Metal Ion Battery Safety Arrangement

Abstract

The present invention concerns a fire safety arrangement for a battery. More particularly, but not exclusively, this invention concerns a fire safety arrangement for a metal ion battery, for example a lithium ion battery cell. The metal ion battery cell comprises a plurality of electrodes and an electrolyte encased within a housing. The housing comprises a safety valve or vent to allow gas build up within the housing to vent outside the housing, and a fabric envelope surrounding the housing. Any sparks generated by the battery are contained within the fabric envelope, thereby reducing or eliminating the chances of fire or explosion.

Claims

1. A metal ion battery cell comprising a plurality of electrodes and an electrolyte encased within a housing, the housing comprising a safety valve or vent configured to allow gas build up within the housing to vent outside the housing, and a fabric envelope surrounding the housing, such that sparks generated by the battery are contained by the fabric envelope.

2. A metal ion battery cell as claimed in claim 1, comprising a lithium ion battery cell.

3. A metal ion battery cell as claimed in claim 1, wherein the lithium ion battery cell is a prismatic lithium ion battery cell.

4. A metal ion battery cell as claimed in claim 1, wherein the lithium ion battery cell is a cylindrical lithium ion battery cell.

5. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope fully surrounds the housing such that little or no oxygen is present between the housing and the envelope.

6. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope is gas permeable, to allow gas to pass from within the envelope to outside the envelope when the pressure within the envelope is greater than the pressure outside the envelope.

7. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope is such that when there is no pressure difference between the inside of the envelope and the outside of the envelope, little or no gas passes through the fabric envelope.

8. A metal ion battery cell as claimed in claim 1, wherein the safety valve is a one way valve arranged to open at 0.9 MPa, or 0.9 MPa±0.2 MPa pressure within the lithium ion battery cell.

9. A metal ion battery cell as claimed in claim 1, wherein the material of the fabric envelope allows gas to pass through the fabric when the pressure within the envelope is 0.9 MPa, or 0.9 MPa±0.2 MPa.

10. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope is elastically deformable.

11. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope comprises a heat resistant material.

12. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope comprises a felt material needled to or between one or more woven fabrics.

13. A metal ion battery cell as claimed in claim 1, wherein the fabric envelope comprises at least one connection port allowing wires to pass through the fabric envelope and connect to terminals of the lithium ion battery cell.

14. (canceled)

15. A method of manufacturing a metal ion battery cell according to claim 1, the method comprising the steps of: placing a metal ion battery cell in a fabric envelope, such that the housing of the metal ion battery cell is surrounded by the fabric envelope.

16. A power module, the power module comprising a plurality of metal ion battery cells, the plurality of metal ion battery cells encased within a housing, the housing comprising a safety valve or vent configured to allow gas build up within the housing to vent outside the housing, and a fabric envelope surrounding the housing, such that sparks generated by the battery cell are contained by the fabric envelope.

17. A battery pack, the battery pack comprising one or more power modules, each power module comprising a plurality of metal ion battery cells, the one or more power modules encased within a housing, the housing comprising a safety valve or vent configured to allow gas build up within the housing to vent outside the housing, and a fabric envelope surrounding the housing, such that sparks generated by the battery cell are contained by the fabric envelope.

Description

DESCRIPTION OF THE DRAWINGS

[0019] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0020] FIG. 1 shows a schematic cross-sectional view of a cell according to the prior art;

[0021] FIG. 2 shows a schematic cross sectional view of the cell of FIG. 1 where a fire has started;

[0022] FIG. 3 shows a schematic cross-sectional view of a cell according to a first embodiment of the invention,

[0023] FIG. 4 shows a schematic cross-sectional view of the cell shown in FIG. 3, with the fabric envelope expanded under pressure; and

[0024] FIG. 5 shows a method of manufacturing a battery cell according to an embodiment of the invention.

DETAILED DESCRIPTION

[0025] FIG. 1 shows a cross-sectional view of a metal ion battery cell, in this case a lithium ion prismatic cell 10. The cell comprises a plurality of electrodes and an electrolyte within a housing 12. Terminal connections 14 and 16 extend from the housing 12. A safety valve 18 is located on a top cover of the housing 12, and is arranged to vent gas from the housing 12 when the pressure reaches a threshold value to prevent undue pressure build up within the housing. A fault may increase the temperature within the cell 10, leading to a flammable gas being generated by the electrodes and electrolyte, which is vented through the safety valve 18 into an area proximate to the cell 10. This is shown by the cloud 20 shown in FIG. 1. As the temperature of the cell 10 rises, the exothermic reaction also increases, leading to further temperature rises. At some point, the temperature will rise to a level at which sparks 22 are generated within the cell 10 and pass through the safety valve. The sparks 22 may ignite the gas 20, leading to a fire 24 as shown in FIG. 2.

[0026] FIG. 3 shows a schematic cross-sectional view of a lithium ion prismatic cell 30. The cell 30 comprises a plurality of electrodes and an electrolyte 32 within a housing 34. Terminal connections 36 and 38 extend from the housing. A safety valve 40 is located on the top cover of the housing 34, and is arranged to vent gas from the housing 34 when the pressure reaches a threshold value. The cell 30 further comprises a fabric envelope 42 which surrounds the housing 34. The fabric envelope comprises a low silica felt needled between two silica fabrics, and is dense enough to absorb any sparks that are generated by the cell 30 and travel out through the safety valve 40. If a fault occurs which results in a flammable gas being generated, the flammable gas will pass through the safety valve 40 once the safety pressure within the cell 30 has been reached, and initially be contained within the fabric envelope 42. Any sparks that are generated and pass through the safety valve 40 will pass into the space between the housing 34 and the fabric envelope 42. This space, if any gas is present, will include little or no oxygen, and therefore there will be no fire or explosion caused by the spark prior to that spark being absorbed by the fabric envelope 42.

[0027] FIG. 4 shows the fabric envelope 42 where a gas build up has caused the expansion of the fabric envelope 42. Any sparks generated will continue to be contained within the fabric envelope 42, which continues to exclude oxygen from the space around the housing 34, and therefore no fire or explosion will result.

[0028] FIG. 5 shows a method of manufacturing a lithium ion battery cell 30 comprising provision of a fabric envelope 42 in step 50, and surrounding the housing 34 of the lithium ion battery cell 30 with the fabric envelope 42 in step 52.

[0029] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0030] In an alternative embodiment to that described above, the fabric envelope may comprise a safety valve arranged to vent gas build up between the housing of the battery cell and inside the envelope.

[0031] The lithium ion battery cell may be a cylindrical cell. The lithium ion battery cell may be a pouch cell. The invention may be applied to various other metal ion battery cells, in particular metal ion battery cells that potentially generate flammable gases.

[0032] The fabric envelope may be applied to cover a safety valve or vent in a housing of a power module, the power module comprising a plurality of metal ion battery cells. The fabric envelope may be applied to cover a safety valve or vent in a housing of a battery pack, the battery pack comprising a plurality of metal ion battery cells. The battery pack may comprise one or more power modules, each power module comprising a plurality of metal ion battery cells.

[0033] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.