Abstract
Lithium-ion (LIB) batteries, thanks to their high energy density and capacity, have enabled the development of new technologies ranging from consumer electronics to hybrid or fully electric vehicles. However, the increasing demand for energy consumption has led to the search for new and more efficient materials to further improve the current capabilities of LIB batteries. A crucial step in the further development of LIB is to understand the behavior of lithium in the cathodic side of the battery and to study its dynamics in a realistic configuration. To better understand the dynamics of (de)lithiation, an in-situ analysis at the primary particle scale in different cathode materials is proposed. The electrochemical liquid TEM analysis configuration [1] allows the performance of battery cycling inside the TEM for imaging at different SoC (state of charge), inducing less of perturbations during data acquisition and imaging analysis. The information obtained could reveal the behavior of lithium inside the crystallographic lattice for different compounds using 3DED technique, as well as other phenomena that lead to battery degradation. For example, in NMC 811, cathode degradation can occur due to the accumulation of stress in the primary particles. The stress is generated by the expansion of lattice parameters during cycling [2], and the accumulation of stress at the primary particle scale could lead to the generation of cracks in the cathode material. In this case, the 4DSTEM technique can be used. 3DED (3D Electron Diffraction) [3] is a technique that allows the reconstruction of the crystal structure of a material by acquiring multiple diffraction patterns at different tilt angles (2D data) to create a 3D map of the material. The 3D data must be processed and refined to avoid the artefacts produced by the TEM data acquisition conditions and to obtain less distorted results for crystal reconstruction. It is proposed to perform 3DED analysis on different SoC to follow the deformation and changes over the lattice as an indirect method to observe the (de)lithiation path during charge and discharge. 4DSTEM is an electron microscopy technique that allows to obtain structural information based on electron diffraction pattern collections [4-6]. Using this method, changes in lattice parameters can be detected by comparing the displacement between diffraction spots in diffraction patterns obtained during the cycle of an in-situ analysis. It is proposed to use 4DSTEM in-situ analysis on different SoC from non-cycled to failure to understand the influence of lithium behavior on the NMC cathode material and compare with literature.</br></br>References</br>1. F Wu and N Yao, Nano Energy 11 (2015), p 196. doi:10.1016/j.nanoen.2014.11.004</br>2. K Märker and PJ Reeves, Chemistry of Materials 31 (2019), p. 2545. doi:10.1021/acs.chemmater.9b00140</br>3. OM Karakulina et al., Nano letters, 18(10) (2018), p. 6286.</br>4. A Bhatia et al., Small Methods 6(2) (2022), p. 2100891.</br>5. N Folastre et al., Microscopy and Microanalysis 27(S1) (2021), p. 3446.</br>6. A Gomez-Perez et al., Microscopy & Microanalysis, 27(S1) (2021), p. 2234.