Polyimide diaphragm for lithium ion secondary battery and lithium ion battery

A polyimide, secondary battery technology, applied in secondary batteries, battery pack parts, circuits, etc., can solve the problem of poor puncture resistance and high temperature safety performance of battery separators, and the size of polyimide membranes is not large. Uniformity and other issues, to achieve the effect of improving safety performance, uniform hole diameter distribution, and improving work efficiency

Inactive Publication Date: 2010-06-23
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] The purpose of the present invention is to overcome the disadvantages of uneven pore size of the polyimide membrane in the prior art, as well as the defects of poor puncture resistance and high temperature safety performance of the battery separator in the prior art, and provide a polyimide membrane with uniform pore size distribution. A polyimide diaphragm with good safety performance with tortuous communication channels inside, and a lithium-ion battery using the diaphragm as a battery diaphragm

Method used

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  • Polyimide diaphragm for lithium ion secondary battery and lithium ion battery
  • Polyimide diaphragm for lithium ion secondary battery and lithium ion battery
  • Polyimide diaphragm for lithium ion secondary battery and lithium ion battery

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preparation example Construction

[0018] The preparation method of the polyimide diaphragm provided by the present 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 dissolves or does not dissolve pore-forming substances, and the coagulation liquid is a liquid that dissolves pore-forming substances but slightly dissolves or does not dissolve 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.

[0019] Preferably, the weight ratio of the pore-forming substance to the polyamic acid is 0.01-0.3:1, the weight ratio of the polyamic acid to the solvent is 1:4.5-10, and the polyamic acid to the solidified The we...

Embodiment approach

[0053] According to a preferred embodiment of the present invention, the preparation method of polyimide membrane provided by the present invention comprises the 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 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;

[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 the above-mentioned polyamic acid m...

Embodiment 1

[0070] (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);

[0071] (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;

[0072] (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 diaphragm for a lithium ion secondary battery and a lithium ion battery, which is characterized in that along the direction of the thickness, the polyimide diaphragm comprises a first surface and a second surface which are communicated by a tortuous pore channel. The tortuous pore channel is formed by mutual connection of through pores. According to a mercury intrusion method, average pore size distribution of the polyimide diaphragm is as follow: the volume of the pores with diameter of 40-280nm accounts for more than 78% of the total pore volume. The diameter distribution of the pores on the polyimide diaphragm provided by the invention is uniform, a large number of small pores are distributed on the porous diaphragm and the pores are communicated in a tortuous manner, thus improving the service life of the prepared lithium ion battery by using the diaphragm as the battery diaphragm, in addition, the diaphragm also has higher thermal stability, thus greatly improving the safety performance of the battery.

Description

technical field [0001] The invention relates to a polyimide diaphragm, and also relates to a lithium ion battery using the diaphragm 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 lithium-ion batteries. The further development of seco...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/18H01M10/36H01M50/463
CPCY02E60/12Y02E60/10
Inventor 杨卫国江林宫清
Owner BYD CO LTD
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