BATTERY CELL WITH INTERNAL SWELLING RELIEF AND EXTERNAL COOLING FEATURES

Abstract

A battery cell including an electrode assembly contained within a housing. The electrode assembly shrinks and/or swells depending on a charge/discharge cycle of the cell. A swelling compensation member configured to shrink upon swelling of the electrode assembly, and expand upon on shrinking of the electrode assembly is in continuous contact with the electrode assembly and an innermost surface of the housing. A first portion of the innermost surface of the housing is in contact with the swelling compensation member, and a second portion is free from contact with the swelling compensation member. The battery cell includes a cooling member in thermal contact with the outermost surface of the housing. Part of the outermost surface of the housing in contact with the cooling member corresponds to a part of the innermost surface of the housing which is free from contact with the swelling compensation member.

Claims

1. A battery comprising a cell assembly comprising: an electrode assembly and an electrolyte, a housing containing the cell assembly, a battery comprising a swelling compensation member, and a cooling member in thermal contact with the outermost surface of the housing; wherein the swelling compensation member is configured to be in contact with the electrode assembly and an innermost surface of the housing, such that a first portion of the innermost surface of the housing is in contact with the swelling compensation member, and a second portion of the innermost surface of the housing is free from contact with the swelling compensation member, and wherein at least a part of the outermost surface of the housing in contact with the cooling member corresponds to at least part of the innermost surface of the housing which is free from contact with the swelling compensation member.

2. The battery cell as claimed in claim 1, wherein the swelling compensation member comprises a material having an at least semi-open porous structure, and wherein, in use, the swelling compensation member is configured to shrink in at least one dimension upon swelling of the electrode assembly, and to expand in at least one dimension upon on shrinking of the electrode assembly.

3. The battery cell as claimed in claim 2, wherein the pores of the swelling compensation member contain electrolyte for use in the battery cell.

4. The battery cell as claimed in claim 1, comprising one or more swelling compensation members.

5. The battery cell as claimed in claim 1, wherein the housing comprises a flexible pouch material or a substantially rigid material.

6. The battery cell as claimed in claim 1, wherein the housing is substantially cuboid in form such that the housing comprises three pairs of substantially opposing side walls which pairs are substantially normal to one another, wherein the cooling member is substantially parallel to a first pair of side walls, and wherein the swelling compensation member is substantially parallel to a second or a third pair of side walls.

7. A battery comprising a plurality of the battery cells as claimed in claim 6, wherein two or more battery cells are arranged side by side and share a common cooling member.

8. The battery as claimed in claim 7, wherein the cooling member comprises one or more cooling fins located between first and second neighbouring cells, wherein each cooling fin is in thermal contact with a second side face of the first cell and a second side face of the second cell, wherein the second side faces of the first and second cells in contact with the cooling fin(s) are cooling side faces of the first and second cells respectively.

9. The battery as claimed in claim 8, wherein the innermost surface of the cooling side face of the first cell, and the innermost surface of the cooling side face of the second cell are free from contact with the respective swelling compensation member of the first and second cells.

10. The battery as claimed in claim 9, comprising a third battery cell located side by side and neighbouring with the second battery cell such that a second side face of the third cell is adjacent to a second side face of the second cell, wherein the adjacent side faces of the second and third cells are insulating side faces of the second and third cells respectively, wherein the innermost surface of the insulating side face of the third cell and the innermost surface of the insulating side face of the second cell are in contact with the respective swelling compensation member of the second and third cells.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will now be described by way of non-limiting examples with reference to the following figures, in which:

[0030] FIG. 1 shows a schematic cross-section of a battery cell having internal swelling relief;

[0031] FIG. 2 shows a schematic end view of a “jelly-roll” type electrode assembly;

[0032] FIG. 3 shows a schematic cross-section of a battery comprising a plurality of the battery cells;

[0033] FIG. 4 shows a schematic view of a battery cell housing; and

[0034] FIG. 5 shows a schematic cross-section of an alternative battery configuration comprising a plurality of the battery cells.

