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Stretched polyimide porous membrane, preparation method and lithium ion battery thereof

A polyimide and porous membrane technology, applied in battery pack parts, circuits, flat products, etc., can solve the problems of poor membrane tensile strength and uneven pore size of polyimide membrane, and achieve the processing yield Improved, uniform pore diameter distribution, high thermal stability effect

Active Publication Date: 2011-07-27
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 uneven pore size and poor tensile strength of the polyimide membrane in the above-mentioned prior art, and provide a stretched polyimide film with uniform pore size and high tensile strength. Amine porous membrane, preparation method thereof, and battery obtained from the stretched polyimide porous membrane

Method used

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  • Stretched polyimide porous membrane, preparation method and lithium ion battery thereof
  • Stretched polyimide porous membrane, preparation method and lithium ion battery thereof
  • Stretched polyimide porous membrane, preparation method and lithium ion battery thereof

Examples

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preparation example Construction

[0025] According to the preparation method provided by the present invention, according to the above-mentioned first pore-forming principle, the pore-forming substance is selected from one of hydroxides of alkaline earth metal elements, aluminum hydroxide, phosphates of alkali metals and sodium tripolyphosphate Or several, and the average particle diameter is 0.01-2 microns. Wherein, the hydroxide of the alkaline earth metal element is magnesium hydroxide and / or calcium hydroxide; the phosphate of the alkali metal is trisodium phosphate and tripotassium phosphate. The coagulation solution is one or more of hydrochloric acid, sulfuric acid and phosphoric acid. Experiments have shown that one or more of hydrochloric acid, sulfuric acid and phosphoric acid is selected from the hydroxides of alkaline earth metal elements, aluminum hydroxide, alkali metal phosphates and sodium tripolyphosphate as pore-forming substances. Or the solubility of several kinds at 25°C is not more than ...

Embodiment approach

[0053] According to a preferred embodiment of the present invention, the preparation method of the stretched polyimide porous membrane provided by the present invention comprises the following steps:

[0054] (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;

[0055] (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;

[0056] (3) immersing the support body of...

Embodiment 1

[0071] This example is used to illustrate the preparation of stretched polyimide porous membrane

[0072] (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 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);

[0073] (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 a...

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Abstract

The invention relates to a stretched polyimide porous membrane, a preparation method and a lithium ion battery thereof. The stretched polyimide porous membrane is obtained by stretching a polyamic acid porous membrane and then carrying out imidization on the polyamic acid porous membrane, wherein the polyamic acid porous membrane has the pore size distribution that pore volumes of pores with porediameters of 50-300 nanometers account for more than 75 percent of the total pore volume, the pore volumes of pores with pore diameters being larger than 300 nanometers account for lower than 25 percent of the total pore volume, and the pore diameters are measured by a mercury intrusion method. The invention also provides a preparation method of the stretched polyimide porous membrane and a battery made of the stretched polyimide porous membrane. The stretched polyimide porous membrane has uniform pore diameter distribution and higher mechanical strength so as to ensure that the service life of the lithium ion battery which is made by using the porous membrane as a battery diaphragm is prolonged, and the processing yield is improved. In addition, the stretched 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 stretched polyimide porous membrane and a preparation method thereof, and also relates to a lithium ion battery comprising the stretched polyimide 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 fo...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08J9/36C08J9/26C08L79/08B29C55/02H01M2/16B29L7/00B29K77/00H01M50/403H01M50/423
CPCY02E60/12Y02E60/10
Inventor 杨卫国任敬宇江林
Owner BYD CO LTD
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