RETICULATED AND CONTROLLED POROSITY BATTERY STRUCTURES

• US 20080213662A1
• Filed: 03/03/2008
• Published: 09/04/2008
• Est. Priority Date: 10/20/2000
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Hellweg, Benjamin, Chiang, Yet-Ming
• Granted Patent: US 7,781,098 B2
• Time in Patent Office: Days
• US Class Current: 429/209
• 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 2004/025 with shapes other than plane or cylindrical
• CPC Class Codes: H01M 4/04 Processes of manufacture in general
• CPC Class Codes: H01M 4/0402 Methods of deposition of the material
• CPC Class Codes: H01M 4/0404 by coating on electrode collectors
• CPC Class Codes: H01M 4/0414 by screen printing
• CPC Class Codes: H01M 4/0416 involving impregnation with a solution, dispersion, paste or dry powder H01M4/0438 takes precedence
• CPC Class Codes: H01M 4/0421 involving vapour deposition
• CPC Class Codes: H01M 4/0423 Physical vapour deposition
• CPC Class Codes: H01M 4/0426 Sputtering
• CPC Class Codes: H01M 4/0428 Chemical vapour deposition
• CPC Class Codes: H01M 4/0471 involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• CPC Class Codes: H01M 4/0492 Chemical attack of the support material
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/139 Processes of manufacture
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The effective ionic conductivity in a composite structure is believed to decrease rapidly with volume fraction. A system, such as a bipolar device or energy storage device, has structures or components in which the diffusion length or path that electrodes or ions must traverse is minimized and the interfacial area exposed to the ions or electrons is maximized. The device includes components that can be reticulated or has a reticulated interface so that an interface area can be increased. The increased interfacial perimeter increases the available sites for reaction of ionic species. Many different reticulation patterns can be used. The aspect ratio of the reticulated features can be varied. Such bipolar devices can be fabricated by a variety of methods or procedures. A bipolar device having structures of reticulated interface can be tailored for the purposes of controlling and optimizing charge and discharge kinetics. A bipolar device having graded porosity structures can have improved transport properties because the diffusion controlling reaction kinetics can be modified. Graded porosity electrodes can be linearly or nonlinearly graded. A bipolar device having perforated structures also provides improved transport properties by removing tortuosity and reducing diffusion distance.

Claims

1. An electrode comprising a framework having an ionically interconnected porous network, wherein the porous network has a porosity density that varies from a first end to a second end.

2. The electrode of claim 1, wherein the porosity density is at least less than 10% from an average porosity density at the first end.

3. The electrode of claim 2, wherein the porosity density is at least greater than 10% from an average porosity density at the second end.

4. The electrode of claim 1, wherein the porosity density varies from the first end to the second end by more than about 5%.

5. An energy storage device, comprising:

a first electrode;

a second electrode;

a first current collector in electronic communication with the first electrode;

a second current collector in electronic communication with the second electrode; and

an electrolyte in ionic communication with the first and second electrodes, wherein at least one of the first and second electrodes includes a portion having an ionically interconnected porosity that increases in a direction from the current collector with which the electrode is in electrical communication toward the other electrode or current collector.

6. The energy storage device of claim 5, further comprising a porous separator separating the first electrode and second electrode, the liquid electrolyte permeating the separator and at least a portion of the porous portion of the first electrode.

7. The energy storage device of claim 5, wherein the first and second electrodes each include a porous portion adapted to receive the liquid electrolyte, each of the first and second electrodes having a porosity that increases in a direction toward the other electrode.

8. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porous portion with an average porosity of from about 10 to about 70%.

9. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porous portion with an average porosity of from about 20 to 50%.

10. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porous portion with an average porosity of from about 30 to 45%.

11. The energy storage device of claim 5, the first electrode having a porous portion with an average porosity and a porosity gradient in a direction from the first current collector toward the second electrode, wherein the porosity at each extreme of the gradient is at least 10% different from the average porosity.

12. The energy storage device of claim 5, at least one of the first and second electrodes having a porous portion with an average porosity and a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode, wherein the porosity at each extreme of the gradient is at least 20% different from the average porosity.

13. The energy storage device of claim 5, at least one of the first and second electrodes having a porous portion with an average porosity and a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode, wherein the porosity at each extreme of the gradient is at least 30% different from the average porosity.

14. The energy storage device of claim 5, wherein the porosity of any cross section of the first electrode perpendicular to a line connecting the center of mass of the current collector and the center of mass of the second electrode is uniform to ±

10%.

15. The energy storage device of claim 5, wherein the porosity of any cross section of the first electrode perpendicular to a line connecting the center of mass of the current collector and the center of mass of the second electrode is uniform to ±

5%.

16. The energy storage device of claim 5, wherein the porosity of any cross section of the first electrode perpendicular to a line connecting the center of mass of the current collector and the center of mass of the second electrode is uniform to ±

3%.

17. The energy storage device of claim 5, wherein the porosity of any cross section of the first electrode perpendicular to a line connecting the center of mass of the current collector and the center of mass of the second electrode is uniform to ±

1%.

18. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode that varies by no more than 5% at any location.

19. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode that varies by no more than 10% at any location.

20. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode that varies by no more than 15% at any location.

21. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode and the gradient is defined by a quadratic function.

22. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a porosity gradient in a direction from the current collector with which the electrode is in electrical communication toward the other electrode and the gradient is defined by a step function.

23. The energy storage device of claim 5, wherein at least one of the first and second electrodes has a reticulating surface defining a plurality of protrusions and intervening indentations, providing a surface area at least 1.5 times greater than the theoretical surface area of a smooth, non-reticulating configuration.