Electrode assembly having electrode tip joining structure and secondary battery including the same

Abstract

The present invention relates to an electrode assembly having an electrode tab joining structure and a secondary battery comprising the same, and more particularly, to an electrode assembly having an electrode tab joining structure and a secondary battery comprising the same, the electrode assembly includes a resin current collector having a metal layer deposited on a polymer layer, in which electrode tabs of different shapes are alternately stacked to form a conductive structure, and electron conduction is promoted in an electrode stacking direction even in the presence of the polymer layer.

Description

[Technical field]

[0001] This application claims the benefit of and priority to Korean Patent Application No. 10-2022-0117334, filed on September 16, 2022, the disclosure of which is incorporated herein by reference in its entirety as a part of this specification.

[0002] The present invention relates to an electrode assembly with an electrode tab joining structure and a secondary battery comprising the electrode assembly, and more specifically, to an electrode assembly with an electrode tab joining structure and a secondary battery comprising the electrode assembly, wherein the electrode assembly comprises a resin collector having a metal layer deposited on a polymer layer, wherein electrode tabs of different shapes are alternately stacked to form a conductive structure, and the conduction of electrons is promoted in the electrode stacking direction even in the presence of a polymer layer. [Background Technology]

[0003] With the development of technology and the explosive growth of demand for mobile devices and automobiles, more research has been conducted on secondary batteries with high energy density, discharge voltage and good output stability. Examples of such secondary batteries include lithium secondary batteries such as lithium-sulfur batteries, lithium-ion batteries and lithium-ion polymer batteries. In addition, the above-mentioned secondary batteries can be divided into cylindrical, prismatic, pouch-type, etc. according to their shapes, among which the interest and demand for pouch-type battery cells are gradually increasing. Pouch-type battery cells can be stacked in a highly integrated manner, have a high energy density per unit weight, and are also inexpensive and easy to deform. Therefore, pouch-type battery cells can be manufactured into shapes and sizes suitable for various mobile devices and automobiles.

[0004] These pouch-type battery cells typically have a stacked structure of multiple unit cells, each of which includes a negative electrode, a positive electrode, and a separator inserted between the negative and positive electrodes (i.e., an electrode assembly or stacked cells), which can be manufactured by housing the electrode assembly in a battery case and then injecting an electrolyte, or by having a solid electrolyte in the electrode assembly from the beginning.

[0005] Then, within the electrode assembly, the negative electrode active material or the positive electrode active material is coated and disposed on the electrode collector to conduct current. In recent years, in order to increase the energy density and improve the stability of the battery, a lightweight resin collector having a metal layer deposited on a polymer layer made of polyimide (PI) or polyethylene terephthalate (PET) has been developed and applied to batteries.

[0006] When assembling battery cells into a stack using such a resin collector, bonding between electrode tabs and bonding between the electrode tabs and lead tabs are required. Figure 1is a front view of a structure of an electrode terminal tab and a lead terminal tab of a resin current collector joined in a conventional manner, as viewed from the lead-out direction of the electrode terminal tab; Figure 2 1 is a plan view schematically showing the stacking and joining positions of the electrode tabs and the lead tabs of the resin collector when the electrode tabs and the lead tabs are joined together in a conventional manner. In other words, even if the battery cell is assembled into a stack using the resin collector, the electrode tabs and the lead tabs of the resin collector are simply stacked and joined in a conventional manner, such as Figure 1 and 2 shown.

[0007] In this case, the metal layer 10 of the resin collector promotes the conduction of electrons in the planar direction of the electrode, but since the polymer layer 20 of the resin collector is non-conductive, the conduction of electrons is inevitably poor in the through-plane direction of the electrode stack (in Figure 1 , the arrows indicate the path of electron transport, albeit weakly). This results in a resistance difference between the electrode in contact with the lead tab 30 and the other electrodes, inevitably leading to poor battery performance during high-rate charge and discharge.

