Electrode with excellent weldability between electrode lead and electrode tab and manufacturing method thereof

Abstract

The present invention relates to a battery including an electrode tab coated with an insulating layer, and more particularly to an electrode including an electrode tab coated with an insulating layer, which includes an electrode current collector (112) coated with an electrode active material (111), an electrode tab (120) protruding from the electrode current collector (112), and an insulating layer (150) coated on the electrode tab (120), wherein the other side of the electrode tab (120) coated with the insulating layer (150) is welded and joined to an electrode lead (130).

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2020-0144304 filed on November 2, 2020, and all contents disclosed in the documents of the corresponding Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode having excellent weldability between an electrode lead and an electrode tab, and a manufacturing method thereof, and more particularly, to an electrode including an insulating layer on an electrode tab, which can reduce the rate of welding defects between the electrode tab and the electrode lead and simplify the process, and a manufacturing method thereof. [Background technology]

[0003] Chargeable and dischargeable secondary batteries are drawing attention as a power source for devices that require high output and large capacity, including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (Plug-In HEVs), which have been presented as a solution to address air pollution caused by existing gasoline and diesel vehicles that use fossil fuels.

[0004] In such devices, medium to large size battery modules are used in which a number of battery cells are electrically connected to provide high power and large capacity.

[0005] Since it is preferable that medium- to large-sized battery modules are manufactured with the smallest possible size and weight, prismatic batteries, pouch-type batteries, etc., which can be stacked with a high degree of integration and have a small weight compared to their capacity, are mainly used as battery cells (unit batteries) for medium- to large-sized battery modules. Recently, pouch-type batteries, which have a structure in which stack-type or stack / folding-type electrodes are built into a pouch-type battery case made of an aluminum laminate sheet, have attracted much attention due to their low manufacturing costs, small weight, easy shape modification, etc., and their usage is gradually increasing.

[0006] One of the major research topics in such secondary batteries is to improve safety. In general, lithium secondary batteries may explode due to high temperature and high pressure inside the battery that may be induced by abnormal operating conditions of the battery, such as an internal short circuit, an overcharged state exceeding an allowable current and voltage, exposure to high temperature, impact due to dropping, etc. As one such case, there is a possibility that an internal short circuit may occur when the secondary battery is dropped or subjected to an impact due to an external force.

[0007] FIG. 1 shows a typical structure of a conventional pouch-type secondary battery including stacked electrodes.

[0008] Referring to FIG. 1, a conventional pouch-type secondary battery includes an electrode 10, electrode tabs 20, 21 extending from the electrode 10, electrode leads 30, 31 welded to the electrode tabs 20, 21, and a battery case that houses the electrode 10.

[0009] The electrode 10 may have positive and negative electrodes stacked in sequence with a separator interposed therebetween. Examples of the electrode 10 include a jelly roll (wound type) electrode having a structure in which long sheet-like positive and negative electrodes are wound up with a separator interposed therebetween, a stack type (laminated type) electrode having a structure in which a number of positive and negative electrodes cut into units of a predetermined size are stacked in sequence with a separator interposed therebetween, and a stack / folding type electrode having a structure in which a bi-cell or full cell in which a predetermined unit of positive and negative electrodes are stacked with a separator interposed therebetween is wound up.

[0010] Each electrode tab 20, 21 extends from each plate of the electrode 10. Each electrode lead 30, 31 is connected to the electrode tabs 20, 21 extending from each plate, and may be partially exposed to the outside of the battery case.

[0011] Each electrode lead 30, 31 is partially electrically connected to each electrode tab 20, 21. At this time, a joint w is formed by joining using a method such as welding, and the joining method may be a method such as general resistance welding, ultrasonic welding, laser welding, riveting, etc. Also, in order to increase the degree of sealing with the battery case and at the same time ensure electrical insulation, protective films 40, 41 may be included between the electrode lead and the battery case.

