Correlative Electrochemical Microscopy of Li‐Ion (De)intercalation at a Series of Individual LiMn₂O₄ Particles

Abstract

The redox activity (Li‐ion intercalation/deintercalation) of a series of individual LiMn2O4 particles of known geometry and (nano)structure, within an array, is determined using a correlative electrochemical microscopy strategy. Cyclic voltammetry (current–voltage curve, I–E) and galvanostatic charge/discharge (voltage–time curve, E–t) are applied at the single particle level, using scanning electrochemical cell microscopy (SECCM), together with co‐location scanning electron microscopy that enables the corresponding particle size, morphology, crystallinity, and other factors to be visualized. This study identifies a wide spectrum of activity of nominally similar particles and highlights how subtle changes in particle form can greatly impact electrochemical properties. SECCM is well‐suited for assessing single particles and constitutes a combinatorial method that will enable the rational design and optimization of battery electrode materials.

Numerical simulations of cyclic voltammetry for lithium-ion intercalation in nanosized systems: finiteness of diffusion versus electrode kinetics

“…It can be easily verified that equation 4of Aoki et al [27] is equivalent to equation (3) of the present work provided g 1 = g 2 = g 3 = 0. Thus, it is interesting to use the kinetic parameter Λ and the finite space diffusion parameter w, introduced in that work, to analyze the degree of reversibility and finiteness of the diffusion space for the experimental conditions used in reference [15]. This kind of plot is useful, since from the knowledge of the diffusional and kinetic parameters, one can predict the type of behavior expected.…”

“…Now, we continue with the most relevant results from the present work. In this section, we will address the cyclic voltammetry of single LiMn 2 O 4 particles and thin film crystals with numerical simulations, comparing our results with experimental data from Mürter et al [16] and Tao et al [15]. We have adopted the parameter values for LMO used by Vassiliev et al [1], detailed in Table 1, which were fitted to experimental measurements with composite electrodes.…”

“…In the following set of calculations, m, S and d were adapted to model single particles and thin films of different sizes. With this purpose, we have used different film thicknesses, comparable to those of Reference [16], and selected different particle volumes from the supplementary information of Tao et al [15]. Figure 2 shows voltammograms for the case of planar diffusion, aimed to simulate thin film electrodes at different potential sweep rates.…”

“…Very recently, Tao et al [15] have performed for the first time experimental voltammograms for LiMn 2 O 4 (LMO) nanometric-sized individual particles of known geometry and nanostructure, using scanning electrochemical cell microscopy (SECCM). They found that structural and geometric properties of the particles impact on the electrochemical response, allowing characterization by sweep rates 2-4 orders of magnitude higher than those used with multi-particle systems (1 V.s −1 vs 0.1-10 mV.s −1 ).…”

“…The purpose of this work is to use numerical simulations to obtain theoretical voltammograms for LiMn 2 O 4 single particles and thin films of nanometric size in connection with the experimental works of Tao et al [15] and Mürter et al [16], and analyze the relevance of the nanometric size of the particles for the voltammetric response of the system. The results will be also discussed in the framework of the theoretical predictions of Aoki et al [27].…”