A battery cell for a vehicle

Abstract

Aspects of the present invention relate to a battery cell (202) for a vehicle, comprising a battery cell housing (104), at least one electrode stack (110) disposed in the battery cell housing (104), and at least one compressible element (204) disposed in the battery cell housing (104), the at least one compressible element (204) being configured to counter any swelling of the battery cell (102).

Description

[0001] A BATTERY CELL FOR A VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a battery cell for a vehicle. Aspects of the invention relate to a battery cell for a vehicle, a battery for a vehicle, a vehicle, a method of manufacturing a battery cell for a vehicle, a method of manufacturing a battery for a vehicle, and an apparatus for manufacturing a battery cell for a vehicle.

[0004] BACKGROUND

[0005] Certain known lithium-ion pouch and prismatic battery cells may be prone to swelling as a result of various reversible and irreversible electrochemical reactions that take place during its charging and discharging cycles. Certain known battery cells are known to slowly and steadily expand and contract (also known as “cell breathing”). Throughout the service life of pouch and prismatic battery cells, swelling may occur due to a number of factors including intercalation of ions into the electrodes, gas generation from side reactions within the battery cell, and growth of the solid electrolyte interphase (SEI) layer due to degradation. Irreversible swelling factors can result in a loss of cell capacity, high stress concentrations on electrodes, and / or excessive cell-to-cell load transfer within a cell stack, the latter presenting a great challenge for the cell-to-module / pack integration. These issues may give rise to cell stack bowing, misaligned busbar welding points, and / or the detachment of cell carriers within a stack of battery cells.

[0006] It is known to control the swelling effect and prevent or limit the above-noted challenges by the introduction of compression elements (in the form of pads) between the battery cells in a battery. Such compression elements serve to exert a constant force across the interface between adjacent battery cells. This restoring force is typically achieved by compressing the cell stack assembly after the endplates have been fitted. This brings both mechanical and electromechanical benefits to the cell. During the stack assembly process, compression pads are either inserted between every adjacent cell or in a periodic manner. A major challenge arises with controlling the cell-pad-cell alignment. Unintended misalignment between the cells and pads can be amplified once the stack assembly is compressed at its endplates which could lead to non-uniform pressure distribution along the battery cell interfaces and relative displacement between battery cells. Such problems cascade to further problems in the surrounding pack.

[0007] It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

[0008] SUMMARY OF THE INVENTION

[0009] Aspects and embodiments of the invention provide a battery cell for a vehicle, a battery for a vehicle, a vehicle, a method of manufacturing a battery cell for a vehicle, a method of manufacturing a battery for a vehicle, and an apparatus for manufacturing a battery cell for a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a battery cell for a vehicle, comprising a battery cell housing, and at least one compressible element disposed in the battery cell housing, the at least one compressible element being configured to counter any swelling of the battery cell.

[0010] According to an aspect of the present invention there is provided a battery cell for a vehicle, comprising a battery cell housing, at least one electrode stack disposed in the battery cell housing, and at least one compressible element disposed in the battery cell housing, the at least one compressible element being configured to counter any swelling of the battery cell.

[0011] The battery cell is independently self-constraining such that the compressible element is an internal feature within the battery cell housing (as opposed to being disposed externally of the battery cell housing, but between adjacent battery cells as in the prior art). Not only will this help to control the swelling phenomenon of the electrodes, but it will ensure that the compressible element may be tightly controlled in its alignment with the electrode stack. It will also reduce the number of parts required during the stack assembly process (only battery cells need to be aligned with one another).

[0012] In certain embodiments, the battery cell comprises at least one can , wherein each of the at least one electrode stack is disposed in one of the at least one cans, and at least part of the at least one can is electrically conductive. The at least one can may serve as both part of the battery cell housing and an electrically conductive terminal of the battery cell.

[0013] In certain embodiments, the at least one compressible element may not be disposed in the at least one can. Whilst there are certain benefits associated with the compressible element being disposed in the can, embodiments in which the compressible element is not disposed in the at least one can may still benefit from the advantages discussed above.

[0014] In certain embodiments, the battery cell comprises two cans, and the at least one compressible element is disposed between the two cans. This is a particularly convenient and effective location for the compressible element. In certain embodiments, the at least one can comprises a recess for accommodating at least part of the at least one compressible element. The recess may improve the alignment of the compressible element within the battery cell.

