Ion transport in polycarbonate based solid polymer electrolytes: experimental and computational investigations

Abstract

Among the alternative host materials for solid polymer electrolytes (SPEs), polycarbonates have recently shown promising functionality in all-solid-state lithium batteries from ambient to elevated temperatures. While the computational and experimental investigations of ion conduction in conventional polyethers have been extensive, the ion transport in polycarbonates has been much less studied. The present work investigates the ionic transport behavior in SPEs based on poly(trimethylene carbonate) (PTMC) and its co-polymer with ε-caprolactone (CL) via both experimental and computational approaches. FTIR spectra indicated a preferential local coordination between Li(+) and ester carbonyl oxygen atoms in the P(TMC20CL80) co-polymer SPE. Diffusion NMR revealed that the co-polymer SPE also displays higher ion mobilities than PTMC. For both systems, locally oriented polymer domains, a few hundred nanometers in size and with limited connections between them, were inferred from the NMR spin relaxation and diffusion data. Potentiostatic polarization experiments revealed notably higher cationic transference numbers in the polycarbonate based SPEs as compared to conventional polyether based SPEs. In addition, MD simulations provided atomic-scale insight into the structure-dynamics properties, including confirmation of a preferential Li(+)-carbonyl oxygen atom coordination, with a preference in coordination to the ester based monomers. A coupling of the Li-ion dynamics to the polymer chain dynamics was indicated by both simulations and experiments.

Understanding the molecular mechanism of pulse current charging for stable lithium-metal batteries

“…3 (C and D), the coordination number of oxygen atoms around Li + is approximately six, among which four are from PC and one or two are from TFSI − . Similar results have been previously reported with Raman intensity experiments ( 38 ) and classical MD simulations ( 39 – 41 ) that, when a static electric field is applied, the coordination number of TFSI − around Li + gets smaller. In addition, Fig.…”

Ion-Conductive Properties of a Polymer Electrolyte Based on Ethylene Carbonate/Ethylene Oxide Random Copolymer

“…These results from FT‐IR and NMR imply that the CO groups in the main chain interact preferentially with Li + , rather than the ether COC in P(EC/EO). A similar study on the copolymer electrolyte, based on trimethylene carbonate and ε‐caprolactone, indicates that Li + coordinates preferentially with ester carbonyl oxygen atoms rather than with carbonate carbonyl oxygen atoms . This is because carbonate groups have no stronger complexation or chelating effects related to more regular spacing, as they are distributed randomly in the copolymer backbone.…”

High Performance Solid Polymer Electrolytes for Rechargeable Batteries: A Self‐Catalyzed Strategy toward Facile Synthesis

“…The polymer host should have a low glass transition temperature facilitating chain segments mobility and a high dielectric constant dissociating enough lithium salts. In addition to the classic poly(ethylene oxide) PEO host polymer,4 polysiloxane,5, 6 and polycarbonate7, 8 have recently been demonstrated to serve as alterative host polymers with regard to their higher electrochemical stability. As to another component lithium salts, it includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO 4 ), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalate)borate (LiDFOB), lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), and so on 9.…”