Electrodes and electrode assemblies

Abstract

To solve the problem, an electrode according to one embodiment of the present invention includes: an active material coating portion, which is coated with an electrode active material on at least one surface of an electrode current collector; and an active material uncoated portion, which is formed on one side of the active material coating portion, is not coated with the electrode active material, and includes at least one slit extending from one end thereof to the other end, wherein a hole is formed through a point where the slit and the active material coating portion are connected to each other.

Description

Technical Field

[0001] The present invention relates to an electrode and an electrode assembly, and more particularly, to an electrode that is prevented from being bent or warped after a rolling process is completed, and to an electrode assembly. Background Art

[0002] Generally speaking, secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. Such secondary batteries are used in small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, electric bicycles, and large products such as electric vehicles and hybrid vehicles that require high power, storage devices for storing surplus power or renewable energy, and backup storage devices.

[0003] In order to manufacture an electrode assembly, a cathode (hereinafter referred to as a positive electrode), a separator and an anode (hereinafter referred to as a negative electrode) are manufactured and stacked. Specifically, a positive electrode active material slurry is applied to a positive electrode current collector, and a negative electrode active material slurry is applied to a negative electrode current collector to manufacture a positive electrode and a negative electrode. In addition, when a separator is interposed and stacked between the manufactured positive electrode and the manufactured negative electrode, a unit cell is formed. The unit cells are stacked on each other to form an electrode assembly. In addition, when the electrode assembly is housed in a specific housing and an electrolyte is injected, a secondary battery is manufactured.

[0004] The process of manufacturing secondary batteries is generally divided into three steps, such as electrode process, assembly process and forming process. In addition, the electrode process is further divided into active material mixing process, electrode coating process, rolling process, slitting process and winding process. Among them, the rolling process is to pass the electrode sheet between two rolling rollers heated at high temperature, so as to compress the electrode sheet to the required thickness and density, so as to increase the capacity density by reducing the thickness of the electrode sheet (on which the coating process of the electrode mixture is completed), and improve the adhesion and adhesion between the electrode current collector and the electrode active material contained in the electrode mixture.

[0005] Figure 1 is a schematic diagram of an electrode 100 according to the prior art, and Figure 2 is a schematic diagram showing a rolling state of an electrode 100 according to the prior art.

[0006] like Figure 1 As shown in FIG. 1 , such as the positive electrode 101 (see Figure 3 ) and the negative electrode 102 (see Figure 3) includes: an active material coated portion 1003 coated with an electrode active material 1002; and an active material uncoated portion 1004 uncoated with the electrode active material 1002. The active material coated portion 1003 is a region that directly generates electricity and occupies a large area of ​​the electrode 100. In addition, the active material uncoated portion 1004 is directly cut or connected to a separate conductive member to form an electrode tab 11.

[0007] According to the prior art, when the electrode sheet passes between two rolling rollers 2 in the rolling process, Figure 2 As shown in FIG. 1 , the active material coated portion 1003 is relatively thick and receives more heat and pressure, while the active material uncoated portion 1004 is relatively thin and receives less heat and pressure. Therefore, due to the difference in heat and pressure, there is a problem in that the electrode 100 is bent or warped after the rolling process is completed. In particular, in recent years, due to the need for batteries with high energy density, the filling amount of the electrode active material 1002 has increased, and this problem occurs more.

[0008] [Prior art document] (Patent document 1) Japanese Patent Publication No. 2014-022116 Summary of the invention

[0009] Technical issues

[0010] An object of the present invention to solve the above problems is to provide an electrode and an electrode assembly, the electrode being able to prevent bending or warping after a rolling process is completed.

[0011] The objects of the present invention are not limited to the above objects, and those skilled in the art will clearly understand other objects not described herein from the following description.

[0012] Technical Solution

[0013] An electrode according to one embodiment of the present invention for solving the above problems includes: an active material coating portion, wherein the active material coating portion is coated with an electrode active material on at least one surface of an electrode current collector; and an active material uncoated portion, wherein the active material uncoated portion is formed on one side of the active material coating portion, is not coated with the electrode active material, and includes at least one slit extending from one end thereof to the other end, wherein a hole is formed through a point where the slit and the active material coating portion meet each other.

[0014] Additionally, the slit may have a linear shape.

[0015] In addition, the slit may have an inclination with respect to a boundary between the active material uncoated portion and the active material coated portion.

[0016] Additionally, the slit may have a curved shape.

[0017] In addition, the slit may have a curved shape with a constant curvature.

[0018] Additionally, the slit may have a curved shape having a plurality of centers of curvature.

