Electrode assembly, secondary battery, battery pack, and automobile

Abstract

One embodiment of the present invention provides an electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are stacked and wound, the negative electrode including an in-tab provided at an end located at a mandrel part among both ends in a direction perpendicular to a winding axis of the electrode assembly, the in-tab being provided to surround 50% or more of a surface of the negative electrode facing the mandrel part, and a secondary battery, a battery pack, and a vehicle including the electrode assembly.

Description

[Technical Field]

[0001] The present invention relates to an electrode assembly, a secondary battery, a battery pack, and an automobile.

[0002] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0133219, filed with the Korean Intellectual Property Office on October 17, 2022, the entire contents of which are incorporated herein by reference.

[0003] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0137388, filed with the Korean Intellectual Property Office on October 16, 2023, the entire contents of which are incorporated herein by reference. [Background technology]

[0004] Secondary batteries, which have high applicability across product groups and electrical properties such as high energy density, are widely used not only in portable devices but also in electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are powered by electrical sources.

[0005] Such secondary batteries have the primary advantage of dramatically reducing the use of fossil fuels, as well as the advantage of not producing any by-products from the use of energy, and are therefore attracting attention as a new energy source that is environmentally friendly and improves energy efficiency.

[0006] Currently, widely used types of secondary batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. The operating voltage of such a unit secondary battery cell is approximately 2.5 V to 4.5 V. Therefore, if a higher output voltage is required, a battery pack may be constructed by connecting multiple battery cells in series. Alternatively, a battery pack may be constructed by connecting multiple secondary batteries in parallel according to the required charge / discharge capacity of the battery pack. Therefore, the number and electrical connection form of the secondary batteries included in the battery pack may be variously set depending on the required output voltage and / or charge / discharge capacity. Meanwhile, cylindrical, prismatic, and pouch-type secondary batteries are known as types of secondary batteries, and the secondary battery may be a cylindrical battery. Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode assembly and a secondary battery that prevent deformation of a mandrel portion of a negative electrode of the electrode assembly and prevent short circuits caused by damage to a separator.

[0008] Another object of the present invention is to provide a battery pack including a secondary battery having the above-mentioned improved structure, and a vehicle including the same.

[0009] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention described below. [Means for solving the problem]

[0010] One embodiment of the present invention provides an electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are stacked and wound, wherein the negative electrode includes an in-tab provided at one end of the electrode assembly in a direction perpendicular to a winding axis, the end being located at a mandrel portion, and the in-tab is provided to surround at least 50% of a surface of the negative electrode facing the mandrel portion.

[0011] Another embodiment of the present invention provides a secondary battery including an electrode assembly according to an embodiment of the present invention.

[0012] Another embodiment of the present invention provides a battery pack including the secondary battery according to the above embodiment.

[0013] Another embodiment of the present invention provides a motor vehicle including a battery pack according to the above embodiment. [Effects of the Invention]

[0014] A secondary battery is constructed by interposing a separator, which is an insulator, between a positive electrode and a negative electrode, and winding the electrode assembly into a jelly roll shape. The electrode assembly is then inserted into a battery can together with an electrolyte. When the jelly roll electrode assembly is wound around a mandrel, stress is generated within the electrode assembly as the negative electrode expands and contracts during charging and discharging.

[0015] The mandrel portion of the electrode assembly is an empty space, and the outward expansion force of stress generated during charging and discharging is suppressed by the battery can, causing deformation of the mandrel portion. If the deformation of the mandrel portion is severe, stress may occur, such as causing the electrode to break, which may result in a short circuit due to damage to the separator inside the electrode assembly.

[0016] According to an embodiment of the present invention, an in-tab provided at an end of the negative electrode of the electrode assembly located on the mandrel portion surrounds at least 50% of the surface of the negative electrode facing the mandrel portion, thereby preventing expansion stress inside the electrode assembly from acting on the mandrel portion. This prevents deformation of the mandrel portion of the electrode assembly and short circuits due to damage to the separator, thereby contributing to ensuring battery stability.

[0017] However, the advantageous effects obtained through the present invention are not limited to the effects described above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the invention described below. [Brief explanation of the drawings]

[0018] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical spirit of the present invention, so the present invention should not be interpreted as being limited only to the matters shown in these drawings.