[0012] However, if the battery is dropped or a physical external force is applied to the upper end of the battery, causing the electrode tab to come into contact with the upper end of the electrode, a short circuit of the battery may be induced. In general, a short circuit may occur when the positive electrode tab comes into contact with the negative electrode current collector or the negative electrode active material.

[0013] FIG. 2 shows a front view and a side cross-sectional view of a conventional electrode tab-electrode lead combination with an insulating layer.

[0014] 2, short circuits can be prevented by providing an insulating layer 50 on a portion of the electrode tab 20 that is joined to the electrode lead 30. However, this method has problems such as a decrease in the joining strength between the electrode tab and the electrode lead due to an unevenly formed insulating layer, resulting in a defective rate of the electrode, a complicated joining process, and inability to completely prevent short circuits inside the battery due to defects in the insulating layer, and therefore, improvements are needed.

[0015] Patent Document 1 relates to a positive electrode including an insulating layer on a positive electrode tab, and is a method of coating a part of the positive electrode tab protruding from the positive electrode current collector with an insulating material to prevent cell deformation, internal short circuiting that may occur when stacking electrodes due to sharp edges of the electrodes when cut during the battery manufacturing process, or physical short circuiting between the positive and negative electrodes due to shrinkage from the separator in a high-temperature atmosphere.

[0016] Patent Document 2 relates to a secondary battery including a sealing member at a joint between an electrode tab and an electrode lead, specifically, an electrode having a laminated structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and an electrode lead electrically connected to each electrode tab of the electrode and drawn out to the outside of a battery case, the electrode tab and the electrode lead form a joint electrically connected to each other by ultrasonic welding, and the outer surface of the joint is covered with a heat-sealed sealing member. By using the sealing member, it is possible to improve the sealing force of the joint between the electrode tab and the electrode lead and prevent short circuits.

[0017] Patent Documents 1 and 2 disclose an insulating layer configuration that prevents short circuits, but the present invention does not disclose a configuration that simplifies the process of coating the electrode tab with an insulating layer and reduces the rate of welding defects between the electrode tab and the electrode lead. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] Republic of Korea Patent Publication No. 10-1586530 [Patent Document 2] Republic of Korea Patent Publication No. 10-1792605 Summary of the Invention [Problem to be solved by the invention]

[0019] The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrode and a manufacturing method thereof that can reduce the defect rate by providing excellent weldability between an electrode tab coated with an insulating layer and an electrode lead.

[0020] Another object of the present invention is to provide an electrode and a manufacturing method thereof that can form an insulating layer by a simple coating operation while still providing a sufficient insulating effect. [Means for solving the problem]

[0021] In order to solve the above problems, the electrode according to the present invention includes an electrode collector 112 coated with an electrode active material 111, an electrode tab 120 protruding from the electrode collector 112, and an insulating layer 150 coated on the electrode tab 120, and the other surface of the electrode tab 120 coated with the insulating layer 150 is welded and joined to an electrode lead 130.

[0022] In the electrode according to the present invention, the electrode tab 120 is a plain portion that does not include a layer of the electrode active material 111 .

[0023] In the electrode according to the present invention, the insulating layer 150 is coated over a part or the entire length of the electrode tab 120 in the protruding direction of the electrode tab 120 .

[0024] In the electrode according to the present invention, the insulating layer 150 is coated with a width equal to the width of the electrode tab 120 perpendicular to the protruding direction of the electrode tab 120.

[0025] In the electrode according to the present invention, the electrode tab 120 is characterized in that it partially includes a layer of the electrode active material 111 .

[0026] In addition, in the electrode according to the present invention, the insulating layer 150 covers a part or the whole of the electrode active material 111 and is coated over a part or the whole of the entire length of the electrode tab 120 in the protruding direction of the electrode tab 120.

[0027] In the electrode according to the present invention, the insulating layer 150 is coated with a width equal to the width of the electrode tab 120 perpendicular to the protruding direction of the electrode tab 120.

