【摘要】：電解液是鋰離子電池不可或缺的一部分，在很大程度上制約著電池的安全性和穩(wěn)定性�，F(xiàn)今，人們對電池的能量密度需求越來越高，出現(xiàn)了以LiNi0.5Mn1.5O4為代表的一系列高電壓正極材料，因此，耐高壓電解液的研究受到了越來越廣泛的關(guān)注。盡管有一些關(guān)于新型高壓電解液溶劑和添加劑的研究報道，但是離商業(yè)化應(yīng)用尚有較大差距。 本論文中，通過對丁二腈和己二腈的電化學(xué)窗口和離子電導(dǎo)率進(jìn)行綜合對比，確認(rèn)在碳酸酯中加入5%的量使得混合電解液的物理性能最優(yōu)，充放電測試研究了正極材料LiNi0.5Mn1.5O4在電解液中的性能，但循環(huán)性能不佳；向混合電解液中加入適量的雙乙二酸硼酸鋰能使電解液的性能得到很好的改善，2C倍率下，經(jīng)過200次循環(huán)后，容量僅衰減了11%。 本文還研究了在普通電解液中添加質(zhì)量分?jǐn)?shù)為3%的丁二酸酐，LiNi0.5Mn1.5O4正極在該電解液中的循環(huán)穩(wěn)定性能得到很大的提高，0.2C的首次放電比容量為124.5mAh g-1，在充放電電壓為3.0-4.9V的區(qū)間內(nèi)，1C和2C倍率循環(huán)200圈的容量維持率分別為90%和92%，而使用普通電解液時，容量維持率僅為48%和47%。 研究了丁二酸酐的作用機(jī)理，通過線性伏安掃描測試得到丁二酸酐的氧化電位要低于碳酸酯的氧化電位，說明電池在充放電的過程中，丁二酸酐優(yōu)先發(fā)生氧化分解，在正極材料表面形成良好的界面膜，一方面隔絕電解液與正極材料之間的接觸，減少它們之間的副反應(yīng)；另一方面可以提高材料的電導(dǎo)率，，有利于鋰離子的脫嵌和嵌入，從而提高高壓正極材料的循環(huán)穩(wěn)定性。 本文還考察了其他三類添加劑在高壓電解液中的應(yīng)用。通過循環(huán)穩(wěn)定性的測試發(fā)現(xiàn)，加入1%的鄰苯二甲酸酐后，Li/LiNi0.5Mn1.5O4電池的大倍率性能很好，循環(huán)200圈容量幾乎沒有衰減，其作用機(jī)理還有待進(jìn)一步的研究。嘗試用氟代碳酸乙烯酯取代碳酸乙烯酯，與丁二腈進(jìn)行共混，所得到的混合電解液擁有高達(dá)5V的電化學(xué)穩(wěn)定窗口，但遺憾的是氟代碳酸乙烯酯沒有起到改善丁二腈與正極材料之間的相容性，導(dǎo)致LiNi0.5Mn1.5O4材料的循環(huán)性能仍然很差，猜想可能是加入的量過多或過少的原因，有待進(jìn)一步的實驗探索。
[Abstract]:Electrolyte is an indispensable part of lithium ion battery, which restricts the safety and stability of battery to a great extent. Nowadays, the demand for energy density of battery is more and more high, and a series of high voltage cathode materials, represented by LiNi0.5Mn1.5O4, have appeared. Therefore, the research of high voltage electrolyte has been paid more and more attention. Although there are some research reports on solvent and additive of new high voltage electrolyte, there is still a big gap from commercial application. In this paper, by comparing the electrochemical window and ionic conductivity of succinonitrile and adiponitrile, it is confirmed that the physical properties of the mixed electrolyte can be optimized by adding 5% of carbonic acid ester. The performance of cathode material LiNi0.5Mn1.5O4 in electrolyte was studied by charge-discharge test, but the cycling performance was not good. Adding proper amount of lithium diacetate borate to the mixed electrolyte could improve the performance of the electrolyte at the rate of 2C. After 200 cycles, the performance of the electrolyte was improved. Capacity only attenuates by 11. In addition, the cyclic stability of LiNi0.5Mn1.5O4 positive electrode in ordinary electrolyte was studied. The initial discharge specific capacity of 0.2C is 124.5mAh g-1, and the charge / discharge voltage is 3.0-4.9 V. The capacity maintenance rates of 1C and 2C cycles in the interval are 90% and 92%, respectively, when ordinary electrolytes are used, The capacity maintenance rate was only 48% and 47%. The action mechanism of succinic anhydride was studied. The oxidation potential of succinic anhydride was lower than that of carbonate by linear voltammetry. A good interfacial film is formed on the surface of the cathode material. On the one hand, the contact between the electrolyte and the cathode material is isolated and the side reactions between them are reduced; on the other hand, the conductivity of the material can be increased, which is favorable to the deintercalation and embedding of the lithium ion. Thus, the cyclic stability of high pressure cathode materials is improved. The application of other three kinds of additives in high-voltage electrolyte was also investigated. By testing the cycle stability, it is found that after adding 1% phthalic anhydride, the high rate performance of Li / LiNi0.5Mn1.5O4 battery is very good, and the cycle capacity of 200 cycles hardly attenuates, and the mechanism of its action remains to be further studied. Ethylfluorocarbonate was used to replace ethylene carbonate and mixed with butylene nitrile. The mixed electrolyte has a electrochemical stabilization window of up to 5 V. However, it is regrettable that ethylfluorocarbonate has not improved the compatibility between butylonitrile and cathode materials, which leads to the poor cycling performance of LiNi0.5Mn1.5O4 materials. It is suspected that the addition of too much or too little may be the reason for further experimental exploration.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TM912

【共引文獻(xiàn)】

相關(guān)博士學(xué)位論文 前10條

1 廖友好;鋰離子電池安全型電解質(zhì)的制備及性能研究[D];華南理工大學(xué);2013年

2 劉建生;鋰離子電池新型凝膠聚合物電解質(zhì)的改性研究[D];華南理工大學(xué);2013年

3 吳賢文;功能電解液對LiMn_2O_4和LiNi_(0.5)Mn_(1.5)O_4電化學(xué)性能改善及其機(jī)理研究[D];中南大學(xué);2013年

4 文志剛;金屬氧化物微/納米結(jié)構(gòu)的合成、表征及其在鋰離子電池中的應(yīng)用研究[D];中南大學(xué);2013年

5 夏陽;生物模板法構(gòu)筑多級多孔結(jié)構(gòu)電極材料及其儲鋰性能研究[D];浙江工業(yè)大學(xué);2013年

6 裴啟飛;AlCl_3-BMIC離子液體電解精煉鋁中雜質(zhì)行為研究[D];昆明理工大學(xué);2012年

7 柳志民;高性能鈦氧化物負(fù)極材料制備及其電化學(xué)性能研究[D];哈爾濱工業(yè)大學(xué);2012年

8 李娜;高功率柔性鋰離子電池電極材料的制備及其性能研究[D];中國科學(xué)技術(shù)大學(xué);2013年

9 陳立鋒;碳基復(fù)合材料的設(shè)計、規(guī)�；苽浼捌湓诔夒娙萜髦械膽�(yīng)用[D];中國科學(xué)技術(shù)大學(xué);2013年

10 鄭立炎;電致化學(xué)發(fā)光新材料的研究[D];福州大學(xué);2011年

本文編號：2146343