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

Abstract

The present invention relates to an electrode assembly having an electrode tab bonding structure and a secondary battery including the same. More specifically, in an electrode assembly including a resin current collector having a metal layer vapor-deposited on a polymer layer, electrode tabs having different shapes are alternately laminated so that a conductive structure is formed, and the present invention relates to an electrode assembly having an electrode tab bonding structure in which electron transfer is smooth in the electrode lamination direction even in the presence of a polymer layer, and a secondary battery including the same.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0117334 filed on September 16, 2022, and all contents disclosed in the literature of the Korean patent application are included as part of this specification.

[0002] The present invention relates to an electrode assembly having an electrode tab bonding structure and a secondary battery including the same, and more particularly, to an electrode assembly including a resin current collector having a metal layer vapor-deposited on a polymer layer, in which electrode tabs having different shapes are alternately laminated so that a conductive structure is formed, and to an electrode assembly having an electrode tab bonding structure that enables smooth electron transfer in the electrode stacking direction even in the presence of a polymer layer, and a secondary battery including the same.

Background Art

[0003] As the technology development and demand for mobile devices and automobiles have increased explosively, more research has been conducted on secondary batteries having high energy density, discharge voltage, and excellent output stability. Examples of such secondary batteries include lithium-based secondary batteries such as lithium-sulfur batteries, lithium-ion batteries, and lithium-ion polymer batteries. In addition, the secondary batteries as described above can be classified into cylindrical, prismatic, pouch-type, etc. according to their shapes, and among them, the interest and demand for pouch-type battery cells are gradually increasing. The pouch-type battery cell can be stacked with a high degree of integration, has a high energy density per unit weight, and is inexpensive and easy to deform. Therefore, the pouch-type battery cell can be manufactured in various forms and sizes applicable to various mobile devices and automobiles.

[0004] Such a pouch-type battery cell generally has a structure in which a large number of unit cells including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are stacked (i.e., an electrode assembly or a stack cell), and after accommodating this electrode assembly in a battery case, an electrolyte can be injected or a solid electrolyte can be provided in the electrode assembly from the beginning to commercialize the product.

[0005] And, in the electrode assembly, a positive electrode active material or a negative electrode active material is coated and located on an electrode current collector for current transmission. In recent years, for the purpose of increasing the energy density of the battery and improving stability, a lightweight resin current collector obtained by vapor-depositing a metal layer on a polymer layer made of polyimide (PI), polyethylene terephthalate (PET), etc. has been developed and applied to the battery.

[0006] When assembling a stack cell using such a resin current collector, joining between electrode tabs and joining between electrode tabs and lead tabs are required. FIG. 1 is a front view of the structure in which the electrode tab and the lead tab of the resin current collector are joined by a normal method as viewed from the pulling-out direction of the electrode tab, and FIG. 2 is a plan development view schematically showing the lamination and joining positions of the electrode tab and the lead tab when joining the electrode tab and the lead tab of the resin current collector by a normal method. That is, when assembling a stack cell using a resin current collector, as shown in FIGS. 1 and 2, the electrode tab and the lead tab of the resin current collector are simply laminated and joined by a normal method.

[0007] In this case, in the electrode plane direction, electron transfer is smooth due to the metal layer (10) of the resin current collector, but since the polymer layer (20) of the resin current collector is non-conductive, a problem inevitably occurs that electron transfer does not occur smoothly in the electrode stacking direction (through-plane) (in FIG. 1, the arrow means a path through which electrons are transferred although weakly). And thereby, a resistance difference occurs between the electrode in contact with the lead tab (30) and other electrodes, and the battery performance deteriorates during high-rate charge and discharge.

