Multilayer conductive tape, secondary battery including same, and method for producing same

Abstract

The present invention relates to a multilayer conductive tape including an adhesive layer; an electrically conductive layer located on one side of the adhesive layer; an insulating layer located on one side of the electrically conductive layer; and a protective layer for protecting an outer surface of the insulating layer.

Description

[Technical field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0105969, filed with the Korean Intellectual Property Office on August 11, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a multilayer conductive tape and a secondary battery including the same, and more particularly to a multilayer conductive tape that prevents a deterioration in performance of a secondary battery due to disconnection at a contact portion between an electrode tab and an electrode lead via a multilayer insulating tape, a secondary battery including the same, and a method for manufacturing the same. [Background technology]

[0003] As technological development and demand for mobile devices increases, the demand for batteries as an energy source is growing rapidly, and accordingly, much research is being conducted on secondary batteries that can meet various needs.

[0004] In terms of shape, there is increasing demand for thin-walled rectangular and pouch-type secondary batteries that can be used in products such as mobile phones, while in terms of materials, there is growing demand for lithium-ion batteries, lithium-ion polymer batteries, and other batteries that have high energy density, discharge voltage, and output stability.

[0005] Typically, a pouch-type secondary battery is configured to include an electrode assembly, an electrode tab extending from the electrode assembly, an electrode lead welded to the electrode tab, a pouch-type exterior material that houses the electrode assembly and is made of a laminate sheet of polymer resin and aluminum, and an insulating tape that is adhered to the electrode tab and the portion where the electrode lead is welded.

[0006] The insulating tape can improve the insulation of the anode or cathode. However, since the adhesive area of ​​the insulating tape is small and the insulating tape has no electrical conductivity, if the electrode tab and the electrode lead are cut, the secondary battery will no longer function, making it impossible to use the secondary battery.

[0007] Therefore, there is an increasing need for a secondary battery structure that can fundamentally solve these problems, ensure process stability, and dramatically improve the problem of defective rates such as broken electrode tabs and electrode leads. Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned problems of the conventional technology, the present invention provides a multilayer conductive tape that has an electrically conductive layer located at a portion where an electrode tab and an electrode lead contact each other, and that conducts electricity to the outside even if a break occurs in the electrode tab or electrode lead, as well as a secondary battery including the same and a method for manufacturing the secondary battery. [Means for solving the problem]

[0009] One embodiment of the present invention provides a multilayer conductive tape including an adhesive layer; an electrically conductive layer located on one side of the adhesive layer; an insulating layer located on one side of the electrically conductive layer; and a protective layer for protecting an outer surface of the insulating layer.

[0010] In another embodiment of the present invention, there is provided a secondary battery including: an electrode assembly in which at least one electrode and a separator are alternately stacked; a battery case in which the electrode assembly is housed; electrode tabs extending from the electrodes and stacked and welded according to polarity; electrode leads stacked and connected to the electrode tabs, a portion of which protrudes outside the battery case; and the multilayer conductive tape.

[0011] In still another embodiment of the present invention, a secondary battery is provided in which the width W of the multilayered conductive tape extends from ends of one side and the other side of the electrode assembly facing the battery case to at least a part of the overlapping portion where the electrode tab and the electrode lead are connected.

[0012] In yet another embodiment of the present invention, there is provided a method for manufacturing a secondary battery, the method including: manufacturing an electrode assembly by alternately stacking a plurality of electrodes and separators; a pre-welding step of gathering and welding electrode tabs provided at ends of the plurality of electrodes; a main welding step of overlapping and welding electrode leads to the ends of the electrode tabs; adhering a multilayered conductive tape to at least one of the upper and lower sides of a position where the electrode tabs and the electrode leads overlap; and thermocompressing an adhesive surface of the multilayered conductive tape by heat. Effect of the Invention

[0013] The multilayer conductive tape according to an embodiment of the present invention has an electrically conductive layer located at a portion where an electrode tab and an electrode lead contact each other, thereby preventing current from flowing due to breakage or bending of an electrode tab included in a secondary battery.

