Method of producing battery cell TABS with improved adhesion capability

Abstract

A method of manufacturing a lead tab for a battery cell comprises supplying a metallic substrate, irradiating the surface of the metallic substrate with pulsed laser light to create formations in the substrate and / or to modify the chemical composition the substrate. Polymer strips are adhered to the resulting metallic substrate in order to incorporate the substrate into the battery cell as a lead tab. The formations in, and / or chemical modification of, the substrate improve the adhesion of the substrate to the polymer strips and may provide an anti-corrosive layer.

Description

[0001] METHOD OF PRODUCING BATTERY CELL TABS WITH IMPROVED ADHESION CAPABILITY

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to improving adhesion between metallic surfaces and polymer surfaces. The invention relates particularly, but not exclusively, to the production of electrically conductive tabs for battery cells, and more particularly to improving adhesion between electrically conductive tabs and polymer elements of battery cells.

[0004] BACKGROUND TO THE INVENTION

[0005] It is known for battery cells to have a positive terminal and a negative terminal each comprising an electrically conductive tab for connecting the battery cell to a load. It is desirable to provide a seal around the tabs in order to prevent or inhibit leakage of fluid or other material from the battery cell. To this end, the tabs are typically adhered to one or more polymer strip or other polymer element(s). A pouch cell is an example of a type of battery cell having such a configuration. The battery cell components (typically comprising lithium-ion cell components) are enclosed in a pouch, each tab being electrically connected to the respective electrode of the cell within the pouch and protruding from the pouch for connection to a load. The pouch is sealed around the tabs to prevent leakage. The tabs may be adhered to the pouch and / or to polymer strip(s) provided between the tabs and the pouch. The pouch is typically formed from an aluminium-polymer film (e.g. aluminium-plastic film). The tabs may be formed from metallic foil.

[0006] Conventionally, for the enhancement of corrosion protection, the metallic tabs are coated with a chromium surface treatment by initially cleaning the metal surface with acidic and / or alkaline solutions followed by contacting the metal surface with an aqueous solution of trivalent or hexavalent chromium. Trivalent chromium coatings are a very common corrosion inhibition method and are considered a safer and more environmentally friendly alternative to hexavalent chromium treatments. However, chemical coatings are generally undesirable not only because they tend not to be environmentally friendly, but also because they increase the electrical resistance of the tab (which reduces the tab’s efficiency for transferring electrical energy to the load).

[0007] It would be desirable therefore to provide an alternative solution for adhering the tabs to the polymer material, advantageously without chemically coating the tabs. More generally it would be desirable to provide an improved method of adhering metallic substrates to polymer material, advantageously without chemically coating the metallic substrate.

[0008] SUMMARY OF THE INVENTION

[0009] One aspect of the invention provides a method of manufacturing a conductive tab for a battery cell, the method comprising: supplying a metallic substrate; irradiating at least one region of at least one surface of the metallic substrate with pulsed laser light to create formations in said metallic substrate in said at least one region, and / or to modify the chemical composition of said metallic substrate in said at least one region. The resulting metallic substrate may be used as a battery lead tab, typically being adhered to one or more polymer strip as described in more detail hereinafter.

[0010] From another aspect the invention provides a method of processing a metallic substrate to improve adhesion with a polymer element or surface and / or to create an anti-corrosive region, the method comprising: supplying a metallic substrate; irradiating at least one region of at least one surface of the metallic substrate with pulsed laser light to create formations in said metallic substrate in said at least one region, and / or to modify the chemical composition of said metallic substrate in said at least one region.

[0011] Creating said formations preferably involves creating uniform or substantially uniform formations, preferably creating said formations with uniform or substantially uniform depth, and / or size, and / or spacing, and / or shape.

[0012] Preferably, said formations are microscale formations, preferably having one or more dimension of 0.01 -100pm. In preferred embodiments the method includes forming said formations in said at least one surface with a depth of at least 0.01 pm, said depth preferably being uniform or substantially uniform.

[0013] Typically, the, or each, of said at least one region corresponds to a respective region to which a polymer element is to be fixed, and wherein, preferably, said formations cover at least 95% of the respective region.

[0014] Optionally, modifying the chemical composition of said metallic substrate involves increasing the oxygen content of said metallic substrate in said at least one region to at least 1%.

[0015] In preferred embodiments, said irradiating involves creating a modified layer in said metallic substrate in said at least one region, wherein said formations are created in said layer and / or said chemical composition is modified in said layer, and wherein said layer has a depth of at least 0.01 pm, and said depth is preferably uniform or substantially uniform.

[0016] In preferred embodiments the, or each, of said at least one region corresponds to a respective region to which a polymer element is to be fixed, and wherein, preferably, said chemical composition is modified over at least 95% of the respective region.

[0017] In preferred embodiments, a fibre laser device is used to perform said irradiating.

[0018] Typically, said pulsed laser light has a pulse energy between 1 pj and 100 mJ inclusive, preferably 10 pJ to 10 mJ. Typically, said laser light has a wavelength between 0.1 - 10 pm, preferably 780- 2200 nm. Typically, said pulsed laser light has a pulse duration of 1 ps or less, preferably 0.1 -300 ns, more preferably 0.1 -100 ns. Typically, said pulsed laser light is produced by a laser device having an operating frequency between 1 - 50,000 kHz.

[0019] Typically, said irradiating involves scanning said pulsed laser light with respect to said metallic substrate. Said pulsed laser light may be scanned with a translational speed of between 100 - 200,000 mm / s, preferably 500-5000 mm / s. Preferably, said pulsed laser light is scanned with a constant, or substantially constant, hatch distance. Preferably, said pulsed laser light is scanned to provide a one or two dimensional array of laser spots on the substrate surface, and wherein the hatch distance is preferably uniform, or substantially uniform, between adjacent laser spots in the, or each, dimension of the array. Preferably said pulsed laser light is scanned with a hatch distance that causes adjacent laser spots overlap, preferably in the or each dimension of the scanning spot array. Typically, said pulsed laser light is scanned with a hatch distance of 0.005-0.05 mm. Preferably, said pulsed laser light is scanned with a constant, or substantially constant, scanning or translational speed.

[0020] Preferably, said pulsed laser light is scanned with an average coverage that is constant or substantially constant, wherein: average coverage = translational speed x hatch distance. In preferred embodiments, said pulsed laser light is scanned with an average coverage of 5-100 mm2.

[0021] Preferably, said pulsed laser light has a pulse energy that is constant or substantially constant.

[0022] In some embodiments, the method includes controlling at least one parameter of said pulsed laser light to create said formations and / or to modify said chemical composition, wherein said at least one parameter preferably includes a pulse energy of said pulsed laser light and / or a pulse duration of said pulsed laser light.

[0023] The method may include controlling the pulse duration and the pulse energy of said pulsed laser light to cause one or more desired change in said chemical composition. The method optionally includes controlling the pulse duration and the pulse energy of said pulsed laser light to increase an oxygen content in said at least one region to a desired level, preferably at least 1%.

