A battery cell

Abstract

A battery cell (100) comprising: a terminal (104); an electrode assembly (106) having a connective tab (108) extending from a first side (106a) of the electrode assembly; a current collector (200) connecting the terminal to the electrode assembly via the connective tab to enable transfer of electrical current from the electrode assembly to the terminal; and a weld structure (204) fixing the connective tab to the current collector, the weld structure extending along a connection axis (206) substantially parallel to the first side of the electrode assembly and comprising a first plurality of weld lines (300), the weld lines being spaced apart from one another and inclined relative to the connection axis.

Description

[0001] A BATTERY CELL

[0002] Technical Field

[0003] The present disclosure relates to a battery cell and a method for manufacturing a battery cell.

[0004] Background

[0005] In addressing climate change, there is an increasing demand for rechargeable batteries, e.g. to enable electrification of transportation and to supplement renewable energy. Such batteries typically comprise a number of battery cells coupled together to provide the desired voltage and current.

[0006] Rechargeable or 'secondary' batteries find widespread use as electrical power supplies and energy storage systems. For example, in automobiles, battery packs formed of a plurality of battery modules, wherein each battery module includes a plurality of electrochemical cells, are provided as a means of effective storage and utilization of electric power.

[0007] Several different form factors exist for the electrochemical cells applied in secondary batteries depending on their intended application field. In automotive applications, the most common cell types are cylindrical, prismatic and pouch cells.

[0008] A battery cell stores electrical energy in an electrode assembly, which may be stacked, and referred to as an 'electrode stack', or rolled, and referred to as an 'electrode roll' or a 'jelly roll'. Stored electrical energy may then be collected and transferred to the terminals of the battery cell via current collectors, which may be adapted for (electrical) connection to the terminal(s) and to the electrode assembly. One current collector may connect between an anode of the electrode assembly and an anode terminal (negative electrode), while another current collector may connect between a cathode of the electrode assembly and a cathode terminal (positive electrode).

[0009] A known method of connecting a current collector to an electrode (anode or cathode) of an electrode assembly is to weld the current collector to one or more tabs that protrude from the electrode stack or electrode roll. The tabs are formed from a foil that acts as a substrate for the electrode. Welding an electrode foil to a current collector can cause the formation of heat cracks in the foil. This is a particular issue for electrodes having an aluminium foil (typically, the cathode will have an aluminium foil). The cracks reduce the tensile strength and electrical conductivity of the connection between electrode and current collector. The cracks are also likely to reduce the lifetime of the connection and, even, the overall battery cell.

[0010] Improving the connection between electrode and current collector presents a challenge.

[0011] According to a first aspect of the disclosure we provide a battery cell comprising: a terminal; an electrode assembly having a connective tab extending from a first side of the electrode assembly; a current collector connecting the terminal to the electrode assembly via the connective tab to enable transfer of electrical current from the electrode assembly to the terminal; and a weld structure fixing the connective tab to the current collector, the weld structure extending along a connection axis substantially parallel to the first side of the electrode assembly and comprising a first plurality of weld lines, the weld lines being spaced apart from one another and inclined relative to the connection axis.

[0012] In one or more embodiments, the weld lines may be oriented at least 20 degrees from the connection axis. In one or more embodiments, the weld lines may be oriented at least 45 degrees from the connection axis. In one or more embodiments, the weld lines may be at least 75 degrees from the connection axis. In one or more embodiments, the weld lines may be oriented substantially 90 degrees from the connection axis.

[0013] Each weld line may extend from a first end to a second end and the first plurality of weld lines may comprise at least a first subset of weld lines and a second subset of weld lines. In one or more embodiments, the first ends of the weld lines in the first subset of weld lines may be out of alignment with the first ends of the weld lines within the second subset of weld lines. In one or more embodiments, the weld structure extends over an area having a lateral dimension, and the first ends of the weld lines of the first subset of weld lines may be laterally offset from the first ends of the weld lines of the second subset of weld lines by at least 5% of the lateral dimension. In one or more embodiments, the first ends of the weld lines of the first subset of weld lines may be laterally offset from the first ends of the weld lines of the second subset of weld lines by at least 10% of the lateral dimension. In one or more embodiments, the first ends of the weld lines of the first subset of weld lines may be laterally offset from the first ends of the weld lines of the second subset of weld lines by at least 20% of the lateral dimension.