[0008] Therefore, for the purpose of increasing the energy density of the battery and improving stability, a resin current collector obtained by vapor-depositing a metal layer on a polymer layer is applied as an electrode current collector. However, it is necessary to explore a solution that can improve the battery performance by making electron transfer smooth in the electrode stacking direction even in the presence of the polymer layer and removing or minimizing the resistance difference between the electrodes. SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0009] Accordingly, an object of the present invention is to provide an electrode assembly including a resin current collector having a metal layer vapor-deposited on a polymer layer, in which electrode tabs having different shapes are alternately laminated so as to form a conductive structure, and an electrode tab joining structure having smooth electron transfer in the electrode lamination direction even in a state where the polymer layer is present, and a secondary battery including the same.

Means for Solving the Problems

[0010] To achieve the above object, the present invention includes an A-type electrode tab biased to the left and a B-type electrode tab biased to the right with respect to the center line in the entire length direction of the center joint portion between the electrode tabs, the A-type electrode tab and the B-type electrode tab are alternately positioned, a part of the A-type electrode tab and the B-type electrode tab overlap to form the center joint portion, and the remaining portions that do not form the center joint portion with the A-type electrode tab and the B-type electrode tab form side joint portions between electrode tabs of the same type, and the A-type electrode tab and the B-type electrode tab each have an electrode tab joining structure having a structure in which a polymer layer is interposed between two metal layers.

[0011] The present invention also provides a secondary battery including the electrode assembly having the electrode tab joining structure and a storage case for housing the electrode assembly.

Advantages of the Invention

[0012] According to the electrode assembly having the electrode tab joining structure according to the present invention and the secondary battery including the same, in an electrode assembly including a resin current collector having a metal layer vapor-deposited on a polymer layer, electrode tabs having different shapes are alternately laminated so as to form a conductive structure, and there is an advantage that electron transfer is smooth in the electrode lamination direction even in a state where the polymer layer is present.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0015] FIG. 3 is a front view of the structure in which electrode tabs having different shapes are alternately laminated so that a conductive structure is formed according to an embodiment of the present invention, as seen from the drawing-out direction of the electrode tab, and FIG. 4 is a plan view which schematizes the lamination and joining positions of the electrode tab and the lead tab when joining the electrode tab and the lead tab of the resin current collector according to an embodiment of the present invention.

[0016] As shown in Fig. 3, an electrode assembly having an electrode tab joint structure according to the present invention includes A-type electrode tabs (200a, 200a') that are biased to the left and B-type electrode tabs (200b, 200b') that are biased to the right, with reference to the center line in the entire length direction of the center joint portion between the electrode tabs. The A-type electrode tabs (200a, 200a') and the B-type electrode tabs (200b, 200b') are alternately positioned. A part of the A-type electrode tabs (200a, 200a') and the B-type electrode tabs (200b, 200b') overlap to form the center joint portion. The remaining portions that do not form the center joint portion with the A-type electrode tabs (200a, 200a') and the B-type electrode tabs (200b, 200b') form side joint portions between electrode tabs of the same type (200a and 200a' or 200b and 200b'). The A-type electrode tabs (200a, 200a') and the B-type electrode tabs (200b, 200b') each have an electrode tab joint structure in which a polymer layer is interposed between two metal layers.

[0017] Among secondary batteries, a pouch-type battery cell generally has a structure in which a large number of unit cells including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are stacked (i.e., an electrode assembly or a stack cell). After accommodating this electrode assembly in a battery case, an electrolyte can be injected, or a solid electrolyte can be provided in the electrode assembly from the beginning for commercialization. In the electrode assembly, a positive electrode active material or a negative electrode active material is coated and positioned on an electrode current collector for current transmission. In recent years, for the purpose of increasing the energy density and improving the stability of the battery, a lightweight resin current collector in which a metal layer is vapor-deposited on a polymer layer made of polyimide (PI), polyethylene terephthalate (PET), etc. has been developed and applied to the battery. When assembling a stack cell using such a resin current collector, joining between electrode tabs and joining between electrode tabs and lead tabs are required. That is, when assembling a stack cell using a resin current collector, as shown in Figs. 1 and 2, the electrode tabs and lead tabs of the resin current collector are simply stacked and joined in the normal manner.

