Current collector for electrodes

Abstract

A current collector for electrodes, according to the present invention, comprises: a base film; a conductive material provided on the upper surface and / or the lower surface of the base film; and a lead tab provided on one of the upper surface or the lower surface of the base film so as to be electrically connected to the conductive material, wherein, at a part adjacent to the edge of the lead tab, a metal-free part in which the surface of the base film is exposed or the conductive material is absent is formed, and the metal-free part can be formed to extend across both ends of the base film in the width direction along the edge of the lead tab, or can be formed such that both ends of the metal-free part in the longitudinal direction are positioned at one of two ends of the base film in the width direction.

Description

Current collector for electrodes

[0001] The present invention relates to a current collector for an electrode, and more specifically, to a current collector for an electrode that can prevent overheating of the battery and increase the safety of the battery by removing a portion of the conductive material around the lead tab among the metal conductive materials provided on the base film, thereby allowing current to flow only in a portion of the conductive material and not in the remaining portion when an external short circuit occurs, thereby performing an electrochemical fuse or physical fuse function such as blocking the short-circuit current path.

[0002] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing, and among such secondary batteries, lithium secondary batteries, which exhibit high energy density and operating potential and a low self-discharge rate, have been commercialized.

[0003] Lithium metal rechargeable batteries were the first commercially available rechargeable batteries to utilize lithium metal as the anode. However, production of lithium metal rechargeable batteries was discontinued within just a few years of commercialization due to issues such as cell volume expansion caused by lithium dendrites forming on the surface of the lithium metal anode, a gradual decrease in capacity and energy density, short circuits resulting from continuous dendrite growth, reduced cycle life, and cell stability problems (explosion and ignition). Consequently, carbon-based anodes were adopted instead of lithium metal because they are more stable and capable of stably storing lithium in an ionic state within lattices or empty spaces. The use of these carbon-based anodes led to the full-scale commercialization and widespread adoption of lithium rechargeable batteries.

[0004] To date, carbon-based or non-carbon-based anode materials have been the mainstream for lithium-ion batteries, and most anode material development has been concentrated on carbon-based (graphite, hard carbon, soft carbon, etc.) and non-carbon-based (silicon, tin, titanium oxide, etc.) materials.

[0005] Meanwhile, as portable electronic devices and information and communication devices have recently become smaller, the use of lithium-ion batteries as ultra-small power systems to power them is highly anticipated.

[0006] Furthermore, the development and research of polymer-based electronic devices and components utilizing advantages such as flexibility, low cost, and ease of fabrication have been actively underway recently. Therefore, to use them in miniaturized devices, it is necessary to reduce the thickness or weight of lithium-ion batteries while maintaining their energy density or performance.

[0007] In addition, even if the thickness or weight of the lithium secondary battery is reduced, it must be possible to enhance the safety of the lithium secondary battery by blocking or destroying the path of the short-circuit current in the event of an external short circuit.

[0008] In particular, for large-capacity lithium secondary batteries capable of storing more than 2Ah of energy, there is an even greater need for battery safety technology that can reduce or cut off the short-circuit current in the event of an external short circuit.

[0009] The applicant has proposed the present invention to solve the above-mentioned problems.

[0010] Related prior art is Korean Patent Publication No. 10-2018-0037898 (Title of invention: Negative electrode for lithium metal secondary battery and lithium metal secondary battery including the same, Date of publication: April 13, 2018).

[0011] The present invention is proposed to solve the above-mentioned problems and provides an electrode current collector that can reduce thickness or weight compared to a metal foil current collector, while simultaneously preventing temperature rise and increasing battery stability by functioning like a fuse in the event of an external short circuit.

[0012] In addition, the present invention provides an electrode current collector that can ensure the safety of a secondary battery including an electrode current collector by blocking the path through which the short-circuit current flows when an external short circuit occurs in a large lithium secondary battery, thereby preventing the entire electrode current collector from reacting to an external short circuit.

[0013] The problems that the present invention aims to solve are not limited to the problem(s) mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0014] A current collector for an electrode according to the present invention for achieving the above-mentioned objectives comprises: a base film; a conductive material provided on at least one surface of the upper or lower surface of the base film; and a lead tab provided on one surface of the upper or lower surface of the base film to be electrically connected to the conductive material; wherein a non-metallic portion is formed in a portion adjacent to the edge of the lead tab, in which the surface of the base film is exposed or the conductive material is not present, and the non-metallic portion may be formed to cross both ends of the base film in the width direction along the edge of the lead tab, or may be formed such that both ends of the non-metallic portion in the length direction are located at one end of the base film in the width direction.

[0015] The above-mentioned metalless portions may be formed on each side in the width direction of the lead tab along the length direction of the lead tab.

[0016] At least a portion of the above-mentioned metalless part may have the conductive material present or a metal part formed where the base film is not exposed.

[0017] The above-mentioned metal part may be formed in a portion close to one end located between the two ends in the width direction of the base film among the two ends in the length direction of the lead tab.

