Perforated copper foil for use in battery electrode manufacturing

Abstract

The present disclosure relates to a copper foil designed for use in battery electrodes, and a method of forming thereof, wherein the foil features a unique non-uniform perforation pattern that may enhance its mechanical strength and facilitate improved handling, especially during electrode coating processes. The foil comprises at least a first non-perforated section, a first perforated section, and a second perforated section, with the average void area of the first perforated section being at least about 1% higher than that of the second perforated section. Introduction of the intermediate perforation section may ensure the integrity of the foil throughout production, transportation, and electrode manufacturing processes.

Description

[0001] PERFORATED COPPER FOIL FOR USE IN BATTERY ELECTRODE MANUFACTURING

[0002] FIELD OF THE INVENTION

[0003] The present invention, in some embodiments thereof, relates to copper foils, and more particularly, but not exclusively, to perforated copper foils designed for use as current collectors as well as for mass production of electrodes comprising the same.

[0004] BACKGROUND OF THE INVENTION

[0005] Battery technology continues to evolve, demanding enhanced materials for improved performance and reliability. A critical component of battery electrodes is the metallic foil used as a current collector. Current collectors play an important role in the charge / discharge process of batteries, as they support the active layer and collect and distribute electrons to / from the active layer. To accelerate the electron transfer, contact between the current collector and active layer should be maintained during the charge / discharge process for thousands of cycles. In other words, current collectors should enable efficient and long-lasting adhesion of the active material thereto. In lithium- ion batteries (LIB), the electrode structure should also enable efficient transport of Li+ions between the electrolyte and the active layers, and in particular, within the active layers. Thus, ideally, a LIB electrode structure should offer high electronic and ionic conductivity.

[0006] At present, in commercially available LIBs, current collectors are made of flat metallic foils (typically copper and aluminum) having a typical thicknesses of 6-15 pm. To improve the adhesion between the active layer and the current collector, reduce weight and provide improved pathways for Li+ions, perforated current collectors have been developed.

[0007] WO2023 / 148736 by the present assignee, which is incorporated herein by reference, provides perforated metal foils for use as current collectors in battery electrodes.

[0008] In mass battery electrode manufacturing, current collector foils are typically provided in a roll configuration, which is suitable for continuous electrode coating that includes applying an electrode slurry onto the foil, passing the foil through a drying oven, calendaring, re-reeling, and slitting into narrower strips suitable for different sizes of electrodes. This multi-step process which the metallic foil undergoes until a final usable electrode is formed is mechanically trying, sometimes leading to foil tearing or deformation, which adversely affects the functionality of the current collector.

[0009] There remains a need for efficient and durable metallic foils and electrode manufacturing processes, to ensure high-quality electrode performance.

[0010] SUMMARY OF THE INVENTION

[0011] The present disclosure provides copper foils, that can be used as current collectors in batteries, exhibiting a non-uniform perforation pattern for improving mechanical strength and durability of the foils, which inter alia, may alleviate both foil and electrode production and handling processes. The long copper foil is designed with a unique configuration, typically featuring a main perforated section that runs longitudinally along the longitudinal direction of the foil. This perforated section is characterized by a substantially uniform hole pattern, with holes of a particular shape and size and a defined hole density, and arrangement pattern creating an intricate and functional design, typically following a seamless repeating pattern (SRP). Flanking this main perforated section is at least one, and optionally two, parallel section situated adjacently to the perforated section, referred to herein as “intermediate perforated section”, which has a different perforation pattern from the perforated section, such that the main perforation section has a larger void area than the void area of the intermediate perforated section. The copper foil further contains at least one solid section of continuous foil without perforations, the solid section is adjacent to the intermediate perforated section, on the opposing side to the main perforated section.

[0012] In the intermediate perforation sections, the perforation density is lower than the perforation density of the central perforated section. This is achieved by smaller hole size and / or lower hole density (i.e., bigger distance between adjacent holes) and / or change in the pattern of the holes arrangement in these sections, as compared to the perforated section. In some currently preferred embodiments, the at least one intermediate perforation section is characterized by a gradually decreasing perforation up to no perforation at all (i.e., up to the solid section). In some embodiments, the perforated section is a central perforated section, which is flanked on both sides thereof by the intermediate perforated sections. The solid sections flank the outer side of each of the intermediate perforated sections, i.e., laterally extend between the intermediate perforated section and the edge of the foil.

[0013] The lower perforation density of the intermediate perforated section enhances structural strength / durability of the foil towards the edges thereof, while maintaining its functional properties in the perforated section.

[0014] In some embodiments, the central perforated section has an average void area ranging from about 5% to about 98%. In some embodiments, the intermediate perforated section has an average void area ranging from about 0.1% to about 97%. The foil's width proportions are finely adjustable to meet application requirements, with the nonperforated section ranging about 0.5-30%, the perforated section ranging about 70-99.4%, and the intermediate perforated section ranging about 0.1-30% of the foil's width.

[0015] The present application further details how the main perforated section can differ from the intermediate perforated section, including variations in hole size, density, and hole arrangement. The inventive foil, with its precise control over void areas and section attributes, finds applications as a porous current collector in electrodes and can be fabricated through electrodeposition, laser engraving, mechanical punching, electrochemical etching, chemical etching, electric discharge machining and others. In some currently preferred embodiments, the foil is fabricated through electrodeposition. The foil typically has a thickness ranging 1-50 pm. In some specific embodiments, the copper foil has a thickness in the range of 5-15 pm, more specifically in the range of 8- 12 pm.

[0016] Additionally, the application encompasses an electrode formed using this foil, and a method for creating such electrodes, involving application of active material slurry to the current collector in a continuous automated manner like roll-to-roll fabrication.

[0017] Thus, according to an aspect of some embodiments of the present invention, there is provided a copper foil that includes: at least one non-perforated section extending in a longitudinal direction of the foil; at least one perforated section extending in the longitudinal direction and laterally offset from the at least one non-perforated section, and at least one intermediate perforated section positioned and extending longitudinally between the perforated section and the non-perforated section, wherein an average void area of the perforated section is at least about 1 % greater than an average void area of the intermediate perforated section.

[0018] In some embodiments, the copper foil consists of the at least one non -perforated section, the at least one main perforated section, and the at least intermediate perforated section. In some particular embodiments, the copper foil consists of: one main perforated section which is a central perforated section, i.e., the longitudinal axis (LI) of the foil runs through the center of the central perforated section; two intermediate perforated sections, adjacent to and outwardly flanking the central perforated portion; and two nonperforated sections, adjacent to and outwardly flanking the intermediate perforated sections, the non-perforated sections extending to the lateral edge of the foil.

[0019] In some embodiments, the intermediate perforated section has a substantially uniform width throughout the length of the foil.

[0020] In some embodiments, the average void area of the perforated section ranges from about 5% to about 98% of the total area of the perforated section.

[0021] In some embodiments, the average void area of the intermediate perforated section(s) ranges from about 0.1% to about 97% of the total area of the intermediate perforated section.

[0022] In some embodiments, the width of the non-perforated section(s) ranges from about 0.5% to about 30% of the width of the copper foil.

[0023] In some embodiments, the width of the perforated section ranges from about 70% to about 99% of the width of the copper foil.

[0024] In some embodiments, the width of the intermediate perforated section(s) ranges from about 0.1% to about 30% of the width of the copper foil.

[0025] In some embodiments, the width of said intermediate perforated section ranges from about 5% to about 100% of the width of the non-perforated section (i.e., solid margin section). In some embodiments, the width of said intermediate perforated section ranges from 1-10 mm, and the width of the non-perforated portion ranges from 10-50 mm. In some embodiments, the width of said intermediate perforated section is about 5 mm, and the width of the non-perforated portion is about 20 mm.

[0026] In some embodiments, each of the perforated section and the intermediate perforated section(s) individually comprise a pattern of holes. In some embodiments, the pattern of the main perforated section is a seamless repeating pattern. In some embodiments, the pattern of the intermediate perforated section is non seamless. In some further embodiments, the pattern of the intermediate perforated section is a second seamless repeating pattern which is different from the seamless repeating pattern of the main perforated section.

[0027] In some embodiments, the seamless repeating pattern of the perforated section is characterized by an average hole size ranging 10-2000 pm and / or a hole density ranging 4-400 holes / mm2.

[0028] In some embodiments, the intermediate perforated section is characterized by holes having an average hole size ranging 10-1800 pm and / or a hole density ranging 4- 300 holes / mm2.

[0029] In some embodiments, at least one of the main perforated section and the intermediate perforated section is characterized by holes having an average hole size ranging 50-150 pm.

[0030] In some embodiments, the perforated section is characterized by essentially the same average hole size and a larger hole density compared to the intermediate perforated section.

[0031] In some embodiments, the perforated section is characterized by essentially the same average hole size and a smaller vertical and / or horizontal distance between at least a portion of adjacent holes compared to the intermediate perforated section.

[0032] In some embodiments, the perforated section is characterized by essentially the same hole density and a larger average hole size compared to the intermediate perforated section.

[0033] In some embodiments, the perforated section is characterized by essentially the same vertical and / or horizontal distance between adjacent holes and a larger average hole size compared to the intermediate perforated section.

[0034] In some embodiments, the perforated section is characterized by a larger hole density and a larger average hole size compared to the intermediate perforated section.

[0035] In some embodiments, the perforated section is characterized by a larger hole density and a smaller vertical and / or horizontal distance between adjacent holes compared to the intermediate perforated section. In some embodiments, the perforated section is characterized by holes having a different shape and / or a different relative orientation compared to the intermediate perforated section.

[0036] In some embodiments, the average void area of the perforated section is about 1- 90% greater than the average void area of the intermediate perforated section.

[0037] In some embodiments, the intermediate perforated section comprises a gradient pattern having an average void area that decreases from the perforated section towards the non-perforated section(s). The gradient may be a linear gradient. In some embodiments, the intermediate perforated section comprises one or more discrete subsections, each of said subsections is characterized by a step-wise decrease in porosity (as compared to its adjacent subsection), namely having an average open area that decreases from the perforated section towards the non-perforated section(s).

[0038] In some embodiments, the intermediate perforated section has a pattern that differs from the pattern of the perforated section in that a certain percentage of the holes present in the perforated section is eliminated in the intermediate perforated section. In further embodiments, said holes are gradually eliminated towards the non-perforated section. In further embodiments, the holes are eliminated in an irregular manner towards the non-perforated section.

[0039] In further embodiments, the holes are eliminated in a step-wise manner, wherein a percentage of the width of each step out of the total width of the intermediate perforated section is essentially similar to said certain percentage of holes that are eliminated in each respective step.

[0040] The non-perforated section may constitute a longitudinal margin of the foil.

[0041] In some embodiments, the copper foil contains a non-perforated section, a first perforated section, a second perforated section, a first intermediate perforated section positioned between the non-perforated section and the first perforated section, and a second intermediate perforated section positioned between the non-perforated section and the second perforated section.

[0042] According to another aspect of some embodiments of the present invention, there is provided a copper foil according to the various embodiments hereinabove, formed by electrodepo sition . In some embodiments, the copper foil provided herein has a thickness that ranges about 1-100 pm, 1-50 pm, 5-20 pm, or 5-15 pm.

[0043] In some embodiments, said perforated section and said intermediate perforated section have a tensile strength in the range of 50-500 MPa, 100-300 MPa, or 150-250 MPa. In some embodiments, the solid section has a tensile strength in the range of 100- 1000 MPa, 200-700 MPa, or 300-400 MPa.

[0044] In some embodiments, less than 1%, less than 0.5%, less than 0.1%, or less than 0.05% of the perforations in at least one of said perforated section and said intermediate perforated section are non-through-holes. In some further embodiments, substantially all of the perforations in said perforated section and said intermediate perforated section are through-holes.

[0045] In some embodiments, the copper foil is corrugated.

[0046] In some further aspects of the invention, the copper foil, or at least the main perforated section thereof, is being for use as a current collector, e.g., in an electrode.

[0047] According to another aspect of some embodiments of the present invention, there is provided an electrode that includes the copper foil provided herein, or at least the perforated section of the copper foil provided herein.

[0048] In some embodiments, the electrode comprises a battery tab connected to the nonperforated section of the copper foil.

[0049] According to yet another aspect of some embodiments of the present invention, there is provided a method of manufacturing an electrode, which is effected by: i) providing the copper foil as disclosed herein; ii) applying an electrode active material slurry on at least the perforated section of the copper foil provided herein, thereby forming the electrode; and iii) optionally separating the perforated section from the non-perforated section(s) and the intermediate perforated section(s).

