【作者】 白莹；

【导师】 莫育俊；

【作者基本信息】 河南大学 ， 光学工程， 2005， 硕士

【摘要】 随着社会的发展,锂离子电池作为一种可循环利用的能源,人们对其电化学容量及可逆循环性能的要求越来越高。在锂离子电池首次充放电过程中形成的固体电解质中间相（Solid Electrolyte Interface Film,简称 SEI 膜）对锂离子电池的电化学容量、安全性、循环性、自放电等性能有十分重要的影响,并逐渐成为锂离子电池研究中的重要方向。 过渡金属化合物由于具有较高的储锂容量和崭新的储能机理,成为近些年锂离子电池负极材料中的研究热点。其中,Cr2O3既具有较高的电化学活性,又具有较低的平均工作电压,因此是较适合的锂离子电池负极材料。 原位研究是指用分析检测仪器直接对正在反应变化的体系进行测试,而不改变体系的实际状态,因此可以得到真实而准确的结果。由于 SEI 膜非常薄,并且接触空气后会很快变质,因此 SEI 膜的原位研究具有特别重要的意义。 本论文对Cr₂O₃负极材料表面的SEI膜进行了原位拉曼光谱研究。主要内容为: 1. 根据原位研究 SEI 膜的需要,设计制作了带石英光学窗口的锂离子模拟电池。测量时,由充放电仪控制实验电池的充放电状态,通过与共聚焦显微拉曼光谱仪的联用,可以实现电池中任一状态下 SEI 膜的拉曼光谱测量,以期得到较为完整而准确的 SEI 膜的组分和演化过程的信息。 2. 前人研究证明,SEI 膜的主要组分除了碳酸锂（Li₂CO₃）、氢氧化锂（LiOH·H₂O）和氟化锂（LiF）外,还有多种烷基锂（ROLi）和烷基脂锂（ROCO₂Li）等锂河南大学光学工程专业 2002 级硕士论文- II -盐存在。由于锂盐组分复杂且不稳定,难以从实验结果中直接确认 R 的具体形式,我们用量子化学方法计算了一系列可能在 SEI 膜中存在的物种的理论拉曼振动谱,以便于为实验结果的指认提供参照,并尝试分析可能存在于 SEI 膜中锂盐的具体组分和演化过程。3. 对包覆银岛膜前后 Cr2O3 表面非原位 SEI 膜的拉曼光谱进行了研究。包银前后SEI 膜的正常拉曼散射和表面增强拉曼散射（Surface Enhanced RamanScattering,简称 SERS）测量结果类似:充放电到低电位的拉曼谱峰比高电位时丰富得多,并且相对强度也较大,说明低电位时 SEI 膜较厚且成分复杂,这一趋势与电镜结果相吻合。随着第一周放电和充电过程的进行,Cr2O3 表面形成随电压动态演化的 SEI 膜。利用 SERS 方法得到的 SEI 膜拉曼信号较多且相对强度较大,更多的锂盐物种得到了增强而被观察到,说明银岛膜确实具有很强的增强效果。根据实验结果并结合理论计算,我们的结论是:在首次充放电过程中,利用 SERS 方法观察到先后有九种锂盐生成;而利用正常拉曼仅能够观察到五种锂盐的先后存在,这些物种不包括同时被观察到的早有报道的碳酸锂（Li2CO3）和氢氧化锂（LiOH·H2O）。4. 对包覆银岛膜前后 Cr2O3 表面原位 SEI 膜的拉曼光谱进行了研究,包银前后 SEI膜的正常拉曼光谱和 SERS 谱差别较大:未包覆银岛膜的原位拉曼测量得不到清晰的来自于 SEI 膜的信号,所测出的拉曼峰都可归属为电解液和电极材料本身的信号;而包覆银岛膜的原位 SERS 测量得到了很好的增强效果,随着第一周放电和充电过程的进行,Cr2O3表面形成随电压动态演化的 SEI 膜。与非原位 SERS 研究的结果类似:低电位的拉曼谱峰比高电位时丰富,并且相对强度也较大,说明低电位时 SEI 膜较厚且成分复杂,这一趋势与电镜结果相吻合。利用 SERS 方法得到的 SEI 膜信号丰富且相对强度较大,先后在不同状态下观察到了全部十六种不包括同时被观察到的碳酸锂（Li2CO3）和氢氧化锂（LiOH·H2O）的锂盐物种。5. 对原位和非原位拉曼光谱研究 SEI 膜的结果进行了比较。非原位 SERS 研究中,更多还原