[0018] The metal parts formed on the metalless parts located at both ends in the width direction of the lead tab can be formed symmetrically with respect to the centerline in the length direction of the lead tab.

[0019] The above metalless portion may be formed on one side in the length direction and one side in the width direction of the lead tab.

[0020] At least a portion of the above-mentioned metalless part may have the conductive material present or a metal part formed where the base film is not exposed.

[0021] The above-mentioned metal part may be formed in a portion close to one end located between the two ends in the width direction of the base film among the two ends in the length direction of the lead tab.

[0022] The above-mentioned metal part may be formed to interrupt the above-mentioned metal part, which is continuously formed along the periphery of the lead tab, at a single point.

[0023] The length of the above-mentioned metal part can be formed to be shorter than the width-direction length of the above-mentioned lead tab.

[0024] The above-mentioned metal part can block the flow of short-circuit current when an external short circuit occurs.

[0025] Specific details of other embodiments are included in the detailed description and attached drawings.

[0026] The electrode current collector according to the present invention uses a base film made of an insulator instead of a metal foil, and since a conductive material is coated or a plating layer is formed on the surface of the base film, the thickness can be reduced compared to a current collector made of a metal foil.

[0027] The electrode current collector according to the present invention can reduce the portion of the electrode current collector involved in an external short circuit by blocking the path through which the short-circuit current flows when an external short circuit occurs, and can prevent overheating of the battery and increase the safety of the battery by performing the function of an electrochemical fuse or a physical fuse through the blocking of the short-circuit current path.

[0028] FIG. 1 is a perspective view illustrating an electrode assembly including a current collector for an electrode according to the present invention.

[0029] FIG. 2 is an exploded perspective view illustrating an electrode assembly according to the present invention.

[0030] FIGS. 3 and FIGS. 4 are plan views illustrating a current collector for an electrode according to a first embodiment of the present invention.

[0031] FIGS. 5a to 5d are plan and cross-sectional views illustrating the portion of the electrode current collector according to FIG. 4 where the lead tab is located.

[0032] FIGS. 6a, FIGS. 6b, and FIGS. 7 are plan views illustrating a current collector for an electrode according to a second embodiment of the present invention.

[0033] FIGS. 8a to 8d are plan and cross-sectional views illustrating the portion of the electrode current collector according to FIG. 7 where the lead tab is located.

[0034] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Identical or similar components are assigned identical or similar reference numerals, and redundant descriptions thereof will be omitted. The suffix "bu" used for components in the following description is assigned or used interchangeably solely for the ease of drafting the specification and does not inherently possess a distinct meaning or role. Furthermore, in describing embodiments disclosed in this specification, if it is determined that a detailed description of related prior art could obscure the essence of the embodiments disclosed in this specification, such detailed description will be omitted. Additionally, the attached drawings are intended only to facilitate understanding of the embodiments disclosed in this specification; the technical concept disclosed in this specification is not limited by the attached drawings, and it should be understood that they include all modifications, equivalents, and substitutions that fall within the spirit and technical scope of the present invention.

[0035] Terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0036] When it is stated that a component is "connected" to another component, it should be understood that it may be directly connected to that other component, or that there may be other components in between.

[0037] A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0038] In this application, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0039] It should be noted that the drawings are schematic and not drawn to scale. The relative dimensions and proportions of parts in the drawings are exaggerated or reduced in size for clarity and convenience, and any dimensions are illustrative only and not limiting. Additionally, the same reference numerals are used to denote similar features for the same structure, element, or part appearing in two or more drawings.

[0040] The embodiments of the present invention specifically illustrate ideal embodiments of the present invention. As a result, various variations of the drawings are expected. Accordingly, the embodiments are not limited to the specific form of the illustrated area and include, for example, variations in form resulting from manufacturing.

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0042] FIG. 1 is a perspective view illustrating an electrode assembly including a current collector for an electrode according to the present invention; FIG. 2 is an exploded perspective view illustrating an electrode assembly according to the present invention; FIG. 3 and FIG. 4 are plan views illustrating a current collector for an electrode according to a first embodiment of the present invention; FIG. 5a to 5d are plan and cross-sectional views illustrating a portion of the current collector for an electrode according to FIG. 4 where a lead tab is located; FIG. 6a, FIG. 6b and FIG. 7 are plan views illustrating a current collector for an electrode according to a second embodiment of the present invention; FIG. 8a to 8d are plan and cross-sectional views illustrating a portion of the current collector for an electrode according to FIG. 7 where a lead tab is located.

[0043] FIGS. 1 and 2 illustrate an electrode assembly (10) including an electrode current collector (100) according to the present invention. In FIGS. 1 and 2, the electrode current collector (100) according to the present invention is a positive electrode current collector. In order to be used in the electrode assembly (10), an active material (103) must be coated on the surface of the electrode current collector (100).

