本文選題：鋰離子電池 + 尖晶石錳酸鋰��； 參考：《天津大學(xué)》2014年碩士論文

【摘要】：近年來(lái)由于環(huán)境污染和資源短缺,引發(fā)了能源汽車的熱議,也引起了研究者對(duì)汽車動(dòng)力電池的高度關(guān)注,為了滿足能源汽車的普及,對(duì)鋰離子電池的成本和性能穩(wěn)定性提出了新的要求。尖晶石錳酸鋰以儲(chǔ)量豐富、價(jià)格低廉、安全穩(wěn)定、綠色無(wú)污染等特點(diǎn)被公認(rèn)為適宜的動(dòng)力電池正極材料之一,但其高溫條件下存在的Jahn-Teller畸變效應(yīng)而引起的循環(huán)容量衰減問(wèn)題阻礙了其規(guī)�；瘧�(yīng)用。目前的解決方法有合成方法的改變、包覆改性、摻雜改性等,主要的改性方法為引入摻雜離子進(jìn)行摻雜改性,本文主要對(duì)采用高溫固相法合成的尖晶石錳酸鋰進(jìn)行金屬陽(yáng)離子摻雜,以改善其循環(huán)性能.采用高溫固相法溶膠凝膠法制備了錳酸鋰材料,XRD研究表明,兩種方法所制備的樣品均為尖晶石結(jié)構(gòu),通過(guò)SEM分析高溫固相法制備的樣品顆粒較大,形貌規(guī)則,粒度均勻,分散良好,電性能測(cè)試中高溫固相法樣品具有更高的放電容量、平穩(wěn)的放電平臺(tái),良好的循環(huán)性能。以Li2CO3和Mn(CH3COO)2為原材料,考察不同的焙燒工藝影響,通過(guò)XRD和電性能分析研究表明當(dāng)焙燒溫度為850℃,焙燒時(shí)間為20小時(shí)所合成的樣品具有更好晶體結(jié)構(gòu)和電化學(xué)性能,樣品首次可逆放電容量為128.7mAh/g,50周后循環(huán)保持率為94.2%。通過(guò)采用CH3COOLi、LiOH和Li2CO3以及Mn(CH3COO)2、MnSO4、MnCl2、Mn(NO3)2不同的原材料以高溫固相法合成尖晶石樣品,結(jié)果發(fā)現(xiàn)不同的原材料合成的樣品性能差異較大,以LiOH和Mn(CH3COO)2為原材料合成的樣品的結(jié)具有典型的尖晶石結(jié)構(gòu),結(jié)晶度高,形貌規(guī)則,電化學(xué)性能好。采用高溫固相合成法以LiOH和Mn(CH3COO)2為原材料,以不同原料配比合成尖晶石錳酸鋰,經(jīng)過(guò)XRD、SEM和電性能測(cè)試研究發(fā)現(xiàn),在高溫焙燒時(shí)存在Li鹽揮發(fā)的現(xiàn)象,鋰錳配比要高于化學(xué)計(jì)量比,以Li/2Mn=1.15合成出的樣品首次可逆容量為118.9 mAh/g,50周后循環(huán)保持率為97.6%。以LiOH和Mn(CH3COO)2為原材料,引入Co、Cr、Al元素進(jìn)行摻雜改性,采用高溫固相法合成樣品,XRD顯示,無(wú)論是單元摻雜還是多元摻雜錳酸鋰材料的晶體結(jié)構(gòu)沒(méi)有發(fā)生變化,均為尖晶石相結(jié)構(gòu),且無(wú)雜相出現(xiàn)。通過(guò)電性能測(cè)試分析,摻雜Co、Cr、Al單元素后,無(wú)論摻雜比例大小,均可引錳酸鋰材料可逆容量的降低,循環(huán)性能均可得到改善。通過(guò)引入Co、Cr、Al多元素?fù)诫s后,合成的錳酸鋰材料結(jié)構(gòu)不變,為尖晶石結(jié)構(gòu)。采用DSC分析確定Al元素對(duì)提高材料的熱穩(wěn)定性具有明顯的效果;Cr元素對(duì)改善材料的倍率性能有一定的作用;Co、Cr、Al三者的協(xié)同作用可顯著提高材料的循環(huán)性能尤其是高溫循環(huán)性能,合成得到Sample-2(LiCo0.1Cr0.05Al0.1Mn1.75O4)樣品常溫1C循環(huán),500周后容量保持率為89.9%,高溫55℃1C循環(huán)500周容量保持率仍然可達(dá)78.4%。通過(guò)對(duì)尖晶石LiMn2O4材料與LiCoO2和三元材料進(jìn)行混合,混合后樣品優(yōu)勢(shì)互補(bǔ),在LiCoO2材料中混合一定比例的LiMn2O4材料可以改善其安全穩(wěn)定性;在尖晶石LiMn2O4材料中混合一定比例的三元材料,可以提高材料的容量,并明顯改善LiMn2O4材料的高溫性能,混合比例為20%的樣品LMMNC-8,45℃循環(huán)500周后容量保持率為85.6%,比LMO提高了6.7%。
[Abstract]:In recent years, due to environmental pollution and shortage of resources, the hot discussion of energy vehicles has been caused, and the researchers have attracted the attention of the automotive power battery. In order to meet the popularity of energy vehicles, new requirements for the cost and performance stability of lithium ion batteries are put forward. Spinel lithium manganese acid lithium is rich in reserves, low in price, safe and stable and green. No pollution and other characteristics have been recognized as one of the suitable cathode materials for power batteries, but the problem of cyclic capacity attenuation caused by the Jahn-Teller distortion effect in high temperature conditions hinders its large-scale application. The current solutions include the changes of synthetic methods, coating modification, mixed modification, etc., the main modification method is the introduction of doping. Ion doping modification, this paper mainly doped metal cation of spinel manganate by high temperature solid-phase synthesis to improve its cycling performance. The lithium manganese oxide material was prepared by high temperature solid phase sol-gel method. The XRD study showed that the samples prepared by the two methods were spinel structure, and the high temperature solid phase was analyzed by SEM. The samples prepared by the method have large particles, regular morphology, uniform particle size and good dispersion. High temperature solid state samples have higher discharge