Miscible Polyether/Poly(ether-acetal) Electrolyte Blends.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Modern lithium-ion batteries utilize solvent mixtures, inspiring exploration of polymer blend electrolytes.
• Polymer electrolytes offer potential advantages over liquid electrolytes in battery applications.
• Understanding polymer miscibility and salt interactions is crucial for developing effective polymer electrolytes.

Purpose of the Study:

• To investigate the miscibility and thermodynamic interactions of poly(ethylene oxide) (PEO)/poly(1,3,6-trioxocane) (P(2EO-MO)) blends with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).
• To characterize the electrochemical properties of these polymer blend electrolytes.
• To explore the potential of polymer blends for creating novel and improved polymer electrolytes.

Main Methods:

• Small-angle neutron scattering (SANS) to determine polymer miscibility and thermodynamic interactions.
• Electrochemical characterization using symmetric cells to evaluate ionic conductivity and performance.
• Analysis of Flory-Huggins interaction parameters (χ and χeff) to quantify polymer-polymer and polymer-salt interactions.

Main Results:

• PEO/P(2EO-MO) blends are homogeneous with attractive interactions (negative χ) in the absence of salt.
• Addition of small salt amounts induces macrophase separation (positive χeff), while higher concentrations surprisingly lead to miscible blends (negative χeff).
• Electrochemical properties of the blends are comparable to PEO/LiTFSI electrolytes, indicating P(2EO-MO) behaves similarly to PEO in the presence of salt.

Conclusions:

• Miscible polymer blend electrolytes can be achieved by carefully controlling polymer composition and salt concentration.
• The study reveals a critical salt concentration beyond which blends become miscible, enabling enhanced electrolyte properties.
• This work presents a new strategy for designing advanced polymer electrolytes by combining polymers or synthesizing new ones for blend applications.