A method of manufacturing an electrode stack of a vehicle battery cell

Abstract

A method of manufacturing an electrode stack (402, fig. 5) comprising applying an electrolyte to a plurality of electrodes (208) to form a plurality of wetted electrodes (214), and subsequently forming the plurality of wetted electrodes into an electrode stack (402, fig. 5). The electrolyte may be applied by using a perforated conveyor belt to transport the electrode through a bath of the electrolyte. The electrolyte may alternatively be applied using a roller, brush or via spraying. The wetted electrodes may be formed into a stack by welding together tabs located on the electrodes. Apparatus 204 is also described comprising applicator 312 for applying the electrolyte, an electrode stack assembly apparatus and a battery cell assembly apparatus for assembling the electrodes in a battery cell case to from a battery cell. The battery may be for use in an electric vehicle.

Description

TECHNICAL FIELD The present disclosure relates to a method of manufacturing an electrode stack of a vehicle battery cell. Aspects of the invention relate to a method of manufacturing an electrode stack of a vehicle battery cell, to a method of manufacturing a vehicle battery cell, and to a manufacturing apparatus. BACKGROUND Batteries for battery electric vehicles typically comprise one or more battery cells each comprising an electrode stack in a battery cell case, wherein the electrode stack is wetted with an electrolyte. Known methods of manufacturing such battery cells include assembling the electrode stack in the battery cell case, adding electrolyte to the battery cell case, and waiting for a period of time to allow the electrode stack to imbibe the electrolyte and become wetted (and therefore functional). Incomplete wetting of the electrode stack may result in sub-optimal functioning of the battery cell. However, the waiting time may introduce a bottle neck in the manufacturing process, may impact the number of battery cells that can be produced, and may incur costs associated with the storage of the battery cells during this period. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a method of manufacturing an electrode stack of a vehicle battery cell, a method of manufacturing a vehicle battery cell, and a manufacturing apparatus. According to an aspect of the present invention there is provided a method of manufacturing a vehicle battery cell, the method comprising: applying an electrolyte to a plurality of individual electrodes to form a plurality of wetted electrodes; and subsequently forming the plurality of wetted electrodes into a vehicle battery cell. According to an aspect of the present invention there is provided a method of manufacturing an electrode stack of a vehicle battery cell, the method comprising: applying an electrolyte to a plurality of electrodes to form a plurality of wetted electrodes; and subsequently forming the plurality of wetted electrodes into an electrode stack. The waiting time associated with wetting of the electrodes is therefore moved upstream (i.e. prior to formation of an electrode stack, and therefore prior to assembly of the electrode stack in a battery cell case to form a battery cell) relative to prior art methods. This may avoid the bottle neck and / or storage requirement associated with prior art methods. In certain embodiments, other manufacturing steps (e.g. formation of the battery cell case) may take place in parallel to the wetting of the electrodes. Therefore, embodiments of the present invention may provide greater efficiencies and / or cost savings in the manufacture of vehicle battery cells in contrast to prior art methods. In certain embodiments, applying the electrolyte to the plurality of electrodes may comprise submerging the plurality of electrodes in electrolyte. Such a method may advantageously be particularly effective for wetting individual electrodes. In certain embodiments, submerging the plurality of electrodes in electrolyte may comprise conveying the plurality of electrodes through a bath of the electrolyte. Such a method is a particularly effective, convenient and / or cost effective method of submerging the plurality of electrodes in electrolyte. Optionally, the method may comprise using a conveyor belt to convey the plurality of electrodes through the bath of the electrolyte. Use of a conveyor belt may facilitate automated wetting of a series of electrodes. In certain embodiments, the conveyor belt may be perforated so as to allow the application of electrolyte from the bath to a first side of each of the plurality of electrodes that is supported on the conveyor belt and a second side of each of the plurality of electrodes that is opposite the first side. A perforated conveyor belt may facilitate simultaneous application of electrolyte on both sides of each electrode. In certain embodiments, applying the electrolyte to the plurality of electrodes may comprise one or more of spraying the plurality of electrodes with electrolyte, using one or more rollers to apply the electrolyte to the plurality of electrodes, or brushing the plurality of electrodes with electrolyte. Any combination