[0015] In certain embodiments, the at least one compressible element is planar. A planar shape may be conveniently disposed within the battery cell whilst countering swelling therein.

[0016] In certain embodiments, each at least one electrode stack comprises a plurality of electrodes each extending along a first longitudinal axis, and the at least one compressible element extends in a first plane that is parallel to the first longitudinal axis of each of the plurality of electrodes. This orientation serves to mitigate any swelling effects along directions that are most likely to exhibit such a phenomenon. In certain embodiments, the at least one compressible element is pre-loaded. Pre-loading the compressible element may allow a more uniform force response to be provided by the compressible element.

[0017] In certain embodiments, the compressible element may comprise a foam (e.g. polyurethane foam or silicone foam). Such materials are particularly advantageous for providing the desired restoring force.

[0018] Additionally or alternatively, the compressible element may comprise a dielectric material. In such embodiments, the compressible element may additionally serve to electrically isolate two components within the battery cell (e.g. two adjacent cans).

[0019] According to another aspect of the present invention there is provided a battery for a vehicle, comprising a plurality of battery cells assembled together, wherein the plurality of battery cells are as described above.

[0020] In certain embodiments, no compressible elements are present between adjacent battery cells (i.e. externally of each battery cell). Since embodiments of the present invention may provide the abovedescribed benefits due to the compressible element being within the battery cell housing, it may not be necessary to include them between adjacent battery cells (although they may be present in certain embodiments).

[0021] According to another aspect of the present invention there is provided a vehicle comprising a battery cell as described above or a battery as described above.

[0022] According to another aspect of the present invention there is provided a method of manufacturing a battery cell, comprising assembling at least one electrode stack in a battery cell housing, and assembling at least one compressible element in the battery cell housing, the at least one compressible element being configured to counter any swelling of the battery cell.

[0023] In certain embodiments, the method may comprise pre-loading the at least one compressible element.

[0024] According to another aspect of the present invention there is provided a method of manufacturing a battery for a vehicle, comprising manufacturing a plurality of battery cells as described above, and assembling the plurality of battery cells together.

[0025] According to another aspect of the present invention there is provided an apparatus for manufacturing a battery cell, comprising a loading apparatus for pre-loading a compressible element, and an assembly apparatus for assembling the compressible element in a battery cell housing. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0028] FIG. 1 shows a perspective view of a battery cell;

[0029] FIG. 2 shows a top down view of the battery cell of FIG. 1 ;

[0030] FIG. 3 shows a cross-sectional view of the battery cell of FIG. 2 taken along line A-A;

[0031] FIG. 4 shows a cross-sectional view of detail B of the battery cell of FIG. 3;

[0032] FIG. 5 shows a schematic cross-sectional view of a battery cell according to an embodiment of the present invention;

[0033] FIG. 6 shows a perspective view of a battery according to an embodiment of the present invention;

[0034] FIG. 7 shows a side view of the battery of FIG. 6;

[0035] FIG. 8 shows a cross-sectional view of the battery of FIG. 7 taken along line C-C;

[0036] FIG. 9 shows a cross-sectional view of detail D of the battery of FIG. 8;

[0037] FIG. 10 illustrates a method of manufacturing a battery cell in accordance with an embodiment of the present invention;

[0038] FIG. 11 illustrates a method of manufacturing a battery in accordance with an embodiment of the present invention;

[0039] FIG. 12 schematically shows an apparatus for manufacturing a battery cell in accordance with an embodiment of the present invention; and

[0040] FIG. 13 shows a vehicle in accordance with an embodiment of the present invention.

[0041] DETAILED DESCRIPTION

[0042] FIG. 1 shows a perspective view of a battery cell 102. As described below, the battery cell 102 may be assembled with other identical or similar battery cells 102 to form a battery. The battery may be a vehicle battery (e.g. a traction battery). In certain embodiments, the battery may be a pouch battery or a prismatic battery. In certain embodiments, the battery may be any battery that has a layered electrode arrangement (as described further below).

[0043] The battery cell 102 comprises two cans 120, namely a first can 122 and a second can 124 stacked on one another, a first cover 106, a second cover 108 (shown in FIG. 3 and FIG. 4) and a battery cell frame 130 that extends around a periphery of the battery cell 102. A battery cell housing 104 of the battery cell 102 comprises the first cover 106, the second cover 108, the battery cell frame 130 and parts of the two cans 120. FIG. 2 shows a top down view of the battery cell 102 of FIG. 1.

