Lithium-ion batteries have been commonly employed as power sources in portable devices and are of great interest for large-scale energy storage. To further enhance the fundamental understanding of the electrode structure, we report on the use of multi-wavelength Raman spectroscopy for the detailed characterization of layered cathode materials for Li-ion batteries (LiCoO2, LiNixCo1−xO2, LiNi1/3Mn1/3Co1/3O2). Varying the laser excitation from the UV to the visible (257, 385, 515, 633 nm) reveals wavelength-dependent changes in the vibrational profile and overtone/combination bands, originating from resonance effects in LiCoO2. In mixed oxides, the influence of resonance effects on the vibrational profile is preserved but mitigated by the presence of Ni and/or Mn, highlighting the influence of resonance Raman spectroscopy on electronic structure changes. The use of UV laser excitation (257, 385 nm) is shown to lead to a higher scattering efficiency towards Ni in LiNi1/3Mn1/3Co1/3O2 compared to visible wavelengths, while deep UV excitation at 257 nm allows for the sensitive detection of surface species and/or precursor species reminiscent of the synthesis. Our results demonstrate the potential of multi-wavelength Raman spectroscopy for the detailed characterization of cathode materials for lithium-ion batteries, including phase/impurity identification and quantification, as well as electronic structure analysis.

The potential of Raman and UV-Vis diagnostics for spatially-resolved and in situ diagnostics of lithium-ion batteries is demonstrated. Regarding the use of in situ Raman diagnostics focus is put on LiCoO2 electrode materials, which were investigated in detail as composites of LiCoO2 with binder and conductive additives. The potential of in situ UV-Vis analysis is illustrated for carbon-based materials showing significant absorption changes during electrochemical cycling due to lithium de-/intercalation.

Miniature x-ray sources present unique challenges due to the cost, power and space constraints placed upon them. One of the key functional differences from larger traditional x-ray tubes is that the x-ray spot is comprised of the entirety of the electrons produced by the filament without the benefit of active focusing elements in most cases. The result is an x-ray spot that is not well described by a traditional Full Width Half Maximum (FWHM) type of measurement due to the irregular nature of the spots. This paper presents an alternate method called an intensity integral curve that can be used in conjunction with a Gaussian FWHM measurement. The intensity integral curve gives important additional spatial information about the x-ray spot and more predictive power in how the x-ray spot on the tube may perform in a given application. The experimental setup, curve generation and curve interpretation are discussed for a number of currently available and prototype miniature x-ray sources. 1.

Lithium-ion batteries are commonly used for electrical energy storage in portable devices and are promising systems for large-scale energy storage. However, their application is still limited due to electrode degradation and stability issues. To enhance the fundamental understanding of electrode degradation we report on the Raman spectroscopic characterization of LiCoO2 cathode materials of working Li-ion batteries. To facilitate the spectroscopic analysis of the SEI (solid electrolyte interface) we apply surface-enhanced Raman spectroscopy by using Au nanoparticles coated with a thin SiO2 layer (Au@SiO2). We observe a surface-enhanced Raman signal of Li2CO3 at 1090 cm-1 during electrochemical cycling as an intermediate. Its formation/decomposition highlights the role of Li2CO3 as a component of the SEI on LiCoO2 composite cathodes. Our results demonstrate the potential of Raman spectroscopy to monitor electrode/electrolyte interfaces of lithium-ion batteries under working conditions thus allowing relations between electrochemical performance and structural changes to be established.

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