[0028] The present invention is also characterized in that it is a secondary battery including the electrode.

[0029] In the present invention, the secondary battery is characterized in that it is of a cylindrical type, a square type or a pouch type.

[0030] The present invention can provide a method for manufacturing an electrode, comprising: a first step of coating an insulating layer on a first side surface of an electrode tab formed to protrude from an electrode current collector; and a second step of welding an electrode lead to another side facing the first side surface of the electrode tab coated with the insulating layer.

[0031] In the method for manufacturing an electrode according to the present invention, in the first step, the insulating layer may be coated over the entire first side of the electrode tab.

[0032] In addition, in the method of manufacturing an electrode according to the present invention, the first step may further include coating the insulating layer on a pair of second and third sides of the electrode tab.

[0033] The present invention can be implemented by selecting and combining one or more of the above-described configurations that are not contradictory to each other. Effect of the Invention

[0034] According to the electrode and manufacturing method thereof of the present invention, the other surface of the electrode tab coated with an insulating layer is welded to the electrode lead. Therefore, the surface of the electrode tab to be welded does not include an insulating layer, which improves weldability with the electrode lead and reduces the rate of welding defects.

[0035] In addition, according to the electrode and manufacturing method thereof of the present invention, since the surface other than the surface of the electrode tab to which the electrode lead is welded is coated with an insulating layer, there is an advantage that the coating process and the welding process are simplified.

[0036] In addition, according to the electrode and the manufacturing method thereof of the present invention, the electrode having an insulating layer on one surface has an advantage that the manufacturing process of the electrode can be significantly shortened, ultimately reducing the manufacturing cost. [Brief description of the drawings]

[0037] [Figure 1] FIG. 1 is a schematic diagram of a secondary battery according to the prior art. [Diagram 2] 1A and 1B are front and side cross-sectional views of an electrode tab-electrode lead combination with an insulating layer according to the prior art; [Diagram 3] 1 is a perspective view of an electrode with protruding electrode tabs according to a first preferred embodiment of the present invention; [Figure 4] 1A and 1B are a front view and a side cross-sectional view of an electrode tab-electrode lead combination including an insulating layer according to a first preferred embodiment of the present invention; [Diagram 5] 4A and 4B are a front view and a side cross-sectional view of an electrode tab-electrode lead combination including an insulating layer according to a second preferred embodiment of the present invention; [Figure 6] 13A and 13B are a front view and a side cross-sectional view of an electrode tab-electrode lead combination including an insulating layer according to a third preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, in which a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, if it is determined that the detailed description of related well-known functions or configurations may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0039] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when one part is said to be connected to another part, this includes not only a direct connection but also an indirect connection via another element between them. In addition, the inclusion of one component does not mean the exclusion of other components, but may further include other components, unless otherwise specified.

[0040] Furthermore, descriptions that specify or limit components by adding them are applicable to all inventions unless otherwise specified, and are not limited to a particular invention.

[0041] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0042] Furthermore, throughout the description of the present invention and the claims, unless otherwise stated, "or" includes "and." Therefore, "including A or B" means all three cases including A, including B, or including A and B.

[0043] Hereinafter, a battery according to the present invention will be described with reference to the accompanying drawings.

[0044] FIG. 3 is a perspective view of an electrode having a protruding electrode tab according to a first preferred embodiment of the present invention, and FIG. 4 is a front view and a side cross-sectional view of an electrode tab-electrode lead combination including an insulating layer according to a first preferred embodiment of the present invention.

[0045] The electrode according to the first embodiment of the present invention will be described with reference to FIGS. 3 and 4. The electrode 110 includes an electrode current collector 112 and an electrode active material 111, an electrode tab 120 protruding from one end of the electrode current collector 112, an insulating layer 150 included in the electrode tab 120, and an electrode lead 130 welded and connected to the electrode tab 120.

