色環(huán)保等突出優(yōu)點(diǎn)。但超級(jí)電容器較低的能量密度是限制其應(yīng)用的瓶頸,提高其能量密度成為該領(lǐng)域的研究重點(diǎn)。 本論文以化學(xué)氣相沉積法所制備的納米碳纖維為原料,經(jīng)氧化-熱處理得到中孔納米碳纖維,并以此為電極材料,組裝得到了高能量密度的插層型超級(jí)電容器。主要研究結(jié)果如下： (1)采用Hummers法將納米碳纖維氧化成類氧化石墨烯結(jié)構(gòu),進(jìn)一步通過熱處理得到彈簧狀中孔納米碳纖維。經(jīng)過氧化-熱膨脹處理后,納米碳纖維的比表面積明顯增大,并呈現(xiàn)中孔結(jié)構(gòu)；石墨層間距增大,且可通過改變氧化值或熱處理溫度調(diào)節(jié)。 (2)中孔納米碳纖維可發(fā)生插層電化學(xué)活化過程。該過程中,電解液離子在電壓的驅(qū)動(dòng)下插入到石墨層間,導(dǎo)致層間距不可逆擴(kuò)大,可用于離子吸／脫附的表面積增大,容量得以提升；且隨截止電壓的增大,離子插層過程深化,電容量進(jìn)一步提高。插層活化后的電極以雙電層原理工作。由于中孔納米碳纖維的彈簧狀結(jié)構(gòu)和松散的空間三維結(jié)構(gòu),能夠在插層過程中起到緩沖應(yīng)力作用,所制材料具有優(yōu)異的插層電化學(xué)性能。經(jīng)電化學(xué)活化后,整體電容器容量由2.8F/g增大到31.5F/g,正負(fù)極電容分別增至115.2F/g和138.1F/g。 (3)系統(tǒng)考察了電化學(xué)插層活化過程的因素影響。結(jié)果發(fā)現(xiàn)：板狀納米碳纖維比魚骨狀納米碳纖維插層電位更低,更易于發(fā)生電化學(xué)活化；氧化程度越大,層間距越大,導(dǎo)致初始活化電壓降低,插層過程越容易發(fā)生,且活化后獲得電容量也越高；插層活化過程還要求電解液對(duì)高電壓保持性質(zhì)穩(wěn)定,四氟硼酸螺環(huán)季銨鹽(SBPBF4)的螯合結(jié)構(gòu)使其穩(wěn)定性更強(qiáng),相比四氟硼酸四乙基銨(Et4NBF4)更有利于高工作電壓下的插層活化。 (4)以板狀膨脹納米碳纖維為正極材料,原始納米碳纖維作為負(fù)極材料,構(gòu)造新型納米碳纖維基鋰離子超級(jí)電容器。該鋰離子電容器的功率密度和能量密度分別可以達(dá)到11.7kW//kg和18.8Wh/kg,且具有良好的倍率性能。
[Abstract]:Supercapacitor is a new type of energy storage equipment between battery and traditional capacitor. It has high power density, long service life and good temperature characteristic. However, the low energy density of supercapacitors is the bottleneck to limit their application, and increasing their energy density has become the research focus in this field. In this paper, carbon nanofibers prepared by chemical vapor deposition were used as raw materials, and mesoporous carbon fibers were prepared by oxidation-heat treatment. The intercalated supercapacitors with high energy density have been assembled. The main results are as follows:. 1) carbon nanofibers were oxidized into graphene oxide structure by Hummers method, and the spring mesoporous carbon fibers were obtained by heat treatment. The specific surface area of carbon nanofibers increased obviously after oxidation and thermal expansion treatment. The graphite layer spacing increases and can be adjusted by changing the oxidation value or heat treatment temperature. (2) Intercalation electrochemical activation can occur in mesoporous carbon nanofibers. In this process, electrolyte ions are inserted into graphite layer driven by voltage, which results in irreversible expansion of interlayer spacing, which can be used to increase the surface area of ion adsorption / desorption. The capacity is increased, and the ion intercalation process deepens with the increase of cutoff voltage. The electrode after intercalation can work on the principle of double electric layer. Because of the spring-like structure of mesoporous carbon nanofibers and the loose three-dimensional structure of space, it can play a role of buffer stress in the intercalation process. After electrochemical activation, the capacitor capacity increased from 2.8 F / g to 31.5 F / g, and the positive and negative capacitance increased to 115.2 F / g and 138.1 F / g, respectively. The results show that the intercalation potential of plate carbon nanofibers is lower than that of fishbone carbon nanofibers, and electrochemical activation is more likely to occur, and the greater the degree of oxidation, the greater the interlayer spacing. The lower the initial activation voltage, the easier the intercalation process is, and the higher the capacitance is, the more stable the electrolyte is to the high voltage. The chelating structure of SBPBF4) is more stable than tetraethyl ammonium tetrafluoroborate (et _ 4NBF _ 4), which is more favorable for intercalation activation at high working voltage than tetraethyl ammonium tetrafluoroborate (et _ 4NBF _ 4). (4) sheet expanded carbon nanofibers are used as cathode materials, and raw carbon nanofibers are used as negative electrode materials. A new type of carbon fiber based lithium ion supercapacitor was constructed. The power density and energy density of the lithium ion capacitor can reach 11.7kW / r / kg and 18.8W / kg, respectively, and have good rate performance.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM53;TQ127.11

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