[0019] Additionally, the slit may have a wavy shape.

[0020] Additionally, the width of the slit may vary regularly or irregularly from one end to the other.

[0021] In addition, the hole may have at least one of a circular shape, an elliptical shape, and a polygonal shape.

[0022] In addition, the slit may be provided in plurality, and a hole may be formed in one end of each of the plurality of slits.

[0023] Furthermore, the holes may have shapes that are different from each other.

[0024] In an electrode assembly (in which electrodes and separators are alternately stacked) according to one embodiment of the present invention for solving the above problems, each of the electrodes includes: an active material coating portion, wherein the active material coating portion is coated with an electrode active material on at least one surface of an electrode current collector; and an active material uncoated portion, wherein the active material uncoated portion is formed on one side of the active material coating portion, is not coated with the electrode active material, and includes at least one slit extending from one end thereof to the other end, wherein a hole is formed through a point where the slit and the active material coating portion are connected to each other.

[0025] In addition, the slit formed in the positive electrode of the electrode and the slit formed in the negative electrode of the electrode may have shapes different from each other.

[0026] In addition, the pores formed in the positive electrode of the electrode and the pores formed in the negative electrode of the electrode may have shapes different from each other.

[0027] Details of other implementations are included in the detailed description and illustrations.

[0028] Beneficial Effects

[0029] According to the embodiments of the present invention, there are at least the following effects.

[0030] Since the slits are formed in the active material uncoated portion of the electrode, the electrode can be prevented from being bent or warped even after the rolling process is completed.

[0031] In particular, depending on the degree of warping of the electrode (which varies depending on the size and type of the electrode and the applied heat and pressure), a slit having an appropriate shape can be formed to more effectively prevent the electrode from bending or warping.

[0032] Furthermore, since the hole is formed through the point where the slit and the active material coating portion meet each other, stress concentrated to one end of the slit can be dispersed to prevent cracks from occurring toward the active material coating portion.

[0033] In particular, pores having an appropriate shape according to stress distribution (causing cracks that vary depending on the size and kind of the electrode and applied heat and pressure) can be formed to more effectively prevent cracks from occurring toward the active material coating portion.

[0034] The effects of the present invention are not limited to the foregoing description, and thus more various effects are involved in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of an electrode according to the prior art.

[0036] Figure 2 is a schematic diagram showing a rolling state of an electrode according to the prior art.

[0037] Figure 3 is a schematic diagram of an electrode assembly according to a first embodiment of the present invention.

[0038] Figure 4 is an assembly diagram of a pouch type secondary battery according to a first embodiment of the present invention.

[0039] Figure 5 is a schematic diagram of an electrode according to a first embodiment of the present invention.

[0040] Figure 6 is a schematic diagram of an electrode according to a second embodiment of the present invention.

[0041] Figure 7 is a schematic diagram of an electrode according to a third embodiment of the present invention.

[0042] Figure 8 is a schematic diagram of an electrode according to a fourth embodiment of the present invention.

[0043] Fig. 9 is a schematic diagram of an electrode according to a fifth embodiment of the present invention.

[0044] Fig.10 is a schematic diagram of an electrode according to a sixth embodiment of the present invention.

[0045] Fig.11 is a schematic diagram of an electrode according to a seventh embodiment of the present invention.

[0046] Fig.12 is a schematic diagram of an electrode according to an eighth embodiment of the present invention.

[0047] Fig.13 is a schematic diagram of an electrode according to a ninth embodiment of the present invention.

[0048] Fig.14 is a schematic diagram of an electrode according to a tenth embodiment of the present invention. DETAILED DESCRIPTION

[0049] The advantages and features of the present invention and its implementation method will be explained by the following embodiments described with reference to the accompanying drawings. However, the present invention can be implemented in different forms and should not be understood as being limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art. In addition, the present invention is limited only by the scope of the claims. Similar reference numerals refer to all similar elements.

[0050] Unless the terms used in the present invention are defined differently, all terms (including technical and scientific terms) used herein have the same meanings as generally understood by those skilled in the art. In addition, unless clearly and unambiguously defined in the description, the terms defined in the commonly used dictionaries are not ideally or excessively interpreted as having a formal meaning.

[0051] In the following description, technical terms are only used to explain specific exemplary embodiments and do not limit the present invention. In this specification, unless otherwise mentioned, terms in the singular may include plural forms. The meaning of "include" and / or "comprising" does not exclude other components other than the mentioned components.

[0052] Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings.

[0053] Figure 3 is a schematic diagram of an electrode assembly 10 according to a first embodiment of the present invention.

