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A compound diaphragm for lithium ion battery and its making method

A lithium battery and separator technology, applied in the field of composite separators for lithium ion batteries and their preparation, can solve the problems of low composite strength, reduced melt strength, and difficulty in stretching of multi-layer films, so as to solve the problems of interlayer compatibility. Sexual problems, good melt strength, and the effect of easy stretching

Inactive Publication Date: 2008-08-13
SHENZHEN SENIOR TECH MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Using this method, the microporous membranes currently produced industrially are basically HDPE single-layer isolation membranes, which have disadvantages such as insufficient safety and insufficient puncture resistance.
[0006] If the multilayer microporous membrane is produced by thermally induced phase separation, if PE and PP layers are directly compounded, on the one hand, due to the compatibility problem between the two, the composite strength of the multilayer film is likely to be low; After the diluent is mixed, the diluent destroys the crystallization ability of PP itself, the melt strength of the mixed system is significantly reduced, and it is difficult to carry out subsequent processing operations such as stretching. question

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] 30% (weight) of high-density polyethylene (weight average molecular weight 2.7 × 10 5, melting point 133°C) into twin-screw extruder A (diameter 78mm, L / D=50, strong mixing type), add 70% (weight) of liquid paraffin (kinematic viscosity) through the side feeding port with a metering pump 90cst / 40°C), under the conditions of 200°C and 150 rev / min, melt kneading is prepared into solution A; 30% (weight) of ethylene-propylene block copolymer (85% crystallinity, melting point > 170°C, 7% ethylene content) into twin-screw extruder B (diameter 78mm, L / D=50, strong mixing type), add 70% (weight) of liquid paraffin (kinematic viscosity) through the side feeding port with a metering pump 90cst / 40°C), melted and kneaded at 230°C and 150 rpm to prepare solution B; then mixed solution A and solution B in a T-shaped die for B / A / B three-layer co-extrusion, The thickness ratio of B / A / B three layers is 3:4:3, and the cast sheet is cooled on the casting roller to obtain a thick sheet w...

Embodiment 2

[0038] 30% (weight) of high-density polyethylene (weight average molecular weight 2.7 × 10 5 , melting point 133°C) into twin-screw extruder A (diameter 78mm, L / D=50, strong mixing type), add 70% (weight) of liquid paraffin (kinematic viscosity) through the side feeding port with a metering pump 90cst / 40°C), under the conditions of 200°C and 150 rev / min, melt kneading is prepared into solution A; 30% (weight) of propylene-ethylene block copolymer (85% crystallinity, melting point > 170°C, 3% ethylene content) into the twin-screw extruder B (78mm in diameter, L / D=50, strong mixing type), add 70% (weight) of liquid paraffin (kinematic viscosity) through the side feeding port with a metering pump 90cst / 40°C), melted and kneaded at 230°C and 150 rpm to prepare solution B; then mixed solution A and solution B in a T-shaped die for B / A / B three-layer co-extrusion, The thickness ratio of B / A / B three layers is 1:1:2, and the cast sheet is cooled on the casting roll to obtain a thick s...

Embodiment 3

[0040] 25% (weight) of high-density polyethylene (weight-average molecular weight 2.7 × 10 5 , melting point 133 ℃), 5% (weight) of ethylene and octene copolymer (octene content 15%, MFI 1.0g / 10min) drop into twin-screw extruder A (diameter 78mm, L / D=50, strong mixing In refining type), use a metering pump to add 70% (weight) liquid paraffin (kinematic viscosity 90cst / 40°C) through the side feeding port, melt and knead under the conditions of 200°C and 150 rpm to prepare solution A ; Put 30% (weight) of propylene-ethylene block copolymer (85% crystallinity, melting point>170°C, 7% ethylene content) into twin-screw extruder B (diameter 78mm, L / D=50, strong mixing In refining type), use a metering pump to add 70% (weight) liquid paraffin (kinematic viscosity 90cst / 40°C) through the side feeding port, melt and knead under the conditions of 230°C and 150 rpm to prepare solution B ; Finally, solution A and solution B are mixed in the T-shaped die head to carry out B / A / B three-laye...

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Abstract

The present invention discloses a composite isolating film used by the lithium cell which is the microporous film with B / A / B three-layer structure, wherein layer A is a copolymer film of ethene and other alkene for 1-25(weight percentage); layer B is a copolymer film of propylene and other alkene for 1-5(weight percentage). The originator of the invention adopts the copolymer film of ethene and other alkene, and adopts the copolymer film of propylene and other alkene for a minute quantity in the other layer for preparing a microporous film with B / A / B three-layer sandwich. The copolymer of ethene and other alkene provides a low pore closing temperature, the copolymer film of propylene and minute-quantity other alkene provides high film breaking temperature, high flux strength and adhesive force in the layer A formed by polythene or vinyl copolymer, thereby obtaining an isolating film which has the advantages of low pore closing temperature, high film breaking temperature, high flux strength and high using security.

Description

technical field [0001] The invention relates to the technical field of a composite separator for lithium ion batteries and a preparation method thereof. Background technique [0002] Polyolefin microporous film is a plastic film with numerous interconnected micropores with a pore size of 0.01-10 μm. Used as a separator in lithium batteries. Lithium-ion batteries consist of positive and negative electrodes, a separator, and an electrolyte. Among them, the separator connects and separates the positive electrode and negative electrode materials. It is an insulator of electrons, but it allows ions to pass through. The performance of the separator determines the interface structure and internal resistance of the battery, which in turn affects the capacity, cycle, charge and discharge of the battery. Therefore, the performance of the separator plays an important role in improving the overall performance of the battery. [0003] Safety is the first index to be considered in the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M2/14B32B27/00B32B37/00C08J5/22H01M50/403H01M50/417H01M50/457H01M50/489H01M50/491
CPCY02E60/10
Inventor 杨梅
Owner SHENZHEN SENIOR TECH MATERIAL
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