[0019] [Figure 1] 1A is a view schematically illustrating a conventional in-tube according to a comparative example of the present invention, and FIG. 1B is a view schematically illustrating an in-tube according to an embodiment of the present invention. [Figure 2] 1(a) is a schematic cross-sectional view perpendicular to the winding shaft of an electrode assembly according to a comparative example of the present invention, and FIG. 1(b) is a schematic cross-sectional view perpendicular to the winding shaft of an electrode assembly according to an embodiment of the present invention. [Figure 3] 10 is a diagram showing a process in which stress occurs within an electrode assembly due to charging and discharging in a secondary battery including an electrode assembly according to a comparative example of the present invention, and deformation of the mandrel portion occurs while the force of outward expansion is suppressed by the battery can. [Figure 4] 1 is a view showing an electrode of an electrode assembly according to an embodiment of the present invention before being wound up; [Figure 5] 1 is a view showing an electrode assembly according to an embodiment of the present invention; [Figure 6] 1 is a schematic diagram illustrating a negative electrode and a positive electrode of an electrode assembly according to an embodiment of the present invention. [Figure 7] 1 is a diagram showing a schematic configuration of a battery pack including a secondary battery according to an embodiment of the present invention; [Figure 8] 1 is a diagram showing a schematic configuration of a vehicle including a battery pack according to an embodiment of the present invention. [Figure 9] 10 is a diagram showing a problem that occurs when the in-tab is provided so as to surround less than 50% of the surface facing the mandrel portion. [Figure 10] 10 is a diagram showing a problem that occurs when the in-tab is provided so as to surround less than 50% of the surface facing the mandrel portion. [Explanation of symbols]

[0020] 1...electrode assembly 1' Conventional electrode assembly 2...Secondary battery 3 Battery pack 4-pack housing 5. Automobiles 10...Positive electrode 11 Positive middle tab 11' Conventional positive middle tab 12: End portion located at the positive electrode mandrel portion 12': End located at the conventional positive electrode mandrel portion 13: End portion located on the outer periphery of the positive electrode 13': Conventional end located on the outer periphery of the positive electrode 14...Cathode active material layer 15 Positive electrode uncoated area 30...Negative electrode 31 Negative electrode insert 31' Conventional negative electrode in-tube 32 Negative electrode outer tab 32' Conventional negative electrode outer tab 33 Negative electrode tab 34: End portion located at the negative electrode mandrel portion 34'....End located at conventional negative electrode mandrel portion 35: End portion located on the outer periphery of the negative electrode 35' Conventional end located on the outer periphery of the negative electrode 36...Negative electrode active material layer 37 Negative electrode uncoated area 38 Both ends of the electrode assembly winding shaft in the vertical direction 40: Surface facing the mandrel 41R: Surrounding area of ​​mandrel 51R: Surrounding portion of electrode assembly 31W ···In-tab width 31T ···Intab thickness 311...Protrusion 312 Recess I Core O Outermost part C: Electrode assembly winding shaft P: Perpendicular to the winding axis of the electrode assembly DETAILED DESCRIPTION OF THE INVENTION

[0021] The terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best describe his or her invention.

[0022] The terms used in this specification are used only to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0023] In this specification, terms such as "comprise," "include," or "have" are intended to describe the presence of certain components, and do not preclude the presence or addition of other components.

[0024] Furthermore, terms such as "unit" and "device" used in the specification refer to a unit that processes at least one function or operation.

[0025] In this specification, the expression "existing on" a particular component is intended to express that the component is on one side of the particular component, and is not intended to limit the hierarchical relationship. It is also not limited to being in physical contact with the component, and means that there may be other components between the component and the component.

[0026] In this specification, the term "mandrel portion" refers to an empty space provided at the innermost part of the electrode assembly, in which a jelly-roll-shaped electrode assembly is wound around a mandrel.

[0027] In this specification, the term "in-tab" refers to a tab provided at one end of an electrode assembly in a direction perpendicular to the winding axis, the end being located at a mandrel portion.

[0028] The embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not fully represent the technical ideas of the present invention, so it should be understood that there may be various equivalents and modifications that can replace them at the time of this application.

[0029] To facilitate understanding of the invention, the accompanying drawings may not be drawn to scale, and the dimensions of some components may be exaggerated. Also, the same reference numerals are used to refer to the same components in different embodiments.

[0030] An embodiment of the present invention will now be described with reference to the drawings.

[0031] One embodiment of the present invention provides an electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are stacked and wound, wherein the negative electrode includes an in-tab provided at one end of the electrode assembly in a direction perpendicular to a winding axis, the end being located at a mandrel portion, and the in-tab is provided to surround at least 50% of a surface of the negative electrode facing the mandrel portion.

[0032] The mandrel portion is provided at the innermost part of the electrode assembly and refers to an empty space provided when the jelly-roll-shaped electrode assembly is wound around the mandrel. The empty space may be cylindrical.

[0033] The surface facing the mandrel portion means a surface that directly contacts the mandrel portion.

[0034] FIG. 4 is a view showing an electrode of an electrode assembly according to an embodiment of the present invention before being wound up, and FIG. 5 is a view showing an electrode assembly according to an embodiment of the present invention.

[0035] 4 and 5, the in-tab 31 may be a tab provided at one end of the electrode assembly 1 in a direction perpendicular to the winding axis, the end being located at the mandrel portion.

[0036] According to one embodiment, the in-tab 31 may be one continuous tab that surrounds 50% or more of the surface 40 of the negative electrode that faces the mandrel portion.

[0037] The surface 40 of the negative electrode facing the mandrel portion refers to the shaded portion in Figure 4, and means, for example, the surface facing the mandrel portion so as to surround the peripheral portion 41R of the mandrel portion of the electrode assembly 1.

