Single Nanowire Electrode Electrochemistry of Silicon Anode by in Situ Atomic Force Microscopy: Solid Electrolyte Interphase Growth and Mechanical Properties

Abstract

Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young's modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young's modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.

Investigation of the Electron Transfer at Si Electrodes: Impact and Removal of the Native SiO2Layer

“…It was shown before that the surface layer of the Si electrode can be damaged and removed by an AFM probe. This was either intended 17,[42][43][44] or occurred accidentally due to the interaction of AFM probes with the sample using the contact mode.…”

“…8,9 Especially atomic force microscopy (AFM) has been used to characterize in situ and ex situ the SEI at amorphous Si (a-Si) thin films, [10][11][12][13][14] Si-based thin films, 11,15 a-Si nanopillars 16 and Si nanowires. 17,18 AFM provides information about the morphology evolution and physical properties of the SEI. The present study aims at characterizing the functional properties of Si electrodes in situ by the feedback mode of scanning electrochemical microscopy (SECM), which probes the local electron transfer rate constants at the surface of interest in the electrolyte environment.…”

Wet Nanoindentation of the Solid Electrolyte Interphase on Thin Film Si Electrodes

“…[7][8][9][10][11] The Poisson ratio of the anisotropic SEI is likely to be between 0.5 and 0.25, which is typical for polymeric composite materials. 24 We used the modification of Bilodeau 25 for the four-sided pyramid indenter for the numerical fitting of the force-indentation data obtained with AFM tip…”

“…This interpretation is consistent with earlier statements claiming that SEI grows mainly during the initial formation cathodic scan. 10,11,35 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 insets. 38 The related distribution of the apparent Young's modulus of the SEI as determined by 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Nanoindentation measurements were conducted with sharp AFM tips and spherical colloidal probes (CPs) on the SEI formed after the first...…”

“…[4][5][6] In addition, AFM-based methods can provide information about the mechanical properties of the SEI, such as the Young´s modulus. [7][8][9][10][11] However, probing thin films by indentation is challenging and special attention must be paid to address several important aspects, e.g. morphology or surface properties such as roughness and adhesiveness to minimize errors and obtain reliable results.…”