[0044] FIG. 3 shows a cross-sectional view of the battery cell 102 of FIG. 2 taken along section line A-A. As shown in FIG. 3, the battery cell 102 includes a pair of electrode stacks 110 (i.e. layered arrangements of electrodes). The pair of electrode stacks 110 comprises a first electrode stack 112 and a second electrode stack 114. Each of the electrode stacks 1 10 is disposed within a can 120. The two cans 120 comprise a first can 122 and a second can 124 wherein the first can 122 is stacked on the second can 124. The first electrode stack 112 is disposed within the first can 122 and the second electrode stack 114 is disposed in the second can 124. The cans 120 contain an electrolyte such that the electrode stacks 110 are in contact with the electrolyte. In certain embodiments, the electrolyte may be a liquid. In other embodiments, the electrolyte may be a solid.

[0045] The first cover 106 is joined to the first can 122 to seal a volume that contains the first electrode stack 112. Similarly, the second cover 108 is joined to the second can 124 to seal a volume that contains the second electrode stack 114. In such sealed volumes, the electrode stacks 1 10 each reside in an electrolyte. Each electrode stack 110 is electrically connected to the each of the first can 122 and the second can 124 such that the cans 120 serve as electrical terminals of the battery cell 102.

[0046] FIG. 4 shows detail B of the battery cell 102 of FIG. 3. Each electrode stack 110 comprises a stack of individual electrodes that extend parallel to a first longitudinal axis 118, and converge and terminate in tabs 116. At least one tab 116 is the convergence of the anodes of the respective electrode stack 1 10 and at least one other tab 116 is the convergence of the cathodes of the respective electrode stack 110. The tabs 116 are electrically connected to the cans 120. More specifically, at least one tab 116 of each electrode stack 110 is electrically connected to the first can 122 and at least one other tab 116 of the respective electrode stack 110 is electrically connected to the second can 124.

[0047] As shown in FIG. 4, the second can 124 includes a second can aperture 126 such that the second electrode stack 114 disposed in the second can 124 may electrically connect to the first can 122. In the non-limiting embodiment shown in FIG. 4, part of the first can 122 extends through the second can aperture 126 so that the electrical connection may be made. In alternative embodiments, the tab 1 16 of the second electrode stack 114 that connects to the first can 122 may extend through the second can aperture 126 such that no part of the first can 122 need extend through the second can aperture 126. At the same end of the battery cell 102 on an opposing side of the first can 122, the tab 116 of the first electrode stack 112 disposed within the first can 122 connects to the first can 122. Thus, the first can 122 is electrically connected on opposing surfaces to tabs 1 16 of two distinct electrode stacks 110. The tabs 116 connecting to the first can 122 have the same polarity as one another such that the first can 122 becomes a positive terminal or a negative terminal of the battery cell 102.

[0048] At an opposing end of the battery cell 102 (not shown in FIG. 4), the first can 122 has a first can aperture such that another tab 116 of the first electrode stack 112 disposed in the first can 122 may form an electrical connection with the second can 124. The opposing tab 116 (not shown in FIG. 4) of the electrode stack 1 10 disposed in the second can 124 is also electrically connected to second can 124. Thus, the second can 124 is electrically connected on opposing surfaces to tabs 116 of two electrode stacks 110. The tabs 116 connecting to the second can 124 have the same polarity as one another such that the second can 124 becomes a positive terminal or a negative terminal (opposite to the polarity of the first can 122) of the battery cell 102.

[0049] An electrical insulator, such as a coating or insert (not visible in the Figures), is disposed between the first can 122 and the second can 124 to electrically isolate one from the other.