[0014] In one or more embodiments, adjacent weld lines of the first plurality of weld lines may be spaced apart by at least 0.1 mm. In one or more embodiments, adjacent weld lines of the first plurality of weld lines may be spaced apart by at least 0.2 mm. In one or more embodiments, adjacent weld lines of the first plurality of weld lines may be spaced apart by at least 0.3 mm.

[0015] In one or more embodiments, the first plurality of weld lines may include at least 10 weld lines. In one or more embodiments, the first plurality of weld lines may include at least 30 weld lines.

[0016] In one or more embodiments, the weld structure may further comprise a second plurality of weld lines spaced apart from the first plurality of weld lines.

[0017] The weld structure extends over an area having a longitudinal dimension. In one or more embodiments, the first plurality of weld lines may be spaced apart from the second plurality of weld lines by at least 5% of the longitudinal dimension. In one or more embodiments, the first plurality of weld lines may be spaced apart from the second plurality of weld lines by at least 10% of the longitudinal dimension. In one or more embodiments, the first plurality of weld lines may be spaced apart from the second plurality of weld lines by at least 20% of the longitudinal dimension.

[0018] In one or more embodiments, the connective tab may comprise aluminium. In some embodiments, the connective tab may consist of aluminium.

[0019] In one or more embodiments, the electrode assembly may comprise a roll or stack of one or more electrode sheets having a plurality of sheet tabs, each sheet tab formed as an extension from the roll or stack of one or more electrode sheets. All the sheet tabs of the plurality of sheet tabs may be joined together to form the connective tab. In one or more embodiments, the electrode assembly may have a substantially rectangular profile and further comprise a second side opposite to the first side, a third side extending from the first side to the second side and a fourth side opposite to the third side. The terminal may be arranged adjacent to the third side. The current collector assembly may extend from the terminal at the third side to the connective tab at the first side.

[0020] In one or more embodiments, the electrode assembly is planar, the current collector comprises a planar weld surface that extends substantially parallel to the electrode assembly, and the weld structure fixes the connective tab to the current collector via the weld surface.

[0021] According to a second aspect of the disclosure we provide a method of manufacturing a battery cell, the method comprising: providing an electrode assembly having a connective tab extending from a first side of the electrode assembly; welding the connective tab to a current collector so as to form a weld structure fixing the connective tab to the current collector, the weld structure extending along a connection axis substantially parallel to the first side of the electrode assembly and comprising a first plurality of weld lines, the weld lines being spaced apart from one another and inclined relative to the connection axis; and coupling the current collector to a terminal to enable transfer of electrical current from the electrode assembly to the terminal.

[0022] The method of the second aspect of the disclosure may be used to manufacture a battery cell according to the first aspect of the disclosure.

[0023] In one or more embodiments, the step of welding the connective tab to the current collector may comprise using a laser welding technique to fuse the connective tab to the current collector.

[0024] In one or more embodiments, the step of welding the connective tab to the current collector may comprise sequentially welding the weld lines of the first plurality of weld lines.

[0025] According to a third aspect of the disclosure we provide a vehicle including a battery system comprising the battery cells as described herein or using battery cells manufactured with use of the method as described herein. The vehicle may comprise a battery electric vehicle and the battery system may be configured to provide motive power.

[0026] A further aspect of the disclosure may comprise a battery system comprising the battery cells as described herein or using battery cells manufactured with use of the method as described herein, wherein the battery system comprises a battery energy storage system, such as grid-connected battery energy storage system. In other examples, the battery system comprises part of a trailer or roof-box for coupling to a vehicle.

[0027] While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that other embodiments, beyond the particular embodiments described, are possible as well.

[0028] The figures and Detailed Description that follow also exemplify various example embodiments. Various example embodiments may be more completely understood in consideration of the following Detailed Description in connection with the accompanying Drawings.

[0029] Brief Description of the Drawings

[0030] One or more embodiments will now be described by way of example only with reference to the accompanying drawings in which:

[0031] Figure 1 schematically shows a battery cell;

[0032] Figure 2 schematically shows a cross-sectional view of a portion of the battery cell shown in Figure 1;

[0033] Figures 3 to 10 schematically show respective examples of a weld structure for fixing a connective tab to a current collector; and

[0034] Figure 11 an example process flow diagram illustrating a method of manufacturing a battery cell.