[0024] In some embodiments, said irradiating involves scanning said pulsed laser light with respect to said metallic substrate, the method further including controlling a scanning speed, or translational speed, of said pulsed laser light to create said formations and / or to modify said chemical composition, and / or controlling an average coverage of said pulsed laser light to create said formations and / or to modify said chemical composition. Optionally, the method includes controlling said translational speed and / or average coverage to cause said at least one region to exhibit an adhesion strength of a desired level, preferably at least 5N.

[0025] In some embodiments, said metallic strip is formed from aluminium or an aluminium alloy, and wherein modifying the chemical composition preferably involves forming aluminium oxide and / or mixed metal oxides. In some embodiments, said metallic strip is formed from copper or nickel-plated copper.

[0026] In some embodiments, the method includes aligning a respective polymer element, for example a polymer strip, with the, or each, of said regions, and causing said polymer element to adhere to the respective region, preferably by heating.

[0027] From another aspect the invention provides a method of manufacturing a pouch cell comprising battery components located in a pouch, said battery components including an anode and a cathode, said method comprising electrically connecting a respective lead tab to said anode and said cathode such that each lead tab protrudes from said pouch, wherein each lead tab is manufactured by the method of the first aspect, and wherein said method further includes: aligning a respective polymer element, for example a polymer strip, with the, or each, of said regions of each lead tab, and causing said polymer element to adhere to the respective region, preferably by heating; and sealing said pouch around said lead tabs.

[0028] Preferred embodiments of the invention involve the creation of one or more laser-processed region, which may be said to comprise a modified region and / or conversion layer, on a metal substrate (e.g. the energy transfer tab or strip of a battery cell) to increase adhesion between the energy transfer tab, or other metallic substrate, and one or more polymer element, e.g. one or more polymer strip for providing a seal around the tab.

[0029] Preferred embodiments involve laser processing that results in surface chemical and topographical modifications to the metallic substrate. In preferred embodiments the metal substrate comprises or consists of one or more of the following metals; Li, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Sn, W and alloys thereof. The preferred laser processing method irradiates a predetermined region of the metallic substrate, advantageously to form a uniformly modified region efficiently in terms of shape, depth, morphology and composition of conversion. The preferred laser surface treatment creates a uniformity to the modified region, which may comprise a conversion layer, with excellent repeatability and results in a region of surface-treated substrate, specifically suited for polymer adhesion. The modified region may comprise a layered composition consisting of one or more compound such as, but not limited to, metal oxides and / or mixed oxides, covering the parent metallic substrate. For example if the substrate is formed from a metal alloy a mixed oxide rather than a particular metal oxide may be formed, e.g. some grades of steel form FeO and Fe2C>3with a generic composition of Fe3O4which is a mixed oxide. Advantageously, these complexes alone or in combination with other components improve corrosion resistant properties, typically chemical and / or electrochemical activity over the parent substrate, as well as improved adhesion properties to both low and high surface energy materials without the requirement for subsequent treatment or coating steps.

[0030] Optionally, the modified, region on the parent substrate, comprising one or more layers of discrete compounds, is created using a pulsed laser light system to form a corrosion-inhibiting layer. Optionally, the modified region on the parent substrate, comprising one or more layers of discrete compounds, is created using a pulsed laser light system to form a protective layer against atmospheric conditions. Optionally, the substrate is not pre-treated before laser processing. Alternatively, the substrate is cleaned under acidic conditions or under alkaline conditions before laser processing. Optionally the substrate is plated with another metal before laser processing.

[0031] In some embodiments, layered compounds are provided on the parent substrate, in particular at the modified region, having a corrosion-inhibiting composition top layer and metallic sub-layer, which makes the substrate suited for use in energy storage devices. Advantageously, the corrosioninhibiting layer may be fixed to, or combined with, a polymer element or strip to form a lead tab for use in a battery cell or other electrical energy storage device.

[0032] In preferred embodiments, the layered compounds described herein have excellent corrosion resistance performance, whilst enhancing adhesion properties. The modified substrates are useful in many industries, including, but not limited to, energy storage devices.

[0033] In some electrical energy storage devices, including some battery cells (e.g. pouch cells), electrical energy is transferred from the storage device to a load via one or more conductive metallic element, typically a metallic strip, that is commonly referred to as a lead tab. The metallic strip may be fixed to a polymer strip by any suitable conventional heat sealing method, and the resulting lead tab may be combined with other components of the energy storage device. Advantageously, a conversion layer (or laser-modified region) is prepared on the metallic substrate at the, or each, location at which the tab is fixed to the polymer strip, while the rest of the tab preferably remains untreated, or unmodified. The conversion layer is advantageously formed by a laser treatment, wherein a pulsed laser beam is radiated onto the metallic substrate at the desired location(s) to produce the laser- modified region(s). The pulsed laser beam parameters may be defined for specific surface chemistry and topographical features, thus ensuring effectiveness of the modified layer for predetermined application(s).

[0034] In preferred embodiments, a strong adhesive bond is created between the metal and the polymer, which is advantageously used to fix the metal energy transfer strip, or tab, in place within a battery cell.

[0035] Preferred embodiments involve laser processing that results in surface modifications to metallic substrates to develop layered substrates with preferred physical, chemical and electrochemical properties. In preferred embodiments the metal substrate comprises or consists of one or more of the following metals: Li, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Sn, W and alloys thereof.

[0036] Polymers used in the production of lead tabs (e.g. to provide the polymer strip(s) or other polymer element(s) that are fixed to the metallic strip) are electrically insulating to prevent cell shortages. Polymers such as, but not limited to, polyethylene, polypropylene and polyurethane are typically used, with or without filler materials such as, but not limited to, ceramic oxides, carbonates and hydrates. Advantageously, the conversion treatment of the metallic substrate can improve corrosion resistance of the substrate as well as promoting adhesion with improved topographical properties, or aid in chemical, and / or electrochemical activity.

[0037] Advantageously, the laser-modified region(s) of the metallic substrate provide strong adhesion with the polymer strip(s) or other polymer element(s), and optionally also anti-corrosive properties, without additional coating(s), e.g. formed by electroplating, being applied to the substrate or tab.

[0038] It will be understood that the invention is not limited to battery lead tabs and that any aspects or features of the invention disclosed herein may be used in any application involving creating or improving adhesion between metallic surfaces and polymer surfaces.

[0039] Further advantageous aspects of the invention will be apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments and with reference to the accompanying drawings.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the invention are now described by way of example and with reference to the accompanying drawings in which like numerals are used to denote like parts and in which:

[0042] Figure 1 is a schematic view of a battery cell, in particular a battery cell of a type known as a pouch cell;

[0043] Figure 2 shows a laser source directing a laser beam onto a metallic substrate to form a modified region, comprising a conversion layer, at the surface of the metallic substrate, wherein the metallic substrate may be an energy transfer tab of the battery cell of Figure 1 ;

[0044] Figure 3 shows the metallic substrate of Figure 2 including a laser-processed region (comprising the conversion layer) and non-laser-processed regions;

[0045] Figure 4 shows the metallic substrate of Figure 3 with a polymer element fixed to the laser- processed region; and

[0046] Figure 5 shows the metallic substrate of Figure 4 fixed to the current collector foil or stack of foils of the battery cell.