[0050] In some embodiments, the method includes separating the perforated section from the non-perforated section(s) and the intermediate perforated section(s).

[0051] In some embodiments, the method further includes applying the electrode active material slurry to the intermediate perforated section of the copper foil. In some embodiments, the method does not involve separating the perforated section from the intermediate perforated section(s). In certain embodiments, the method does not involve separating the perforated section and the intermediate perforated section from the nonperforated section(s).

[0052] According to yet another aspect of some embodiments of the present invention, there is provided a method of forming an electrode, comprising: i) providing the copper foil disclosed herein; ii) applying an electrode active material slurry on at least the perforated section and the at least one intermediate perforated section of the copper foil, thereby forming the electrode; and iii) optionally separating the perforated section and the intermediate perforated section from the non-perf orated section.

[0053] According to yet another aspect there is provided a method of forming a copper foil comprising: i) exposing at least a portion of a drum having a patterned lateral surface to an electrolyte comprising copper ions, ii) connecting the drum to a negative pole of a power source, wherein an anode that faces said portion of the drum, and is exposed to said electrolyte, is connected to a positive pole of the power source, iii) rotating the drum and continuously separating the copper foil that is electrically deposited thereon from the drum, wherein the patterned lateral surface comprises at least one circumferential nonpatterned section, at least one circumferential patterned section comprising electrically insulating regions, and at least one circumferential intermediate patterned section comprising electrically insulating regions, said intermediate patterned section positioned and extending longitudinally between said patterned section and said non-patterned section, wherein the electrically insulating regions of the patterned section occupy an area that is at least about 1% greater than an area occupied by the electrically insulating regions of the intermediate patterned section.

[0054] In some embodiments, the copper foil formed by the method comprises at least one non-perf orated section extending in a longitudinal direction of the foil; at least one perforated section extending in said longitudinal direction and laterally offset from the at least one non-perforated section, and at least one intermediate perforated section positioned and extending longitudinally between said perforated section and said non-perforated section, wherein an average void area of said perforated section is at least about 1 % greater than an average void area of said intermediate perforated section.

[0055] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0056] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying figures. With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the figures makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[0057] In the figures:

[0058] FIG. 1 presents a schematic illustration of an exemplary foil, according to some embodiments of the present invention, showing foil 10, having perforated section 11, flanked on both sides thereof by intermediate perforated sections 12a and 12b, and nonperforated sections 13a and 13b, wherein the grey shade of perforated section 11 represents a fixed density of a hole pattern which covers the entire area of perforated section 11, the grey shade of non-perforated sections 13a and 13b represents a solid area with no holes therein which covers the entire area of each of non-perforated sections 13a and 13b, and the gradual greyscale of each of intermediate perforated sections 12a and 12b represent a gradual increase / decrease in hole pattern density, going from the high hole pattern density of perforated section 11 to the “no hole” solid area of non-perforated sections 13a and 13b;

[0059] FIGs. 2A-B present several exemplary embodiments of a perforation profile of the intermediate perforated section in a copper foil according to the present invention, each illustrated as a graph of the perforation parameters, i.e., the void area in a strip parallel to the longitudinal axis of the foil, as a function of the lateral, or horizontal, distance of the strip from the central longitudinal axis of the foil, the dashed vertical lines marking the interface between the perorated, intermediate perforated, and non-perforated sections, wherein FIG. 2A includes perforation profile 21 which shows a smooth linear transition, and perforation profiles 22 and 23 which each shows a different smooth non- linear transition, and FIG. 2B includes perforation profile 24 which shows a single step transition, perforation profile 25 which shows a multi-step linear transition and perforation profile 26 which shows a multi-step non-linear transition;

[0060] FIGs. 3A-C present several exemplary embodiments of a perforation profile of the intermediate perforated section in a copper foil according to the present invention, each illustrated as a graph of the perforation parameters, i.e., the number of holes in a strip parallel to the longitudinal axis of the foil, as a function of the lateral, or horizontal, distance of the strip from the central longitudinal axis of the foil, the dashed vertical lines marking the interface between the intermediate perforated and non-perforated sections, wherein FIG. 3A shows a non-linear decrease transition perforation profile, FIG. 3B shows a first multi-step linear decrease transition perforation profile, and FIG. 3C shows a second multi-step linear decrease transition perforation profile;

[0061] FIG. 4A presents a comparative example of a perforation scheme of copper foil 300, a part of which (from a mid-section to the left side thereof) is represented by a grey area, displaying perforated section 301 and non-perforated section 303, wherein copper foil 300 does not exhibit an intermediate perforated section; and

[0062] FIGs. 4B-D present three non-limiting illustrations of exemplary perforation scheme of copper foil 30, a part of which (from a mid-section to the left side thereof) is represented by a grey area, (as opposed to foil 300 in FIG. 4A which exemplifies a foil without an intermediate perforated section, including only perforated section 301 and non-perforated section 303), FIG. 4B shows foil 30 having gradual perforation section 32 that exhibits increasing vertical distance between holes and decreasing hole size, FIG. 4C shows foil 30 having intermediate perforated section 32 that exhibits increasing vertical and horizontal distance between holes and holes of the same size, and non-perforated section 33, and FIG. 4D shows foil 30 having intermediate perforated section 32 that exhibits a gradually a fixed distance between holes and decreasing hole size.

[0063] DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0064] The present invention, in some embodiments thereof, relates to metallic copper foils, and more particularly, but not exclusively, to perforated copper foils designed for use as current collectors as well as for mass production of electrodes comprising the same. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details set forth in the following description or exemplified by the Examples. The disclosure is meant to encompass other embodiments or of being practiced or carried out in various ways.

[0065] While developing methods for electrodepositing copper on drums designed to impart a perforation pattern on the resulting copper foil, the present inventors observed that copper foils having non-perforated margins flanking both sides along a perforated mid-section, were prone to tear at the perforated and the non-perforated interface when collected from the drum or processed thereafter. Such tearing resulted in a non-smooth (jagged) foil edge that increases the possibility of foil axial tearing and complicated handling during rolling, transportation and electrode coating. It was realized that it is advantageous to have the solid (non-perforated) margin attached to the foil when removing the foil from the drum and for future handling, until electrode is manufactured, at least until it is coated and, optionally, slitted.

[0066] Without being bound be any particular theory, it is assumed that one of the possible contributors to the above-described margin tearing at the perforation- solid interface in electrodeposited copper foils is the difference in current density on the drum’s solid edge during electrodeposition, compared to the perforated section, which might specifically affect the interface, leaving the perforated area that is next to the solid margin thinner, weaker, or having a different structure or density than the remaining perforated section. Another possible cause for the tearing phenomenon at the perforation -solid interface may be associated with the foil separation step, when the foil is being peeled off the drum by applying a certain amount of force, thereby potentially affecting the mechanical properties of the copper foil, including at said interface.

[0067] While conceiving the present invention, the present inventors envisioned a solution to the tearing problem in the form of an intermediate perforation section between the main perforated section of the foil and the solid margins thereof, wherein said intermediate section has a lower degree of perforation than the main perforated section. Said lower degree of perforation may be obtained by increasing the distance between holes of the perforations, while the hole size may remain the same. Alternatively, the lower degree of perforation may be obtained by decreasing the size (e.g., radii) of the holes of the perforations, while maintaining the distance between the holes the same. Further alternatively, the lower degree of perforation may be obtained by decreasing the hole size and increasing the distance therebetween. Throughout the present disclosure, the term "perforated section", when appearing on its own, refers to the main perforated section.

[0068] The intermediate section may have a constant degree of perforation or a varying (gradient) degree of perforation along the axial direction of the foil, wherein the degree of perforation decreases towards the solid margin of the foil. In some embodiments, the intermediate perforated section has a constant degree of perforation, having at least 1% less void area than the perforated section, optionally 5%, 10%, 20%, 25%, 50%, or 75% less void area than the perforated section. In some particular embodiments, the intermediate perforated section has a constant degree of perforation having at least about 50% less void area than the perforated section. In some embodiments, the constant degree of perforation is a seamless repeating pattern (SRP). In some further embodiments, as further detailed herein, the intermediate perforated section has a degree of perforation which decreases from the interface with the perforated portion to the interface with the non-perforated portion.

[0069] The pattern of the intermediate perforated section may differ from the pattern of the main perforated section in that a certain percent of the holes in the intermediate perforated section is eliminated as compared to the holes in the main perforated section. For example, while the main perforated section may include a symmetrical pattern of holes, the intermediate section perforation pattern may optionally be asymmetric or have a different symmetry axis.

[0070] A Long Copper Foil with Margins exhibiting Intermediate Decreasing Perforation:

[0071] The invention primarily concerns a long, continuous sheet of metal (e.g., copper) with a defined longitudinal axis, denoted "LI", that runs along machine direction (MD) when handled in a roll to roll fabrication. The longitudinal axis of the foil is referred to herein interchangeably also as the "vertical axis" or "length" of the foil. Positioned in the same direction as the longitudinal axis of the copper foil are one or more solid (nonperforated), sections, e.g., solid margin(s) positioned along one or both lateral edges of the copper foil. These solid margins refer to non-perforated sections of the foil, which extend from the lateral edges inward towards the central region of the foil. Each solid margin is separated from the central perforated section by a respective intermediate perforated section. The lateral direction, as used herein, refers to the direction on the foil surface which is perpendicular to the longitudinal direction, referred to herein interchangeably also as the "horizontal direction" or as the "width" of the foil. An example of an axis in the horizontal direction of the foil is shown in FIGs. 3B-D, denoted "L2".

[0072] The non-perf orated section may be located not along the edge of the foil, but rather between two main perforated sections. For example, such non-perf orated section may be used for allowing longitudinal slitting of the current collector foil. The non-perforated section is separated from the two main perforated sections by two intermediate perforated sections flanking the non-perforation section.

[0073] According to some embodiments of the present invention, provided is a long copper foil having a solid (non-perforated) margin along each of its lateral edges, a perforated section between the margins, wherein the interface between the solid margins and the perforated section is a section by itself that exhibits a constant perforation that is decreased as compared to the central perforated section, or a gradient of decreasing perforation (i.e., decreasing porosity) from more perforated to less perforated moving from the central section towards the margins. Each of the sections of the foil that are solid, or non-perforated, is referred to herein as the “non-perforated section”. According to some embodiments, the non-perforated section constitutes the longitudinal edge (also termed herein “margin”) of the foil, extending longitudinally on both sides of the foil.

[0074] Spanning the central region of the foil is a perforated section referred to as the “perforated section”, “central perforation section”, and “main perforation section”. This perforated section is characterized by the presence of holes or perforations that extend through the thickness of the foil from one surface to the other (also referred to as "through- holes", whereas perforation that do not extend through the entire thickness of the foil are referred to as "non-through-holes"). The holes may be arranged in a pattern with uniform spacings between the holes. It is noted that the perforated section correlates to the active section of the foil, namely the perforated section that preferably comprises a non-varying pattern of holes is the section of the foil that will eventually be coated with active electrode material and become the current collector in an electrode. In some embodiments, the perforation pattern of the perforated section follows the rules of a seamless repeating pattern (SRP), as defined hereinbelow. Alternatively, the perforated section may include a varying pattern of holes, however, such pattern does not exhibit an increasing or decreasing void area along the traverse direction of the foil. The perforated section may span between the solid margins of the foil (being separated therefrom by the intermediate perforated sections). The perforated section may also be divided into one or more perforated subsections by one or more non-perforated sections that are not positioned at the foil edges (and their adjacent intermediate perforated sections).

[0075] The interface between the non-perforated section(s), e.g., the solid margin, and the perforated section refers to the boundary or transition area where the non-perforated section meets the perforated section. This interface section, referred to herein as the “intermediate perforated section”, represents the region where the foil transitions from being non-perforated (e.g., solid margins; no porosity) to being perforated (perforated section; high porosity). By transition from non-perforated to perforated, it is meant that the intermediate perforated section is having an overall lower porosity compared to the perforated section, and may exhibit a pattern of holes that is not fixed across its lateral direction, but rather changing from being similar to that of the perforated section to no perforation (solid), or exhibits one or more step-wise reductions in porosity going from the perforated section to the non-perforated section.