[0054] In order to manufacture the electrode assembly 10 according to the first embodiment of the present invention, first, a slurry mixed with a positive electrode active material 1012, a binder and a plasticizer is applied to a positive electrode current collector 1011 in the form of a metal foil or a metal mesh containing aluminum, and then dried and pressed to manufacture a positive electrode 101 (ie, a cathode). In addition, a slurry mixed with a negative electrode active material 1022, a binder and a plasticizer is applied to a negative electrode current collector 1021 in the form of a metal foil or a metal mesh containing copper, and then dried and pressed to manufacture a negative electrode 102 (ie, anode). The slurry can generally be formed by stirring a granular active material, an auxiliary conductor, a binder and a plasticizer in a state where a solvent is added. At this time, if necessary, the slurry may further include a filler. In addition, the solvent may be removed in a subsequent process. Each of the positive electrode 101 and the negative electrode 102 can be manufactured in a sheet form and then mounted on a roll.

[0055] The electrode assembly 10 is formed by alternately stacking electrodes 100 and separators 103. In particular, a stacking structure may be provided in which a separator 103 is inserted between the electrodes 100 or is arranged on the left or right side of any one electrode 100 so as to insulate two types of electrodes 100 manufactured as a positive electrode 101 and a negative electrode 102 from each other. In this stacking structure, a positive electrode 101 and a negative electrode 102, both having a predetermined standard, may be stacked with a separator 103 sandwiched therebetween, or may be wound in a jelly roll form. Alternatively, when a separator 103 is inserted between the manufactured positive electrode 101 and the manufactured negative electrode 102 for stacking, a unit cell may be formed. Then, the unit cells may be stacked on each other to form a structure such as Figure 3 The electrode assembly 10 shown in FIG.

[0056] The cathode current collector 1011 generally has a thickness of 3 μm to 500 μm. The positive electrode current collector 1011 is generally made of a material having high conductivity without causing chemical changes. Such a material may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. on its surface, but is not limited thereto. In addition, the positive electrode current collector 1011 may be formed with fine unevenness on its surface to enhance the bonding of the positive electrode active material 1012. In addition, the positive electrode current collector 1011 may have various shapes, such as a film, a sheet, a foil, a mesh, a porous body, a foam or a non-woven fabric.

[0057] In the case of a lithium secondary battery, the positive electrode active material 1012 may include, for example, a layered compound of lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted by one or more transition metals; a lithium manganese oxide such as Li 1+x Mn 2-xO4 (x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxide, such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, etc.; 1-x M x Ni-site lithium nickel oxide represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 to 0.3); represented by the chemical formula LiMn 2-x M x Lithium manganese composite oxide represented by LiMn2O4 (M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which part of Li is replaced by alkaline earth ions; disulfide; Fe2(MoO4)3, etc. However, the present embodiment is not limited thereto.

[0058] The conductive agent is generally added at 1% to about 50% (by weight) based on the total weight of the mixture including the cathode active material 1012. The conductive agent is generally made of a material having conductivity without causing chemical changes. The conductive agent may include, for example, conductive materials such as graphite such as natural graphite and artificial graphite, carbon black (such as acetylene black, ketjen black, furnace black, channel black, lamp black, and thermal black); conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; or polyphenylene derivatives.

[0059] The binder is a component that assists the active material to be bonded to the conductive material and to the current collector, and is generally added at 1 wt % to 50 wt % based on the total weight of the mixture containing the cathode active material 1012. Examples of the binder may include polyvinyl fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, and the like.

[0060] The filler may be used as a component to suppress the expansion of the positive electrode 101. In addition, if the general filler is a fiber material that does not cause chemical changes, the filler may be used. Examples of the filler may include olefin polymers such as polyethylene and polypropylene; and fiber materials such as glass fiber and carbon fiber.

[0061] The anode current collector 1021 generally has a thickness of 3 μm to 500 μm. The anode current collector 1021 is usually made of a material that has electrical conductivity and does not cause chemical changes. Examples of such materials include: copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. on its surface, or an aluminum cadmium alloy. In addition, the negative electrode current collector 1021 may form fine irregularities on its surface to increase the adhesion force of the negative electrode active material 1022. Additionally, the negative electrode current collector 1021 may have various shapes, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0062] The negative electrode active material 1022 may include, for example: carbon, such as non-graphitized carbon, graphite-based carbon, etc.; metal complex oxides, such as 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, elements of Group 1, Group 2, and Group 3 in the periodic table, halogens; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc.; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides, such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, etc.; conductive polymers, such as polyacetylene, etc.; lithium cobalt nickel-based materials, etc.