[0050] FIG. 5 shows a schematic cross-sectional view of a battery cell 202 in accordance with an embodiment of the present invention. The battery cell 202 may comprise any or all of the features described above in relation to battery cell 102. As shown in FIG. 5, the battery cell 202 comprises a battery cell housing 104, and a pair of cans 120 (namely a first can 122 and a second can 124) wherein each can 120 contains an electrode stack 110. In particular, the first can 122 contains a first electrode stack 1 12 and the second can 124 contains a second electrode stack 114. The battery cell 202 also includes a compressible element 204. In the non-limiting embodiment, the compressible element 204 is disposed between the adjacent cans 120, but not within either can 120. In such an embodiment, the compressible element 204 is not exposed to or in contact with electrolyte that is contained in the cans 120. In this illustrated non-limiting embodiment, the cans 120 each comprise a recess 128 for accommodating at least part of the at least one compressible element 204.

[0051] The compressible element 204 is configured to counter any swelling of the battery cell 202. In particular, swelling of a part of the battery cell 202 may exert a force on the compressible element 204. In response, the compressible element 204 may exert an opposing force on the swelling part. Consequently, the net force exerted externally of the battery cell housing 104 due to the swelling may be zero or at least reduced due to the presence of the compressible element 204. In the absence of such a restoring opposing force, such swelling can stack up in a battery comprising multiple stacked battery cells and increase the likelihood of failure or sub-optimal operation of the battery.

[0052] The compressible element 204 may be pre-loaded prior to assembly within the battery cell housing 104. The compressible element 204 may have a generally non-linear stress-strain curve associated with it (that defines the operating limits of the compressible element 204), but one that includes a generally linear section. Pre-loading the compressible element 204 may mean that in operation the compressible element 204 is compressed and provides a restoring force which may be substantially constant. Operating in the upper limit of the stress-strain curve may lead to damage of the battery cell 202 over time.

[0053] In the non-limiting embodiment shown in FIG. 5, the compressible element 204 is planar. That is, the compressible element 204 generally extends in a first plane 206. In the non-limiting embodiment shown in FIG. 5, the first plane 206 is parallel to the first longitudinal axes 118 of the electrode stacks 110. Whilst the compressible element 204 has some (non-zero) thickness in a direction perpendicular to the first plane 206, this dimension is much smaller than the two orthogonal dimensions of the compressible element 204 (i.e. the length and width which define the first plane 206). The length of the compressible element 204 (i.e. along the dimension of the first plane 206 that is parallel to the first longitudinal axes 118 may be less than the lengths of the electrode stacks 110. Such an arrangement allows the compressible element 204 to be disposed between the adjacent cans 120 without interfering with the connection of the tabs 116 of each of the electrode stacks 110 to each of the cans 120.

[0054] In alternative embodiments, the compressible element 204 may have other forms.

[0055] In certain embodiments, more than one compressible element 204 may be disposed within the battery cell housing 104.

[0056] In certain embodiments, the one or more compressible elements 204 may be disposed in the battery cell housing 104 in a position other than between adjacent cans 120 as illustrated in FIG. 5. In such embodiments, the one or more compressible element 204 may still not be disposed within the cans 120 and therefore be isolated from electrolyte contained in the cans 120. In other embodiments, the one or more compressible element 204 may be disposed within one or both of the cans 120 and therefore be in contact with the electrolyte. In certain non-limiting embodiments, one or more compressible elements 204 may be disposed between one or more of the electrode stacks 1 10 and the battery cell housing 104. In certain embodiments, for example, one or more of the electrode stacks 110 may be disposed between a pair of compressible elements 204.

[0057] Whilst the skilled person will appreciate that the compressible element 204 may comprise any suitable compressible material, in certain non-limiting embodiments, the compressible element 204 may comprise polyurethane or silicone. In certain embodiments, the compressible element 204 may comprise a foam (e.g. polyurethane foam or silicone foam).

[0058] FIG. 6 shows a perspective view of a battery 602 in accordance with an embodiment of the present invention. The battery 602 comprises multiple battery cells 202 stacked with one another. In the non-limiting embodiment shown in FIG. 6, the battery 602 comprises a battery housing 604 surrounding at least parts of the battery cells 202. In such a battery 602, the battery cells 202 are electrically connected with one another In particular, the can 120 serving as the positive terminal of one battery cell 202 is electrically connected to the can 120 serving as the negative terminal of the adjacent battery cell 202 (e.g. the first can 122 of one battery cell 202 is electrically connected to the second can 124 of the next battery cell 202 of the battery 602, such as shown in FIG. 9). In this stacked configuration, one end can 120 (e.g. a first can 122) serves as a positive terminal of the battery 602 and another end can 120 (e.g. a second can 124) at the opposite end of the stack serves as a negative terminal of the battery 602.

