Raman Diagnostics of Cathode Materials for Li-Ion Batteries Using Multi-Wavelength Excitation

Abstract

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.

Monitoring electrode/electrolyte interfaces of Li‐ion batteries under working conditions: A surface‐enhanced Raman spectroscopic study on LiCoO2 composite cathodes

“…The left panel of Figure 3 and 597 cm À1 (A 1g ). 31,34 The broad bands at around 1340 and 1600 cm À1 originate from carbon black in the composite cathode and are attributed to the defect band (D) and to the C C stretching mode of graphite (G), respectively. 31 The additive PVDF of the composite cathode does not give a contribution to the Raman spectrum of the as prepared cathode, as evidenced by comparison with the spectrum of bare PVDF (see Figure S4).…”

“…The left panel of Figure 3 depicts the ex situ Raman spectrum of an as prepared LiCoO 2 composite cathode (yellow line), which is characterized by Raman bands of LiCoO 2 and carbon black. The Raman‐active modes of LiCoO 2 result in signals at 486 (E g ) and 597 cm −1 (A 1g ) 31,34 . The broad bands at around 1340 and 1600 cm −1 originate from carbon black in the composite cathode and are attributed to the defect band (D) and to the CC stretching mode of graphite (G), respectively 31 .…”

Synthesis and characterization of LiNi0,5Mn0,4Co0,1O2 as a cathode material for lithium-ion batteries using coprecipitation method

“…This is also a helpful machine to study the crystal chemistry and correlating phase changes and electrochemical properties [29]. To better understand the basic of the electrode structure, we report that layered cathode materials for LIBs can be studied in detail using multi-wavelength Raman spectroscopy [30]. In traditional Raman spectroscopy, the scattering intensity of solid materials depends on a number of variables, including the Raman cross section and Raman concentration, and typically shows a mild relationship on the excitation laser's wavelength [30].…”

“…To better understand the basic of the electrode structure, we report that layered cathode materials for LIBs can be studied in detail using multi-wavelength Raman spectroscopy [30]. In traditional Raman spectroscopy, the scattering intensity of solid materials depends on a number of variables, including the Raman cross section and Raman concentration, and typically shows a mild relationship on the excitation laser's wavelength [30]. It is crucial to remember that very low laser strengths are necessary for the Raman spectroscopy's accurate detection of the spinel phase.…”