[0014] In addition, the multilayer conductive tape is bonded over an area larger than the area of ​​the portion where the electrode tab and the electrode lead are welded, which makes it possible to prevent problems such as breakage or bending of the electrode tab. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing a conventional insulating tape. [Diagram 2] 1 is a cross-sectional view showing a multi-layer conductive tape according to one embodiment of the present invention. [Diagram 3] 1 is a perspective view showing a secondary battery according to an embodiment of the present invention; [Figure 4] 4 is a partial cross-sectional view of a secondary battery according to an embodiment of the present invention taken along line AA' in FIG. [Diagram 5] 4 is a partial cross-sectional view of a secondary battery including a multilayer conductive tape according to another embodiment of the present invention taken along line AA' in FIG. [Figure 6] 1 is a flowchart of a method for manufacturing a secondary battery according to an embodiment of the present invention. [Explanation of symbols]

[0016] 100...Secondary battery 10, 10' Multi-layer conductive tape 11...adhesive layer 12 Electrically conductive layer 13 Insulation layer 14...Protective layer 20...electrode assembly 30 Electrode tab 40 Electrode lead DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the present invention will be described in detail with reference to the drawings. However, the drawings are for illustrating the present invention, and the scope of the present invention is not limited by the drawings.

[0018] FIG. 2 is a cross-sectional view showing a multilayer conductive tape 10 according to one embodiment of the present invention, FIG. 3 is a perspective view showing a secondary battery 100 according to one embodiment of the present invention, FIG. 4 is a portion of a cross-sectional view of a secondary battery 100 according to one embodiment of the present invention taken along A-A' in FIG. 3, and FIG. 5 is a portion of a cross-sectional view of a secondary battery 100 including a multilayer conductive tape 10' according to another embodiment of the present invention taken along A-A' in FIG. 3.

[0019] The secondary battery 100 includes a multi-layer conductive tape 10 , an electrode assembly 20 , an electrode tab 30 , and an electrode lead 40 .

[0020] Referring to FIG. 2, multi-layer conductive tape 10 includes an adhesive layer 11, an electrically conductive layer 12, an insulating layer 13, and a protective layer .

[0021] The adhesive layer 11 directly contacts an object to which the multilayer conductive tape 10 is attached, and imparts adhesiveness to the multilayer conductive tape 10. Here, the object to which the multilayer conductive tape 10 is attached may be, for example, an electrode tab 30 and an electrode lead 40 of a secondary battery 100, which will be described later.

[0022] The adhesive layer 11 may be made of a resin having adhesiveness at room temperature. The resin contained in the adhesive layer 11 is not particularly limited as long as it can adhere to the object to be attached without damaging it, and may include, for example, at least one selected from the group consisting of acrylic, synthetic rubber, and ethyl acetate.

[0023] The adhesive layer 11 may also contain a highly electrically conductive material to pass an electric current through the electrically conductive layer 12 described below. The adhesive layer 11 may be formed by mixing an adhesive resin with a highly electrically conductive material. The highly electrically conductive material may contain metals or carbon-based materials, and may contain, for example, any one or more of copper, aluminum, titanium, silicon, magnesium, nickel, and stainless steel.

[0024] Alternatively, the adhesive layer 11 may be formed by applying an adhesive resin to a substrate having a plurality of holes formed therein penetrating in the lamination direction of the multilayer conductive tape 10. For example, the substrate may be provided in a mesh or dot pattern. The adhesive layer 11 may contain a conductive material in one or more of the substrate and the resin.

[0025] For example, the substrate may include metal fibers or metal foils, plated fibers, plated nonwoven fabrics, etc., made of one selected from the group consisting of nickel, copper, stainless steel, silver, and gold.

[0026] The adhesive layer 11 may be formed to a thickness of 1 μm to 20 μm, preferably 3 μm to 15 μm, and more preferably 6 μm to 12 μm. If the thickness of the adhesive layer 11 is less than 1 μm, the adhesive strength decreases and the adhesive layer may peel off from the object to be adhered, and if the thickness of the adhesive layer 11 exceeds 20 μm, the volume occupied by the object to be adhered becomes too large.

[0027] An electrically conductive layer 12 is located on one side of adhesive layer 11 and enables electrical current to be passed through multi-layer conductive tape 10 .