[0076] A definition of the intermediate perforated section may be based on the relative average porosity of the intermediate perforated section and the central perforated section. For example, the average void area of the central perforated section may be at least 1% greater than the average void area of the intermediate perforated section.

[0077] In some embodiments, the foil is characterized by one central perforated section, two non-perforated sections extending longitudinally along each side of the foil constituting the foil’s margins, and two intermediate perforated sections extending longitudinally between the perforated section and each of the non-perforated sections, wherein the intermediate section has a lower porosity than the central perforated section. In some currently preferred embodiments, the intermediate perforated section connects the main perforated section and the non-perforated section.

[0078] In some additional embodiments, an intermediate perforated section may extend between two perforated sections (i.e., main perforated sections) connecting the two perforated sections. The term “non-perforated”, as used herein, refers, in some embodiments, to a solid region or a region having a very low degree of perforation (i.e., an average void area of 0-5%, 0-2%, 0-1%, 0-0.5% or 0-0.1%, provided that the average void area of the nonperforated section is lower than the average void area of the intermediate perforated section).

[0079] In some embodiments, the terms “non-perforated” and “perforated”, as used herein, are relative terms, which denote the difference in the average void area between the non-perforated section and the perforated section of at least about 200%. For example, if the non-perforated section has an average void area of 2%, the average void area of the intermediate perforated section would be 6% or higher. In some embodiments, the average void area of the perforated section is at least five- or ten-fold higher than that of the non-perforated section.

[0080] The intermediate section may be characterized by a single perforation pattern which porosity is lower than that of the central perforation section.

[0081] In some embodiments, the perforation pattern within the interface is characterized by a gradient of decreasing perforation (decreasing porosity), namely the intermediate perforated section, which signifies a step-wise and / or gradual and continuous change in the density and / or size of the holes. Specifically, this gradient involves a reduction in the number, size, or density of holes as one moves from the central perforated section towards each of the solid margins. In other words, the perforation holes become less frequent / dense and / or smaller as they approach the margins. This gradual change in the pattern can be smooth or step-wise, and it is expressed by the ratio of void-to-solid areas, as discussed hereinbelow, which can be manipulated via the size, and / or density of holes. The density of the holes may be altered (decreased or increased) gradually and / or step- wise by changing the distance between the centers of neighboring (adjacent) holes in a gradual fashion.

[0082] In a perforated copper foil, the area that is open or devoid of metal due to the presence of holes or perforations is referred to herein as the “void area”, which typically comprises a plurality of discrete and isolated voids; unless specified otherwise, the combined area of the plurality of individual voids is referred to herein as the “void area”, whereas a reference to an individual void is typically a reference to an individual hole. This void area allows for the passage of fluids or the infiltration of other materials. Conversely, the area that still contains the metal between the holes or perforations is referred to herein as the “solid area”, which is a continuous entity. The total area of a given perforated foil is the sum of all the void areas and the solid area. The solid area provides structural support and conductivity in the foil, making it essential for the foil's intended applications, such as serving as a current collector in a battery electrode.

[0083] The term “void area” may be expressed as a percentage of the plurality of individual voids out of the total surface area of the foil (including the void area and the solid area). In such instances, the terms “void area”, “porosity” and “degree of perforation” may be used herein interchangeably. The degree of perforation may be assessed as known in the art, for example by using suitable software linked to an imaging device that analyzes the total area of the holes and by dividing the total area of the holes by the total area of the analyzed foil.

[0084] The presently disclosed long copper foil, with its non-perforated solid margins and the intermediate perforated section exhibiting a gradient of decreasing ratio of void- to-solid at the interface between the perforated section and the non-perforated margins, is designed to address issues related to tearing and mechanical strength during manufacturing and subsequent handling, particularly in battery electrode applications. This configuration ensures a gradual transition from the central perforated section towards both margins, contributing to the foil's structural integrity and improved handling characteristics.

[0085] Thus, according to some embodiments of the present invention, there is provided a copper foil, which includes: at least one non-perforated section extending along a longitudinal direction of the foil; at least one perforated section extending along the longitudinal direction, laterally offset from the non-perforated section, and at least one intermediate perforated section positioned and extending longitudinally between the perforated section and the non-perforated section, said intermediate perforated section having a lower degree of perforation than the at last one perforated section.

[0086] The term “degree of perforation”, as used herein, refers to a ratio of the void area and total area of the copper foil, wherein when referring to a certain copper foil, a higher perforation density denotes a higher void area, and a lower degree of perforation denotes a lower void area of the foil.

[0087] In one non-limiting embodiment, the foil is an elongated sheet characterized by three types of longitudinal sections, including a single central perforated section running in a longitudinal direction, flanked on both its longitudinal edges by two non-perforated sections, each of which is separated from the central perforated section by one of two intermediate perforated sections, constituting five longitudinal sections, as depicted in FIG. 1.

[0088] FIG. 1 presents a schematic illustration of an exemplary foil, according to some embodiments of the present invention, showing foil 10, having perforated section 11, flanked on both sides thereof by intermediate perforated sections 12a and 12b, and nonperforated sections 13a and 13b, wherein the grey shade of perforated section 11 represents a fixed density of a hole pattern which covers the entire area of perforated section 11, the grey shade of non-perforated sections 13a and 13b represents a solid area with no holes therein which covers the entire area of each of non-perforated sections 13a and 13b, and the gradual greyscale of each of intermediate perforated sections 12a and 12b represent a gradual increase / decrease in hole pattern density, going from the high hole pattern density of perforated section 11 to the “no hole” solid area of non-perforated sections 13a and 13b.

[0089] According to some embodiments of the present invention, the width of at least one of the non-perforated sections ranges about 0.5-50% of the total width of the foil. Alternatively, the width of the non-perforated section(s) is about 0.5-40%, 0.5-30%, 0.5- 20%, 0.5-10%, or 0.5-5% of the total width of the foil.

[0090] In some embodiments, the width of the perforated section ranges about 50-99% of the total width of the copper foil. Alternatively, the width of the perforated section is about 60-99%, 70-95%, or 80-90% of the total width of the copper foil.

[0091] According to some embodiments of the present invention, the width of at least one intermediate perforated section ranges about 0.1-30% of the width of the copper foil. Alternatively, the width of the intermediate perforated section(s) is about 0.5-30%, 1- 20%, or 5-20% of the total width of the copper foil.

[0092] Although in some preferred embodiments the foil exhibits one central perforation section, flanked on both its longitudinal sides by two intermediate perforated sections, one on each side, and two non-perforated sections on both the longitudinal sides of the foil, as depicted in FIG. 1, it is to be understood that the scope of the present invention encompasses other configurations of foils, namely foil configurations that include additional longitudinal sections having additional perforation schemes and patterns.

[0093] The perforation properties of any given section of the foil may be defined relatively to the perforated section in terms of ratio of void-to-solid or in terms of percentage of void area of the toral area of the foil. When stating that the ratio of void- to-solid, or the void-to-solid ratio, decreases in a given section of the foil compared to another section thereof, it means that there are fewer and / or smaller holes in that given section compared to the other section. Similarly, one may consider the percentage of void area per foil area at any given section of the foil, and compare that to the percentage of void area per foil area at another section thereof. Since the intermediate perforated section may have a gradually (linearly or non-linearly) changing void-to-solid ratio, one of the perforation properties of the intermediate perforated section may be its average void area across the entire intermediate perforated section. The perforated section may also be defined by an average void area although it may exhibit the same hole density throughout the entire area.

[0094] In the context of the present invention, the hole density of a current collector relates to the number of through-holes per unit area. In some embodiments, the hole density relates to the ratio between the solid (e.g., metal) area and a void area of the holes per unit area.

[0095] For example, the intermediate perforated section may include a longitudinal region having a void area of 60% and another longitudinal region having a hole density of 30%, each spanning 50% of the intermediate perforation section width. The intermediate perforated section may thus be defined by an average value of the void area, that is calculated by multiplying the void area of each region by its relative width. Accordingly, in the present example, the average void is: 60*0.5 + 30*0.5, that is 45%. In another example, the intermediate perforated section may include a first longitudinal region having a void area of 60% and a second longitudinal region having a void area of 30%, wherein the first longitudinal section spans 10% and the second longitudinal section spans 90% of the intermediate perforation section width. In said exemplified embodiment, the average value of the void area of the intermediate perforated section is 33%.

[0096] Hence, the copper foil provided herein is characterized by an average void area of the perforated section that is at least about 1% greater than an average void area of the intermediate perforated section. This definition entails that the perforated section is perforated more densely than the intermediate perforated section by at least 1% or that an average of the opening size of the holes in the perforated section is at least about 1% larger than in the intermediate perforated section. In some embodiments, the average void area of the perforated section is at least about 5% higher than that of the intermediate perforated section. In further embodiments, the average void area of the perforated section is at least about 10% higher than that of the intermediate perforated section. In still further embodiments, the average void area of the perforated section is at least about 20% higher than that of the intermediate perforated section. In yet further embodiments, the average void area of the perforated section is at least about 25% higher than that of the intermediate perforated section. In still further embodiments, the average void area of the perforated section is at least about 40% higher than that of the intermediate perforated section. In yet further embodiments, the average void area of the perforated section is at least about 50% higher than that of the intermediate perforated section. In still further embodiments, the average void area of the perforated section is at least about 100% higher than that of the intermediate perforated section.

[0097] In some embodiments, the average void area of the perforated section ranges from about 5% to about 98% of the total area of said perforated section. In further embodiments, the average void area of the perforated section ranges from about 7% to about 90% of the total area of said perforated section. In still further embodiments, the average void area of the perforated section ranges from about 10% to about 80% of the total area of said perforated section. In yet further embodiments, the average void area of the perforated section ranges from about 15% to about 70% of the total area of said perforated section. In additional embodiments, the average void area of the perforated section ranges from about 20% to about 60% of the total area of said perforated section.

[0098] In some embodiments, the average void area of the intermediate perforated section ranges from about 0.1% to about 97% of the total area of said intermediate perforated section. In further embodiments, the average void area of the intermediate perforated section ranges from about 0.5% to about 80% of the total area of said intermediate perforated section. In still further embodiments, the average void area of the intermediate perforated section ranges from about 1% to about 70% of the total area of said intermediate perforated section. In yet further embodiments, the average void area of the intermediate perforated section ranges from about 5% to about 60% of the total area of said intermediate perforated section. In still further embodiments, the average void area of the intermediate perforated section ranges from about 7% to about 50% of the total area of said intermediate perforated section. In yet further embodiments, the average void area of the intermediate perforated section ranges from about 10% to about 40% of the total area of said intermediate perforated section. In still further embodiments, the average void area of the intermediate perforated section ranges from about 12% to about 20% of the total area of said intermediate perforated section. In yet further embodiments, the average void area of the intermediate perforated section ranges from about 12% to about 15% of the total area of said intermediate perforated section.

[0099] In some embodiments, the width of at least one non-perforated section ranges from about 0.5% to about 30% of the total width of the copper foil, or about 1% to about 20%, or about 5% to about 15%.

[0100] In some embodiments, the width of the perforated section ranges from about 70% to about 99% of the width of the copper foil, or about 50-95%, or about 60-90%, or about 70-85% of the width of the copper foil.

[0101] According to some embodiments of the present invention, each of the perforated section and the intermediate perforated section, individually exhibit a pattern of holes, namely the holes are not distributed randomly over the area of the sections.

[0102] In some embodiments, the pattern of the perforated section is a seamless repeating pattern. As used herein, the phrase “seamless repeating pattern” or “seamlessly repeating pattern”, abbreviated herein to “SRP”, refers to a pattern that spans an undefined and unlimited area or surface without visible transitions or boundaries. An SRP is a continuous repeating pattern of holes that consists of repeating elements arranged in a two-dimensional format, such as a geometric shape or a decorative design. An SRP continues indefinitely in all directions, creating a seamless visual effect. In the context of the present invention, an SRP can be defined by a repeating pattern unit, whereas placing a plurality of such units intimately adjacent (juxtaposed) to each other will afford the SRP. The repeating unit is referred to herein as a tile or a motif.

[0103] The motif is defined by one or more textural elements, whereas each motif blends into neighboring motifs to afford the SRP. In the context of the present invention, the motif includes textural elements in the forms of holes (i.e., through- holes, perforations, apertures, through-windows), whereas the entire SRP can be defined by the repeating motif. The arrangement of any given textural elements in the seamless repeating pattern characterizing the main perforated section (and / or optionally the intermediate perforated section) in some embodiments of the present invention, is controlled (non-random), as opposed to a random distribution of similar textural elements over a similar area; hence, the SRP characterizing the perforated section is non-random by definition.