[0008] Therefore, it is necessary to apply a resin collector having a metal layer deposited on a polymer layer as an electrode collector to increase the energy density of the battery and improve the stability of the battery, but a method of improving battery performance is sought in the following manner: even in the presence of a polymer layer, the electron conduction in the electrode stacking direction is smooth, thereby eliminating or minimizing the resistance difference between the electrodes. [Summary of the invention]

[0009] [Technical issues]

[0010] Therefore, an object of the present invention is to provide an electrode assembly having an electrode tab joining structure and a secondary battery comprising the electrode assembly, wherein the electrode assembly comprises a resin collector having a metal layer deposited on a polymer layer, wherein electrode tabs of different shapes are alternately stacked to form a conductive structure, which promotes the conduction of electrons in the electrode stacking direction even in the presence of a polymer layer.

[0011] [Technical solution]

[0012] In order to achieve the above-mentioned objectives, the present invention provides an electrode assembly having an electrode tab joining structure, comprising: an A-type electrode tab, which is arranged to be biased to the left side of the length direction center line of the central joint between the electrode tabs; and a B-type electrode tab, which is arranged to be biased to the right side of the center line, wherein the A-type electrode tab and the B-type electrode tab are alternately arranged, and the A-type electrode tab and the B-type electrode tab partially overlap to form the central joint, wherein the remaining parts of the A-type electrode tab and the B-type electrode tab that do not form the central joint form a structure in which side joints are formed with electrode tabs of the same type, and wherein the A-type electrode tab and the B-type electrode tab each have a structure in which a polymer layer is inserted between two metal layers.

[0013] In addition, the present invention provides a secondary battery, which includes: the electrode assembly having the electrode tab bonding structure; and a receiving case for accommodating the electrode assembly.

[0014] [Beneficial Effects]

[0015] According to the present invention, an electrode assembly having an electrode tab joining structure and a secondary battery comprising the electrode assembly are provided, wherein electrode tabs of different shapes are alternately stacked in the electrode assembly, so that a conductive structure is formed in the electrode assembly having a resin collector with a metal layer deposited on a polymer layer, thereby providing a joining structure for the electrode tabs, wherein the conduction of electrons in the electrode stacking direction is promoted even in the presence of a polymer layer. [Drawings]

[0016] Figure 1 This is a front view of a structure in which an electrode tab of a resin collector and a lead tab are joined in a conventional manner, as viewed from the direction in which the electrode tab is led out.

[0017] Figure 2 is a plan view schematically showing the stacking and bonding positions of an electrode tab and a lead tab of a resin collector when the electrode tab and the lead tab are bonded together in a conventional manner.

[0018] Figure 3 is a front view of a structure in which electrode tabs of different shapes are alternately stacked to form a conductive structure according to one embodiment of the present invention, as viewed from a direction in which the electrode tabs are led out.

[0019] Figure 4 is a plan view schematically showing stacking and bonding positions of an electrode tab and a lead tab of a resin collector when bonding the electrode tab and the lead tab according to one embodiment of the present invention. [Specific implementation method]

[0020] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0021] Figure 3 is a front view of a structure in which electrode tabs of different shapes are alternately stacked to form a conductive structure according to one embodiment of the present invention, as viewed from a direction in which the electrode tabs are led out; Figure 4 is a plan view schematically showing stacking and bonding positions of an electrode tab and a lead tab of a resin collector when bonding the electrode tab and the lead tab according to one embodiment of the present invention.

[0022] The electrode assembly with the electrode terminal tab bonding structure of the present invention is as follows: Figure 3 As shown, it includes: A-type electrode terminals 200a, 200a', which are arranged to the left of the length direction center line of the central joint between the electrode terminals; B-type electrode terminals 200b, 200b', which are arranged to the right of the center line, wherein the A-type electrode terminals 200a, 200a' and the B-type electrode terminals 200b, 200b' are alternately arranged, and the A-type electrode terminals 200a, 200a' and the B-type electrode terminals 200b, 200b' partially overlap. To form the central joint, the remaining parts of the A-type electrode terminal 200a, 200a' and the B-type electrode terminal 200b, 200b' that do not form the central joint form a structure in which side joints are formed with the same type of electrode terminal 200a, 200a' and 200b, 200b' respectively, and wherein the A-type electrode terminal 200a, 200a' and the B-type electrode terminal 200b, 200b' each have a structure in which a polymer layer is inserted between two metal layers.

