Jelly roll type electrode assembly, secondary battery, battery pack, and automobile

Abstract

The present invention relates to a jelly-roll type electrode assembly, a secondary battery, a battery pack, and an automobile, and more particularly to a jelly-roll type electrode assembly including a separator overlapping portion, a cylindrical secondary battery, a battery pack, and an automobile.

Description

[Technical field]

[0001] The present invention relates to a jelly roll-type electrode assembly, a secondary battery, a battery pack, and an automobile, and more particularly to a jelly roll-type electrode assembly including a separator overlapping portion, a cylindrical secondary battery, a battery pack, and an automobile. This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0184186 filed with the Korean Intellectual Property Office on December 26, 2022, and all contents disclosed in the documents of the Korean patent application are incorporated herein by reference. [Background technology]

[0002] Secondary batteries, which have high ease of application depending on the product group 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) that are driven by electrical sources.

[0003] 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 associated with energy use, and are therefore attracting attention as a new energy source that is environmentally friendly and can improve energy efficiency.

[0004] Currently, the types of secondary batteries that are widely used 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 about 2.5V to 4.5V. Therefore, when a higher output voltage is required, a battery pack may be configured by connecting a plurality of secondary battery cells in series. Also, a battery pack may be configured by connecting a plurality of secondary battery cells in parallel depending on the charge / discharge capacity required for the battery pack. Therefore, the number and electrical connection form of the secondary battery cells included in the battery pack may be variously set depending on the required output voltage and / or charge / discharge capacity.

[0005] Meanwhile, when the form factor of a cylindrical secondary battery cell is increased to apply it to an electric vehicle, a lot of heat is generated during the fast charging process, which may cause the cylindrical secondary battery cell to catch fire. For example, the electrode assembly located in the core part may become more deformable due to contraction / expansion of the electrode assembly during charging / discharging, and if the separator located between the negative and positive electrodes is damaged, the negative and positive electrodes may come into direct contact with each other, resulting in an internal short circuit, which may cause heat generation and fire.

[0006] When the rate at which heat is generated inside a secondary battery cell due to an internal short circuit exceeds the rate at which heat is released to the outside of the secondary battery cell, the temperature of the secondary battery cell begins to rise, and the secondary battery cell in which heat is generated and fire occurs acts as an external heat source, which may lead to an increase in the temperature of adjacent secondary battery cells. When a secondary battery cell reaches a critical temperature, exothermic decomposition of components occurs, and rapid decomposition of the negative electrode material, known as thermal runaway, and rapid exothermic reactions between the electrolyte and the negative electrode material, etc., continue until the reactants are completely depleted.

[0007] If the cap of the secondary battery is separated due to a sudden increase in pressure inside a secondary battery cell where thermal runaway has occurred, flammable and toxic gases may be released; if exhaust is performed at an early stage, the thermal runaway may be accelerated by the oxygen and moisture in the air; and if an unburned electrode assembly is expelled from the battery case before the exothermic reaction is completed, it may spread to adjacent cells, causing secondary ignition and explosion.

[0008] In particular, when an unburned electrode assembly is discharged, metals with excellent electrical conductivity may come into contact with different cells to form an external short circuit. Therefore, if the same phenomenon occurs in some of the secondary battery cells included in a battery module or battery pack including multiple secondary battery cells, there is a problem that the risk of secondary fire and explosion increases significantly.

[0009] Therefore, there is a need to develop a technology that can suppress heat generation and ignition due to an internal short circuit and prevent the problem of unburned electrode assemblies being ejected from the battery case and spreading to adjacent cells in the event of thermal runaway. Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a jelly-roll type electrode assembly, a secondary battery, a battery pack, and an automobile, in which the design of the jelly-roll type electrode assembly is modified.

[0011] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0012] One embodiment of the present invention provides a jelly roll type electrode assembly in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound up, the positive electrode having a first surface in the direction of the winding axis of the jelly roll type electrode assembly and a second surface opposite the first surface, and a separator overlapping portion is included in a core portion of the electrode assembly between the positive electrode and the negative electrode facing the first surface of the positive electrode, or between the positive electrode and the negative electrode facing the second surface of the positive electrode, and the core portion of the electrode assembly includes a hollow having a diameter of 5 mm or more and 7.5 mm or less.

