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. 2024 May 29;16(21):27202-27208.
doi: 10.1021/acsami.3c17597. Epub 2024 May 15.

Thickness Variation of Conductive Polymer Coatings on Si Anodes for the Improved Cycling Stability in Full Pouch Cells

Philipp Stehle  1   2 , Frauke Langer  2   3 , Dragoljub Vrankovic  2 , Montaha Anjass  1   4
Affiliations

Thickness Variation of Conductive Polymer Coatings on Si Anodes for the Improved Cycling Stability in Full Pouch Cells

Philipp Stehle et al. ACS Appl Mater Interfaces. .

Abstract

Si-dominant anodes for Li-ion batteries provide very high gravimetric and volumetric capacity but suffer from low cycling stability due to an unstable solid electrolyte interphase (SEI). In this work, we improved the cycling performance of Si/NCM pouch cells by coating the Si anodes with the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) prior to cell assembly via an electropolymerization process. The thicknesses of the PEDOT coatings could be adjusted by a facile process parameter variation. Glow-discharge optical emission spectroscopy was used to determine the coating thicknesses on the electrodes prior to the cell assembly. During electrochemical testing, improvements were observed closely linked to the PEDOT coating thickness. Specifically, thinner PEDOT coatings exhibited a higher capacity retention and lower internal resistance in the corresponding pouch cells. For the thinnest coatings, the cell lifetime was 18% higher compared to that of uncoated Si anodes. Postmortem analyses via X-ray photoelectron spectroscopy and cross-sectional scanning electron microscopy revealed a better-maintained microstructure and a chemically different SEI for the PEDOT-coated anodes.

Keywords: PEDOT; conducting polymers; lithium-ion battery; silicon anodes; solid electrolyte interphase.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Exemplary complete glow-discharge optical emission spectrum of a PEDOT-coated Si anode (a), photos of a PEDOT-coated compared to a pristine anode from front and back (b), and excerpt from glow-discharge optical emission spectra measured at the four different positions of a PEDOT-coated anode (c). The data in this picture originate from anodes coated with 1 mA/cm2 for 2 min. Coatings obtained from these conditions are referred to as “thick” in the following figures.
Figure 2
Figure 2
Glow-discharge optical emission spectra of Si anodes coated with different thicknesses of PEDOT (a) and net masses of the corresponding PEDOT coatings (b).
Figure 3
Figure 3
Discharge capacities obtained during the cycling protocol (a), corresponding capacity retentions after 100 cycles related to 1C (b), and internal resistances measured 5 s after the discharge pulses (c).
Figure 4
Figure 4
Cross-sectional SEM images of postmortem Si anodes after 100 cycles without PEDOT coating (a) and with a PEDOT coating obtained after applying 0.1 mA/cm2 for 0.5 min (b).
Figure 5
Figure 5
F1 s (a) and C1 s (b) X-ray photoelectron spectra of postmortem Si anodes after 100 cycles without PEDOT coating (top) and with a PEDOT coating (bottom) obtained after applying 0.1 mA/cm2 for 0.5 min.
See this image and copyright information in PMC

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