[0023] In secondary batteries, pouch-type battery cells generally have a stacked structure of multiple unit cells each including a negative electrode, a positive electrode, and a separator inserted between the negative electrode and the positive electrode (i.e., an electrode assembly or a stacked cell), which can be manufactured by housing the electrode assembly in a battery case and then injecting an electrolyte, or by having a solid electrolyte in the electrode assembly from the beginning. In the electrode assembly, a negative electrode active material or a positive electrode active material is coated and arranged on the electrode collector to conduct current. At the same time, in recent years, in order to increase the energy density and improve the stability of the battery, a lightweight resin collector having a metal layer deposited on a polymer layer such as polyimide (PI) or polyethylene terephthalate (PET) has been developed and applied to batteries. When assembling stacked cells using such a resin collector, bonding between electrode tabs and bonding between electrode tabs and lead tabs are required. In other words, even if the stacked cells are assembled using a resin collector, the electrode tabs and lead tabs of the resin collector are simply stacked and bonded in a conventional manner, such as Figure 1 and 2 shown.

[0024] In this case, the metal layer 10 of the resin collector promotes the conduction of electrons in the planar direction of the electrode, but since the polymer layer 20 of the resin collector is non-conductive, the conduction of electrons is inevitably poor in the through-plane direction of the electrode stack (in Figure 1 , the arrows indicate the path of electron transport, albeit weakly). This results in a resistance difference between the electrode in contact with the lead tab 30 and the other electrodes, inevitably leading to poor battery performance during high-rate charge and discharge.

[0025] Therefore, the present inventors have invented an electrode assembly that can improve the performance of a battery by applying a resin collector coated with a metal layer on a polymer layer as a collector and by promoting the conduction of electrons in the electrode stacking direction even in the presence of a polymer layer, thereby eliminating or minimizing the resistance difference between electrodes, thereby improving the energy density and stability of the battery.

[0026] The key feature of the present invention lies in the structure or shape of the electrode tab 200, which extends and protrudes from the collector (specifically, the resin collector including the non-conductive polymer layer and the conductive metal layer) included in the unit cell 100 and is joined to the lead tab 300 made of metal. Figure 3 The shape shown forms an electrode terminal tab 200, and the metal layers contained in each of the plurality of electrode terminal tabs 200 can contact each other, thereby promoting the conduction of electrons in the electrode stacking direction, thereby eliminating or minimizing the resistance difference between the electrodes and improving the performance of the battery compared with the conventional case ( Figure 3 The arrows in the figure indicate the conduction paths of electrons).

[0027] The A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' have a shape extending and protruding from a current collector included in each unit cell 100 of the electrode assembly. Therefore, the current collector also has a structure in which a polymer layer is interposed between two metal layers.

[0028] Meanwhile, the lead tab 300 is arranged at the outermost of the electrode tab assembly including the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b', or between the electrode tab assemblies relative to the stacking direction of the aforementioned electrode tabs 200a, 200b, 200a'.

[0029] like Figure 3 As shown, based on the vertical cross section observed from the direction of the electrode tab 200, one end of the A-type electrode tab 200a, 200a' is arranged to overlap with one end of the lead tab 300, and the other end is arranged between the other end of the lead tab 300 and the center portion, but is not limited thereto. Figure 3 As shown, the B-type electrode tabs 200 b and 200 b ′ may be disposed in a shape symmetrical to the A-type electrode tabs 200 a and 200 a ′, but are not limited thereto.

[0030] In addition, the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' have the following characteristics: Figure 3 and 4 At this time, the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' partially overlap to form a central joint.

[0031] In addition, in order to form a conductive structure between the lead tab 300 and all the electrode tabs 200 and promote the conduction of electrons, the same type of electrode tabs 200a, 200a' or 200b, 200b' should have a shape that is crimped in units of two pieces in the direction of one end of the lead tab 300. At this time, a piece of electrode tabs of a different type is inserted between them. Therefore, by crimping the same type of electrode tabs together to form a side joint, they form a shape in which different types of electrode tabs are inserted, and the metal layers contained in each of the same type of electrode tabs contact each other at the side joint. At this time, as Figure 3 As shown, the front edge of the side joint portion may be arranged to coincide with one end of the lead tab, but is not limited thereto.