[0018] In this case, in the electrode plane direction, electron transfer is smooth due to the metal layer (10) of the resin current collector, but since the polymer layer (20) of the resin current collector is non-conductive, a problem inevitably occurs that electron transfer does not occur smoothly in the electrode stacking direction (through-plane) (in FIG. 1, the arrow means the path along which electrons are transferred weakly). And thereby, a resistance difference occurs between the electrode in contact with the lead tab (30) and other electrodes, and the battery performance deteriorates during high-rate charge and discharge.

[0019] Therefore, the applicant of the present application applies a resin current collector with a metal layer vapor-deposited on the polymer layer as an electrode current collector for the purpose of increasing the energy density of the battery and improving the stability. However, even in the presence of the polymer layer, the electron transfer in the electrode stacking direction is smoothed, and by removing or minimizing the resistance difference between the electrodes, an electrode assembly capable of improving the battery performance has been invented.

[0020] The present invention has a core feature in the structure or shape of the electrode tab (200) that extends from the electrode current collector (specifically, a resin current collector including a non-conductive polymer layer and a conductive metal layer) included in the unit cell (100) and is joined to the lead tab (300) made of a metal material. That is, when the electrode tab (200) is configured in the form shown in FIG. 3, the metal layers included in each of the multiple electrode tabs (200) can contact each other, thereby smoothing the electron transfer in the electrode stacking direction and removing or minimizing the resistance difference between the electrodes, and improving the battery performance compared to the normal case (in FIG. 3, the arrow means the path along which electrons are transferred).

[0021] The type A electrode tabs (200a, 200a') and type B electrode tabs (200b, 200b') have a form that extends and protrudes from the electrode current collector included in each of the unit cells (100) of the electrode assembly. Therefore, the electrode current collector also has a structure in which a polymer layer is interposed between two metal layers.

[0022] Then, based on the stacking direction of the electrode tabs (200a, 200b, 200a', 200b'), a lead tab (300) is disposed at the outermost contour of the electrode tab assembly including the type A electrode tabs (200a, 200a') and the type B electrode tabs (200b, 200b') or between the electrode tab assemblies.

[0023] As shown in FIG. 3, one end of the type A electrode tabs (200a, 200a') is located to coincide with one end of the lead tab (300) with reference to the vertical cross section viewed from the direction in which the electrode tab (200) is drawn out, and the other end can be located between the other end and the center of the lead tab (300), but is not limited thereto. Also, as shown in FIG. 3, the type B electrode tabs (200b, 200b') can be located in a shape symmetric to the type A electrode tabs (200a, 200a'), but is not limited thereto.

[0024] Then, as shown in FIGS. 3 and 4, the type A electrode tabs (200a, 200a') and the type B electrode tabs (200b, 200b') have a form in which they are stacked alternately one by one. At this time, the type A electrode tabs (200a, 200a') and the type B electrode tabs (200b, 200b') partially overlap to form a central joint portion.

[0025] In addition, in order to form a conductive structure between the lead tab (300) and all the electrode tabs (200) so as to enable smooth electron transfer, the same type of electrode tabs (200a and 200a', or 200b and 200b') must have a form in which they are crimped in units of two in the direction of one end of the lead tab (300). At this time, one electrode tab of the other type is interposed therebetween. Therefore, the same type of electrode tabs are crimped to form a side joint portion, and at the same time, they form a shape with the other type of electrode tab interposed therebetween, and the metal layers included in the same type of electrode tabs come into contact with each other at the side joint portion. At this time, the tip of the side joint portion can be located to coincide with one end of the lead tab as shown in FIG. 3, but is not limited thereto.

