Lithium Salt Induces Phase Separation in Polymer Blend Electrolyte

June 15, 2023
Lithium Salt Induces Phase Separation in Polymer Blend Electrolyte
(left) Schematic showing phase transition of PEO/PMMA blend when Li salt is added. (right) Miscible (blue) and separated (red) regions of the PEO/PMMA phase diagram measured by SANS (Exp) compared to theory prediction (The); ϕ1 = volume fraction of PEO in binary PEO/PMMA blend; r = mol ratio of Li ions relative to ether oxygen atoms in PEO.

Scientific Achievement

This work demonstrates that adding lithium bis(trifluoro-methanesulfonyl)imide (LiTFSI) induces phase separation in the normally fully miscible blend of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA).

Significance and Impact

The results will help in the design of novel polymer electrolytes with the desired immiscibility to yield both high mechanical stability and high Li-ion conductivity.

Research Details

  • Small angle neutron scattering (SANS) determined the thermodynamic properties of PEO/PMMA/LiTFSI blend electrolytes.
  • The de Gennes’ RPA framework was used to determine interaction parameters from  x SANS scattering profiles of miscible blends.
  • The results reveal an unusual relationship between miscibility, salt concentration, and blend composition.

“Thermodynamics and Phase Behavior of Poly(ethylene oxide)/ Poly(methyl methacrylate)/Salt Blend Electrolytes Studied by SmallAngle Neutron Scattering”
Neel J. Shah, Lilin He, Kevin W. Gao1, and Nitash P. Balsara1,
Macromolecules 56, 2889 -2898 (2023). DOI:10.1021/acs.macromol.2c02533