Production method of high-permeability low-density lithium battery polyolefin diaphragm

Abstract

The invention discloses a production method of a high-permeability low-density lithium battery polyolefin diaphragm. The production method comprises the following steps of 1, preparing a nucleating agent, 2, mixing 50 to 80% of a metallocene-catalyzed polypropylene homopolymer, 20 to 50% of a metallocene-catalyzed polypropylene block copolymer and 1 to 4% of the nucleating agent, extruding the mixture by an extruder to obtain a diaphragm, cooling the diaphragm by a chilling roller at a temperature of 100 to 150 DEG C for 2 to 15 minutes so that a mass of beta-type crystals are produced and fully grows in the diaphragm, and cooling to obtain a casted sheet, and 3, carrying out vertical stretching and horizontal stretching of the casted sheet to obtain the high-permeability low-density lithium battery polyolefin diaphragm having density less than or equal to 0.55g / cm<3> and thickness of 12 to 60 micrometers, wherein a stretching temperature is in a range of 90 to 160 DEG C; and an area stretching ratio is in a range of 8 to 40. The high-permeability low-density lithium battery polyolefin diaphragm obtained by the production method has unique performances of high non-transparency, high gas permeability, low density (high porosity), high moisture permeability and high strength. A stretching ratio of the high-permeability low-density lithium battery polyolefin diaphragm is in a range of 8 to 40. The density of the high-permeability low-density lithium battery polyolefin diaphragm is less than 0.55g / cm<3>, and preferably, is 0.30g / cm<3>.

Description

technical field [0001] The invention relates to a production method of a lithium-ion battery diaphragm. Background technique [0002] Lithium-ion batteries have become a new generation of batteries widely used due to their high voltage, high specific energy, long cycle life and no environmental pollution. The separator, as a key component in lithium-ion batteries, plays the role of isolating the positive and negative electrodes to prevent short-circuiting of the positive and negative electrodes, and provides lithium ion transport channels during the charging and discharging process of lithium batteries. The performance of the diaphragm determines the capacity, internal resistance, cycle, storage, safety and other properties of the lithium battery. It can also block the current conduction in the battery through the closed cell function when the battery is overheated. At present, the production process of polyolefin separator can be divided into two categories: dry method an...

AI Technical Summary

Problems solved by technology

The disadvantages of this method are: the process is complicated, solvents and diluents need to be added, it will cause secondary pollution, and the cost is high

However, the processes taught by the prior art to make films at low draw ratios are not cost-effective

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