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Polyolefin microporous membrane, making method thereof, and lithium ion battery

A polyolefin microporous film and microporous film technology, applied in secondary batteries, battery pack parts, circuits, etc., can solve the problems of inability to maintain melt integrity, temperature rise, strength reduction, etc., and achieve improved film rupture. Effects of temperature and high temperature melt integrity, good processability, moderate porosity

Active Publication Date: 2016-02-24
乐凯胶片股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The content disclosed in this invention includes that when the content of polypropylene in the mixed resin exceeds 45%, the micropores related to the safety performance disappear, the temperature rises, and it is difficult to obtain a uniform film, so that its strength decreases
In addition, the blend has a single-phase continuous structure of polyethylene, and polypropylene is dispersed between the continuous phases of polyethylene in an "island" structure, which cannot form a continuous polypropylene skeleton structure, so the melt cannot be kept intact at high temperatures Sex, low membrane rupture temperature, limited improvement in safety performance

Method used

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  • Polyolefin microporous membrane, making method thereof, and lithium ion battery
  • Polyolefin microporous membrane, making method thereof, and lithium ion battery
  • Polyolefin microporous membrane, making method thereof, and lithium ion battery

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preparation example Construction

[0048] 2. Preparation method of polyolefin microporous membrane

[0049] 2.1 Description of raw materials and process parameters

[0050] In order to give full play to the performance advantages of polyethylene resin and polypropylene resin, the present invention uses a pre-blending method to mix two different polyolefin resins together, which can not only form a uniform blend, but also achieve excellent blending performance.

[0051] In order to obtain a blend with good compatibility, according to the principle of similar compatibility, the present invention selects polypropylene resin and polyethylene resin with similar viscosity values ​​for blending. The polyethylene resin and polypropylene resin used in the present invention have intrinsic viscosity values ​​between 200ml / g-1000ml / g, and the difference between the two is less than 100ml / g.

[0052] The present invention has no special limitation on the process of preparing polyolefin masterbatch by twin-screw extruder, ...

Embodiment 1

[0071] a. Preparation of polyolefin masterbatch:

[0072] Add polypropylene resin with an intrinsic viscosity of 560ml / g and polyethylene resin with an intrinsic viscosity of 480ml / g into a twin-screw extruder, melt and knead at 220°C, and pelletize after extrusion. After two consecutive granulations, the polyolefin masterbatch is obtained for use. Among them, polypropylene resin accounts for 65% of the total, and polyethylene resin accounts for 35% of the total.

[0073] b. Preparation of oily slabs:

[0074] Add polyolefin masterbatch and liquid paraffin into the twin-screw extruder from different feeding ports and melt and knead at 215°C. After extruding from the die, cool down with a 40°C cooling roll to make phase separation to make oil-containing thick piece. Among them, the masterbatch accounts for 40% of the total weight of the oily slab, and the liquid paraffin accounts for 60% of the total weight of the oily slab.

[0075] c. Biaxially stretch the oil-containing ...

Embodiment 2

[0080] a. Preparation of polyolefin masterbatch:

[0081] Add a polypropylene resin with an intrinsic viscosity of 900ml / g and a polyethylene resin with an intrinsic viscosity of 1000ml / g into a twin-screw extruder, melt and knead at 260°C, and pelletize after extrusion. After three times of continuous granulation, polyolefin masterbatches are obtained for future use. Among them, polypropylene resin accounts for 50% of the total, and polyethylene resin accounts for 50% of the total.

[0082] b. Preparation of oily slabs:

[0083] Add polyolefin masterbatch and liquid paraffin into the twin-screw extruder from different feeding ports and melt and knead at 220°C. After extruding from the die, cool down with a 60°C cooling roll to make phase separation to make oily thick piece. Among them, the masterbatch accounts for 30% of the total weight of the oily slab, and the liquid paraffin accounts for 70% of the total weight of the oily slab.

[0084] c. Biaxially stretch the oil...

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Abstract

The invention relates to a polyolefin microporous membrane, a making method thereof, and a lithium ion battery. The skeleton structure of the microporous membrane is formed by a polypropylene and polyethylene two-phase continuous phase, wherein the mass percentage of polypropylene resin is 50-65%, the mass percentage of polyethylene resin is 35-50%, the intrinsic viscosities of the polypropylene resin and the polyethylene resin are 200-1000ml / g respectively, and a difference between the intrinsic viscosities of the polypropylene resin and the polyethylene resin is 100ml / g. The microporous membrane has the advantages of large safety window, excellent integrity of a high temperature melt, and great improvement of the safety performance of the battery when the microporous membrane is used in the lithium ion battery.

Description

technical field [0001] The invention relates to a microporous membrane material for lithium ion batteries, in particular to a polyolefin microporous membrane for lithium ion batteries. Background technique [0002] Lithium-ion batteries, especially power lithium-ion batteries, not only require the diaphragm to have excellent mechanical strength and permeability and other conventional physical properties, but also require the diaphragm to have an enlarged safety window and good heat resistance from the perspective of battery safety. performance. [0003] When the inside of the battery is overheated due to overcharging, etc., the separator melts to form a film covering the electrodes, and the micropores are closed to block the current to ensure the safety of the battery. This temperature is called the "closed cell temperature" of the membrane. The lower the closed cell temperature, the safer the battery. When the continuous high temperature inside the battery reaches a cert...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/14H01M2/16H01M10/0525H01M50/403H01M50/417H01M50/489
CPCH01M10/0525H01M50/409H01M50/403Y02E60/10
Inventor 宋红芹韩继庆张永升
Owner 乐凯胶片股份有限公司
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