An Ambient Temperature Electrolyte with Superior Lithium Ion Conductivity based on a Self-Assembled Block Copolymer

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Developing high-performance electrolytes is critical for advancing lithium ion and lithium metal batteries.
• Block copolymers offer a promising platform for creating stable and conductive solid-state electrolytes.

Purpose of the Study:

• To investigate block copolymer electrolytes with high lithium salt content for improved battery performance.
• To explore the relationship between microstructure, ionic conductivity, and mechanical properties in these polymer electrolytes.

Main Methods:

• Macromolecular co-assembly of poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) with lithium bis(trifluoromethane)sulfonimide.
• Utilizing an ultra-short poly(ethylene oxide) block (2100 g mol⁻¹) to form 2D continuous lamellar microstructures.
• Characterizing ionic conductivity, lithium ion transference number, and mechanical stability via thermal annealing and electrochemical measurements.

Main Results:

• Achieved high ionic conductivity of 1.4 mS cm⁻¹ at 20°C with low activation energy.
• Demonstrated a superior lithium ion transference number of 0.7.
• Obtained enhanced mechanical stability with a storage modulus up to 10⁷ Pa.
• Confirmed fast Li⁺ transport in block copolymers (BCP) decoupled from polymer relaxation at high Li:O ratios (>1).

Conclusions:

• The developed block copolymer electrolyte with an ultra-short PEO block provides a viable concept for fast Li⁺ transport.
• This approach enhances both ionic conductivity and mechanical stability, addressing key challenges in solid-state lithium battery electrolytes.
• The findings pave the way for designing advanced polymer electrolytes for high-performance lithium batteries.