[0035] Detailed Description

[0036] Figure 1 schematically shows a battery cell 100, also referred to hereinafter as 'cell 100', having a prismatic form factor. The cell 100 may have a substantially cuboidal shape, thereby having a rectangular profile, as shown in Figure 1. The cell 100 may comprise a casing 102, which may determine the general form factor of the cell 100 and may be configured (e.g., in its dimensions) for installation into a larger battery module, battery pack, or other battery assembly. The casing 102 may be rigid and resistant to external shocks or impacts, for example being made of metal such as aluminium or made of a high-density plastic.

[0037] The casing 102 may be formed from a plurality of sides joined together or may be formed of substantially one or two pieces, e.g., by extrusion, additive manufacturing (AM), or some other manufacturing technique. According to an example, the casing 102 may comprise a height (extending vertically as shown in Figure 1), a width (extending horizontally as shown in Figure 1), and a thickness (not visible).

[0038] The prismatic form factor for the cell 100, as defined substantially by the casing 102, may comprise two larger faces 102b (other larger face not visible) spaced apart by a relatively small distance in the thickness direction, and a plurality of comparatively smaller faces 102a, 102c, 102d, 102e bridging between the two larger faces 102b. The casing 102 may be formed by providing an open cuboidal shape and sealing the open face of the open cuboidal shape with a lid. For example, the lid may form the upper face 102a of the casing 102 (shown only as the top line in Figure 1).

[0039] Internal components of the cell 100 may be introduced into the casing 102 and then a lid 102a may be provided thereover and sealed in placed to thereby contain the internal components. The lid 102a may be attached in a substantially watertight fashion so as to contain liquid electrolyte in the cell 100, for example. The lid 102a may be provided with a vent, an injection port for injecting electrolyte, and / or other features, the details of which are outside the scope of the present disclosure.

[0040] In the illustrated example, provided on the casing 102 of the cell, and extending into the cell 100, are a pair of terminals 104. One of the terminals 104 may be an anode and the other may be a cathode. The terminals 104 may be riveted through the casing 102, e.g., through the lid 102a thereof, and provided with a gasket therearound to improve the watertight seal that the casing 102 may preferably provide. The terminals 104 may be made of any suitable conductive material, although the particular manufacture and installation of the terminals 104 is outside the scope of the present disclosure. Both of the terminals 104 are shown installed at an upper face 102a of the casing 102 of the cell 100. However, it will be appreciated that either of the terminals 104 may instead be provided at any location around the casing 102 of the cell 100.

[0041] Figure 2 shows a cross-sectional view of the portion of the cell 100 indicated by the dotted box in Figure 1, revealing an internal space 103 within the casing 102. As shown in this figure, the cell 100 may comprise a terminal 104 that extends through the casing 102 and into the internal space 103 of the cell 100.

[0042] The cell 100 may further comprise an electrode assembly 106, which may be an electrode roll or an electrode stack, for example, comprising a plurality of sheets. The plurality of sheets may comprise an anode, a cathode, and a separator for separating the anode from the cathode, thereby providing the electrode assembly 106 with its ability to store electrical energy. The electrode assembly 106 may comprise, at a first side 106a thereof, a connective tab 108 for electrically connecting to other components of the cell 100. In this example, the electrode assembly 106 has a substantially rectangular profile similar to that of the casing 102. Although not shown, the electrode assembly has a second side opposite to the first side 106a. There is also a third side 106b extending from the first side 106a to the second side, adjacent to the lid 102a and the terminals 104 extending through the lid 102a, and a fourth side (also not shown) opposite to the third side 106b. The electrode assembly 106 may also be considered as planar, or as extending along a plane through the cell 100.

[0043] The connective tab 108 may be an extension from the roll or stack of one or more electrode sheets respectively, which may optionally be provided with notches, feathering, or some other processing to further facilitate the connection of the connective tab 108 to other electrical components. In some variants, the entire length of the uncoated region of the electrode sheet forms the tab, without any notching being performed.

[0044] In some examples, the one or more electrode sheets have a plurality of sheet tabs, each sheet tab formed as an extension from the roll or stack of one or more electrode sheets. In particular, the sheet tabs may be formed from the foil that acts as a substrate in the electrode sheet. The foil may comprise, or consist of, a metal such as copper or aluminium. Typically, an anode (negative electrode) foil will comprise, or consist of, copper, whereas a cathode (positive electrode) foil will comprise, or consist of, aluminium. All the sheet tabs of the plurality of sheet tabs may be joined together to form the connective tab 108. In other words, the connective tab 108 may be considered as a plurality of joined sheet tabs. The sheet tabs may be joined by a welding process or by some other suitable process which may involve the use of an electrically conductive glue, or a physical process such as clamping or crushing. For example, particularly if the terminal 104 is the positive terminal, the connective tab 108 be formed from a plurality of aluminium foils joined together.