[0038] The surface 40 of the negative electrode facing the mandrel portion may be provided in a non-coating portion 37 of the negative electrode where no electrode active material layer is provided.

[0039] 100% of the surface 40 of the negative electrode facing the mandrel portion may surround the peripheral portion 41R of the mandrel portion of the electrode assembly 1 100%.

[0040] The end of the electrode assembly positioned at the mandrel portion in a direction perpendicular to the winding axis may be provided at the innermost mandrel portion of the electrode assembly.

[0041] The inner tab 31 is provided to surround at least 50% of the surface 40 of the negative electrode 30 facing the mandrel portion, thereby increasing the internal rigidity of the mandrel portion and thereby preventing expansion stress from acting on the mandrel portion within the electrode assembly 1. This prevents deformation of the mandrel portion of the electrode assembly 1 and the occurrence of short circuits due to damage to the separator, which is advantageous for ensuring battery stability.

[0042] FIG. 1(a) is a diagram schematically illustrating a conventional in-tub 31' according to a comparative example of the present invention, and FIG. 1(b) is a diagram schematically illustrating a negative electrode in-tub 31 according to an embodiment of the present invention.

[0043] Referring to Figures 1(a) and (b), the conventional in-tab 31' according to the comparative example of the present invention is relatively narrower than the in-tab 31 according to the embodiment of the present invention, and the tab cannot be provided to surround more than 50% of the surface facing the mandrel portion of the negative electrode, making it impossible to prevent expansion stress inside the electrode assembly from acting on the mandrel portion.

[0044] The conventional in-tab 31' is relatively narrower than the in-tab 31 according to an embodiment of the present invention, and therefore cannot surround more than 50% of the surface facing the mandrel of the negative electrode, whether it is provided in the winding axis direction C of the electrode assembly or obliquely wound into a spiral shape. This creates discontinuous sections in the spiral shape, reducing internal rigidity compared to the continuous in-tab 31 according to the present invention and making it difficult to prevent expansion stress inside the electrode assembly from acting on the mandrel. Furthermore, the spiral shape can result in burrs in the discontinuous sections of the tab, which can damage the separator and reduce safety.

[0045] That is, when the electrode assembly has a structure in which it is wound around a mandrel, stress is generated within the electrode assembly as the negative electrode expands and contracts during charging and discharging. The stress generated during charging and discharging is suppressed by the battery can, which suppresses the outward expansion force, and the mandrel, which is an empty space, is deformed by this force. If the deformation of the mandrel is severe, stress may occur, such as the electrode breaking, which may cause a short circuit within the electrode assembly due to damage to the separator.

[0046] 9 and 10 illustrate the problem that occurs when the in-tab 31 surrounds less than 50% of the surface facing the mandrel. Specifically, FIG. 9 illustrates the mandrel deformed after activation and lifespan testing. (a) shows the state where deformation began after activation, and (b) shows the state where deformation deepened after lifespan testing. Furthermore, in the case of a cylindrical battery in which the in-tab 31 surrounds less than 50% of the surface facing the mandrel, heat dissipation issues arise along with the deformation of the mandrel. Specifically, FIG. 10 shows that after battery discharge, the temperature of the mandrel (b) rose by approximately 2-3°C compared to the outer surface (a). In other words, when the in-tab 31 surrounds less than 50% of the surface facing the mandrel, the mandrel is unable to dissipate heat, resulting in an increase in temperature.

[0047] Meanwhile, the inner tab 31 according to an embodiment of the present invention may be provided to surround 50% or more of the surface of the negative electrode facing the mandrel portion, for example, it may be provided continuously to surround the periphery of the mandrel portion of the electrode assembly.

[0048] Since the in-tub 31 is provided to surround 50% or more of the surface facing the mandrel portion, the rigidity of the mandrel portion can be improved, minimizing deformation of the mandrel portion, and the heat trapped in the mandrel portion can be transferred through the in-tub 31, which is a metal body, thereby reducing the temperature of the mandrel portion.

[0049] The surrounding area of ​​the mandrel of the electrode assembly refers to the periphery of the mandrel, which is an empty space around which the jelly-roll-shaped electrode assembly is wound.

[0050] The inner tab 31 is provided to surround at least 50% of the surface of the negative electrode facing the mandrel portion, thereby preventing expansion stress inside the electrode assembly from acting on the mandrel portion, thereby preventing deformation of the mandrel portion of the electrode assembly and preventing short circuits due to damage to the separator, which is advantageous in ensuring battery stability.

[0051] The fact that the inner tab 31 is provided to surround 50% or more of the surface of the negative electrode facing the mandrel portion means that the inner tab 31 is provided continuously to surround the periphery of the mandrel portion of the electrode assembly, meaning that, for example, one inner tab can be provided in a continuous shape to surround 50% or more of the surface facing the mandrel portion.

