锂金属电池中隔膜润湿性研究

发布时间：2018-05-23 12:46

本文选题：锂金属电池 + 隔膜润湿性　；参考：《合肥工业大学》2017年硕士论文

【摘要】：锂金属电池具有比锂离子电池更高的能量密度。但锂金属负极存在的锂枝晶问题限制了锂金属电池的实用化。隔膜-电解液界面润湿性显著影响锂金属电池性能,特别是锂枝晶的生长。一方面,良好的隔膜润湿性有利于锂离子在隔膜微孔中的传导,从而减小电池内阻;另一方面,良好的隔膜润湿性有利于改善锂金属负极表面电流分布,促进锂金属在电极表面均匀沉积/脱出从而避免产生枝晶。本论文主要围绕隔膜-电解液界面润湿性展开研究。首先研究了电解液对隔膜润湿性的影响;其次开发了氟代醚、痕量水以及三嵌段有机非离子表面活性剂作为电解液添加剂来改善隔膜-电解液界面润湿性;最后考察了上述添加剂对锂金属电池电化学性能的影响以及在抑制锂枝晶上的应用。主要包括以下内容:第一章首先介绍了锂金属电池研究背景及研究进展,其次介绍了隔膜润湿性对电池性能的影响并综述了改善隔膜润湿性的一般方法。第二章主要介绍了本论文涉及到的实验药品、实验设备以及实验方法。第三章1)考察了碳酸酯类有机溶剂对隔膜润湿性的影响,研究结果表明:具有高粘度和高介电常数的溶剂更倾向于获得较差的隔膜润湿性;2)考察了具有不同阴离子结构的锂盐对隔膜润湿性的影响,研究结果表明:双三氟磺酰亚胺锂(LiTFSI)分子结构中由于含有极性很低的全氟烷基官能团(-CF3)能够有效减小电解液表面张力,从而获得良好的隔膜-电解液界面润湿性(特别是在高粘度电解液体系中);3)考察了当锂盐浓度变化时隔膜-电解液的界面润湿性,研究结果表明:随着锂盐浓度的上升,隔膜-电解液的润湿性越来越差,主要原因是电解液粘度的增加。第四章开发出1,1,2,2四氟乙基-2,2,3,3四氟丙基醚(HF2C-CF2-CH2-O-CF2-CF2H,F-EPE)、1H,1H,5H,八氟戊基-1,1,2,2四氟乙基醚(HF2C-CF2-CF2-CF2-CH2-O-CF2-CF2H,F-EAE)、痕量水(200ppm)以及聚氧化乙烯-聚氧化丙烯-聚氧化乙烯(HO-CH2-CH2-(O-CH2-CH2-)20-(O-CH(CH3)-CH2-)70-(O-CH2-CH2-)20-CH2-CH2-OH,P123)三嵌段非离子有机表面活性剂作为电解液添加剂来改善隔膜-电解液界面润湿性并研究了这些添加剂对锂金属电池倍率和循环性能的影响。实验结果表明:1)F-EAE和F-EPE添加量分别为2%(w/w)和5%(w/w)时对隔膜润湿性的改善作用最佳,隔膜吸液率由原来的30%分别提高到110%和105%,F-EAE添加量为2%时LiFePO4||Li电池10C(大充大放)条件下放电容量由原来的40 mAh g-1提高到110 mAh g-1;2)电解液中添加200ppm水并静置48小时后,隔膜的吸液率由原来的30%提高到100%,LiFePO4||Li电池10C(小充大放)条件下放电容量由原来的96 mAh g-1提高到115 mAh g-1;3)P123添加量为0.2%时隔膜的吸液率由原来的30%提高到了85%,此时隔膜电导率由原来的0.045 mS cm-1提高到0.50 mS cm-1。第五章在Cu||Li电池体系中考察了不同比例LiPF6-LiTFSI双盐电解液对锂金属沉积形貌的影响。发现随着隔膜-电解液界面润湿性变好锂金属在铜箔上沉积的表面形貌由最初的针状逐渐聚拢演变为岛状。本章中还考察了不同添加量的P123对枝晶的抑制作用,结果表明:P123添加量为0.2%时对枝晶的抑制作用最明显,CV和XPS分析发现P123能够在电极表面强烈吸附并作为一层“artificial SEI”对锂金属负极进行保护从而抑制锂枝晶和减少界面反应。在论文第六章中,对本论文的结论和创新之处进行了总结,分析了论文的不足之处,并对未来工作提出了展望。
[Abstract]:Lithium metal batteries have higher energy density than lithium ion batteries. However, the existence of lithium dendrite in lithium metal negative electrode restricts the practicality of lithium metal cells. The wettability of diaphragm electrolyte interface significantly affects the performance of lithium metal cells, especially the growth of lithium dendrites. On the one hand, good diaphragm wettability is beneficial to lithium ion in diaphragm. On the other hand, good diaphragm wettability is beneficial to improve the surface current distribution of the lithium metal negative electrode and promote the uniform deposition / release of lithium metal on the surface of the electrode to avoid dendrites. This paper mainly focuses on the wettability of the diaphragm electrolyte interface. The influence of wettability, followed by the development of fluoroether, trace water and three block organic nonionic surfactants as an electrolyte additive to improve the interfacial wettability of the electrolyte electrolyte. Finally, the effects of the additives on the electrochemical performance of lithium metal batteries and the application on the inhibition of lithium dendrites were investigated. The following contents were included: The first chapter introduces the research background and research progress of lithium metal battery. Secondly, it introduces the influence of the diaphragm wettability on the performance of the battery and summarizes the general methods to improve the wettability of the diaphragm. The second chapter mainly introduces the experimental drugs, experimental equipment and the method of testing in this paper. Third chapter 1) inspected the organic carbonates. The effect of solvent on the wettability of the diaphragm showed that the solvent with high viscosity and high dielectric constant was more inclined to obtain poor diaphragm wettability; 2) the effect of lithium salts with different anion structures on the wettability of the diaphragm was investigated. The results showed that the molecular structure of double three fluorsulfonimide (LiTFSI) has the polarity in the molecular structure. A very low perfluoroalkyl group (-CF3) can effectively reduce the surface tension of the electrolyte, thus obtaining a good diaphragm - electrolyte interface wettability (especially in the high viscosity electrolyte system). 