[0026] That is to say, in other words, when the same type of electrode tabs (200a and 200a', or 200b and 200b') are crimped in units of two in the direction of one end of the lead tab (300), the metal layers respectively included in the same type of electrode tabs come into contact with each other at the portion (side joint) having the crimped form. Also, due to the crimped form, one different type of electrode tab is interposed between the same type of electrode tabs (200a and 200a', or 200b and 200b'), so that the metal layers also face and contact each other between the different types of electrode tabs.

[0027] Therefore, the same type of electrode tabs are in contact with each other via the metal layer at the side joint, and different types of electrode tabs (for example, 200a and 200b, 200b and 200a', 200a' and 200b') are in contact with each other via the metal layer at the center joint, whereby a continuous conductive structure is formed between all the electrode tabs including the type A electrode tabs (200a and 200a') and the type B electrode tabs (200b and 200b'). And thereby, a continuous conductive structure is also formed between the lead tab (300) and all the electrode tabs, and electron transfer is smoothly performed. Therefore, any one or more of the type A electrode tabs (200a, 200a') and the type B electrode tabs (200b, 200b') must be provided in an even number.

[0028] The A-type electrode tabs (200a and 200a') and the B-type electrode tabs (200b and 200b') can overlap each other with a width exceeding 50% and not exceeding 80% of the width standard of the lead tab (300), preferably 60% - 80%, more preferably 70% - 80%, based on the vertical cross-section viewed from the direction in which the electrode tab (200) is drawn out. In case the width of each of the A-type electrode tabs (200a and 200a') and the B-type electrode tabs (200b and 200b') is 50% or less of the width standard of the lead tab (300), it may not be easy for the contact between the electrode tabs of different types. That is, in other words, the central joint portion may not be formed, and it may be difficult for the A-type electrode tabs (200a, 200a') and the B-type electrode tabs (200b, 200b') to contact via the metal layer. And when the width of each of the A-type electrode tabs (200a and 200a') and the B-type electrode tabs (200b and 200b') exceeds 80% of the width standard of the lead tab (300), unnecessary portions where the electrode tabs of different types do not contact may occur, and in this case, it may be disadvantageous in terms of the required cost.

[0029] Also, the lead tab (300) can physically contact only the A-type electrode tab (200a), but as shown in FIG. 3, if it is physically contacted with the B-type electrode tab (200b) in addition to the A-type electrode tab (200a), the electron transfer can be made smoother. That is, in other words, the lead tab (300) preferably contacts with any one of the A-type electrode tabs and any one of the B-type electrode tabs positioned to face it. And at the same time, as shown in FIG. 3, when the lead tab (300) contacts the entire end face of the other end of the A-type electrode tab (200a) that is not crimped, the electron transfer can be made smoother.

[0030] Hereinafter, with reference to FIG. 3, the A-type electrode tabs (200a, 200a') and the B-type electrode tabs (200b, 200b') will be further specifically described as one embodiment. FIG. 3 is an electrode assembly composed of only two A-type electrode tabs (200a, 200a') and two B-type electrode tabs (200b, 200b'). In the following embodiments, the two A-type electrode tabs (200a, 200a') will be denoted as the first electrode tab (200a) and the third electrode tab (200a'), and the two B-type electrode tabs (200b, 200b') will be denoted as the second electrode tab (200b) and the fourth electrode tab (200b').

[0031] When the electrode assembly of the present invention includes only a total of four electrode tabs, the electrode tabs included in the electrode assembly are in contact so as to face the lead tab (300), one end is positioned to coincide with one end of the lead tab (300), and the other end is positioned between the other end and the center of the lead tab (300), the first electrode tab (200a), the second electrode tab (200b) having a shape symmetrical to the first electrode tab (200a) and in contact so as to partially overlap on the other surface of the first electrode tab (200a) that does not face the lead tab (300), the 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 in contact so as to partially overlap on the other surface of the second electrode tab (200b) that does not face the first electrode tab (200a), and the fourth electrode tab (200b') having the same shape as the second electrode tab (200b) and a shape symmetrical to the first electrode tab (200a), and in contact so as to partially overlap on the other surface of the third electrode tab (200a') that does not face the second electrode tab (200b).

