Test method for puncture resistance performance of lithium battery separator
separator, as the separator of positive and negative electrodes, is an essential part of lithium battery. The performance of the separator material used directly affects the safety and cost of the battery.
With the advancement of science and technology and the enhancement of environmental protection awareness, lithium batteries with excellent performance such as high working voltage, high energy density, long cycle life, low self-discharge rate, low pollution, and no memory effect are used in Mobile phones, notebook computers, tablet computers, digital cameras, electric vehicles, aerospace, navigation, satellites, small medical, military communications equipment and other products and fields are widely used.
The puncture resistance is an important mechanical index to evaluate the performance of the diaphragm material, and it can effectively reflect whether the diaphragm is prone to short circuit during the assembly process. The mixed active material, carbon black, plasticizer and PVDF are uniformly coated on the metal foil and dried in high-temperature vacuum. The surface of the lithium battery electrode is composed of fine particles of the active material and carbon black mixture. Because of the unevenness, the separator material sandwiched between the positive and negative electrodes needs to withstand a lot of pressure. Therefore, the separator material should have strong puncture resistance to prevent the positive and negative electrodes of the lithium battery pack from contacting and short-circuiting.
1. diaphragm puncture test basis
According to the puncture strength in the standard GB/T 10004-2008 'Plastic composite film for packaging, bag dry composite, extrusion composite' Related regulations.
2. Sample preparation for diaphragm puncture test
Take the polyolefin battery diaphragm as the test sample to test its anti-puncture performance, select the same batch of products to make 5 to 10 samples .
3. diaphragm puncture test equipment
Use intelligent electronic tensile testing machine to test the puncture force of battery diaphragm samples, paying attention to the equivalence of condition settings.
4. Principle of puncture test of lithium battery separator
The level of puncture resistance is expressed by the maximum force generated during puncturing the sample to be tested-puncture force. During the test, the specimen is clamped in a fixed fixture, and the movable fixture equipped with a puncture needle moves to the specimen at a set speed until the specimen is pierced. The movable fixture contains a force sensor, which can monitor the puncture in real time. The force value changes during the process, thereby obtaining the puncture force of the sample. In addition, the fixture is also equipped with a displacement sensor to monitor the deformation of the sample.
5. diaphragm piercing equipment parameters
General equipment is equipped with 500N and 50N force sensors to choose from; according to relevant standards, the equipment provides 50mm/ Seven test speeds: min, 100mm/min, 150mm/min, 200 mm/min, 250 mm/min, 300 mm/min, 500 mm/min, which can be set freely according to the requirements of the test standard; the 1000mm long stroke can meet the requirements Testing of materials with large deformation rates; intelligent configuration such as limit protection, overload protection, automatic return and power-down memory, to ensure the safety of users' operations.
6. diaphragm piercing test process
(1) Use a sampler to cut 5 samples from the surface of the battery diaphragm sample to be tested.
(2) Set the test speed, sample name, test times and other parameter information on the equipment control software, clamp the sample in the special fixture, and install the puncture needle. Click the 'Test' option, the test starts, the puncture needle moves to puncture the sample at the set test speed, the device displays the force value change in real time, and reports the puncture force value at the end of the test.
7. Record the test results
The test values u200bu200bof the puncture force of the 5 specimens are 5.34 and 5.61N5.57N5.49N5.32N respectively. The battery diaphragm samples tested
The puncture resistance of the product is 5.47N, the average of the test results of 5 specimens. Compare the result with GB/T 10004-2008 'Plastic composite film for packaging, bag dry composite, extrusion composite'. Within the qualified range, the battery separator is qualified.
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