[0104] The coverage of a planar surface, such as a surface of the perforated section, with the aforementioned SRP, essentially follows any standard tessellation or tiling approach, using one or more geometric shapes (tiles; motifs) with no overlaps and no gaps. In some embodiments, the SRP is afforded by a periodic tiling, whereas some embodiments include regular tiling with regular polygonal tiles, all having the same shape, and some embodiments include semiregular tiling with regular tiles of more than one shape and with every corner identically arranged.

[0105] The terms “motif’ or “tile”, as used herein, refer to the smallest and simplest single textural element, or non-repeating group of textural elements, the repetition of which forms and defines the SRP. In the context of the present invention, a motif is closely related to a unit cell in a 3D lattice (a crystal / lattice), whereas the SRP is form by repeating the motif in the plane to any direction on the plane. Within a motif there can one textural element, or multiple textural elements. In some embodiments, the motif includes multiple textural elements that relate to one another by symmetry operations in the 2D plane, such as translation, rotation and reflection transformation operations. In some embodiments, the motif includes multiple textural elements that are arranged non- symmetrically with respect to one-another, or multiple textural elements having different size / shape. It is to be understood that within a single tile the textural elements should not necessarily be arranged in a symmetrical or ordered manner. A flat plane, or SRP, can be fully tiled (covered) with triangular, rectangular and hexagonal polygons (tiles), each having one or more textural elements arranged within. Rectangular and hexagonal tiles can be placed using the same tile orientation (only translation, no rotation), while triangular tiles are placed with a 600rotation (translation and rotation). An example of a simple motif is a round dot, the expression of which can be a round hole, whereas its SRP can be a square or hexagonal circle packing where the circles are evenly spaced, and in the case of holes, do not touch each other to allow continuous material therebetween).

[0106] The void area and / or density of a hole (hole density) may depend inter alia on the size of the holes and the distance between adjacent holes. In the context of the present invention, the hole density of the perforated section relates to the number of holes per unit area. In some embodiments, the hole density relates to the void-to-solid ratio per unit area.

[0107] According to some embodiments, the diameter of the holes (hole opening size) in the perforated section may be as small as 10-200 pm. In some embodiments, size of the holes ranges from 10 pm to 5000 pm, or about 10-2000 pm, or about 10-1000 pm, or about 10-100 pm, or about 10-50 pm, or 20-100 pm, 30-100 pm, 40-100 pm, 50-100 pm, 60-100 pm, 70-100 pm, 80-100 pm, 90-200 pm, 90-300 pm, 90-400 pm, or about 90- 500 pm. In some embodiments, the size of a hole is less than about 1,000 pm, less than about 750 pm, less than about 500 pm, less than about 250 pm, less than about 100 pm, less than 90 pm, less than 80 pm, less than 70 pm, less than 60 pm, less than 50 pm, less than 40 pm, less than 30 pm, less than 20 pm, less than 15 pm, less than 10 pm, less than 9 pm, less than 8 pm, less than 7 pm, less than 6 pm, less than 5 pm, or less than 4 pm.

[0108] According to some embodiments, the hole density in the perforated section ranges from 4 holes per 1 mm2(square millimeter) to 400 holes / mm2(4-400 holes / mm2). In some embodiments, the hole density ranges 5-250 holes / mm2, or 10-200 holes / mm2.

[0109] In some embodiments, including any of the foregoing, the holes have an opening (aperture; opening size) dimension of about 10-200 pm x about 10-200 pm, about 20-150 pm x 20-150 pm, or about 30-100 pm x 30-100 pm.

[0110] Given a fixed hole size, the distance between two adjacent holes may also be used to define the hole density and / or void area in the perforated section. Since the foil is an elongated member, the distance between two adjacent holes in the plane of the foil is defined with reference to the foil’s longitudinal direction, namely the distance is referred to in terms of the vertical distance and the horizontal distance, wherein vertical distance aligns with the longitudinal axis of the foil (i.e., in the longitudinal direction), and the horizontal distance aligns with the transverse axis of the foil (along its width, in the lateral direction). In some embodiments, the vertical and / or horizontal distance between the centers of two adjacent holes ranges 1-1000 |im, or about 10-100 |im, or 20-100 |im, 30- 100 |im, 40-100 |im, 50-100 |im, 60-100 |im, 70-100 |im, 80-100 |im, or about 90-100 |am. In some embodiments, the vertical and / or horizontal distance between the center of two holes in the perforated section is about 5 pm, 6 pm, 7 pm, 8 pm, 9 pm, 10 pm, 20 pm, 30 pm, 40 pm, 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, or about 100 pm, 110 pm, 120 pm, 130 pm, 140 pm, 150 pm, 160 pm, 170 pm, 180 pm, 190 pm, or about 200 pm, 210 pm, 220 pm, 230 pm, 240 pm, 250 pm, 260 pm, 270 pm, 280 pm, 290 pm, 300 pm, 310 pm, 320 pm, 330 pm, 340 pm, 350 pm, 360 pm, 370 pm, 380 pm, 390 pm, or about 400 pm, 450 pm, 500 pm, 550 pm, 600 pm, 650 pm, 700 pm, 750 pm, 800 pm, 850 pm, about 900 pm, 950 pm, or about 1,000 pm.

[0111] The term “opening size”, as used herein, refers, in some embodiments, to a value corresponding to a length of the hole in the largest dimension thereof. For example, for an essentially circular hole, the opening size should coincide with its diameter, for a square hole, the hole opening would be the length of its diagonal, and for an oval hole, the opening size would be defined as the length of its major axis. In some embodiments, the term “opening size” refers to a diameter of a circle that encloses an opening defined by its surrounding solid material.

[0112] The hole opening size of the foil (or of a current collector made from the foil) may be measured using various techniques depending on the precision and hole size, including but not limited to an optical microscope or SEM. Both top view and cross-sectional foil samples can be analyzed by optical and electron microscopy. Particle Sizing Analysis techniques such as laser diffraction or dynamic light scattering may also be employed to indirectly measure the hole sizes by analyzing the size distribution of particles that pass through the foil.

[0113] The above techniques allow measuring opening sizes of a plurality of individual holes, and / or an average hole opening size value of a tested number of holes. As the perforated copper foil includes a plurality of holes, which sizes may differ (even if only slightly), the term “opening size” as used herein, generally refers to a mean opening size of a plurality of holes of the perforated foil rather that to an individual hole, unless indicated otherwise. The terms "mean opening size” or “average opening size”, used herein interchangeably, refer to the average size of the hole openings in a perforated foil, which may be measured as part of a size distribution analysis or calculated manually. To determine the mean hole opening, one of the methods mentioned hereinabove, such as optical microscopy, image analysis software, or SEM, can be used to measure the individual sizes of multiple holes across a sample of the perforated material. These measurements are then aggregated to calculate the average size, providing insight into the typical dimension of the holes in the perforated foil.

[0114] The hole opening size of a plurality of holes may also be measured by taking a picture from the surface side of the perforated current collector foil with a bottom light source of parallel or non-parallel light using an optical microscope or a camera with the suitable resolution, wherein each hole is captured with transmitted light. The entire width of the foil may be analyzed in-situ (during foil manufacturing or electrode coating) or ex- situ by image analysis software to calculate a mean opening size of the plurality of holes within a certain longitudinal section of the foil or along the entire length thereof.

[0115] The void area of the copper foil may be assessed by imaging a certain area of the foil by image analysis software, as described hereinabove with respect to measuring hole opening size, and calculating a ratio of the total opening area of the through-holes to an area of the imaged geometric area. Similarly, a hole density may be assessed by calculating the number of holes within said certain area and dividing said number by the imaged geometric area. These operations may be performed in multiple locations (such as 2, 3, 5, 10 or more locations) by changing the observation position, and an average of the open area and of the hole density may be obtained.

[0116] The above mentioned hole measuring and / or void measuring techniques may be used to measure at least one of the hole opening size, hole density, and void area of the main perforated section and / or of the intermediate perforated section. In some embodiments, particularly when the holes of the main perforated section have a SRP, a single location of the main perforated section, including at least 2, at least 3, at least 4, at least 6, at least 9, or at least 16 holes, may be sufficient to establish the average hole size, density, or average void area. Each possibility represents a separate embodiment. The measured location may optionally have a substantially circular or square shape, but may alternatively also have a rectangular, hexagonal, oval, or any other relevant shape which spans a sufficient number of holes. According to some embodiments, the above-mentioned techniques may also be used to identify or distinguish between a main perforated section of the foil and an intermediate perforated section. For example, operations according to any one of the measuring techniques may be performed in a series of locations (such as 2, 3, 5, 10 or more locations) which locations form a lateral sequence, and a comparison may be made between the measurements in each location. For instance, when 2 or more locations which are sequentially laterally displaced produce the same measurements, it can be understood that the 2 or more locations are within a main perforated section. Conversely, when 2 or more locations, which are sequentially laterally displaced, produce different measurements, it can be understood that the locations lie within an intermediate perforated section having a gradual decrease in hole density, or that the 2 or more locations span the transition from the main perforated section to the intermediate perforated section or from the intermediate perforated section to the solid section.

[0117] Intermediate perforation:

[0118] Since the main purpose of manufacturing the foil as provided herein is for its perforated section, that may be used as a current collector in a battery electrode, the perforation pattern of this section is designed purposely and controlled meticulously, while the pattern in the intermediate perforated sections smooths the transition between said pattern and the solid margin.

[0119] In some embodiments, the intermediate perforated section starts with the same pattern as in the central perforated section, which gradually and / or step-wise morphs into the solid non-perforated sections (e.g., the foil’s margins or longitudinal edges).

[0120] The change in the perforation parameters in the intermediate perforated section may follow a smooth profile or a step-wise profile, a linear or a non-linear gradient profile. A smooth profile implies a gradual transition in the perforation parameters within the intermediate section. The smooth gradual transition of the perforation parameters moving from the perforated section to the non-perforated section(s) may be further characterized by a linear transition or a non-linear transition. In contrast, a step-wise profile involves discrete, well-defined changes in perforation parameters along the traverse direction of the foil, essentially partitioning the intermediate perforated section into subsections. A step-wise transition may be afforded by one or more steps (subsections), each step or subsection is characterized by a discrete, well-defined change in perforation parameters (porosity) compared to the neighboring section or the previous step. A linear gradient signifies a consistent change in perforation parameters, such as hole size or density, along the length of the intermediate section. Non-linear gradients involve, inter alia, irregular or exponential changes in perforation parameters. In embodiments wherein the intermediate perforated section is characterized by more than one step in the step-wise transition of perforation parameters within the intermediate perforated section, this step-wise transition may follow a linear transition or a non-linear transition, pertaining to the values of the perforation parameters.

[0121] Hence, the intermediate perforated section may be characterized by one of: a smooth and linear gradient of decreasing perforation; a smooth and non-linear gradient of decreasing perforation; a linear step-wise gradient of decreasing perforation; or a non-linear step-wise gradient of decreasing perforation.

[0122] In some embodiments, the intermediate section is defined by a single step transition from the perforation parameters of the perforated section and the nonperforated section(s). In such embodiments, the foil may be defined as having at least three types of sections, each characterized by a fixed (non-transitioning) set of perforation parameters, wherein the perforated section is characterized by first higher perforation (e.g., higher average void area) compared to the intermediate perforated section characterized by second intermediate perforation, and the non-perforated section characterized by third “no perforation”. In other words, the intermediate perforated section is characterized by a linear step-wise gradient of decreasing perforation or a nonlinear step-wise gradient of decreasing perforation, wherein the gradient is a single step gradient, as shown in FIG-2B, perforation profile 24.

[0123] FIGs. 2A-2B present several exemplary embodiments of a perforation profile of the intermediate perforated section in a copper foil according to the present invention, each illustrated as a graph of the perforation parameters, i.e., the void area in a strip parallel to the longitudinal axis of the foil, as a function of the lateral, or horizontal, distance of the strip from the central longitudinal axis of the foil, the dashed vertical lines marking the interface between the perorated, intermediate perforated, and non-perforated sections, wherein FIG. 2A includes perforation profile 21 which shows a smooth linear transition, and perforation profiles 22 and 23 which each shows a different smooth nonlinear transition; and FIG. 2B includes perforation profile 24 which shows a single step transition, perforation profile 25 which shows a multi-step linear transition and perforation profile 26 which shows a multi-step non-linear transition. It is to be understood that the intermediate perforated section spans between the first longitudinal section that is adjacent to the main perforated section and has a lower void area than that of the main perforated section and the first longitudinal section that is adjacent to the nonperforated section and has a higher void area than that of the non -perforated section (as indicated by the two dashed lines in FIG. 2).