[0032] (That is, when the A-type electrode tab includes the first electrode tab and the third electrode tab, and the B-type electrode tab includes the second electrode tab and the fourth electrode tab, the first electrode tab contacts the lead tab so as to face it, and the second electrode tab, the third electrode tab, and the fourth electrode tab are sequentially positioned on the other surface of the first electrode tab that does not face the lead tab)

[0033] And one end of the first electrode tab (200a) and one end of the third electrode tab (200a') that coincide with one end of the lead tab (300) have a form crimped with the second electrode tab (200b) interposed 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 having a form in which one end of the first electrode tab (200a) and one end of the third electrode tab (200a') are crimped, contact is made between the facing metal layers of the first electrode tab (200a) and the third electrode tab (200a'), and contact may also be made between the metal layers of the first electrode tab (200a) and the third electrode tab (200a') that do not face each other.

[0034] Also, one end of the second electrode tab (200b) and one end of the fourth electrode tab (200b') that coincide with the other end of the lead tab (300) have a form crimped with the third electrode tab (200a') interposed 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 form in which one end of the second electrode tab (200b) and one end of the fourth electrode tab (200b') are crimped, contact is made between the facing metal layers of the second electrode tab (200b) and the fourth electrode tab (200b'), and contact may also be made between the metal layers of the second electrode tab (200b) and the fourth electrode tab (200b') that do not face each other.

[0035] Also, the lead tab (300) can physically contact only the first electrode tab (200a). However, as shown in FIG. 3, if it is physically contacted with the second electrode tab (200b) in addition to the first electrode tab (200a), electron transfer can be made smoother. And at the same time, as shown in FIG. 3, by also making the lead tab (300) contact the entire other end tip surface of the first electrode tab (200a) that is not crimped, electron transfer can be made smoother. On the other hand, for the sake of convenience of explanation, an electrode assembly composed of four electrode tabs has been exemplified, but it will be obvious to those skilled in the art that a large number of additional electrode tabs can be laminated. For example, on the other surface side of the fourth electrode tab (200b’) that does not face the third electrode tab (200a’), a large number of the A-type electrode tabs and B-type electrode tabs can be further included alternately.

[0036] Next, the secondary battery according to the present invention will be described. The secondary battery includes the electrode assembly of the present invention described above and a storage case that houses the electrode assembly. And the secondary battery is not particularly limited in use. The secondary battery can be any battery that can accommodate the electrode assembly inside a storage case such as a pouch, but is preferably a lithium-based secondary battery.

[0037] When the lithium-based secondary battery is a lithium-sulfur battery, it can contain sulfur as a positive electrode active material, and a sulfur-carbon composite containing a carbon material can also be applied as a positive electrode active material. When the lithium-based secondary battery is a lithium-ion battery, examples of the positive electrode active material include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, LiMn2O4, etc.), lithium iron phosphate compound (LiFePO4), and lithium nickel cobalt manganese-based positive electrode active material (or lithium NCM-based positive electrode active material, or NCM-based lithium composite transition metal oxide, or High Ni positive electrode material). Further, the positive electrode further includes a binder, a conductive material, etc. in addition to the positive electrode active material.

[0038] The binder is a component that aids in binding the positive electrode active material, conductive material, etc. and binding to the current collector. For example, one or more selected from the group consisting of 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 - butylene rubber, fluororubber, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, and mixtures thereof may be used, but are not necessarily limited thereto.

[0039] The binder is usually added in an amount of 1 to 50 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the total positive electrode. If the content of the binder is less than 1 part by weight, the adhesion between the positive electrode material and the current collector may be insufficient. If it exceeds 50 parts by weight, although the adhesion is improved, the content of the positive electrode material decreases accordingly, and the battery capacity may be reduced.