of one or more of these methods provides a convenient and effective means of applying electrolyte to the electrodes. Optionally, the method may comprise using a conveyor belt to convey the plurality of electrodes through the spray, rollers and / or brushes. Use of a conveyor belt may facilitate automated wetting of a series of electrodes. In certain embodiments, the conveyor belt may be perforated so as to allow the application of electrolyte to a first side of each of the plurality of electrodes that is supported on the conveyor belt and a second side of each of the plurality of electrodes that is opposite the first side. A perforated conveyor belt may facilitate simultaneous application of electrolyte on both sides of each electrode. In certain embodiments, applying the electrolyte to the plurality of electrodes may comprise applying the electrolyte to a first side of each of the plurality of electrodes and subsequently applying the electrolyte to a second side of each of the plurality of electrodes that is opposite the first side. Such a method may be particularly effective and / or convenient for applying electrolyte to both sides of each electrode. In certain embodiments, forming the plurality of wetted electrodes into an electrode stack may comprise joining tabs of the wetted electrodes together. Tabs of the wetted electrodes are a particularly convenient and effective part of the wetted electrodes to be joined together. In certain embodiments, the tabs may remain free of electrolyte and / or be cleaned of electrolyte prior to joining. Optionally, joining tabs of the wetted electrodes together may comprise welding the tabs of the wetted electrodes together. Welding offers a particularly effective joining method. In certain embodiments, ultrasonic welding is used, which advantageously reduces any ignition risk. In accordance with another aspect of the present invention, there is provided a method of manufacturing a vehicle battery cell, comprising: manufacturing an electrode stack of a vehicle battery cell in accordance with the method described above; and assembling the electrode stack in a battery cell case to form the vehicle battery cell. Battery cells manufactured in accordance with embodiments of the present invention may be made quicker, more efficiently and / or more cost effectively due to the advantages of wetting electrodes prior to formation into an electrode stack. Optionally, assembling the electrode stack in the battery cell case to form the vehicle battery cell may comprise joining tabs of the electrode stack to the battery cell case. The tabs provide a particularly convenient and effective joining region. Joining tabs of the electrode stack to the battery cell case may comprise welding the tabs of the electrode stack to the battery cell case. Welding is a particularly convenient and effective joining method. In certain embodiments, ultrasonic welding is used, which advantageously reduces any ignition risk. In accordance with another aspect of the present invention, there is provided a manufacturing apparatus comprising: at least one applicator for applying electrolyte to a plurality of electrodes to form a plurality of wetted electrodes; an electrode stack assembly apparatus for forming an electrode stack from the wetted electrodes; and a battery cell assembly apparatus for assembling the electrode stack in a battery cell case to form a battery cell. Such a manufacturing apparatus may facilitate the manufacture of a battery cell that makes use of electrodes that are wetted prior to formation in to an electrode stack. As described above, such battery cells may be made quicker, more efficiently and / or more cost effectively compared with prior art battery cells. According to another aspect of the present invention, there is provided a vehicle comprising the battery cell as described above. 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 anyway 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. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 shows a method of manufacturing an electrode stack of a vehicle battery cell in accordance with an embodiment of the present invention; FIG. 2 shows an electrolyte application assembly in accordance with an embodiment of the present invention; FIG. 3 shows an electrolyte application assembly in accordance with another embodiment of the present invention; FIG. 4 shows an electrode stack in accordance with an embodiment of the present invention; FIG. 5 shows a detailed view of a part of the electrode stack of FIG. 4; FIG. 6 shows a schematic view of a battery cell in accordance with an embodiment of the present invention; and FIG. 7 shows a schematic view of a manufacturing apparatus in accordance with an embodiment of the present invention. DETAILED DESCRIPTION FIG. 1 shows a method of manufacturing an electrode stack of a vehicle battery cell in accordance with an embodiment of the present invention. In block 102, the method 100 comprises applying an electrolyte to a plurality of electrodes to form a plurality of wetted electrodes. In block 104, the method 100 comprises subsequently forming the plurality of wetted electrodes into an electrode