[0046] First, to specifically describe the electrode 110, the electrode 110 can be a positive electrode or a negative electrode.

[0047] The positive electrode may be formed by applying an electrode active material 111, which is a coated positive electrode active material, to one or both sides of an electrode current collector 112, which is a positive electrode current collector.

[0048] Here, the positive electrode current collector can be manufactured to a thickness of 3 μm to 500 μm.

[0049] Further, the positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, as the positive electrode current collector, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0050] The current collector can also enhance the adhesive force of the positive electrode active material by forming fine irregularities on its surface. As the current collector, various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabric bodies, etc. are possible.

[0051] Further, the positive electrode active material may be any one selected from lithium-containing transition metal oxides and their equivalents. More specifically, for example, the positive electrode active material can include manganese-based spinel active materials, lithium metal oxides, or mixtures thereof. Further, the lithium metal oxide may be selected from the group consisting of lithium-manganese-based oxides, lithium-nickel-manganese-based oxides, lithium-manganese-cobalt-based oxides, and lithium-nickel-manganese-cobalt-based oxides. More specifically, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(Ni a Co b Mn c )O2 (where 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), LiNi 1-Y Co Y O2, LiCo 1-Y Mn Y O2, LiNi 1-Y Mn Y O2 (where 0 ≤ Y < 1), Li(Ni a Co b Mn c )O4 (0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-z Ni z O4, LiMn 2-z Co z O4 (where 0 < Z < 2) can be used.

[0052] In addition, the negative electrode current collector can be manufactured with a thickness of 3 μm to 500 μm. The negative electrode current collector is not particularly limited as long as it does not induce a chemical change in the battery and has conductivity. For example, as the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, those obtained by surface treatment of the surface of copper or stainless steel with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. Further, similar to the positive electrode current collector, the negative electrode current collector can also strengthen the binding force of the negative electrode active material by forming fine irregularities on the surface, and can be used in various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven bodies, etc.

[0053] Examples of the negative electrode material include carbon such as graphitizable carbon and graphite-based carbon; Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials, etc. can be used.

[0054] Next, the electrode tab 120 will be described. The electrode tab 120 can be formed by protruding and extending from the electrode current collector 112.

[0055] In addition, in the present invention, the electrode tab 120 can be formed by notching a continuous electrode sheet in which the electrode active material 111 is coated on one or both surfaces of the electrode current collector 112 at the interval of unit electrodes with a mold frame.

[0056] Therefore, the electrode tab 120 extends from one side of the electrode collector 112 and includes a pair of opposing first side surfaces 121 corresponding to the surface in the width direction (X-axis direction), a pair of opposing second side surfaces 122 corresponding to the surface in the thickness direction (Y-axis direction), and a third side surface 123 facing the electrode collector 112.

[0057] Here, the electrode tab 120 is a plain portion on which the electrode active material 111 is not applied, and includes an insulating layer 150 formed by coating an insulating material on one side of a pair of first sides 121, and the opposite first side 121 on which the insulating layer 150 is not formed is coupled to the electrode lead 130.

[0058] Meanwhile, the insulating layer 150 is formed by coating an insulating material on the first side surface 121 of the electrode tab 120 in a protruding direction (Z-axis direction) from the electrode current collector 112, and may be formed over a part or the entire length (Z-axis direction) of the first side surface 121. When coating the first side surface 121 of the electrode tab 120 with an insulating material, since there are no strict restrictions on the coating area, the coating operation of the insulating material may be simple and easy.

[0059] In addition, it is preferable that the insulating layer 150 is coated with a width equal to the width (X-axis direction) of the electrode tab 120 perpendicular to the protruding direction of the electrode tab 120. Since the electrode active material 111 is formed on the electrode collector 112 from which the electrode tab 120 protrudes, the insulating material is coated over the entire width of the first side surface 121 of the electrode tab 120 extending from the electrode collector 112, which is advantageous in preventing a short circuit induced by the electrode active material 111.