[0063] Generally known polyolefin separators or composite separators with an organic or inorganic composite layer formed on an olefin-based material can be used as the separator, which insulates the electrode 100 between the positive electrode 101 and the negative electrode 102, but is not particularly limited thereto.

[0064] According to the first embodiment of the present invention, the electrode assembly 10 having the above structure is accommodated in the battery case 13, and then, an electrolyte is injected to manufacture the secondary battery 1.

[0065] Figure 4 is an assembly diagram of the pouch-type secondary battery 1 according to the first embodiment of the present invention.

[0066] As Figure 4 shown, the pouch-type secondary battery 1 according to the first embodiment of the present invention includes: an electrode assembly 10 in which electrodes 100 (such as a positive electrode 101 and a negative electrode 102) and a separator 103 are laminated; and a pouch-type battery case 13 that houses the electrode assembly 10 therein.

[0067] To manufacture the pouch type secondary battery 1, the manufactured electrodes 100 are stacked on both sides of the separator 103 to manufacture the electrode assembly 10 having a predetermined shape. Then, the electrode assembly 10 is inserted into the battery case 13, and the battery case 13 is sealed after injecting an electrolyte therein.

[0068] like Figure 4 As shown in , the electrode assembly 10 includes an electrode tab 11. The electrode tab 11 is respectively connected to the positive electrode 101 and the negative electrode 102 of the electrode assembly 10 to protrude to the outside of the electrode assembly 10, thereby providing a path for electrons to move between the inside and the outside of the electrode assembly 10. The electrode current collector 1001 of the electrode assembly 10 includes an active material coated portion 1003 coated with an electrode active material 1002 and an active material uncoated portion 1004 uncoated with the electrode active material 1002. In addition, the electrode tab 11 can be formed by cutting the uncoated portion or connecting a separate conductive member to the uncoated portion by ultrasonic welding. As shown in FIG. Figure 4 As shown in FIG. 1 , the electrode tabs 11 may protrude from one side of the electrode assembly 10 in the same direction, but the present invention is not limited thereto. For example, the electrode tabs 11 may protrude in different directions from each other.

[0069] In the electrode assembly 10, the electrode lead 12 that supplies power to the outside of the secondary battery 1 is connected to the electrode tab 11 by spot welding. In addition, a portion of the electrode lead 12 is surrounded by an insulating portion 14. The insulating portion 14 may be arranged to be confined within a sealing portion 134, where the upper shell 131 and the lower shell 132 of the battery case 13 are thermally melted, so that the electrode lead 12 is bonded to the battery case 13. In addition, the power generated from the electrode assembly 10 can be prevented from flowing to the battery case 13 via the electrode lead 12, and the sealing of the battery case 13 can be maintained. Therefore, the insulating portion 14 may be made of a non-conductor having non-conductivity, which is non-conductive. In general, although an insulating tape that is easily attached to the electrode lead 12 and has a relatively thin thickness is mainly used as the insulating portion 14, the present invention is not limited thereto. For example, various components can be used as the insulating portion 14, as long as these components can insulate the electrode lead 12.

[0070] The electrode lead 12 includes: a positive electrode lead 121, one end of which is connected to the positive electrode connector 111 and extends along the protruding direction of the positive electrode connector 111; and a negative electrode lead 122, one end of which is connected to the negative electrode connector 112 and extends along the protruding direction of the negative electrode connector 112. Figure 4As shown in , the other ends of the positive electrode lead 121 and the negative electrode lead 122 are both protruded to the outside of the battery case 13. Therefore, the power generated in the electrode assembly 10 can be supplied to the outside. In addition, since each of the positive electrode tab 111 and the negative electrode tab 112 is formed to protrude in different directions, each of the positive electrode lead 121 and the negative electrode lead 122 can extend in different directions.

[0071] The positive electrode lead 121 and the negative electrode lead 122 may be made of different materials from each other. That is, the positive electrode lead 121 may be made of the same material as the positive electrode collector 1011 (ie, aluminum (Al) material), and the negative electrode lead 122 may be made of the same material as the negative electrode collector 1021 (ie, copper (Cu) material or copper material coated with nickel (Ni)). In addition, the portion of the electrode lead 12 protruding to the outside of the battery case 13 may be provided as a terminal portion and electrically connected to an external terminal.