stack. That is, the individual electrodes (i.e. single electrode sheets) are each wetted with electrolyte prior to formation into an electrode stack. The electrodes may comprise anodes and cathodes. Each electrode may comprise a current collector that is coated with an active material. For example, each cathode may comprise an aluminium current collector coated with active material. Additionally or alternatively, each anode may comprise a copper current collector coated with active material. Wetting of the electrodes prior to formation into the electrode stack permits electrolyte to wet each electrode more freely. In particular, in an electrode stack, electrolyte enters the spaces between electrodes from the edges and gradually progresses into the electrode stack structure. In contrast, individual electrodes have a greater surface area that is directly exposed to electrolyte. Thus, wetting speed is dependent on absorption of electrolyte across the small thickness of the individual electrode rather than in-plane absorption across its larger surface area, and the wetting of the electrodes may advantageously be achieved more quickly. FIG. 2 shows an electrolyte application assembly 202 in accordance with an embodiment of the present invention, and which may be used as part of the method 100 in block 102. The electrolyte application assembly 202 comprises a conveyor belt 206 that is moveable through a bath 212 of electrolyte along a conveyor direction 204. Supported on a surface of the conveyor belt 206 are a plurality of electrodes 208. As the conveyor belt 206 moves through the bath 212 of electrolyte along the conveyor direction 204, the plurality of electrodes 208 are wetted with electrolyte to produce a plurality of wetted electrodes 214. In the non-limiting embodiment shown in FIG. 2, end portions of each of the plurality of electrodes 208 are masked by covers 210 so that such portions are not exposed to the electrolyte when in the bath 212 of electrolyte. As described further below, maintaining electrolyte-free portions of the wetted electrodes 214 is advantageous when forming the wetted electrodes 214 into an electrode stack. In certain embodiments, a first pass of the plurality of electrodes 208 through the bath 212 may apply electrolyte to upper surfaces of the plurality of electrodes 208, and the plurality of electrodes 208 may subsequently be flipped so as to expose the lower surfaces before a subsequent pass through the bath 212 applies electrolyte to the lower surfaces. Additionally or alternatively, the conveyor belt 206 may be perforated or otherwise permeable to permit exposure of the lower surface (supported on the conveyor belt 206) to electrolyte when in the bath 212. In alternative embodiments, any suitable arrangement for submerging the plurality of electrodes 208 in electrolyte may be utilised in place of the bath 212 described herein. In certain embodiments, no conveyor belt 206 may be present (e.g. other arrangements for moving the electrodes 208 relative to the electrolyte may be utilised). In certain embodiments, the wetted electrodes 214 are maintained in a controlled environment during wetting and up until at least formation of a battery cell. In doing so, any risk of oxidisation of the wetted electrodes 214 is mitigated. In certain embodiments, such a controlled environment may comprise an environment consisting of or including an inert gas. FIG. 3 shows an electrolyte application assembly 302 in accordance with another embodiment of the present invention, and which may be used as part of the method 100 in block 102. The electrolyte application assembly 302 of FIG. 3 comprises a conveyor belt 206 that is moveable through a plurality of applicators 312 along a conveyor direction 204. Supported on a surface of the conveyor belt 206 are a plurality of electrodes 208. As the conveyor belt 206 moves through the plurality of applicators 312 along the conveyor direction 204, the applicators 312 each apply electrolyte to the electrodes 208. Such application may be by any suitable method. For example, such application may be by spraying, rolling or brushing. That is, in certain embodiments, the applicators 312 may comprise any one or more of a sprayer, a roller or a brush. In certain embodiments, only a single applicator 312 may be provided. In certain embodiments, the plurality of applicators 312 may comprise different types of applicator 312 (e.g. a sprayer and a roller). In certain embodiments, a single applicator 312 may comprise different types of applicator apparatus (e.g. a single applicator 312 may comprise a sprayer and a roller). In certain embodiments, no conveyor belt 206 may be present. For example, the applicators 312 may move relative to (e.g. static) electrodes 208. Application of the electrolyte on the plurality of electrodes 208 by the plurality of applicators 312 produces a plurality of wetted electrodes 214. In the non-limiting embodiment shown in FIG. 3, end portions of each of the plurality of electrodes 208 are masked by covers 210 so that such portions are not exposed to the electrolyte applied by the applicators 312. As described further below, maintaining electrolyte-free