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Composite membrane and preparation method thereof and battery comprising composite membrane

A technology of composite diaphragm and porous membrane, which is applied in the direction of secondary batteries, battery pack parts, chemical instruments and methods, etc., can solve the problem of uneven pore size of polyimide porous membrane, achieve uniform pore diameter distribution, high Effects of mechanical strength and high thermal stability

Active Publication Date: 2010-02-24
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to overcome the disadvantages of the non-uniform pore size of the polyimide porous membrane in the composite diaphragm of the prior art, and provide a composite diaphragm formed by a polyimide membrane with uniform pore size and good air permeability Its preparation method and battery comprising the composite separator

Method used

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  • Composite membrane and preparation method thereof and battery comprising composite membrane
  • Composite membrane and preparation method thereof and battery comprising composite membrane
  • Composite membrane and preparation method thereof and battery comprising composite membrane

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preparation example Construction

[0020] 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 size 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 1% (...

Embodiment approach

[0048] According to a kind of preferred embodiment of the present invention, the preparation method of polyimide porous membrane of the present invention comprises the steps:

[0049] (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 pore-forming substances, the weight ratio of pore-forming substances 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;

[0050] (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;

[0051] (3) immersing the support body of the above-mentioned polyamic a...

Embodiment 1

[0071] This embodiment illustrates the preparation of the composite membrane provided by the invention

[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 (solid content It means that the weight of the polyamic acid generated in the system accounts for the mass percentage of the total weight of the mixture) 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);

[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 remove...

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Abstract

The invention discloses a composite membrane and a preparation method thereof and a battery comprising the composite membrane. The composite membrane comprises a polyolefin porous membrane layer and apolyimide porous membrane layer, wherein the composite membrane also comprises an adhesive layer; the adhesive layer is positioned between the polyimide porous membrane layer and the polyolefin porous membrane layer and tightly attached to the polyolefin porous membrane layer and the polyimide porous membrane layer; and the pore diameter distribution of a polyimide porous membrane comprises that:the pore volume of pores of which pore diameters are 50 to 300 nanometers accounts for over 75 percent of the total pore volume, and the pore volume of pores of which pore diameters are less than 50nanometers and more than 300 nanometers accounts for less than 25 percent of the total pore volume, and the pore diameter is measured by adopting a mercury intrusion method. A lithium ion battery manufactured by using the composite membrane as a battery membrane has improved service life and improved processing yield. Moreover, the composite membrane also has high thermal stability, and greatly improves the safety performance of the battery.

Description

technical field [0001] The invention relates to a composite diaphragm and a preparation method of the composite diaphragm, and also relates to a battery comprising the composite 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 lithium-ion batteries. ...

Claims

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Application Information

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IPC IPC(8): H01M2/14H01M2/16B32B7/12B32B27/32B32B27/34B32B37/00H01M10/40H01M50/403H01M50/417H01M50/423H01M50/449H01M50/491
CPCY02E60/12Y02E60/10
Inventor 杨卫国江林
Owner BYD CO LTD
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