DETAILED DESCRIPTION

[0035] A schematic cross-sectional illustration of a battery cell 10 is shown in FIG. 1. The battery cell 10 comprises a housing 12 within which is located an electrode assembly 20. The electrode assembly 20 comprises a first electrode 22 and a second electrode 24 separated from one another by a separator 26.

[0036] As is well-known in battery technology, the first and second electrodes 22, 24 comprise electrical conductors of differing electrode potential. A suitable electrolyte (not shown) is located within the housing 12. Typically the electrolyte comprises a liquid or a gel and resides within the separator 26 which has an open porous structure. For example, the separator 26 may comprise a porous solid or woven material. Typical secondary battery cells chemistries include lithium-metal and lithium-ion cells as is well known in the art.

[0037] The first and second electrodes 22, 24, and the separator 26, typically have a thin film type construction. In the example shown in FIG. 1, the electrode assembly 20 is shown as a stack of layers comprising a single first electrode 22 (for example a cathode), a single second electrode 24 (for example an anode) and a single layer of separator material 26. Each electrode 22, 24 is attached to an electrical connection tab 16 (for example by an ultrasonic or spot weld) which lead to external electrical contacts 14 located on the outside of the housing 12. When the external electrical contacts 14 are connected in a circuit, ions flow from one electrode to the other through the electrolyte to provide electrical power to the circuit and an electrical device attached thereto. To charge the battery cell, the flow of electrical current is reversed.

[0038] As described above, the configuration of the electrode assembly 20 shown in FIG. 1 comprises two electrodes 22, 24 separated by a single separator 26. However, it will be understood that this is a simplified example only and that other electrode assembly configurations are possible. For example, the electrode assembly 20 may comprise a plurality of first electrodes 22 and a corresponding plurality of second electrodes 24, each separated by a separator layer 26 in a multi-electrode, multi-separator stack. In this case, each of the plurality of electrodes 22, 24 has an electrical connection tab 16 leading from the electrode to the corresponding external electrical contact 14. Alternatively or additionally, the electrode assembly 20 may be rolled up to form a generally cylindrical electrode assembly. Such an assembly would typically be located in a cylindrical housing to form a cylindrical battery cell. Another common electrode assembly configuration is a “jelly-roll” in which the thin film stack (or stacks) is rolled in a flattened spiral as illustrated schematically in FIG. 2. A “jelly-roll” electrode assembly is typically, although not exclusively, used in pouch cell batteries.

[0039] Referring once again to FIG. 1, the battery cell 12 also comprises a swelling compensation member 30 located between the electrode assembly 20 and the inner surface 11 of the housing 12. The swelling compensation member 30 comprises a resilient material and is configured to be in continuous contact with the electrode assembly 20. Example materials include foams, sponge like materials, and woven materials. The resilient behaviour of the swelling compensation member 30 need not be linear.

[0040] As discussed above, in use, during charging/discharging of the battery cell 10, the electrode assembly 20 may swell or shrink. In the example shown in FIG. 1, the swelling/shrinking is generally in a direction Y normal to the electrode assembly 20. The swelling compensation member 30 is configured to shrink in the Y direction upon swelling of the electrode assembly 20 and to expand in the Y direction upon shrinking of the electrode assembly 20. In other embodiments, the electrode assembly 20 may swell in one or more other directions in addition to, or instead of, the Y direction shown in FIG. 1. The swelling compensation member 30 can be configured to expand/shrink in any direction as necessitated by the particular electrode assembly 20 swell/shrink characteristic.

[0041] The swelling compensation member 30 may be attached to the electrode assembly 20 and/or to the inner surface 11 of the housing 12 by mechanical fasteners and/or adhesive. Alternatively, the swelling compensation member 30 may simply be located between the electrode assembly 20 and/or the inner surface 11 of the housing 12 without physical attachment to either. The swelling compensation member 30 may be under compression in all swelling conditions of the electrode assembly 20 such that it is substantially held in place between the electrode assembly 20 and the inner surface 11 of the housing 12 by the resilient restoring force as the swelling compensation member 30 seeks to regain its uncompressed form. A biasing member (not shown) may be provided to bias the swelling compensation 30 member towards the housing 12 and/or electrode assembly 20.