[0052] In cases where the in-tab 31' is not provided continuously to surround the periphery of the mandrel portion of the electrode assembly, for example, the conventional in-tab 31' may be provided diagonally and then wound around the periphery of the mandrel portion. When the conventional in-tab 31' is wound around the periphery of the mandrel portion, its rigidity may be reduced compared to the in-tab 31 of the present invention. Also, when the in-tab 31' is wound spirally, burrs at the corners of the tab may be positioned on the outer periphery of the mandrel portion, which may result in damage to the separator and other safety issues.

[0053] FIG. 3 is a diagram illustrating a process in which stress occurs inside an electrode assembly due to charging and discharging in a secondary battery including an electrode assembly according to a comparative example of the present invention, and deformation of the mandrel portion occurs as the force of outward expansion is suppressed by the battery can.

[0054] A secondary battery is formed by interposing a separator, which is an insulator, between a positive electrode and a negative electrode, rolling up the electrode assembly in a jelly roll shape, and inserting the electrode assembly into a battery can together with an electrolyte to form a battery.

[0055] The secondary battery may be a cylindrical secondary battery.

[0056] When a jelly-roll-shaped electrode assembly has a structure in which it is wound around a mandrel, stress is generated within the electrode assembly as the negative electrode expands and contracts during charging and discharging of a secondary battery including the electrode assembly. Because the mandrel of the electrode assembly is an empty space, stress generated during charging and discharging is suppressed by the battery can from expanding outward, and the stress is applied internally to the electrode assembly, causing deformation of the mandrel. If the deformation of the mandrel is severe, stress may occur, such as causing the electrodes to break, which may result in a short circuit within the electrode assembly due to damage to the separator.

[0057] In one embodiment of the present invention, the negative electrode includes a current collector and an electrode active material layer provided on the current collector, the current collector including an uncoated portion where the electrode active material layer is not provided, the negative electrode including the uncoated portion at one or more ends in a direction perpendicular to a winding axis of the electrode assembly, and the in-tab is provided in the uncoated portion provided at an end of the uncoated portion located at a mandrel portion of the uncoated portions.

[0058] Referring to FIG. 4, the negative electrode 30 has the in-tab 31 provided in the uncoated portion 37 provided at the end located on the mandrel portion, which provides high conductivity and is advantageous for electrical connection, and also reduces the resistance of the electrode assembly, which is advantageous for energy density.

[0059] According to one embodiment of the present invention, a negative electrode tab 33 may be provided at one or more of both ends of the electrode assembly in a direction perpendicular to the winding axis.

[0060] FIG. 6 is a diagram schematically illustrating a negative electrode and a positive electrode of an electrode assembly according to an embodiment of the present invention.

[0061] 4 and 6, the negative electrode 30 according to an embodiment of the present invention may further include an outer tab 32 provided at one of both ends of the electrode assembly in a direction perpendicular to the winding axis, the outermost end. By including one more outer tab 32 in the negative electrode 30, an effect can be obtained in that the resistance of the electrode assembly decreases as the number of tabs increases.

[0062] As a result, the positive electrode 10 described below may have a free edge shape and a middle tab 11 structure in which the end of the positive electrode current collector and the end of the positive electrode active material layer 14 coincide with each other at the end perpendicular to the winding axis of the electrode assembly.

[0063] In the positive electrode free edge structure, when the electrode assembly is charged and discharged, the negative electrode 30 expands and contracts, which can increase stress at the portion where the free edge of the positive electrode 10 abuts. However, the internal rigidity of the mandrel portion is increased by the in-tab 31 of the negative electrode 30, preventing deformation of the mandrel portion of the electrode assembly 1 and preventing short circuits due to damage to the separator.

[0064] Furthermore, by further including the outer tab 32, the resistance of the electrode assembly 1 can be reduced, thereby increasing the energy density.

[0065] As an example different from one embodiment of the present invention, a structure in which a positive electrode tab is located on a mandrel portion may be employed. An electrode assembly having such a structure typically employs one positive electrode inner tab and one negative electrode outer tab, which reduces the number of tabs compared to the electrode assembly structure according to the present invention, resulting in an increased resistance of the electrode assembly.

[0066] 2(a) is a schematic cross-sectional view perpendicular to the winding shaft of a conventional electrode assembly 1' according to a comparative example of the present invention, and (b) is a schematic cross-sectional view perpendicular to the winding shaft of an electrode assembly 1 according to an embodiment of the present invention. In this case, since the positive electrode has a free edge structure, the negative electrode may expand and contract during charging and discharging of the electrode assembly, which may increase stress at the portion where the positive electrode free edge abuts.

[0067] Referring to FIG. 2(a), the conventional in-tab 31' according to the comparative example of the present invention is relatively thin in width compared to the in-tab 31 according to the embodiment of the present invention, and the tab cannot be provided to surround more than 50% of the surface facing the mandrel portion of the negative electrode, so it is not possible to prevent expansion stress inside the electrode assembly from acting on the mandrel portion.