[0028] In other words, when the multilayer conductive tape 10 according to the present invention is applied to the portion where the electrode tab 30 and the electrode lead 40 are welded, it has the effect of expanding the path through which current flows beyond the electrode tab 30 and the electrode lead 40, thereby increasing the electrical conductivity.

[0029] Furthermore, if the electrode tab 30 is damaged, such as cut or broken, and becomes disconnected, a current may flow from the electrode tab 30 to the electrode lead 40 via the electrically conductive layer 12. In other words, the secondary battery 100 to which the multilayer conductive tape 10 according to the present invention is attached does not experience performance degradation due to disconnection of the electrode tab 30.

[0030] The electrically conductive layer 12 may be formed of a metal. The electrically conductive layer 12 may include a metal or an alloy including at least one metallic element selected from iron, copper, lead, tin, zinc, gold, platinum, mercury, nickel, aluminum, magnesium, cadmium, uranium, thorium, plutonium, beryllium, titanium, zirconium, niobium, vanadium, hafnium, indium, tantalum, molybdenum, tungsten, silicon, germanium, sodium, potassium, and gallium.

[0031] That is, electrically conductive layer 12 may be a layer made of one of the above metals, or may be formed of an alloy in which two or more of the above metals are mixed.

[0032] For example, the electrically conductive layer 12 may be formed of an aluminum and copper alloy, in which the weight ratio of aluminum to copper in the alloy is 1:2 to 1:5, preferably 1:2 to 1:4, and more preferably 1:3.

[0033] If the weight ratio of aluminum to copper is less than 1:2, the weight of the electrically conductive layer 12 becomes heavy, which may cause problems in processing the electrically conductive layer 12. If the weight ratio of aluminum to copper is less than 1:5, the strength of the electrically conductive layer 12 may decrease.

[0034] The electrically conductive layer 12 preferably has a thickness of 20 μm to 60 μm, and more preferably 30 μm to 50 μm. If the thickness of the electrically conductive layer 12 is less than 20 μm, the electrical conductivity of the multilayer conductive tape 10 decreases, whereas if the thickness exceeds 60 μm, the increase in electrical conductivity is too small to be economically efficient.

[0035] Insulating layer 13 is located on one side of electrically conductive layer 12 , and may be located on the side of electrically conductive layer 12 that faces adhesive layer 11 with respect to electrically conductive layer 12 .

[0036] The insulating layer 13 increases the insulation between the electrically conductive layer 12 and the outside. That is, the insulating layer 13 can primarily prevent current from flowing from the electrode assembly 20 to the outside.

[0037] The insulating layer 13 may be provided with a thickness of 20 μm to 60 μm. Preferably, the insulating layer 13 may be provided with a thickness of 20 μm to 50 μm, more preferably, 20 μm to 40 μm.

[0038] When the thickness of the insulating layer 13 is within the above range, the insulation efficiency between the electrically conductive layer 12 and the battery case can be maximized.

[0039] The insulating layer 13 may be formed of an organic material, which may be selected from the group consisting of polyethylene terephthalate, polyimide, polypropylene, polystyrene, polybutylene, polyethylene, and combinations thereof.

[0040] Protective layer 14 is located in a direction opposite electrically conductive layer 12 with respect to insulating layer 13, and serves to prevent insulating layer 13 from being damaged.

[0041] The protective layer 14 may contain one or more of an organic material and an inorganic material. That is, the protective layer 14 may be provided as a single layer made of an organic material or an inorganic material, or may be provided as a multilayer made of an organic material and an inorganic material.

[0042] For example, when the protective layer 14 is provided in multiple layers, the protective layer 14 may be provided in a form in which an organic material layer, an inorganic material layer, and an organic material layer are laminated in this order, or an organic material layer is wrapped in an inorganic material layer. When the inorganic material layer wraps the organic material layer like a bag, the inorganic material layer can protect the organic material layer, which is sensitive to oxygen and moisture.

[0043] Alternatively, the protective layer 14 may be a composite material layer in which an organic material and an inorganic material are mixed. In this case, the weight ratio of the organic material to the inorganic material in the protective layer 14 may be 1:7 to 1:12, preferably 1:8 to 1:10, and more preferably 1:9.