[0047] DETAILED DESCRIPTION OF THE DRAWINGS

[0048] Referring now to Figure 1 of the drawings, there is shown, generally indicated as 10, an energy storage device in the form of a battery cell. In typical embodiments, the cell 10 is a lithium-metal battery, a lithium-ion battery or a lithium-ion polymer battery, and may be rechargeable or non- rechargeable as applicable. The cell 10 shown in Figure 1 is of a type commonly referred to as a pouch cell. The cell 10 comprises a stack 12 of cell components, typically Li-ion cell components, located inside a pouch 13 (in Figure 1 the stack 12 is shown partially protruding from the pouch for illustrative purposes). The pouch 13 is typically formed from an aluminium-polymer film (e.g. aluminium-plastic film). The stack 12 comprises current collectors 14, typically in the form of foils, sheets or other layers, formed from electrically conductive material (e.g. copper or aluminium). The current collectors 14 comprise an anode 14A and a cathode 14C separated by a separator 14B, which is a membrane or layer that prevents electrical contact between the anode 14A and the cathode 14C. The current collectors 14 are typically coated in a suitable active material (e.g. lithium- metal oxide for the cathode 14C and graphite for the anode 14A) to facilitate their use as electrodes. The specific configuration of the stack 12 may vary from cell to cell and may comprise additional layers as would be apparent to a skilled person. A respective electrically conductive element 16A, 16C, commonly referred to as a tab, a cell tab or a lead tab, is connected to the anode 14A and the cathode 14C. The tabs 16A, 16C may be connected to the respective electrode 14A, 14C by any convenient means, e.g. ultrasonic welding or other conventional welding. The tabs 16A, 16C typically comprise a metallic strip, e.g. formed from aluminium or copper. The tabs 16A, 16C provide the means for transferring electrical energy to and from the cell 10, as applicable, and may therefore be connected to an electrical load or charger as required. To this end, when the stack 12 is located within the pouch 13, the tabs 16A, 16C protrude from the pouch 13. The pouch 13, in particular its open mouth, is sealed around the tabs 16A, 16C in order to protect the cell components within the pouch 13 and prevent leakage of fluid or other material from the pouch 13. To facilitate sealing the pouch 13 around the tabs 16A, 16C, each tab 16A, 16C may be provided with one or more element or strip 18 of polymer material (e.g. polyethylene, polypropylene and polyurethane, with or without filler materials such as, but not limited to, ceramic oxides, carbonates and hydrates). The or each polymer element or strip 18 may take the form of a polymer film. In Figure 1 a respective polymer strip 18 is shown on the obverse face of the tabs 16A, 16C, and an identical or similar polymer strip (not visible) may also be provided on the reverse face of each tab 16A, 16C in register with the respective strip 18 on the obverse face. The pouch 13 may be sealed around the tabs 16A, 16C using any conventional sealing process, e.g. heat sealing, and this is facilitated by the polymer strips 18. Alternatively, the pouch 13 may include one or more polymer elements at location(s) where the pouch 13 is to be sealed around the tabs 16A, 16C, in which case the pouch 13 may be sealed directly to the tabs 16A, 16C at these location(s). In any event, it is desirable to provide strong adhesion between the polymer elements and the tabs 16A, 16C, and preferably also a bond with anti-corrosive properties.

[0049] In preferred embodiments, prior to fixing the polymer strip(s) 18 to the metallic strip of the tabs 16A, 16C, one or more region of the metallic strip is subjected to laser texturing, and / or other laser processing, using a pulsed laser beam. The or each region that is laser textured or processed (which may be referred to as a modified region) is provided at a location where it is intended to fix a respective polymer strip 18 or other polymer element. As is described in more detail hereinafter, when the polymer is fixed to the metallic strip at the modified region, the modified region provides strong adhesion between the polymer and the metallic strip, and may also provide a good anticorrosive barrier. More generally, and with reference in particular to Figures 2 to 5, preferred embodiments of the invention involve the formation of one or more modified region 20 on a metallic substrate 16, typically a metallic strip or tab, that is particularly, but not exclusively, used as a battery tab. The, or each, modified region 20 is provided at a location of the metallic substrate to which a polymer element, typically a polymer strip 18, is to be adhered. Modified region(s) 20 may be provided on one face of the metallic substrate, or on multiple faces, as required. For example, modified region(s) 20 may be provided on an obverse face 22 and / or a reverse face 23. In embodiments in which modified regions 20 are provided on both the obverse face 22 and reverse face 23 of the substrate, the modified region(s) on the reverse face 23 is / are preferably in register, or aligned with, the respective modified region(s) 20 on the obverse face 22. Preferably, a modified region is provided on one or more edge 24 of the metallic substrate, preferably in register with, or aligned with, the or each modified region 20 on one or more face of the substrate, e.g. the obverse and / or reverse face. The preferred arrangement results in one or more modified region that extends in a band, preferably a continuous band, around the substrate 16.

[0050] Figure 2 shows a laser source 30 producing a laser beam 32 that is incident on the parent metallic substrate 16. The corresponding modified region 20, which may comprise a conversion layer, is formed at the surface 22 of the substrate 16 as a result of the incident laser beam 32. The laser source 30 may comprise any conventional laser device. In preferred embodiments, the laser source 30 comprises a fibre laser device. A fibre laser is a laser in which the active gain medium comprises one or more optical fibre.

[0051] Advantageously, only the, or each, region of the substrate 16 that is intended for adherence with a polymer element 18 is laser treated to form a modified region 20. It is preferred that the remainder of the substrate 20, in particular the remainder of its obverse and reverse faces 22, 23, is not laser treated, and is preferably otherwise untreated or unmodified, e.g. consists of only the untreated or unprocessed metallic substrate itself (e.g. without being coated or textured). In Figures 3 to 5, such untreated, or unmodified, regions are indicated by reference numeral 34. It is advantageous to leave the remainder of the substrate 16 untreated or unmodified so as not to further comprise the ability of the metal substrate to transfer electrical power.

[0052] Preferably, the size of the, or each, modified region 20 matches or substantially matches the size of the corresponding polymer element 18 that is to be fixed to it. In particular it is preferred that the surface area of the, or each, modified region 20 matches or substantially matches the corresponding area of the corresponding polymer element 18 that is to be fixed to it. While an exact match in size is preferred, it is not essential. For example, as is illustrated in Figures 4 and 6, the size (in particular the surface area) of the modified region 20 does not exactly match the size of the portion of the polymer strip 18 attached to it (in particular the modified region 20 is larger, or wider, than the relevant portion of the strip 18), although the respective sizes substantially match. It is preferred that there is a full overlap between the portion of the polymer element 18 that is to be adhered to the surface 22 of the metallic strip 16 and the respective modified region 20, and this may be facilitated by making the modified region 20 larger, or wider, than the relevant portion of the polymer element 18. In typical embodiments, the polymer element 18 is a polymer strip that is disposed perpendicularly, or substantially perpendicularly, to the metallic substrate 18, which is typically also in strip form, the polymer strip 18 extending laterally beyond the metallic strip 18 at each side.