[0068] The conventional in-tab 31' is relatively narrower than the in-tab 31 according to an embodiment of the present invention, and when it is provided not only in the winding axial direction of the electrode assembly but also obliquely and wound into a spiral shape, discontinuous sections are generated, which reduces internal rigidity compared to the continuous in-tab 31 according to the present invention and makes it impossible to prevent internal expansion stress from acting on the mandrel portion of the conventional electrode assembly 1'. Furthermore, due to the spiral shape, burrs may be present in the discontinuous sections of the tab, which may damage the separator and make the device less safe.

[0069] 2(b), the in-tab 31 according to one embodiment of the present invention is a single continuous tab that surrounds more than 50% of the surface of the negative electrode facing the mandrel portion. This increases the internal rigidity of the mandrel portion, preventing expansion stress within the electrode assembly 1 from acting on the mandrel portion. This prevents deformation of the mandrel portion of the electrode assembly 1 and short circuits due to separator damage, thereby ensuring battery stability. Furthermore, unlike a spiral-shaped tab, the in-tab 31 is continuous and free of burrs, eliminating the risk of separator damage.

[0070] One embodiment of the present invention provides an electrode assembly 1, wherein the in-tub 31 is provided to surround 70% or more of the surface 40 facing the mandrel portion. Specifically, the in-tub 31 may be provided to surround 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more of the surface 40 facing the mandrel portion. The in-tub 31 may be provided to surround 100% or less of the surface 40 facing the mandrel portion.

[0071] Within this range, the inner tab 31 can maintain rigidity and prevent expansion stress inside the electrode assembly 1 from acting on the mandrel portion, thereby preventing deformation of the mandrel portion of the electrode assembly 1 and preventing short circuits due to damage to the separator, thereby ensuring battery stability.

[0072] In one embodiment of the present invention, the width of the in-tab is 80% or more and 100% or less of the length of the peripheral part of the mandrel part.

[0073] 4 and 5, the width 31W of the in-tab means the length of the in-tab in a direction perpendicular to the winding axis of the electrode assembly.

[0074] The peripheral portion 41R of the mandrel portion refers to the periphery of the mandrel portion, which is an empty space around which the jelly-roll-shaped electrode assembly is wound.

[0075] The width 31W of the in-tab may be 85% or more, 90% or more, or 95% or more of the length of the surrounding portion 41R of the mandrel portion. The width of the in-tab may be 100% or less of the length of the surrounding portion of the mandrel portion.

[0076] When the width 31W of the inner tab satisfies this range, the inner tab 31 is disposed to surround the peripheral portion 41R of the mandrel portion of the negative electrode, increasing the internal rigidity of the mandrel portion and thereby preventing expansion stress from the inside of the electrode assembly from acting on the mandrel portion, thereby preventing deformation of the mandrel portion of the electrode assembly and the occurrence of short circuits due to damage to the separator, which is advantageous for ensuring battery stability.

[0077] In one embodiment of the present invention, the width of the inner tab is 15% to 20% of the length of the peripheral portion of the electrode assembly.

[0078] The peripheral portion 51R of the electrode assembly means a peripheral portion of the end portion of the electrode assembly 1 in the winding axis direction.

[0079] The width 31W of the inner tab may be 15.5% or more, or 16% or more, of the length of the peripheral portion 51R of the electrode assembly. The width 31W of the inner tab may be 19.5% or less, 19% or less, 18.5% or less, or 18% or less of the length of the peripheral portion 51R of the electrode assembly.

[0080] When this range is satisfied, the inner tab 31 is provided to surround the peripheral portion 41R of the mandrel portion of the negative electrode, and the internal rigidity of the mandrel portion can be increased, thereby preventing expansion stress inside the electrode assembly 1 from acting on the mandrel portion.

[0081] In one embodiment of the present invention, the length of the inner tab 31 extending in a direction perpendicular to the winding axis of the electrode assembly is 10 mm to 12 mm.

[0082] The length of the in-tub extended in a direction perpendicular to the winding axis of the electrode assembly may be the width 31W of the in-tub.

[0083] The length of the in-tab 31, extending in a direction perpendicular to the winding shaft of the electrode assembly, may be 10.3 mm or more, 10.6 mm or more, or 10.9 mm or more.The length of the in-tab 31, extending in a direction perpendicular to the winding shaft of the electrode assembly, may be 11.7 mm or less, 11.4 mm or less, or 11.1 mm or less.

[0084] When this range is satisfied, the inner tab 31 is provided to surround the peripheral portion 41R of the mandrel portion of the negative electrode, which increases the internal rigidity of the mandrel portion and thereby prevents expansion stress from acting on the mandrel portion within the electrode assembly 1. This prevents deformation of the mandrel portion of the electrode assembly 1 and the occurrence of short circuits due to damage to the separator, which is advantageous for ensuring battery stability.

[0085] In one embodiment of the present invention, the thickness of the inner tab is 100 μm or more.

[0086] 2, the thickness 31T of the inner tab may be 110 μm or more, 120 μm or more, 130 μm or more, or 140 μm or more. The thickness of the inner tab may be 200 μm or less, 190 μm or less, 180 μm or less, or 170 μm or less.

