Title
An experimental and theoretical correlation to account for the effect of LiPF<inf>6</inf> concentration on the ionic conductivity of poly(poly (ethylene glycol) methacrylate)
Date Issued
01 July 2016
Access level
metadata only access
Resource Type
journal article
Author(s)
Publisher(s)
Elsevier B.V.
Abstract
This study is intended to analyze Li+ ion conduction across amorphous poly(poly(ethylene glycol) methacrylate) (pPEGMA) electrolyte using high concentrations of lithium hexafluorophosphate (LiPF6). A monomer (PEGMA) comprised of eight units of ethylene glycol is thermally polymerized via free radicals. Physicochemical and mechanical properties of polymer electrolytes pPEGMA /LiPF6 are determined at different Li+/O atomic ratios (0.37, 0.42, 0.48 and 0.54) using FTIR, DSC, TGA, XRD, and EIS. These experimental characterizations are used to account for the dependence of the material conductivity on the LiPF6 concentration, and its enhancement at a determined ratio. pPEGMA polymer presents a glass transition temperature (Tg) of 224 K and a 10% weight loss decomposition temperature (Td10%) of 453 K. Excess of salt on polymer electrolyte forms different complex interactions including ion pairs, which are detected by XRD and FTIR analysis. Although the presence of these clusters is important (i.e. mechanically), it is not dominant to determine ionic conduction, since it increases monotonically with increasing salt concentration and temperature, showing values of 2.07 × 10- 5 and 1.07 × 10- 4 S cm- 1 at 298 and 323 K respectively (Li+/O = 0.54). This trend is opposite to that observed in typical polymer electrolytes such as PEO, and it is due to the amorphous morphology of pPEGMA which forms a weak coordination shell with Li+ ion (weak electrolyte), enhancing ionic transport. In the region of temperature exceeding, Tg (224 K), the energetic conditions promote the dynamics disorder of motion chains and lithium ion hopping over Coulombic interactions, enabling diffusion motion at long time scale. DFT calculations performed to evaluate the physics and energies of the interactions of LiPF6 and PEGMA monomer reveal that mostly interactions where partial coordination crowns (two or three ether oxygens) between the polymer (i.e. central region) and one Li+ ion (also interacting with PF6-) present thermodynamically favorable energies, and the most probable bonding involves three ether oxygens, as experimentally determined.
Start page
98
End page
107
Volume
290
Language
English
OCDE Knowledge area
Ingeniería química
Subjects
Scopus EID
2-s2.0-84964596740
Source
Solid State Ionics
ISSN of the container
01672738
DOI of the container
10.1016/j.ssi.2016.03.020
Sponsor(s)
Financial support is greatly appreciated from the Ministry of Science, Technology and Innovation through project PICCO11-22 . JVA is indebted to CONACYT (Grant Nos. 2010-155698 , 2012-183230 , 2013-205416 and 2014-237343 ) for economic support to carry out this research. Authors also thank the supercomputing facilities offered by LANCAD (Laboratorio Nacional de Computo de Alto Desempeño) at UAM-I.
Sources of information:
Directorio de Producción Científica
Scopus