[0032] In other words, if the same type of electrode tabs 200a, 200a' or 200b, 200b' have a shape that is crimped in units of two pieces in the direction of one end of the lead tab 300, the metal layers included in the respective same type of electrode tabs contact each other at the portion (side joint portion) having the crimped shape. Moreover, since one piece of electrode tabs of different types is inserted between the same type of electrode tabs 200a, 200a' or 200b, 200b' by the crimped shape, the metal layers of the different types of electrode tabs also face and contact each other.

[0033] Therefore, by contacting the metal layer through the side joint, the same type of electrode tabs are in contact with each other, and by contacting the metal layer through the center joint, different types of electrode tabs (e.g., 200a and 200b, 200b and 200a', 200a' and 200b') are in contact with each other, thereby forming a continuous conductive structure between all electrode tabs including the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b'. Therefore, a continuous conductive structure is formed between the lead tab 300 and all electrode tabs, and electron conduction is smoothly performed. Therefore, one or more of the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' should be arranged in an even number.

[0034] Based on the vertical cross section observed from the direction of the electrode tab 200, the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' may each overlap each other by a width greater than 50% and less than 80%, preferably 60% to 80%, and more preferably 70% to 80% based on the width of the lead tab 300. If the width of each of the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' is less than or equal to 50% of the width of the lead tab 300, it may not be easy to promote contact between different types of electrode tabs. In other words, the central joint may not be formed, and the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' may be difficult to contact through the metal layer. Furthermore, if the width of each of the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' exceeds 80% of the width of the lead tab 300, unnecessary portions where different types of electrode tabs are not in contact may occur, and this may be disadvantageous in terms of cost.

[0035] In addition, the lead tab 300 may only physically contact the A-type electrode tab 200a, but Figure 4As shown, if the lead tab 300 physically contacts both the A-type electrode tab 200a and the B-type electrode tab 200b, the conduction of electrons can be smoother. In other words, it is preferred that the lead tab 300 contacts one of the A-type electrode tabs and one of the B-type electrode tabs that are arranged to face each other. Figure 3 As shown, by contacting the lead tab 300 with the entire end section of the uncrimped A-type electrode tab 200a, the conduction of electrons can be smoother.

[0036] Below, see Figure 3 , the A-type electrode tabs 200a, 200a' and the B-type electrode tabs 200b, 200b' will be described in more detail as embodiments. Figure 3 An electrode assembly consisting of only two A-type electrode tabs 200a, 200a' and two B-type electrode tabs 200b, 200b' is shown. In the following embodiments, the two A-type electrode tabs 200a, 200a' are represented as the first electrode tab 200a and the third electrode tab 200a', and the two B-type electrode tabs 200b, 200b' are represented as the second electrode tab 200b and the fourth electrode tab 200b'.

[0037] In the case where the electrode assembly of the present invention includes only four electrode tabs, the electrode tabs included in the electrode assembly include:

[0038] a first electrode tab 200a which contacts the lead tab 300 face to face and has one end disposed to coincide with one end of the lead tab 300 and the other end disposed between the other end of the lead tab 300 and the central portion,

[0039] a second electrode tab 200b having a shape symmetrical to the first electrode tab 200a and contacting a portion of the other side of the first electrode tab 200a that does not face the lead tab 300,

[0040] a third electrode tab 200a' having the same shape as the first electrode tab 200a and a shape symmetrical to the second electrode tab 200b and contacting a portion of the other side of the second electrode tab 200b that does not face the first electrode tab 200a, and

[0041] A fourth electrode tab 200b' has the same shape as the second electrode tab 200b and a shape symmetrical to the first electrode tab 200a, and contacts a portion of the other side of the third electrode tab 200a' that does not face the second electrode tab 200b.

