Porous diaphragm, preparation method thereof and lithium ion battery

A technology of porous diaphragm and pore size, applied in the field of porous diaphragm and its preparation method and lithium ion battery, can solve the problems of electrospinning being susceptible to vibration and electric field interference, poor strength of spinning film, short circuit of battery, etc., and achieve high consistency , The effect of low battery internal resistance and uniform thickness

Active Publication Date: 2020-05-05
HUIZHOU BYD BATTERY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although this method is simpler than the nuclear track etching method, in an industrial environment, electrospinning is susceptible to vibration and electric field interference. At the same time, the pore size of the lithium battery separator prepared under this method is too large, and some pores are larger than 10 μm. Silk films are usually less strong
If it is used in a lithium-ion battery without treatment, it is very easy to cause a short circuit in the battery

Method used

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  • Porous diaphragm, preparation method thereof and lithium ion battery
  • Porous diaphragm, preparation method thereof and lithium ion battery
  • Porous diaphragm, preparation method thereof and lithium ion battery

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preparation example Construction

[0047] A second aspect of the present invention provides a method for preparing a porous membrane, the method comprising:

[0048] (1) Organic solvent and crystalline polyimide are mixed, dissolved, and defoamed to obtain a casting solution;

[0049] (2) Using the casting solution to prepare a diaphragm to obtain a diaphragm;

[0050] (3) The separator is placed for 5-60 minutes under constant temperature and humidity conditions with a humidity of 30%-90%RH and a temperature of 10-70°C to obtain a porous separator.

[0051] In the above preparation method, the volatilization of the organic solvent will take away the heat, reducing the temperature of the organic solvent in the diaphragm, and the temperature difference between the ambient temperature and the temperature of the organic solvent will cause condensation of water droplets in the humidity environment, and the condensed water droplets will penetrate Through the organic solvent, the immiscibility between water and crys...

Embodiment 1

[0068] Prepare an N-methylpyrrolidone solution with a mass fraction of 25% ether anhydride polyimide. After stirring until completely dissolved, let it stand for a period of time, and wait for the casting solution to be completely degassed before use.

[0069] Apply the casting solution to the glass plate with a scraper to prepare the diaphragm, place the glass plate with the diaphragm in a constant temperature and humidity box, set the temperature at 50°C, the humidity at 60% RH, and the time for 30 minutes. Take it out when the volatilization is complete and form a film, and make a porous separator C1.

[0070] The morphology of porous separator C1 was measured by field emission scanning electron microscope JEOL-7600F as follows: figure 1 with figure 2 As shown, compared with the scale on the figure, it can be seen that the pore size is 100-500 nm and the thickness is 50 μm.

[0071] And further test the air permeability, tensile strength, heat shrinkage resistance, etc....

Embodiment 2

[0073] Prepare a chloroform solution with a mass fraction of 10% ketone anhydride polyimide. After stirring until completely dissolved, let it stand for a period of time, and wait for the casting solution to be completely degassed before use.

[0074] The casting liquid is poured into a specific mold by pouring method, and placed in a constant temperature and humidity box with a set temperature of 40°C, a humidity of 60% RH, and a time of 30 minutes. Take it out when the solvent is completely evaporated and the film is formed, and the porous diaphragm is made. C2.

[0075] The morphology of porous separator C2 was measured by field emission scanning electron microscope JEOL-7600F as image 3 with Figure 4 As shown, compared with the scale on the figure, it can be seen that the pore size is 100-200 nm and the thickness is 20 μm.

[0076] And further test the air permeability, tensile strength, heat shrinkage resistance, etc. of the separator.

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Abstract

The invention relates to the field of lithium ion batteries, in particular to a porous diaphragm, a preparation method thereof and a lithium ion battery. The pore size of the porous diaphragm is 0.03-10 [mu]m, the air permeability is 20-500 sec / 100 ml, and the tensile strength is 30-200 MPa; and the porous diaphragm contains crystalline polyimide. The porous diaphragm provided by the invention hasthe properties of good air permeability and tensile strength, excellent thermal stability, high conductivity and the like, and the lithium ion battery prepared from the diaphragm has good charge-discharge rate performance and safety performance.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a porous diaphragm, a preparation method thereof and a lithium ion battery. Background technique [0002] The polymer separators currently used in lithium-ion batteries mainly include polyethylene PE, polypropylene PP, polyethylene terephthalate, polyimide, and the like. Among them, polyethylene and polypropylene are the most widely used. These polyolefin separators have ideal tensile strength (100-150MPa), low price, easy processing and other characteristics. However, the thermal stability and electrolyte affinity of the polyolefin separator are not ideal. Therefore, polyimide is regarded as a promising alternative material to replace traditional polyolefin separators. [0003] CN105322119A discloses a method for preparing a porous polyimide membrane by weather-induced phase transition. The porous diaphragm prepared by the method has a pore size of 0.05-10 nm and a porosi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M2/14H01M10/0525
CPCH01M10/0525H01M50/403H01M50/411Y02E60/10
Inventor 龚河卿胡家玲单军
Owner HUIZHOU BYD BATTERY
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