Temperature Dependence of Puncture Strength of Separators

Importance of the Topic

The mechanical strength of battery separators is a critical factor in preventing internal short circuits and thermal runaway in lithium-ion cells. Evaluating puncture resistance at various temperatures provides insight into separator durability under real-world operating conditions, supporting safer battery design and performance optimization.

Objectives and Study Overview

This study investigates how environmental temperature affects the puncture strength of three commercial separator materials. By comparing performance at room temperature, 60 °C, and 90 °C, the work aims to quantify strength reduction and identify materials with superior thermal stability.

Methodology and Instrumentation

Puncture tests were conducted using a precision universal testing machine equipped with a boil-in-bag piercing jig mounted inside a thermostatic chamber. A constant crosshead speed of 50 mm/min and a preload of 0.1 N ensured reproducible conditions. Each material was tested three times at each temperature. The cage-type jig design applies load in tension to prevent buckling at elevated temperatures.

Instrumentation Used

• AGS-V Precision Universal Testing Machine (500 N capacity)
• Boil-in-bag piercing test jig with cage-type mechanism
• TCE-N300A Compact Thermostatic Chamber
• TRAPEZIUM X-V data acquisition software

Main Results and Discussion

All three separator materials exhibited decreasing puncture strength with rising temperature. At 60 °C, strength decreased by 25–30 % for two samples but remained near 75 % of room-temperature values for one manufacturer. At 90 °C, all materials lost almost half of their initial strength, indicating significant thermal softening and loss of mechanical integrity.

Benefits and Practical Applications

The temperature-dependent data guide material selection for applications involving thermal stress, such as electric vehicles and high-power devices. The simple nut-based jig enables fast sample exchange and high-precision measurements under controlled conditions.

Future Trends and Opportunities

Advances in separator polymers and composite structures could improve high-temperature puncture resistance. Integration of in situ monitoring techniques and multiaxial testing may further refine safety assessments. Emerging solid-state battery separators will also require tailored mechanical testing protocols.

Conclusion

This work demonstrates a reliable method for assessing separator puncture strength across a range of temperatures. The findings emphasize the need to consider thermal effects in safety evaluations and highlight materials with enhanced resistance at elevated temperatures.