[0042] (That is, in the case where the A-type electrode tab includes a first electrode tab and a third electrode tab and the B-type electrode tab includes a second electrode tab and a fourth electrode tab, the first electrode tab contacts the lead tab face to face, and the second electrode tab, the third electrode tab, and the fourth electrode tab are sequentially disposed on the other side of the first electrode tab that does not face the lead tab)

[0043] In addition, one end of the first electrode tab 200a and one end of the third electrode tab 200a', which are arranged to overlap with one end of the lead tab 300, are crimped in a shape in which the second electrode tab 200b is inserted therebetween, and the metal layer of the first electrode tab 200a and the metal layer of the third electrode tab 200a' are in contact at the crimped portion. That is, by the crimped shape at one end of the first electrode tab 200a and one end of the third electrode tab 200a', the metal layers of the first electrode tab 200a and the third electrode tab 200a' that face each other are in contact with each other, and the metal layers of the first electrode tab 200a and the third electrode tab 200a' that do not face each other may also be in contact with each other.

[0044] Furthermore, one end of the second electrode tab 200b and one end of the fourth electrode tab 200b', which are arranged to overlap with the other end of the lead tab 300, are crimped in a shape in which the third electrode tab 200a' is inserted therebetween, and the metal layer of the second electrode tab 200b and the metal layer of the fourth electrode tab 200b' are in contact at the crimped portion. That is, by having a crimped shape at one end of the second electrode tab 200b and one end of the fourth electrode tab 200b', the metal layers of the second electrode tab 200b and the fourth electrode tab 200b' that face each other contact each other, and the metal layers of the second electrode tab 200b and the fourth electrode tab 200b' that do not face each other may also contact each other.

[0045] In addition, the lead tab 300 may only physically contact the first electrode tab 200a, but Figure 3 As shown, if the lead tab 300 physically contacts both the first electrode tab 200a and the second electrode tab 200b, the conduction of electrons can be smoother. Figure 3 As shown, by contacting the lead tab 300 with the entire end section of the first electrode tab 200a that is not crimped, the conduction of electrons can be smoother. At the same time, for ease of explanation, an electrode assembly consisting of four electrode tabs is illustrated, but it will be easily understood by those skilled in the art that a plurality of electrode tabs may also be stacked. For example, on the other side of the fourth electrode tab 200b' that does not face the third electrode tab 200a', a plurality of A-type electrode tabs and B-type electrode tabs may be alternately included.

[0046] Hereinafter, the secondary battery of the present invention will be described. The secondary battery includes the electrode assembly of the present invention described above and a housing for accommodating the electrode assembly. The secondary battery is not limited to any specific use. The secondary battery may be any battery capable of accommodating the electrode assembly in a storage housing such as a bag, but it may be desirable to use a lithium secondary battery.

[0047] In the case where the lithium secondary battery is a lithium sulfur battery, the positive electrode active material may contain sulfur, including a sulfur-carbon composite that also contains a carbon material. If the above-mentioned lithium secondary battery is a lithium ion battery, examples of positive electrode active materials include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, LiMn2O4, etc.), lithium iron phosphate (LiFePO4), lithium nickel cobalt manganese positive electrode active materials (or lithium NCM positive electrode active materials, or NCM lithium composite transition metal oxides, or high Ni positive electrode materials). In addition to the positive electrode active material, the positive electrode also includes a binder and a conductive material.

[0048] Binder is a component that contributes to the combination of positive electrode active material, conductive material and other components with collector. The example of binder that can be used includes polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF / HFP), polyvinyl acetate, polyvinyl alcohol, polyvinyl ether, polyethylene, polyethylene oxide, alkylated polyethylene oxide, polypropylene, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polytetrafluoroethylene (PTFE), polyvinyl chloride, polyacrylonitrile, polyvinyl pyridine, polyvinyl pyrrolidone, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, styrene-butene rubber, fluororubber, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose and mixtures thereof. However, this is not an exhaustive list of binders that can be used.

[0049] Based on 100 parts by weight of the total weight of the positive electrode, the amount of the binder added is generally 1 to 50 parts by weight, preferably 3 to 15 parts by weight. If the content of the binder is less than 1 part by weight, the adhesion of the positive electrode material to the collector may be insufficient, and if the content of the binder is greater than 50 parts by weight, the adhesion may be improved, but the content of the positive electrode material may be reduced, resulting in a lower battery capacity.

