Temperature-Shift-Induced Mechanical Property Evolution of Lithium-Ion Battery Separator Using Cyclic Nanoindentation

Area of Science:

• Materials Science
• Electrochemistry
• Mechanical Engineering

Background:

• Mechanical properties of battery separators are critical for lithium-ion battery performance.
• Evaluating these properties is challenging due to the flexible nature of separator films.
• Temperature fluctuations significantly influence separator behavior and battery safety.

Purpose of the Study:

• To investigate the temperature-dependent evolution of mechanical properties in lithium-ion battery separators.
• To quantify the impact of temperature shifts on elastic modulus, hardness, and hysteresis.
• To provide data for optimizing separator design and enhancing battery safety.

Main Methods:

• Experimental determination of temperature distribution during subzero discharge.
• Multicycle depth-sensitive nanoindentation on separators subjected to various temperature shifts.
• Analysis of loading-unloading nanoindentation responses to extract mechanical properties.
• Characterization using X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS).

Main Results:

• Experimentally verified temperature-dependent weakening of elastic modulus and hardness in separators.
• Quantified variation trends of elastic modulus, hardness, and hysteresis with temperature changes.
• Observed attenuation in hardness changes after heating/cooling followed by a thermostatic process.
• Identified size effects in nanoindentation hardness related to indentation depth.

Conclusions:

• Temperature shifts induce significant changes in separator mechanical properties, particularly elastic modulus and hardness.
• The study provides a framework for understanding temperature-induced mechanical property evolution in battery separators.
• Findings support optimized separator design and improved safety for lithium-ion batteries.