[0072] The battery case 13 is a bag-shaped member made of a tough material, which accommodates the electrode assembly 10 therein. Hereinafter, the case where the battery case 13 is a bag-shaped member will be described. When a bag-shaped film 135 having toughness is drawn by using a punching machine or the like, a portion of the bag-shaped film 135 is stretched to form a cup-shaped portion 133 including a bag-shaped accommodation space 1331, thereby manufacturing the battery case 13. The battery case 13 accommodates the electrode assembly 10 so that a portion of the electrode lead 12 (i.e., the terminal portion) is exposed, and then is sealed. Figure 4 As shown in , the battery case 13 includes an upper case 131 and a lower case 132. A receiving space 1331 may be provided in the lower case 132, in which a cup-shaped portion 133 is formed to receive the electrode assembly 10, and the upper case 131 may cover the upper side of the receiving space 1331 so that the electrode assembly 10 is not separated to the outside of the battery case 13. In addition, the sealing portion 134 is sealed to seal the receiving space 1331. Here, the cup-shaped portion 133 having the receiving space 1331 may be formed in the upper case 131 to receive the electrode assembly 10 in the upper portion. As shown in FIG. Figure 4 As shown in FIG. 1 , one side of the upper housing 131 and one side of the lower housing 132 may be connected to each other. However, the present invention is not limited thereto. For example, the upper housing 131 and the lower housing 132 may be manufactured separately to be separated from each other.

[0073] When the electrode lead 12 is connected to the electrode tab 11 of the electrode assembly 10 and the insulating portion 14 is provided on a portion of the electrode lead 12, the electrode assembly 10 can be accommodated in the accommodation space 1331 provided in the cup-shaped portion 133 of the lower shell 132, and the upper shell 131 can cover the accommodation space from the upper side. In addition, the electrolyte is injected, and the sealing portion 134 extending outward from the edge of the upper shell 131 and the edge of the lower shell 132 is sealed. The electrolyte can move lithium ions generated by the electrochemical reaction of the electrode 100 during the charging and discharging process of the secondary battery 1. The electrolyte may include a non-aqueous organic electrolyte or a polymer using a polymer electrolyte, wherein the non-aqueous organic electrolyte is a mixture of a lithium salt and a high-purity organic solvent. The pouch-type secondary battery 1 can be manufactured by the above method.

[0074] Figure 5 is a schematic diagram of an electrode 100 a according to a first embodiment of the present invention.

[0075] According to an embodiment of the present invention, since the slits 1005a to 1005f are formed in the active material uncoated portions 1004a to 1004j of the electrode 100, the electrode 100 can be prevented from bending or warping even after the rolling process is completed. In particular, according to the degree of warping of the electrode 100 (which varies depending on the size and type of the electrode 100 and the applied heat and pressure), the slits 1005a to 1005f having a suitable shape can be formed to more effectively prevent the electrode 100 from bending or warping. In addition, since holes are formed through the points where the slits 1005a to 1005f and the active material coated portion 1003 meet each other, the stress concentrated on one end of the slits 1005a to 1005f can be dispersed to prevent cracks from occurring toward the active material coated portion 1003. In particular, the holes 1006 a to 1006 f may be formed in appropriate shapes according to stress distribution (causing cracks that vary depending on the size and kind of the electrode 100 and applied heat and pressure) to more effectively prevent cracks from occurring toward the active material coating portion 1003 .

[0076] To this end, the electrode 100a according to the first embodiment of the present invention includes: an active material coating portion 1003, which is coated with an electrode active material 1002 on at least one surface of an electrode current collector 1001; and an active material non-coating portion 1004a, which is formed on one side of the active material coating portion 1003, is not coated with the electrode active material 1002, and includes at least one slit 1005a extending from one end thereof to the other end. Here, a hole 1006a is formed through a point where the slit 1005a and the active material coating portion 1003 meet each other.

[0077] like Figure 5As shown in , the electrode 100a includes: an active material coating portion 1003, on which an electrode active material 1002 is applied on at least one surface of an electrode current collector 1001; and an active material uncoated portion 1004a, on which the electrode active material 1002 is not applied.

[0078] The active material coating portion 1003 generates electricity by allowing ions to be injected through the electrolyte and discharged. In addition, the active material uncoated portion 1004a (i.e., as described above, the uncoated portion is formed on one side of the active material coating portion 1003) is a distal end to which the electrode active material 1002 is not applied. In addition, the electrode tab 11 can be formed by cutting the uncoated portion or connecting a separate conductive member to the uncoated portion by ultrasonic welding or the like.

