Research

Materials Imaging & Integration

Ionics

Goal

  • To advance the understanding of ionic/electronic properties and elucidate their underlying mechanisms

  • To observe and visualize the electrochemical phenomena on the battery materials at the nano and microscale, and connect them with the bulk scale analysis results

Approach

  • Visualize the change in electrode surfaces during cycles by in-situ EC-AFM

  • Characterize the properties of the Solid electrolyte interphase(SEI) layer under various environmental conditions by ex-situ AFM measurement

  • Distinguish and analyze the battery materials at the surface and image in 3D as a function of parameters by depth profiling

Impact

  • Contribute to the advancement of the combination between electrode/electrolyte

  • Unique and original analyzing methods via various advanced AFM modes applied to secondary battery systems

Visualization of lithiation sites in SWCNT via KPFM. (a) Schematic image of a KPFM tip on a SiO active material showing the work function change between Ø_𝑠1 and Ø_𝑠2 during cycling as well as the isolated work function domain (Ø_𝑠3). Ø_𝑠𝑛 (n = 1, 2, and 3) refers to the work function values depending on charging state of active material. (b–d) Topography, VEXT, and deflection images of the pristine SiO/graphite composite anode. The red dotted line in (d) serves as a visual cue for distinguishing SiO particles. [link]

Verification of the multilayer structure of the SEI via nanoindentation mode in AFM. Typical force–displacement curves of Li-metal anodes in the (a) additive-free, (b) LiPO2F2 + LiNO3, and (c) LiPO2F2 + LiNO3 + VC electrolytes after precycling. Schematics of the mechanical properties of SEI layers formed in the (d) additive-free, (e) LiPO2F2 + LiNO3, and (f) LiPO2F2 + LiNO3 + VC electrolytes. AFM 3D images recorded before the measurement of data used for the construction of force–indentation depth curves in the (g) additive-free, (h) LiPO2F2 + LiNO3 , and (i) LiPO2F2 + LiNO3 + VC electrolytes. The elastic moduli and thicknesses of SEI layers formed in the (j) additive-free, (k) LiPO2F2 + LiNO3 , and those of the polymeric outer SEI layer formed in (l) LiPO2F2 + LiNO3 + VC electrolytes. [link]

Identifying the composition of the electrode and correlation of ESM and LFM signals (a–c) Height, ESM amplitude, and friction force images, respectively. (d) Pearson’s correlation plot of friction force (X axis) and ESM amplitude (Y axis) and histogram of friction force. (e) Trends of average values of ESM amplitude as a function of friction force (orange) and friction force as a function of ESM amplitude (olive). The ranges of the X and Y axes are 99% of full data. [link]

Correlation of the ionic/electronic parameters’ images. Comparison between the ESM and C-AFM images of the same area (marked with a slashed red line), where a-i) and a-ii) are the simultaneously obtained topography and ESM images and b-i) and b-ii) are the simultaneously obtained topography and C-AFM images, respectively. [link]