Composite Heat Spreader and Battery Module Incorporating the Same

• US 20130216887A1
• Filed: 02/14/2013
• Published: 08/22/2013
• Est. Priority Date: 02/20/2012
• Status: Active Grant

• Current Assignee: NeoGraf Solutions, LLC
• Original Assignee: Graftech International Holdings Inc (Graftech International Limited)
• Inventors: Wayne, Ryan J., Taylor, Jonathan Andrew
• Granted Patent: US 9,797,664 B2
• Time in Patent Office: Days
• US Class Current: 429/120
• CPC Class Codes: F28F 21/02 of carbon, e.g. graphite
• CPC Class Codes: H01M 10/647 Prismatic or flat cells, e.g. pouch cells
• CPC Class Codes: H01M 10/6551 Surfaces specially adapted for heat dissipation or radiation, e.g. fins or coatings
• CPC Class Codes: H01M 10/6555 arranged between the cells
• CPC Class Codes: H01M 50/209 adapted for prismatic or rectangular cells H01M50/216 takes precedence
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A composite heat spreader includes a first flexible graphite layer, a second flexible graphite layer, and a gas evolving layer positioned between the first flexible graphite layer and the second flexible graphite layer. The gas evolving layer is temperature sensitive and when a threshold temperature is reached, the thermal conductivity of the gas evolving layer is reduced by at least factor of five.

Claims

1. A composite heat spreader comprising:

a first flexible graphite layer;

a second flexible graphite layer;

a gas evolving layer positioned between said first flexible graphite layer and said second flexible graphite layer; and

wherein when a threshold temperature is reached, the thermal conductivity of said gas evolving layer is reduced by at least factor of five.

2. The composite heat spreader according to claim 1 wherein said first and said second flexible graphite layer comprises a sheet of a compressed mass of exfoliated natural graphite particles.

3. The composite heat spreader according to claim 1 wherein said first and said second flexible graphite layer comprises a sheet of graphitized polyimide.

4. The composite heat spreader according to claim 1 wherein said first and said second flexible graphite layer have an in-plane thermal conductivity of from between about 250 W/mK and about 700 W/mK.

5. The composite heat spreader according to claim 1 wherein said first and said second flexible graphite layer have an in-plane thermal conductivity greater than at least about 400 W/mK.

6. The composite heat spreader according to claim 1 wherein said gas evolving layer comprises a hydrocarbon polymer.

7. The composite heat spreader according to claim 1 wherein said threshold temperature is at least about 95 degrees C.

8. The composite heat spreader according to claim 1 wherein said threshold temperature is at least about 150 degrees C.

9. The composite heat spreader according to claim 1 wherein after said threshold temperature is reached, the average thickness of said gas evolving layer increases by at least about 10 percent.

10. The composite heat spreader according to claim 1 wherein after said threshold temperature is reached, the average thickness of said gas evolving layer increases by at least about 50 percent.

11. The composite heat spreader according to claim 1 further comprising a containment shell.

12. The composite heat spreader according to claim 11 wherein said containment shell encapsulates said first flexible graphite layer, said second flexible graphite layer and said gas evolving layer.

13. A battery pack comprising:

a plurality of battery cells arranged in a stacked configuration, said battery cells each including opposed major surfaces;

at least one composite heat spreader positioned between two adjacent battery cells and contacting a major surface of each said adjacent battery cells;

said composite heat spreader comprising a first flexible graphite layer, a second flexible graphite layer;

a gas evolving layer positioned between said first flexible graphite layer and said second flexible graphite layer; and

wherein when a threshold temperature is reached, the thermal conductivity of said gas evolving layer is reduced by at least a factor of five.

14. The battery pack according to claim 13 wherein said first and said second flexible graphite layer comprises either a sheet of a compressed mass of exfoliated natural graphite particles or a sheet of graphitized polyimide.

15. The battery pack according to claim 13 wherein said first and said second flexible graphite layer have an in-plane thermal conductivity of at least about 250 W/mK.

16. The battery pack according to claim 13 wherein said gas evolving layer comprises a hydrocarbon polymer.

17. The battery pack according to claim 13 wherein said threshold temperature is at least about 95 degrees C.

18. The battery pack according to claim 13 wherein said threshold temperature is at least about 150 degrees C.

19. The battery pack according to claim 13 wherein after said threshold temperature is reached, the average thickness of said gas evolving layer increases by at least about 10 percent.

20. The battery pack according to claim 13 each said battery cell is electrically connected to an electrical system and wherein after said threshold temperature is reached at least one battery is electrically disconnected from said electrical system.

21. The battery pack according to claim 13 further comprising a containment shell that encapsulates said first flexible graphite layer, said second flexible graphite layer and said gas evolving layer.