Film without grease residue and preparation method thereof

Abstract

The present invention provides a film without grease residue and a preparation method thereof. The method comprises the steps of: mixing and heating polyethylene, paraffin oil, silicon dioxide nanoparticles and 4, 4'-sulfo-bis(6-tert-butyl-m-cresol) in batches, performing extrusion molding, performing transverse stretching and longitudinal stretching respectively, and performing two-dimensional stretching; and after stretching is finished, feeding the film into an oil removal device, and carrying out oil removal operation on the film under the action of an extrusion roller and an oil absorption material, so as to prepare the lithium battery diaphragm without grease residues.

Description

technical field [0001] The invention relates to the technical field of lithium battery diaphragm and its preparation. Background technique [0002] Separator is an important part of lithium battery, which directly determines the performance and safety of lithium battery. Usually the diaphragm is an insulating material with a porous structure. For the separator, it is usually necessary to ensure a certain porosity and opening size, so that ions can migrate smoothly. If it is too high, the strength of the diaphragm will decrease, and if it is too low, the internal resistance will increase. The uniformity of the membrane also affects the electrolyte wetting the membrane, thereby affecting the internal resistance of the battery. Moreover, under abnormal conditions, too much current will cause the temperature to rise to T1, thereby closing the pores of the membrane, thereby stopping ion migration and avoiding further danger. But if the temperature rises too high to T2, it wil...

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Problems solved by technology

But this is time-consuming and labor-intensive, and multi-parameter crossover is difficult to control

At the same time, they did not realize that the consistency of the comprehensive performance of each parameter is of great significance to battery safety and performance improvement.

[0005] However, grease or other solvents are inevitably used in the preparation process of the film. Although it will be extracted in the process, there may still be a small amount of residue. Whether the grease is extracted or not has a great impact on the performance parameters of the film.

If the oil is not extracted, it will directly affect the porosity and air permeability of the separator, and then affect the internal resistance and cycle performance of the battery.

According to the existing technology, if you want to further remove the residual oil, you can only extract it multiple times, which will prolong the extraction time, increase the cost, and more seriously, increase the complexity of the process, so that additional reprocessing is required on the conventional production line. Set up the extraction box

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