Modifying Li<sup>+</sup> and anion diffusivities in polyacetal electrolytes: A pulsed-field-gradient NMR study of Ion self-diffusion

Halat, DM; Snyder, RL; Sundararaman, S; Choo, Y; Gao, KW; Hoffman, ZJ; Abel, BA; Grundy, LS; Galluzzo, MD; Gordon, MP; Celik, H; Urban, JJ; Prendergast, D; Coates, GW; Balsara, NP; Reimer, JA

Modifying Li<sup>+</sup> and anion diffusivities in polyacetal electrolytes: A pulsed-field-gradient NMR study of Ion self-diffusion

Halat, DM Snyder, RL Sundararaman, S Choo, Y

Gao, KW Hoffman, ZJ Abel, BA Grundy, LS Galluzzo, MD Gordon, MP Celik, H Urban, JJ Prendergast, D Coates, GW Balsara, NP Reimer, JA

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Publisher:: American Chemical Society
Publication Type:: Journal Article
Citation:: Chemistry of Materials, 2021, 33, (13), pp. 4915-4926
Issue Date:: 2021-07-13

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Field	Value	Language
dc.contributor.author	Halat, DM
dc.contributor.author	Snyder, RL
dc.contributor.author	Sundararaman, S
dc.contributor.author	Choo, Y https://orcid.org/0000-0003-2715-0618
dc.contributor.author	Gao, KW
dc.contributor.author	Hoffman, ZJ
dc.contributor.author	Abel, BA
dc.contributor.author	Grundy, LS
dc.contributor.author	Galluzzo, MD
dc.contributor.author	Gordon, MP
dc.contributor.author	Celik, H
dc.contributor.author	Urban, JJ
dc.contributor.author	Prendergast, D
dc.contributor.author	Coates, GW
dc.contributor.author	Balsara, NP
dc.contributor.author	Reimer, JA
dc.date.accessioned	2022-05-12T01:04:13Z
dc.date.available	2022-05-12T01:04:13Z
dc.date.issued	2021-07-13
dc.identifier.citation	Chemistry of Materials, 2021, 33, (13), pp. 4915-4926
dc.identifier.issn	0897-4756
dc.identifier.issn	1520-5002
dc.identifier.uri	http://hdl.handle.net/10453/157257
dc.description.abstract	Polyacetal electrolytes have been demonstrated as promising alternatives to liquid electrolytes and poly(ethylene oxide) (PEO) for rechargeable lithium-ion batteries; however, the relationship between polymer structure and ion motion is difficult to characterize. Here, we study structure-property trends in ion diffusion with respect to polymer composition for a systematic series of five polyacetals with varying ratios of ethylene oxide (EO) to methylene oxide (MO) units, denoted as P(xEO-yMO), and PEO. We first use 7Li and 19F pulsed-field-gradient NMR spectroscopy to measure cation and anion self-diffusion, respectively, in polymer/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt mixtures. At 90 °C, we observe modest changes in Li+ diffusivity across all polymer compositions, while anion (TFSI-) self-diffusion coefficients decrease significantly with increasing MO content. At a given reduced temperature (T - Tg), all polyacetal electrolytes exhibit faster Li+ self-diffusion than PEO. Intriguingly, P(EO-MO) and P(EO-2MO) also show slower TFSI- anion self-diffusion than PEO at a given reduced temperature. Molecular dynamics simulations reveal that shorter distances between acetal oxygen atoms (O-CH2-O) compared to ether oxygens (O-CH2-CH2-O) promote more diverse, often asymmetric, Li+ coordination environments. Raman spectra reveal that anion-rich ion clusters in P(EO-MO) and P(EO-2MO) lead to decreased anion diffusivity, which along with increased cation diffusivity, support the viability of polyacetals as high-performance polymer electrolytes.
dc.language	English
dc.publisher	American Chemical Society
dc.relation.ispartof	Chemistry of Materials
dc.relation.isbasedon	10.1021/acs.chemmater.1c00339
dc.rights	info:eu-repo/semantics/closedAccess
dc.subject	03 Chemical Sciences, 09 Engineering
dc.subject.classification	Materials
dc.title	Modifying Li<sup>+</sup> and anion diffusivities in polyacetal electrolytes: A pulsed-field-gradient NMR study of Ion self-diffusion
dc.type	Journal Article
utslib.citation.volume	33
utslib.for	03 Chemical Sciences
utslib.for	09 Engineering
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology
pubs.organisational-group	/University of Technology Sydney/Faculty of Engineering and Information Technology/School of Civil and Environmental Engineering
utslib.copyright.status	closed_access	*
pubs.consider-herdc	false
dc.date.updated	2022-05-12T01:04:10Z
pubs.issue	13
pubs.publication-status	Published
pubs.volume	33
utslib.citation.issue	13

Abstract:

Polyacetal electrolytes have been demonstrated as promising alternatives to liquid electrolytes and poly(ethylene oxide) (PEO) for rechargeable lithium-ion batteries; however, the relationship between polymer structure and ion motion is difficult to characterize. Here, we study structure-property trends in ion diffusion with respect to polymer composition for a systematic series of five polyacetals with varying ratios of ethylene oxide (EO) to methylene oxide (MO) units, denoted as P(xEO-yMO), and PEO. We first use 7Li and 19F pulsed-field-gradient NMR spectroscopy to measure cation and anion self-diffusion, respectively, in polymer/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt mixtures. At 90 °C, we observe modest changes in Li+ diffusivity across all polymer compositions, while anion (TFSI-) self-diffusion coefficients decrease significantly with increasing MO content. At a given reduced temperature (T - Tg), all polyacetal electrolytes exhibit faster Li+ self-diffusion than PEO. Intriguingly, P(EO-MO) and P(EO-2MO) also show slower TFSI- anion self-diffusion than PEO at a given reduced temperature. Molecular dynamics simulations reveal that shorter distances between acetal oxygen atoms (O-CH2-O) compared to ether oxygens (O-CH2-CH2-O) promote more diverse, often asymmetric, Li+ coordination environments. Raman spectra reveal that anion-rich ion clusters in P(EO-MO) and P(EO-2MO) lead to decreased anion diffusivity, which along with increased cation diffusivity, support the viability of polyacetals as high-performance polymer electrolytes.

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http://hdl.handle.net/10453/157257