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.

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This paper reports about new insight into a problem of a laser–matter interaction during Raman probing of lithium iron phosphate (LiFePO4), discusses phase transformation kinetics in powder samples, and provides some methodological recommendations. LiFePO4 is the second most popular positive electrode material in the global lithium battery industry, but the use of Raman spectroscopy for its structural characterization is hampered by the laser‐induced degradation. The statistical/big‐data approach to Raman spectra measurements is utilized to revise the problem and suggest a simple model of laser‐induced phase transformations in powder LiFePO4. The results are proposed to be used for better understanding of the physics and chemistry of other processes taking place in electrochemical cells, namely, lithiation/delithiation and thermal stability/safety studies. Simple recommendations for nondestructive LiFePO4 characterization by Raman spectroscopy are formulated.

Lithium manganese-based cathodes are widely used in rechargeable batteries due to their low cost, safety, and ecological stability. On the other hand, fast capacity fade occurs in LiMn 2 O 4 mainly because of the induced manganese dissolution and formation of additional phases. Confocal Raman microscopy provides many opportunities for sensitive and spatially resolved structural studies of micro-and nanoscale phenomena. Here, we demonstrate advantages of confocal Raman spectroscopy approach for uncovering the mechanisms of lithiation/delithiation and degradation in LiMn 2 O 4 commercial cathodes. The analysis of Raman spectra for inspecting local lithiation state and phase composition is proposed and exploited for the visualization of the inhomogeneous distribution of lithium ions. The cycling of cathodes is shown to be followed by the formation and dissolution of the Mn 3 O 4 phase and local disturbance of the lithiation state. These processes are believed to be responsible for the capacity fade in the commercial batteries.