Page 8 - Guide to Lithium-ion Battery Solutions

Material Testing

Strength measurement and strain characteristic evaluation of a separator at high temperature Purpose

Tensile strength measurement of a separator
(Condition : 25 °C, 60 °C, and 90 °C)
AUTOGRAPH Precision Universal Tester

AGX-V Samples

• Various mechanical strength measurements of Lithium-ion Battery Two types of separators, prepared in
materials dumbbell shapes along both the length and
• Evaluation of the piercing strength of a separator packed with high density width direction
• Visualization of strain distribution by DIC analysis

Data
The separator is installed so that it is in contact with the positive and negative electrodes. Since the temperature rises
during charging, it is necessary to maintain mechanical strength even as the temperature changes. The following shows
an example of measuring how the strength of a separator in the tensile test and the piercing test changes with respect to Mechanical properties of separator (1) and (2) in the short side and long side directions
temperature changes, and an example of evaluating the strain characteristics after piercing damage. Long side: Machine Direction
Short side: Transverse Direction

25 °C 60 °C 90 °C
Tensile strength Rupture strain Tensile strength Rupture strain Tensile strength Rupture strain
Sample
(MPa) (%) (MPa) (%) (MPa) (%)
Purpose Samples
(1)Short side 36.9 471.4 35.4 898.8 19.3 1044.0
Tensile test of separator Three types of separators (1)Long side 175.6 26.8 162.5 57.0 129.9 76.7
(2)Short side 78.2 138.5 68.8 347.6 33.8 427.9
Specimen Lithium Battery Separator
(2)Long side 129.5 34.1 118.3 105.3 58.7 367.2
Data Specimen Name A B C
Thickness Separator (1) Separator (2)
Tensile Test Results (µm) 20 20 10
Specimen Lithium Battery Separator

Specimen Name A B C
Elastic Modulus 902 1856 1376
(MPa)
Tensile Strength 165 118 101
(MPa) Stress-strain graph
Break Point Strain 27.6 31.7 29.1
(%)
Result

Separator (1) is produced by near uniaxial stretching in the machine direction (MD), and separator (2) is
Stress-strain graph
Result produced by biaxial stretching at a low stretching ratio. Despite the increase in elongation properties
at 60°C, excellent mechanical strength is maintained.
From the measurement results, it can be seen that the separator with high tensile strength is A.

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