Chinese Team Develops New High-Temperature-Resistant Battery Separator to Improve Lithium Battery Safety

Recently, concerns over the safety of lithium batteries—particularly the potential for sudden high temperatures during charging—have garnered significant attention. A research team from the Institute of Modern Physics at the Chinese Academy of Sciences, in collaboration with Lanzhou University and the Guangdong Provincial Laboratory of Advanced Energy Science and Technology, has developed an innovative process for creating high-temperature-resistant polyimide separators. This work, achieved using ion track technology and supported by the Lanzhou Heavy Ion Accelerator, aims to improve the safety of lithium-ion batteries.

The findings, representing a significant advance in battery material science, were published in the journal ACS Nano. Both the first author and corresponding author are from the Institute of Modern Physics.

The team explained that separators are vital components of lithium-ion batteries, as they isolate the electrodes while allowing lithium-ion transport. While commercial lithium batteries now reach energy densities of up to 300 Wh/kg, safety issues become more critical with higher energy densities. Traditional polyolefin separators, which lack thermal stability and feature inconsistent pore structures, are prone to shrinkage at high temperatures, potentially causing short circuits.

Polyimide is regarded as an ideal material for safer separators due to its excellent thermal stability, high mechanical strength, and chemical durability. Developing polyimide separators with consistent pore structures is essential for improving battery safety.

Using ion track technology, the team created a new manufacturing process for polyimide separators. These separators demonstrate significant advantages over polyolefin ones:

• High mechanical strength: up to 150.6 MPa.
• Excellent thermal stability: no shrinkage at 450°C.
• Narrow pore size distribution: standard deviation <6%.
• Vertically aligned pore channels: tortuosity = 1.

Under testing conditions of 3 mA/cm², lithium symmetric cells using these separators cycled stably for 1,200 hours and showed uniform lithium deposition, effectively suppressing dendrite growth. Furthermore, lithium iron phosphate pouch cells equipped with the separators achieved 1,000 cycles at room temperature with a 73.25% capacity retention rate and operated reliably at 150°C.

This research offers a new approach to developing reliable, high-performance lithium-ion battery separators and manufacturing processes, providing a promising pathway to enhance battery safety.