3) the interfacial wettability of the diaphragm electrolyte is investigated when the concentration of lithium salts is changed. The results show that with the increase of the concentration of lithium salts, the diaphragm - electricity The wettability of solution is getting worse and worse, the main reason is the increase of viscosity of electrolyte. The fourth chapter developed 1,1,2,2 tetrafluoroethyl -2,2,3,3 tetrafluoropropyl ether (HF2C-CF2-CH2-O-CF2-CF2H, F-EPE), 1H, 1H, 5H, eight fluoramyl -1,1,2,2 tefluoroethyl ether (HF2C-CF2-CF2-CF2-CH2-O-CF2-CF2H, F-EAE), trace water (200ppm), and polyoxyethylene polyoxidation C Alkene polyvinyl oxide (HO-CH2-CH2- (O-CH2-CH2-) 20- (O-CH (CH3) -CH2-) 70- (O-CH2-CH2-) 20-CH2-CH2-OH, P123) three block non ionic organic surfactants as an electrolyte additive to improve the interfacial wettability of the electrolyte electrolyte and study the effects of these additives on the ratio and cycling performance of lithium metal batteries. Experimental results show that: 1) F-E When the addition of AE and F-EPE is 2% (w/w) and 5% (w/w) respectively, the improvement of the wettability of the diaphragm is the best. The absorption rate of the diaphragm is increased from 30% to 110% and 105% respectively. The discharge capacity of LiFePO4||Li battery 10C (large charge and large discharge) is increased from 40 mAh g-1 to 110 mAh g-1, and the addition of 200ppm water in the electrolyte is added at 2% when the F-EAE addition is 2%. After 48 hours of static, the absorption rate of the diaphragm was increased from 30% to 100%, and the discharge capacity of LiFePO4||Li battery 10C (small charge and large discharge) was increased from 96 mAh g-1 to 115 mAh g-1; 3) the absorption rate of the diaphragm was increased from 30% to 85% when the P123 addition was 0.2%, and the conductivity of the diaphragm was increased from 0.045 mS cm-1 to 0.50 mS. In the cm-1. fifth chapter, the influence of different proportion of LiPF6-LiTFSI double salt electrolyte on the deposition morphology of lithium metal was investigated in the Cu||Li battery system. It was found that the surface morphology of the lithium metal deposited on the copper foil was gradually changed from the initial needle shape to the island with the wettability of the diaphragm electrolyte interface. In this chapter, the different additions of P1 were also investigated. The inhibitory effect of 23 on dendrites shows that the inhibition effect on dendrites is the most obvious when the addition of P123 is 0.2%. CV and XPS analysis found that P123 can strongly adsorb on the surface of the electrode and protect the lithium metal anode as a layer of "artificial SEI" to inhibit the lithium dendrite and reduce the interfacial reaction. In the sixth chapter of the paper, the paper The conclusions and innovations are summarized, the deficiencies of the paper are analyzed, and the future work is prospected.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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