[0013] Another embodiment of the present invention provides a secondary battery including the electrode assembly; a positive electrode terminal having a rivet structure; and a sealing body, wherein the electrode assembly is housed inside a battery case, the negative electrode and the battery case are electrically connected, the positive electrode and the positive electrode terminal are electrically connected, and the sealing body seals an open end of the battery case so as to be insulated from the battery case.

[0014] Yet another embodiment of the present invention provides a battery pack including at least one of the secondary batteries, and a vehicle including at least one of the battery packs. Effect of the Invention

[0015] A jelly roll type electrode assembly according to an embodiment of the present invention includes a separator overlapping portion having a modified folding structure of a core separator, thereby preventing damage to the negative electrode and separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes during charging / discharging of the battery. Even if the separator is damaged, the separator overlapping portion prevents internal short circuits between the positive and negative electrodes, thereby improving the stability and life characteristics of the battery.

[0016] In addition, in a secondary battery according to an embodiment of the present invention, even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery, the separator overlapping portion prevents an internal short circuit between the positive and negative electrodes, thereby improving the stability and life characteristics of the battery. Also, even when thermal runaway occurs due to an internal short circuit, a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell can be prevented.

[0017] A battery pack and a vehicle according to an embodiment of the present invention can suppress heat generation and fire caused by an internal short circuit in a secondary battery cell, and can prevent a problem in which an unburned electrode assembly is ejected from a battery case and spreads to an adjacent secondary battery cell even when thermal runaway occurs in each secondary battery cell, thereby improving stability.

[0018] The effects of the present invention are not limited to those described above, and effects not mentioned herein will be apparent to those skilled in the art from the present specification and the accompanying drawings. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a jelly roll type electrode assembly according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a cross section and a core portion of a jelly roll-type electrode assembly according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram illustrating a core portion including a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing a secondary battery according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a vertical sectional view of the secondary battery of FIG. [Figure 6] 1 is a longitudinal sectional view showing a schematic configuration of a secondary battery according to an embodiment of the present invention. [Figure 7] 1 is a longitudinal sectional view showing a schematic configuration of a secondary battery according to an embodiment of the present invention. [Figure 8] 1 is a longitudinal sectional view showing a schematic configuration of a secondary battery according to an embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing an exemplary configuration of a negative current collector according to one embodiment of the present invention. [Figure 10] FIG. 1 illustrates a battery pack according to one embodiment of the present invention. [Figure 11] FIG. 1 illustrates a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Throughout this specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, but not to the exclusion of other elements, unless specifically stated to the contrary.

[0021] Throughout this specification, when a member is said to be "on" another member, this includes not only when the member is in contact with the other member, but also when there is another member between the two members.

[0022] One embodiment of the present invention is a jelly roll type electrode assembly in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound, the positive electrode including a first surface in a winding axis direction of the jelly roll type electrode assembly and a second surface opposite to the first surface, The present invention provides a jelly roll type electrode assembly, comprising: a separator overlapping portion in a core portion of the electrode assembly, between the positive electrode and the negative electrode facing a first surface of the positive electrode; or between the positive electrode and the negative electrode facing a second surface of the positive electrode; and the core portion of the electrode assembly includes a hollow having a diameter of 5 mm or more and 7.5 mm or less.

[0023] Here, the "core portion" refers to a hollow portion located on the winding shaft of the electrode assembly and a region including a part of the wound positive electrode / separator / negative electrode laminated structure, and may refer to a region of the laminated structure located at the innermost position of the electrode assembly, within two turns of the positive electrode from one end of the positive electrode in the longitudinal direction.

[0024] A jelly roll type electrode assembly according to an embodiment of the present invention includes a separator overlapping portion having a modified folding structure of a core separator, thereby preventing damage to the negative electrode and separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes during charging / discharging of the battery. Even if the separator is damaged, the separator overlapping portion prevents internal short circuits between the positive and negative electrodes, thereby improving the stability and life characteristics of the battery.

[0025] In addition, in a secondary battery according to an embodiment of the present invention, even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery, the separator overlapping portion prevents an internal short circuit between the positive and negative electrodes, thereby improving the stability and life characteristics of the battery. Also, even when thermal runaway occurs due to an internal short circuit, a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell can be prevented.