[0124] The term “strips”, as used herein, may refer to continuous longitudinal foil sections which make up the main perforated, intermediate perforated, and solid sections of the foil of the present invention, the strips having a unform width. In some embodiments, each strip includes not more than a single through-hole across its width (i.e., in the lateral direction of the strip). In some further embodiments, at least some of the strips may include more than one hole across their width.

[0125] FIGs. 3A-C present several exemplary embodiments of a perforation profile of the intermediate perforated section in a copper foil according to the present invention, each illustrated as a graph of the perforation parameters, i.e., the number of holes in a strip parallel to the longitudinal axis of the foil, as a function of the lateral, or horizontal, distance of the strip from the central longitudinal axis of the foil, the dashed vertical lines marking the interface between the intermediate perforated and non-perf orated sections. FIG. 3A shows a multi-step non-linear decrease transition perforation profile, wherein within each step there are strips with different void areas, such that, for example, a strip that is closer to the solid margin may have a higher void area than a strip that is closer to the perforated section, as long as the overall void area within each step is lower than the void area of the adjacent step that is closer to the perforated section. FIG. 3B shows a first multi-step linear decrease transition perforation profile in which each step includes two strips, wherein within each step a strip that is closer to the solid margin has a lower void area than its adjacent strip that is closer to the perforated section, and FIG. 3C shows a second multi-step linear decrease transition perforation profile, having less steps than the profile of FIG. 3B, i.e., in which each step includes two strips, wherein within each step the strips have the same void area. In general, the perforated section and the intermediate perforated section differ by any one of the following perforation parameters, or any combination thereof: hole size, void area (or void-to-solid ratio), hole density, and vertical and / or horizontal distance between adjacent holes. In other words, the intermediate perforated section is a transition zone between the perforated section and the non-perforated section. The perforation parameters in the intermediate perforated section change in a single step or gradually (either smoothly or in steps), from the values in the perforated section to the values in the non-perforated section.

[0126] The perforation parameters can be any of the following:

[0127] Hole size: The diameter of the holes in the foil;

[0128] Void area (or void-to-solid ratio): The percentage of the foil that is open space, due to the holes;

[0129] Hole density: The number of holes per unit area of the foil; and / or

[0130] Vertical and / or horizontal distance between adjacent holes: The spacing between the holes in the foil.

[0131] The choice of perforation parameters and the profile of the change in perforation parameters will depend on the specific application of the foil. For example, an intermediate perforated section with a smooth profile may be desired for applications where a gradual transition is required. An intermediate perforated section with a step- wise profile may be desired for applications where a more abrupt change is required or is sufficient for preventing solid margin detachment or tearing.

[0132] In some embodiments, the perforated section and the intermediate perforated section have about the same hole size (the same hole size) and a different average hole density, meaning that the intermediate perforated section exhibits the same holes as the perforated section, but at a lower hole density, whereas the hole density may be expressed in the number of holes per unit area, or the vertical and / or horizontal distance between adjacent holes, or the void area.

[0133] In some embodiments, the perforated section and the intermediate perforated section have about the same hole density and a different average hole size, meaning that the intermediate perforated section exhibits the same hole density as the perforated section, but smaller holes, whereas the hole density may be expressed in the number of holes per unit area, or the vertical and / or horizontal distance between adjacent holes, or the void area.

[0134] In some embodiments, the perforated section and the intermediate perforated section have different average hole size and a different hole density, whereas the hole density may be expressed in the number of holes per unit area, or the vertical and / or horizontal distance between adjacent holes, or the void area.

[0135] If the perforated section is defined by a specific hole density, the perforated section may be defined as exhibiting a first hole density and the intermediate perforated section may be defined as exhibiting a second hole density, wherein the second hole density is lower than the first hole density by a specific value, which can be expressed as a percentage of the first density.

[0136] For example, the intermediate perforated section may have a varying hole density across the width of the intermediate perforated section (along the traverse direction of the foil). For example, the intermediate perforated section may include a longitudinal region having a hole density of 60 holes / mm2and a longitudinal region having a hole density of 30 holes / mm2, each spanning 50% of the intermediate perforation section width. The intermediate perforated section may be defined by end values of the intermediate perforation section, namely a first value (an initial value; juxtaposed to the perforated section, that is 60 holes / mm2in the exemplified embodiment) and a second value (a final value; juxtaposed to the non-perforated section, that is 30 holes / mm2in the exemplified embodiment). The intermediate perforated section may further be defined by an average value of the hole density, that is calculated by multiplying the hole density of each region by its relative width. Accordingly, in the above example the average hole density is: 60*0.5 + 30*0.5, that is 45 holes / mm2. In another example, the intermediate perforated section may include a first longitudinal region having a hole density of 60 holes / mm2and a second longitudinal region having a hole density of 30 holes / mm2, wherein the first longitudinal section spans 10% and the second longitudinal section spans 90% of the intermediate perforation section width. In said exemplified embodiment, the average value of the hole density of the intermediate perforated section is 33 holes / mm2.

[0137] The intermediate perforated section may also be defined based on other features of the pattern, such as hole size and distance between adjacent holes, including the end values or the average value, as explained hereinabove. For another example, in some embodiments, the average void area of the perforated section may range about 5-98% of the total area of the perforated section. In such embodiments and in general, the average void area of the intermediate perforated section ranges about 0.1-97% of the total area of said intermediate perforated section, correspondingly with respect to the average void area of the perforated section.

[0138] In some embodiments the seamless repeating pattern is characterized by an average hole size ranging 10-2000 pm and / or a hole density ranging 4-400 holes / mm2. In such and other embodiments, the intermediate perforated section may be characterized by holes having an average hole size ranging 10-1800 pm and / or a hole density ranging 4-300 holes / mm2.

[0139] The holes in the intermediate perforated sections may also be of a different shape and relative orientation compared to the holes in the perforated section. For example, the holes in the intermediate perforated sections may be elliptical, while the holes in the perforated section are circular. The holes in the intermediate perforated sections may also be oriented at an angle, while the holes in the perforated section are oriented perpendicular to the foil.

[0140] FIGs. 4A-D present four non-limiting illustrations of exemplary perforation scheme of copper foil 30, a part of which (from a mid-section to the left side thereof) is represented by a grey area, FIG. 4A is a comparative example of copper foil 300 not exhibiting a intermediate perforated section, and displaying perforated section 310 and non-perf orated section 330. FIG. 4B shows foil 30 having intermediate perforated section 32 that exhibits increasing vertical distance between holes and decreasing hole size, FIG. 4C shows foil 30 having intermediate perforated section 32 that exhibits increasing vertical and horizontal distance between holes and holes of the same size, and nonperforated section 33, and FIG. 4D shows foil 30 having intermediate perforated section 32 that exhibits a gradually a fixed distance between holes and decreasing hole size.

[0141] In some embodiments, the pattern of the intermediate perforated section is non seamless (i.e., does not extend equally in all directions within the intermediate perforated section). In some embodiments, the pattern of the intermediate perforated section is not repeating (i.e., there may be a difference in the pattern of elements that make up the entire pattern of the intermediate perforated section). Furthermore, as mentioned hereinabove, the reduction of the void area of the intermediate perforated section may be achieved by eliminating a certain percent of the holes in the intermediate perforated section as compared to the holes in the main perforated section. The holes may be eliminated in an organized or random manner.

[0142] For example, the number of holes may be eliminated in a step-wise manner, such that each consecutive step that is closer to the solid margin has a smaller number of holes, wherein within each step hole elimination may be gradual or sporadic.

[0143] In one example, the foil may be designed to include an intermediate perforated section that has a width X, wherein the number of holes is reduced along the axial direction of the foil from the main perforated section towards the solid margin such that a certain percent of the holes (Y%) are eliminated every Y% of the intermediate perforated section (i.e., Y%*X), while maintaining the original distance between the holes (where the holes are not eliminated). Said certain percent (Y%) may be, inter alia, 1%, 5%, 10% or 20%. For example, the number of holes within the intermediate perforated section may be reduced along the axial direction of the foil such that 10% are eliminated every 10% of the intermediate perforated section (0.1*X).

[0144] According to some embodiments, the number of holes within said Y%*X regions is eliminated in an irregular manner, e.g., a strip within one such region that is closer to the solid margin of the foil may have a higher density of holes than a strip within said region that is closer to the perforated section, as long as the overall design of the gradient of the intermediate perforated section fulfils the above condition (Figure 3 A).

[0145] According to some embodiments, the number of holes within said 0.1 *X regions is eliminated in a gradual manner, i.e., each strip within one 0.1 *X region that is closer to the solid margin of the foil has a lower density of holes than its adjacent strip within said 0.1*X region that is closer to the perforated section (Figure 3B).

[0146] According to some embodiments, the number of holes within said 0.1 *X regions is constant, i.e., each strip within one 0.1 *X region that is closer to the solid margin of the foil has the same density of holes than its adjacent strip within said 0.1 *X region that is closer to the perforated section (Figure 3C).

[0147] In some exemplary embodiments, the copper foil includes a 5 mm intermediate section between the main perforated section and the solid margin, wherein the number of holes is reduced along the axial direction of the foil such that approximately 10% of the holes are eliminated every 0.5 mm, while maintaining the original distance between the holes (where the holes are not eliminated).

[0148] While reducing the present invention to practice it has been observed that mechanical stability of the foil is increased when the perforation parameter that was gradually changed in the intermediate perforated section, compared to the perforated section, was the hole density. Gradually increasing the vertical and / or horizontal distance between adjacent holes in the intermediate perforated section while maintaining the same hole size and shape as in the perforated section, reduced the stress at the margins of the perforated section and resulted in a more workable piece.

[0149] The copper foil may further include a plurality of non-piercing textural elements on the surface thereof, e.g., a plurality of peaks and valleys, as disclosed in WO 2023 / 148737, which is incorporated herein by reference.

[0150] In some embodiments, the copper foil is corrugated, i.e., has corrugation elements. The term “corrugation”, as used herein, refers in some embodiments, to a plurality of both embossed and debossed textural elements that bestow a patterned texture, regular surface roughness and / or regular surface undulations. A corrugated current collector may combine both embossment and debossment elements, “dual-level embossing" and / or "dual-level debossing", referring to the creation of both raised and recessed textural elements within the same design on a material. In some embodiments, the corrugation elements are regular in size, shape, spacing, and relative orientation. According to some embodiments, the corrugation elements are arranged in a seamless repeating pattern.

[0151] A corrugation element can perturb the surface on one side thereof, and be a bulge (e.g., peak) or a depression (e.g., valley), depending on the definition of the opposite sides of the copper foil. Corrugation elements may be divided into a group of isolated elements, such that may form a single local bulge, and a group of extended elements, such that may form a ridge across the foil, ending at the edge of the foil. For example, a corrugation element may include a combination of rounded bulges and depressions, which are arranged in a chess-board pattern, i.e., each bulge (other than bulges located at the edges of the copper foil) is surrounded by four adjacent depressions and each depression (other than depressions located at the edges of the copper foil) is surrounded by four adjacent bulges. Additionally, a corrugation element may include a combination of rounded bulges and depressions, which are arranged in a hexagonal pattern, i.e., each bulge (other than bulges located at the edges of the copper foil) is surrounded by three adjacent depressions and each depression (other than depressions located at the edges of the copper foil) is surrounded by three adjacent bulges. Alternatively, a corrugation element can span any length with respect to the size of the copper foil, namely a valley or a peak can run from edge to edge while forming a part of an SRP of parallel waves. The longitudinal axis of the extended corrugation element may be oriented perpendicular to the longitudinal axis of the copper foil or may be tilted at any angle with respect to the longitudinal axis, as well as parallel to the longitudinal axis of the copper foil.

[0152] In some embodiments, the corrugation elements comprise periodically alternating peaks and valleys. In some embodiments, the corrugation elements comprise periodically alternating round bulges and depressions.

