本文選題：鋰離子電池 + 正極材料��； 參考：《西南石油大學(xué)》2017年碩士論文

【摘要】：三元正極材料 LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2、LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 和 LiNi0.8Co0.1Mn0.1O_2 具有可逆比容量高、成本低等優(yōu)點(diǎn),應(yīng)用前景廣闊。然而,上述正極材料由于屬于半導(dǎo)體材料,電子導(dǎo)電性差,導(dǎo)致其倍率性能及循環(huán)穩(wěn)定性差,限制了其在實(shí)際生產(chǎn)中的應(yīng)用。本論文以三元正極材料為研究對(duì)象,通過(guò)將其與石墨烯、碳納米管構(gòu)建的三維導(dǎo)電網(wǎng)絡(luò)復(fù)合來(lái)提升其電化學(xué)性能,系統(tǒng)研究了復(fù)合材料的微觀結(jié)構(gòu)、電化學(xué)性能及兩者之間的關(guān)聯(lián)機(jī)制,并總結(jié)了復(fù)合材料電化學(xué)性能提升的機(jī)理。采用二維片狀石墨烯(GNs)和一維管狀碳納米(CNTs)管構(gòu)建的三維導(dǎo)電網(wǎng)絡(luò)與LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2三元正極材料復(fù)合(LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/GNs/CNTs)提升其電化學(xué)性能。復(fù)合材料中,GNs包覆在LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2表面,CNTs穿插于GNs和LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的間隙,利于石墨烯與碳納米管的協(xié)同效應(yīng),構(gòu)筑高效三維導(dǎo)電網(wǎng)絡(luò),在最大程度上改善LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的表面電子導(dǎo)電性,提升其倍率性能及循環(huán)穩(wěn)定性。上述復(fù)合材料較之單一導(dǎo)電炭黑(SP)、GNs或CNTs與LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2復(fù)合制備的復(fù)合材料體現(xiàn)出了明顯優(yōu)異的電化學(xué)性能,LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/SP、LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/GNs、LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/CNTs 和 LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2/GNs/CNTs 復(fù)合正極材料在1 C下分別具有156 mAhg-1、150 mAhg-1、142 mAhg-1,161 mAhg-1的初始放電比容量,經(jīng)過(guò)1 C下循環(huán)50次分別保留了 56 mAhg-1 90 mAhg-1、75 mAhg-1,123 mAhg-1的放電比容量,容量保持率分別為:36%、60%、53%,76%。此外,論文還系統(tǒng)考察了不同類(lèi)型的碳納米管及石墨烯對(duì)復(fù)合材料電化學(xué)性能的影響,研究還表明:較細(xì)管徑的多壁碳納米管對(duì)提升三元正極材料LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的電化學(xué)性能具有更好的效果;氧化石墨烯由于帶有大量官能團(tuán),活性較高容易與電解液發(fā)生反應(yīng),不利于與三元正極材料電化學(xué)性能提升,還原氧化石墨烯具有較好的導(dǎo)電性和電化學(xué)惰性,與三元正極材料復(fù)合后能提升正極材料的倍率性能及循環(huán)穩(wěn)定性;當(dāng)石墨烯和碳納米管的質(zhì)量比為2:1時(shí),復(fù)合材料具有最好的倍率性能和循環(huán)穩(wěn)定性。論文還采用流變相法分別制備了 LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2和LiNi0.8Co0.1Mn0.1O_2三元正極材料,并系統(tǒng)研究了其與GNs、CNTs復(fù)合制備的復(fù)合材料的的電化學(xué)性能,研究結(jié)果表明,上述三元正極材料與GNs、CNTs共復(fù)合制備的復(fù)合材料體現(xiàn)出最優(yōu)異的倍率性能及循環(huán)穩(wěn)定性,且GNs和CNTs在復(fù)合材料中的最佳質(zhì)量比仍為2:1。上述結(jié)果表明,利用 GNs 及 CNTs 與三元正極材料 LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2、LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 和LiNi0.8Co01Mn0.1O_2共復(fù)合,通過(guò)GNs與CNTs的協(xié)同效應(yīng),均可以在復(fù)合材料中構(gòu)建高效三維導(dǎo)電網(wǎng)絡(luò),有利于三元正極材料表面電子導(dǎo)電性的提升,從而促進(jìn)其倍率性能及循環(huán)穩(wěn)定性的提高。此外,GNs與CNTs在上述三種復(fù)合材料中的最佳質(zhì)量比均為2:1,說(shuō)明該方法在提升三元正極材料倍率性能及循環(huán)穩(wěn)定性方面具有一定的普適性,亦具有潛在的商業(yè)應(yīng)用價(jià)值。
[Abstract]:The three element positive material LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2, LiNi_ (0.5) Co_ (0.2) Mn_ (0.3) O_2 and LiNi0.8Co0.1Mn0.1O_2 have the advantages of high reversible specific capacity, low cost and low cost. However, the above cathode material is a semiconductor material, and the electrical conductivity is poor, resulting in poor multiplication and cycle stability. In this paper, the three element positive material was used as the research object. The electrochemical properties of the composites were improved by combining the three dimensional conductive network with graphene and carbon nanotubes to improve the electrochemical