Quantitative characterization of the ionic mobility and concentration in Li-battery cathodes via low frequency electrochemical strain microscopy

Abstract

Electrochemical strain microscopy (ESM) can provide useful information on the ionic processes in materials at the local scale. This is especially important for ever growing applications of Li-batteries whose performance is limited by the intrinsic and extrinsic degradation. However, the ESM method used so far has been only qualitative due to multiple contributions to the apparent ESM signal. In this work, we provide a viable approach for the local probing of ionic concentration and diffusion coefficients based on the frequency dependence of the ESM signal. A theoretical basis considering the dynamic behavior of ion migration and relaxation and change of ion concentration profiles under the action of the electric field of the ESM tip is developed. We argue that several parasitic contributions to the ESM signal discussed in the literature can be thus eliminated. The analysis of ESM images using the proposed approach allows a quantitative mapping of the ionic diffusion coefficients and concentration in ionic conductors. The results are validated on Li-battery cathodes (LiMnO) extracted from commercial Li-batteries and can provide novel possibilities for their development and further insight into the mechanisms of their degradation.

Local Study of Lithiation and Degradation Paths in LiMn2O4 Battery Cathodes: Confocal Raman Microscopy Approach

“…Spatially resolved imaging of these shifts reveals an inhomogeneity of the lithiated phase in the middle of the particles, producing a core structure, while shell is enriched by lithium ( Figure 2). This observation is in line with recent electrochemical strain microscopy measurements in the same material [14]. the delithiated samples we also observed Raman band around of 680-690 cm −1 , which cannot be related to LMO vibration modes.…”

“…Spatially resolved imaging of these shifts reveals an inhomogeneity of the lithiated phase in the middle of the particles, producing a core structure, while shell is enriched by lithium ( Figure 2). This observation is in line with recent electrochemical strain microscopy measurements in the same material [14]. Though Raman band position can be used as a signature of the lithiation state, the accuracy of this approach is not very high due to the apparent difficulties in the precise evaluation of the peak positions in complex Raman spectra with many overlapped peaks.…”

Quantitative Electromechanical Atomic Force Microscopy

“…66 Resonance tracking techniques allow the determination of the driving force or strain in PFM/ESM by accounting for any change in the contact resonance frequency or quality factor, analyzed in terms of the simple harmonic oscillator (SHO). With few exceptions 32 71 , and tall tips. 25 Often, however, the tip-sample stiffness required to eliminate electrostatic effects is sufficiently large to compromises the material, particularly important for fragile thin films or biological materials.…”

Recent Progress in the Nanoscale Evaluation of Piezoelectric and Ferroelectric Properties via Scanning Probe Microscopy

“…Therefore, ferroelectriclike hysteresis loops can be formed in non-ferroelectric materials, such as LiCoO 2 and lithium-ion conductors. [104][105][106][107][108] These results revealed that it is likely to misinterpret the ionically mediated PFM hysteresis loop as ferroelectricity. Accordingly, several studies have distinguished these aspects from each other based on voltage conditions, harmonic responses, and environmental conditions.…”