[0153] Without wishing to being bound by theory or mechanism of action, it is contemplated that the perforated foil having non-perforated margins flanking both sides along a perforated mid-section, that is subjected to a corrugation (or embossment) process, is particularly prone to tear at the perforated and the non-perforated interface. The foils of the present invention that include the intermediate perforation section are therefore particularly beneficial when three dimensionally-formed copper foils are concerned.

[0154] Foil and electrode manufacturing:

[0155] The non-uniformly perforated copper foil provided herein may be produced by any known method, including subtractive and additive foil-forming methodologies, as these are known in the art.

[0156] International patent application No. WO2023 / 148736 by the present assignee and incorporated herein by reference, provides perforated copper foils for use as current collectors in battery electrodes, as well as methods of producing the same. These methods are relevant in the context of the present invention, while implementing the perforation scheme(s) as provided herein.

[0157] As discussed herein, one of the objectives of the present invention is to provide a uniformly perforated copper foil, specifically designed for a roll-to-roll electrode manufacturing configuration. The foils provided herein are designed to sustain the stresses which may be applied on the foil before or in the course of electrode preparation thereon. One of the steps in forming an electrode, includes applying an electrode active material slurry to the uniformly perforated copper foil, thereby forming the electrode.

[0158] A roll:

[0159] The perforated copper foil provided herein is very thin (e.g., 1-50 pm), highly flexible, and due to the innovative perforation design strategy provided herein, namely the decrease in perforation near the edges of the foil, it can be easily bent, folded, and shaped without breaking, and it can withstand a variety of stresses and forces during the electrode manufacturing process. Hence, due to these properties, as well as the requirements of the manufacturing and utilization industries, one of the optimal formats to handle the copper foil provided herein is in the form of a roll.

[0160] A roll of a long strip of the copper foil provided herein can be described as a cylindrical shaped article, which is made up of a thin copper foil that has been wound around an axis, which is the traverse axis of foil. The roll is typically of a fixed width and can be of several tens, hundreds, thousands and even tens of thousands of meters in length. The roll of the copper foil provided herein can be packaged with protective materials to avoid any damage during the transportation and storage.

[0161] The perforated copper foil provided herein can be rolled onto a core tube or a hollow cylinder having an inner diameter and an outer diameter which can be selected to suit the manufacturing and utilization settings.

[0162] Thus, according to an aspect of the present invention, there is provided a roll comprising a cylindrical core and the copper foil provided herein wound around the core. The roll is made up of a central cylindrical support, typically made of cardboard, plastic or metal, and the member provided herein is wrapped around the core. The core is typically hollow and provides the necessary support for the roll, while the member is the material that is used for producing, for example, electrodes for batteries. The roll can be of different sizes and the member can be of different thicknesses, depending on the specific application.

[0163] In some embodiments, a single continuous perforated copper foil, exhibiting the perforation design described herein and provided in the form of a roll, has any fixed width, e.g., 0.1-5 meters wide, and any length, such as, for example, at least 0.5 m, 1 m, 10 m, 30 m, 50 m, at least 100 m long, at least 500 m long, at least 1,000 m long, or at least 0.5- 100 m long, at least 50-500 m long, or at least 100-1,000 m long, and in some embodiments, at least 1-5 kilometer long.

[0164] Current collector:

[0165] Current collectors (CCs) have general roles in battery systems: (i) because the typical electrodes are fabricated by casting slurry (a mixture of active material, polymeric binder, and carbon additive) on CCs, CCs support the electrode layer and (ii) CCs offer electrical paths to deliver electrons between the electrode materials and the external circuit. By controlling the properties of the CC, the following effects can be obtained: (i) the lower the thickness and the higher the strength, the more active materials can be stacked in a limited space, resulting in a high volumetric energy density; (ii) by strengthening the connection between the active material and CC with a broad contact area, additional electron pathways can be achieved, thus reducing the internal resistance of the cell. In Li-ion batteries, Cu foil is generally used as an anode current collector and Al foil is used as a cathode current collector.

[0166] The present invention provides a copper foil that exhibits at least one major section that is characterized by uniform (e.g., SRP) perforation, thereby allowing loading larger amounts of active material slurry thereon, increasing the surface area of contact between the active material and the CC, and exhibiting uniformity over the entire area of the CC, thereby reducing delamination of active material, cracking, swelling, adverse formation of “hot-spots” and other mechanical failures that lead to battery malfunction.

[0167] The current collector according to the principles of the present invention may be manufactured by a low-cost and rapid continuous process and provided in industrial- size rolls, conducive to the machinery and processes employed in contemporary and advanced electrode and battery industry.

[0168] Thus, according to an aspect of some embodiments of the present invention, there is provided a current collector, in the sense of a part of an electrode that collects electrons from electrode materials and transports them to an external circuit (and vice versa), wherein the CC consists or comprises at least the perforated section of the copper foil provided herein. In some embodiments, the current collector includes the perforated section and the intermediate perforation section. In some embodiments, the current collector includes the perforated section, the intermediate perforation section, and at least a portion of the non-perforated section. As used herein, the term “current collector” (abbreviated as “CC”) refers to a substrate that conducts electrons from and / or to the cathode and anode in a sufficient manner to be used in a battery or electrochemical cell to complete an electrical circuit. The CC, and hence the metallic foil provided herein, is typically made of a metal such as copper, aluminum or nickel. Other metals such as magnesium, tungsten, cobalt, iron, titanium, platinum, tungsten and gold, and any alloy thereof, may also be used, as well as alloys or combinations of metals, such as steel. In some preferred embodiments, the CC, and foil, is made of copper. In the context of a secondary battery, the CC in the cathode conducts electrons into the cathode during a discharge and conducts electrons out of the cathode during a charge, whereas in an anode, the CC conducts electrons into the anode during a charge and conducts electrons out of the anode during a discharge.

[0169] The current collector provided herein may further include contacts and contact leads, terminals and other features common and / or needed as part of a current collector, or needed for its assembly and implementation in an electric device, and these additional features, all or any selection thereof, are encompassed in the definition of a current collection, as used herein.

[0170] According to an aspect of some embodiments of the present invention, there is provided a current collector suitable for use in an electrode, such as e.g., in a battery, which includes at least the perforated section of the copper foil provided herein, wherein the copper foil is produced by a continuous manufacturing process, and characterized by having at least one intermediate perforated section and at least one non-perf orated section, as described hereinabove, wherein the perforated section may be separated from the intermediate perorated section, or the intermediate perforated section may be separated from the non-perf orated section. .

[0171] Electrode manufacturing process:

[0172] The manufacturing process of lithium-ion battery electrodes, starting with a roll of perforated copper foil for the current collector, involves several key steps, which are described hereinbelow. For the sake of clarity, the exemplary process refers to a copper foil, which is manufactured by electrodeposition, however, it should be noted that the present invention is not limited to a particular metal, or to a particular foil perforation and manufacturing methodology, as other metals, such as aluminum, and other foil manufacturing methodologies, such as laser engraving, mechanical punching, electrochemical etching, chemical etching, or electric discharge machining are contemplated and included in the scope of the present invention.

[0173] An electrode that is based on the perforated current collector according to the various embodiments of the present invention may be manufactured as follows:

[0174] Preparation of Copper Foil:

[0175] The copper foil used as the current collector may be prepared through an electrodeposition process. In this process, the copper foil may be deposited on a conductive (e.g., titanium or stainless-steel) rotating drum from a copper solution where it is connected to a voltage source. The drum exhibits a surface that is conducive to forming the copper foil provided herein, namely exhibit sections that correspond to the perforation of the various sections of the copper foil, as described hereinabove, by including electrically insulating isles corresponding to the intended foil perforations, and has continuous electrically conducting margins (that do not contain electrically insulating isles). The drum is connected to the negative pole of the voltage source, and the anode is submerged in the copper electrolyte solution facing the drum.

[0176] According to some aspects and embodiments of the present invention there is provided a method of forming a copper foil comprising: i) exposing at least a portion of a drum having a patterned lateral surface to an electrolyte comprising copper ions, ii) connecting the drum to a negative pole of a power source, wherein an anode that faces said portion of the drum, and is exposed to said electrolyte, is connected to a positive pole of the power source, iii) rotating the drum and continuously separating the copper foil that is electrically deposited thereon from the drum, wherein the patterned lateral surface comprises at least one circumferential nonpatterned section, at least one circumferential patterned section comprising electrically insulating regions (also referred to as “main circumferential patterned section”), and at least one circumferential intermediate patterned section comprising electrically insulating regions, said intermediate patterned section positioned and extending longitudinally between said patterned section and said non-patterned section, wherein the electrically insulating regions of the patterned section occupy an area that is at least about 1% greater than an area occupied by the electrically insulating regions of the intermediate patterned section.

[0177] In some embodiments, a metal foil is electroformed on a mandrel, which may be flat or have other shapes, such as a cylindrical drum (cylinder). The terms “drum”, “cylinder” and “mandrel” are used herein interchangeably to refer to curved surface on which a copper foil can be formed, as described herein.

[0178] In some embodiments, patterning the lateral surface of the drum is achieved by machining, such as mechanical machining, etching, milling, laser machining, or any combination thereof to form a plurality of recesses. The recesses may then be filled with a dielectric material. Electrodepositing copper of such a patterned surface results in an electrochemical deposition (electroforming) of the metal occurring on the electric conducting mandrel surfaces but not on the non-conductive dielectric material, where a hole is formed. The dielectric material may include various types of plastics, polymers, glues, epoxy resins and other non-conductive materials.

[0179] In some embodiments, the diameter of the drum / cylinder / mandrel is about 100 mm, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1,000 mm, 200 cm, 300 cm, 400 cm, 500 cm, 600 cm, 700 cm, 800 cm, 900 cm, or about 1-4 m, about 2 m, 3 m, 4 m, or a diameter of about 5 m.

[0180] In some embodiments, the at least one circumferential patterned section includes electrically insulating regions arranged in an SRP around its circumference. The electrically insulating regions may be of any shape and size, according to the designed motif. In some embodiments, the electrically insulating regions of the at least one circumferential patterned section are approximately circular and have a diameter that ranges 1-500 pm. In some embodiments, the electrically insulating regions have a diameter of about 1 pm, or a diameter of about 1-10 pm, 10-20 pm, 20-30 pm, 30-40 pm, 40-50 pm, 50-60 pm, 60-70 pm, 70-80 pm, 80-90 pm, 90-100 pm, 100-110 pm, 110-120 pm, 120-130 pm, 130-140 pm, 140-150 pm, 150-160 pm, 160-170 pm, 170-180 pm, 180-190 pm, 190-200 pm, 200-220 pm, 220-240 pm, 240-260 pm, 260-280 pm, 280- 300 pm, 300-220 pm, 300-350 pm, 350-400 pm, 400-450 pm, or about 450-500 pm in diameter.

[0181] In some embodiments, the at least one circumferential intermediate patterned section includes electrically insulating regions arranged around its circumference in a different pattern than the main circumferential patterned section. The electrically insulating regions of the circumferential intermediate patterned section may be of any shape and size, according to the designed motif. In general, the main circumferential patterned section and the circumferential intermediate patterned section differ by any one of the following parameters of the electrically insulating regions thereof, or any combination thereof: size of insulating region, density of insulating regions, and vertical and / or horizontal distance between adjacent insulating regions. In some embodiments, the circumferential intermediate patterned section starts with the same pattern of insulating regions as the main circumferential patterned section, which gradually and / or step-wise (either smoothly or in steps) morphs into the circumferential non-patterned sections.

[0182] In some embodiments, the main circumferential patterned section and the circumferential intermediate patterned section of the drum have about the same size of insulating regions and a different average density of insulating regions. In some embodiments, the main circumferential patterned section and the circumferential intermediate patterned section have about the same density of insulating regions and a different average size thereof. In some embodiments, the main circumferential patterned section and the circumferential intermediate patterned section have different average size and a different density of electrically insulating regions.

[0183] In some embodiments, the main circumferential patterned section may be defined as exhibiting a first density of insulating regions and the circumferential intermediate patterned section may be defined as exhibiting a second density of insulating regions, wherein the second density is lower than the first density by a specific value, which can be expressed as a percentage of the first density.

[0184] In one example, the drum may be designed to include a circumferential intermediate patterned section that has a width X, wherein the number of electrically insulating regions is reduced along the axial direction of the drum from the main circumferential patterned section towards the non-patterned section such that a certain percent of the insulating regions (Y%) are eliminated every Y% of the circumferential intermediate patterned section (i.e., Y%*X), while maintaining the original distance between the insulating regions (where the insulating regions are not eliminated). Said certain percent (Y%) may be, inter alia, 1%, 5%, 10% or 20%. For example, the number of insulating regions within the circumferential intermediate patterned section may be reduced along the axial direction of the drum such that 10% are eliminated every 10% of the circumferential intermediate patterned section (0.1*X).