【Abstract】 With the development of our society, further requirements such as higher electrochemical capacity and better reversibility are advanced to lithium ion battery, which is a kind of reversible energy. In the first cycle of lithium ion battery, solvent decomposition reaction on the surface of electrode will lead to the formation of a passivating layer, commonly named solid electrolyte interface film （SEI film）. It has great impact on the electrochemical capacity, security, reversibility, self-discharge and has become a focus in the study of lithium ion battery. Transition metal compound has been the focus as anode material in lithium ion battery since it has high lithium storage capacity and new energy storage mechanism. Thereinto, Cr₂O₃ is more fitting for its high electrochemical activity and low average working voltage. In-situ study can get real and accurate result through detecting the reacting system with detector directly without changing the real state and that makes great sense for SEI film since it is extraordinary thin and very sensitive to the environment. The in-situ Raman spectroscopy of SEI film on the anode material of Cr₂O₃ was studied in this paper: 1. To meet the needs of in-situ study of SEI film, the lithium ion simulate battery with optical quartz window was designed and made. The charge-discharge apparatus accurately control the state of battery when measuring, and we can realize the measurement and token of SEI film in an arbitrary state through co-employment with the co-focus micro-Raman spectroscopy. By this method we can obtain the information of the evolvement process . 2. It is believed that many kinds of ROLi and ROCO₂Li exist in the SEI film besides Li₂CO₃, LiOH·H₂O and LiF, while the lithium salts are difficult to be affirmed directly from the experiment for its complexity and instability. In this paper, a series of possibly existing species were calculated, and the Raman vibrational spectra were obtained. Through the comparison of the theoretical results and those from experiments, the components of the SEI film can be tentatively affirmed. 3. In order to gain active substrate of Surface Enhanced Raman Scattering（SERS）, we deposited Ag grain on the surface of Cr₂O₃ particles. The ex-situ Raman spectra of SEI film were studied both before Ag deposited and after that. The tendencies of normal Raman spectra and SERS were similar, the Raman peaks at low voltages were richer than those at high voltages, which accorded with the HRTEM results. It also demonstrated the dynamic transformation of SEI film in the first cycle. In the ex-situ SERS study, the SEI signals were richer and stronger, and more components were enhanced and be detected, which also indicated the great enhancement effect of the substrate. Took the theoretical results as references, we analyzed 9 lithium salts with SERS and 5 lithium salts with normal Raman, without considering Li₂CO₃ and LiOH·H2O reported before. 4. The in-situ Raman spectra of SEI film were studied both before Ag deposited and after that. The in-situ spectra of normal Raman and SERS were obviously different: the former can’t give any clear signal from SEI component and all Raman peaks measured can be assigned to electrode and anode material itself; the latter displayed great enhancement effect and the SERS signals of SEI film varied with the voltageslow voltages were richer than those at high voltages, which accorded with the HRTEM results. In the in-situ SERS study, the SEI signals were richer and stronger, and more components were enhanced and be detected. Took the theoretical results as references, we analyzed 16 lithium salts with SERS, without considering Li2CO3 , LiOH·H₂O reported before. 5. The comparison between the ex-situ and in-situ Raman study was also advanced. 9 components were detected in ex-situ SERS study in the first cycle with 16 components in the counterpart. The differences derived from the dissolution of some certain components into solvent in the sample preparation process. Our work at the same time demonstrated更多还原