[0044] If the weight ratio of the organic material to the inorganic material contained in the protective layer 14 is less than 1:7, the content of the inorganic material is low, and the heat resistance and strength may decrease. If the weight ratio of the organic material to the inorganic material exceeds 1:12, the moisture permeability of the multilayer conductive tape 10 increases, causing a problem of moisture permeating into the electrode tabs 30 and the electrode leads 40.

[0045] That is, the protective layer 14 can improve the heat resistance and mechanical strength of the multilayer conductive tape.

[0046] The protective layer 14 may be provided with a thickness of 20 μm to 60 μm. Preferably, the protective layer 14 may be provided with a thickness of 20 μm to 50 μm, more preferably, 20 μm to 40 μm.

[0047] The multilayer conductive tape 10 according to the present invention may further include a second insulating layer. The second insulating layer is located on the opposite side of the protective layer 14 from the insulating layer 13.

[0048] The second insulating layer can improve the insulation between the secondary battery 100 and the battery case in which the secondary battery 100 is mounted, and can prevent current from flowing from the electrode assembly 20 to the battery case.

[0049] The second insulating layer may be formed of an organic material, which may be selected from the group consisting of polyethylene terephthalate, polyimide, polypropylene, polystyrene, polybutylene, polyethylene, and combinations thereof.

[0050] The second insulating layer may have a thickness of 20 μm to 60 μm. Preferably, the second insulating layer may be provided with a thickness of 20 μm to 50 μm, more preferably 20 μm to 40 μm.

[0051] When the thickness of the second insulating layer satisfies the above range, it is possible to increase the sealing force and insulating efficiency between the battery case and the electrode tab 30 and between the battery case and the electrode lead 40. In addition, it is possible to prevent the problem of moisture permeating into the electrode assembly 20 due to damage to the insulating layer 13 and the second insulating layer.

[0052] The second insulating layer protects the welded portion where the electrode tab 30 and the electrode lead 40 are welded, and minimizes the distance between the electrode lead 40 and the welded portion and the battery case, thereby minimizing sealing interference of the multilayer conductive tape 10 between the electrode lead 40 and the welded portion where the electrode tab 30 and the electrode lead 40 are welded and the battery case.

[0053] The anode and cathode included in the electrode assembly 20 may be stacked in a pre-welded state, with the anode cells stacked together and the cathode cells stacked together. The electrode assembly 20 may be stacked in the order of pre-welded cathode / separator / anode / separator / cathode... Then, the electrode assembly 20 may be housed in a battery case and main-welded.

[0054] The electrode tabs 30 extend from one side of the electrode assembly 20 and may include an anode tab and a cathode tab. The electrode assembly 20 may include an anode tab and a cathode tab that extend from one side of the anode and cathode, respectively, after the anode and cathode are pre-welded. The anode tab and the cathode tab may be located in the same direction with respect to the electrode assembly 20 and spaced apart by a certain distance.

[0055] The electrode lead 40 extends the electrode tab 30 for connection to an external subject, and may be connected to the electrode tab 30 by welding.

[0056] The multi-layered conductive tape 10 is adhered to the portion where the electrode tab 30 and the electrode lead 40 are connected, so that the electrode tab 30 and the electrode lead 40 can be electrically connected to each other.

[0057] When the connection portion between the electrode tab 30 and the electrode lead 40 is damaged and the electrode tab 30 and the electrode lead 40 are disconnected, the multilayer conductive tape 10 can transmit electric current to an external object through the adhesive layer 11 and the electrically conductive layer 12 included in the multilayer conductive tape 10.

[0058] The multi-layer conductive tape 10 may be adhered to one or more of the upper and lower sides of the joining area between the electrode tab 30 and the electrode lead 40 .

[0059] In one embodiment, the multi-layered conductive tape 10 may be adhered to the upper and lower sides of the joint area between the electrode tab 30 and the electrode lead 40. The multi-layered conductive tape 10 may be sealed by fusing the edges at both ends of the multi-layered conductive tape 10 through heat compression bonding. Therefore, the multi-layered conductive tape 10 can protect the joint area between the electrode tab 30 and the electrode lead 40 from external air and oxygen.