[0053] By way of example, in typical embodiments the substrate 16 comprises a strip or tab having a width of 5-90 mm, a thickness of 0.1 -1 mm and a length of 25-60 mm. The polymer strip 18 may have a width of 10-100 mm, a thickness of 0.1 -0.2 mm and a length of 5-15 mm. The modified region 20 may have a width of 5-90 mm, a thickness of less than 0.1 mm and a length of 6-17 mm (allowing tolerance in the position of the polymer strip 18).

[0054] In Figures 4 and 5, the polymer element 18 is fixed to the modified region 20. This may be achieved by any suitable means, e.g. heat welding or heat sealing. Although not shown in Figures 4 and 5, a respective polymer element, which may be the same as or similar to the polymer element 18, may be similarly fixed to the reverse face of the substrate 16. Typically, during the fixing process, the polymer element(s) 18 are molded such that they cover and are fixed to the edges 24 of the metallic substrate 16. When fixed to the metallic strip 16 the preferred arrangement is that the polymer element(s) 18 form a seal around the periphery of the metallic substrate 16. The, or each, modified region 20 strengthens the adhesion between the polymer element 18 and the substrate 16 (in comparison with adhesion that could be obtained by fixing the polymer element 18 to an unmodified region), without requiring the relevant portion(s) of the substrate 16 to be electroplated or otherwise coated with other substance(s).

[0055] Figure 5 shows the metallic substrate 16, with the attached polymer element 18, connected to the stack 12 of the cell 10. In particular the substrate 16 is connected to one of the electrodes of the cell 10 (the anode 14A in the illustrated example although it may alternatively be connected to the cathode 14C). Typically, the substrate 16 is welded to the electrode 14A (as indicated by weld 36), and any suitable welding technique may be used for this purpose, e.g. spot welding, ultrasonic welding or laser welding. The connection is electrically conductive to facilitate the metallic substrate 16 serving as a tab for transferring electrical power from and / or to the cell 10 as applicable. In typical embodiments, the metallic substrate 16 is a metallic strip and is connected to the stack 12 at an end of the strip 16. Typically, the end of the strip 16 overlaps with and is welded or otherwise fixed to the respective electrode of the cell 10. As shown in Figure 5, the modified region 20, and therefore also the polymer strip 18, is located adjacent the end of the metallic strip 16. The preferred arrangement is such that the modified region 20, and therefore also the polymer strip 18, is spaced apart from the electrode to which the strip 16 is connected.

[0056] In preferred embodiments, the metallic substrate 16 is formed from aluminium or an aluminium alloy. Alternatively, the metallic substrate 16 may be formed from one or more of the following metals: Li, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Sn, W or alloys thereof.

[0057] In preferred embodiments, the laser processing is configured to cause the, or each, modified region 20 to have a textured surface, in particular a textured surface that is rougher (i.e. less smooth) than the unmodified metallic substrate 16 (and therefore rougher than the unmodified region(s) of the substrate 16). It is preferred that the textured surface has a texture, or pattern, that is uniform or substantially uniform over the whole surface area, or substantially the whole surface area, of the modified region 20. Creating the surface texture typically involves modifying the surface topography of the modified region(s) 20. Modifying the surface topography may involve creating formations and / or structures in the surface and / or below the surface of the modified region(s) 20. The formations are preferably uniform, or substantially uniform, in respect of any one or more of their depth, size (e.g, area), spacing, distribution and / or shape. The formations and / or structures may be microscale formations and / or structures, i.e. having microscale dimension(s), or dimensions of less than 100 microns (e.g. width, length, depth and / or area), for example of the order 0.01 -100pm. The formations and / or structures are typically formed as result of the action of the pulsed laser beam on the surface of the substrate 16.

[0058] In preferred embodiments, the laser processing is configured to change the chemical composition, or cause chemical and / or electrochemical modification, or conversion, of the metallic substrate 16 in the, or each, modified region 20. Preferably, the laser processing is configured to cause oxidation of the metallic substrate in the, or each, modified region 20, or otherwise to cause the formation of one or more metal oxide or mixed oxides in the modified region 20, typically as a conversion layer in the modified region 20. A hydroxide layer, e.g. an atomic hydroxide layer at the surface of the modified region 20, may be formed during the laser processing as a result of the presence of atmospheric moisture. More generally, it is preferred that the laser processing is configured to cause the conversion layer in the modified region(s) 20 to have an oxygen content of greater than 1%. It is preferred that the depth, or thickness, of the conversion layer at the modified region(s) is microscale, for example of the order 0.1 -100pm. The preferred thickness helps to create the desired oxygen content. The laser processing may be performed in air, or in an environment containing oxygen (preferably at a level above 20%).

[0059] The laser texturing may be performed by the application of pulsed laser beam(s) 32 to the metallic substrate 16. The substrate surface(s) 22, 23, 24 may be modified to have any one or more of a plurality of functionalities, which can improve performance of the substrate 16 in a given application, i.e. the substrate is enhanced by laser surface engineering. Functional textures can be provided on the substrate by utilising pulsed laser(s) to remove defined areas of material and developing microstructures to enhance certain functionalities, such as water repelling, adhesion promotion, advanced heating / cooling processes and / or controlled surface friction. Mechanical performance can also be enhanced significantly by using continuous wave or pulsed lasers to impart beneficial stresses and / or sub-surface micro-scale features.

[0060] The types of laser used and its mode of operation may be selected for specific requirements and substrate finishes. Pulsed lasers are well suited to laser texturing due to the ability to tune the power output to achieve defined structures and composition transitions. Pulse duration may be controlled by any conventional means, e.g. a modulating apparatus, and may vary from milliseconds to femtoseconds. Nanosecond to femtosecond pulse durations are typically those used when considering material processing. The gain medium of the laser must also be considered when determining the application and desired final product. Examples are given below. i. Gas lasers utilise a gas to generate light by passing an electric current through the medium.

[0061] Common examples include CO2 lasers. ii. Solid-state lasers use crystalline or amorphous solids mixed with rare-earth elements to achieve optical gain. Common examples include Neodymium-doped Yttrium Aluminium Garnet (Nd:YAG) lasers. ill. Fibre lasers are a special form of solid-state lasers whereby an optical fibre gain medium is used, typically doped with rare-earth elements. Common examples include Ytterbium and Erbium-doped fibre lasers.

