Separator for Electricity Storage Device, Laminate and Porous Film

• US 20150188108A1
• Filed: 07/26/2013
• Published: 07/02/2015
• Est. Priority Date: 07/26/2012
• Status: Active Grant

• Current Assignee: Asahi Kasei E-materials Corporation (Asahi Kasei Corporation)
• Original Assignee: Asahi Kasei E-materials Corporation (Asahi Kasei Corporation)
• Inventors: Miyazawa, Hiroshi, Ameyama, Keitaro, Shuto, Takashi
• Granted Patent: US 10,153,473 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B32B 2457/10 Batteries
• CPC Class Codes: B32B 37/182 one or more of the layers being plastic
• CPC Class Codes: H01G 11/52 Separators
• CPC Class Codes: H01M 50/449 having a layered structure
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

An object is to provide a separator excellent in adhesiveness to electrodes and a separator for an electricity storage device also excellent in handling performance. A separator for an electricity storage device having a polyolefin microporous film and a thermoplastic polymer coating layer covering at least a part of at least one of surfaces of the polyolefin microporous film, in which the thermoplastic polymer coating layer, on the polyolefin microporous film, has a portion containing a thermoplastic polymer and a portion not containing the thermoplastic polymer in a sea-island configuration, the thermoplastic polymer coating layer contains the thermoplastic polymer having at least two glass-transition temperatures, at least one of the glass-transition temperatures is in a range of less than 20° C. and at least one of the glass-transition temperatures is in a range of 20° C. or more.

Claims

1. A separator for an electricity storage device comprising a polyolefin microporous film and a thermoplastic polymer coating layer covering at least a part of at least one of surfaces of the polyolefin microporous film, wherein

the thermoplastic polymer coating layer, on the polyolefin microporous film, has a portion containing a thermoplastic polymer and a portion not containing the thermoplastic polymer in a sea-island configuration,

the thermoplastic polymer coating layer contains the thermoplastic polymer having at least two glass-transition temperatures,

at least one of the glass-transition temperatures is in a range of less than 20°

C., and

at least one of the glass-transition temperatures is in a range of 20°

C. or more.

2. The separator for the electricity storage device according to claim 1, wherein, in the thermoplastic polymer coating layer,

a thermoplastic resin having a glass-transition temperature of 20°

C. or more is present on a side of a outermost surface of the separator for the electricity storage device, and

a thermoplastic resin having a glass-transition temperature of less than 20°

C. is present on a side of a interface between the polyolefin microporous film and the thermoplastic polymer coating layer.

3. The separator for the electricity storage device according to claim 1, wherein a peel strength of an aluminum foil after the aluminum foil is pressed at a temperature of 25°

C. and a pressure of 5 MPa for 3 minutes against the outermost surface of the separator for the electricity storage device having the thermoplastic polymer coating layer thereon is 8 gf/cm or less.

4. The separator for the electricity storage device according to claim 1, wherein a peel strength of an aluminum foil after the aluminum foil is pressed at a temperature of 80°

C. and a pressure of 10 MPa for 3 minutes against the outermost surface of the separator for the electricity storage device having the thermoplastic polymer coating layer thereon is 10 gf/cm or more.

5. The separator for the electricity storage device according to claim 1, wherein a 90°

peel strength of the polyolefin microporous film and the thermoplastic polymer coating layer is 6 gf/mm or more.

6. The separator for the electricity storage device according to claim 1, wherein, in the thermoplastic polymer coating layer, at least a part of the thermoplastic polymer present on the outermost surface of the separator for the electricity storage device is a particulate thermoplastic polymer.

7. The separator for the electricity storage device according to claim 6, wherein the particulate thermoplastic polymer has an average particle size of 0.01 μ

m to 0.4 μ

m.

8. The separator for the electricity storage device according to claim 1, wherein an area ratio of the polyolefin microporous film covered with the thermoplastic polymer coating layer is 95% or less based on 100% of a total area of the polyolefin microporous film.

9. The separator for the electricity storage device according to claim 1, wherein an area ratio of the polyolefin microporous film covered with the thermoplastic polymer coating layer is 50% or less based on 100% of the total area of the polyolefin microporous film.

10. A laminate formed by laminating the separator for the electricity storage device according to claim 1 and electrodes.

11. A porous film having a polyolefin microporous film and a thermoplastic polymer coating layer covering at least a part of at least one of surfaces of the polyolefin microporous film, wherein

the thermoplastic polymer coating layer contains a thermoplastic polymer having a glass-transition temperature in a range of −

10°

C. or more and 40°

C. or less, and

a degree of swelling of the thermoplastic polymer with an electrolytic solution of 5 times or less.

12. The porous film according to claim 11, wherein the thermoplastic polymer coating layer has an average thickness of 1.5 μ

m or less.

13. The porous film according to claim 11, wherein an area ratio of the polyolefin microporous film covered with the thermoplastic polymer coating layer is 70% or less based on 100% of a total area of the polyolefin microporous film.

14. The porous film according to claim 11, wherein the thermoplastic polymer has a gel fraction of 90% or more.

15. The porous film according to claim 11, wherein the thermoplastic polymer coating layer, on the polyolefin microporous film, has a portion containing the thermoplastic polymer and a portion not containing the thermoplastic polymer in a sea-island configuration, and

the portion containing the thermoplastic polymer is formed in a dot pattern.

16. The porous film according to claim 15, wherein the dot has an average major axis of 20 to 1000 μ

m.