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A lithium battery composite separator and its preparation method and application

A composite separator and lithium battery technology, applied in the field of preparation, lithium battery composite separator, and lithium battery, can solve the problems of the peeling strength of the ceramic layer and the PVDF layer, the weakening of the peeling strength of the composite separator layer, and the limited effect of thermal stability, etc. Achieve excellent positive electrode bonding properties, good dimensional stability at high temperature, and improve peel strength

Active Publication Date: 2022-07-12
中材锂膜(宁乡)有限公司
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Problems solved by technology

However, the effect of using ceramic coatings to improve the thermal stability of polyolefin separators is still very limited. In order to further improve the thermal stability of the separator, reduce the thermal shrinkage rate of the separator, and improve the bonding between the separator and the pole piece, the industry A scheme of applying ceramics and polyvinylidene fluoride (PVDF) to polyolefin diaphragms is proposed. For example, patent documents CN104269506A and CN104157819A propose a composite diaphragm structure with polyolefin layer / ceramic layer / PVDF layer stacked, in which the ceramic layer Both the ceramic layer and the PVDF layer are coated with water-based slurry. The adhesion between the ceramic layer and the PVDF layer is good, and the interlayer peel strength of the overall composite separator is high. However, water-based PVDF coating is used to improve the adhesion between the separator and the positive electrode The effect of knot degree is very limited, the adhesion between the water-based PVDF layer and the pole piece is much lower than the adhesion between the oil-based PVDF layer and the pole piece
[0004] However, if a ceramic layer is used to superimpose a PVDF oily coating, the adhesion between the ceramic layer and the oily PVDF oily coating will be poor, resulting in problems with the peel strength between the ceramic layer and the PVDF layer, and the peel strength between the composite separator layers will be weakened. The PVDF layer is easy to fall off during use. Therefore, in order to obtain high peel strength between the composite diaphragm layers in the industry, the PVDF layer is usually made in the form of a water-based coating during the preparation process, but at the expense of the gap between the composite diaphragm and the pole piece. The bond strength at the expense of

Method used

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  • A lithium battery composite separator and its preparation method and application
  • A lithium battery composite separator and its preparation method and application
  • A lithium battery composite separator and its preparation method and application

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0076] Embodiment 1 of the present invention is the preparation of a lithium battery composite diaphragm:

[0077] 1) Preparation of PVDF / ceramic hybrid slurry: Based on 100 parts by weight of the coatable slurry, 5 parts by weight of PVDF resin (3 parts by weight of PVDF resin with a weight average molecular weight of 800,000 to 1 million and 2 parts by weight of 200,000~500,000 PVDF resin), 2 parts by weight of emulsion-type acrylate adhesive dispersed in deionized water (solid content 40wt%, viscosity 20~200cps) and 7.5 parts by weight of Al 2 O 3 Particles (Dv50 of 0.64 μm) were added to a dimethylacetamide (DMAC) / water dispersion and dissolved at 50 °C for about 3 hours to form a mixed slurry of binders.

[0078] 2) Preparation of ceramic layer: use microgravure coating to coat the ceramic slurry on one side of the 7 μm base film, form a ceramic layer after drying, and obtain the ceramic film, that is, the traditional power lithium-ion battery separator (thickness 9 μm, ...

Embodiment 2

[0081] Embodiment 2 of the present invention is the preparation of a lithium battery composite separator:

[0082] 1) Preparation of PVDF / ceramic mixed slurry: Based on 100 parts by weight of the coatable slurry, 5 parts by weight of PVDF resin (2 parts by weight of PVDF resin with a weight average molecular weight of 800,000 to 1 million and 3 parts by weight of 200,000~500,000 PVDF resin), 2 parts by weight of emulsion-type acrylate adhesive dispersed in deionized water (solid content 40wt%, viscosity 20~200cps) and 7.5 parts by weight of Al 2 O 3 Particles (Dv50 of 0.64 μm) were added to a dimethylacetamide (DMAC) / water dispersion and dissolved at 50 °C for about 3 hours to form a mixed slurry of binders.

[0083] 2) Preparation of ceramic layer: use microgravure coating to coat the ceramic slurry on one side of the 7 μm base film, form a ceramic layer after drying, obtain a ceramic film (thickness 9 μm, puncture strength 366gf), a single layer of ceramic layer The coatin...

Embodiment 3

[0086] Embodiment 3 of the present invention is the preparation of a lithium battery composite separator:

[0087] 1) Preparation of PVDF / ceramic hybrid slurry: Based on 100 parts by weight of the coatable slurry, 4 parts by weight of PVDF resin and 2 parts by weight of emulsion-type acrylate adhesive (solid content 40wt) dispersed in deionized water %, viscosity 20~200cps) and 8 parts by weight of Al 2 O 3 Particles (Dv50 of 0.64 μm) were added to a dimethylacetamide (DMAC) / water dispersion and dissolved at 50 °C for about 3 hours to form a mixed slurry of binders.

[0088] 2) Preparation of ceramic layer: use microgravure coating to coat the ceramic slurry on one side of the 7 μm base film, form a ceramic layer after drying, obtain a ceramic film (thickness 9 μm, puncture strength 366gf), a single layer of ceramic layer The coating thickness is 2.0 μm.

[0089] 3) Preparation of composite diaphragm: under the conditions of 23 ° C and 20% relative humidity, the mixed slurr...

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Abstract

The invention provides a lithium battery composite separator and its preparation method and application. The lithium battery composite separator of the present invention includes a polymer base film, a ceramic layer and a porous gel layer. The porous gel layer includes inorganic ceramic particles, PVDF resin and acrylate adhesive. Any of the lithium battery composite separators The peeling force between the two interfaces is not less than 60N / m; compared with the existing technology, the present invention sets a porous gel layer mainly composed of PVDF resin, and adds inorganic ceramic particles and acrylic esters to the porous gel layer. The adhesive can not only improve the positive electrode bonding performance, thermal stability and ion conductivity of the composite separator, reduce the thermal shrinkage rate of the composite separator, but also effectively improve the peel strength between the layers of the composite separator and reduce the material cost of the composite separator. Composite separators have excellent comprehensive performance, which can improve the performance of lithium batteries.

Description

Technical field [0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium battery composite separator, a preparation method and a lithium battery using the same. Background technique [0002] The separator is an electrically insulating film with a porous structure. It is an important component of the secondary battery. It is mainly used to separate the positive electrode sheet and the negative electrode sheet to prevent internal short circuit of the secondary battery. Traditional separators mainly use polyolefin porous membranes, such as single-layer membranes or multi-layer composite membranes of polyethylene (PE) and polypropylene (PP). However, the polyolefin separator has a low melting point and will undergo severe thermal shrinkage when the temperature is too high. When the internal heat accumulates during the use of the secondary battery, the polyolefin separator is easily deformed and the positive and negative...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01M50/457H01M50/403H01M50/451H01M50/489H01M50/491H01M10/052H01M10/0525
CPCY02P70/50
Inventor 马平川刘杲珺张绪杰白耀宗高飞飞杜敬然甘珊珊孟颖翟萌萌李论周阳韩超魏明
Owner 中材锂膜(宁乡)有限公司
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