[0185] According to some embodiments, the number of insulating regions within said Y%*X regions is eliminated in an irregular manner, e.g., a strip within one such region that is closer to the non-patterned section of the drum may have a higher density of insulating regions than a strip within said region that is closer to the main circumferential patterned section, as long as the overall design of the gradient of the circumferential intermediate patterned section fulfils the above condition.

[0186] According to some embodiments, the number of insulating regions within said 0.1 *X regions is eliminated in a gradual manner, i.e., each strip within one 0.1 *X region that is closer to the non-patterned section of the drum has a lower density of insulating regions than its adjacent strip within said 0.1 *X region that is closer to the main circumferential patterned section.

[0187] According to some embodiments, the number of holes within said 0.1 *X regions is constant, i.e., each strip within one 0.1 *X region that is closer to the non-patterned section of the drum has the same density of holes as its adjacent strip within said 0.1 *X region that is closer to the main circumferential patterned section.

[0188] In some embodiments, the electrically insulating regions are at least 10-100 pm deep, at least 20-100 pm deep, at least 30-100 pm deep, at least 40-100 pm deep, or at least 50-100 pm deep. In some embodiments, the the electrically insulating regions are at least 10 pm deep, or at least 20 pm, 30 pm, 40 pm, 50 pm, 60 pm, 70 pm, 80 pm, 90 pm, or at least 100 pm deep, at least 110 pm deep, or at least 120 pm, 130 pm, 140 pm, 150 pm, 160 pm, 170 pm, 180 pm, 190 pm, or at least 200 pm deep, or at least 210 pm deep, at least 220 pm, 230 pm, 240 pm, 250 pm, 260 pm, 270 pm, 280 pm, 290 pm, or at least 300 pm deep.

[0189] In some embodiments, the method of forming a copper foil includes using forward and reverse current / voltage / power pulses and modifying pulse amplitude, shape, duration, and rate / frequency of pulses by modifying the pulse supply during the electrodeposition process to control the lateral growth of copper and create a structure. In some embodiments, the process includes using direct current during the electrodeposition process. In some embodiments, the shape of the pulses is not symmetrical. In some embodiments, the shape, amplitude or duration of the pulse may change during the electroforming process, to specifically control the lateral growth at any stage of copper deposition.

[0190] In some embodiments, the copper foil is electrodeposited from a copper sulfate electrolyte onto the drum surface. In some embodiments, the conducting an electrical current is performed at at least one of: a temperature in the range of 25°C to 50 °C; and a current density in the range of 5 A / dm2to 80 A / dm2. In some embodiments, the electrolyte comprises copper cations at a concentration in the range of 15 to 110 g / L. In some embodiments, the electrolyte further comprises chloride ion at a concentration in the range of 20-80 mg / L, and / or sulfuric acid at a concentration in the range of 45 to 110 g / L.

[0191] In some embodiments, the electrolyte is a liquid electrolyte. In some embodiments, the electrolyte further comprises at least one additive selected from the list consisting of: brighteners, levelers and wetting agents. In some embodiments, the liquid electrolyte is a solution. In some embodiments, the liquid electrolyte is an aqueous solution.

[0192] Alternatively, the copper foil may be prepared through an electrochemical etching process. In this process, a continuous copper foil is covered by or comes in contact with an electrically insulating mask that has openings arranged in a predefined pattern through which the surface of the copper foil that contacts the mask is etched, when the foil is held at a positive potential versus a counter electrode, while being in ionic contact therewith through a common electrolyte.

[0193] The obtained foil features narrow, non-perf orated sections along each of its longitudinal edges, structural margins that are referred to herein as non-perforated sections. These margins provide additional mechanical stability and facilitate easier handling during the manufacturing process. As provided herein, the perforation of the perforated section of the foil diminishes closer to the non-perforated sections (i.e., intermediate perforated sections), ensuring that the margins will not tear in mid-process. The obtained copper foil is rolled into a roll as described hereinabove.

[0194] Feeding the Copper Foil: The prepared perforated copper foil is then fed into the electrode manufacturing process. Preparation of Active Material Slurry: Active materials (such as lithium nickel cobalt manganese oxide or lithium iron phosphate for the cathode or graphite for the anode), conductive additives, and polymer binders are mixed with solvents to form a slurry.

[0195] Coating: The prepared slurry is then coated onto both sides of the the perforated copper foil in a continuous automated process. The coating process ensures that the active material is uniformly distributed on the surfaces of the copper foil.

[0196] Electrode coating is a significant part of battery manufacturing process, with a large contribution to the final micro structure and thus pertinent to the functioning of the resulting electrode. According to embodiments of the present invention, coating of the copper foil provided herein can be performed via various routes, whereas the coating device may be a draw down coater, which is commonly used in research labs to produce small coatings, or for larger, industrial applications, a roll-to-roll (a.k.a., R2R or reel-to- reel) coater, which the presently disclosed copper foil is designed and most suitable for. In a roll-to-roll setup, the geometry of the coater, used to coat the copper foil according to some embodiments of the present invention, can be doctor blade (a fine blade set at a fixed gap from the CC), comma bar (a comma shaped geometry with a curved leading edge), slot die (coating material is extruded out of a slot onto the CC), “knife-over-roll” (coating material is dispensed to the CC, which then passes through a knife and roller), “reverse comma bar”, “Meyer rod” (wherein a roller applies the coating material to the CC, and then a Meyer bar meters out the correct amount), as these methods and devices are known in the art. The coating may be applied while the CC is supported by a roller, or it can also be applied to an unsupported CC under tension, which is known as tensioned web coating. Other electrode coating processes known in the art may be used to coat a current collector, set forth herein.

[0197] The coating materials are introduced directly onto the CCs without additional morphological deformation of the CCs, and can be introduced on one side of the copper foil, or on both sides thereof, depending on the coating equipment.

[0198] Thus, according to some embodiments of the present invention, the electrode is produced by any known R2R process, using a roll of the copper foil provided herein.

[0199] Since the copper foil provided herein is designed to be suitable for contemporary industrial electrode production, all known and commonly used processes, methodologies and techniques for producing and applying active coating materials onto current collectors, apply and are useful for use therewith.

[0200] In some embodiments, the processes include coating a current collector with wet or fluid active material composition, in the form of a slurry, a paste, a liquid and the likes. In some embodiments, the coating is afforded by dry (solventless) coating in which the active material is deposited onto a current collector with little or no use of a solvent to carry the active material.

[0201] Drying: After coating, the electrode is dried to remove the solvent, which results in a porous electrode coating. From the coater, the coated foil is fed directly into a long drying oven to bake the electrode material onto the foil.

[0202] Compaction (calendering) step: The electrode (i.e., the current collector foil coated with the porous electrode coating on both sides, gets pulled into a gap two roll presses or calenders working in opposite directions. The gap size is set significantly smaller than the electrode thickness or the rolling force is adjusted ensuring the desired compaction of the electrode coating.

[0203] Re-reeling and Cutting: Following calendaring, the coated foil is re-reeled. The coated foils are subsequently fed into slitting machines to cut the foil into narrower strips suitable for different sizes of electrodes. At this stage, the coated perforated section may be separated from the non-perforated section(s) and / or the intermediate perforated section(s), leaving a coated and uniformly perforated copper foil corresponding to the perforated section of the foil provided herein. This step may be carried out by cutting the copper foil such that most of the perforated section is afforded such that only the uniformly perforated part of the foil enters the nest step(s) of electrode manufacturing. In some embodiments, the coated foil is cut such that the intermediate perforated section or the intermediate perforated section along with the non-perforated section are part of the final electrode structure.

[0204] In some embodiments the coated perforated section is not separated from the intermediate perforated section(s).

[0205] In some embodiments the coated perforated section is not separated from the intermediate perforated section(s) and the non-perforated section(s). Assembly: Depending on the specific design of the battery (cylindrical, prismatic, or pouch), the electrodes (i.e., the coated current collectors) are either stacked or wound together with a separator in between to prevent short-circuiting.

[0206] Finishing: Finally, the assembled cell undergoes a finishing process that includes sealing, electrolyte filling, formation (first slow charge / discharge cycles), and aging.

[0207] Hence, according to an aspect of some embodiments of the present invention, there is provided a method of forming an electrode, which is effected by: i) providing the copper foil as disclosed herein; ii) applying an electrode active material slurry on the copper foil or at least on the perforated section of the copper foil provided herein, thereby forming the electrode; and iii) optionally separating the perforated section from the non-perforated section(s) and the intermediate perforated section(s), thereby obtaining a coated and uniformly perforated copper foil corresponding to the perforated section of the foil provided herein, thereby forming the electrode.

[0208] In some embodiments, the method includes separating the perforated section from the non-perforated section(s) and the intermediate perforated section(s).

[0209] In some embodiments, the method further includes applying the electrode material slurry to the intermediate perforated section of the copper foil. In some embodiments, the method does not involve separating the perforated section from the intermediate perforated section(s). In certain embodiments, the method does not involve separating the perforated section from the non-perforated section(s).

[0210] Electrode:

[0211] According to some embodiments of the present invention, there is provided an electrode, e.g., in the context of a battery or a capacitor, that includes at least one current collector, and an active electrode material (a.k.a., coating material) disposed on the current collector, wherein the current collector includes at least one, or consists of the perforated section of the copper foil provided herein. Herein throughout, the term “electrode” refers to both anodes and cathode, unless stated otherwise explicitly.

[0212] According to some embodiments of the present invention, there is provided an electrode, e.g., in the context of a battery or a capacitor, that includes at least one current collector, and an active electrode material (a.k.a., coating material) disposed on the current collector, wherein the current collector includes at least the perforated section and the intermediate perforated section of the copper foil provided herein. The current collector may further include at least a portion of the non-perforated section. A battery tab may be attached to said portion of the non-perforated section.

[0213] Batteries and electric devices:

[0214] In view of the forgoing, there is provided a cell or a battery, that includes at least one electrode, wherein the electrode comprises at least a perforated section of the copper foil provided herein, or wherein the electrode comprises a current collector that includes at least one, or consists of the perforated section of the copper foil provided herein. In some embodiments, the electrode further includes the intermediate perforated section of the copper foil. In some embodiments, the electrode further includes at least a portion of the non-perforated section of the copper foil.

[0215] It is noted herein that while a cell is a single unit of device that converts chemical energy into electrical energy, and a battery is a collection of cells that converts chemical energy into electrical energy, the terms “cell” and “battery” are used herein interchangeably. Correspondingly, there is provided an electric device that includes the cell, an array of cells, the battery or an array of batteries (i.e., battery packs or battery modules), as provided herein. In some embodiments, the cell or the battery includes at least one electrode that includes at least one current collector, wherein the CC comprises or consists of the perforated section of the copper foil as described herein.

[0216] The electric devices which are contemplated within the scope of the present invention, include any electric device that can use a cell or a battery as a main, auxiliary or minor source of energy. Alternatively, an electric device is one that includes at least one battery, wherein the device uses the electricity stored in the battery as its power source.

[0217] Examples of electric devices include, without limitation, an electric vehicle for transportation in air, land, water and / or space, a smartphone, a laptop computer, a portable media player, a power tool, a toy, a heating device, a colling device, an article for illumination (e.g., flashlight), and the likes.

[0218] In some embodiments, the electric device is a device that requires batteries with high power density, such as a vehicle (e.g., electric car). In the context of a battery, power density refers to the amount of power that can be stored or delivered by the battery per unit volume or unit mass. High power density means that a battery has the ability to store or deliver a relatively large amount of power in a relatively small space or weight. This is one of the characteristics for batteries using the perforated section of the copper foil provided herein, which is designed for use in portable electronic devices and electric vehicles, where size and weight are critical factors. High power density batteries can also have a higher energy density, which means they can store more energy per unit weight or volume.

[0219] General Definitions:

[0220] As used herein the term “about” refers to ±10%. For example, the term “about 100 pm” encompasses the value 100 pm, as well as the values 90 pm, 91 pm, 92 pm, 93 pm, 94 pm, 95 pm, 96 pm, 97 pm, 98 pm, 98 pm, 99 pm, 100 pm, 101 pm, 102 pm, 103 pm, 104 pm, 105 pm, 106 pm, 107 pm, 108 pm, 109 pm, and 110 pm.

