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Polyimide porous membrane and lithium ion battery comprising same

A polyimide and polyamic acid film technology, applied in secondary batteries, battery pack parts, circuits, etc., can solve the problem of uneven pore size of polyimide film, and achieve good air permeability and high mechanical strength. The effect of uniform distribution of strength and pore diameter

Active Publication Date: 2011-09-28
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The purpose of the present invention is to overcome the disadvantages of the uneven pore size of the polyimide membrane in the above-mentioned prior art, and provide a polyimide porous membrane with uniform pore size and a lithium ion battery comprising the porous membrane.

Method used

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  • Polyimide porous membrane and lithium ion battery comprising same
  • Polyimide porous membrane and lithium ion battery comprising same
  • Polyimide porous membrane and lithium ion battery comprising same

Examples

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Embodiment approach

[0049] According to a preferred embodiment of the present invention, the preparation method of polyimide porous membrane provided by the present invention comprises the steps:

[0050] (1) Tetraacid dianhydride and organic diamine are added to the solvent according to the molar ratio of 0.8-1.2:1, the amount of solvent used is such that the concentration of the obtained polyamic acid is 5-40% by weight, at 20-70°C After stirring and reacting for 3-15 hours, add a pore-forming substance, the weight ratio of the pore-forming substance to the obtained polyamic acid is 0.01-0.3:1; vacuum degassing at the same temperature for 1-12 hours to obtain a polyamic acid solution;

[0051] (2) At a temperature of 10-40°C and a relative humidity of 20-80%, the above polyamic acid solution is coated on a stainless steel or glass support, dried at 20-200°C, and the solvent is removed to obtain 8 - 30 micron polyamic acid film;

[0052] (3) the porous polyamic acid film obtained above is heate...

Embodiment 1

[0065] This embodiment is used to illustrate the preparation of the polyimide porous membrane provided by the present invention

[0066] (1) 4,4'-diaminodiphenyl ether and pyromellitic dianhydride are added to 300 milliliters of N,N-dimethylacetamide at a molar ratio of 1:1, wherein the solid content is 10% by weight (Solid content refers to the mass percentage of the weight of polyamic acid generated in the system to the total weight of the mixture). Stir the reaction at 25°C for 8 hours, then add 3 grams of pore-forming substance diisooctyl phthalate, and vacuum degassing at this temperature for 1 hour to obtain a viscous mixture with an intrinsic viscosity η int =175 ml / g (measurement conditions: Ubbelohde viscometer, constant temperature 30°C, the mixture is diluted to a solid content of 0.005 g / ml);

[0067] (2) At a temperature of 10°C and a relative humidity of 50%, the above mixture is coated on a stainless steel plate, dried at 100°C for 20 minutes, and then the solv...

Embodiment 2

[0072] This embodiment is used to illustrate the preparation of the polyimide porous membrane provided by the present invention

[0073] Prepare polyimide porous membrane according to the method for embodiment 1, difference is, the pore-forming substance that adds in step (1) is 4.5 grams of trioctyl trimellitate, obtains the mixture of viscous shape, the mixture of Intrinsic viscosity ηint=148 ml / g (measurement conditions: Ubbelohde viscometer, constant temperature 30°C, the mixture is diluted to a solid content of 0.005 g / ml). The way of heating is to keep at 80°C for 1 hour, at 150°C for 1 hour, and at 350°C for 1 hour. Finally, a polyimide porous membrane with a thickness of 18 micrometers was obtained.

[0074] Mercury porosimetry is used to measure the pore diameter of the polyimide porous membrane obtained above. The pore volume of the pores with a pore diameter of 130-380 nanometers accounts for 76% of the total pore volume, and the average pore diameter of the film i...

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Abstract

The invention discloses a polyimide porous membrane and a lithium ion battery comprising the same. The polyimide porous membrane is prepared by the following method, and the method comprises the following steps: forming a polyamic acid membrane by using the mixture of a mixture containing polyamic acid, pore-forming substance and solvent, and subjecting the polyamic acid membrane to amidation at the temperature higher than the decomposing temperature of the pore-forming substance, wherein the solvent is a solvent which dissolves the polyamic acid but slightly dissolves or does not dissolve the pore-forming substance; and the pore-forming substance may be one or combination of benzoic acid polyol ester, phthalic acid dialkyl ester, polyprotic acid alkyl ester, phenyl alkysulfonate, chlorinated paraffin and epoxidized soybean oil. The service life and the processing yield of the lithium ion battery made of the polyimide porous membrane serving as a battery membrane are improved. Moreover, the polyimide porous membrane also has higher thermal stability, and greatly improves the safety performance of the battery.

Description

technical field [0001] The invention relates to a polyimide porous membrane, and also relates to a lithium ion battery comprising the porous membrane. Background technique [0002] So far, lithium ion secondary batteries using liquid electrolytes have been widely used. However, since the liquid electrolyte needs to be packaged in a sealed metal shell, in some cases of improper use, such as when the battery is working in a high temperature environment, the external heat is transferred to the inside of the battery through the metal shell, or when the discharge current is large. Overheating inside or outside the battery will greatly increase the internal pressure of the battery, and the battery will explode due to the thermal instability of the liquid electrolyte. Therefore, there are potential safety hazards in lithium-ion secondary batteries using liquid electrolytes, which limits the use of liquid electrolytes for lithium-ion batteries. The further development of secondary ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08J5/18C08J9/26H01M2/16C08L79/08H01M50/423H01M50/491
CPCY02E60/12Y02E60/10
Inventor 杨卫国谢征江林
Owner BYD CO LTD
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