[0087] When the thickness satisfies this range, the inner tab 31 can increase the internal rigidity of the mandrel portion, thereby preventing expansion stress inside the electrode assembly 1 from acting on the mandrel portion. This prevents deformation of the mandrel portion of the electrode assembly 1 and prevents short circuits caused by damage to the separator, which is advantageous for ensuring battery stability. In addition, because the inner tab 31 has appropriate rigidity within this thickness range, it can be easily wound in the winding process of the electrode assembly.

[0088] One embodiment of the present invention provides an electrode assembly, wherein the inner tab has a thermal conductivity of 90 W / (m·K) or more.

[0089] The thermal conductivity is the difference in the degree to which heat is transferred from one side to another, and refers to the inherent property of a material that indicates heat transfer. The thermal conductivity (k) can be measured by the following equation (1) under the conditions of 1 atmosphere and 293K (=20°C):

[0090] P=k×A(△T / L)-Equation (1) P=Heat flow rate (W) A = sample area (m 2 ) L = sample thickness (m) △T = temperature difference (K or °C)

[0091] The inner tab may have a thermal conductivity of 91 W / (m·K) or more, 100 W / (m·K) or more, 200 W / (m·K) or more, 300 W / (m·K) or more, or 400 W / (m·K) or more. The inner tab may have a thermal conductivity of 450 W / (m·K) or less, 430 W / (m·K) or less, 410 W / (m·K) or less, or 405 W / (m·K) or less.

[0092] The inner tab may contain at least one of copper and nickel, as described below, and in this case, the thermal conductivity of the copper may be 401 W / (m·K) and the thermal conductivity of the Ni may be 91 W / (m·K).

[0093] The in-tab may be provided as a clad tab in which a copper layer containing copper and a nickel layer containing nickel are bonded together. In this case, heat generated in the electrode assembly can be transferred from the copper layer, which has good thermal conductivity, and has a thermal conductivity similar to that of copper, which is advantageous for heat conduction.

[0094] 1(a) and 1(b), the conventional in-tub 31' according to the comparative example of the present invention is relatively narrower than the in-tub 31 according to the embodiment of the present invention, and therefore may have lower thermal conductivity than the in-tub 31 according to the embodiment of the present invention, not only when it is provided in the winding axial direction of the electrode assembly 1 but also when it is provided obliquely and wound into a spiral shape. Specifically, the conventional in-tub 31' is relatively narrow or has discontinuous sections in the spiral shape, so heat is transferred only in the narrow or spiral direction compared to the continuous in-tub 31 according to the present invention, but the in-tub 31 according to the embodiment of the present invention is advantageous in terms of heat transfer because heat can be transferred in any 2D direction.

[0095] In one embodiment of the present invention, the in-tab contains at least one of copper and nickel.

[0096] The in-tab may contain copper. The in-tab may contain copper in an amount of 50% to 100% based on the total amount (100%).

[0097] The in-tab may contain nickel. The in-tab may contain nickel in an amount of 0% to 50% based on the total amount (100%).

[0098] The in-tub may be provided as a clad tub to which a copper layer containing copper and a nickel layer containing nickel are bonded.

[0099] The in-tube containing the compound may be more advantageous in terms of heat conduction of the electrode assembly containing the in-tube.

[0100] In one embodiment of the present invention, the in-tab includes a protrusion on one surface of an end of the electrode assembly in the winding axis direction.

[0101] 4 and 5, the protrusion 311 is a necessary component for welding to a battery can of a secondary battery including the electrode assembly 1. The protrusion 311 is bent and positioned at the center of a mandrel portion, and then welded to the center of the inner bottom surface of the battery can, thereby electrically connecting the inner tab 31 and the battery can.

[0102] The center of the mandrel part refers to the central region of a vertical cross section of the winding shaft of the electrode assembly 1 at the mandrel part, and the center of the inner bottom surface of the battery can refers to the central region of a vertical cross section of the winding shaft of the electrode assembly at the inner bottom surface of the battery can.

[0103] In one embodiment of the present invention, the in-tab includes a recess on the other surface opposite to one surface of the end of the electrode assembly in the winding axis direction.

[0104] The recess 312 is a configuration for convenience in the assembly process, and typically, when attaching the tab 31 to the electrode assembly 1, the tab 31 is cut off to a predetermined length from a rolled-up tab roll and attached. If the protrusion 311 is present according to one embodiment of the present invention, the recess 312 may be unavoidably generated when cutting off the tab to the predetermined length.

[0105] In one embodiment of the present invention, the positive electrode includes a current collector and an electrode active material layer provided on the current collector, and an end of the positive electrode current collector and an end of the positive electrode active material layer coincide with each other at at least one of both ends of the electrode assembly in a direction perpendicular to a winding axis.