[0060] Here, the method of coating the insulating material may be a dipping method, a deep coating method, a spray coating method, a spin coating method, a roll coating method, a die coating method, a roll coat method, a gravure printing method, a bar coat method, etc., but is not limited to these.

[0061] Examples of insulating materials include polyethylene, polypropylene, polyetherimide, polyacetal, polysulfone, polyetheretherketone, polyester, polyamide, ethylene-vinyl acetate copolymer, polystyrene, polytetrafluoroethylene, polysiloxane, polyimide, any copolymer thereof, any mixture thereof, etc., among which polyimide having excellent electrical insulation and heat resistance is particularly preferable. However, the insulating material is not limited to the above examples as long as it has electrical insulation properties and does not affect the electrochemical reaction of the battery.

[0062] In some cases, inorganic substances may be further added to the polymer resin within a range that does not impair the effects of the present invention. Examples of such inorganic substances include SiO2, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, Y2O3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y TiyO3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), BaTiO3, hafnia(H f O2), SrTiO3, and mixtures of two or more thereof.

[0063] In the present invention, the electrode lead 130 is not particularly limited as long as it is made of a material capable of electrically connecting the electrode tabs 120, and may be preferably a metal plate. Examples of such metal plates include, but are not limited to, a nickel plate, a nickel-plated copper plate, an aluminum plate, a copper plate, and a SUS plate.

[0064] In the present invention, the electrode tab 120 and the electrode lead 130 can be joined by welding and are electrically connected to each other by ultrasonic welding. Such joining by ultrasonic welding is performed by applying high frequency vibrations generated by high ultrasonic waves of about 20KHz, and the vibration energy is converted into heat energy by friction due to the operation of a horn and anvil at the interface between the electrode tab and the electrode lead, thereby rapidly welding the electrode tab and the electrode lead.

[0065] The manufacturing method of the electrode according to the first embodiment of the present invention having the above-mentioned configuration may include a step of forming an insulating layer 150 by coating an insulating material on a first side of the electrode tab 120 protruding from the electrode collector 112, and a step of welding an electrode lead 130 to the other side opposite to the first side of the electrode tab 120 on which the insulating layer 150 is formed.

[0066] Here, in the coating step for forming the insulating layer, the insulating layer may be coated on a part or the entirety of the first side of the electrode tab 120 .

[0067] FIG. 5 is a front view and a side cross-sectional view of an electrode tab-electrode lead combination including an insulating layer according to a second preferred embodiment of the present invention.

[0068] The second embodiment of the present invention is the same as the first embodiment described with reference to FIGS. 3 and 4, except that one side of the electrode tab 220 includes a portion of the electrode active material 211. Therefore, hereinafter, only the electrode active material 211 included in the electrode tab 220 will be described.

[0069] 5, an electrode active material may be formed on one surface of an electrode tab 220 in a direction protruding from one end of an electrode collector 212 of the electrode according to the second embodiment of the present invention. The electrode active material formed on the electrode tab 220 may be an extension of the electrode active material 211 formed on the electrode collector 212 onto the electrode tab 220.

[0070] Here, the insulating layer 250 covers all or part of the electrode active material formed on the electrode tab 220, and may be coated in the protruding direction (Z-axis direction) of the electrode tab 220. Also, the insulating layer 250 is preferably coated with the same width (X-axis direction) as the width of the electrode tab 220. This is advantageous in preventing a short circuit caused by the electrode active material coming into contact with other members. Also, it is advantageous in delaying the progression of a short circuit when the separator shrinks at high temperatures.

[0071] The method for manufacturing an electrode according to the second embodiment of the present invention is the same as the method for manufacturing an electrode according to the first embodiment described above, except that an electrode active material is formed on the electrode tab 220, so a detailed description thereof will be omitted.