[0060] The edges at both ends of the multilayer conductive tape 10 according to an embodiment may refer to portions where the electrode tabs 30 and the electrode leads 40 are not located in a direction perpendicular to the direction in which the electrode leads 40 extend from the electrode tabs 30. In other words, the multilayer conductive tape 10 may be attached in a direction perpendicular to the direction in which the electrode leads 40 extend from the electrode tabs 30, and portions where the electrode tabs 30 and the electrode leads 40 are not included may be generated between the multilayer conductive tape 10 located above and below the portions where the electrode tabs 30 and the electrode leads 40 overlap.

[0061] Here, the upper and lower sides may refer to one side and the other side in the lamination direction of the electrode tab 30 and the electrode lead 40 .

[0062] The multilayer conductive tape 10 may cover at least a portion of the overlapping portion where the electrode tabs 30 and the electrode leads 40 are connected. That is, the width W of the multilayer conductive tape 10 may be wider than the width of the overlapping portion where the electrode tabs 30 and the electrode leads 40 are connected. Here, the width R of the overlapping portion where the electrode tabs 30 and the electrode leads 40 are connected may mean the length in the same direction as the width of the multilayer conductive tape 10.

[0063] Referring to FIG. 4, the width of the multilayer conductive tape 10 according to one embodiment may be 1.5 to 5 times, preferably 2 to 4 times, and more preferably 2.5 to 3.5 times the width of the electrode tab 30 and the electrode lead 40 connected together.

[0064] 5, the width of the multilayer conductive tape 10' according to another embodiment may extend in the width direction of the multilayer conductive tape 10 from ends of one and the other sides of the electrode assembly 20 facing the battery case to at least a part of the overlapping portion R where the electrode tab 30 and the electrode lead 40 are connected. The end of the electrode assembly 20 to which the multilayer conductive tape 10' is adhered may include the end in the direction in which the electrode tab extends.

[0065] The width W of the multilayer conductive tape 10 refers to the direction perpendicular to the direction in which the electrode tabs 30 and the electrode leads 40 are laminated, or the distance in the direction in which the electrode leads 40 extend from the electrode tabs 30 .

[0066] The multilayer conductive tape 10 envelops the entire connecting portion between the electrode tab 30 and the electrode lead 40, thereby protecting the electrode tab 30 and the electrode lead 40 from damage and expanding the flow path through which current flows. Here, the connecting portion is the position where the electrode tab 30 and the electrode lead 40 are stacked and connected, and means the portion where the electrode tab 30 and the electrode lead 40 overlap. In other words, the connecting portion between the electrode tab 30 and the electrode lead 40 may mean the portion where the electrode tab 30 and the electrode lead 40 overlap, or may have the same meaning as the overlapping portion.

[0067] After the multilayer conductive tape 10 is adhered to the connecting portion between the electrode tab 30 and the electrode lead 40, the contact surfaces of the electrode tab 30 and the electrode lead 40 with the multilayer conductive tape 10 may be sealed by heat compression bonding.

[0068] For example, thermocompression bonding can be performed by applying a certain temperature to the multilayer conductive tape 10 to melt the protective layer 14 or the second insulating layer, and then applying pressure to the multilayer conductive tape 10 from the outside to fuse the contact surfaces of the electrode tabs 30 and electrode leads 40 with the multilayer conductive tape 10.

[0069] FIG. 6 is a flowchart of a method for manufacturing a secondary battery according to an embodiment of the present invention.

[0070] The method for manufacturing a secondary battery includes a step of manufacturing an electrode assembly (S100), a pre-welding step (S200), a main-welding step (S300), a multi-layer conductive tape bonding step (S400), a thermocompression bonding step (S500), and a step of assembling the electrode assembly and a battery case to manufacture a secondary battery (S600).

[0071] In the step of manufacturing the electrode assembly (S100), a plurality of electrodes and a separator are alternately stacked to manufacture the electrode assembly, and may be stacked in the following order: anode, separator, cathode, separator, anode . . .

[0072] More specifically, the electrode assembly may include a plurality of anode electrodes and a plurality of cathode electrodes stacked together, and may include a separator between the anode electrodes and the cathode electrodes, and electrode tabs corresponding to the polarities may be connected to the anode and cathode electrodes.

[0073] The pre-welding step (S200) is for gathering and welding electrode tabs included in the electrode assembly in the electrode assembly manufacturing step (S100), and may weld anode tabs and cathode tabs according to polarity.

