Energy storage device having a separator blocking parasitic ions

• US 7,532,455 B2
• Filed: 04/14/2006
• Issued: 05/12/2009
• Est. Priority Date: 04/14/2006
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Maxwell Technologies Incorporated (Tesla Inc.)
• Inventors: Mitchell, Porter
• Primary Examiner(s): Ha; Nguyen T
• Application Number:
  US11/279,788
• Publication Number:
  US 20070242415A1
• Time in Patent Office: 1,124 Days
• Field of Search: 361/502, 361503-504, 361508-512, 361516-519, 361523-525, 361528-534
• US Class Current: 361/502
• CPC Class Codes: C08B 37/003 Chitin, i.e. 2-acetamido-2-deoxy-(beta-1,4)-D-glucan or N-acetyl-beta-1,4-D-glucosamine; Chitosan, i.e. deacetylated product of chitin or (beta-1,4)-D-glucosamine; Derivatives thereof
• CPC Class Codes: H01G 9/02 Diaphragms; Separators
• CPC Class Codes: H01G 9/145 Liquid electrolytic capacitors H01G11/00 takes precedence

Abstract

An energy storage device comprises a pair of electrodes in contact with an electrolyte and a dielectric separator therebetween. The separator comprises a chelating material capable of binding parasitic to ions with the electrolyte, so to prevent the free circulation of the parasitic ions within the electrolyte. In one embodiment, the chelating material comprises chitosan, which may be provided in fibrous form and which may be included within a non-woven fabric of cellulosic and/or olefinic, or which may be instead coated on the separator or otherwise comprised in the separator. In another embodiment, the chelating material comprises chitosan, and the ion-binding capability of the chitosan is enhanced by chemically binding a chelating agent to the chitosan so to create a multi-dentate ligand that binds with the parasitic ions, particularly multi-valent metal ions, to create coordination compounds. One such chelating agent is ethylendiamine tetraacetic acid (EDTA).

Claims

1. An energy storage device comprising:

a first electrode capable of storing a positive electrical charge;

a second electrode capable of storing a negative electrical charge;

a separator disposed between the first and the second electrodes, the separator creating a dielectric layer between the first and the second electrodes; and

an electrolyte contacting the first electrode, the second electrodes, and the separator and creating an ionic interface with the first and second electrodes,

wherein the separator comprises fibrous form chitosan capable of binding parasitic ions contained in the electrolyte, thereby preventing the free circulation of the parasitic ions within the electrolyte.

2. The energy storage device of claim 1, wherein the parasitic ions comprise metal ions.

3. The energy storage device of claim 1, wherein the chitosan is derived from the deacetylation of chitin.

4. The energy storage device of claim 1, wherein the chitosan is comprised within a non-woven fabric.

5. The energy storage device of claim 4, wherein the non-woven fabric further comprises one or more fibrous materials selected from the group consisting of cellulose and olefin.

6. The energy storage device of claim 4, wherein the non-woven fabric is sandwiched between layers of paper.

7. The energy storage device of claim 1, wherein the chitosan is coated on at least a portion of the dielectric layer.

13. The energy storage device of claim 1, wherein the energy storage device is a capacitor.

8. An energy storage device comprising:

a first electrode capable of storing a positive electrical charge;

a second electrode capable of storing a negative electrical charge;

a separator disposed between the first and the second electrodes, the separator creating a dielectric layer between the first and second electrodes; and

an electrolyte contacting the first electrode, the second electrodes, and the separator and creating an ionic interface with the first and second electrodes,

wherein the separator comprises chitosan capable of binding parasitic ions contained in the electrolyte, thereby preventing the free circulation of the parasitic ions within the electrolyte, wherein the ion-binding capability of the chitosan is enhanced by chemically binding a chealating agent with the chitosan.

9. The energy storage device of claim 8, wherein the chelating agent operates as a multi-dentate ligand.

10. The energy storage device of claim 8, wherein the chelating agent is ethylendiamine tetraacetic acid (EDTA).

11. The energy storage device of claim 10, wherein the EDTA is functionalized to a dianhydride form.

12. The energy storage device of claim 10, wherein the EDTA is ester-modified and cross-linked with cellulose.

14. The energy storage device of claim 8, wherein the energy storage device is a capacitor.