[0062] The use of a laser light source, preferably using a pulsed laser beam, facilitates rapid and localised surface treatment with a uniform, or substantially uniform, depth and surface topography across 100%, or substantially all of, of the desired treatment region, i.e. the modified region, of the metallic substrate 16. A uniform, or substantially uniform, surface topography is achievable using laser treatment due to the repeatability of the pulsed laser light incident on the surface of the metal. A uniform, or substantially uniform, topography is advantageous in creating a surface with optimal adhesion properties to ensure there are not areas of poor adhesion which could result in a failure of the lead tab, and ultimately the energy storage device.

[0063] In preferred embodiments, a fibre laser light source is used to process, or modify, the metallic substrate 16. A fibre laser light source utilises fibre optics to focus and intensify the laser beam; this enables faster processing times, with greater energy efficiency than that which is achievable with a CO2 laser. CO2 lasers operate in the far-infrared wavelength range, which is absorbed by non- metallic materials but poorly absorbed by most metals, including aluminium. A fibre laser is a special form of solid-state laser with an optical fibre gain medium. Other solid-state lasers, such as Nd:YAG or Nd:YVO4 lasers, can be utilised but these are more complex and less practical for delivery to the workspace, especially when considering the necessity to traverse the body of the tab and process around the edge of the material. Fibre lasers are preferred for modification of the substrate 16 due to the absorption of the desired wavelength range, delivery to the workspace via fibre optic cable(s) and also the tuneability to the feature size of the workpiece - in this example including the edges of the lead tab. In preferred embodiments, the wavelength range of the laser source 30 is 780-2200 nm.

[0064] The preferred wavelength range facilitates absorption of the laser energy by the metallic substrate 16 in comparison with, for example, a CO2 laser with a wavelength of 10000 nm.

[0065] Typical processing times for surface modifications range from seconds to minutes, but laser processing treatments can be achieved with sub-second bursts of laser beam(s). Preferred embodiments of the invention involves the treatment of metallic substrate surface layers to achieve characteristics such as, but not limited to, corrosion inhibition, adhesion promotion, chemical and electrochemical activation, surface topography modification and / or protection from effects of atmospheric environment - for example hydration and / or oxidation. In some embodiments the modified surface of the substrate 16 is combined with other components or materials to form the lead tab for use in a battery cell or other energy storage device.

[0066] Optionally, the metallic substrate 16 is pre-treated (i.e. prior to laser processing) by any one or more of: acid or alkali cleaning, degreasing, etching, electroplating, or a combination of any two or more of these treatments. For example, the metallic substrate may be cleaned with a degreasing agent, followed by an acid cleaning step. Alternatively, or in addition, the metal substrate 16 is treated with dilute acid to etch the surface. In preferred embodiments, the metallic substrate 16 is not pre-treated and the laser light incident on the surface is used to simultaneously clean the surface and produce the desired modified region or conversion layer. The use of a single step to simultaneously clean the metal substrate surface and produce a conversion layer, or modified region 20, is not currently achievable with conventional non-laser-based metal treatment processes. It is found that cleaning is inherent to the laser processing depending on the laser power involved. For example very low powers do nothing to the surface, slightly higher power will clean, higher still will clean and texturise the surface, and even higher power still will clean, texturise and create the desired conversion layer in the surface. The tuneability of the pulsed laser light parameters make it possible to clean and / or texturise the surface and / or create the conversion layer. In another preferred embodiment the metal substrate is cleaned with an acidic and / or an alkaline cleaning agent before being electroplated with nickel (prior to laser processing).

[0067] The laser-induced conversion at the surface of the metal substrate 16 can allow for use of the substrate in environments that would usually be restrictive, or to access chemical and / or electrochemical activity that would otherwise be prevented. In one preferred embodiment the conversion of the metallic substrate 16 to form a metal oxide layer allows for the use of the substrate in corrosive environments.

[0068] The laser processing may be configured to cause a conversion of the metal substrate that involves an alteration of crystal structure. Amorphous structures exhibit no long-range ordering due to an absence of atomic periodicity. Amorphous structures are often generated from anodising treatments. Crystalline metal oxide structures have regular atomic packing which leads to different properties when compared to amorphous structures of the same constituents. For example, Aluminium oxide can exist as an amorphous solid or as a-AlzOs and various other polymorphs of AI2O3. a-AIzCh has a hexagonal close-packed structure, and benefits from increased hardness and fluorescence / phosphorescence under UV-light over the amorphous equivalent. The laser light and processing parameters at the surface of the substrate 16 may be controlled for selectivity regarding phase structures of the resultant conversion layer or coating. Incident laser energy and time may be controlled to change crystal phases of the conversion layer 20 of the metal substrate 16.

[0069] The laser conversion may increase the wear resistance and hardness of the modified surface layer 20 by forming a new compound such as a metal oxide. The conversion compounds formed can have their properties and compositions controlled by the laser processing parameters. Improved hardness and wear resistance can improve component lifespan in abrasive environments, leading to a resistance to penetration, scratching and plastic deformation.

[0070] In an exemplary embodiment the metallic substrate 16 is treated with a fibre laser light source to create a modified region 20, or conversion layer, comprising one or more different chemical compound at the surface of the metallic substrate 16 (i.e. different from the material from which the unprocessed substrate 16 is made). The conversion layer may consist of a metal oxide or mixed oxides and improves the adhesion strength of the polymer and the corrosion resistance at the region of interest.

[0071] In a preferred embodiment, the substrate 16 is treated with a fibre laser light source to simultaneously impart laser texturing that improves polymer adhesion and create a conversion layer of a different chemical compound at the surface (i.e. in the modified region 20) of the metallic substrate 16.

[0072] In a preferred embodiment the substrate 14 is formed from aluminium and the resulting conversion layer contains >1% O (oxygen). Preferably, the conversion layer covers >95% of a designated area (i.e. the or each modified region 20) of the parent substrate 16. Preferably, the topographical modifications, or formations, have a uniform, or substantially uniform, spacing, depth and preferably size across the entire, or substantially the entire, designated area(s) 20. As indicated above, the dimensions of the formations are preferably microscale. The spacing of the formations is also preferably microscale, e.g. 0.01 -100pm. In order to achieve the desired characteristics of the modified region 20, it is preferred that the surface of the substrate 16 (in the modified region 20) is scanned with a pulsed laser beam 32, preferably with a constant, or substantially constant, hatch distance (also known as spot distance or scan spacing). Typically, the pulsed laser beam scanning is performed with a one or two dimensional array of laser spots on the substrate surface, wherein the hatch distance is preferably uniform, or substantially uniform, between adjacent laser spots in the, or each, dimension of the array as applicable. It is preferred that the scanning speed is constant or substantially constant. It is preferred that pulse energy is constant or substantially constant. It is preferred that the hatch distance is such that adjacent laser spots overlap, preferably in the or each dimension of the scanning spot array as applicable. For example a constant pulse energy and hatch distance and spot size overlaps may achieve a uniform surface topography. By way of example, the hatch distance may be 0.005-0.05mm. The laser spot size (e.g. diameter or width) may for example be ^200 pm, preferably 2100 pm, or more preferably 250 pm (where the minimum spot size (e.g. diameter or width) may be 0.1 pm or 1 pm). For example, in some embodiments the spot size (e.g. diameter or width) is 20-50 pm. The preferred arrangement is such that, for a given spot size, a hatch distance is selected such that adjacent laser spots overlap.