[0079] According to the first embodiment of the present invention, the active material uncoated portion 1004a includes a slit 1005a extending from one end thereof to the other end. Therefore, after the rolling process is completed, even if the stretching amounts of the active material coated portion 1003 and the active material uncoated portion 1004a are different from each other due to the difference in heat and pressure, the slit 1005a can separate the active material uncoated portion 1004a into two regions to prevent the electrode 100a from bending or warping.

[0080] like Figure 5 As shown in , one end of the active material uncoated portion 1004a is adjacent to the active material coated portion 1003, and the other end of the active material uncoated portion 1004a faces the opposite side of the active material coated portion 1003. In addition, the slit 1005a may extend outward from the boundary between the active material uncoated portion 1004a and the active material coated portion 1003. That is, it is preferred that one end of the slit 1005a is formed at the boundary between the active material uncoated portion 1004a and the active material coated portion 1003. This is because there is a problem that if the slit 1005a does not reach the boundary of the active material coated portion 1003, a region in which the slit 1005a is not formed will appear in the active material uncoated portion 1004a, and the region will bend or warp even after the rolling process is completed.

[0081] In addition, the slit 1005a is formed only in the active material uncoated portion 1004a, and preferably, the slit 1005a does not extend to the active material coated portion 1003. Because the area of ​​the active material coated portion 1003 on the electrode 100a is relatively large, and the thickness of the active material coated portion 1003 in the electrode 100a is relatively thick, the active material coated portion 1003 is subjected to heat and pressure with a certain intensity. Therefore, after the rolling process is completed, there is no problem of bending or warping of the active material coated portion 1003. However, if the slit 1005a extends to the active material coated portion 1003, the effect of the present invention may not be greatly exhibited, and the energy density may also be reduced by reducing the area of ​​the active material coated portion 1003.

[0082] If the width of the slit 1005a is too narrow, the electrode 100a may be bent or warped even after the rolling process is completed. On the other hand, if the width of the slit 1005a is too wide, the cross-sectional area of ​​the electrode joint 11 may be reduced, and thus, the resistance may be increased. Therefore, it is preferred to set the most suitable width of the slit 1005a in the experiment according to the size and type of the electrode 100a and the temperature and pressure of the electrode 100a to be rolled.

[0083] When the rolling process is performed on the active material coating portion 1003, since the other end of the slit 1005a faces the outside, stress is unlikely to be concentrated, but stress may be concentrated on one end of the slit 1005a to cause cracks to occur toward the active material coating portion 1003. Therefore, according to the first embodiment of the present invention, a hole 1006a is formed through a point where the slit 1005a and the active material coating portion 1003 meet each other. The hole 1006a can disperse the stress concentrated on one end of the slit 1005a to prevent the problem of cracks occurring toward the active material coating portion 1003 due to the slit 1005a even after the rolling process is completed.

[0084] If the size of the hole 1006a is also too narrow, cracks may still occur toward the active material coating portion 1003 after the rolling process. On the other hand, if the size of the hole 1006a is too wide, the energy density is also reduced by reducing the area of ​​the active material coating portion 1003.

[0085] Figure 6 is a schematic diagram of an electrode according to a second embodiment of the present invention.

[0086] According to the first embodiment of the present invention, the active material non-coating portion 1004a includes a slit 1005a extending from one end thereof to the other end. In addition, a hole 1006a is formed at one end of the slit 1005a.

[0087] However, according to the second embodiment of the present invention, Figure 6 As shown in , the active material uncoated portion 1004b includes a plurality of slits 1005b extending from one end thereof to the other end. In addition, a hole 1006b is formed at one end of each of the plurality of slits 1005b. Therefore, the slits 1005b divide the active material uncoated portion 1004b into three or more regions to more effectively prevent the electrode 100b from bending or warping.

[0088] Figure 7 is a schematic diagram of an electrode 100c according to a third embodiment of the present invention, Figure 8 is a schematic diagram of an electrode 100d according to a fourth embodiment of the present invention, Fig. 9 is a schematic diagram of an electrode 100e according to a fifth embodiment of the present invention, and Fig.10 is a schematic diagram of an electrode 100 f according to a sixth embodiment of the present invention.

[0089] According to the first and second embodiments of the present invention, each of the slits 1005a and 1005b has a linear shape. In addition, each of the slits 1005a and 1005b may extend outward in a direction perpendicular to the boundary between each of the active material uncoated portions 1004a and 1004b and the active material coated portion 1003. Therefore, each of all regions into which the active material uncoated portions 1004a and 1004b are divided may have a rectangular shape.

[0090] However, the size and type of the electrode 100 may be different, and the heat and pressure applied according to the rolling process may also be different. Therefore, it may be inefficient to always form only the slit 1005 having the same shape.

