The seminar will take place at the Sala d'Actes MATGAS but it will also be possible to be followed online:
Effect of Molecular Weight and star shaped architecture on the Thermal properties and conductivity of PEO based electrolytes
by Dimitrios Chatzogiannakis, University of Crete
Tuesday, 21 September 2021, at 12 pm
ICMAB-Sala d'Actes MATGAS and Online by Zoom. Register here to attend.
Since the discovery of the interaction of polyethylene-oxide’s ether oxygens with lithium ions by Fenton and Parker in 19731, PEO has attracted considerable research effort for its potential use as an electrolyte in Lithium ion batteries as it can both dissociate Lithium salts as well as conduct the resulting ions. The interest on it, and other similar polymer, grew exponentially when research into solid state batteries became popular, promising multiple advantages over the traditional ones, revolving mostly around safety and longevity and last but not least, enabling the use of metallic Lithium as an anode, significantly boosting their performance. The goal for the utilization of such molecules comes, amongst others, from a theoretical paper from Newman and Monroe in 2005 stating that the growth of Lithium dendrites, possibly the biggest challenge of Lithium metal batteries, can be mechanically suppressed by an electrolyte with a sheer modulus in the order of GPa2. Since then multiple efforts have been made to reinforce polymers to such moduli while maintaining their conductivity as well as developing other polymers to serve such purposes3. Another problem of PEO is its high tendency to crystallize, fact that inhibits Lithium conduction which predominantly occurs through the amorphous regions of the polymer electrolyte4. This makes the reduction of such crystallinity also of paramount importance.
In this work we studied various PEO-based macromolecules differing in size (molecular weight) and shape/architecture (linear/star) in terms of Lithium conductivity and thermal characteristics when blended with Lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI). In parallel we performed Raman measurements to quantify the degree of salt dissociation as well as well as some rheology to reveal the expected mechanical superiority of the star shaped molecules.
Our results amongst others shed light on the temperature/conductivity interplay of PEO electrolytes as well as the conductivity/viscosity interplay when architecture is altered. Notably utilizing star-like shapes we managed to increase viscosity by 6 orders of magnitude while reducing conductivity less than a factor of 10.
- Fenton, D. E., Parker, J. M. & Wright, P. V. Complexes of alkali metal ions with poly(ethylene oxide). Polymer 14, 589 (1973).
- Monroe, C. & Newman, J. The Impact of Elastic Deformation on Deposition Kinetics at Lithium/Polymer Interfaces. J. Electrochem. Soc. 152, A396 (2005).
- Glynos, E., Pantazidis, C. & Sakellariou, G. Designing All-Polymer Nanostructured Solid Electrolytes: Advances and Prospects. ACS Omega (2020). doi:10.1021/acsomega.9b04098
- Berthier, C. et al. Microscopic investigation of ionic conductivity in alkali metal salts-poly(ethylene oxide) adducts. Solid State Ionics 11, 91–95 (1983).
Hosted by M. Rosa Palacín, Solid State Chemistry group, ICMAB-CSIC
Register here to attend by Zoom.