[0044] Meanwhile, the current collector (200) for the negative electrode has a negative active material (203) coated on a negative metal foil (201), and a negative lead tab (290) can be connected to one end in the longitudinal direction.

[0045] A separator (300) may be placed between a current collector (200) for a negative electrode and a current collector (100) for an electrode (positive electrode) according to the present invention. If the current collector (200) for a negative electrode and the current collector (100) for a positive electrode are stacked in order above and below, respectively, with the separator (300) in between, as shown in FIG. 2, an electrode assembly (10) as shown in FIG. 1 is formed.

[0046] For convenience of explanation, the current collector (100) for the positive electrode is referred to as the current collector for the electrode below.

[0047] FIGS. 3 and 4 illustrate an electrode current collector (100) according to a first embodiment of the present invention. Unlike the negative electrode current collector (200) mentioned above, the electrode current collector (100) does not use a metal foil.

[0048] A current collector for electrodes (100) according to the first embodiment of the present invention has a resistance value greater than that of a current collector made of metal foil, so the limit current value of the current flowing through the current collector can be adjusted, and since the current flow can be obstructed by damage to the base film, the short-circuit current can be reduced or heat generation can be prevented when an internal or external short circuit occurs in a secondary battery.

[0049] A lithium secondary battery equipped with an electrode current collector (100) according to the present invention may have the characteristics or concept of a Max Current Limited Battery (MCLB). Below, an electrode current collector according to the present invention that enables the implementation of an MCLB will be described.

[0050] The electrode current collector (100) according to the present invention is a positive current collector, and because it has a higher resistance value than the positive current collector of a conventional battery, that is, a positive current collector formed of a metal foil, it can not only adjust the limit current but also reduce the short-circuit current or reduce the heat generation phenomenon that occurs during a short circuit by blocking or collapsing the current path in the event of an internal or external short circuit, thereby increasing the safety of the battery.

[0051] The electrode current collector (100) according to the first embodiment of the present invention is characterized by using a base film (101) as the base material without using a metal foil, and applying or coating a thin layer of metal on the base film (101).

[0052] Referring to FIG. 3 and FIG. 4, a current collector (100, current collector) for an electrode according to a first embodiment of the present invention may include a base film (101, polymer film); and a conductive material (102, conductive material) provided on at least one surface of the upper or lower surface of the base film (101).

[0053] Here, the conductive material (102) can function as an electrochemical fuse and thus can have a short-circuit prevention function. The electrochemical characteristics of this conductive material (102) will be described later.

[0054] The base film (101) can be provided in the shape of a long strip as shown in FIG. 3. Here, the base film (101) is preferably provided with an insulating material such as polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or polyethylene terephthalate (PET).

[0055] The base film (101) has a thickness of 50 μm or less, but it is preferable to have a thickness of 1.4 μm or more and 50 μm or less. The electrode current collector (100) according to the first embodiment of the present invention can reduce the thickness or weight of the battery compared to when a conventional metal foil current collector is used. By using an insulating base film (101) with a thickness of 1.4 μm or more and 50 μm or less as the basic configuration of the current collector (100), the overall thickness or weight of the lithium secondary battery equipped with the electrode current collector (100) according to the first embodiment of the present invention can be reduced.

[0056] When the electrode current collector (100) is a positive electrode current collector, the conductive material (102) may be made of aluminum (Al) metal. The conductive material (102) may also be a conductive layer forming the outermost surface of the electrode current collector (100).

[0057] The conductive material (102) may be formed to control or lower the limit current or maximum current of the electrode current collector (100). In other words, the conductive material (102) is an aluminum metal that is plated or coated on the surface of the base film (101) to control the conductivity of the electrode current collector (100), and if the focus is on the state of being deposited or coated (applied) on the surface of the base film (101), the conductive material (102) may be referred to as a conductive layer. It should be noted below that the conductive material (102) is a concept that includes a conductive layer.

[0058] By controlling the amount or thickness of the coating of the conductive material (102) that is plated (coated) or deposited on the surface of the base film (101), the maximum amount of current flowing through the electrode current collector (100) can be controlled or lowered, thereby increasing the safety of the lithium secondary battery including the electrode current collector (100) and ensuring the safety of the battery in the event of a short circuit.

[0059] In other words, the limit current or maximum current flowing through the electrode current collector (100) can be controlled by the thickness or amount of the conductive material (102) formed on the surface of the base film (101). In this way, the nature or concept of a Max Current Limited Battery (MCLB) of a lithium secondary battery can be realized by the conductive material (102) of the electrode current collector (100) according to the first embodiment of the present invention.

[0060] In addition, the safety of the battery can be improved because the base film (101) can melt when a physical internal or external short circuit occurs, thereby preventing the generation of a sudden current.

[0061] The conductive material (102) can be formed on the surface of the base film (101) by various methods. For example, aluminum metal, which is the conductive material (102), can be formed on the surface of the base film (101) by sputtering or evaporation coating. Since aluminum oxidizes easily, it is not easy to form the conductive material (102) on the surface of the base film (101) by electroplating.

