Techniques π are used to investigate the factors affecting the peel strength of the pole sheet from various angles
The stripping strength of the pole sheet refers to the size of the bonding property between the active material and the foil in the positive and negative lithium battery electrodes, which can usually be expressed in N or N/m. The test method is to fix the width and length of the pole piece, use a certain specification of tape, and use a tension test machine to test the stripping strength of the pole piece. The test methods are transverse stretching and longitudinal stretching, the test results of the two methods are slightly different, and it is best to use the same equipment when used to guide daily production.
The stripping strength of the lithium-ion battery electrode has a great impact on the performance of the battery. When the stripping strength is low, the active substance will be stripped from the surface of the foil after multiple cycles of charging and discharging, resulting in the attenuation of the battery capacity and the shortening of the cycle life. Low stripping strength is one of the main failure modes of lithium batteries. Only by knowing the factors that affect the stripping strength of the pole sheet can we overcome this anomaly with a target. The following is an analysis from multiple angles:
From the point of view of cell design, it is mainly the ratio and selection of binder in battery raw materials. From the point of view of capacity design, the less the amount of binder selected, the better, the cheaper the better, but the less, the cheaper, on behalf of the quality stability of the binder, the lower the peel strength of the pole sheet. A balance needs to be struck between battery performance and material selection. At present, the binder used for the positive electrode is mainly PVDF, and the binder used for the negative electrode is mainly SBR and CMC, for example:
It can be seen from the figure that with the increase of the amount of SBR, the stripping strength of the pole sheet increases gradually before and after rolling. With the increase of SBR content from 1.25% to 2.99%, the stripping strength of anode sheet increases from 11.07N /m to 97.33N/m, with an average increase of 779.22%. After rolling, the peel strength of the pole sheet increased from 9.2N/m to 41.77N /m, with an average increase of 354.02%.
However, it should be noted that it is not the higher the SBR content, the better, the higher the SBR content will make the pole plate more brittle fracture, but also affect the battery capacity and rate performance. In addition, the ratio of SBR to CMC in the negative electrode is equally important.
The stripping strength of the lithium-ion battery electrode has a great impact on the performance of the battery. When the stripping strength is low, the active substance will be stripped from the surface of the foil after multiple cycles of charging and discharging, resulting in the attenuation of the battery capacity and the shortening of the cycle life. Low stripping strength is one of the main failure modes of lithium batteries. Only by knowing the factors that affect the stripping strength of the pole sheet can we overcome this anomaly with a target. The following is an analysis from multiple angles:
From the point of view of cell design, it is mainly the ratio and selection of binder in battery raw materials. From the point of view of capacity design, the less the amount of binder selected, the better, the cheaper the better, but the less, the cheaper, on behalf of the quality stability of the binder, the lower the peel strength of the pole sheet. A balance needs to be struck between battery performance and material selection. At present, the binder used for the positive electrode is mainly PVDF, and the binder used for the negative electrode is mainly SBR and CMC, for example:
It can be seen from the figure that with the increase of the amount of SBR, the stripping strength of the pole sheet increases gradually before and after rolling. With the increase of SBR content from 1.25% to 2.99%, the stripping strength of anode sheet increases from 11.07N /m to 97.33N/m, with an average increase of 779.22%. After rolling, the peel strength of the pole sheet increased from 9.2N/m to 41.77N /m, with an average increase of 354.02%.
However, it should be noted that it is not the higher the SBR content, the better, the higher the SBR content will make the pole plate more brittle fracture, but also affect the battery capacity and rate performance. In addition, the ratio of SBR to CMC in the negative electrode is equally important.