[0040] The conductive material contained in the positive electrode is not particularly limited as long as it does not cause side reactions in the internal environment of the battery, does not cause chemical changes to the battery, and has excellent electrical conductivity. Typically, graphite or conductive carbon can be used. For example, graphite 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, lamp black; carbon-based substances with a crystal structure of graphene or graphite; conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives can be used alone or in combination of two or more, but are not necessarily limited thereto.

[0041] The conductive material is usually added in an amount of 0.5 to 50 parts by weight, preferably 1 to 30 parts by weight, based on 100 parts by weight of the total positive electrode. If the content of the conductive material is less than 0.5 parts by weight, it is difficult to expect an effect of improving electrical conductivity, or the electrochemical characteristics of the battery may deteriorate. If the content of the conductive material exceeds 50 parts by weight and is too much, the amount of the positive electrode material relatively decreases, and the capacity and energy density may decrease. The method of incorporating the conductive material into the positive electrode is not greatly limited, and ordinary methods known in the art such as coating on the positive electrode material can be used. Further, if necessary, a conductive second coating layer can be added to the positive electrode material to replace the addition of the conductive material as described above.

[0042] In addition, a filler can be selectively added to the positive electrode as a component for suppressing its expansion. Such a filler is not particularly limited as long as it can suppress the expansion of the electrode without causing chemical changes to the battery. For example, olefin polymers such as polyethylene and polypropylene; fibrous substances such as glass fibers and carbon fibers can be used.

[0043] The positive electrode can be manufactured by dispersing and mixing the positive electrode material, binder, conductive material, etc. in a dispersion medium (solvent) to prepare a slurry, applying this onto a positive electrode current collector, and then drying and rolling. As the dispersion medium, NMP (N-methyl-2-pyrrolidone), DMF (Dimethyl formamide), DMSO (Dimethyl sulfoxide), ethanol, isopropanol, water, and mixtures thereof can be used, but are not necessarily limited thereto.

[0044] As the positive electrode current collector, 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 alloys thereof, and those obtained by surface-treating the surface of aluminum (Al) or stainless steel with carbon (C), nickel (Ni), titanium (Ti), or silver (Ag) can be used, but are not necessarily limited thereto. The form of the positive electrode current collector can be in the form of foil, film, sheet, punched material, porous body, foam, etc.

[0045] The negative electrode can be manufactured according to a conventional method known in the art. For example, a negative electrode active material, conductive material, binder, and optionally a filler, etc. are dispersed and mixed in a dispersion medium (solvent) to prepare a slurry, which is applied onto a negative electrode current collector and then dried and rolled to manufacture the negative electrode. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Sb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β(0 < β < 2), metal oxides such as SnO2, vanadium oxides, and lithium vanadium oxides that can be doped and undoped with lithium; or composites containing the metal compound and a carbonaceous material such as Si-C composites or Sn-C composites, etc. can be mentioned, and one or a mixture of two or more of these may be used. Further, a thin film of metallic lithium can also be used as the negative electrode active material. Also, as the carbon material, all of low-crystalline carbon and high-crystalline carbon, etc. can be used. Representative examples of low-crystalline carbon are soft carbon and hard carbon, and representative examples of high-crystalline carbon are amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes, etc.

[0046] Also, the binder and the conductive material used for the negative electrode can be the same as those described above for the positive electrode. As the negative electrode current collector, 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, and those obtained by surface-treating the surface of copper (Cu) or stainless steel with carbon (C), nickel (Ni), titanium (Ti) or silver (Ag), etc. can be used, but are not necessarily limited thereto. The form of the negative electrode current collector can be in the form of a foil, film, sheet, punched material, porous body, foam, etc.

[0047] As the separation membrane, olefin polymers such as polyethylene and polypropylene, glass fibers, etc. can be used in the form of sheets, multilayer films, microporous films, woven fabrics, non-woven fabrics, etc., but are not necessarily limited thereto. However, it is preferable to apply porous polyethylene or porous glass fiber non-woven fabric (glass filter) as the separation membrane, and it is more preferable to apply porous glass fiber non-woven fabric (glass filter) as the separation membrane.