[0045] The cell 100 may be further provided with one or more spacers (not shown), some of which being electrical insulators, for appropriately spacing, retaining, etc. internal components of the cell 100 in their respective desired positions, and / or electrically insulating internal components of the cell 100 from each other or from the casing 102.

[0046] The electrode assembly 106 may be connected to the terminal 104 via a current collector 200. The current collector 200 may form a current path between the electrode assembly and the terminal 104, thus enabling the transfer of electrical current from the electrode assembly to the terminal. The current collector may be formed from any suitable material such as zinc, steel, copper, aluminium, etc., although the choice of material may further depend on whether the current collector 200 is connecting the anode side or the cathode side of the cell 100.

[0047] In this example, the current collector 200 extends from the terminal 104 at the third side 106b to the connective tab 108 at the first side 106a. However, it will be appreciated that the current collector may have a different configuration depending on the respective locations of the terminal 108 and the connective tab 108. The current collector 200 may comprise a weld surface 202 against which the connective tab 108 may be welded. In this example, the weld surface 202 is a planar surface extending substantially parallel to the electrode assembly 106.

[0048] When charging or discharging the cell 100, current may flow between the terminal 104 and the electrode assembly 106 via the current path created by the current collector 200.

[0049] A weld structure 204 fixes the connective tab 108 to the current collector 200. The weld structure 204 extends along a connection axis substantially parallel to the first side 106a of the electrode assembly 106.

[0050] Various examples of the weld structure are shown in Figures 3 to 10. Figure 3 shows a weld structure 204a comprising a plurality of weld lines 300.

[0051] A weld line is a line of fused material formed by exposing that line of material to a welding process. For example, the welding process may be a laser welding process wherein a beam of energy is directed at the material to be welded, the beam moving relative to the target material such that a line of material is welded.

[0052] The weld lines 300 are spaced apart from one another by a gap 310 and are oriented substantially perpendicularly to the connection axis 206, i.e. the axis along which the weld structure 204a extends.

[0053] The orientation of the weld lines 300 to be substantially perpendicular to the connection axis 206 is counter intuitive as it is more time consuming than providing a weld structure that extends over a similar area with weld lines extending substantially parallel to the connection axis 206.

[0054] However, welding processes involve exposing the conductive tab to high temperatures which can lead to the formation of heat cracks, especially the top layers of sheet tabs that are being welded as they are exposed to the highest temperatures. Further, the inventors have identified that those heat cracks tend to follow the direction of the weld lines. Accordingly, weld lines that extend parallel to the connection axis risk causing the generation of heat cracks that also run parallel to the connection axis. This can result in a significant reduction in the tensile strength and electrical conductivity of the connection between electrode and current collector and, in some cases, cause the electrical connection to be entirely severed, rendering the electrode useless and reducing the performance of the battery cell.

[0055] By counter-intuitively inclining the weld lines 300 away from the connection axis 206, the risk of heat cracks forming in such a way as to sever the electrode from the current collector is greatly reduced.

[0056] In this example, the weld lines 300 also extend substantially parallel to one another. Configuring the weld lines 300 to be substantially parallel may enable a more consistent spacing between weld lines 300, which may in turn provide more consistent electrical conduction through the weld structure 204a. Providing the weld lines 300 substantially in parallel to one another may also make the manufacturing process more straight forward. Nevertheless, in other examples, the weld lines may be non-parallel. The spacing between the weld lines 300 may be optimised according to a number of factors. Firstly, a greater the density of fused material within the weld structure 204a will result in a lower electrical resistance, which is desirable for the performance of the battery cell. However, the performance benefit of including many weld lines that are very closely spaced must be balanced against providing an efficient manufacturing process as increasing the number of weld lines will require more time and energy consumption to complete the welding process. There is also a risk that the advantage of orienting the weld lines away from the connection axis could be reduced if the weld lines are so close together that they facilitate heat crack propagation in the direction of the connection axis or the generation of so many heat cracks that the tensile strength and structural integrity of the sheet tabs is diminished.

