Spatially and temorally resolved in situ Raman spectroscopy of cathode materials of Li-ion batteries

锂离子电池已被用作各种现代IT应用的移动储能设备。锂离子电池在电动汽车(电动汽车和混合动力汽车)以及用作固定能源方面的未来应用也非常令人感兴趣。然而，特别是在后一种应用方面，将需要进一步的技术开发。合理开发具有更高能量密度和稳定性的锂离子电池，是基于对其工作模式的基本了解。这需要开发和应用新的实验方法，以便在工作条件下对电池进行详细分析。本项目的目标是通过空间分辨分析来研究锂离子电池正极材料LiCoO2和Li(NiMnCo)O2(NMC)的工作模式。除了研究正极材料的动力学外，还将侧重于对单个粒子的研究。为了考虑碳添加剂和粘结剂材料的影响，将正极材料作为由活性物质、碳添加剂和聚偏二氟乙烯粘结剂组成的正极混合物进行研究。主要的研究方法将是共振增强的原位拉曼显微镜，它将被用于空间分辨实验(拉曼图谱)和对单个粒子的测量。由于共振增强的优化、表面增强拉曼光谱(SERS)的使用以及原位池设计的改变，该方法的灵敏度有望显著提高。这些研究将得到其他方法的支持，如红外光谱、紫外可见光谱和X射线光电子能谱。研究的重点之一是在工作条件下对单个颗粒进行分析。通过这种方式，我们打算探索单个粒子的电荷状态和动力学的差异。这些基础研究对观察到的LiCoO2和NMC正极材料的疲劳非常感兴趣。设想研究的另一个重点是正极材料的异质性及其动力学。在这种背景下，我们打算探索不同的阴极混合物(即碳类型的变化)对行为的影响程度。作为深入了解LiCoO2和NMC正极材料工作模式的另一种方法，原子层沉积(ALD)将用于制备特定的Al_2O_3涂层。为此，通过原位分析，我们希望能够通过与未涂层材料的比较来阐明涂层对正极材料行为的积极影响的来源。

Li-ion batteries have been used as mobile energy storage devices for a variety of modern IT applications. Li-ion batteries are also of great interest for future applications in electro mobility (electrical and hybrid vehicles) and for use as stationary energy sources. However, in particular regarding the latter applications, further technological developments will be necessary. A rational development of Li-ion batteries with higher energy density and stability is based on a fundamental understanding of their mode of operation. This requires the development and application of new experimental approaches allowing for a detailed analysis of the battery under working conditions. It has been shown that Raman microscopy has the potential to provide new insight into the mode of operation of Li-ion batteries, in particular, when it is used for spatially-resolved analysis.The goal of the project is to gain new insight into the mode of operation of LiCoO2 and Li(NiMnCo)O2 (NMC) cathode materials for Li-ion batteries using spatially-resolved analysis under working conditions of the battery. Emphasis will be put on studies of individual particles besides studies on the dynamics of the cathode materials. To take the influence of the carbon additive and binder material into account, cathode materials will be investigated as cathode mixes consisting of active mass, carbon additive and polyvinylidendifluoride binder. The main method of investigation will be resonance-enhanced in situ Raman microscopy, which will be employed for both spatially-resolved experiments (Raman mapping) and measurements on individual particles. A significant increase in the sensitivity of the method is expected from the optimization of the resonance enhancement as well as the use of surface-enhanced Raman spectroscopy (SERS) and changes in the in situ-cell design. These studies will be supported by other methods such as IR, UV-Vis and X-ray photoelectron spectroscopy.One focus of the investigations is the analysis of individual particles under working conditions. In this way, we intend to explore the differences in the state of charge and dynamics of the individual particles. Such fundamental studies are of great interest regarding the observed fatigue of LiCoO2 and NMC cathode materials. Another focus of the envisaged investigations is the heterogeneity of the cathode materials as well as its dynamics. In this context, we intend to explore, to which extent the behavior is influenced by different cathode mixes (i.e. variation in type of carbon). As an alternative approach to gain insight into the mode of operation of LiCoO2 and NMC cathode materials, atomic layer deposition (ALD) will be employed to prepare defined Al2O3 coatings. To this end, by using in situ analysis, we expect to be able to elucidate the origin of the positive influences of the coatings on the behavior of the cathode materials by comparison with uncoated materials.