[0091] According to other embodiments of the present invention, the shape of the slit 1005 may be different. In particular, according to the third embodiment of the present invention, as Figure 7 As shown in FIG, the slit 1005c may have an inclination with respect to the boundary between the active material uncoated portion 1004c and the active material coated portion 1003. Therefore, the divided area of ​​the active material uncoated portion 1004c may not have a rectangular shape but may have a trapezoidal shape or a triangular shape.

[0092] Alternatively, according to a fourth embodiment of the present invention, Figure 8 As shown in , the slit 1005d can have a curved shape, and in particular, the curved shape can have a center of curvature. In this case, the curvature can always be constant, but the curvature can change regularly or irregularly. Therefore, the slit 1005d can have various shapes, such as a circular arc shape and an elliptical arc shape.

[0093] Alternatively, according to a fifth embodiment of the present invention, Fig. 9 As shown in , the slit 1005e can have a curved shape, and in particular, the curved shape can have multiple centers of curvature. Here, multiple centers of curvature can be alternately arranged at fixed intervals on the left and right sides of the slit 1005e, so that the slit 1005e can have a wavy shape. In addition, the curves formed about each center of curvature can all have the same curvature. Alternatively, these curves can have different curvatures. That is, multiple centers of curvature are not limited and can be arranged differently, and the curvature of the curve formed about each center of curvature can be formed differently.

[0094] Alternatively, according to a sixth embodiment of the present invention, Fig.10 As shown in , the width of the slit 1005f can be changed regularly or irregularly. For example, the width can be uniformly widened from one end to the other end of the slit 1005f, and conversely, the width can be uniformly narrowed. Alternatively, the phenomenon of the width widening and narrowing at fixed intervals can also be repeated. That is, the width of the slit 1005f is not limited and can be formed differently.

[0095] As described above, the degree of warping of the electrode 100 varies depending on the size and type of the electrode 100 and applied heat and pressure, and thus a slit having an appropriate shape may be formed according to the degree of warping of the electrode 100 to more effectively prevent the electrode 100 from bending or warping.

[0096] In addition, a plurality of slits having various shapes may be formed in the active material non-coated portion 1004. In addition, one hole may be formed at one end of each of the plurality of slits.

[0097] In addition, the positive electrode 101 and the negative electrode 102 are different from each other in size and material even in one electrode assembly 10. Therefore, the slit formed in the positive electrode 101 and the slit formed in the negative electrode 102 may have different shapes from each other.

[0098] Fig.11 is a schematic diagram of an electrode 100g according to a seventh embodiment of the present invention, Fig.12 is a schematic diagram of an electrode 100h according to an eighth embodiment of the present invention, Fig.13 is a schematic diagram of an electrode 100i according to a ninth embodiment of the present invention, and Fig.14 is a schematic diagram of an electrode 100j according to a tenth embodiment of the present invention.

[0099] According to the first to sixth embodiments of the present invention, the hole 1006a has a circular shape. However, the size and type of the electrode 100 may be different, and the heat and pressure applied according to the rolling process may also be different. Therefore, it may be inefficient to always form only the hole 1006a having a circular shape.

[0100] For example, if the hole 1006a has a circular shape, the stress may be uniformly dispersed, but the durability of the peripheral area of ​​the hole may differ depending on the type of the electrode 100. That is, there may be an area with strong durability, and therefore, cracks are not easily generated even under large stress, while there may be an area with weak durability, and therefore, cracks are easily generated even under small stress.

[0101] According to other embodiments of the present invention, the shape of the hole may be different. For example, the hole may have at least one of a circular, elliptical or polygonal shape. In particular, each of the holes 1006c and 1006d may have an elliptical shape, and according to the seventh embodiment of the present invention, as shown in FIG. Fig.11 As shown in , the hole 1006c has a major axis of an elliptical shape, which is formed parallel to the slit 1005a. Alternatively, according to the eighth embodiment of the present invention, as Fig.12 As shown in FIG. 1 , the hole 1006 d may have a minor axis of an elliptical shape formed parallel to the slit 1005 a .

[0102] In the elliptical holes 1006c and 1006d, stress is widely dispersed to the corners with small curvature, and stress is narrowly dispersed to the corners with large curvature. Therefore, each of the holes 1006c and 1006d can be formed so that the corners with small curvature face the area with relatively strong durability, and the corners with large curvature face the area with relatively weak durability.

[0103] Alternatively, the hole may have a polygonal shape, and according to the ninth embodiment of the present invention, as Fig.13 As shown in , the hole 1006e may be formed in a pentagonal shape. Alternatively, according to the tenth embodiment of the present invention, as Fig.14 As shown in , the hole 1006f can be formed in a triangular shape.

