Multifunctional Solvent Molecule Realizing High-Performance Elastic Polymer Electrolytes for Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Solid-state polyurethane electrolytes offer elasticity for improved interfacial ion transport in lithium metal batteries.
• Pure polyurethane electrolytes exhibit limited Li+ conductivity, hindering their practical application.

Purpose of the Study:

• To enhance the Li+ conductivity and interfacial stability of thermoplastic polyurethane (TPU) electrolytes.
• To develop a composite electrolyte (TPU-TFDMA) using trifluoro-N,N-dimethylacetamide (TFDMA) for solid-state lithium metal batteries.

Main Methods:

• Modification of TPU electrolyte with trifluoro-N,N-dimethylacetamide (TFDMA).
• Experimental characterizations (e.g., ionic conductivity measurements, transference number determination).
• Theoretical simulations to understand interfacial interactions and ion transport mechanisms.

Main Results:

• The TPU-TFDMA composite electrolyte achieved an ionic conductivity of 1.53 × 10-3 S cm-1 and a Li+ transference number of 0.50.
• TFDMA enhanced mechanical properties, interfacial stability, and inhibited lithium dendrite growth through hydrogen-bonding interactions.
• Improved Li+ dissociation, reduced Li+ desolvation energy, and TFSI- immobilization were observed.

Conclusions:

• The developed TPU-TFDMA electrolyte demonstrates excellent Li+ transport performance and mechanical properties.
• Stable cycling of Li symmetric cells (>2500 h) and LiFePO4 full cells (130 mAh g-1 at 0.5 C after 320 cycles) were achieved.
• TFDMA is a promising additive for high-performance solid-state lithium metal batteries.