[0072] FIG. 6 is a front view and a side cross-sectional view of an electrode tab-electrode lead combination including an insulating layer according to a third preferred embodiment of the present invention.

[0073] The third embodiment of the present invention is the same as the first embodiment described with reference to FIGS. 3 and 4, except that an insulating layer 350 is further formed by coating on the second and third sides of the electrode tab 320. Therefore, hereinafter, only the insulating layer 350 formed by coating on the second and third sides of the electrode tab 320 will be described.

[0074] In the third embodiment of the present invention, the insulating layer 350 may be coated on a pair of second and third sides as well as one first side of the electrode tab 320, or may be coated on a part or the entirety of the four sides. The insulating layer 350 may be coated in the protruding direction (Z-axis direction) of the electrode tab 320, and is preferably coated with the same width (X-axis direction) as the width of the electrode tab 320.

[0075] Of the five sides of the electrode tab 320 extending and protruding from the electrode collector 312, an insulating layer is formed on the remaining four sides excluding the side that is welded to the electrode lead 330, which is advantageous in preventing short circuits caused by corrosion of the electrode tab 320.

[0076] The method for manufacturing an electrode according to the third embodiment of the present invention is the same as the method for manufacturing an electrode according to the first embodiment described above, except that an insulating layer is coated on a pair of second and third sides in addition to the first side of the electrode tab 320, and therefore a detailed description thereof will be omitted.

[0077] The present invention can provide a secondary battery including the above-mentioned electrode. In general, in a lithium secondary battery, the negative electrode is made larger than the positive electrode in consideration of the problem of lithium ions being precipitated on the negative electrode during charging and discharging. Therefore, when an external impact is received due to dropping, the positive electrode tab is likely to come into preferential contact with the negative electrode (current collector or active material) of the power generating element. Therefore, when the positive electrode is smaller than the negative electrode, it is preferable to coat the positive electrode tab with an insulating layer. Alternatively, when the positive electrode and the negative electrode are the same size, the insulating layer can be coated on both the positive electrode tab and the negative electrode tab. EXAMPLES

[0078] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited thereto.

[0079] Example 1 LiNi as the positive electrode active material 0.8 Mn0.1 Co 0.1 A positive electrode active material slurry was prepared by adding NMP as a solvent to a mixture of O2, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of positive electrode active material:conductive material:binder of 96:2:2.

[0080] 4.01mAh / cm per side of 30μm thick aluminum current collector 2 The positive electrode active material slurry was applied in a loading amount of 1000g, and then dried and rolled to obtain a positive electrode.

[0081] The above-mentioned positive electrode was punched out to a size of 40 mm x 55 mm so that the electrode active material layer did not reach a part of the tab, and a PVdF solution (NMP solution, solid content 7%) was applied with a brush to the plain area on the front side of the tab, and after drying at 80°C, the rear side of the electrode tab and the electrode lead were welded (20Khz, 0.5 sec ultrasonic welding).

[0082] Example 2 The positive electrode was punched out to a size of 40 mm x 55 mm so that the electrode active material layer reached a part of the tab, and the PVdF solution was painted with a brush on the uncoated area on the front side of the tab and the area where the active material reached, except for the same procedure as in Example 1.

[0083] Example 3 Same as Example 1 except the PVdF solution was applied with a brush to the plain areas on the front of the tab and to the sides of the tab.

[0084] Comparative Example 1 This is the same as Example 1, except that the rear welding of the tab is not performed, and the PVdF solution is painted with a brush onto the front surface of the tab, dried, and then the front welding is performed thereon.

[0085] Comparative Example 2 This is the same as Example 1, except that the rear welding of the tab is not performed, and the PVdF solution is applied with a brush to an area of ​​3 / 4 or more of the tab, dried, and then the front welding is performed on it.

[0086] Welding performance evaluation The welding operations for each of Examples 1 to 3 and Comparative Examples 1 and 2 were carried out 10 times, and the number of welding failures was summarized in the table below.

