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A kind of polymer composite membrane and preparation method thereof and lithium ion battery including same

A polymer and composite film technology, applied in secondary batteries, battery pack parts, circuits, etc., can solve the problems of reduced bonding performance, poor thermal stability of composite films at high temperatures, and poor viscosity, etc., to increase mechanical performance, stability improvements

Active Publication Date: 2021-09-03
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] However, in the foregoing technical solutions, there is a large contradiction between the adhesion between the organic / inorganic composite layer and the porous base layer and the air permeability of the composite membrane.
This is because this organic / inorganic composite layer is formed by coating and relies on the gaps of inorganic particles to form voids. If you want to increase the porosity (permeability) of the organic / inorganic composite layer, you need to reduce the polymer bonding. However, due to the high glass transition temperature of the aforementioned polymer binder, its viscosity is not good. Once the amount of polymer binder is reduced, it will lead to poor bonding performance between the coating and the base layer. reduced, which in turn makes the high temperature thermal stability of this composite film worse

Method used

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  • A kind of polymer composite membrane and preparation method thereof and lithium ion battery including same
  • A kind of polymer composite membrane and preparation method thereof and lithium ion battery including same

Examples

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preparation example Construction

[0034] The preparation method of the ceramic diaphragm provided by the present invention realizes optimal dispersion of ceramic particles by controlling the amount of each component in the ceramic layer slurry, the number average molecular weight of the dispersant, and the rotational speed of the ceramic layer slurry, thereby controlling the packing density between the ceramic particles To control the surface density of the ceramic layer at a unit thickness (1μm) to 1.8mg / cm 2 2 In this way, the high temperature heat shrinkability of the ceramic diaphragm can be improved on the basis of basically not reducing the gas permeability, so that the heat resistance temperature can reach above 160°C, that is, the thermal stability can be improved without increasing the thickness of the ceramic layer, so that Does not affect the energy density of the battery.

[0035] According to the polymer composite membrane of the present invention, preferably, in the ceramic layer, relative to 100...

Embodiment 1

[0087] Embodiment 1 (preparation of two-layer polymer composite film of PE base film-heat-resistant layer)

[0088] This example is used to illustrate the polymer composite membrane provided by the present invention and its preparation method.

[0089] (1) Form a heat-resistant layer on the PE base film:

[0090] Polymphenylene isophthalamide (PMIA) (commercially purchased from Yantai Taihe New Materials Co., Ltd., the same below) and lithium chloride (commercially purchased from Aladdin Reagent Company) with a weight of 0.4% by weight of PMIA weight , analytically pure, the same below) was added to N,N-dimethylacetamide (DMAc) (commercially purchased from Aladdin Reagent Company, the same below), and magnetically stirred in a water bath at 70°C to fully dissolve it to form a polymer A spinning solution having a concentration of 15% by weight of the substance (the aforementioned PMIA).

[0091] One side surface of the PE base film of 11 μm (purchased from Japan SK Company, t...

Embodiment 2

[0097] Embodiment 2 (preparation of three-layer polymer composite film of heat-resistant layer-PE base film-heat-resistant layer)

[0098] This example is used to illustrate the polymer composite membrane provided by the present invention and its preparation method.

[0099] (1) Forming a heat-resistant layer: adopt the method in Example 1 to form the first heat-resistant layer (thickness is 1.5 μ m, porosity 79%) on one side of PE base film earlier, then on the other side of PE base film A second heat-resistant layer (thickness 1.5 μm, porosity 79%) was formed, and polymer composite membrane F2 was obtained after immersion and drying treatment. Detected by an energy spectrometer (EDS), 99.5% by weight of the heat-resistant layer is PMIA, and the rest are solubilizing residues.

[0100] After testing, the transverse tensile strength and longitudinal tensile strength of the polymer composite membrane F2 are 146MPa and 148MPa respectively, the needle punching strength is 0.53kg...

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Abstract

The invention discloses a polymer composite membrane, a preparation method thereof and a lithium ion battery comprising the same. The polymer composite membrane comprises a porous base membrane and a heat-resistant layer covering at least one surface of the porous base membrane. The heat-resistant layer includes a heat-resistant polymer material and has a fiber network structure. The heat-resistant polymer material includes polyparaphenylene terephthalamide, polym-phenylene isophthalamide, and polyparaphenylene terephthalamide. One or more of benzamide, poly-p-phenylenebenzobisoxazole, polyphenylenebenzobithiazole, polybenzoxazole and polybenzimidazole. The polymer composite membrane forms a heat-resistant layer by using a specific heat-resistant polymer material, which is conducive to improving the high-temperature (>180°C) stability of the polymer composite membrane while meeting the porosity requirements of the polymer composite membrane, which is beneficial to Lithium ion migration and improve battery safety performance.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a polymer composite membrane and a preparation method thereof; the invention also includes a lithium ion battery using the aforementioned polymer composite membrane. Background technique [0002] Lithium-ion batteries are mainly composed of positive / negative electrode materials, electrolytes, separators and battery casing packaging materials. The separator is an important part of the lithium-ion battery, which is used to separate the positive and negative electrodes and prevent the internal short circuit of the battery; it allows the electrolyte ions to pass freely to complete the electrochemical charge and discharge process. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the rate performance, cycle performance, and safety performance (high temperature resistance) of the battery. A separator w...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M50/403H01M50/414H01M50/44H01M50/454H01M50/489H01M10/0525H01M50/423H01M50/434H01M50/449H01M50/491
CPCH01M10/0525H01M50/403H01M50/411H01M50/44H01M50/431H01M50/449Y02E60/10
Inventor 胡家玲刘荣华吴金祥单军胡刚何龙
Owner BYD CO LTD
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