Film with uniform water absorption, and preparation method thereof

Abstract

The invention provides a film with uniform water absorption, and a preparation method thereof. The preparation method comprises the following steps: mixing and heating polyethylene, paraffin oil, silicon dioxide nanoparticles and 4,4'-sulfo-bis(6-tert-butyl-m-cresol) in batches, carrying out extrusion molding, respectively carrying out transverse stretching and longitudinal stretching, carrying out two-dimensional stretching according to the light transmittance distribution of a film, spraying water after stretching is completed, determining a to-be-stretched area according to a water layer distribution diagram, carrying out two-dimensional stretching, and carrying out drying and film forming to obtain the lithium battery diaphragm with the uniform water absorption characteristic.

Description

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

AI Technical Summary

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] In particular, the uneven size and porosity of the separator will greatly affect the safety of the battery. Film breakdown is prone to occur in the position with large pores and large porosity, while in the position with small pores and small porosity location where electrical performance is affected

In the prior art, ① can only be tested for the above-mentioned single parameter, and cannot be considered comprehensively; ② is only tested after the final preparation is completed, and even if a problem is found, the front-end process cannot be fed back and controlled. It belongs to the quality inspection type of detection, not the production process. ③ Even for a single parameter, the existing technology only detects the size of porosity and opening size, but does not propose to detect the uniformity of pore distribution and the uniformity of opening size

[0006] However, if a method that can comprehensively characterize each parameter is selected for process control, the control accuracy of the process will be higher, and there is no mention in the prior art of how to use a simple method to realize the process control of this composite parameter

Images