本文選題：鋰離子電池 + 高電壓　； 參考：《浙江大學》2017年碩士論文

【摘要】：隨著鋰離子電池的廣泛應用,高電壓鋰離子電池體系成為研究熱點。電解液作為鋰離子電池中的重要組成部分正面臨著挑戰(zhàn),一方面?zhèn)鹘y(tǒng)的碳酸酯電解液在4.5V以上就會發(fā)生氧化分解；另一方面新型高電壓電解液由于存在各種問題未能得到普遍應用。而電解液在高壓下的穩(wěn)定性直接影響著電池的電化學性能,是制約高電壓鋰離子電池發(fā)展的關鍵因素之一。據(jù)文獻報道,現(xiàn)階段有效而又經濟的解決方法之一就是在電解液中引入一定量(5%)的功能性添加劑,可以穩(wěn)定高電壓鋰離子電池體系從而提高電化學性能。本論文選用極性大、氧化電位高、熱穩(wěn)定性好的砜類作為研究對象,在1M LiPF6-EC:DMC(1:1)參比電解液(Standard, STD)體系中加入不同量的添加劑,通過對LiNi1/3CO1/3Mn1/3O2/Li、石墨/Li以及LiNi1/3Co1/3Mn1/3O2/石墨電池體系在不同電解液體系中的循環(huán)性能和倍率性能測試,并結合線性掃描伏安(Linear sweep voltammetry, LSV)、循環(huán)伏安(Cyclic voltammetry, CV)、電化學阻抗(Electrochemical impedance spectroscopy, EIS)以及掃描電子顯微鏡(Scanning electron microscopy, SEM)、能量色散X射線光譜學(Energy dispersive X-ray spectroscopy, EDS)和X射線光電子能譜(X-ray photoelectron spectroscopy, XPS)等材料表征手段,探討不同結構的砜作為添加劑對電池的影響。主要結果如下：1、環(huán)丁砜作為高電壓電解液添加劑：(1)研究發(fā)現(xiàn)當添加量為2%(體積比)時,環(huán)丁砜能夠提高參比電解液的電化學窗口以及增強電解液在高壓下的氧化穩(wěn)定性,并在一定程度上減少溶劑碳酸乙烯酯(Ethylene carbonate, EC)的還原分解。(2)含有環(huán)丁砜的電解液對LiNi1/3CO1/3Mn1/3O2正極、石墨負極的相容性較好,LiNi1/3Co1/3Mn1/3O2/Li、石墨/Li以及LiNi1/3Co1/3Mn1/3O2/石墨電池體系的放電容量、循環(huán)性能和倍率性能都得到提高。(3)結合多種分析手段發(fā)現(xiàn)：環(huán)丁砜對電池電化學性能的改進的機理是含有環(huán)丁砜的電解液能夠在正負極表面形成均一緊密的膜層,消除膜層表面的裂痕從而抑制電解液的持續(xù)分解,提高了循環(huán)過程中電解液和電極的穩(wěn)定性,減少電池體系在循環(huán)過程中的阻抗增加,從而使電池性能得到提升。2、乙基異丙基砜(Ethyl isopropyl sulfone, EIS)、乙基乙烯基砜(Ethyl vinyl sulfone, EVS)作為添加劑：(1) 乙基異丙基砜作為添加劑時,能夠提高參比電解液的電化學窗口至4.5V, LiNi1/3Co1/3Mn1/3O2正極材料在4.6V的截止電壓下充放電100次的放電容量更大、循環(huán)更穩(wěn)定；但發(fā)現(xiàn)電池在循環(huán)過程中的阻抗的增加幅度比參比電解液大,且石墨負極在含該添加劑的體系中的電化學性能并不理想。(2)乙基乙烯基砜作為添加劑時,LiNi1/3Co1/3Mn1/3O2/Li電池的充放電容量不穩(wěn)定,并且?guī)靷愋食掷m(xù)低于100%,初步原因分析為加入EVS后,LiNi1/3Co1/3Mn1/3O2在充放電過程的不可逆程度增大以及電化學極化較嚴重。雖然EVS在1.2V左右能夠先于EC進行還原反應,但是未能對電池體系起到穩(wěn)定作用,對石墨負極的兼容性較差。
[Abstract]:With the wide application of lithium ion batteries, the system of high voltage lithium ion batteries has become a hot topic. As an important part of lithium ion batteries, electrolyte is facing challenges. On the one hand, the oxidation decomposition of the traditional carbonate electrolyte over 4.5V will occur. On the other hand, the new high voltage electrolyte has a variety of problems because of various problems. The stability of the electrolyte at high pressure directly affects the electrochemical performance of the battery. It is one of the key factors restricting the development of high voltage lithium ion batteries. According to the literature, one of the effective and economical solutions at the present stage is the introduction of a certain amount of functional additives (5%) in the electrolyte, which can stabilize the electrolyte. The high voltage lithium ion battery system improves the electrochemical performance. In this paper, the sulfone, which has high polarity, high oxidation potential and good thermal stability, is used as the research object, adding different additives in the 1M LiPF6-EC:DMC (1:1) reference electrolyte (Standard, STD) system through LiNi1/3CO1/3Mn1/3O2/Li, graphite /Li, and LiNi1/3Co1/3Mn1/3O2/ The cyclic voltammetry (Linear sweep voltammetry, LSV), cyclic voltammetry (Cyclic