[0221] The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

[0222] The term “consisting of’ means “including and limited to”.

[0223] The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0224] As used herein, the phrase “selected from the group consisting of’ includes all members of the recited group, each member of the recited group, and all possible combinations. For example, selected from the group consisting of A, B, and C, includes A, only, as well as B, only, as well as C, only, as well as A and B, as well as A and C, as well as B and C, and as well as A, B, and C.

[0225] As used herein, the phrases "substantially devoid of" and / or "essentially devoid of" in the context of a certain substance, refer to a composition that is totally devoid of this substance or includes less than about 5, 1, 0.5 or 0.1 percent of the substance by total weight or volume of the composition. Alternatively, the phrases "substantially devoid of" and / or "essentially devoid of" in the context of a process, a method, a property or a characteristic, refer to a process, a composition, a structure or an article that is totally devoid of a certain process / method step, or a certain property or a certain characteristic, or a process / method wherein the certain process / method step is effected at less than about 5, 1, 0.5 or 0.1 percent compared to a given standard process / method, or property or a characteristic characterized by less than about 5, 1, 0.5 or 0.1 percent of the property or characteristic, compared to a given standard.

[0226] When applied to an original property, or a desired property, or an afforded property of an object or a composition, the term “substantially maintaining”, as used herein, means that the property has not change by more than 20%, 10% or more than 5% in the processed object or composition.

[0227] The term “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0228] The words “optionally” or “alternatively” are used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features unless such features conflict.

[0229] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0230] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0231] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging / ranges between” a first indicate number and a second indicate number and “ranging / ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0232] As used herein the terms “process” and "method" refer to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, material, mechanical, computational and digital arts.

[0233] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0234] EXAMPLES

[0235] Reference is now made to the following examples, which together with the above descriptions, illustrate some embodiments of the invention in a non-limiting fashion.

[0236] Example 1

[0237] Measurement of fracture strength at a solid-porous interface

[0238] This experiment was designed to measure fracture strength at an interface between a perforated section and a solid section of a copper foil by a 90° pull test using FINAT 2 Assisted Pull-Peel Table along with Omni Test 5.0 Universal Testing Machine from Mecmesin. The procedure included the following steps:

[0239] • Preparing a rectangular specimen from a metallic perforated foil to be tested;

[0240] • Fastening the non-perf orated section of the specimen to a glass slide. The perforated section is left unbound to ensure free movement;

[0241] • Attaching a single- sided clear tape to the perforated section of the specimen (or the intermediate perforation section) adjacent to the non-perforated section. The tape should be positioned near the interface without overlapping with the non- perforated section. The tape should be sufficiently long to adhere to the specimen and extend to a clamp for the peel test;

[0242] • Mounting a peel test stage onto the testing machine, ensuring the taped area is directly under the clamp and clamping the end of the tape in the grip;

[0243] 5 • Adjusting the stage position to get a 90° angle between the tape and the sample; and

[0244] • Initiating the test using the software.

[0245] The same test was performed within the perforated section of the foil to normalize the data for bulk fracture strength. 0

[0246] Example 2

[0247] Effect of the intermediate perforated section on fracture strength

[0248] Three elongated perforated copper foils (Sample A, Sample B, and Sample C) were manufactured by electrodeposition, each having non-perforated sections (solid 5 margins) along both longitudinal edges of the foil. The perforated sections of the three foils had a seamless repeating pattern of holes with hexagonal packing, wherein holes within each pattern had an essentially similar diameter and essentially similar horizonal and vertical distance therebetween. Sample A did not have an intermediate perforated section, while Samples B and C were characterized by a gradient of decreasing 0 perforation between the central perforated section and the non-perforated section of the foil by gradually eliminating a certain percentage of the holes as present in the central perforated section towards the non-perforated sections.

[0249] Fracture strength at the solid-porous interface between the three foils was tested as described in Example 1. Table 1 shows the test results as well as the structural 5 properties of the tested foils.

[0250] Table 1: Structural and mechanical properties of the tested copper foils

[0251] It can be seen that the addition of the intermediate perforated section significantly improved interface fracture strength of the foils (Samples B and C as compared to Sample A). Additionally, it was observed that this positive effect was more pronounced in Sample 5 B than in Sample C, which may possibly be attributed, for example, to a larger difference between the average void area of the central (i.e., main) perforated section and the intermediate perforated section of Sample B, as compared to Sample C.

[0252] It is expected that during the life of a patent maturing from this application many 0 relevant copper foils specifically perforated for electrode manufacturing will be developed and the scope of the phrase "gradually perforated copper foil" is intended to include all such new technologies a priori.

[0253] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination 5 in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub -combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is 0 inoperative without those elements.

[0254] The instant disclosure provides a copper foil design with distinctive sections for specific applications, offering enhanced performance and versatility in the field of electronic storage devices. The copper foil includes a non-perf orated section, a perforated 5 section, and an intermediate perforated section positioned between them in a longitudinal direction.

[0255] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0256] It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

WHAT IS CLAIMED IS:

1. A copper foil comprising: at least one non-perforated section extending in a longitudinal direction of the foil; at least one perforated section extending along said longitudinal direction and laterally offset from the at least one non-perforated section, and at least one intermediate perforated section positioned and extending longitudinally between said perforated section and said non-perforated section, wherein an average void area of said perforated section is at least about 1% greater than an average void area of said intermediate perforated section.

2. The copper foil of claim 1, wherein the intermediate perforated section has a uniform width throughout the length of the foil.

3. The copper foil of claims 1 or 2, wherein said average void area of said perforated section ranges from about 5% to about 98% of the total area of said perforated section.

4. The copper foil of any one of the preceding claims, wherein the average void area of said intermediate perforated section ranges from about 0.1% to about 97% of the total area of said intermediate perforated section.

5. The copper foil of any one of the preceding claims, wherein a width of said at least one non-perforated section ranges from about 0.1% to about 30% of the width of the copper foil.

6. The copper foil of any one of the preceding claims, wherein a width of said perforated section ranges from about 70% to about 99% of the width of the copper foil.

7. The copper foil of any one of the preceding claims, wherein a width of said intermediate perforated section ranges from about 1% to about 30% of the width of the copper foil.

8. The copper foil of any one of the preceding claims, wherein a width of said intermediate perforated section ranges from about 5% to about 100% of a width of the non-perf orated section.

9. The copper foil of any one of the preceding claims, wherein the width of said intermediate perforated section ranges from 1-10 mm, and the width of the non-perf orated portion ranges from 10-50 mm.

10. The copper foil of claim 9, wherein the width of said intermediate perforated section is about 5 mm, and the width of the non-perforated portion is about 20 mm.

11. The copper foil of any one of the preceding claims, wherein each of said perforated section and said intermediate perforated section individually comprise a pattern of holes.

12. The copper foil of claim 11, wherein said pattern of holes of said perforated section is a seamless repeating pattern.

13. The copper foil of claim 12, wherein said seamless repeating pattern is characterized by an average hole size ranging 10-2000 pm and / or a hole density ranging 4-400 holes / mm2.

14. The copper foil of claim 13, wherein said intermediate perforated section is characterized by holes having an average hole size ranging 10-1800 pm and / or a hole density ranging 4-300 holes / mm2.

15. The copper foil of claims 12 or 13, wherein at least one of the perforated section and the intermediate perforated section is characterized by holes having an average hole size ranging 50-150 pm.

16. The copper foil of claim 11, wherein said perforated section is characterized by essentially the same average hole size and a larger hole density compared to said intermediate perforated section.

17. The copper foil of claim 11, wherein said perforated section is characterized by essentially the same average hole size and a smaller vertical and / or horizontal distance between at least a portion of adjacent holes compared to said intermediate perforated section.

18. The copper foil of claim 11, wherein said perforated section is characterized by essentially the same hole density and a larger average hole size compared to said intermediate perforated section.

19. The copper foil of claim 11, wherein said perforated section is characterized by essentially the same vertical and / or horizontal distance between adjacent holes and a larger average hole size compared to said intermediate perforated section.

20. The copper foil of claim 11, wherein said perforated section is characterized by a larger hole density and a larger average hole size compared to said intermediate perforated section.

21. The copper foil of claim 11, wherein said perforated section is characterized by a larger hole density and a smaller vertical and / or horizontal distance between adjacent holes compared to said intermediate perforated section.

22. The copper foil of claim 11, wherein said perforated section is characterized by holes having a different shape and / or a different relative orientation compared to said intermediate perforated section.

23. The copper foil of any one of the preceding claims, wherein said average void area of said perforated section is about 1-90% greater than said average void area of said intermediate perforated section.

24. The copper foil of any one of the preceding claims, wherein said intermediate perforated section is characterized by a gradient of decreasing perforation.

25. The copper foil of claim 24, wherein said gradient of decreasing perforation is one of: a smooth and linear gradient; a smooth and non-linear gradient; a linear step-wise gradient; or a non-linear step-wise gradient.

26. The copper foil of claim 11, wherein said pattern of holes of said intermediate perforated section differs from said pattern of holes of said perforated section in that a certain percentage of the holes present in said perforated section is eliminated in said intermediate perforated section.

27. The copper foil of claim 26, wherein said holes are eliminated in a gradual manner towards the non-perforated section.

28. The copper foil of claim 26, wherein said holes are eliminated in an irregular manner towards the non-perforated section.

29. The copper foil of any one of claims 26 to 28, wherein the holes are eliminated in a step-wise manner, wherein a percentage of the width of a step out of the total width of the intermediate perforated section is similar to said certain percentage of holes that are eliminated in the step.

30. The copper foil of any one of the preceding claims, formed by electrodepo sition .

31. The copper foil of any one of the preceding claims, having a thickness ranging about 1-50 pm.

32. The copper foil of claim 31, having a thickness ranging about 5-15 pm.

33. The copper foil of claims 31 or 32, wherein said perforated section and said intermediate perforated section have a tensile strength in the range of 150-250 MPa, and the solid section has a tensile strength in the range of 300-400 MPa.

34. The copper foil of any one of the preceding claims, wherein less than 1% of the perforations in said perforated section and said intermediate perforated section are non-through-holes .

35. The copper foil of claim 34, wherein the perforations in said perforated section and said intermediate perforated section are through-holes.

36. The copper foil of any one of the preceding claims, wherein the foil is corrugated.

37. The copper foil of any one of the preceding claims, wherein the copper foil or said perforated section thereof being for use as a current collector of an electrode.

38. An electrode comprising the copper foil of any one of the preceding claims, or at least said perforated section of the copper foil.

39. The electrode of claim 38 comprising a battery tab connected to the nonperforated section of the copper foil.

40. A method of forming an electrode, comprising: providing the copper foil of any one of claims 1-37; applying an electrode active material slurry on at least the perforated section of the copper foil, thereby forming the electrode; andoptionally separating the perforated section from the non-perforated section and the intermediate perforated section.

41. A method of forming an electrode, comprising: providing the copper foil of any one of claims 1-37; applying an electrode active material slurry on at least the perforated section and the at least one intermediate perforated section of the copper foil, thereby forming the electrode; and optionally separating the perforated section and the intermediate perforated section from the non-perforated section.

42. A method of forming a copper foil comprising: exposing at least a portion of a drum having a patterned lateral surface to an electrolyte comprising copper ions, connecting the drum to a negative pole of a power source, wherein an anode that faces said portion of the drum and is exposed to said electrolyte is connected to a positive pole of the power source, rotating the drum and continuously separating the copper foil that is electrically deposited thereon from the drum, wherein the patterned lateral surface comprises at least one circumferential nonpatterned section, at least one circumferential patterned section comprising electrically insulating regions, and at least one circumferential intermediate patterned section comprising electrically insulating regions, said intermediate patterned section positioned and extending longitudinally between said patterned section and said non-patterned section, wherein the electrically insulating regions of the patterned section occupy an area that is at least about 1% greater than an area occupied by the electrically insulating regions of the intermediate patterned section.

43. The method of claim 42, wherein the copper foil comprises at least one non-perforated section extending in a longitudinal direction of the foil; at least one perforated section extending in said longitudinal direction and laterally offset from the at least one non-perforated section, andat least one intermediate perforated section positioned and extending longitudinally between said perforated section and said non-perforated section, wherein an average void area of said perforated section is at least about 1 % greater than an average void area of said intermediate perforated section.

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