[0062] Since the conductivity of the electrode current collector (100) can be controlled or the safety of the battery can be ensured by the amount (weight) or thickness of the conductive material (102) coated, it is necessary to use a method that can control or adjust the thickness or weight of the conductive material (102) when plating or coating.

[0063] The conductive material (102) may be formed on only one side of the base film (101) or on both sides. In this case, it is preferable that the conductive material (102) be formed with a thickness of 0.3 μm based on the minimum cross-section and 2.5 μm based on the maximum cross-section.

[0064] Since the electrode current collector (100) according to the first embodiment of the present invention enables current flow through the conductive material (102), the conductive material (102) must be well maintained coated on the surface of the base film (101). To this end, it is desirable to increase the bonding strength between the conductive material (102) and the base film (101) by surface treatment of the base film (101).

[0065] If the bonding strength between the conductive material (102) and the base film (101) is poor, the conductive material (102) may separate or detach from the surface of the base film (101) when the electrolyte is injected, so it is important to increase the bonding strength between the conductive material (102) and the base film (101).

[0066] A surface treatment may be formed on the surface of the base film (101) to increase the adhesion or bonding strength with the conductive material (102).

[0067] To increase the bonding strength between the conductive material (102) and the base film (101), it is desirable to perform corona treatment on the surface of the base film (101).

[0068] Meanwhile, the electrode current collector (100) according to the first embodiment of the present invention is a current collector used as a positive electrode of a secondary battery, and unlike a conventional metal foil current collector, it can increase the safety of the secondary battery. This is because the conductive material (102) applied or coated on the base film (101) functions to cut off short-circuit current, just like a fuse.

[0069] Generally, when an internal or external short circuit occurs in a secondary battery, a heat generation phenomenon occurs in which the temperature of the secondary battery rises due to the short-circuit current, and there is also a risk that the battery may explode due to the heat. On the other hand, in the case of a secondary battery using an electrode current collector (100) according to the first embodiment of the present invention as the positive electrode, even if an internal or external short circuit occurs, the safety of the battery can be ensured by preventing the temperature of the secondary battery from rising and blocking the short-circuit current.

[0070] A conductive material (102) applied or coated on a base film (101) functions as a current path, and when a short circuit occurs, the conductive material (102) reacts with the electrolyte and breaks into small pieces as if corroded, so the current path is blocked and the short-circuit current no longer flows.

[0071] As illustrated in FIGS. 3 and 4, the electrode current collector (100) according to the first embodiment of the present invention may have a conductive material (102) formed by dividing it into two or more parts along the width direction of the base film (101). Here, the width direction of the base film (101) refers to the direction with a relatively shorter length among the horizontal direction and the vertical direction.

[0072] The electrode current collector (100) illustrated in FIGS. 3 and 4 has an active material (103) formed on the surface of a conductive material (102) provided on the surface of a base film (101). However, the portion where the lead tab (190) is connected is in a blank state without the active material (103). That is, the conductive material (102) can be electrically connected to the lead tab (190) in a state where there is no active material (103) in the portion where the lead tab (190) is connected.

[0073] Referring to FIGS. 3 and 4, a plurality of grooves (103a) may be formed at regular intervals along the length direction of the base film (101) across the entire conductive material (102) and active material (103). FIGS. 3 and 4 illustrate a case where a plurality of grooves (103a) are formed at intervals along the length direction of the base film (101), but a plurality of grooves (103a) may also be formed at intervals along the width direction of the base film (101).

[0074] Since the conductive material (102) and the active material (103) are both absent or removed from the groove (103a), the base film (101) can be provided in an exposed state in the groove (103a).

[0075] The groove portion (103a) can be formed symmetrically on the upper and lower surfaces of the base film (101).

[0076] As shown in FIG. 3, a lead tab (190) is attached to the unoccupied portion (180) of a base film (101) that is long along the longitudinal direction, i.e., the portion without active material (103), and the base film (101) is cut in the width direction to obtain an electrode current collector (100) as shown in FIG. 4.

[0077] Referring to FIG. 4, the groove (103a) formed in the active material (103) and the conductive material (102) can be formed by coating (applying) or depositing the conductive material (102) and the active material (103) over the entire upper or lower surface of the base film (101), and then simultaneously cutting the conductive material (102) and the active material (103) using a laser or by patterning the conductive material (102) and the active material (103). That is, after forming the conductive material (102) and the active material (103) on the surface of the base film (101), the groove (103a) can be formed by irradiating a laser onto the part where the groove (103a) is to be formed to remove the active material (103) and the conductive material (102).

[0078] Referring to FIG. 4, in the base film (101), in the portion excluding the blank portion (180), a number of groove portions (103a) in which neither the conductive material (102) nor the active material (103) are present are formed at regular intervals, whereas in the blank portion (180) in which there is no active material (103), a metalless portion (102a) in which the conductive material (102) is present along the edge of the lead tab (190) may be provided in the form of an engraved groove.