[0048] On the other hand, when a solid electrolyte such as a polymer (for example, an organic solid electrolyte, an inorganic solid electrolyte, etc.) is used as the electrolyte, the solid electrolyte can also serve as the separation membrane. Specifically, an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separation membrane can generally be in the range of 0.01 to 10 μm, and the thickness can generally be in the range of 5 to 300 μm, but is not limited thereto.

[0049] As the electrolyte or electrolytic solution, carbonates, esters, ethers, or ketones of non-aqueous electrolytic solutions (non-aqueous organic solvents) can be used alone or in a mixture of two or more, but are not necessarily 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-pyrrolidinone, 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 aprotic organic solvents can be used, but are not necessarily limited thereto.

[0050] The electrolyte can be further added with a lithium salt for use (so-called lithium salt-containing non-aqueous electrolyte). As the lithium salt, known ones that are easily soluble in the non-aqueous electrolyte can be used, for example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiPF3(CF2CF3)3, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylborate, lithium imide, etc. can be mentioned, but are not necessarily limited thereto. For the said (non-aqueous) electrolyte, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, glyme-based compound, hexamethylphosphoric triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. can also be added. If necessary, a halogen-containing solvent such as carbon tetrachloride or vinylidene fluoride can be further included to impart non-flammability, and carbon dioxide gas can be further included to improve high-temperature storage characteristics.

[0051] On the other hand, the secondary battery can be manufactured according to the usual methods in the art. For example, it can be manufactured by inserting a porous separator between the positive electrode and the negative electrode and injecting a non-aqueous electrolyte. The secondary battery according to the present invention can be applied not only to a battery cell used as a power source for a small device, but can be particularly preferably used as a unit cell of a battery module that is a power source for medium and large devices. From this aspect, the present invention also provides a battery module in which two or more secondary batteries are electrically connected (in series or in parallel). Of course, the number of secondary batteries included in the battery module can be adjusted variously in consideration of the use and capacity of the battery module.

[0052] Furthermore, the present invention provides a battery pack in which the battery modules are electrically connected according to the ordinary techniques in the art. The battery modules and the battery pack can be used as a power source for one or more medium to large-sized devices among Power Tools; electric vehicles including Electric Vehicles (EVs), Hybrid Electric Vehicles (HEVs), and Plug-in Hybrid Electric Vehicles (PHEVs); electric trucks; electric commercial vehicles; or power storage systems, but are not necessarily limited thereto.

[0053] As described above, the present invention has been described through preferred embodiments. However, the present invention is not limited thereto, and those skilled in the technical field to which the present invention pertains will easily understand that various modifications and variations are possible without departing from the concept and scope of the claims described below.

[0054] [Example 1] Manufacture of the Electrode Assembly As shown in FIGS. 3 and 4, an electrode assembly having an electrode tab joining structure having an electrode tab joining structure having an A-type electrode tab positioned to be biased to the left and a B-type electrode tab positioned to be biased to the right with respect to the center line in the entire length direction of the center joining portion between the electrode tabs was manufactured. At this time, the A-type electrode tabs and the B-type electrode tabs are alternately positioned, and a part of the A-type electrode tabs and the B-type electrode tabs overlap to form the center joining portion, and the remaining portions that do not form the center joining portion with the A-type electrode tabs and the B-type electrode tabs form side joining portions between electrode tabs of the same type. The A-type electrode tabs and the B-type electrode tabs each have a structure in which a polymer layer is interposed between two metal layers.

[0055] [Comparative Example 1] Manufacture of the Electrode Assembly As shown in FIGS. 1 and 2, an electrode assembly was manufactured by simply laminating and joining electrode tabs of a resin current collector in which a polymer layer was interposed between two metal layers in a normal manner.