[0050] The conductive material contained in the positive electrode of the battery must have excellent conductivity and not cause any side reactions or chemical changes to the internal environment of the battery. There is no specific limitation on the type of conductive material that can be used, but some examples include: graphite or conductive carbon, for example, carbon such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black and lamp black; carbonaceous materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate whiskers; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These materials can be used alone or in combination with two or more other materials, but are not limited to this.

[0051] The conductive material is usually added to the positive electrode in the range of 0.5 to 50 parts by weight, preferably 1 to 30 parts by weight per 100 parts by weight of the entire positive electrode. If the content of the conductive material is less than 0.5 parts by weight, it may be difficult to expect an improvement in conductivity, or the electrochemical characteristics of the battery may deteriorate. If the content of the conductive material exceeds 50 parts by weight, the amount of the positive electrode material is relatively reduced, which may result in a decrease in the capacity and energy density of the battery. There is no specific restriction on how to include the conductive material in the positive electrode, and conventional methods, such as coating the positive electrode material, can be used. In addition, if necessary, a second coating having conductivity can be added to the positive electrode material instead of adding conductive materials such as those described above.

[0052] A component capable of suppressing electrode expansion may be selectively added to the positive electrode as a filler. The type of filler that can be used is not specifically limited as long as it does not cause any chemical changes to the battery and can suppress the expansion of the electrode. Examples of fillers include polyethylene and polypropylene as olefin polymers, and fiber materials such as glass fiber and carbon fiber.

[0053] The positive electrode material, binder and conductive material can be dispersed in a solvent to produce a slurry. The slurry is then applied to the positive electrode collector, dried and rolled to make the positive electrode. Examples of solvents that can be used include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, isopropanol, water and mixtures thereof.

[0054] The positive electrode collector can be made of various materials, including platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), aluminum (Al), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO2), FTO (F doped SnO2) and their alloys. In addition, the surface of aluminum or stainless steel can be treated with carbon (C), nickel (Ni), titanium (Ti) or silver (Ag). The positive electrode collector can be in the form of foil, film, sheet, punching material, porous material or foam.

[0055] The negative electrode can be manufactured by conventional methods known in the art. For example, a slurry can be prepared by dispersing and mixing a negative electrode active material, a conductive material, a binder and an optional filler in a solvent, and then the slurry is coated on a negative electrode collector, dried and rolled to manufacture the negative electrode. The negative electrode active material can be a compound that can reversibly insert and deinsert lithium. Specific examples include: carbon materials such as artificial graphite, natural graphite, graphitized carbon fiber or amorphous carbon; metal compounds that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy or Al alloy; metal oxides that can be doped and dedoped with lithium, such as SiO β (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide; or a composite comprising a metal compound and a carbon material, such as a Si-C composite or a Sn-C composite. Any one or more mixtures thereof may be used. In addition, a metallic lithium film may be used as a negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as carbon materials. Representative examples of low-crystalline carbon include soft carbon and hard carbon. Representative examples of high-crystalline carbon include amorphous, flaky, needle-shaped, spherical or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-type carbon fibers, mesocarbon microspheres, mesophase pitch, and coke derived from petroleum or coal tar pitch.

[0056] In addition, the binder and conductive material for the negative electrode may be the same as those described for the positive electrode. The negative electrode collector may be made of platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), copper (Cu), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO2), FTO (F doped SnO2) and alloys thereof or a material surface treated with carbon (C), nickel (Ni), titanium (Ti) or silver (Ag) on ​​the surface of copper (Cu) or stainless steel, but is not limited thereto. The negative electrode collector may have a shape of foil, film, sheet, punching, porous or foam.

[0057] The separator can be made of olefin polymers such as polyethylene, polypropylene, glass fiber in the form of sheets, multilayers, microporous membranes, woven fabrics and non-woven fabrics, but is not limited thereto. However, it may be desirable to use porous polyethylene or porous glass fiber non-woven fabrics (glass filter paper) as the separator, and it may be more desirable to use porous glass filter paper (glass fiber non-woven fabric) as the separator.

