ε-Caprolactone-based solid polymer electrolytes for lithium-ion batteries: synthesis, electrochemical...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid polymer electrolytes (SPEs) are crucial for developing safer and more efficient battery technologies.
• Incorporating polystyrene blocks into poly(ε-caprolactone) aims to enhance electrochemical and mechanical properties.

Purpose of the Study:

• To synthesize and characterize novel polymer electrolytes based on ε-caprolactone.
• To evaluate the performance of these SPEs in lithium-ion battery half-cells.
• To optimize the composition of SPEs for improved cycling stability and capacity.

Main Methods:

• Synthesis of poly(ε-caprolactone), polystyrene-poly(ε-caprolactone), and polystyrene-poly(ε-caprolactone-r-trimethylene carbonate) (SCT) polymers.
• Preparation of SPEs by blending polymers with varying concentrations of lithium bis(trifluoromethane)sulfonimide (LiTFSI).
• Fabrication and electrochemical testing of Li|SPE|LiFePO4 battery half-cells, including cycling performance analysis and dynamic mechanical analysis (DMA).

Main Results:

• The SCT polymer blended with 17 wt% LiTFSI demonstrated superior performance as a solid polymer electrolyte.
• A Li|SPE|LiFePO4 cell using this optimized SPE achieved a discharge capacity of ~140 mA h g⁻¹ at C/5 for 100 cycles at 40 °C.
• Dynamic mechanical analysis indicated a storage modulus E' of approximately 5 MPa for the best-performing electrolyte.

Conclusions:

• Polystyrene-grafted polymers offer improved properties for solid polymer electrolytes.
• The optimized SCT/LiTFSI electrolyte shows significant potential for stable lithium-ion battery applications.
• Further research into polymer-based electrolytes can lead to advanced energy storage solutions.