[0056] [Experimental Example 1] Measurement of the Electrical Resistance between the Electrode Tab and the Lead Tab First, with reference to the electrode tab stacking direction of the electrode assembly manufactured in Example 1 above, after arranging a lead tab on the outermost contour of the electrode tab assembly including the A-type electrode tab and the B-type electrode tab, welding was performed to measure the electrical resistance between the electrode tab and the lead tab.

[0057] Separately from this, after arranging a lead tab on the outermost contour of the electrode assembly manufactured in Comparative Example 1 above, welding was performed to measure the electrical resistance between the electrode tab and the lead tab.

[0058] As a result of the measurement, when the electrode assembly manufactured in Comparative Example 1 was used, the electrical resistance between the electrode tab and the lead tab was measured to be 0.12 to 0.16 ohm, whereas when the electrode assembly manufactured in Example 1 was used, the electrical resistance between the electrode tab and the lead tab was measured to be 0.05 to 0.07 ohm.

[0059] Therefore, it can be understood that when the electrode assembly of the present invention in which electrode tabs having different shapes are alternately stacked so as to form a conductive structure is used, electron transfer is smoothly performed in the electrode stacking direction even in a state where a polymer layer exists.

Explanation of Reference Numerals

[0060] 100: Unit cell 200: Electrode tab (200a, 200a': A-type electrode tab, 200b, 200b': B-type electrode tab) 300: Lead tab

Claims

1. An electrode assembly having an electrode tab joining structure, comprising an A-type electrode tab positioned to be offset to the left and a B-type electrode tab positioned to be offset to the right, with reference to the center line in the entire length direction of the center joint between the electrode tabs, wherein the A-type electrode tabs and the B-type electrode tabs are alternately positioned, wherein a part of the A-type electrode tabs and the B-type electrode tabs overlap to form the center joint, wherein the remaining portions that do not form the center joint with the A-type electrode tabs and the B-type electrode tabs form side joints between electrode tabs of the same type, and wherein the A-type electrode tabs and the B-type electrode tabs each have a structure in which a polymer layer is interposed between two metal layers.

2. The electrode assembly having the electrode tab joining structure according to Claim 1, wherein side joints are formed in a form in which electrode tabs of the same type are crimped, forming a shape that interposes electrode tabs of other types, and wherein metal layers included in the electrode tabs of the same type contact each other at the side joints.

3. The electrode assembly having the electrode tab joining structure according to Claim 2, wherein electrode tabs of the same type contact each other through a metal layer at the side joints, and electrode tabs of different types contact each other through a metal layer at the center joint, thereby forming a continuous conductive structure between all electrode tabs including the A-type electrode tabs and the B-type electrode tabs.

4. The electrode assembly having the electrode tab joining structure according to Claim 1, wherein one or more of the A-type electrode tabs and the B-type electrode tabs are provided in an even number.

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

6. The electrode assembly having the electrode tab joining structure according to Claim 1, wherein a lead tab is disposed at the outermost periphery of an electrode tab assembly including the A-type electrode tabs and the B-type electrode tabs or between the electrode tab assemblies, with reference to the stacking direction of the electrode tabs.

7. An electrode assembly having the electrode tab joining structure according to claim 6, wherein a tip of the side joining portion coincides with one of the ends of the lead tab.

8. An electrode assembly having the electrode tab joining structure according to claim 6, wherein the type A electrode tab and the type B electrode tab overlap each other with a width exceeding 50% and not exceeding 80% of the width standard of the lead tab.

9. An electrode assembly having the electrode tab joining structure according to claim 6, wherein the lead tab is in contact with one of the type A electrode tabs and one of the type B electrode tabs positioned to face the one type A electrode tab.

10. A secondary battery including: an electrode assembly having the electrode tab joining structure according to any one of claims 1 to 9; and a storage case for housing the electrode assembly.

Images