[0074] For example, the electrode assembly may include a plurality of anode electrodes, and therefore a plurality of anode tabs may also be included. The electrode assembly may be formed by laminating a plurality of anode tabs to form an anode tab stack portion, and then welding the anode tabs to pre-weld them.

[0075] Pre-welding may then be applied to all surfaces where the electrode tabs will be laminated and contacted.

[0076] The main welding step (S300) is to stack and weld an electrode lead to an end of an electrode tab, and the electrode lead may be welded to the top or bottom of the electrode tab.

[0077] The electrode lead may be welded to the location where the electrode tab is pre-welded, for example, the electrode lead may be placed below the pre-welded surface where the anode tab is pre-welded and welded, and all surfaces in contact with the electrode tab may be welded.

[0078] The electrode lead may be positioned so that the electrode tab overlaps the entire pre-welding surface, or may be positioned so that the electrode tab overlaps a portion of the pre-welding surface.

[0079] In the step of adhering the multilayer conductive tape (S400), the multilayer conductive tape is adhered to at least one of the upper and lower sides of the laminated portion in which the electrode tabs and the electrode leads are laminated, and in the step of thermocompression bonding (S500), heat and pressure are applied to the adhesive surface of the multilayer conductive tape to perform thermocompression bonding.

[0080] Here, the adhesive surface means the surface where the multilayer conductive tape comes into contact with the electrode tab or electrode lead as a result of the adhesion of the multilayer conductive tape. In the case where the multilayer conductive tape is adhered only to the upper side of the laminated portion, an adhesive surface between the electrode tab and the multilayer conductive tape may be formed in the direction of the electrode assembly of the multilayer conductive tape, and an adhesive surface between the electrode lead and the multilayer conductive tape may be formed in the opposite direction.

[0081] The adhesive surface may then be sealed by thermocompression. For example, the multi-layer conductive tape may be placed on the top of the multi-layer conductive tape by applying heat and pressure to the thermocompression means, and the layer in contact with the thermocompression means may melt and be fused to the electrode tab or electrode lead.

[0082] The multilayer conductive tape may be thermocompression bonded at a temperature of 50°C to 300°C and a pressure of 0.2 MPa to 1.0 MPa, preferably at a temperature of 100°C to 250°C and a pressure of 0.2 MPa to 0.7 MPa, and more preferably at a temperature of 160°C to 200°C and a pressure of 0.2 MPa to 0.4 MPa.

[0083] If the thermocompression conditions are a temperature below 50°C and a pressure below 0.2 MPa, the multilayer conductive tape will not be sealed to the electrode tab and electrode lead, and boundaries may form at the portions where the multilayer conductive tape and the electrode tab or the multilayer conductive tape and the electrode lead are bonded, reducing the adhesive strength between the multilayer conductive tape and the electrode tab and the electrode lead.

[0084] Furthermore, when the thermocompression conditions exceed 300°C and the pressure exceeds 1.0 MPa, the energy consumption increases, while the synergistic effect of adhesion and sealing of the multi-layer conductive tape is minimal.

[0085] For example, when a multi-layer conductive tape is adhered to the upper and lower sides of a laminate where electrode tabs and electrode leads are laminated and welded, the multi-layer conductive tapes located on the upper and lower sides of the laminate will be adhered to each other in areas where the electrode tabs and electrode leads are not located.

[0086] At this time, by subjecting the adhesive surfaces of the multilayer conductive tape to thermocompression bonding, the portions where the multilayer conductive tapes are bonded together can also be sealed by thermocompression bonding, allowing the multilayer conductive tape to be sealed in a bag-like shape.

[0087] The step of assembling the electrode assembly and the battery case to manufacture the secondary battery (S600) may further include the steps of preparing a battery case (S610), assembling the battery case and the electrode assembly (S620), and sealing the battery case (S630).

[0088] The step of preparing a battery case (S610) may involve pressing a battery case precursor made of a ductile material, for example, a laminated sheet, with a punch to form a lower case including a receiving portion in which the electrode assembly can be received.

[0089] After the electrode assembly is accommodated in the receiving portion of the lower case, an upper case that covers the electrode assembly from above may be brought into contact with and sealed to the lower case so that the electrode assembly does not fall out of the battery case. At this time, the battery case may be sealed so that the electrode tabs and electrode leads are exposed.