[0059] Placement of the compressible element 204 within the battery cell 202 negates any requirement to assemble and align compressible elements between battery cells when assembling the battery cells to form a battery. Consequently, the assembly of the battery 602 in accordance with embodiments of the present invention is advantageously simplified compared to prior art arrangements. In certain embodiments, additional compressible elements may be provided outside of and between adjacent battery cells. In other embodiments, no compressible elements are present between adjacent battery cells.

[0060] FIG. 7 shows a side view of the battery 602 of FIG. 6.

[0061] FIG. 8 shows a cross-sectional view of the battery 602 of FIG. 7 taken along section line C-C.

[0062] FIG. 9 shows detail D of the battery 602 of FIG. 8.

[0063] FIG. 10 shows a method 1000 of manufacturing a battery cell 202 in accordance with an embodiment of the present invention. In block 1002, the method 1000 comprises assembling at least one electrode stack 110 in a battery cell housing 104. In block 1004, the method 1000 comprises pre-loading at least one compressible element 204, the at least one compressible element being configured to counter any swelling of the battery cell 102. In block 1006, the method 1000 comprises assembling the at least one compressible element 204 in the battery cell housing 104. In certain embodiments, the step of pre-loading (block 1004) may not take place (e.g. depending on the material of the compressible element 204).

[0064] FIG. 11 shows a method 1102 of manufacturing a battery 602 in accordance with an embodiment of the present invention. The method 1102 comprises manufacturing a plurality of battery cells 202 according to the method 1000 described above and subsequently assembling the plurality of battery cells 202 together to form the battery 602.

[0065] FIG. 12 schematically shows an apparatus 1202 for manufacturing a battery cell 202 in accordance with an embodiment of the present invention. The apparatus 1202 comprises a loading apparatus 1204 for pre- loading a compressible element 204, and an assembly apparatus 1208 for assembling the compressible element 204 in a battery cell housing 104 to form the battery cell 202.

[0066] FIG. 13 shows a vehicle 1302 comprising a battery 602 in accordance with an embodiment of the present invention.

[0067] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1 . A battery cell for a vehicle, comprising: a battery cell housing; at least one electrode stack disposed in the battery cell housing; and at least one compressible element disposed in the battery cell housing, the at least one compressible element being configured to counter any swelling of the battery cell.

2. The battery cell of claim 1 , comprising at least one can, wherein each of the at least one electrode stacks is disposed in one of the at least one cans, and at least part of the at least one can is electrically conductive.

3. The battery cell of claim 2, wherein the at least one compressible element is not disposed in the at least one can.

4. The battery cell of claim 3, comprising two cans, wherein the at least one compressible element is disposed between the two cans.

5. The battery cell of any one of claims 2 to 4, wherein the at least one can comprises a recess for accommodating at least part of the at least one compressible element.

6. The battery cell of any one of claims 1 to 5, wherein the at least one compressible element is planar.

7. The battery cell of claim 6, wherein each at least one electrode stack comprises a plurality of electrodes each extending along a first longitudinal axis, and wherein the at least one compressible element extends in a first plane that is parallel to the first longitudinal axis of each of the plurality of electrodes.

8. The battery cell of any one of claims 1 to 7, wherein the at least one compressible element is pre- loaded.

9. A battery for a vehicle, comprising a plurality of battery cells assembled together, wherein the plurality of battery cells are according to any one of claims 1 to 8.

10. The battery of claim 9, wherein no compressible elements are present between adjacent battery cells.11 . A vehicle comprising a battery cell according to any one of claims 1 to 8 or a battery according to claim 9 or 10.

12. A method of manufacturing a battery cell, comprising: assembling at least one electrode stack in a battery cell housing; and assembling at least one compressible element in the battery cell housing, the at least one compressible element being configured to counter any swelling of the battery cell.

13. The method of claim 12, comprising pre-loading the at least one compressible element.

14. A method of manufacturing a battery for a vehicle, comprising: manufacturing a plurality of battery cells according to claim 12 or 13; and assembling the plurality of battery cells together.

15. An apparatus for manufacturing a battery cell, comprising: a loading apparatus for pre-loading a compressible element; and an assembly apparatus for assembling the compressible element in a battery cell housing.

Images