performance. The microstructure, electrochemical properties and the correlation mechanism of the composites were systematically studied, and the electrochemical properties of the composites were summarized. The three-dimensional conductive network constructed by two dimensional flake graphene (GNs) and one dimensional tubular carbon nanotube (CNTs) tube is used to improve the electrical properties of the LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2 three yuan cathode material (LiNi_ (1/3) Co_). Interspersed with the gap between GNs and LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2, it is beneficial to the synergistic effect of graphene and carbon nanotubes, to construct an efficient three-dimensional conductive network, and to improve the electronic conductivity of the LiNi_ (1/3) Co_ (1/3) Co_ (1/3) Co_ (1/3). The composite material prepared by CNTs and LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2 shows obvious excellent electrochemical performance. The initial discharge specific capacity of hg-1150 mAhg-1142 mAhg-1161 mAhg-1, after 1 C cycles, retained 56 mAhg-1 90 mAhg-1,75 mAhg-1123 mAhg-1 respectively, and the capacity retention rate was 36%, 60%, 53%, and 76%. respectively. The paper also systematically investigated the electrochemical properties of different types of carbon nanotubes and graphene. The results also show that the multi walled carbon nanotubes with smaller diameter have better effects on improving the electrochemical performance of the three element positive electrode material LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) O_2, and the activity of graphene oxide is higher than that of the electrolyte, which is not conducive to the improvement of the electrochemical performance with the three element cathode material. The original graphene oxide has good conductivity and electrochemical inertia. It can improve the ratio and cyclic stability of the cathode material with the composite of three yuan positive material. When the mass ratio of graphene and carbon nanotube is 2:1, the composite has the best performance of multiplier and cyclic stability. The paper also uses rheological phase method to prepare LiN respectively. I_ (0.5) Co_ (0.2) Mn_ (0.2) Mn_ (0.3) O_2 and LiNi0.8Co0.1Mn0.1O_2 three yuan positive electrode materials, and systematically study the electrochemical properties of the composite prepared with GNs, CNTs composite. The results show that the composite materials prepared by the co compound of the three element positive electrode and GNs and CNTs show the most excellent multiplier and cyclic stability, and GNs and CNTs. The optimum mass ratio in the composite is still 2:1.. The results show that using GNs and CNTs, LiNi_ (1/3) Co_ (1/3) Mn_ (1/3) Mn_ (1/3) O_2, LiNi_ (0.5) Co_ (0.2) and co recombination, the efficient three-dimensional conductive network can be constructed in the composite by the synergistic effect. In addition, the optimum mass ratio of GNs and CNTs in the above three composite materials is 2:1, which shows that the method has a certain universality and potential in improving the ratio and cyclic stability of the three Yuan Zhengji material. The value of commercial application.
【學(xué)位授予單位】：西南石油大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TM912

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本文編號(hào)：1904196