[0073] Table 1 provides exemplary laser parameters used on an aluminium substrate and the associated adhesion strengths achieved. The pulse energy (mJ) and pulse duration (ns) were varied to increase oxygen content of the conversion layer 20, and therefore corrosion resistance. The average coverage is indicative of the speed of the laser 30 across the surface of the substrate 16. The average speed is preferably constant throughout processing of the substrate 16. As illustrated in Table 1 , the average coverage may be increased to improve polymer adhesion, particularly for given values of pulse energy and pulse duration. The oxygen content, which is an indication of the oxidation caused by the laser processing, affects the substrate’s corrosion resistance. An oxygen content of 1% or greater, e.g. 1-50%, is considered to provide desirable corrosion resistance. An adhesion strength of 5N or greater is desired, preferably greater than 5N, more preferably 10N or greater. It is found that the laser speed (or average coverage), on its own or in combination with the pulse energy, can be controlled to obtain the desired adhesion strength and / or oxygen content. It is also found that the pulse duration, on its own or in combination with the pulse energy, can be controlled to obtain the desired adhesion strength and / or oxygen content.

[0074] Table 1

[0075] As shown in Table 1 , depending on the laser processing parameters there may be little or negligible oxidation of the substrate surface and / or inadequate adhesion strength. For example, samples A5 and A7 are considered to be failures because their oxygen content is too low to provide useful corrosion resistance and their adhesion strength is inadequate. In preferred embodiments, the laser processing is configured to cause oxidation of the substrate 16 such that the conversion layer 20 comprises at least 1% oxygen, preferably at least 20% oxygen. It is preferred that the laser processing is configured such that the depth, or thickness, of the conversion layer at the modified region(s) is microscale, for example of the order 0.01 -100pm, or larger. The preferred thickness helps to create the desired oxygen content. Obtaining the desired oxygen content and / or other characteristics of the modified region(s) 20 may be achieved by controlling the laser pulse energy and / or the pulse duration and / or the average coverage of the laser processing. It is found that the average coverage of the laser processing may be controlled to obtain the desired microstructure and / or other properties of the conversion layer 20, optionally in conjunction with adjustment of the instantaneous energy input. It is also found that the desired modification(s) of the conversion layer 20, in particular to achieve the desired adhesion strength and / or oxidation, can be created by controlling the pulse energy and / or the pulse duration. In particular, the pulse energy and / or pulse duration can be controlled to determine the instantaneous energy incident at the surface of the substrate 16, which affects how the substrate 16 is modified at the conversion layer 20 (chemically and / or topographically). In another preferred embodiment the substrate 16 is formed from Ni-plated Cu, for example with a plating thickness of 0.2 - 10 pm. The laser processing may be performed such that the resulting conversion layer 20 contains >1% oxygen (O). After the laser processing the conversion layer may comprise Ni with a low amount of oxide (preferably >1% but can be <1%). The oxide may comprise any one or more of NiO, CuO or Cu2O depending on the laser processing parameters. Preferably, the conversion layer covers >95% of the designated area (modified region(s) 20) of the substrate 16. Preferably, the total thickness of the Ni plating on the Cu substrate is greater than 0.1 pm and less than or equal to 10 pm.

[0076] Table 2 shows exemplary laser parameters used on a Ni-plated Cu substrate 16 and the associated adhesion strengths achieved.

[0077] Table 2

[0078] Although not illustrated in Table 2, depending on the laser processing parameters there may be little or negligible oxidation of the substrate surface. In preferred embodiments, the laser processing is configured to cause oxidation of the substrate 16 such that the conversion layer 20 comprises at least 0.1% oxygen, preferably at least 1% oxygen. It is preferred that the laser processing is configured such that the depth, or thickness, of the conversion layer at the modified region(s) is microscale, for example of the order 0.01-100pm, or larger. The preferred thickness helps to create the desired oxygen content. Obtaining the desired oxygen content and / or other characteristics of the modified region(s) 20 may for example be achieved by controlling the laser pulse energy and / or the average coverage of the laser processing. It is also found that the desired modification(s) of the conversion layer 20, in particular to achieve the desired adhesion strength and / or oxidation, can be created by controlling the pulse energy and / or the pulse duration. In particular, the pulse energy and / or pulse duration can be controlled to determine the instantaneous energy incident at the surface of the substrate 16, which affects how the substrate 16 is modified at the conversion layer 20 (chemically and / or topographically).

[0079] In another preferred embodiment the substrate 16 is formed from Cu. The laser processing may be performed such that the resulting conversion layer 20 contains >0.1% oxygen (O). After the laser processing the conversion layer may comprise Cu with a low amount of oxide (preferably >1% but can be <1%). The oxide may comprise any one or more of CuO or Cu2O depending on the laser processing parameters. Preferably, the conversion layer covers >95% of the designated area (modified region(s) 20) of the substrate 16. Table 3 shows exemplary laser parameters used on a Cu substrate 16 and the associated adhesion strengths acheived.

[0080] Table 3

[0081] Although not illustrated in Table 3, depending on the laser processing parameters there may be little or negligible oxidation of the substrate surface. In preferred embodiments, the laser processing is configured to cause oxidation of the substrate 16 such that the conversion layer 20 comprises at least 0.1% oxygen, preferably at least 1% oxygen. It is preferred that the laser processing is configured such that the depth, or thickness, of the conversion layer at the modified region(s) is microscale, for example of the order 0.01-100pm, or larger. The preferred thickness helps to create the desired oxygen content. Obtaining the desired oxygen content and / or other characteristics of the modified region(s) 20 may for example be achieved by controlling the laser pulse energy and / or the average coverage of the laser processing. It is also found that the desired modification(s) of the conversion layer 20, in particular to achieve the desired adhesion strength and / or oxidation, can be created by controlling the pulse energy and / or the pulse duration. In particular, the pulse energy and / or pulse duration can be controlled to determine the instantaneous energy incident at the surface of the substrate 16, which affects how the substrate 16 is modified at the conversion layer 20 (chemically and / or topographically).

[0082] Pulse energy may be calculated as follows:

[0083] Pulse energy = laser power / laser operating frequency, where pulse energy may be measured in joules (J), laser power may be measured in watts (W) and laser operating frequency may be measured in Hertz (Hz).

