Sedimentation of opaque suspensions of carbon black and lithium-iron-phosphate was investigated by spin-echo-based magnetic resonance imaging. Optical methods are usually applied to determine settling velocities, but are limited with respect to high concentrations and optical transparency. The presented method uses intensity data from the noninvasively measured magnetic resonance signal of the sample. The settling velocity is obtained from the evolution of the signal intensity profiles based on the contrast in 1 H magnetic resonance imaging between particles and liquid. New insights into the sedimentation in opaque suspensions are provided, since the 1 H images uncover the spatial distribution of the particles and its agglomerates, as well as the shape of the settling front. Additionally, the sedimentation was experimentally studied using a sedimentation balance, which gravimetrically measures the increase in mass fraction over time due to the settling of particles. By parallel usage of these two methods, the sedimentation processes of opaque suspensions of lithium-ionbattery electrode materials were investigated. The sedimentation balance covers high, technically relevant concentrations. Limiting factors of the methods are discussed, which are mainly signal intensity in the magnetic resonance imaging and the increasing viscosity of highly concentrated suspensions.
The impact of electrode formation is studied by the spatially and time‐resolved distribution of transverse relaxation. In situ 7Li nuclear magnetic resonance experiments are performed on an experimental lithium‐ion battery cell to study the impact of electrode passivation via imaging and transverse relaxation in the interelectrode volume. The electrolyte in the battery, using technically relevant electrode material, i.e., graphite and lithium–nickel–cobalt–manganese–oxide, is studied by 2D magnetic resonance imaging. The electrolyte is 1 mol L−1 lithium hexafluorophosphate dissolved in a binary mixture of ethylene carbonate and dimethyl carbonate. 1D profiles are acquired and related to 7Li concentration during passivation and during a constant current/constant voltage cycle. The transverse relaxation rate R2(z,t) measured by multiecho profiles revealed changes within the electrolyte volume. The ongoing process changes the relaxation distribution. Indications for a defective electrode passivation are deduced from the data. During one charging cycle with constant current/constant voltage, the lithium concentration is measured spatially resolved, and the data are modeled by the Nernst–Planck equation.
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