Carbonaceous material, polarizable electrode for electrical double-layer capacitor, and electrical double-layer capacitor

• US 6,574,092 B2
• Filed: 10/16/2001
• Issued: 06/03/2003
• Est. Priority Date: 10/16/2000
• Status: Expired due to Fees

• Current Assignee: Nisshinbo Industries, Inc. (Kawasaki Heavy Industries Limited)
• Original Assignee: Itochu Corporation, Nisshinbo Industries, Inc. (Kawasaki Heavy Industries Limited)
• Inventors: Minamiru, Shigenori, Mitsuhashi, Hideto, Shimizu, Tatsuo, Yoshida, Hiroshi, Sato, Takaya, Hashimoto, Zenzo
• Primary Examiner(s): Reichard, Dean A.
• Assistant Examiner(s): HA, NGUYEN T
• Application Number:
  US09/977,361
• Publication Number:
  US 20020126439A1
• Time in Patent Office: 595 Days
• Field of Search: 361/582, 361/503, 361/508, 361/523, 361/528, 361/512, 361/516, 361/509, 361/511, 361/504, 361/505, 361/303, 361/305, 361/327-330, 29/250.3
• US Class Current: 361/502
• CPC Class Codes: C01B 32/348 Metallic compounds
• CPC Class Codes: C01P 2004/61 Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/17 Pore diameter distribution
• CPC Class Codes: D01F 9/14 by decomposition of organic filaments
• CPC Class Codes: H01G 11/24 characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
• CPC Class Codes: H01G 11/34 characterised by carbonisation or activation of carbon
• CPC Class Codes: H01G 11/44 Raw materials therefor, e.g. resins or coal
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

A carbonaceous material having a pore size distribution, as determined from a nitrogen adsorption isotherm, in which pores with a radius of up to 10 Å account for at most 70% of the total pore volume, and having a specific surface area, as measured by the nitrogen adsorption BET method, of 1-500 m²/g is optimized for the penetration of non-aqueous electrolyte solution to the interior thereof and the surface adsorption of ionic molecules so as to form an electrical double layer thereon. Electrical double-layer capacitors assembled using polarizable electrodes made with the carbonaceous material have a high voltage, a high energy density, a high capacitance, a long cycle life, and are amenable to miniaturization.

Claims

1. A carbonaceous material having a pore size distribution, as determined from a nitrogen adsorption isotherm, in which pores with a radius of up to 10 Å

account for at most 70% of the total pore volume, and having a specific surface area, as measured by the nitrogen adsorption BET method, of 1 to 200 m²/g.

2. The carbonaceous material of claim 1 having a pore size distribution, as determined from a nitrogen adsorption isotherm, in which at least 50% of the pores with a radius greater than 10 Å

having a pore radius of 20 to 400 Å

.

3. The carbonaceous material of claim 1, which is prepared by subjecting a mesophase pitch-based carbon material, a polyacrylonitrile-based carbon material, a gas phase-grown carbon material, a rayon-based carbon material or a pitch-based carbon material to alkali activation with an alkali metal compound, then grinding the activated carbon material.

4. The carbonaceous material of claim 3 which is in the form of fine particles having a cumulative average particle size after grinding of at most 20 μ

m.

5. The carbonaceous material of claim 3 or 4 which is prepared by subjecting mesophase pitch-type carbon fibers to alkali activation, then grinding the activated fibers, and which is in the form of fine particles having a cumulative average particle size of at most 5 μ

m.

6. A polarizable electrode for electrical double-layer capacitors that is made by coating a current collector with an electrode composition containing a carbonaceous material according to claim 1 and a polymer binder, drying the applied coat, and press-forming;

which polarizable electrode has a density after drying of 0.6 to 1.2g/cm³.

7. A polarizable electrode for electrical double-layer capacitors that is made by coating a current collector with an electrode composition containing a carbonaceous material according to claim 1, a polymer binder and a conductive material, drying the applied coat, and press-forming;

which polarizable electrode has a density after 0.6 to 1.2 g/cm³.

8. The polarizable electrode of claim 6 or 7 which has a spontaneous potential with respect to lithium metal of at most 3.0 V.

9. The polarizable electrode of claim 6, wherein the polymer binder is a polymeric material having an interpenetrating network structure or a semi-interpenetrating network structure.

10. The polarizable electrode of claim 6, wherein the polymer binder is a fluoropolymer material.

11. The polarizable electrode of claim 6, wherein the polymer binder is a thermoplastic polyurethane-type polymeric material.

12. The polarizable electrode of claim 6 which is activated by carrying out at least one charge/discharge cycle at a potential at least 30% higher than the rated potential.

13. An electrical double-layer capacitor comprising:

a pair of polarizable electrodes,

a separator between the polarizable electrodes, and

an electrolyte solution;

wherein one or both of the pair of polarizable electrodes is a polarizable electrode according to claim 6.

14. The electrical double-layer capacitor of claim 13, wherein the electrolyte solution is a non-aqueous electrolyte solution.

15. The electrical double-layer capacitor of claim 13 or 14 which has a capacitance F₁ at a high current of 90 mA/cm² and a capacitance F₂ at a low current of 1.8 mA/cm², as measured by a constant current discharge method, such that the ratio F₂/F₁ is from 1 to 4.

16. An electrical double-layer capacitor comprising:

a pair of polarizable electrodes,

a separator between the polarizable electrodes, and

an electrolyte solution;

wherein the pair of polarizable electrodes are polarizable electrodes according to claim 6, and are activated by carrying out at least one charge/discharge cycle at a potential at least 30% higher than the rated potential.