[0106] Referring to FIG. 6, the fact that the end of the positive electrode current collector and the end of the positive electrode active material layer 14 coincide with each other at the end of the positive electrode 10 may mean that the positive electrode 10 has a free edge in the electrode assembly 1, and that no uncoated portion 15 is formed at both ends of the positive electrode 10 in a direction P perpendicular to the winding axis of the electrode assembly 1.

[0107] The fact that the end of the positive electrode current collector and the end of the positive electrode active material layer 14 are aligned at the end of the positive electrode 10 means that the lengths of the positive electrode current collector and the positive electrode active material layer 14 are the same at the end of the positive electrode, and in this case, the length of the positive electrode current collector and the length of the positive electrode active material layer 14 may be within a general tolerance range in the industry. For example, the ratio of the length of the positive electrode current collector to the length of the positive electrode active material layer 14 at the end of the positive electrode may be +0.5% or less.

[0108] According to one embodiment, the end of the positive electrode may be provided at a winding start portion of the wound electrode assembly.

[0109] In one embodiment of the present invention, the positive electrode further includes a tab provided at a portion other than both ends in a direction perpendicular to the winding axis of the electrode assembly.

[0110] As described above, the positive electrode has a free edge structure, and therefore, the uncoated portion 15 may not be formed at both ends of the positive electrode in the direction P perpendicular to the winding axis of the electrode assembly.

[0111] As a result, the positive electrode may have a middle tab 11 structure, and the middle tab structure means that the electrode assembly 1 further includes tabs 11 provided at portions other than both ends in a direction P perpendicular to the winding axis. Therefore, both ends of the electrode assembly 1 in a direction P perpendicular to the winding axis may have free edges where no uncoated portion 15 is formed. The middle tab 11 may be provided on the positive electrode uncoated portion 15.

[0112] Referring to FIG. 6, the positive electrode 10 may have a free edge shape and a middle tab 11 structure in which an end of the positive electrode current collector and an end of the positive electrode active material layer 14 coincide with each other at an end perpendicular to the winding axis of the electrode assembly 1.

[0113] In the positive electrode free edge structure, the negative electrode expands and contracts during charge and discharge of the electrode assembly 1, which can increase stress at the portion where the positive electrode free edge abuts. However, the internal tab 31 of the negative electrode 30 increases the internal rigidity of the mandrel portion, preventing deformation of the mandrel portion of the electrode assembly 1 and preventing short circuits due to damage to the separator. In addition, the negative electrode 30 further includes an outer tab 32, which reduces the resistance of the electrode assembly and increases the energy density compared to when the positive electrode 10 and the negative electrode 30 each have one tab.

[0114] One embodiment of the present invention provides a secondary battery including an electrode assembly according to the above embodiment.

[0115] In the present invention, the positive electrode active material coated on the positive electrode plate and the negative electrode active material coated on the negative electrode plate may be any active material known in the art without any limitation.

[0116] Non-limiting examples of the positive electrode active material include conventional positive electrode active materials that can be used for the positive electrodes of conventional electrochemical devices, and in particular, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide that is a combination of these may be used.

[0117] In one example, the positive electrode active material has the general chemical formula A[A x M y ]O 2+z (A includes at least one element selected from Li, Na, and K; M includes at least one element selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Al, Mo, Sc, Zr, Ru, and Cr; x≧0, 1≦x+y≦2, −0.1≦z≦2; and the stoichiometric coefficients of the elements included in x, y, z, and M are selected to maintain electroneutrality of the compound).

[0118] In another example, the positive electrode active material is an alkali metal compound xLiM disclosed in U.S. Pat. No. 6,677,082, U.S. Pat. No. 6,680,143, etc. 1 O2-(1-x)Li2M 2 O3(M 1 contains at least one element having an average oxidation state of 3; M 2 may comprise at least one element having an average oxidation state of 4; 0≦x≦1).

[0119] In still another example, the positive electrode active material has the general chemical formula LiM 1 xFe1-xM 2 yP1-yM 3 zO 4-z (M 1 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, and Al; M 2 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V, and S; M 3 contains halogen elements optionally containing F; <a≦2、0≦x≦1、0≦y<1、0≦z<1;a、x、y、z、M 1 , M 2 , and M 3 wherein the stoichiometric coefficients of the components included are selected so that the compound maintains electroneutrality), or lithium metal phosphate represented by Li3M2(PO4)3, where M comprises at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg, and Al.

[0120] Preferably, the positive electrode active material may include primary particles and / or secondary particles formed by aggregation of the primary particles.

[0121] Non-limiting examples of the negative electrode active material include common negative electrode active materials that can be used in the negative electrodes of conventional electrochemical devices, and in particular, lithium adsorbent materials such as lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, graphite, or other carbons can be used.

[0122] For example, the negative electrode active material may be a carbon material, lithium metal or a lithium metal compound, silicon or a silicon compound, tin or a tin compound, etc. Metal oxides with a potential of less than 2 V, such as TiO2 and SnO2, can also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon.

[0123] Non-limiting examples of the positive electrode current collector include foils made of aluminum, nickel, or a combination thereof, and non-limiting examples of the negative electrode current collector include foils made of copper, gold, nickel, or a copper alloy, or a combination thereof.

