Enhanced breakdown voltage electrode

• US 20070008677A1
• Filed: 07/08/2005
• Published: 01/11/2007
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Maxwell Technologies Incorporated (Tesla Inc.)
• Inventors: Xi, Xiaomei, Zhong, Linda
• Granted Patent: US 7,245,478 B2
• Time in Patent Office: Days
• US Class Current: 361/502
• CPC Class Codes: H01G 11/22 Electrodes
• CPC Class Codes: H01G 11/38 Carbon pastes or blends; Binders or additives therein
• CPC Class Codes: H01G 11/42 Powders or particles, e.g. composition thereof
• CPC Class Codes: H01M 4/0402 Methods of deposition of the material
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/1393 of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

Particles of active electrode material are made by blending and fibrillizing (i.e., fibrillating) a mixture of activated carbon, conductive carbon, and fibrillizable binder. In selected embodiments, chloride level in the activated carbon is relatively low, a small amount of conductive carbon with low impurity levels and high conductivity is used, and the binder is inert. For example, chloride content of the activated carbon is below 50 ppm, and total impurities in the conductive carbon are below 120 ppm. The mixture may include about 10% of PTFE and 0.5% or less of conductive carbon. Blending and fibrillization may be performed without solvents. The fibrillized particles are dried, blended again to reduce clumping, and used to make active electrode material film. The film is attached to a current collector to obtain an electrode for use in various electrical devices, including double layer capacitors. The electrode increases breakdown voltage of the capacitor electrolyte.

Claims

1. A method of making particles of active electrode material, the method comprising:

providing activated carbon with chloride content not exceeding about 50 parts per million;

providing binder;

mixing the activated carbon and the binder to obtain a mixture; and

fibrillizing the binder in the mixture.

2. A method in accordance with claim 1, further comprising providing conductive particles.

3. A method in accordance with claim 2, wherein proportion of the conductive carbon particles in the mixture does not exceed about 0.5 percent by weight.

4. A method in accordance with claim 1, wherein the binder comprises PTFE;

and wherein the proportion of the binder in the mixture is about 10 percent by weight.

5. A method in accordance with claim 2, wherein the proportion of the conductive carbon particles in the mixture is between 0.1 percent and 1 percent by weight;

and wherein the proportion of binder in the mixture is between 9 and 11 percent by weight.

6. A method in accordance with claim 2, wherein the step of mixing comprises dry blending the activated carbon, conductive carbon, and the binder.

7. A method in in accordance with claim 1, wherein the step of fibrillizing is performed without processing additives.

8. An electrode comprising:

a current collector; and

a film of active electrode material attached to the current collector, wherein the active electrode material comprises particles of activated carbon with a chlorine content of less than about 50 ppm; and

wherein the active electrode material further comprises conductive carbon particles, and wherein the proportion of the conductive carbon particles in the active electrode material is between about 0.1 percent and about 1.0 percent by weight.

9. The electrode of claim 8, wherein the active electrode material comprises binder, wherein the proportion of binder in the active electrode material is between 9 and 11 percent by weighting.

10. The electrode of claim 9, wherein the proportion of the conductive carbon particles in the active electrode material is between about 0.1 percent and about 0.5 percent by weight.

11. The electrode of claim 8, wherein the chlorine content of the activated carbon is less than about 30 ppm chlorine.

12. A method of making particles of active electrode material, the method comprising:

providing activated carbon with chloride content not exceeding about 50 parts per million;

providing low contamination level conductive particles;

providing fibril-forming binds;

mixing the activated carbon, the conductive carbon, and the binder to obtain a mixture; and

fibrillizing the mixture.

13. A method in accordance with claim 12, wherein proportion of the conductive carbon particles in the mixture does not exceed about 0.5 percent by weight.

14. A method in accordance with claim 13, wherein proportion of the binder in the mixture is about 10 percent by weight.

15. A method in accordance with claim 13, wherein proportion of binder in the mixture is between 9 and 11 percent by weight.

16. A method in accordance with claim 12 wherein the step of providing activated carbon comprises providing activated carbon with chloride content less than about 30 parts per million.

17. An eletrochemical double layer capacitor comprising:

a first electrode comprising a first current collector and a first film of active electrode material, the first film comprising a first surface and a second surface, the first current collector being attached to the first surface of the first film;

a second electrode comprising a second current collector and a second film of active electrode material, the second film comprising a third surface and a fourth surface, the second current collector being;

at ached to the third surface of the second film;

a porous separator disposed between the second surface of the first film and the fourth surface of the second film;

a container;

an electrolyte;

wherein;

the first electrode, the second electrode, the porous separator, and the electrolyte are disposed in the container;

the first film is at least partially immersed in the electrolyte;

the second film is at least partially immersed in the electrolyte;

the porous separator is at least partially immersed in the electrolyte;

each of the first and second films comprises a mixture of activated carbon with chlorine content not exceeding about 50 parts per million; and

wherein the mixture of each of the first and second films further comprises conductive carbon particles, and wherein the amount of the conductive carbon particles is between about 0.1 percent and about 0.5 percent by weight.

18. The capacitor of claim 17, wherein the proportion of the conductive carbon in the mixture is less than about 0.5 percent by weight.

19. The capacitor of claim 18, wherein the electrode films further comprise binder, wherein the proportion of binder in the mixture is between about 9 percent and 11 percent by weight.

20. The capacitor of claim 17, wherein the films are attached to respective collectors via a conductive adhesive layer.