[0084] Pulse duration is the duration of each pulse of the laser beam 32 incident on the substrate 16. Relatively short pulses concentrate the same energy in a shorter time period, and hence reach higher peak powers. It is found that relatively short pulses cause more energy to be absorbed at the substrate surface, which may facilitate chemical change(s), e.g. oxidation, in the modified region 20, and / or facilitate the desired other modifications, e.g. topographical modifications, for achieving desired characteristics such as adhesion strength. In preferred embodiments, pulse duration and pulse energy are selected to cause the desired change(s) (chemical changes and / or topographical changes) in the modified region, or conversion layer 20. In particular, pulse duration and pulse energy may be selected to alter the oxygen content in the modified region 20 to a desired level (e.g. at least 1%), for example by causing oxidation or otherwise causing the formation of one or more metal oxide. Pulse duration and pulse energy may be selected to create the desired adhesion strength (e.g. 5N or above, preferably 10N or above) for example by creating the desired formations in the substrate surface. Either one or both of the pulse duration and pulse energy may be selected and / or adjusted to cause the desired chemical change(s) and / or topographical change(s).

[0085] For example, in embodiments in which the substrate 16 comprises aluminium, a relatively low pulse energy (e.g. 0.5 mJ or less) in combination with a relatively long pulse duration (e.g. 100 ns or more) may fail to cause the desired oxygen content in the conversion layer 20 and / or the desired adhesion strength. To achieve the desired oxygen content and / or adhesion strength, the pulse energy may be increased (e.g. to above 0.5 mJ, preferably to between 0.6 and 2 mJ) and / or the pulse duration may be shortened (e.g. to less than 100 ns, preferably to between 0.1 and 80 ns). Similarly, higher pulse energy levels (e.g. above 0.5 mJ, preferably to between 0.6 and 2 mJ) may also fail to cause the desired oxygen content and / or adhesion strength if the pulse duration is too high (e.g. above 100ns) but will cause the desired oxygen content and / or adhesion strength with lower pulse durations (e.g. 100ns or below). For example, for a pulse energy of 1 mJ, a pulse duration of 250 ns may fail to cause the desired oxygen content and / or adhesion strength whereas a pulse duration of 100 ns may cause the desired oxygen content and / or adhesion strength. Therefore, for a given pulse energy, the pulse duration may be selected and / or adjusted to achieve the desired oxygen content and / or other chemical change. Pulse duration and / or pulse energy may selected and / or adjusted to cause the desired adhesion strength at the modified region 20. Either one or both of the pulse duration and pulse energy may be selected and / or adjusted to create the desired adhesion strength.

[0086] In preferred embodiments, the average coverage of the laser 30 is selected and / or adjusted to cause the modified region 20 to have the desired adhesion strength (e.g. 5N or greater). Preferably, the average coverage of the laser 30 is selected and / or adjusted to cause the modified region 20 to have the desired adhesion strength. The average coverage is a measure of the rate at which the laser processing covers the modified region 20, i.e. area per second. The average coverage may be calculated as follows:

[0087] Average coverage = translational speed x hatch distance where average coverage may be measured in mm2 / s, translational speed may be measured in mm / s and hatch distance may be measured in mm.

[0088] It is found that selecting the translational speed, or average coverage, to be above a threshold level causes the modified region 20 to exhibit the desired adhesion strength. The threshold level may depend on any one or more of the pulse energy, the pulse duration and the material from which the substrate 16 is formed. For example, from samples A7 and A8 of Table 1 , increasing the average coverage significantly improves the adhesion strength. From Table 2 it can be seen from samples NC2 and NC3 that increasing the average coverage improves the adhesion strength. . For example, for an aluminium substrate and a pulse energy of 1 mJ an average coverage of 5 mm2 / s provides an adhesion strength of less than 5N, whereas an average coverage of 10 mm2 / s or more (e.g. between 10 mm2 / s and 40 mm2 / s) produces an adhesive strength of 10-20N.

[0089] Furthermore, the pulse duration can affect the adhesion strength. By way of example, it is found that for an aluminium substrate, a pulse energy of 1 mJ and an average coverage of 10 mm2 / s, an adhesion strength of less than 5N may be obtained for pulse durations of between 100-250 ns, whereas a pulse duration of between 30-75 ns produces an adhesion strength of 13-20N.

[0090] In preferred embodiments, the pulse energy of the laser light ranges from 1 pj to 100 mJ, more preferably 10 pJ to 10 mJ. The wavelength of the laser light is preferably greater than 0 pm, e.g. 0.01 pm or greater. The wavelength of the laser light is preferably less than 10 pm. In preferred embodiments the wavelength is 780-2200 nm. Preferably, the pulse duration is of 1 ps or less. For example in typical embodiments the pulse duration may be 0.1 -300 ns, preferably 0.1 -100 ns. The operating frequency is typically between 1 - 50,000 kHz. The beam translational speed is preferably 100 - 200,000 mm / s, preferably 500-5000 mm / s. The average coverage is typically 5-100 mm2 / s, and is preferably constant or substantially constant. In any given embodiment, the values of these parameters required to achieve the desired chemical change(s) and / or adhesion strength may depend on each other and / or on the material from which the substrate 16 is formed. Any one or more of these parameters may therefore be selected and / or adjusted as required in order to achieve the desired chemical change(s) and / or adhesion strength.

[0091] In preferred embodiments, fibre laser-based processing is performed on the relevant region(s) of the substrate 16 to create a conversion layer 20 with a uniform depth and topographical surface that improves the polymer adhesion, and so creates a strong bond between the materials.

[0092] In preferred embodiments, the creation of the modified region(s) 20, or conversion layer, comprises a single-step processing method whereby the metallic substrate 16 is treated with the laser light source to produce the desired modified region, or conversion layer, e.g. without subsequently coating, electroplating or further laser processing the substrate 16, and optionally without pre-treating the substrate 16.

[0093] In preferred embodiments, the laser processing is configured to create a conversion layer in the modified region(s) 20 with an oxygen content of greater than 1%.

[0094] In preferred embodiments, the laser processing is configured to produce a conversion layer at the modified region(s) with a constant, or substantially constant, depth over more than 95% of the modified region(s) 20. The laser processing is preferably configured to produce a conversion layer at the modified region(s) having formations with a uniform, or substantially uniform, spacing, preferably over more than 95% of the modified region(s) 20. The laser processing is preferably configured to produce a conversion layer at the modified region(s) having formations with a uniform, or substantially uniform, size, preferably over more than 95% of the modified region(s) 20.

[0095] In some embodiments, the laser processing may be configured to produce a conversion layer with an oxygen content >0% with equal depth and spacing across >95% of the modified region(s) 20.

[0096] Advantageously, the metallic substrate 16 is not pre-treated before the laser processing.

[0097] Optionally, the metallic substrate is electroplated with nickel before the laser processing.

[0098] In some embodiments, the conversion layer 20 does not require further coating or surface treatment, in particular for use as a lead tab in an energy storage device.

[0099] In preferred embodiments, the laser processing is configured so that at least 95% of the predetermined region(s) 20 of the metallic substrate 16 is modified at the surface in any one or more of the following ways: i. to impart chemical and topographical variations in order to form a corrosion-inhibiting layer (e.g. an oxide or mixed oxides layer) with a thickness of 1 nm or greater; ii. to impart chemical, morphological, and topographical variations in order to promote adhesion at the modified surface layer.