[0042] Because the swelling compensation member 30 is configured to shrink upon swelling of the electrode assembly 20, and to expand upon shrinking of the electrode assembly 20, the external dimensions of the battery cell housing 12 can be protected from dimensional change caused by the swelling/shrinking of the electrode assembly 20 since dimensional change of the electrode assembly is taken up by the swelling compensation member 30.

[0043] In the example described above, a swelling compensation member 30 is only provided on one side of the electrode assembly 20. However, it will be understood that more than one swelling compensation member 30 may be provided and may be located between any part of the electrode assembly 20 and the inner surface 11 of the battery cell housing 12 as required. Alternatively or additionally, one or more swelling compensation members 30 may be provided within the electrode assembly 20. For example, within an electrode stack (between electrode pairings), or within a rolled electrode assembly. The swelling compensation member 30 may comprise one continuous member which partially or substantially fully surrounds the electrode assembly 20. Furthermore, it will be understood that the electrode assembly 20 may have any suitable configuration such as stacked, rolled or jelly-rolled, and that the housing 12 may be rigid or a flexible pouch, and may have any suitable form such as cuboid, rounded-cuboid or cylindrical.

[0044] In one example, the swelling compensation member 30 comprises a resilient material having an open porous structure capable of containing the electrolyte of the battery cell. In such an example, the electrolyte is able to move from the pores of the swelling compensation member 30 to the separator 26, and vice versa, as the swelling compensation member shrinks and expands in use. If the battery cell 10 should lose electrolyte over the course of its life due to oxidation, the electrolyte contained in the swelling compensation member 30 can replace the lost electrolyte thereby extending the life of the battery cell 10.

[0045] A suitable material for the swelling compensation member 30 is ethylene propylene diene monomer (EPDM) foam having a semi-open porous structure in which some of the pores have a closed structure and some of the pores have an open interconnected structure. Sponges or foams having a semi-open porous structure such as this are useful as the elastic behaviour of the closed pores help to maintain dimensional stability and electrode assembly compression during swelling and shrinking of the electrode assembly 20, and the open interconnected pores are suited to containing and dispensing the electrolyte during the life of the battery cell 10.

[0046] FIG. 3 shows a schematic cross-sectional illustration of a battery 40 comprising a plurality of battery cells 10. For reasons of consistency, the same reference numerals as used above are used throughout the description to indicate like features.

[0047] The battery 40 comprises six battery cells 10 arranged side by side. For reasons of clarity, the electrode assemblies 20 are shown in outline only. It will be understood that the electrode assemblies 20 could be configured in any suitable manner as discussed above.

[0048] Each battery cell 10 comprises a housing 12 (FIG. 4) of generally rounded cuboid form having a first pair of substantially opposing first side faces 41, 42 which are substantially parallel to a first plane, a second pair of substantially opposing second side faces 43, 44 which are substantially parallel to a second plane, and a third pair of substantially opposing third side faces 45, 46 which are substantially parallel to a third plane, wherein the first, second and third planes are substantially normal to one another.

[0049] With reference to the orientation of FIG. 3, the first pair of side faces 41, 42 respectively form the top and bottom of the battery cells 10, the second pair of side faces 43, 44 respectively form the left and right of the battery cells 10, and the third pair of side faces 45, 46 respectively form the front and back of the battery cells 10. Each battery cell 10 comprises a layer of swelling compensation member material 30 located between the electrode assembly 20 and the inner surface 11 of the left side face (with respect to FIG. 3) of the housing 12.

[0050] A cooling member 60 in the form of a metal (or other thermally conductive material) plate is in thermal contact with the bottom faces of the battery cells 10. The cooling member 60 may be attached to the bottom faces of the battery cells 10 by mechanical fasteners and/or by adhesive. An outer housing 50 surrounds the battery cells 10 and cooling member 60.

