# US 2013/0280616 A1 · Porous membrane and process for preparing the same

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2013/0280616 A1
- Document ID: US20130280616A1
- Status: Published application
- Kind: A1
- Application number: 13/978,352
- Filed: 2012-10-12
- Published: 2013-10-24
- Earliest claimed: 2011-10-13
- Assignees: Tokushu Tokai Paper Co., Ltd.
- Inventors: Yoshiharu Machii; Satoshi Nemoto; Yohta Mori
- Web page: https://patentgrep.com/patent/US20130280616A1

## CPC

- H01G 11/52: Separators
- H01G 9/004: Details
- H01G 9/02: Diaphragms; Separators
- H01M 50/403: Manufacturing processes of separators, membranes or diaphragms
- H01M 50/4295: {Natural cotton, cellulose or wood}
- H01M 50/44: Fibrous material
- H01M 50/489: Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M 50/491: Porosity
- H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
- Y02E 60/10: Energy storage using batteries
- Y02E 60/13: Energy storage using capacitors
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- 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
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

The present invention relates to a porous membrane containing cellulose fibers, wherein the cellulose fibers contain 5% by weight or more of cellulose fibers with a diameter of 1 μm or more, relative to the total weight of the cellulose fibers, the mode diameter (maximal frequency) of the pore distribution determined by the mercury penetration method is less than 0.3 μm, the air resistance per thickness of 10 μm is from 20 to 600 seconds, and the porous membrane has a volume resistivity of 1500 Ω·cm or less determined by alternate current with a frequency of 20 kHz in which the porous membrane is impregnated with 1 mol/LiPF6/propylene carbonate solution. The porous membrane according to the present invention can provide a separator for electrochemical devices with superior properties at a reasonable cost.

## Claims

### Claim 1

A porous membrane comprising cellulose fibers, wherein
said cellulose fibers comprise cellulose fibers with a diameter of 1 μm or more in an amount of 5% by weight or more based on the total weight of said cellulose fibers,
a mode diameter (maximal frequency) of a pore distribution determined by a mercury penetration method is less than 0.3 μm,
an air resistance per thickness of 10 μm ranges from 20 to 600 seconds, and
said porous membrane has a volume resistivity of 1500 Ω·cm or less determined by alternate current with a frequency of 20 kHz in which said porous membrane is impregnated with a 1 mol/LiPF6/propylene carbonate solution.

### Claim 2 (depends on 1)

The porous membrane according to claim 1, which has a porosity ranging from 30 to 70%.

### Claim 3 (depends on 1)

The porous membrane according to claim 1, which has an air resistance per thickness of 10 μm ranging from 30 seconds to 250 seconds.

### Claim 4 (depends on 1)

The porous membrane according to claim 1, which is obtained from a slurry containing a hydrophilic pore former together with said cellulose fibers.

### Claim 5 (depends on 4)

The porous membrane according to claim 4, wherein said hydrophilic pore former has a solubility with respect to water of 10% by weight or more.

### Claim 6 (depends on 4)

The porous membrane according to claim 4, wherein said hydrophilic pore former has a vapor pressure at 25° C. which is less than 0.1 kPa.

### Claim 7 (depends on 4)

The porous membrane according to claim 4, wherein a water-octanol partition coefficient of said hydrophilic pore former ranges from −1.2 to 0.8.

### Claim 8 (depends on 4)

The porous membrane according to claim 4, wherein said hydrophilic pore former is a glycol ether.

### Claim 9 (depends on 4)

The porous membrane according to claim 4, wherein said slurry contains a hydrophilic polymer binder in an amount ranging from 3 to 80 parts by weight with respect to 100 parts by weight of said cellulose fibers.

### Claim 10 (depends on 1)

A separator for an electrochemical device comprising the porous membrane as recited in claim 1.

### Claim 11 (depends on 10)

An electrochemical device comprising the separator for an electrochemical device as recited in claim 10.

### Claim 12 (depends on 11)

The electrochemical device according to claim 11, which is a battery or a capacitor.

### Claim 13

A process for preparing a porous membrane formed from cellulose comprising the steps of:
applying a slurry including at least a hydrophilic pore former and cellulose fibers comprising cellulose fibers with a diameter of 1 μm or more, in an amount of 5% by weight or more based on the total weight of said cellulose fibers, onto a substrate;
drying said slurry to form a sheet on said substrate; and
separating said sheet from said substrate to obtain a cellulose porous membrane formed from said sheet.

### Claim 14 (depends on 13)

The process for preparing a porous membrane according to claim 13, further comprising a step of cleaning said sheet or said porous membrane with an organic solvent.