# US 2021/0280943 A1 · Method for preparing composite separator, composite separator, and lithium battery comprising composite separator

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- Number: US 2021/0280943 A1
- Document ID: US20210280943A1
- Status: Published application
- Kind: A1
- Application number: 17/195,437
- Filed: 2021-03-08
- Published: 2021-09-09
- Earliest claimed: 2020-03-09
- Assignees: Samsung SDI Co., Ltd.
- Applicants: Samsung SDI Co., Ltd.
- Inventors: Daehyun HONG
- Web page: https://patentgrep.com/patent/US20210280943A1

## CPC

- H01M 50/403: Manufacturing processes of separators, membranes or diaphragms
- H01M 10/052: Li-accumulators
- H01M 50/417: Polyolefins
- H01M 50/426: Fluorocarbon polymers
- H01M 50/434: Ceramics
- H01M 50/446: Composite material consisting of a mixture of organic and inorganic materials
- H01M 50/449: having a layered structure
- Y02E 60/10: Energy storage using batteries
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A method of preparing a composite separator for a lithium battery includes: coating a binder composition on one side or both sides of a porous substrate; hot-air drying the porous substrate coated with the binder composition; and supplying a non-solvent during the hot-air drying, such that a porous layer is on one side or both sides of the porous substrate, wherein the binder composition includes a good-solvent, a binder, and inorganic particles, an amount of the non-solvent supplied during the hot-air drying is from 12 g/m3 to 17 g/m3, and a ratio (e) of the hot-air supply speed to the moving speed of the porous substrate per unit transit time in the hot-air dryer is from 2.2 to 5.0.

## Claims

### Claim 1

A method of preparing a composite separator, the method comprising:
coating a binder composition on one side or both sides of a porous substrate;
hot-air drying the porous substrate coated with the binder composition; and
supplying a non-solvent during the hot-air drying,
wherein the composite separator comprises a porous layer on the one side or both sides of the porous substrate,
the binder composition comprises a good-solvent, a binder, and inorganic particles,
an amount of the non-solvent supplied during the hot-air drying is from 12 g/m3 to 17 g/m3, and
a ratio (e) represented by Equation 1 is from 2.2 to 5.0:
Ratio (e) of the hot-air supply speed to the moving speed of the porous substrate per unit transit time [s−1]=[hot-air supply speed/moving speed of porous substrate]/transit time of porous substrate in the hot-air dryer. Equation 1

### Claim 2 (depends on 1)

The method of claim 1, wherein the moving speed of the porous substrate is from 0.15 m/s to 0.45 m/s.

### Claim 3 (depends on 1)

The method of claim 1, wherein the hot-air supply speed is from 10 m/s to 50 m/s.

### Claim 4 (depends on 1)

The method of claim 1, wherein the hot-air drying is carried out at a temperature from 30° C. to 80° C.

### Claim 5 (depends on 1)

The method of claim 1, wherein the transit time of the porous substrate in the hot-air dryer is from 10 seconds to 50 seconds.

### Claim 6 (depends on 1)

The method of claim 1, wherein the non-solvent comprises at least one selected from water and alcohol.

### Claim 7 (depends on 1)

The method of claim 1, wherein the binder comprises a fluorine-based binder.

### Claim 8 (depends on 7)

The method of claim 7, wherein the fluorine-based binder comprises a vinylidene fluoride-hexafluoropropylene copolymer, and
the vinylidene fluoride-hexafluoropropylene copolymer has a glass transition temperature of −10° C. or lower and a melting point of 150° C. or higher.

### Claim 9 (depends on 8)

The method of claim 8, wherein the vinylidene fluoride-hexafluoropropylene copolymer has a weight average molecular weight of 700,000 to 1,200,000.

### Claim 10 (depends on 1)

The method of claim 1, wherein the inorganic particles comprise particles of at least one selected from alumina, titania, boehmite, and barium sulfate.

### Claim 11

A composite separator, the composite separator comprising:
a porous substrate; and
a porous layer formed on one side or both sides of the porous substrate,
wherein the porous layer comprises a fluorine-based binder and inorganic particles,
a ratio (a/b) of the number of pores having a diameter of 500 nm to 1000 nm per 1 μm2 of the porous layer (a) to the number of pores having a diameter less than 500 mm per 1 μm2 of the porous layer (b) is from 0.25 to 0.85,
an electrode assembly comprising a positive electrode, a negative electrode, and the composite separator interposed between the positive electrode and the negative electrode, wound in a jelly roll shape, has a bending strength of 460 N or more, and
the porous layer has a peel strength of 0.3 N/m or more with respect to the porous substrate.

### Claim 12 (depends on 11)

The composite separator of claim 11, wherein the bending strength is from 460 N to 550 N.

### Claim 13 (depends on 11)

The composite separator of claim 11, wherein the peel strength is from 0.3 N/m to 0.95 N/m.

### Claim 14 (depends on 11)

The composite separator of claim 11, wherein the porous layer comprises 0.3 to 0.4 pores having a diameter of 500 nm to 1000 nm per 1 μm2, and 0.5 to 1.5 pores having a diameter less than 500 nm per 1 μm2.

### Claim 15 (depends on 11)

The composite separator of claim 11, wherein the porous layer has a surface morphology in which a plurality of pores are discontinuously arranged on a polymer film in the form of islands.

### Claim 16 (depends on 11)

The composite separator of claim 11, wherein the fluorine-based binder comprises a vinylidene fluoride-hexafluoropropylene copolymer, and
the vinylidene fluoride-hexafluoropropylene copolymer has a glass transition temperature of −10° C. or lower and a melting point of 150° C. or higher.

### Claim 17 (depends on 16)

The composite separator of claim 16, wherein the vinylidene fluoride-hexafluoropropylene copolymer has a weight average molecular weight of 700,000 to 1,200,000.

### Claim 18 (depends on 11)

The composite separator of claim 11, wherein the inorganic particles comprise at least one selected from alumina, titania, boehmite, and barium sulfate.

### Claim 19 (depends on 11)

The composite separator of claim 11, wherein an amount of the inorganic particles is 90 wt % or less based on a total weight of the porous layer.

### Claim 20 (depends on 11)

A lithium battery, the lithium battery comprising:
an electrode assembly comprising:
a positive electrode;
a negative electrode; and
the composite separator according to claim 11 interposed between the positive electrode and the negative electrode,
wherein the electrode assembly is wound in a jelly roll shape.