capacity, stable discharge platform and good cycling performance in electrical properties test. The effects of different calcination processes are investigated with Li2CO3 and Mn (CH3COO) 2 as raw materials. By XRD and electrical properties analysis, it is shown that roasting The samples with a temperature of 850 C and 20 hours of calcination have better crystal structure and electrochemical properties. The first reversible discharge capacity of the sample is 128.7mAh/g, and the retention rate of the cycle is 94.2%. 50 weeks later by using CH3COOLi, LiOH and Li2CO3 and Mn (CH3COO) 2, MnSO4, MnCl2, Mn (NO3) 2 different raw materials to synthesize spinel by high temperature solid phase method. The results show that the properties of the samples synthesized by different raw materials are different. The samples synthesized by LiOH and Mn (CH3COO) 2 as the raw materials have typical spinel structure, high crystallinity, regular morphology and good electrochemical properties. LiOH and Mn (CH3COO) 2 are used as raw materials to synthesize spinel with different raw materials. Lithium manganate, after XRD, SEM and electrical properties test, found that there is a phenomenon of Li salt volatilization at high temperature, and the ratio of lithium and manganese is higher than that of stoichiometry. The first reversible capacity of the samples produced by Li/2Mn=1.15 is 118.9 mAh/g, and the retention rate of the Li/2Mn=1.15 is 97.6%. with LiOH and Mn (CH3COO) 2 as the raw material, and Co, Cr, Al elements are introduced. Modified, high temperature solid state method was used to synthesize the samples. XRD showed that the crystal structure of both unit and multi doped lithium manganese oxide material did not change, and all of them were spinel phase structure, and no heterozygous phase appeared. The reversible capacity of lithium manganese oxide material can be induced by doping Co, Cr and Al by electrical properties test. Through the introduction of Co, Cr, Al multielement doping, the structure of the synthesized lithium manganese dioxide is unchanged and the structure of spinel. The DSC analysis is used to determine the Al element to improve the thermal stability of the material; the Cr element has a certain effect on the improvement of the material multiplier performance; the coordination of Co, Cr, Al three. The function can significantly improve the cyclic performance of the material, especially the high temperature cycling performance. The Sample-2 (LiCo0.1Cr0.05Al0.1Mn1.75O4) sample at normal temperature 1C cycle is synthesized, the capacity retention rate is 89.9% after 500 weeks, and the 500 week capacity retention rate of the high temperature 55 C 1C cycle is still up to 78.4%. through mixing the spinel LiMn2O4 material with LiCoO2 and three yuan material. After mixing, the sample has complementary advantages. Mixing a certain proportion of LiMn2O4 material in LiCoO2 material can improve its safety and stability. Mixing a certain proportion of three yuan material in the spinel LiMn2O4 material can improve the capacity of the material, and obviously improve the high temperature performance of the LiMn2O4 material. The sample of the mixture ratio of 20% is LMMNC-8,45 centigrade for 500 weeks. The post capacity retention rate is 85.6%, which is higher than LMO by 6.7%.

【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TQ131.11;TM912

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本文編號(hào)：1831324