portions of the wetted electrodes 214 is advantageous when forming the wetted electrodes 214 into an electrode stack. In certain embodiments, a first pass of the plurality of electrodes 208 through the plurality of applicators 312 may apply electrolyte to upper surfaces of the plurality of electrodes 208, and the plurality of electrodes 208 may subsequently be flipped so as to expose the lower surfaces before a subsequent pass through the applicators 312 applies electrolyte to the lower surfaces. Additionally or alternatively, the conveyor belt 206 may be perforated orotherwise permeable to permit exposure of the lower surface (supported on the conveyor belt 206) to electrolyte by the applicators 312. Additionally or alternatively, the applicators 312 may directly apply electrolyte to opposing sides of the electrodes 208 simultaneously. In certain embodiments, the wetted electrodes 214 are maintained in a controlled environment during wetting and up until at least formation of a battery cell. In doing so, any risk of oxidisation of the wetted electrodes 214 is mitigated. In certain embodiments, such a controlled environment may comprise an environment consisting of or including an inert gas. FIG. 4 shows a side view of an electrode stack 402 in accordance with embodiments of the present invention and that may be used in methods according to embodiments of the invention. FIG. 5 shows a detailed cross-sectional view of a part of the electrode stack 402 of FIG. 4. As shown in FIG. 5, the electrode stack 402 comprises a plurality of wetted electrodes 214 arranged in a spaced stack, where ends of the plurality of wetted electrodes 214 merge together to form tabs 404. In certain embodiments, the tabs 404 may be formed by welding or otherwise joining the ends of the wetted electrodes 214 together. Adjacent electrodes may be parted by a porous separator layer. The tabs 404 form electrical terminals of the electrode stack 402 (i.e. one tab 404 forms a positive terminal of the electrode stack 402 whilst the other tab 404 forms a negative terminal of the electrode stack 402). In the non-limiting embodiment shown in FIG. 5, the wetted electrodes 214 transition through three regions before terminating at the respective tabs 404. In a first region 502, the wetted electrodes 214 each comprise current collectors and an active material, and are separated from one another by separator layers. The current collectors extend from the first region 502 through a second region 504 wherein the separator layers are disposed between adjacent current collectors but in which the current collectors are not coated with the active material. The current collectors extend from the second region 504 to a third region 506 in which the separator layers are no longer disposed between adjacent current collectors. Each current collector then bends to join to an adjacent current collector to form the tab 404. The tab 404 therefore increases in thickness as the current collectors progressively join one another. In certain embodiments, the ends of the wetted electrodes 214 that are joined together are the electrolyte-free portions of the wetted electrodes 214 that were previously masked by covers 210 when exposed to electrolyte (i.e. the covers 210 are removed prior to joining). In such embodiments, the risk of electrolyte causing a spark or ignition during welding (or other joining method) is mitigated. In certain embodiments, the portions to be welded may be otherwise cleaned of electrolyte and / or blow-dried (e.g. with an inert gas) to remove any incidental electrolyte that may be present prior to joining to form the tabs 404. In certain embodiments, the tabs 404 may comprise merged current collectors without active material(s). In certain embodiments, the welding may be ultrasonic welding which further reduces any potential spark or ignition risk during formation of the tabs 404. The electrode stack 402 may be any suitable arrangement of layered wetted electrodes 214 including linearly arranged wetted electrodes (e.g. as described below) and rolled wetted electrodes. FIG. 6 shows a battery cell 602 that is formed by assembling the electrode stack 402 (comprising wetted electrodes 214) in a battery cell case 604. The tabs 404 of the electrode stack 402 may be welded or otherwise joined to the battery cell case 604 to form the battery cell 602. FIG. 7 shows a manufacturing apparatus 702 comprising at least one applicator 312 for applying electrolyte to a plurality of electrodes to form a plurality of wetted electrodes 214, an electrode stack assembly apparatus 706 for forming an electrode stack 402 from the wetted electrodes 214, and a battery cell assembly apparatus 710 for assembling the electrode stack 402 in a battery cell case 604 to form a battery cell 602. In alternative embodiments, the at least one applicator 312 may be substituted for the above-described bath 212 or any other apparatus arranged to submerge and / or otherwise coat the electrodes 208 in electrolyte to form the plurality of wetted electrodes 214. One or more of the battery cells 602 may be assembled together to form a battery 804. 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

