Separator for Electrochemical Device, and Electrochemical Device

• US 20070264577A1
• Filed: 12/08/2005
• Published: 11/15/2007
• Est. Priority Date: 12/08/2004
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Maxell, Ltd.
• Inventors: Aoyama, Shigeo, Abe, Toshihiro, Katayama, Hideaki, Matsumoto, Nobuaki, Kita, Fusaji
• Granted Patent: US 11,050,095 B2
• Time in Patent Office: Days
• US Class Current: 429/246
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/4235 Safety or regulating additives or arrangements in electrodes, separators or electrolyte H01M10/4242 takes precedence
• CPC Class Codes: H01M 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 50/414 Synthetic resins, e.g. thermoplastics or thermosetting resins
• CPC Class Codes: H01M 50/429 Natural polymers
• CPC Class Codes: H01M 50/4295 Natural cotton, cellulose or wood
• CPC Class Codes: H01M 50/434 Ceramics
• CPC Class Codes: H01M 50/44 Fibrous material
• CPC Class Codes: 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
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An electrochemical device having excellent safety at high temperature is provided by using a separator for an electrochemical device, which is made of a porous film comprising: a porous base (5) having a heat-resistant temperature of 150° C. or higher and including filler particles (3); at least one kind of shutdown resin (6) selected from the group consisting of resin A that has a melting point in a range of 80° C. to 130° C. and resin B that absorbs an electrolyte and swells due to heating, and the swelling degree is increased as the temperature rises; and a binder (4).

Claims

1. A separator for an electrochemical device, comprising a porous film comprising a porous base and a resin, wherein

the porous base has a heat-resistant temperature of not lower than 150°

C. and comprises filler particles,

the resin is at least one kind of shutdown resin selected from the group consisting of resin A that has a melting point in a range of 80°

C. to 130°

C., and resin B that absorbs an electrolyte and swells due to heating, and the swelling degree is increased as the temperature rises.

2. The separator for an electrochemical device according to claim 1, wherein at least a part of the porous base is formed of the filler particles.

3. The separator for an electrochemical device according to claim 1, wherein the filler particles are contained in pores of the porous base.

4. The separator for an electrochemical device according to claim 1, wherein a shutdown occurs due to melting of the resin A or swelling of the resin B when at least heated at 130°

C. in a state wet with the electrolyte.

5. The separator for an electrochemical device according to claim 1, wherein the porous base is formed of a fibrous material having a heat-resistant temperature of not lower than 150°

C.

6. The separator for an electrochemical device according to claim 5, wherein the fibrous material is at least one selected from the group consisting of cellulose and a modification thereof, polyolefin, polyester, polyacrylonitrile, aramid, polyamideimide, polyimide, and an inorganic oxide.

7. The separator for an electrochemical device according to claim 5, wherein the fibrous material is a woven fabric or a nonwoven fabric.

8. The separator for an electrochemical device according to claim 1, wherein the shutdown resin is formed of fine particles.

9. The separator for an electrochemical device according to claim 1, wherein the shutdown resin is formed of fine particles and arranged together with the filler particles in the pores of the porous base.

10. The separator for an electrochemical device according to claim 1, wherein the resin A is at least one selected from the group consisting of polyethylene, an ethylene-vinyl monomer copolymer and a polyolefin wax.

11. The separator for an electrochemical device according to claim 1, wherein the resin B is a crosslinked resin having a glass transition temperature in a temperature range of 75°

C. to 125°

C.

12. The separator for an electrochemical device according to claim 11, wherein the crosslinked resin is at least one crosslinked body of resin selected from the group consisting of a styrene resin, a styrene-butadiene copolymer, an acrylic resin, polyalkylene oxide, a fluororesin and a derivative thereof.

13. The separator for an electrochemical device according to claim 1, wherein a swelling degree B_R of the resin B at 25°

C., which is expressed with the equation below, is not more than 2.5;

B_R=(V₀/V_i)−

1

where V₀ denotes the volume (cm³) of the resin B after being dipped in the electrolyte at 25°

C. for 24 hours, and V_i denotes the volume (cm³) of the resin B before being dipped in the electrolyte.

14. The separator for an electrochemical device according to claim 1, wherein the swelling degree B_T of the resin B at 120°

C., which is expressed with the equation below, is not less than 1;

B_T=(V₁/V₀)−

1

where V₀ denotes the volume (cm³) of the resin B after being dipped in the electrolyte at 25°

C. for 24 hours, and V₁ denotes the volume (cm³) of the resin B after being dipped in the electrolyte at 25°

C. for 24 hours, followed by steps of raising the temperature of the electrolyte to 120°

C. and keeping the electrolyte at 120°

C. for one hour.

15. The separator for an electrochemical device according to claim 1, wherein the filler particles are formed of an inorganic oxide.

16. The separator for an electrochemical device according to claim 15, wherein the inorganic oxide is at least one oxide selected from the group consisting of Al₂O₃, SiO₂ and boehmite.

17. The separator for an electrochemical device according to claim 1, wherein the filler particles are plate-like particles.

18. The separator for an electrochemical device according to claim 1, wherein air permeability expressed as a Gurley value is in a range of 10 to 300 (sec/100 mL).

19. An electrochemical device comprising a positive electrode, a negative electrode, a nonaqueous electrolyte and a separator,

wherein the separator is the separator for an electrochemical device according to claim 1.

20. The electrochemical device according to claim 19, wherein the separator is integrated with at least one selected from the group consisting of the positive electrode and the negative electrode.