[0079] In the following, "metal non-existence part" refers to a part where no metal (aluminum) conductive material exists, and "metal existence part" refers to a part where a metal (aluminum) conductive material exists. Additionally, it is assumed that the "metal non-existence part" and the "metal existence part" exist in the non-existence part (180).

[0080] Referring to FIG. 4, an electrode current collector (100) according to a first embodiment of the present invention may include: a base film (101); a conductive material (102) provided on at least one surface of the upper or lower surface of the base film (101); and a lead tab (190) provided on one surface of the upper or lower surface of the base film (101) to be electrically connected to the conductive material (102).

[0081] Here, the lead tab (190) is located in a blank portion (180) that has no active material (103) but has a conductive material (102). The lead tab (190) is welded to a metal piece (not shown) provided in the blank portion (180) and connected to a base film (101), and can be electrically connected to the conductive material (102). A plurality of auxiliary blank portions (102c) may be formed at the widthwise edge of the blank portion (180). The auxiliary blank portions (102c) are parts where the active material (103) is absent and only the conductive material (102) is present, and can be provided in a form that protrudes outward from the edge of the blank portion (180).

[0082] Referring to FIG. 4, a metalless portion (102a) in which the surface of the base film (101) is exposed or the conductive material (102) is not present may be formed in a portion adjacent to the edge of the lead tab (190). The metalless portion (102a) may be formed on only one side of the base film (101) or on both sides.

[0083] Similar to the groove portion (103a), the metalless portion (102a) can be formed by coating or depositing a conductive material (102) over at least one surface of the upper or lower surface of the base film (101), and then cutting or patterning the conductive material (102) using a laser. That is, after forming the conductive material (102) on at least one surface of the base film (101), the metalless portion (102a) can be formed by irradiating a laser onto the portion where the metalless portion (102a) is to be formed to remove the conductive material (102). At this time, since the laser penetrates the base film (101), it is possible to form the metalless portion (102a) simultaneously on both the upper and lower surfaces of the base film (101).

[0084] Additionally, the metalless portion (102a) and the groove portion (103a) may be formed simultaneously by a single laser patterning process.

[0085] Referring to FIG. 4, the lead tab (190) located in the non-metallic portion (180) is positioned along the width direction of the base film (101), and a metalless portion (102a) may be formed in the portion adjacent to the edge of the lead tab (190). In the case of the electrode current collector (100) according to the first embodiment shown in FIG. 4, a metalless portion (102a) may be formed on each side in the width direction of the lead tab (190).

[0086] At this time, the metalless portion (102a) may be formed to cross both ends of the base film (101) in the width direction along the edge of the lead tab (190). Referring to FIG. 4, the lead tab (190) has a rectangular shape formed long along the width direction of the base film (101), and the metalless portion (102a) may be formed on one side of the longer side of the edge of the lead tab (190). That is, the metalless portion (102a) may be formed on both sides of the lead tab (190) in the width direction along the length direction (longer side direction) of the lead tab (190).

[0087] Two (a pair) metalless portions (102a) can be formed to be connected to both ends in the width direction of the base film (101). That is, the metalless portions (102a) can be formed to cross both ends in the width direction of the base film (101) along the edge of the lead tab (190).

[0088] However, each metalless portion (102a) may not be formed as a single unit along the width direction of the base film (101), but may be formed as two units that are broken in the middle. That is, as shown in FIG. 4, a conductive material (102) may be present in at least a part of the metalless portion (102a), or a metal portion (102b) in which the base film (101) is not exposed may be formed.

[0089] Unlike the metalless part (102a), the base film (101) is not exposed in the metal part (102b) because a conductive material (102) is present. In the metal part (102b), the surface of the base film (101) is not exposed because it is covered with the conductive material (102).

[0090] It is provided in a form where one metal part (102b) is located between two metalless parts (102a), and the two metalless parts (102a) and the one metal part (102b) are located on the same line.

[0091] Here, the metal parts (102b) formed on the metalless parts (102a) located at both ends of the width direction (short side direction) of the lead tab (190) may be formed symmetrically with respect to the centerline of the length direction (long side direction) of the lead tab (190). That is, it is preferable that the metalless parts (102a) and the metal parts (102b) located on both sides of the width direction of the lead tab (190) be provided in the same shape and at the same location relative to the lead tab (190). However, in some cases, they may be formed asymmetrically.

[0092] The metal part (102b) can be formed at the end of the lead tab (190) in the longitudinal direction, that is, at the end of the long side located between the two ends of the base film (101) in the width direction. Referring to FIG. 4, one end of the long side of the lead tab (190) is located outside the base film (101), while the other end is located between the two ends of the base film (101) in the width direction, that is, on the base film (101). The metal part (102b) is located at the end of the lead tab (190) in the long side located near the other end located on the base film (101).

[0093] As shown in FIG. 4, it is preferable that both of the two metal parts (102b) be located within a single reaction area (S1) partitioned by the groove (103a).

