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铝沉积和锂离子电池电解液中添加剂的作用及机理研究
Alternative TitleResearch on the Function and Mechanism of Additives in Aluminium Electrodeposition and Lithium Ion Battery Electrolyte System
刘恋
Subtype博士
Thesis Advisor张锁江
2014-04
Degree Grantor中国科学院研究生院
Degree Discipline化学工艺
Keyword添加剂   电解液   电沉积   锂离子电池   电化学原位装置
Abstract电解液在电化学反应过程中起到了重要的支撑作用,是电解、电镀的反应介质,被喻为电池的“血液”。添加剂作为电解液的重要组成部分,在电化学反应过程中起到了修饰、改善形貌及提高物化性能的作用。例如在电解、电镀过程中起到了降低反应温度、整平、细晶等作用,在锂电池电解液中可以起到修饰SEI膜、提高电导率、除水、降酸、阻燃、限压等作用,从而改善电池的倍率、高低温、循环、安全等性能。目前添加剂种类繁多、性能单一、作用机理不明,难以满足研发及生产的需求,因此添加剂的多功能化及作用机理即成为研究热点。本文系统研究了五类添加剂在氯铝酸盐离子液体电解液中对铝沉积层纯度、形貌、结构的优化作用。设计合成了以烟酰胺为代表的新型多功能添加剂,研究其在锂离子电池中的性能及作用机理。得到如下主要结论: (1) 选用[Bmim]Cl/2AlCl3离子液体为低温电沉积铝电解液体系。无添加剂的情况下电沉积铝的过程属于准可逆过程,为受扩散控制的三维瞬时成核机理。分别考察了无机金属氯化物、稀土元素氯化物、小分子有机添加剂、大分子有机添加剂、多种添加剂混合物这五大类添加剂对电沉积过程的影响。其中,无机氯化物添加剂易与铝形成共沉积;有机添加剂对沉积层纯度无影响,同时具有很好的细晶作用;复合添加剂LaCl3-NH4Cl-C6H12可以有效改善沉积层质量,获得纳米级铝沉积层,并可将铝纯度从99.795 %提高至99.95 %,达到精铝级别。 (2) 以玻璃碳为惰性阳极进行离子液体低温电解铝实验。在不使用添加剂时,随着电解电位的增大铝在阴极的成核经历了由连续成核到瞬时成核的过程,电解铝产品粗糙、纯度较低。加入复合添加剂LaCl3-NH4Cl-C6H12后,铝呈层状生长,沉积层具有银白色金属光泽,且纯度可以达到99.994 %的精铝级别。 (3) 通过筛选有机胺类化合物,确定采用可与水形成稳定氢键(O…H-O和N-H…O)、除水效果明显、无副反应的酰胺类添加剂作为锂离子电池电解液稳定剂。此外,酰胺类添加剂具有明显的成膜性能,可以在溶剂分解前形成SEI膜。在循环性能测试中,加入0.5 % N-甲基乙酰胺可将容量保持率由91.67 %提高至95.99 %,同时内阻明显降低。 (4) 研究了烟酰胺、丙烯酰胺、N,N-亚甲基双丙烯酰胺三种新型添加剂的作用机理及性能。实验发现烟酰胺除了具有显著的除水降酸作用,还可以在电极表面形成优质的SEI膜。烟酰胺可使电解液的酸值在50 天内保持不变,明显优于其他添加剂体系。加入0.1 %的烟酰胺即可促进电极表面成膜,100次循环后容量保持率可达95.92 %,提高锰酸锂电池的循环和倍率性能,同时内阻较低。 (5) 根据以上两种电解液的电化学特性,设计并制作了“电化学过程原位研究装置”和多功能原位光电化学池,建立了一种简便高效的电化学过程原位研究与评价平台。
Other AbstractElectrolyte is a kind of material with ionic conductivity and plays an important role in electrochemical reaction process. In practice, the industry of batteries, electrolysis, electroplating is related to the electrolyte. As an important component of the electrolyte, additives significantly effect on modification, improvement of performance in the electrochemical reaction process. For example, the reaction temperature of electrolysis can be reduced by adding additives. And the additives prominently influence the morphology and grain parameters of the deposits. In lithium ion battery electrolyte, the functional additives can modify SEI film, improve electrical conductivity, dehydrate, reduce acidity, flame retardant and limit voltage. Then, the performance of high ratio discharge property, cycle stability, high and low temperature and security can be improved. Nowadays, multi-functional additive is brought into research hotspot in the field of electrolyte. The systematic analysis of additives affecting the purity, morphology, structure in [Bmim]Cl/2AlCl3 ionic liquids for Al electrodeposition has been carried out. And a new type of multifunctional additive has been designed, which is represented by nicotinamide. The effect of functional additives on mechanism and properties in electrolytes were investigated in this work. The main conclusions as following: (1) [Bmim]Cl/2AlCl3 ionic liquid is used as electrolyte for electrodeposition of aluminum at low temperature. In the additive free system, deposition of aluminum process is quasi reversible and the nucleation mechanism of aluminum is controlled by the diffusion of three-dimensional instantaneous nucleation process. Five kinds of additives included inorganic metal chloride, rare earth chloride, small molecule organic, macromolecular organic and mixed additives are investigated in this work. The inorganic chloride additives are apt to codeposition with aluminum. Organic additives unable affect the purity, and have a role in densification and homogenization. Composite additive (LaCl3-NH4Cl-C6H12) can significantly improve the deposit quality, and obtain nano aluminum deposits. Compare with additive free system, the purity of aluminium is elevated from 99.795 % to 99.95 % with adding LaCl3-NH4Cl-C6H12. (2) Glass carbon is used as inert anode for electrolytic aluminium. In additive free system, the nucleation process experienced continuous nucleation to instantaneous nucleation process with increase of potential, but aluminium deposit with low purity and rough morphology. The use of composite additive LaCl3-NH4Cl-C6H12 can make the aluminum deposit present silvery lustre and the purity of aluminum can be up to 99.994 %. (3) Using organic amine additive as stabilizers in lithium ion battery electrolyte. It is found that the amide additives possess obvious effects of dehydration function, and form stable hydrogen bonds (O…H-O, N-H…O). At the mean time, amide additives have remarkable film forming performance. Adding the concentration of 0.5 % methylacetamide into electrolety can enhance the capacity retention from 91.67 % to 95.99 %, and significantly reduce internal resistance. (4) Nicotinamide, acrylamide and N,N-methylenebisacrylamide are used as novel multifunctional additives. The results have shown that electrolyte with additing nicotinamide incorporation can be stable for over 50 days without HF change and precipitation. The addition of 0.1 % niacinamide can improve capacity retention to 95.92 % after 100 cycles. Therefore, niacinamide can be used as difunctional additive to improve performance of lithium ion battery. (5) According to the electrochemistry features of electrolyte, design and construction of in situ electrochemical device and photoelectric chemical pool. Establish a simple and effective in situ electrochemical research and evaluation platform.
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15527
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
刘恋. 铝沉积和锂离子电池电解液中添加剂的作用及机理研究[D]. 中国科学院研究生院,2014.
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