[0087] In the present invention, failure in welding between the electrode tab and the electrode lead can be confirmed by the following method.

[0088] (1) A failure is when the electrode tab and the electrode lead are not welded at all and the detachment of the electrode tab and the electrode lead is visible to the naked eye.

[0089] (2) In the case where the electrode tab and the electrode lead are partially welded and it is difficult to confirm the welding defect with the naked eye, when the electrode tab and the electrode lead are detached from each other when struck 1 to 10 times with a striking part made of elastic material, it can be regarded as a failure.

[0090] (3) In addition, when the electrode tab and electrode lead are partially welded and it is difficult to confirm the weld defect with the naked eye, the presence or absence of the weld failure is confirmed by measuring the resistance of the weld. Here, when the electrode tab and electrode lead are welded under the same welding conditions, if the measured resistance value is 10% or more higher than the resistance value of the welded part that was successfully welded, it can be regarded as a weld failure.

[0091] [Table 1]

[0092] Although certain parts of the present invention have been described in detail above, it will be apparent to a person skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the present invention. It is possible to make various changes and modifications within the scope of the present invention and the technical spirit of the present invention. It is natural that such changes and modifications fall within the scope of the appended claims. [Explanation of symbols]

[0093] 10, 110, 210, 310 electrodes 11, 111, 211, 311 Electrode active material 12, 112, 212, 312 Electrode current collector 20, 120, 220, 320 Electrode tab 121 1st side, 122 2nd side, 123 3rd side 30, 130, 230, 330 Electrode Leads 40, 140, 240, 340 Protective Film 50, 150, 250, 350 Insulation layer w Joint

Claims

1. An electrode to be welded to an electrode lead, the electrode comprising: One electrode current collector coated with an electrode active material; and an electrode tab protruding from the electrode current collector; the electrode tab includes one surface and another surface facing the one surface, an insulating layer is coated on the one surface of the electrode tab; the other surface of the electrode tab is not coated with an insulating layer; an electrode having an electrode lead welded to the other surface of the electrode tab;

2. The electrode of claim 1 , wherein the electrode tab is a plain area that does not include a layer of the electrode active material.

3. The electrode of claim 2 , wherein the insulating layer is coated over a portion or the entire length of the electrode tab in a protruding direction of the electrode tab.

4. The electrode according to claim 2 or 3, wherein the insulating layer is coated with a width equal to a width of the electrode tab perpendicular to a protruding direction of the electrode tab.

5. The electrode of claim 1 , wherein the electrode tab comprises a portion of the layer of electrode active material.

6. The electrode of claim 5 , wherein the insulating layer covers a portion or all of the electrode active material and is coated over a portion or all of the entire length of the electrode tab in a protruding direction of the electrode tab.

7. The electrode according to claim 5 or 6, wherein the insulating layer is coated with a width equal to the width of the electrode tab perpendicular to a protruding direction of the electrode tab.

8. A secondary battery comprising the electrode of any one of claims 1 to 7.

9. The secondary battery according to claim 8 , wherein the secondary battery is of a cylindrical type, a rectangular type or a pouch type.

10. A first step of coating an insulating layer on one surface of an electrode tab formed protruding from an electrode current collector; and a second step of welding an electrode lead to the other surface of the electrode tab opposite to the surface of the electrode tab coated with the insulating layer, The electrode is One electrode current collector coated with an electrode active material; and the electrode tab protruding from the electrode current collector; an insulating layer is coated on the one surface of the electrode tab; the other surface of the electrode tab is not coated with an insulating layer; the electrode lead is welded to the other surface of the electrode tab.

11. The method of claim 10 , wherein in the first step, the insulating layer is coated on the entire surface of the electrode tab.

12. The method of claim 10 or 11, further comprising coating the insulating layer on a pair of second and third sides of the electrode tab in the first step.

Images