[0057] The gap 310 between adjacent weld lines 300 may be determined as a fraction or percentage of the length (longitudinal dimension) of the weld structure 204a. For example, the gap 310 may be between 0.2% and 20% of the length of the weld structure, optionally between 0.5% and 10% of the length of the weld structure, such as between 1% and 5% of the length of the weld structure.

[0058] Alternatively, the gap 310 may be considered independently of the overall weld structure. For example, the gap 310 may be at least 0.1 mm, optionally at least 0.2 mm, such as at least 0.3 mm.

[0059] In the example shown in Figure 3, there is a total of 30 weld lines. In other examples, there may be more weld lines, and in further examples there may be fewer weld lines.

[0060] Figure 4 shows a weld structure 204b comprising a plurality of weld lines 400.

[0061] Rather than being oriented substantially perpendicular to the connection axis 206, the weld lines 400 are inclined at an angle 412 to the connection axis 206. In this example, the angle 412 is 45°.

[0062] To avoid the formation of heat cracks that sever an electrode, the angle 412 may be at least 20 degrees from the connection axis 206, optionally at least 45 degrees from the connection axis 206, such as at least 75 degrees from the connection axis 206. In some examples, such as that shown in Figure 1, the angle may be substantially 90 degrees from the connection axis 206. Figure 5 shows a weld structure 204c comprising a plurality of weld lines 500. The plurality of weld lines includes a first subset 502 of weld lines and a second subset 504 of weld lines wherein the weld lines alternate between the first and second subsets 502, 504 throughout the plurality of weld lines.

[0063] The weld structure 204c may be considered similar to the weld structure 204a shown in Figure 3 in that the weld lines 500 extend perpendicular to the connection axis 206. However, in weld structure 204c, the weld lines 500 are out of alignment. More particularly, if each weld line is considered as having a first end and an opposite second end, the first ends of weld lines in the first subset 502 are out of alignment with the first ends of weld lines in the second subset 504. Further, in this example, the second ends of weld lines in the first subset 502 are also out of alignment with the second ends of weld lines in the second subset 504. The nonalignment between weld lines of the first and second subsets is provided by a lateral offset 514 between a first ends of weld lines in the first subset and the first ends of a weld lines in the second subset 504.

[0064] By laterally offsetting the weld lines 500 from one another the spacing between weld lines in regions close to the edges of the weld structure 204c is increased. This may be beneficial as it is the regions close to the edges of the weld structure 204c where propagation of heat cracks can be most harmful, especially if a number of heat cracks join together, which would increase the risk of the respective electrode being severed from the current collector.

[0065] Accordingly, introducing the lateral offsets allows electrical conduction through the weld structure to be substantially maintained while reducing the likelihood that heat cracks join and grow. Alternatively, the risk of heat cracks joining can be maintained at an acceptable level while improving the conduction performance of the weld structure by positioning weld lines closer together.

[0066] Increasing the lateral spacing between adjacent weld lines may reduce the likelihood that heat cracks join and grow. However, increasing the lateral spacing will also slightly reduce the density of fused material within the weld structure and therefore slightly increases electrical resistance. It is therefore necessary to find a compromise between preventing heat crack formation and electrical performance, which may be dependent on factors such as the size of the area available for the weld structure and the various materials involved. With reference to Figure 2, the nonalignment of the ends of the weld lines may be particularly beneficial on the side of the weld structure 204 proximal to the electrode assembly 106, i.e. the side between the electrode assembly and the current collector. Accordingly, in some examples, it may be that only first ends of the weld lines, arranged proximally to the electrode assembly, are configured to be out of alignment.

[0067] Figure 5 shows just one example of a weld structure 204c including weld lines with ends that are out of alignment with one another. However, it will be appreciated that lateral offsets may be provided in many variations other than an alternating pattern and still achieve the same effect of taking the ends of the weld lines out of alignment from one another. For example, Figure 6 shows a weld structure 204d in which weld lines from a first subset 602 of weld lines are offset from weld line belonging to a second subset 604 of weld lines by a gap X in a first lateral direction. Meanwhile, a weld lines from a third subset 606 of weld lines are offset from the weld lines of the second subset 604 by the same gap X in the opposite lateral direction. Accordingly, the weld lines of the first and third subsets 602, 606 are offset from one another by a gap 2X.

[0068] Meanwhile, Figure 7 shows a weld structure 204e in which the weld lines 700 are out of alignment from one another to the extent that a first subset 702 of weld lines may be considered as a first column of weld lines 700 and a second subset 704 of weld lines may be considered as a second column of weld lines. The lateral offset between the first and second subsets 702, 704 is sufficiently large that the entire first column is laterally spaced apart from the entire second column.

