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Lithium ion battery diaphragm and preparation method thereof

A lithium-ion battery and diaphragm technology, applied in the field of lithium-ion battery diaphragm and its preparation, can solve the problems of poor air permeability of products, low adhesion between coating and pole piece, low proportion of ceramics, etc., and achieve the accumulation of small molecules Weakening, the effect of good pole piece bonding performance and good heat resistance

Inactive Publication Date: 2020-05-22
DONGGUAN DONGYANG SOLAR SCI RES & DEV CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

There are two problems in the wet-process lithium battery separator at this stage: one is that the heat resistance is poor, and the melting point of the raw material polyethylene is low, which leads to obvious thermal shrinkage of the separator in a high-temperature environment; The adhesion of the sheet is weak, and the positive and negative electrode materials will expand and shrink when the lithium battery is charged and discharged, which will lead to deformation and displacement of the diaphragm
For the product prepared by this method, since the particle size of PVDF particles is about 200nm and the particle size of ceramic particles is about 500nm, after the two kinds are mixed and coated, the accumulation effect of large and small particles will be formed, resulting in a decrease in the air permeability of the product.
Moreover, due to the accumulation and coverage of the two kinds of particles, if the proportion of PVDF in the mixed slurry is low, the adhesion between the coating and the pole piece is very low; if the proportion of PVDF is high, the proportion of ceramics will be low, and the heat resistance of the product will be lower. poor performance
[0006] A series of existing technologies represented by the above three patents, in order to simultaneously improve the heat resistance of diaphragm products and the bonding performance of pole pieces, respectively adopt ceramic / PVDF secondary coating, ceramic surface spraying PVDF and ceramic / PVDF mixed coating and other methods, the prepared composite diaphragm is prone to problems such as obvious increase in thickness, poor air permeability of the product, complicated coating process and low efficiency.

Method used

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  • Lithium ion battery diaphragm and preparation method thereof
  • Lithium ion battery diaphragm and preparation method thereof
  • Lithium ion battery diaphragm and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0066] Preparation of PVDF copolymer resin suspension:

[0067] Add 100kg of deionized water and 0.1kg of polyvinyl alcohol dispersant to the reaction kettle, vacuumize and replace with nitrogen, so that the oxygen content in the kettle is lower than 30ppm. Start the mechanical stirring, control the stirring speed to 800r / min, and raise the temperature of the reaction kettle to 29°C. The VDF monomer and the HFP monomer are uniformly mixed and passed into the reactor, wherein HFP accounts for 1% of the total mass of the comonomers, and the internal pressure of the reactor is controlled to be 4.5 MPa. Add 0.001kg of diisopropyl peroxydicarbonate initiator and 0.04kg of diethyl malonate chain transfer agent to start the polymerization reaction. During the polymerization process, continuously replenish mixed monomers to keep the pressure in the kettle at 4.5MPa. When the cumulative reaction amount of the monomer is 20kg, the reaction is terminated, the reaction time is 7.2h, and ...

Embodiment 2

[0071] Preparation of PVDF copolymer resin suspension:

[0072] Add 100kg of deionized water and 0.4kg of methylcellulose dispersant to the reaction kettle, vacuumize and replace with nitrogen, so that the oxygen content in the kettle is lower than 30ppm. Start the mechanical stirring, control the stirring speed to 1000r / min, and raise the temperature of the reaction kettle to 27°C. The VDF monomer and the HFP monomer are uniformly mixed and passed into the reactor, wherein HFP accounts for 5% of the total mass of the comonomers, and the pressure inside the reactor is controlled to be 5.0 MPa. Add 0.002 kg of tert-butyl peroxyisobutyrate initiator and 0.02 kg of butyl acetate chain transfer agent, and the polymerization reaction starts. During the polymerization process, the mixed monomers are constantly replenished to keep the pressure in the kettle at 5.0 MPa. When the cumulative monomer reaction amount is 20kg, the reaction is terminated, the reaction time is 6.3h, and the...

Embodiment 3

[0076] Preparation of PVDF copolymer resin suspension:

[0077] Add 100kg of deionized water and 0.6kg of hydroxymethyl cellulose dispersant to the reaction kettle, vacuumize and replace with nitrogen, so that the oxygen content in the kettle is lower than 30ppm. Start the mechanical stirring, control the stirring speed to 1500r / min, and raise the temperature of the reaction kettle to 29°C. The VDF monomer and the HFP monomer are uniformly mixed and passed into the reactor, wherein HFP accounts for 10% of the total mass of the comonomers, and the pressure inside the reactor is controlled to be 5.5 MPa. Add 0.02 kg of di-tert-butyl peroxide initiator and 0.16 kg of butyl diacetate chain transfer agent to start the polymerization reaction. During the polymerization process, the mixed monomers are continuously replenished to keep the pressure in the kettle at 5.5 MPa. When the cumulative monomer reaction amount is 20kg, the reaction is terminated, the reaction time is 3.6h, and ...

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Abstract

The invention provides a lithium ion battery diaphragm and a preparation method thereof. The diaphragm comprises a base material and a coating coated on at least one surface of the base material, thecoating comprises ceramic particles and PVDF copolymer resin, the ceramic particles are continuously distributed in the coating, and the PVDF copolymer resin is embedded in the ceramic particles and protrudes out of the coating. The invention also provides a preparation method of the diaphragm. In the diaphragm, the small molecule accumulation effect of large-particle PVDF is weakened, the air permeability of the diaphragm is improved, PVDF particles protruding out of a coating play a role in bonding with a pole piece, the diaphragm has good heat resistance and pole piece bonding performance at the same time, and the additional value of a diaphragm product can be remarkably improved. And the preparation method adopts one-time coating, the process is simple, and the production efficiency ishigh.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery diaphragm and a preparation method thereof. Background technique [0002] With the development of technology and the promotion of national policies, the new energy automobile industry has developed rapidly. Lithium-ion batteries for new energy vehicles generally use wet-process lithium battery separators for lamination or winding. There are two problems in the wet-process lithium battery separator at this stage: one is that the heat resistance is poor, and the melting point of the raw material polyethylene is low, which leads to obvious thermal shrinkage of the separator in a high-temperature environment; The adhesion of the sheet is weak, and the positive and negative electrode materials will expand and shrink when the lithium battery is charged and discharged, which will lead to deformation and displacement of the separator. [0003] In ord...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M2/16H01M2/14H01M10/0525
CPCH01M10/0525H01M50/403H01M50/446H01M50/449Y02E60/10
Inventor 李义涛程宗盛杨华军云晧郑炳发张魁黄连红吴慧娟肖文武
Owner DONGGUAN DONGYANG SOLAR SCI RES & DEV CO LTD
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