本文選題：石墨負(fù)極材料 + 人造石墨　； 參考：《湖南大學(xué)》2015年碩士論文

【摘要】：鋰離子電池具有電壓高、比能量高、自放電少、綠色環(huán)保、無(wú)記憶效應(yīng)等優(yōu)點(diǎn),被譽(yù)為“21世紀(jì)最具有競(jìng)爭(zhēng)力的動(dòng)力電源”,不僅廣泛應(yīng)用于便攜式電子產(chǎn)品中,還被應(yīng)用于航天航空、軍事、電動(dòng)汽車(chē)和儲(chǔ)能等領(lǐng)域。石墨材料具有比容量高、循環(huán)性能好、嵌脫鋰平臺(tái)低、成本低廉等優(yōu)點(diǎn),成為最具有商業(yè)價(jià)值的鋰離子電池負(fù)極材料。但是由于石墨與有機(jī)溶劑電解液的相容性很差,使得負(fù)極材料表面形成過(guò)多的SEI膜,過(guò)量的SEI膜不僅消耗大量的鋰,產(chǎn)生較大的不可逆容量損失,還使界面阻抗增大,引起電化學(xué)動(dòng)力學(xué)障礙,使石墨層解理乃至剝落,導(dǎo)致容量衰減和循環(huán)性能下降。因此,為進(jìn)一步改善石墨負(fù)極材料的性能,本文采用真空-液相包覆法對(duì)石墨材料進(jìn)行瀝青炭包覆改性處理。采用XRD、SEM和多種電化學(xué)測(cè)試方法考察了軟化點(diǎn)較低的中溫瀝青和改質(zhì)瀝青炭包覆對(duì)石墨結(jié)構(gòu)、形貌和電化學(xué)性能的影響。實(shí)驗(yàn)結(jié)果表明:采用真空-液相包覆法能夠制備出具有良好的“核-殼”結(jié)構(gòu)復(fù)合材料。瀝青炭種類(lèi)和包覆量對(duì)石墨樣品的結(jié)構(gòu)和電化學(xué)性能影響很大,中溫瀝青包覆微晶石墨,改質(zhì)瀝青包覆人造石墨,在石墨顆粒表面可以形成良好的無(wú)定形炭包覆層,提高石墨材料的電化學(xué)性能,隨著包覆量的增加,石墨顆粒團(tuán)聚性增加,表面平整度增加;經(jīng)過(guò)包覆改性可以提高石墨材料的首次庫(kù)倫效率,并保持可逆容量基本不變。而采用改質(zhì)瀝青炭包覆天然微晶石墨和采用中溫瀝青炭包覆人造石墨,包覆效果都較差。中溫瀝青炭包覆微晶石墨的最佳包覆量為6%,改質(zhì)瀝青炭包覆人造石墨的最佳包覆量為9%。瀝青濃度越高,天然微晶石墨包覆樣品電化學(xué)性能越好,本實(shí)驗(yàn)最佳瀝青濃度為0.1g/ml。炭化升溫速率也會(huì)影響天然微晶石墨包覆樣品的電化學(xué)性能,炭化升溫速率過(guò)快或過(guò)慢都不利于電化學(xué)性能的提高,最佳炭化升溫速率為2℃/min。炭化溫度越高,人造石墨包覆樣品的電化學(xué)性能越好,本實(shí)驗(yàn)的最佳炭化溫度為1100℃。真空-液相包覆人造石墨的改性效果優(yōu)于固相包覆人造石墨的改性效果。經(jīng)過(guò)包覆改性后,石墨材料電化學(xué)性能得到明顯改善,微晶石墨和人造石墨的首次庫(kù)倫效率分別從原來(lái)的86.5%和90.0%提高到92.7%和93.4%,循環(huán)性能得到改善。
[Abstract]:Li-ion battery has the advantages of high voltage, high specific energy, less self-discharge, green environment protection, no memory effect and so on. It is praised as "the most competitive power supply in the 21st century", which is not only widely used in portable electronic products. They are also used in aerospace, military, electric vehicles and energy storage. Graphite has many advantages, such as high specific capacity, good cycling performance, low platform and low cost, so it has become the most valuable anode material for lithium ion batteries. However, due to the poor compatibility between graphite and organic solvent electrolyte, too much SEI film is formed on the surface of anode material. The excess SEI film not only consumes a large amount of lithium, but also results in a large irreversible loss of capacity, and increases the interface impedance. It causes electrochemical kinetic obstacles, cleavage and even exfoliation of graphite, resulting in capacity attenuation and decreased cycling performance. Therefore, in order to further improve the performance of graphite anode materials, the vacuum liquid phase coating method was used to modify graphite materials by bituminous carbon coating. The effects of carbon coating on graphite structure, morphology and electrochemical properties were investigated by XRDX SEM and various electrochemical methods. The experimental results show that a good "core-shell" structure composite can be prepared by vacuum-liquid phase coating method. The structure and electrochemical properties of graphite samples are greatly affected by the type and amount of bituminous carbon. A fine amorphous carbon coating layer can be formed on the surface of graphite particles by medium temperature bitumen coated with microcrystalline graphite and modified asphalt coated with artificial graphite. With the increase of coating amount, the agglomeration of graphite particles increases and the surface smoothness increases, and the first Coulomb efficiency of graphite material can be improved by coating modification, and the reversible capacity remains unchanged. However, the coating effect of modified bituminous carbon coated with natural microcrystalline graphite and medium temperature bituminous carbon coated with artificial graphite is poor. The optimum coating amount of medium temperature bituminous carbon coated microcrystalline graphite is 6 and that of modified asphalt carbon coated artificial graphite is 9. The higher the asphalt concentration, the better the electrochemical performance of the sample coated with natural microcrystalline stone ink. The optimum asphalt concentration in this experiment is 0.1 g 路ml ~ (-1) 路L ~ (-1) 路L ~ (-1). The carbonization heating rate also affects the electrochemical performance of the sample coated with natural microcrystalline stone ink. Too fast or too slow carbonization temperature rise rate is not conducive to the improvement of the electrochemical performance. The best carbonization temperature rise rate is 2 鈩，

本文編號(hào)：1929432