Homogeneity Measurements of Li-Ion Battery Cathodes Using Laser-Induced Breakdown Spectroscopy

Abstract

We study the capability of nanosecond laser-induced breakdown spectroscopy (ns-LIBS) for depth-resolved concentration measurements of Li-Ion battery cathodes. With our system, which is optimized for quality control applications in the production line, we pursue the goal to unveil manufacturing faults and irregularities during the production process of cathodes as early as possible. Femtosecond laser-induced breakdown spectroscopy (fs-LIBS) is widely considered to be better suited for depth-resolved element analysis. Nevertheless, the small size and intensity of the plasma plume, non-thermal energy distribution in the plasma and high investment costs of fs-LIBS make ns-LIBS more attractive for inline application in the industrial surrounding. The system, presented here for the first time, is able to record quasi-depth-resolved relative concentration profiles for carbon, nickel, manganese, cobalt, lithium and aluminum which are the typical elements used in the binder/conductive additive, the active cathode material and the current collector. LIBS often causes high variations in signal intensity from pulse to pulse, so concentration determination is, in general, conducted on the average of many pulses. We show that the spot-to-spot variations we measure are governed by the microstructure of the cathode foil and are not an expression of the limited precision of the LIBS setup.

Depth-Resolved Elemental Analysis on Moving Electrode Foils with Laser-Induced Breakdown Spectroscopy

“…As the spectra of single pulses show a big variance, from pulse-to-pulse spectra from 400 positions with 10 spectra at each position (depth profile) were averaged. Pulse-to-pulse variations are mainly due to the distribution of the NMC beads [ 20 ].…”

“…With no average, a high variation is seen due to inherently inhomogeneous distribution of NMC beads (see [ 20 ]). For the monitoring of a global demixing of NMC and graphite, e.g., in the drying process of the cathode, a higher average might be useful.…”

“…However, it is important for stability and performance of the battery cell that the constituents NMC, binder and graphite are homogeneously distributed within the thickness of the layer [ 19 ]. By comparing electron microprobe analysis of cathode cross-sections with LIBS measurements, we showed that fluctuations in the normalized LIBS spectrum are dominated by the inhomogeneity of the dispersion [ 20 ]. The relevant parameter for the homogeneity to be measured is the 3D distribution of the carbon–NMC ratio.…”

Atomic spectrometry update: review of advances in the analysis of metals, chemicals and materials

“…Two papers by the same research group have reported the use of LIBS for homogeneity measurements of lithium ion batteries 226 and for depth-resolved elemental analysis on moving foils. 227 In the former paper, a LIBS system operating at 1064 nm, a pulse duration of 6 ns and a varied pulse energy of between 0.25 and 50 mJ was used.…”

Characterization of Functional Coatings on Cork Stoppers with Laser-Induced Breakdown Spectroscopy Imaging

“…Moreover, due to the small spot size of LIBS (down to the µm range), this technique can be used for spectral imaging as it allows for high-resolution pointwise analysis. LIBS imaging has been applied in all sorts of fields such as geology [10][11][12], biology [13][14][15], batteries [16,17], heritage [18] and more [13,19], making it a well-established technique and a strong candidate for the surface analysis of cork stoppers.…”