[0069] Figure 8 shows a weld structure 204f comprising a first plurality of weld lines 800 and a second plurality of weld lines 802 that is spaced apart from the first plurality of weld lines 800. In this example, each of the first and second pluralities of weld lines comprise ten weld lines in total.

[0070] The space 818 between the first and second pluralities of weld lines 800, 802 may act as a buffer to separate heat cracks formed by the first plurality of weld lines 800 from heat cracks formed by the second plurality of weld lines 802, thereby further reducing the likelihood that an electrode is severed from the current collector. However, it will be appreciated that there will be increased electrical resistance in the region of the end structure 204e having no weld lines. In this example, the space 818 extends over about a third of the length of the weld structure 204e. However, a space between pluralities of weld lines may be smaller in other instances. For example, the space may be at least 5% of the longitudinal dimension, optionally at least 10% of the longitudinal dimension, such as at least 20% of the longitudinal dimension.

[0071] Figure 9 shows a weld structure 204g that combines weld lines 900, 902 extending perpendicular to the connection axis 206 and weld lines 904 that are inclined at an acute angle relative to the connection axis 206. In particular, the weld structure 204f comprises a first plurality of weld lines 900 positioned at one end of the weld structure 204f and a second plurality of weld lines 902 positioned at the opposite end of the eld structure 204g. However, rather than the space between the first and second pluralities of weld lines 900, 902 being entirely absent of any further weld lines, there is a third plurality of weld lines 904 that extend diagonally across the region between the first and second pluralities of weld lines 900, 902.

[0072] The weld structure 204g therefore benefits from spacing between weld lines to act as a buffer that separates propagated heat cracks from one another (similarly to the example shown in Figure 8) while also having at least some fused material extending almost entirely through the length of the weld structure 204g such that electrical performance is not unduly sacrificed.

[0073] Figure 10 shows a weld structure 204h comprising a first plurality of weld lines 1000 positioned at one end of the weld structure 204h, a second plurality of weld lines 1002 positioned at the opposite end of the weld structure 204h and a third plurality of weld lines 1004 positioned in between the first and second pluralities of weld lines 1000, 1002. The weld lines 1000, 1002, 1004 within each of the first, second and third pluralities of weld lines are laterally offset from one another. In between the first second and third pluralities of weld lines 1000, 1002, 1004, there are auxiliary weld lines 1018 extending along or parallel to the connection axis 206.

[0074] Although the auxiliary weld lines 1018 would be problematic if they were provided in isolation, the provision of the first second and third pluralities of weld lines 1000, 1002, 1004 extending substantially perpendicular to the auxiliary weld lines 1018 may act as a barrier to prevent the heat cracks propagated by the auxiliary weld lines 1018 from spreading too far. It will be appreciated that the different features of the various weld structures shown in Figures 3 to 10 may be interchanged and / or combined with one another to form further weld structures.

[0075] Figure 11 shows steps of a method 2 of manufacturing a battery cell such as the battery cell 100 shown in Figure 1. (For illustrative purposes only, reference is made to the features shown in Figures 1, 2 and 3.)

[0076] The method 2 comprises providing 4 an electrode assembly 106 having a connective tab 108 extending from a first side 106a of the electrode assembly 106. A following step is welding 6 the connective tab 108 to a current collector 200 so as to form a weld structure 204 fixing the connective tab 108 to the current collector 200. The weld structure 204 extends along a connection axis 206 substantially parallel to the first side 106a of the electrode assembly 106 and comprises a first plurality of weld lines 300. The weld lines are spaced apart from one another and inclined relative to the connection axis 206. A further step of the method 2 involves coupling 6 the current collector 200 to a terminal 104 to enable transfer of electrical current from the electrode assembly 106 to the terminal 104.

[0077] In some examples, the step of welding 4 the connective tab 108 to the current collector 200 comprises using a laser welding technique to fuse the connective tab 108 to the current collector 200.

[0078] In further examples, the step of welding 4 the connective tab 108 to the current collector 200 comprises sequentially welding the weld lines 300 of the first plurality of weld lines.

[0079] In one example, one or more instructions or steps discussed herein are automated. Thus, performing the method may include controlled operation of an apparatus, system, and / or process using computers and / or mechanical / electrical devices without the necessity of human intervention, observation, effort and / or decision.