[0058] On the other hand, when a polymer such as a solid electrolyte (e.g., an organic solid electrolyte, an inorganic solid electrolyte, etc.) is used as an electrolyte, the solid electrolyte can also act as a diaphragm. Specifically, a thin film of an insulating material with high ion permeability and mechanical strength is used. The pore size of the diaphragm can generally be 0.01 μm to 10 μm, and the thickness can generally be 5 μm to 300 μm, but is not limited thereto.

[0059] The electrolyte or electrolyte solution may be a non-aqueous electrolyte (non-aqueous organic solvent) using carbonate, ester, ether or ketone alone or in a mixture of two or more thereof, but is not limited thereto. For example, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, n-methyl acetate, n-ethyl acetate, n-propyl acetate, triester phosphate, dibutyl ether, N-methyl-2-pyrrolidone, 1,2-dimethoxyethane, tetrahydrofuran derivatives such as 2-methyltetrahydrofuran, dimethyl sulfoxide, formamide, dimethylformamide, dioxolane and its derivatives, acetonitrile, nitromethane, methyl formate, methyl acetate, trimethoxymethane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, methyl propionate, ethyl propionate and other non-hydrogen bond organic solvents may be used, but are not limited thereto.

[0060] The electrolyte may also contain a lithium salt (so-called non-aqueous electrolyte containing a lithium salt), and the lithium salt may be any lithium salt that is easily soluble in the non-aqueous electrolyte, such as LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiPF3(CF2CF3)3, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborate, lower aliphatic carboxylic acid lithium, 4-phenylborate lithium, imide lithium, etc., but not limited thereto. The (non-aqueous) electrolyte may also contain additives for improving charge / discharge characteristics, flame retardancy, etc., such as pyridine, triethyl phosphate, triethanolamine, crown ether, ethylenediamine, glycol ether compounds, hexafluorophosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidinones, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, aluminum chloride, etc. If necessary, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further included to impart non-flammability, and carbon dioxide gas may be further included to improve high-temperature storage characteristics.

[0061] Meanwhile, the secondary battery can be manufactured according to conventional methods in the art. For example, a porous separator can be inserted between the negative electrode and the positive electrode, and a non-aqueous electrolyte can be injected to manufacture it. The secondary battery of the present invention can be particularly suitable for use as a unit cell of a battery module as a power source for medium and large devices, and for use in a battery cell used as a power source for small devices. In this regard, the present invention also provides a battery module comprising more than two (in series or in parallel) electrically connected secondary batteries. Of course, various adjustments can be made to the number of secondary batteries contained in the battery module, taking into account the purpose and capacity of the battery module.

[0062] In addition, the present invention provides a battery pack electrically connected to a battery module according to conventional techniques in the art. The battery module or battery pack can be used as a power source for one or more medium-to-large devices such as: power tools; electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs); or power storage systems, but is not limited thereto.

[0063] Although the present invention has been described with reference to the preferred embodiments described above, those skilled in the art will readily appreciate that the present invention is not limited thereto and that various modifications and variations are possible without departing from the spirit and scope of the patent claims set forth below.

[0064] [Example 1] Manufacturing of electrode assemblies

[0065] like Figure 3 and 4As shown, an electrode assembly having an electrode tab joining structure is manufactured, wherein the electrode tabs include: a type A electrode tab, which is arranged to be biased to the left side of the length direction center line of the central joint between the electrode tabs; and a type B electrode tab, which is arranged to be biased to the right side of the center line; wherein the type A electrode tabs and the type B electrode tabs are alternately arranged, and the type A electrode tabs and the type B electrode tabs partially overlap to form the central joint, and the remaining parts of the type A electrode tabs and the type B electrode tabs that do not form the central joint form a structure in which side joints are formed with electrode tabs of the same type, and the type A electrode tabs and the type B electrode tabs each have a structure in which a polymer layer is inserted between two metal layers.

[0066] [Comparative Example 1] Manufacturing of electrode assemblies

[0067] like Figure 1 and 2 As shown, the electrode assembly is manufactured by simply stacking and joining electrode tabs of a resin collector having a polymer layer interposed between two metal layers in a conventional manner.