[0094] Figures 5b to 5d show cross-sectional views of the unoccupied portion (180). Figures 5b, 5c, and 5d are cross-sectional views along the cutting lines A1-A1, A2-A2, and A3-A3 shown in Figure 5a, respectively.

[0095] Referring to FIG. 5b, a conductive material (102) and a metalless part (102a) are formed on the upper and lower surfaces of a base film (101), and a lead tab (190) is connected to a metal piece (120) provided on one surface. At this time, the metalless part (102a) may be symmetrically provided on the upper and lower surfaces of the base film (101).

[0096] FIG. 5c shows a cross-sectional view of the metal part (102b). Referring to FIG. 5c, it can be seen that a metal part (102b) is formed on both the upper and lower sides of the base film (101) in which a conductive material (102) is present.

[0097] FIG. 5d shows a cross-sectional view of the portion without a lead tab (190). Referring to FIG. 5d, it can be seen that a conductive material (102) and a metalless portion (102a) are formed on the upper and lower surfaces of the base film (101). At this time, the metalless portion (102a) can be symmetrically provided on the upper and lower surfaces of the base film (101).

[0098] FIGS. 5b to 5d illustrate a case where the conductive material (102) is formed on both the upper and lower surfaces of the base film (101), but the conductive material (102) may be formed on only one of the upper and lower surfaces of the base film (101). When the conductive material (102) is formed on only one of the upper and lower surfaces of the base film (101), the metalless portion (102a) and the metallic portion (102b) may be formed on the same surface as the conductive material (102).

[0099] FIGS. 6a to 8d illustrate a current collector (500) for an electrode according to a second embodiment of the present invention.

[0100] Referring to FIGS. 6a, 6b, and 7, a plurality of grooves (503a) may be formed at regular intervals along the length direction of the base film (501) throughout the conductive material (502) and the active material (503). Since the grooves (503a) are identical to those shown in FIGS. 3 and 4, a repeated description is omitted. Hereinafter, a repeated description of the same content as the electrode current collector (100) shown in FIGS. 3 and 4 is omitted.

[0101] As shown in FIG. 6a, a lead tab (590) is attached to the unlined portion (580) of a base film (501) arranged lengthwise, and the base film (501) is cut in the width direction to obtain an electrode current collector (500) as shown in FIG. 7.

[0102] The electrode current collector (500) shown in FIG. 6b differs from the electrode current collector (500) shown in FIG. 6a in that it does not have a plurality of grooves (503a) formed in the conductive material (502) and the active material (503).

[0103] Referring to FIG. 7, in the base film (501), a metal-free portion (502a) in which no conductive material (502) exists along the edge of the lead tab (590) may be provided in the form of an engraved groove in the non-metallic portion (502a).

[0104] Referring to FIGS. 7 and FIGS. 8a to 8d, a current collector (500) for an electrode according to a second embodiment of the present invention may include: a base film (501); a conductive material (502) provided on at least one surface of the upper or lower surface of the base film (501); and a lead tab (590) provided on one surface of the upper or lower surface of the base film (501) to be electrically connected to the conductive material (502).

[0105] Referring to FIG. 7, the lead tab (590) located in the non-metallic portion (580) is positioned along the width direction of the base film (501), and a metalless portion (502a) may be formed in the portion adjacent to the edge of the lead tab (590). In the case of the electrode current collector (500) according to the second embodiment shown in FIG. 7, a metalless portion (502a) may be formed on both sides in the length direction and on one side in the width direction of the lead tab (590).

[0106] At this time, the metalless portion (502a) can be formed such that both ends in the length direction of the metalless portion (502a) are located at either end in the width direction of the base film (501).

[0107] Referring to FIG. 7, the lead tab (590) has a rectangular shape formed along the width direction of the base film (501), and a metalless portion (502a) is formed on one side of the long side of the edge of the lead tab (590), and a metalless portion (502a) can also be formed on one side of the short side of the edge of the lead tab (590). That is, the metalless portion (502a) can be formed continuously along the length direction (long side direction) and width direction (short side direction) of the lead tab (590).

[0108] Referring to FIG. 7, the metalless portion (502a) can be formed in a U-shape such that both ends are located at either end of the base film (501) in the width direction.

[0109] However, the metalless portion (502a) may not be formed as a single portion along the long and short directions of the lead tab (590), but may be formed as two portions that are broken in the middle. That is, as shown in FIG. 7, a metallic portion (502b) in which a conductive material (502) is present or the base film (501) is not exposed may be formed in at least a part of the metalless portion (502a).

[0110] Here, the metal part (502b) may be formed in a portion close to the end located between the two ends in the width direction of the base film (501) among the two ends in the length direction (long side direction) of the lead tab (590). That is, the metal part (502b) may be formed in a portion close to the short side of the lead tab (590). Accordingly, a metal-free portion (502a) may be formed on one side of the long side of the lead tab (590), and a metal part (502b) may be formed on one side of the short side.