voltammetry, CV), electrochemical impedance (Electrochemical impedance spectroscopy, EIS), and scanning electron microscopy (Scanning) are used to test the cycle performance and ratio performance of the graphite battery system in different electrolyte systems. ), energy dispersive X ray spectroscopy (Energy dispersive X-ray spectroscopy, EDS) and X ray photoelectron spectroscopy (X-ray photoelectron spectroscopy, XPS) are used to characterize the effects of sulfone as additives on batteries. The main results are as follows: 1, sulfoxide as a high voltage electrolyte additive: (1) research When the addition amount is 2% (volume ratio), sulfoxide can improve the electrochemical window of the reference electrolyte and the oxidation stability of the enhanced electrolyte at high pressure, and reduce the reduction decomposition of the solvent carbonate (Ethylene carbonate, EC) to a certain extent. (2) the electrolyte containing sulfoxide is on the positive pole of the LiNi1/3CO1/3Mn1/3O2, Shi Mofu The discharge capacity, cycle performance and multiplying performance of LiNi1/3Co1/3Mn1/3O2/Li, graphite /Li and LiNi1/3Co1/3Mn1/3O2/ graphite battery systems are improved. (3) the mechanism of the improvement of the electrochemical performance of the sulphone battery is that the electrolyte containing sulphone can be on the positive and negative surface. A homogeneous membrane is formed to eliminate the cracks on the surface of the membrane and inhibit the continuous decomposition of the electrolyte, improve the stability of the electrolyte and electrode during the cycle, and reduce the increase of the impedance of the battery system during the cycle process, so that the battery performance is enhanced by.2, ethyl isopropyl sulfone (Ethyl isopropyl sulfone, EIS), ethyl vinyl group Ethyl vinyl sulfone (EVS) is used as additive: (1) when ethyl isopropyl sulfone is used as an additive, the electrochemical window of the reference electrolyte can be increased to 4.5V, and the discharge capacity of the LiNi1/3Co1/3Mn1/3O2 positive electrode charging and discharging at the cut-off voltage of 4.6V is greater and the ring is more stable, but the impedance of the battery in the cycle process is found. The increase amplitude is larger than that of the reference electrolyte, and the electrochemical performance of the graphite negative electrode in the system containing the additive is not ideal. (2) when ethyl vinyl sulfone is used as an additive, the charge and discharge capacity of LiNi1/3Co1/3Mn1/3O2/Li battery is unstable and the efficiency of Kulun continues to be less than 100%. The initial reason is that after adding EVS, LiNi1/3Co1/3Mn1/3O2 is in the process. The irreversible degree of charge and discharge process increases and the electrochemical polarization is serious. Although EVS can be reduced to EC before 1.2V, it can not play a stable role in the battery system, and the compatibility of graphite negative electrode is poor.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM912

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