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Polyimide porous membrane, preparation method thereof and lithium ion battery

A technology of polyimide and polyamic acid film, which is used in battery pack parts, circuits, electrical components, etc., to achieve the effects of improved processing yield, improved service life and good safety performance.

Active Publication Date: 2012-01-25
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The object 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 membrane with uniform pore size Amine porous membrane and preparation method thereof, also provides a lithium ion battery using the porous membrane as a battery separator

Method used

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  • Polyimide porous membrane, preparation method thereof and lithium ion battery
  • Polyimide porous membrane, preparation method thereof and lithium ion battery
  • Polyimide porous membrane, preparation method thereof and lithium ion battery

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preparation example Construction

[0016] The preparation method of the polyimide porous membrane provided by the invention comprises forming a polyamic acid membrane from a mixture containing polyamic acid, a pore-forming substance and a solvent, contacting the polyamic acid membrane with a coagulation solution, and performing imidization , the solvent is a solvent that dissolves polyamic acid but slightly soluble or insoluble pore-forming substances, and the coagulation liquid is a liquid that dissolves pore-forming substances but slightly soluble or insoluble polyamic acid. "Slightly soluble" described herein means that the solubility is less than 1 g / 100 g solvent and greater than 0.01 g / 100 g solvent; "insoluble" means that the solubility is less than 0.01 g / 100 g solvent.

[0017] According to the preparation method provided by the present invention, preferably, the weight ratio of the pore-forming substance to the polyamic acid is 0.01-0.3:1, and the weight ratio of the polyamic acid to the solvent is 1:4...

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 5 - 50 micron polyamic acid film;

[0052] (3) immersing the support body of the above-mentioned pol...

Embodiment 1

[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 . Stir the reaction at 25°C for 8 hours, then add 3 grams of propylene glycol methyl ether acetate, and vacuum degassing at this temperature for 1 hour to obtain a viscous mixture with an intrinsic viscosity η int =150 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 solvent is removed to obtain a polyamic acid film;

[0068] (3) Dip the above-mentioned stainless steel plate with polyamic acid film in 100 ml of coagulation solution composed of ethanol, ether and acetone (the volume ratio of ethanol, ether and acetone is 3:2:1) at 20°C fo...

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Abstract

The invention provides a polyimide porous membrane. The aperture distribution of the porous membrane made from the polyimide is as follows: the pores of which the pore diameter is 40 to 280 nanometers account for over 75 percent of the total pore volume; and the pores of which the pore diameter is less than 40 nanometers and more than 280 nanometers account for less than 25 percent of the total pore volume. The invention also provides a preparation method of the polyimide porous membrane and a lithium ion battery which takes the membrane as a diaphragm. The polyimide porous membrane of the invention has a uniformly distributed pore diameter and relatively high mechanical strength so that the service life and the finished product ratio of the lithium ion battery which takes the membrane asthe diaphragm thereof are improved. In addition, the membrane has a relatively high thermal stability, thereby greatly improving the safety of the battery.

Description

technical field [0001] The invention relates to a polyimide porous membrane, a preparation method of the polyimide porous membrane, and a lithium ion battery using the porous membrane as a battery diaphragm. 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 lit...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M2/14C08J5/22C08J9/00H01M50/403H01M50/423H01M50/489
CPCY02E60/12Y02E60/10
Inventor 杨卫国江林宫清
Owner BYD CO LTD