[0111] A metal portion (502b) provided on one side of the short side of the lead tab (590) can be formed to cut the metal portion (502a), which is continuously formed along the edge of the lead tab (590), at a single point.

[0112] Additionally, the length of the metal part (502b) can be formed to be shorter than the width direction length of the lead tab (590), that is, the length of the short side.

[0113] As shown in FIG. 7, a metal part (502b) may be located within a reaction area (S2) partitioned by a groove part (503a).

[0114] Figures 8b to 8d show cross-sectional views of the unoccupied portion (580). Figures 8b, 8c, and 8d are cross-sectional views along the cutting lines B1-B1, B2-B2, and B3-B3 shown in Figure 8a, respectively.

[0115] Referring to FIG. 8b, a conductive material (502) and a metalless portion (502a) are formed on the upper and lower surfaces of a base film (501), and a lead tab (590) is connected to a metal piece (520) provided on one surface. At this time, the metalless portion (502a) may be symmetrically provided on the upper and lower surfaces of the base film (501).

[0116] FIG. 8c shows a cross-sectional view of the metal-containing portion (502b). Referring to FIG. 8c, it can be seen that both a metal-free portion (502a) where the conductive material (502) is not present and a metal-containing portion (102b) where the conductive material (502) is present are formed on both the upper and lower sides of the base film (501). Here, compared to the case of FIG. 8b, the metal-free portion (502a) in FIG. 8c can be formed longer.

[0117] In the case of FIGS. 8b and 8c, the metalless portion (502a) and the metal portion (502b) may be symmetrically provided on both the upper and lower sides of the base film (501).

[0118] FIG. 8d shows a cross-sectional view of the portion without the lead tab (590). Referring to FIG. 8d, it can be seen that a conductive material (502) is formed on both the upper and lower surfaces of the base film (501).

[0119] FIGS. 8b to 8d illustrate a case where the conductive material (502) is formed on both the upper and lower surfaces of the base film (501), but the conductive material (502) may be formed on only one of the upper and lower surfaces of the base film (501). When the conductive material (502) is formed on only one of the upper and lower surfaces of the base film (501), the metalless portion (502a) and the metallic portion (502b) are formed on the same surface as the conductive material (502).

[0120] In the electrode current collector (100, 500) according to the present invention, the lead tab (190, 590) can be welded to a metal piece (120, 520) by ultrasonic welding, laser welding, or spot welding.

[0121] When a lead tab (190,590) is welded to one of the metal pieces (120,520) provided on at least one of the two sides of a base film (101,501), the lead tab (190,590) is welded and connected to the metal piece (120,520) provided on the base film (101,501) by melting the base film (101,501), and as a result, the lead tab (190,590) can be electrically connected simultaneously with the conductive material (102,502) provided on both sides of the base film (101,501).

[0122] Meanwhile, when an external short circuit occurs in a secondary battery including an electrode current collector (100, 500) according to the present invention as illustrated in FIGS. 3 to 8d, the short-circuit current flows only in the metal parts (102b, 502b), so if the metal parts (102b, 502b) are broken, the short-circuit current cannot flow.

[0123] When an external short circuit occurs in a secondary battery including an electrode current collector (100, 500) according to the present invention, the short circuit current flows through the electrode current collector (100, 500) via the lead tab (190, 590), and all of the external short circuit current flowing through the conductive material (102, 502) of the electrode current collector (100, 500) flows to the metal part (102b, 502b).

[0124] Since there is no conductive material (102, 502) in the non-metallic part (102a, 502a), current cannot flow, so all short-circuit current flows only through the metallic part (102b, 502b). Therefore, the metallic part (102b, 502b) functions as a conductive part.

[0125] When an external short-circuit current flows only in the metal part (102b, 502b), the resistance of the metal part (102b, 502b) is high, so the metal part (102b, 502b) melts due to the external short-circuit current that increases instantaneously, or the potential of the metal part (102b, 502b) drops to near the negative potential (i.e., < 0.3 volt, negative Li metal), and the conductive material (102, 502) reacts with the electrolyte, causing the conductive material (102, 502) to break as if corroded, thereby lowering (reducing) or blocking the external short-circuit current.

[0126] In this way, the metal portion (102b, 502b) of the electrode current collector (100, 500) according to the present invention can block the flow of short-circuit current when an external short circuit occurs.

[0127] As a result, the lifespan of a secondary battery using an electrode current collector (100, 500) according to the present invention can be extended, and the safety of the secondary battery can be ensured.

[0128] Meanwhile, the inventors of the present application determined that the width (size) of the metal parts (102b, 502b) is an important parameter that determines whether the metal parts (102b, 502b) break upon short circuit. To verify this, experiments were conducted to determine under what conditions the metal parts (102b, 502b) break while varying the size of the metal parts (102b, 502b) and the current. The experimental results are as shown in [Table 1] below.