[0090] While the present invention has been described above with reference to preferred embodiments, those skilled in the art will appreciate that various modifications and variations of the present invention may be made without departing from the spirit and scope of the present invention as set forth in the following claims. EXAMPLES

[0091] <Example 1> The secondary battery according to the present invention shown in Fig. 4 is a secondary battery in which a multilayer conductive tape including an adhesive layer, an electrically conductive layer, an insulating layer, a protective layer, and a second insulating layer is attached to a welded portion where an electrode tab and an electrode lead are welded. In this case, the secondary battery according to the embodiment was produced by attaching the multilayer conductive tape after disconnecting the welded portion.

[0092] The adhesive layer is prepared by coating both sides of the copper foil with acrylic resin, and is provided with a thickness of 10 μm.

[0093] The electrically conductive layer is an aluminum plate having a thickness of 40 μm, which is attached to one side of the adhesive layer.

[0094] The insulating layer is a 40 μm thick plate made of polypropylene (PP) and attached to one side of the electrically conductive layer, that is, to one side of the electrically conductive layer opposite to the side in contact with the adhesive layer.

[0095] The protective layer is a 40μm-thick layer of alumina and polypropylene attached to one side of the insulating layer, and the second insulating layer is a 30μm-thick plate containing polypropylene (PP) attached to one side of the protective layer.

[0096] <Example 2> The secondary battery was constructed in the same manner as in Example 1, except that the electrically conductive layer was a copper plate having a thickness of 40 μm and was attached to one side of the adhesive layer.

[0097] <Comparative Example> The secondary battery is fabricated by attaching a multilayer tape including an adhesive layer and an insulating layer to a welding area where an electrode tab and an electrode lead are welded. The secondary battery according to the comparative example was fabricated by attaching the multilayer tape to a good electrode assembly in which no disconnection occurred in the welding area.

[0098] The adhesive layer and the insulating layer are configured similarly to the first embodiment.

[0099] [Table 1]

[0100] [Table 2]

[0101] The capacity of the secondary batteries was measured by charging them at 1C up to 4.2V under constant current / constant voltage (CC / CV) conditions at 25°C, and then discharging them at 1C down to 2.5V under constant current (CC) conditions, and then measuring the discharge capacity.

[0102] The insulation resistance and insulation voltage were measured by applying a voltage of 50 V between the cathode and pouch and between the anode and pouch of the secondary battery and measuring the resistance after 1 second to confirm whether leakage current flowed, and evaluating the resistance level against this to evaluate whether insulation was achieved between the anode / cathode and the pouch.

[0103] The alternating current impedance (AC-imp) was measured using an EIS device (Biologic potentiostat).

[0104] The tensile strength was measured using an INSTRON 4465 device in accordance with the ASTM D638 standard.

[0105] Referring to Table 1, it can be seen that the physical properties such as capacity, insulation resistance, insulation voltage, and AC impedance of Example 1, which includes a break at the welded portion where the electrode tab and the electrode lead are welded, are similar to those of the good secondary battery of the comparative example.

[0106] More specifically, since the secondary battery according to Example 1 was not affected by disconnection at the welded portion and current was passed through the multilayer conductive tape, the AC impedance value of Example 1 showed similar characteristics to the AC impedance value of the comparative example.

[0107] The secondary battery of Example 1 showed similar characteristics to the comparative example, in which the insulation resistance value and insulation voltage value were good, because no current flowed between the welded portion and the battery case, more specifically, due to the insulating layer, protective layer, and second insulating layer between the electrically conductive layer of the multilayer conductive tape and the battery case.

[0108] Referring to Table 2, it can be seen that the tensile strength of Examples 1 and 2 was 21% to 26% higher than that of the Comparative Example. Here, the tensile strength is the strength measured when either the welded portion or the multilayer conductive tape (or the multilayer tape) or both are cut and no current flows.

[0109] In the secondary battery of the comparative example, when the welded portion where the multilayer tape is bonded is pulled, no current flows if the welded portion is cut, and therefore the tensile strength is the strength value at the time when the welded portion is cut, which is relatively smaller than those of Examples 1 and 2.