[0080] It will be appreciated that any components said to be coupled may be coupled or connected either directly or indirectly. In the case of indirect coupling, additional components may be located between the two components that are said to be coupled.

[0081] In this specification, example embodiments have been presented in terms of a selected set of details. However, a person of ordinary skill in the art would understand that many other example embodiments may be practiced which include a different selected set of these details. It is intended that the following claims cover all possible example embodiments.

Claims

CLAIMS1. A battery cell comprising: a terminal; an electrode assembly having a connective tab extending from a first side of the electrode assembly; a current collector connecting the terminal to the electrode assembly via the connective tab to enable transfer of electrical current from the electrode assembly to the terminal; a weld structure fixing the connective tab to the current collector, the weld structure extending along a connection axis substantially parallel to the first side of the electrode assembly and comprising a first plurality of weld lines, the weld lines being spaced apart from one another and inclined relative to the connection axis.

2. The battery cell of claim 1, wherein the weld lines are oriented at least 20 degrees from the connection axis, optionally oriented at least 45 degrees from the connection axis, alternatively at least 75 degrees from the connection axis, such as substantially 90 degrees from the connection axis.

3. The battery cell of claim 1 or claim 2, wherein each weld line extends from a first end to a second end and the first plurality of weld lines comprises at least a first subset of weld lines and a second subset of weld lines, and wherein the first ends of the weld lines in the first subset of weld lines are out of alignment with the first ends of the weld lines within the second subset of weld lines.

4. The battery cell of claim 3, wherein the weld structure extends over an area having a lateral dimension, and the first ends of the weld lines of the first subset of weld lines are laterally offset from the first ends of the weld lines of the second subset of weld lines by at least 5% of the lateral dimension, optionally at least 10% of the lateral dimension, alternatively at least 20% of the lateral dimension.

5. The battery cell of any preceding claim, wherein adjacent weld lines of the first plurality of weld lines are spaced apart by at least 0.1 mm, optionally at least 0.2 mm, alternatively at least 0.3 mm.

6. The battery cell of any preceding claim, wherein the first plurality of weld lines includes at least 10 weld lines, optionally at least 30 weld lines.

7. The battery cell of any preceding claim, wherein the weld structure further comprises a second plurality of weld lines spaced apart from the first plurality of weld lines.

8. The battery cell of claim 7, wherein the weld structure extends over an area having a longitudinal dimension, and the first plurality of weld lines is spaced apart from the second plurality of weld lines by at least 5% of the longitudinal dimension, optionally at least 10% of the longitudinal dimension, alternatively at least 20% of the longitudinal dimension.

9. The battery cell of any preceding claim, wherein the connective tab comprises or consists of aluminium.

10. The battery cell of any preceding claim, wherein the electrode assembly comprises a roll or stack of one or more electrode sheets having a plurality of sheet tabs, each sheet tab formed as an extension from the roll or stack of one or more electrode sheets; and wherein all the sheet tabs of the plurality of sheet tabs are joined together to form the connective tab.

11. The battery cell of any preceding claim, wherein : the electrode assembly has a substantially rectangular profile and further comprises a second side opposite to the first side, a third side extending from the first side to the second side and a fourth side opposite to the third side; the terminal is arranged adjacent to the third side; and the current collector assembly extends from the terminal at the third side to the connective tab at the first side.

12. The battery cell of any preceding claim, wherein the electrode assembly is planar, the current collector comprises a planar weld surface that extends substantially parallel to the electrode assembly, and the weld structure fixes the connective tab to the current collector via the weld surface.

13. A method of manufacturing a battery cell, the method comprising : providing an electrode assembly having a connective tab extending from a first side of the electrode assembly; welding the connective tab to a current collector so as to form a weld structure fixing the connective tab to the current collector, the weld structure extending along a connection axis substantially parallel to the first side of the electrode assembly andcomprising a first plurality of weld lines, the weld lines being spaced apart from one another and inclined relative to the connection axis; and coupling the current collector to a terminal to enable transfer of electrical current from the electrode assembly to the terminal.

14. The method of claim 13, wherein the step of welding the connective tab to the current collector comprises using a laser welding technique to fuse the connective tab to the current collector.

15. The method of claim 13 or claim 14, wherein the step of welding the connective tab to the current collector comprises sequentially welding the weld lines of the first plurality of weld lines.

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