[0129] (1) Specimen: 6μm PET (base film) + aluminum conductive material of 1.0μm or less coated on each side by sputtering

[0130] (2) Laser

[0131] - HG Tech's LSF20D

[0132] - 30W integrated laser

[0133] - Laser wavelength: 1,064±1.0nm

[0134] - Average output power: 30±0.8W

[0135] (3) Experimental conditions: Loading level 12.5 mg / cm² 2 Standard speed 300mm / s, power 60%

[0136] (3) Experimental Method: Using a power supply, gradually increase the current until the insulation is maintained and the current drops to near 0A, and measure and record the current value just before it drops to 0A.

[0137] Psalm 123456 Current(A) Current(A) Current(A) Current(A) Current(A) Current(A) #14.55.25.15.05.35.1 #23.53.43.63.53.13.0 #32.82.92.62.72.72.5

[0138] The experiment in [Table 1] was performed on a lithium secondary battery comprising a lead tab (190) welded to a current collector (100) for a positive electrode as shown in FIG. 3.

[0139] In [Table 1], Specimen #1 is the case where the width of the metal part (102b) is 4mm, Specimen #2 is the case where the width of the metal part (102b) is 3mm, and Specimen #3 is the case where the width of the metal part (102b) is 2mm.

[0140] [Table 1] records the current value at which the molten metal part (102b) is cut off as the current (A) value increases. A total of 6 repeated experiments were conducted for each specimen.

[0141] Experimental results confirmed that the smaller the width of the metal part (102b), the more the current path is cut off even when the current value is small.

[0142] In this way, the electrode current collector (100, 500) according to the present invention is provided with a metal-free portion (102a, 502a) around the lead tab (190, 590) in which the thickness of the conductive material (102, 502) is relatively thin or non-existent, thereby enabling the electrochemical fuse function or short-circuit current blocking function to be exerted in the metal-containing portion (102b, 502b) where the conductive material (102, 502) exists and functions as a current-carrying portion, thereby preventing the temperature of the secondary battery from rising when an external short circuit occurs and blocking the short-circuit current, thereby ensuring the safety of the secondary battery.

[0143] As described above, the present invention has been explained by specific details such as specific components, limited embodiments, and drawings; however, this is provided merely to aid in a more comprehensive understanding of the invention, and the invention is not limited to the above embodiments. A person skilled in the art to which the invention pertains can make various modifications and variations from this description. Therefore, the scope of the invention should not be limited to the described embodiments, and all things equivalent to or having equivalent variations to the claims set forth below, as well as the claims themselves, shall be considered to fall within the scope of the concept of the invention.

Claims

1. Base film; A conductive material provided on at least one surface of the upper or lower surface of the base film; and A lead tab provided on one of the upper or lower surfaces of the base film to be electrically connected to the conductive material; comprising In the portion adjacent to the edge of the lead tab, the surface of the base film is exposed or a metalless portion is formed where the conductive material is not present. An electrode current collector characterized in that the metalless portion is formed to cross both ends of the base film in the width direction along the edge of the lead tab, or both ends of the metalless portion in the length direction are located at either end of the base film in the width direction.

2. In Paragraph 1, The above-mentioned metal-free part is, An electrode current collector characterized by being formed on each side in the width direction of the lead tab along the length direction of the lead tab.

3. In Paragraph 2, A current collector for an electrode characterized in that at least a portion of the above-mentioned metalless portion is formed such that the conductive material is present or the base film is not exposed.

4. In Paragraph 3, The above-mentioned metal part is, An electrode current collector characterized by being formed in a portion close to one end located between the two ends in the width direction of the base film among the two ends in the length direction of the lead tab.

5. In Paragraph 4, An electrode current collector characterized in that the metal parts formed on the metalless parts located at both ends in the width direction of the lead tab are formed symmetrically with respect to the centerline in the length direction of the lead tab.

6. In Paragraph 1, The electrode current collector is characterized by the above-mentioned metal-free portion being formed on one side in the length direction and one side in the width direction of the above-mentioned lead tab.

7. In Paragraph 6, A current collector for an electrode characterized in that at least a portion of the above-mentioned metalless portion is formed such that the conductive material is present or the base film is not exposed.

8. In Paragraph 7, The above-mentioned metal part is, An electrode current collector characterized by being formed in a portion close to one end located between the two ends in the width direction of the base film among the two ends in the length direction of the lead tab.

9. In Paragraph 8, An electrode current collector characterized in that the above-mentioned metal portion is formed to interrupt the above-mentioned metal portion, which is continuously formed along the periphery of the above-mentioned lead tab, at a single point.

10. In Paragraph 7, An electrode current collector characterized by the length of the above-mentioned metal part being shorter than the width direction length of the above-mentioned lead tab.

11. In Paragraph 3, The above-mentioned metal part is an electrode current collector characterized by blocking the flow of short-circuit current when an external short circuit occurs.

12. In Paragraph 7, The above-mentioned metal part is an electrode current collector characterized by blocking the flow of short-circuit current when an external short circuit occurs.

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