[0051] Heat developed in the battery cells 10 during charging and discharging is removed from the battery cells via thermal conduction to the cooling member 60. The cooling member 60 may be cooled by a fan or other cooling system (not shown).

[0052] The cooling member 60 need not be in direct physical contact with the bottom of the battery cells 10 provided that it is in thermal contact with the battery cells 10. If desired, any suitable thermally conductive material may be placed between the cooling member 60 and the battery cells 10. Furthermore, it will be appreciated that the cooling member 60 may alternatively or additionally be in contact with any other faces of the battery cells 10 such as the top faces, front faces or back faces. Additionally, it will be appreciated that the battery 40 may comprise more than one cooling member 60.

[0053] The thermal compensation members 30 of the battery cells 10 of the battery 40 provide thermal insulation between the adjacent battery cells 10 to help prevent thermal run away of the entire battery 40 in the event that one of the battery cells 10 experiences thermal run-away.

[0054] FIG. 5 shows an alternative battery configuration 70 comprising six battery cells 10a-f and a cooling member 60 located in an outer housing 50. In the battery configuration 70 of FIG. 5 the cooling member 60 comprises a plurality of fins 62a, 62b, 62c located respectively between, and in thermal contact with, the first and second battery cells 10a, 10b, third and fourth battery cells 10c, 10d, and fourth and fifth battery cells 10e, 10f.

[0055] Referring to the orientation of FIG. 5, the swelling compensation members 30 of the first 10a, third 10c, and fifth 10e battery cells are located between the electrode assemblies 20 and the inner surfaces 11 of the left side faces of the housings 12, and the swelling compensation members 30 of the second 10b, fourth 10d, and sixth 10f battery cells are located between the electrode assemblies 20 and the inner surfaces 11 of the right side faces of the housings 12. In this example, the side faces 43, 44 in contact with the swelling compensation members 30 are insulation side faces as the swelling compensation members 30 provide thermal insulation between the adjacent battery cells 10.

[0056] Conversely, the innermost surfaces of the side faces 43, 44 of the battery cells 10a-f in thermal contact with the cooling fins 62a-c are not in contact with the swelling compensation members 30. As a consequence, the thermal compensation member material 30 does not impede the transfer of heat from the battery cells to the cooling fins. Therefore, in this example, the side faces 43, 44 in contact with the cooling fins 62a-c are cooling side faces.

[0057] As above for the battery 40 of FIG. 3, the thermal compensation members 30 of the adjacent battery cells not in thermal contact with the cooling fins 62a-c provide thermal insulation between adjacent battery cells to help prevent thermal run away of the entire battery 70 in the event that one of the battery cells 10a-f experiences thermal run-away.

[0058] Although not shown, if desired cooling fins 62 may be located between one or more of the cells 10 of FIG. 3. In such an example the swelling compensation members 30 may impede the transfer of heat from the battery cell 10 to the cooling fin 62. However, such an arrangement does not preclude the use of cooling fins 62 if desired. Furthermore, the material of the swelling compensation members 30 may be selected, or engineered, to be thermally conductive. The cooling fins 62 may comprise a solid layer of thermally conductive material, or may comprise a mesh, fingers or any other suitable configuration. More than one cooling fin 62 may be located between adjacent battery cells 62. The cooling fins 62 may contact any face of the battery cells, in particular the left, right, front and back faces (in the orientation of FIGS. 3 and 5).

[0059] Although the batteries 40, 70 of FIGS. 3 and 5 have been described as having generally rounded cuboid form cell housings 12, it will be appreciated that any shape of battery cell may be used. In addition, the housings 12 of the battery cells 10, and the outer housing 50 of the batteries 40, 70 may comprise rigid housings or pouch cell housing or any combination thereof. The outer housings 50 of the batteries 40, 70 are not essential and may be omitted if desired.