(Invited) In Situ Monitoring of Mechanical Properties Via Multi-Length Scale Approach

The in situ multi-length scale methodology creates new insights for the correlation of structural changes on the (sub-) nanometer scale with the resulting behavior of a bulk electrode in batteries and supercapacitors. The primary atomic-scale effect of Li-ion intercalation-induced changes of the unit cell volume or ion insertion between layered materials generates mechanical stress. [1, 2] This electrochemical process occurs during charging and discharging, meaning insertion and extraction of ions, generating a variety of secondary multiscale dimensional changes and causes a deterioration in the energy storage performance stability. [3] A complementary approach to monitor structural changes with in situ x-ray diffraction (XRD), microscopic changes with in situ atomic force microscopy (AFM), mesoscopic changes with hydrodynamic spectroscopy via electrical quartz microbalance measurements with dissipation monitoring (EQCM-D) and macroscopic changes with electrical dilatometry (eD) was chosen. [1, 4] We combined the results of this in situ measurement techniques. By this way, it is possible to correlate structural changes on the (sub-) nanometer scale with the resulting behavior of a bulk electrode in batteries and supercapacitors. We have proved the particularly understanding of ion intercalation into two-dimensional materials and a better understanding of the related mechanisms in composite electrodes. 1. Jäckel, N., et al., Electrochemical in Situ Tracking of Volumetric Changes in Two-Dimensional Metal Carbides (MXenes) in Ionic Liquids. ACS Applied Materials & Interfaces, 2016. 8 (47): p. 32089-32093. 2. Thackeray, M., Lithium-ion batteries: An unexpected conductor. Nature Materials, 2002. 1 (2): p. 81-82. 3. Shpigel, N., et al., Non-Invasive In Situ Dynamic Monitoring of Elastic Properties of Composite Battery Electrodes by EQCM-D. Angewandte Chemie International Edition, 2015. 54 (42): p. 12353-12356. 4. Shpigel, N., et al., In situ hydrodynamic spectroscopy for structure characterization of porous energy storage electrodes. Nature Materials, 2016. 15 (5): p. 570-575. Figure 1: Different characteristic length scales for certain in situ measurement techniques. Figure 1