非水电解质组份的量子化学研究及在锂离子电池中的应用

【作者】 薛照明；

【导师】 陈春华；

【作者基本信息】 中国科学技术大学 ， 材料学， 2007， 博士

【摘要】 锂盐是锂离子电池电解质中的主要成分，开发高性能锂离子电池必须研制新的锂盐。新型锂盐研究的重点是寻找与Li~+配位的合适的阴离子，从而得到具有热化学和电化学特性优良的锂盐。弄清锂盐结构与性能的关系(quantitative structure—property relationships—QSPR)来为实验研究者提供指导作用并为其节省时间和资源，量子化学指导下的计算机模拟就是一个行之有效的方法。实际上，锂盐分子的阴离子结构、离子对的相互作用在决定它在有机溶剂中的溶解性、离子导电率、电化学窗口和热稳定性方面起着内在的作用，所以对锂硼盐的电子结构、能量和轨道进行充分的计算研究，可以在量子化学水平上加深对其特性的理解。本论文研究旨在：一方面对电解质的结构与性能的关系做系统性的研究，另一方面对理论指导下实际锂盐的设计、合成及实验的结果进行研究。在论文的第一、二、三章中，综述了锂盐的研究现状；其中包括锂盐的分类、合成方法、热化学及电化学性能的实验结果。也包括了量子化学方法从理论上对分子结构及结构与性能关系的研究，尤其是在分子的IR、NMR、热稳定性、电导率及电化学窗口的方面的理论研究。在论文第四章中，提出了本工作的研究方法，研究对象及主要研究内容，对后续的研究工作进行了总体设计。为了寻找对锂盐合适的量子化学研究方法及性能良好的锂盐应具备的共性，论文第五章详细地研究了氮方酸衍生物的强酸性和芳香性。包括了酸性和芳香性的判据和判断结果，为寻找较高电导率的锂盐准备了计算方法和明确了配合物的结构特点。为了系统地研究锂盐的分子结构与电解质的关系，论文第六、七、八三章系统地从理论上研究了方酸及其氰基亚氨基衍生物、方酸及其二氰亚甲基衍生物、克酮酸及其二氰亚甲基衍生物等各系列电解质分子(阴离子)结构、分子结构与电导率、阴离子结构与电化学稳定性的关系。在论文第九章中利用前述有关研究方法，对已有合成报道的锂盐LBBB及其衍生物进行了详细理论研究，分析了此类锂盐的分子结构与电子结构。从理论上阐述了该类锂盐的热稳性、溶解性、导电性及电化学稳定性与分子结构关系的本质。在上述理论结果的指导下，论文第十章选择了克酮酸二价阴离子——具有很强的酸性、较好的芳香性、较大的电荷分散性、形成的配合阴离子具有较显著的共轭性——作为配体与B配位，合成了二种新的锂盐(LBCB和LCSB)，通过实验测定了它们的结构和在有机溶剂中的溶解性。测试了这些锂盐的热分解温度、电导率和电化学窗口，并和已报道的同类锂盐LBSB进行比较，从实验上证明了前述理论研究的正确性。为了更好地说明新合成的锂盐(LBCB和LCSB)性能与结构关系，论文第十一章用前述的理论方法研究了这些新的锂盐。所得结果与前述理论研究结果完全一致。最后，第十二章对本论文所取得的成果及存在的不足作了简要的总述，并对今后可能的研究方向进行了展望和提出了建议。更多还原

【Abstract】 The lithium salts are the important part of lithium ion containing electrolyte. So we have to develop new lithium salts to save the necessary of manufacturing lithium ion batteries. The focus on the development of the novel lithium salts has been placed on seeking proper anions for coordination with lithium cation to obtain desired species with appropriate chemical and electrochemical property.Getting the quantitative structure-property relationships（QSPR） to guide experimental scientists research and to save their time and costs, Quantum chemistry calculation can in many cases be a successful method applied to lithium salts. Because the anion-cation interaction within the lithium salts plays an important role in determining to the solubility, ionic conductivity, electrochemical windows and thermal stability, a thorough computational investigation on the electronic structures, energies, and orbitals of the lithium salts would be desirable to better our understanding their properties at a quantum chemistry level.The main concerns of the present work are as follows: more systematic research of the quantitative structure-property relationships for electrolytes; the research on design, synthesis, and the experimental results of lithium salts guided by the theoretical results.In chapter 1, 2 and 3 of thesis, reviewed the present research situation of lithium salt. Including the classification of lithium salt, methods of synthesis, experimental results of thermal- and electro-chemistry. Also it is included that the theoretical research by the quantum chemistry’s method in molecular structure and quantitative structure-property relationships, particularly in the aspect of IR, NMR, thermal stability, electric conductivity and electrochemistry window.In the thesis chapter 4, it was put forward that research method of this work, research object and main research contents. We also carried on a total design to the follow-up research work in this chapter.Looking for the suitable quantum chemistry calculation method and the structure common feature of novel lithium salts, the gas-phase acidity and aromaticity of nitrogen squaric acid and its dimeric derivative were studied in the thesis chapter 5. The study included judge of acidity and aromaticity according to the criteria. According to the results, the suitable calculation method and the structure common feature for the lithium salt with a higher electric conductivity were gotten.For systematically studying the quantitative structure-property relationships for electrolytes, the thesis chapter 6, 7 and 8 systematically studied molecular（anions） structure and quantitative structure-property relationships, including the relationship between molecular structure and conductivity, anions structure and electrochemistry stability, on anions of 1,2-Dihydroxycyclo-pentenetrione （croconic acid, H₂C₅O₅） and the whole series of dicyanomethylene derivatives, anions of 1,2-dihydroxycyclobuten- 3,4-dione （squaric acid, H₂C₄O₄） and the whole series of dicyanomethylene derivatives, and anions of 1,2-Dihydroxy-cyclobuten- 3,4-dione （squaric acid, H₂C₄O₄） and the whole series of dicyanomethylene derivatives.Using of the above relevant research methods in the thesis chapter 9, we carried on detailed theoretical researches to lithium salt LBBB and its derivatives, which have already been synthesized and reported, and analyzed molecular structure and electronics structure of this kind of lithium salt. We also elaborated the essence of the relationships between the property （thermal stability, solubility, electric conductivity, and electrochemical stability window） and the structure.Under the instruction of above-mentioned theoretical results, in the thesis chapter 10, the strongly electron-withdrawing anion, C₅O₅^2-[dianion of croconic acid （4,5-dihydroxycyclopent-4- ene-1,2,3-trione）], was chosen as the chelator to coordinate with boron to form lithium salt, which will yield high ionic conductivity solutions, and exhibit wide electrochemical stability windows and high thermal stability. As described in the chapter, two new lithium salts containing C₅O₅^2-, lithium bis[croconato]borate （LBCB） and its novel derivative, lithium [croconato salicylato]borate （LCSB） for Li-ion battery electrolytes were synthesized. Their thermal and electrochemical stabilities, conductivities in solvent mixtures were studied and compared with those in the LBSB electrolyte. The results proved from the experiment the above theoretical study of accuracy.For better explaining quantitative structure-property relationships of the lately synthesized lithium salts （LBCB and LCSB）, in the thesis chapter 11, we studied these new lithium salts with the above theoretical method. The results were completely consistent with the foregoing theoretical results.Finally, in the 12^th chapter, the author gives a general overview on the achievements and the deficiency in this thesis. Some prospects and suggestions of the possible future research directions are pointed out.更多还原