Presentation Information
[8a-N206-5]Molecular-Scale Visualization of Solvation Structures of LiTFSI-PC Electrolyte on a Heterogeneously Charged Surface by FM-AFM and MD Simulations
〇(D)Yilin Wang1, Kei Kobayashi1 (1.Kyoto Univ..)
Keywords:
frequency modulation atomic force microscopy,solid liquid interface,molecular dynamics simulations
The solvation structures formed by ions and solvent molecules at solid/liquid interfaces critically influence the energy storage performance of lithium-ion batteries (LIBs). In a previous study, we studied the solvation structures of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in propylene carbonate (PC) on muscovite mica[1], which is negatively charged. In this study, we performed the solvation structure measurement of LiTFSI in PC on a heterogeneously charged clinochlore surface using FM-AFM to elucidate the relationship between solvation structures and surface charge density.
Cleaving clinochlore yields a (001) surface composed of alternating negatively charged talc-like and positively charged brucite-like layers [2]. And the higher layer is the brucite-like layer with a thickness of approximately 0.5 nm. Two-dimensional frequency shift map (Fig. 1a) in 100 mM LiTFSI-PC electrolyte distinguished solvation structures on each domain. On the talc-like layer we found a few dark stripes with about 0.4 nm spacing, indicating layered assemblies of PC molecules. In contrast, on the brucite-like layer, we found two dark stripes with a spacing of about 1 nm, suggesting TFSI- anions attracted to the surface formed solvated complexes such as (PC)3TFSI- and (PC)4TFSI-.
We also conducted molecular dynamics (MD) simulations of the clinochlore/electrolyte interface. Fig. 1b shows preliminary density profiles of each ionic/molecular species at the interface, showing the Li+ and TFSI- adsorbed on the talc-like and brucite-like layer, respectively.
Reference
[1] Y. Yamagishi, et al. Nano Lett. 22, 9907 (2022).
[2] K. Umeda, et al. Nat. Commun. 8, 594 (2018).
Cleaving clinochlore yields a (001) surface composed of alternating negatively charged talc-like and positively charged brucite-like layers [2]. And the higher layer is the brucite-like layer with a thickness of approximately 0.5 nm. Two-dimensional frequency shift map (Fig. 1a) in 100 mM LiTFSI-PC electrolyte distinguished solvation structures on each domain. On the talc-like layer we found a few dark stripes with about 0.4 nm spacing, indicating layered assemblies of PC molecules. In contrast, on the brucite-like layer, we found two dark stripes with a spacing of about 1 nm, suggesting TFSI- anions attracted to the surface formed solvated complexes such as (PC)3TFSI- and (PC)4TFSI-.
We also conducted molecular dynamics (MD) simulations of the clinochlore/electrolyte interface. Fig. 1b shows preliminary density profiles of each ionic/molecular species at the interface, showing the Li+ and TFSI- adsorbed on the talc-like and brucite-like layer, respectively.
Reference
[1] Y. Yamagishi, et al. Nano Lett. 22, 9907 (2022).
[2] K. Umeda, et al. Nat. Commun. 8, 594 (2018).