1. A method of manufacturing an electrode stack of a vehicle battery cell, the method comprising: applying an electrolyte to a plurality of electrodes to form a plurality of wetted electrodes; and subsequently forming the plurality of wetted electrodes into an electrode stack.

2. The method of claim 1, wherein applying the electrolyte to the plurality of electrodes comprises submerging the plurality of electrodes in electrolyte.

3. The method of claim 2, wherein submerging the plurality of electrodes in electrolyte comprises conveying the plurality of electrodes through a bath of the electrolyte.

4. The method of claim 3, comprising using a conveyor belt to convey the plurality of electrodes through the bath of the electrolyte.

5. The method of claim 4, wherein the conveyor belt is perforated so as to allow the application of electrolyte from the bath to a first side of each of the plurality of electrodes that is supported on the conveyor belt and a second side of each of the plurality of electrodes that is opposite the first side.

6. The method of claim 1, wherein applying the electrolyte to the plurality of electrodes comprises spraying the plurality of electrodes with electrolyte.

7. The method of claim 1, wherein applying the electrolyte to the plurality of electrodes comprises using one or more rollers to apply the electrolyte to the plurality of electrodes.

8. The method of claim 1, wherein applying the electrolyte to the plurality of electrodes comprises brushing the plurality of electrodes with electrolyte.

9. The method of any one of claims 1 -4 or 6-8, wherein applying the electrolyte to the plurality of electrodes comprises applying the electrolyte to a first side of each of the plurality of electrodes and subsequently applying the electrolyte to a second side of each of the plurality of electrodes that is opposite the first side.

10. The method of any one of claims 1 to 9, wherein forming the plurality of wetted electrodes into an electrode stack comprises joining tabs of the wetted electrodes together.

11. The method of claim 10, wherein joining tabs of the wetted electrodes together comprises welding the tabs of the wetted electrodes together.

12. A method of manufacturing a vehicle battery cell, comprising:manufacturing an electrode stack of a vehicle battery cell in accordance with any any one of claims 1 to 11;andassembling the electrode stack in a battery cell case to form the vehicle battery cell.

13. The method of claim 12, wherein assembling the electrode stack in the battery cell case to form the vehicle battery cell comprises joining tabs of the electrode stack to the battery cell case.

814. The method of claim 13, wherein joining tabs of the electrode stack to the battery cell case comprises welding the tabs of the electrode stack to the battery cell case.

15. A manufacturing apparatus comprising:at least one applicator for applying electrolyte to a plurality of electrodes to form a plurality of wetted 5 electrodes;an electrode stack assembly apparatus for forming an electrode stack from the wetted electrodes; anda battery cell assembly apparatus for assembling the electrode stack in a battery cell case to form a battery cell.10

Images