[0100] The preferred laser processing method involves irradiating the surface of the substrate 16 with pulsed laser light. Preferably, the pulse energy of the laser light ranges from 1 pj to 100 mJ. Preferably, the wavelength of the laser light is greater than 0 pm, e.g. 0.1 pm or greater. Preferably, the pulse duration is of 1 ps or less. The operating frequency is typically between 1 - 50,000 kHz. The beam translational speed is preferably 100 - 200,000 mm / s.

[0101] In preferred embodiments, the laser processing is configured to form a conversion layer, or modified region, comprising any one or more of an oxide layer, a hydroxide layer or mixed oxide layer. Such layers provide improved corrosion resistance and polymer adhesion.

[0102] In some embodiments, the laser processing is configured to cause the conversion layer to undergo a crystalline phase change. For example formation of AI2O3 from Al involves a crystalline phase change.

[0103] In some embodiments, the laser processing is configured to cause the conversion layer to form an amorphous region. For example, in embodiments in which AI2O3 is formed, it may be crystalline or amorphous (or partially crystalline).

[0104] The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.

Claims

CLAIMS:

1. A method of manufacturing a conductive tab for a battery cell, the method comprising: supplying a metallic substrate; irradiating at least one region of at least one surface of the metallic substrate with pulsed laser light to create formations in said metallic substrate in said at least one region, and / or to modify the chemical composition of said metallic substrate in said at least one region.

2. The method of claim 1 , wherein creating said formations involves creating uniform or substantially uniform formations, preferably creating said formations with uniform or substantially uniform depth, and / or size, and / or spacing, and / or shape.

3. The method of claim 1 or 2, wherein said formations are microscale formations, preferably having one or more dimension of 0.01 -100pm.

4. The method of any preceding claim, including forming said formations in said at least one surface with a depth of at least 0.01 pm, said depth preferably being uniform or substantially uniform.

5. The method of any preceding claim, wherein the, or each, of said at least one region corresponds to a respective region to which a polymer element is to be fixed, and wherein, preferably, said formations cover at least 95% of the respective region.

6. The method of any preceding claim, wherein modifying the chemical composition of said metallic substrate involves increasing the oxygen content of said metallic substrate in said at least one region to at least 1%.

7. The method of any preceding claim, wherein said irradiating involves creating a modified layer in said metallic substrate in said at least one region, wherein said formations are created in said layer and / or said chemical composition is modified in said layer, and wherein said layer has a depth of at least 0.01 pm, and said depth is preferably uniform or substantially uniform.

8. The method of any preceding claim, wherein the, or each, of said at least one region corresponds to a respective region to which a polymer element is to be fixed, and wherein, preferably, said chemical composition is modified over at least 95% of the respective region.

9. The method of any preceding claim, including using a fibre laser device to perform said irradiating.

10. The method of any preceding claim, wherein said pulsed laser light has a pulse energy between 1 pJ and 100 mJ inclusive, preferably 10 pJ to 10 mJ.

11. The method of any preceding claim, wherein said laser light has a wavelength between 0.1 - 10 pm, preferably 780-2200 nm.

12. The method of any preceding claim, wherein said pulsed laser light has a pulse duration of 1 ps or less, preferably 0.1 -300 ns, more preferably 0.1 -100 ns.

13. The method of any preceding claim, wherein said pulsed laser light is produced by a laser device having an operating frequency between 1 - 50,000 kHz.

14. The method of any preceding claim, wherein said irradiating involves scanning said pulsed laser light with respect to said metallic substrate, preferably with a constant, or substantially constant, hatch distance, and wherein, preferably, said pulsed laser light is scanned with a translational speed of between 100 - 200,000 mm / s, preferably 500-5000 mm / s.

15. The method of any one of claim 14, wherein said pulsed laser light is scanned to provide a one or two dimensional array of laser spots on the substrate surface, and wherein the hatch distance is preferably uniform, or substantially uniform, between adjacent laser spots in the, or each, dimension of the array, and wherein, preferably, said pulsed laser light is scanned with a hatch distance that causes adjacent laser spots overlap, preferably in the or each dimension of the scanning spot array.

16. The method of any preceding claim, wherein said pulsed laser light is scanned with a hatch distance of 0.005-0.05 mm.

17. The method of any one of claims 14 to 16, said pulsed laser light is scanned with a constant, or substantially constant, scanning or translational speed, and / or wherein said pulsed laser light is scanned with an average coverage that is constant or substantially constant, wherein: average coverage = translational speed x hatch distance.

18. The method of any one of claims 14 to 17, wherein said pulsed laser light is scanned with an average coverage of 5-100 mm2 / s, wherein: average coverage = translational speed x hatch distance.

19. The method of any preceding claim, wherein said pulsed laser light has a pulse energy that is constant or substantially constant.

20. The method of any preceding claim, including controlling at least one parameter of said pulsed laser light to create said formations and / or to modify said chemical composition, wherein said at least one parameter preferably includes a pulse energy of said pulsed laser light and / or a pulse duration of said pulsed laser light.21 . The method of any preceding claim, including controlling the pulse duration and the pulse energy of said pulsed laser light to cause one or more desired change in said chemical composition, and wherein, preferably, the method includes controlling the pulse duration and the pulse energy of said pulsed laser light to increase an oxygen content in said at least one region to a desired level, preferably at least 1%.

22. The method of any preceding claim, wherein said irradiating involves scanning said pulsed laser light with respect to said metallic substrate, the method further including controlling a scanning speed, or translational speed, of said pulsed laser light to create said formations and / or to modify said chemical composition, and / or controlling an average coverage of said pulsed laser light to create said formations and / or to modify said chemical composition, and wherein, preferably, the method includes controlling said translational speed and / or average coverage to cause said at least one region to exhibit an adhesion strength of a desired level, preferably at least 5N.

23. The method of any preceding claim, wherein said metallic strip is formed from aluminium or an aluminium alloy, and wherein modifying the chemical composition preferably involves forming aluminium oxide and / or mixed metal oxides, or wherein said metallic strip is formed from copper or nickel-plated copper.

24. The method of any preceding claim, including aligning a respective polymer element, for example a polymer strip, with the, or each, of said regions, and causing said polymer element to adhere to the respective region, preferably by heating.

25. A method of manufacturing a pouch cell comprising battery components located in a pouch, said battery components including an anode and a cathode, said method comprising electrically connecting a respective conductive tab to said anode and said cathode such that each conductive tab protrudes from said pouch, wherein each conductive tab is manufactured by the method of any one of claims 1 to 24, and wherein said method further includes: aligning a respective polymer element, for example a polymer strip, with the, or each, of said regions of each conductive tab, and causing said polymer element to adhere to the respective region, preferably by heating; and sealing said pouch around said conductive tabs.

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