[0104] In the polygonal holes 1006e and 1006f, stress is widely dispersed to the corners of the straight line, and stress is narrowly dispersed to the apex. Therefore, each of the holes 1006c and 1006d can be formed so that the apex faces the area with relatively strong durability, and the corners of the straight line face the area with relatively weak durability.

[0105] As described above, stress distribution causing cracks may vary depending on the size and type of the electrode 100 and applied heat and pressure, and therefore, according to the stress distribution, holes having an appropriate shape may be formed to more effectively prevent cracks from occurring toward the active material coating portion 1003 .

[0106] In addition, a plurality of slits may be formed in the active material non-coated portion 1004. Here, a hole having various shapes may be formed at one end of each of the plurality of slits, and the holes may have shapes different from each other.

[0107] In addition, the sizes and materials of the positive electrode 101 and the negative electrode 102 are different from each other even in one electrode assembly 10. Therefore, the pores formed in the positive electrode 101 and the pores formed in the negative electrode 102 may have different shapes from each other.

[0108] Those skilled in the art will appreciate that the present invention may be implemented in other specific forms without changing the technical concept or basic features. Therefore, the embodiments disclosed above should be considered illustrative rather than restrictive. Therefore, the scope of the present invention is defined by the appended claims rather than the preceding description and the exemplary embodiments described herein. Various modifications made within the meaning of the equivalents of the claims of the present invention and within the claims will be considered within the scope of the present invention.

[0109] Description of Reference Numerals

[0110] 1: Secondary battery 10: Electrode assembly

[0111] 11: Electrode connector 12: Electrode lead

[0112] 13: Battery case 14: Insulation part

[0113] 100: electrode 101: positive electrode

[0114] 102: negative electrode 103: separator

[0115] 111: Positive terminal 112: Negative terminal

[0116] 121: Positive lead 122: Negative lead

[0117] 131: Upper shell 132: Lower shell

[0118] 133: cup-shaped portion 134: sealing portion

[0119] 1001: Electrode current collector 100: Electrode active material

[0120] 1003: Active material coated portion 1004, 1004a to 1004j: Active material uncoated portion

[0121] 1005a to 1005f: slits 1006a to 1006f: holes

[0122] 1011: Positive electrode current collector 1012: Positive electrode active material

[0123] 1021: Positive electrode current collector 1022: Positive electrode active material

[0124] 1331: Accommodation Space

[0125] CROSS-REFERENCE TO RELATED APPLICATIONS

[0126] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0015833, filed on February 10, 2020, which is hereby incorporated by reference herein in its entirety.

Claims

1. An electrode, comprising: an active material coating portion, wherein the active material coating portion is coated with an electrode active material on at least one surface of the electrode current collector; as well as an active material uncoated portion, the active material uncoated portion being formed on one side of the active material coated portion, not coated with the electrode active material, and comprising at least one slit extending from one end thereof to the other end, wherein a hole is formed through a point where the slit and the active material coating portion meet each other, and wherein the slit has a curved shape in a direction perpendicular to a boundary between the active material uncoated portion and the active material coated portion, and Wherein, the slit does not extend to the active material coating portion.

2. The electrode according to claim 1, wherein The slit has an inclination with respect to the boundary between the active material uncoated portion and the active material coated portion.

3. The electrode according to claim 1, wherein The slit has a curved shape with a constant curvature.

4. The electrode according to claim 1, wherein The slit has a curved shape having a plurality of centers of curvature.

5. The electrode according to claim 4, wherein The slit has a wavy shape.

6. The electrode according to claim 1, wherein The width of the slit varies regularly or irregularly from one end to the other.

7. The electrode according to claim 1, wherein The hole has at least one of a circular shape, an elliptical shape, and a polygonal shape.

8. The electrode according to claim 1, wherein The slits are provided in a plurality, and a hole is formed in one end of each of the plurality of slits.

9. The electrode according to claim 8, wherein The holes have shapes different from each other.

10. An electrode assembly, in which electrodes and separators are alternately stacked, in, Each of the electrodes is an electrode according to any one of claims 1 to 9.

11. The electrode assembly according to claim 10, wherein: The slit formed in the positive electrode of the electrode and the slit formed in the negative electrode of the electrode have shapes different from each other.

12. The electrode assembly according to claim 10, wherein: The pores formed in the positive electrode of the electrode and the pores formed in the negative electrode of the electrode have shapes different from each other.

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