[0068] [Experimental Example 1] Measurement of resistance between electrode tabs and lead tabs

[0069] First, based on the electrode tab stacking direction of the electrode assembly manufactured in Example 1, the lead tab was placed at the outermost edge of the electrode tab assembly including the A-type electrode tab and the B-type electrode tab, and then the resistance between the electrode tab and the lead tab was measured by welding.

[0070] Additionally, a lead tab was placed at the outermost edge of the electrode assembly manufactured in Comparative Example 1, and then the resistance between the electrode tab and the lead tab was measured by welding.

[0071] As a result of the measurements, when the electrode assembly manufactured in Comparative Example 1 was used, the resistance between the electrode tab and the lead tab was measured to be 0.12 to 0.16 ohms, and when the electrode assembly manufactured in Example 1 was used, the resistance between the electrode tab and the lead tab was measured to be 0.05 to 0.07 ohms.

[0072] Therefore, it can be seen that by using the electrode assembly of the present invention in which the conductive structure is formed by alternately stacking electrode tabs of different shapes, electron conduction in the electrode stacking direction can be smoothly performed even in the presence of a polymer layer.

[0073] <Description of Reference Numerals>

[0074] 100: Cell

[0075] 200: electrode terminal piece (200a, 200a': A-type electrode terminal piece, 200b, 200b': B-type electrode terminal piece)

[0076] 300: Lead lug

Claims

1. An electrode assembly having an electrode terminal tab bonding structure, comprising: A-type electrode tabs are disposed to the left of a lengthwise centerline of a central joint between the electrode tabs; and The B-type electrode terminal piece is arranged to be biased to the right side of the center line, in, The A-type electrode tabs and the B-type electrode tabs are alternately arranged, and the A-type electrode tabs and the B-type electrode tabs partially overlap to form the central joint portion, The remaining parts of the A-type electrode tab and the B-type electrode tab that do not form the central joint portion form a structure in which side joint portions are formed with electrode tabs of the same type, respectively, and The A-type electrode tab and the B-type electrode tab each have a structure in which a polymer layer is inserted between two metal layers.

2. The electrode assembly having an electrode tab bonding structure according to claim 1, wherein: The electrode tabs of the same type are crimped together to form a side joint portion, with electrode tabs of different types interposed therebetween, and metal layers included in the respective electrode tabs of the same type contact each other at the side joint portion.

3. The electrode assembly having an electrode tab bonding structure according to claim 2, wherein: The same type of electrode tabs are in contact with each other through the metal layer at the side joint portion, and the different types of electrode tabs are in contact with each other through the metal layer at the center joint portion, and Wherein, a continuous conductive structure is formed between all electrode tabs including the A-type electrode tab and the B-type electrode tab.

4. The electrode assembly having an electrode tab bonding structure according to claim 1, wherein: At least one of the A-type electrode tabs and the B-type electrode tabs is arranged in an even number.

5. The electrode assembly having an electrode tab bonding structure according to claim 1, wherein: The A-type electrode tab and the B-type electrode tab extend and protrude from an electrode collector included in each unit cell of the electrode assembly, and the electrode collector also has a structure in which a polymer layer is interposed between two metal layers.

6. The electrode assembly having an electrode tab bonding structure according to claim 1, wherein: The lead tab is disposed at the outermost edge of the electrode tab assembly including the A-type electrode tab and the B-type electrode tab, or between the electrode tab assemblies, with respect to the stacking direction of the electrode tabs.

7. The electrode assembly having an electrode tab bonding structure according to claim 6, wherein: The front edge of the side joint portion is arranged to coincide with either end of the lead tab.

8. The electrode assembly having an electrode tab bonding structure according to claim 6, wherein: The A-type electrode tab and the B-type electrode tab each overlap with each other by a width greater than 50% and not greater than 80% based on the width of the lead tab.

9. The electrode assembly having an electrode tab bonding structure according to claim 6, wherein: The lead tab contacts one of the A-type electrode tabs and one of the B-type electrode tabs facing therewith.

10. A secondary battery comprising: The electrode assembly having an electrode tab bonding structure according to claim 1; and A storage shell for accommodating the electrode assembly.

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