Robust, High-Temperature-Resistant Polyimide Separators with Vertically Aligned Uniform Nanochannels for...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Conventional polyolefin separators in lithium-ion batteries (LIBs) exhibit poor thermal stability and non-uniform pore structures.
• These limitations hinder effective prevention of thermal shrinkage and lithium dendrite growth, compromising battery safety and performance.

Purpose of the Study:

• To develop a robust, high-temperature-resistant polyimide (PI) separator with vertically aligned nanochannels for enhanced LIBs.
• To improve ionic conductivity, lithium-ion transport, and overall battery safety and cycle life.

Main Methods:

• Fabrication of polyimide track-etched membranes (PITEMs) using ion track-etching technology.
• Characterization of PITEMs for ionic conductivity, Li+ transfer number, and thermal stability.
• Electrochemical testing of PITEMs in various LIB configurations (Li/Li, Li/LiFePO4, graphite/LiFePO4 pouch cells) at different temperatures.

Main Results:

• PITEMs exhibit enhanced ionic conductivity (0.57 mS cm-1) and a high Li+ transfer number (0.61).
• Significant improvements in cycle life for Li/Li cells (1200 h) and capacity retention in Li/LiFePO4 cells (83.88% after 300 cycles at room temp, 85.92% after 200 cycles at 80 °C).
• Pouch cells with PITEMs show excellent cycling stability (73.25% capacity after 1000 cycles at room temp) and can operate at 150 °C.

Conclusions:

• The developed PI separator effectively addresses limitations of traditional separators, offering superior thermal stability and uniform ion distribution.
• PITEMs demonstrate significant potential for enhancing the safety and electrochemical performance of LIBs.
• The fabrication method is suitable for mass production via roll-to-roll techniques, paving the way for advanced battery manufacturing.