[0124] The separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, etc., either alone or in a laminate thereof. As another example, the separator may be a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, etc.

[0125] At least one surface of the separation membrane may include a coating layer of inorganic particles.

[0126] Alternatively, the separator itself may be formed of a coating layer of inorganic particles, and the particles constituting the coating layer may be bound with a binder so that interstitial volume exists between adjacent particles.

[0127] The inorganic particles may be made of an inorganic material having a dielectric constant of 5 or more. Non-limiting examples of the inorganic particles include Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3 (PMN-PT), BaTiO3, hafnia (HfO2), SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, and Y2O3.

[0128] The electrolyte is A + B - The salt may have the following structure: + Li + , Na + , K. + and alkali metal cations such as B - is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO- , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The anion comprises one or more anions selected from the group consisting of:

[0129] The electrolyte may also be dissolved in an organic solvent, such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or a mixture thereof.

[0130] Another embodiment of the present invention provides a battery pack including at least one of the aforementioned secondary batteries.

[0131] The cylindrical secondary battery according to the above-described embodiment may be used to manufacture a battery pack.

[0132] FIG. 7 is a diagram showing a schematic configuration of a battery pack 3 including a secondary battery 2 according to an embodiment of the present invention.

[0133] 7, a battery pack 3 according to an embodiment of the present invention includes an assembly of electrically connected cylindrical secondary batteries and a pack housing 4 that accommodates the assembly. The cylindrical secondary batteries are the secondary batteries 2 according to the above-described embodiment. For ease of illustration, components such as bus bars for electrically connecting the cylindrical secondary batteries, a cooling unit, and external terminals are omitted from the drawing.

[0134] Another embodiment of the present invention provides a vehicle including at least one battery pack as described above.

[0135] The battery pack can be installed in a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may be a four-wheeled vehicle or a two-wheeled vehicle.

[0136] FIG. 8 is a diagram illustrating an automobile 5 including the battery pack 3 of FIG.

[0137] 8, an automobile 5 according to an embodiment of the present invention includes a battery pack 3 according to an embodiment of the present invention. The automobile operates by receiving power from the battery pack 3 according to an embodiment of the present invention.

[0138] Although the present invention has been described above using limited embodiments and drawings, the present invention is not limited thereto, and it is of course possible for a person having ordinary skill in the art to which the present invention pertains to make various modifications and variations within the technical spirit of the present invention and the equivalent scope of the claims set forth below.

Claims

1. An electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are stacked and wound, the negative electrode includes an in-tab provided at an end located at a mandrel portion among both ends of the electrode assembly in a direction perpendicular to the winding shaft, the in-tab is provided so as to surround 50% or more of a surface of the negative electrode facing the mandrel portion, The in-tab includes a recess on one surface opposite to one surface of the end of the electrode assembly in the winding axis direction.

2. the negative electrode includes a current collector and an electrode active material layer provided on the current collector, the current collector includes a plain portion where the electrode active material layer is not provided, 2. The electrode assembly of claim 1, wherein the in-tab is provided in a non-coating portion provided at an end of the negative electrode that is located at a mandrel portion, among both ends of the negative electrode in a direction perpendicular to the winding axis of the electrode assembly.

3. The electrode assembly according to claim 1 , wherein the in-tab is provided so as to surround 70% or more of the surface facing the mandrel portion.

4. The electrode assembly according to claim 1 , wherein the width of the in-tab is 80% to 100% of the length of the peripheral portion of the mandrel portion.

5. The electrode assembly of claim 1 , wherein the width of the in-tab is 15% to 20% of the length of the periphery of the electrode assembly.

6. The electrode assembly of claim 1, wherein the in-tab has a length of 10 mm to 12 mm in a direction perpendicular to the winding axis of the electrode assembly.

7. The electrode assembly of claim 1 , wherein the thickness of the inner tab is 100 μm or more.

8. The electrode assembly according to claim 1 , wherein the inner tab has a thermal conductivity of 90 W / (m·K) or more.

9. The electrode assembly of claim 1 , wherein the in-tab comprises at least one of copper and nickel.

10. The electrode assembly according to claim 1 , wherein the in-tab includes a protrusion on one surface of an end portion of the electrode assembly in the winding axis direction.

11. the positive electrode includes a current collector and an electrode active material layer provided on the current collector, The electrode assembly according to claim 1 , wherein an end of the current collector and an end of the electrode active material layer of the positive electrode coincide with each other at at least one of both ends in a direction perpendicular to the winding axis of the electrode assembly.

12. The electrode assembly according to claim 1 , wherein the positive electrode further includes a tab provided at a portion other than both ends of the electrode assembly in a direction perpendicular to the winding axis.

13. A secondary battery comprising the electrode assembly according to any one of claims 1 to 12.

14. A battery pack comprising the secondary battery according to claim 13.

15. A motor vehicle comprising at least one battery pack according to claim 14.

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