[0110] On the other hand, in the secondary batteries according to Examples 1 and 2, even if the welded portion is cut, the current flows through the multilayer conductive tape. Therefore, in the secondary batteries according to Examples 1 and 2, the current is not interrupted unless both the welded portion and the multilayer conductive tape are cut, so the tensile strength of Examples 1 and 2 can be considered as the tensile strength until both the welded portion and the multilayer conductive tape are cut. Therefore, the tensile strength of Examples 1 and 2 showed higher characteristics than the comparative example.

Claims

1. An electrode assembly comprising one or more electrodes and separators stacked alternately; a battery case in which the electrode assembly is housed; Electrode tabs extending from the electrodes and stacked and welded according to polarity; an electrode lead that is stacked and connected to the electrode tab and has a portion protruding outside the battery case; and A secondary battery including a multilayer conductive tape, The multilayer conductive tape comprises: Adhesive layer; an electrically conductive layer located on one side of the adhesive layer; an insulating layer disposed on one side of the electrically conductive layer; and a protective layer for protecting the outer surface of the insulating layer Including, the multi-layered conductive tape is attached to at least one of an upper side and a lower side in a stacking direction at a position where the electrode tab and the electrode lead are stacked and connected; Secondary battery.

2. 2. The secondary battery according to claim 1, wherein the electrically conductive layer comprises a metal, and the metal comprises at least one of copper, aluminum, titanium, silicon, magnesium, and stainless steel.

3. 2. The secondary battery according to claim 1, wherein the insulating layer is made of a material selected from the group consisting of polyethylene terephthalate, polyimide, polypropylene, polystyrene, polybutylene, polyethylene, and combinations thereof.

4. The secondary battery of claim 1 , further comprising a second insulating layer located on one side of the protective layer.

5. The secondary battery according to claim 1 , wherein the adhesive layer comprises a mesh-shaped substrate and an adhesive resin.

6. The secondary battery according to claim 5 , wherein at least one of the substrate and the resin contains an electrically conductive material.

7. The secondary battery of claim 1 , wherein the multilayer conductive tape covers at least a portion of an overlapping portion where the electrode tab and the electrode lead are connected to each other.

8. 8. The secondary battery of claim 7, wherein the multilayer conductive tape has a width (W) in a direction in which the electrode lead extends to the electrode tab, the width being greater than a width of a portion where the electrode tab and the electrode lead are connected and overlapped.

9. 2. The secondary battery according to claim 1, wherein the width (W) of the multilayer conductive tape extends in a width direction from ends of one surface and the other surface of the electrode assembly facing the battery case to at least a portion of an overlapping portion where the electrode tab and the electrode lead are connected.

10. The secondary battery according to claim 1 , wherein the multi-layered conductive tape seals contact surfaces of the electrode tabs and the electrode leads to the battery case.

11. the multi-layered conductive tape is attached to the upper and lower sides of the overlapping positions of the electrode tabs and the electrode leads in a direction perpendicular to the direction in which the electrode leads extend; 2. The secondary battery of claim 1, wherein the upper and lower multilayer conductive tapes located in a portion where the electrode tab and the electrode lead are not located in a direction perpendicular to a direction in which the electrode lead extends are adhered to each other and sealed.

12. manufacturing an electrode assembly by alternately stacking a plurality of electrodes and separators; a pre-welding step of gathering and welding electrode tabs provided at the ends of the plurality of electrodes; a main welding step of overlapping and welding an electrode lead to the end of the electrode tab; adhering a multi-layered conductive tape to at least one of an upper side and a lower side of a position where the electrode tab and the electrode lead overlap; and thermocompressing the adhesive surface of the multi-layered conductive tape by heat; A method for producing the secondary battery according to claim 1 , comprising:

13. The method of claim 12, wherein the thermocompression bonding step comprises thermocompressing the adhesive surfaces of the multilayered conductive tape at a temperature of 50° C. to 300° C. and a pressure of 0.2 MPa to 1.0 MPa.

14. 13. The method for manufacturing a secondary battery according to claim 12, wherein the multilayer conductive tape is attached to the upper and lower sides of a position where the electrode tab and the electrode lead overlap, and a portion where the multilayer conductive tapes attached to the upper and lower sides contact each other is sealed via the thermocompression bonding.

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