# US 2014/0193692 A1 · Multilayer porous film, separator for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery

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- Number: US 2014/0193692 A1
- Document ID: US20140193692A1
- Status: Published application
- Kind: A1
- Application number: 14/236,010
- Filed: 2013-03-15
- Published: 2014-07-10
- Earliest claimed: 2012-03-26
- Assignees: Mitsubishi Plastics, Inc.
- Applicants: Mitsubishi Plastics, Inc.
- Inventors: Hiroto Yamada; Tomoyuki Nemoto
- Web page: https://patentgrep.com/patent/US20140193692A1

## CPC

- B32B 27/32: comprising polyolefins {(comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30)}
- B32B 27/08: of synthetic resin
- B32B 27/20: using fillers, pigments, thixotroping agents
- H01M 10/4235: {Safety or regulating additives or arrangements in electrodes, separators or electrolyte (H01M10/4242 takes precedence)}
- H01M 50/417: Polyolefins
- H01M 50/42: Acrylic resins
- H01M 50/426: Fluorocarbon polymers
- H01M 50/429: Natural polymers
- H01M 50/4295: {Natural cotton, cellulose or wood}
- H01M 50/434: Ceramics
- H01M 50/44: Fibrous material
- H01M 50/449: having a layered structure
- H01M 50/451: comprising layers of only organic material and layers containing inorganic material
- H01M 50/491: Porosity
- H01M 10/052: Li-accumulators
- Y02E 60/10: Energy storage using batteries
- Y10T 428/249991: Synthetic resin or natural rubbers
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- 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
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Provided is a multilayer porous film that has extremely high powder fall-off resistance and superior electrolyte solution adsorptivity and heat resistance and exhibits superior properties when used as a battery separator without decreasing the high air permeability of a porous film. The multilayer porous film includes a polyolefin-based resin porous film and a coating layer containing a filler and a resin binder on at least one surface of the polyolefin-based resin porous film. The amount of particles with particle sizes of less than 0.2 μm (D0.2) in the filler is 1% or more, and the specific surface area of the filler is 5 m2/g or more and less than 10 m2/g. The multilayer porous film satisfies a particular condition.

## Claims

### Claim 1

A multilayer porous film comprising:
a polyolefin-based resin porous film, and
a coating layer comprising a filler and a resin binder on at least one surface of the polyolefin-based resin porous film,
wherein an amount of particles with particle sizes of less than 0.2 μm (D0.2) in the filler is 1% or more,
wherein a specific surface area of the filler is 5 m2/g or more and less than 10 m2/g, and
wherein the multilayer porous film satisfies a condition (1):
condition (1). after the multilayer porous film is cut to a size of 50 mm×50 mm and is stuck on thick paper in a state where the coating layer faces upward, a column-shaped weight having a diameter of 40 mm and a weight of 700 g and covered with a cotton cloth on an entire bottom surface thereof is placed on the coating layer, and the weight is rotated at a rotational speed of 50 rpm for 10 minutes to rub the surface of the coating layer, observation of the surface of the coating layer shows that the coating layer has a missing portion with an area of less than 10% of a contact area of the weight.

### Claim 2 (depends on 1)

The multilayer porous film of claim 1, wherein the filler comprises a metal oxide.

### Claim 3 (depends on 1)

The multilayer porous film of claim 1, wherein the resin binder is at least one selected from the group consisting of polyvinyl alcohol, polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, and a polyacrylic acid derivative.

### Claim 4 (depends on 1)

The multilayer porous film of claim 1, wherein a content of the filler to a total amount of filler and resin binder in the coating layer is from 80% to 99.9% by mass.

### Claim 5 (depends on 1)

The multilayer porous film of claim 1, wherein the polyolefin-based resin porous film comprises a polypropylene-based resin.

### Claim 6 (depends on 1)

The multilayer porous film of claim 1, wherein the polyolefin-based resin porous film has β-crystal activity.

### Claim 7 (depends on 1)

The multilayer porous film of claim 1, wherein the coating layer is formed on the polyolefin-based resin porous film by a method comprising applying a dispersion to the polyolefin-based resin porous film.

### Claim 8 (depends on 7)

The multilayer porous film of claim 7, wherein a dispersion medium in the dispersion comprises water as a major component.

### Claim 9 (depends on 1)

A separator comprising the multilayer porous film of claim 1.

### Claim 10 (depends on 9)

A nonaqueous electrolyte secondary battery comprising the separator of claim 9.

### Claim 11 (depends on 2)

The multilayer porous film of claim 2, wherein the resin binder is at least one selected from the group consisting of polyvinyl alcohol, polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, and a polyacrylic acid derivative.

### Claim 12 (depends on 2)

The multilayer porous film of claim 2, wherein a content of the filler to a total amount of filler and resin binder in the coating layer is from 80% to 99.9% by mass.

### Claim 13 (depends on 3)

The multilayer porous film of claim 3, wherein a content of the filler to a total amount of filler and resin binder in the coating layer is from 80% to 99.9% by mass.

### Claim 14 (depends on 11)

The multilayer porous film of claim 11, wherein a content of the filler to a total amount of filler and resin binder in the coating layer is from 80% to 99.9% by mass.

### Claim 15 (depends on 2)

The multilayer porous film of claim 2, wherein the polyolefin-based resin porous film comprises a polypropylene-based resin.

### Claim 16 (depends on 3)

The multilayer porous film of claim 3, wherein the polyolefin-based resin porous film comprises a polypropylene-based resin.

### Claim 17 (depends on 4)

The multilayer porous film of claim 4, wherein the polyolefin-based resin porous film comprises a polypropylene-based resin.