[0026] Figures 1 and 2 are diagrams showing a jelly-roll type electrode assembly according to an embodiment of the present invention. Specifically, Figure 1 is a diagram showing a jelly-roll type electrode assembly according to an embodiment of the present invention, and Figure 2 is a diagram showing a cross section and a core part of the jelly-roll type electrode assembly according to an embodiment of the present invention. More specifically, Figure 2(a) is a cross section of the jelly-roll type electrode assembly of Figure 1, and Figure 2(b) is a diagram showing a core part including a step part of the electrode assembly.

[0027] According to one embodiment of the present invention, in the core portion of the electrode assembly, the negative electrode and the separator may extend longer than the longitudinal end portion of the positive electrode and be further wound. Specifically, referring to FIG. 1 and FIG. 2, the negative electrode 110' and the separator 200' may extend longer than the longitudinal end portion 310e of the positive electrode and be further wound. That is, the negative electrode 110' and the separator 200' may be wound up together with the positive electrode 310 after being wound up to a predetermined length. For example, the negative electrode 110' and the separator 200' may be wound up together with the positive electrode 310 after being wound up around a winding core for one or more turns.

[0028] That is, in the core part (C) of the jelly roll type electrode assembly, the longitudinal ends of the negative electrode 110 and the separator 200 may be located inside the longitudinal end 310e of the positive electrode. In other words, the length and width of the negative electrode may be greater than those of the positive electrode, and the length and width of the separator located on one side and the opposite side of the negative electrode may also be greater than those of the positive electrode.

[0029] When the negative electrode and the separator are extended beyond the longitudinal end of the positive electrode and further wound up, the lithium ions of the positive electrode can be more easily transferred to the negative electrode in the chemical reaction of the lithium ion battery. When the negative electrode is formed to be longer or wider, the area of ​​the negative electrode that receives the lithium ions increases, preventing a decrease in charge / discharge efficiency and providing excellent stability and life characteristics of the battery.

[0030] According to an embodiment of the present invention, the core part of the electrode assembly may include a step part, which is a region where the negative electrode covers the longitudinal end of the positive electrode. Specifically, referring to FIG. 2(b), the step part 400 may refer to a region where the negative electrode 110 of the core part (C) covers the longitudinal end 310e where the winding of the positive electrode begins, that is, a region where a step is formed due to the thickness (T) of the longitudinal end of the positive electrode. The step part 400 may be a region where the negative electrode 110 covers the longitudinal end 310e of the positive electrode, and a space (H3) on the side of the longitudinal end of the positive electrode is open due to the thickness (T) of the positive electrode. In this case, the step due to the thickness of the positive electrode forms stress in the opposing negative electrode, and such stress may be concentrated on the surface opposite to the surface facing the positive electrode during charging and discharging, causing a crack in the negative electrode.

[0031] In other words, in the core portion (C) of the electrode assembly 1000, the length of the positive electrode 310 may be shorter than the remaining layers, and an empty space (H3) surrounded by the negative electrode 110 / the end portion 310e of the positive electrode in the longitudinal direction / the negative electrode 110' may be formed. That is, the core portion of the jelly roll type electrode assembly according to an embodiment of the present invention may include a step portion 400 including a region forming a stacked structure of the negative electrode 110' / separator (not shown) / positive electrode 310 / separator (not shown) / negative electrode 110 when wound around the end portion 310e of the positive electrode in the longitudinal direction, and a region forming a stacked structure of the negative electrode 110' / separator (not shown) / empty space (H3) / separator (not shown) / negative electrode 110.

[0032] According to one embodiment of the present invention, the step portion 400 may refer to a region from the longitudinal end 310e of the positive electrode to a point where the negative electrodes 110, 110' are in direct contact with each other, i.e., a region including an empty space (H3) having a predetermined length (L1) depending on the thickness (T) of the positive electrode, and a region including the positive electrode 310, having the same length (L1') as the empty space in the opposite direction from the longitudinal end 310e of the positive electrode. That is, the step portion 400 may refer to a region having a length of L1+L1'=L1+L1=2L1, centered on the longitudinal end 310e of the positive electrode, and may refer to a region having a length of 2L1 from the longitudinal end of the step portion 400, i.e., the point where the negative electrodes 110, 110' are in direct contact with each other, toward the longitudinal end 310 of the positive electrode.

[0033] According to one embodiment of the present invention, the core part of the electrode assembly may include a separator overlapping part between the positive electrode and the negative electrode facing the first surface of the positive electrode, or between the positive electrode and the negative electrode facing the second surface of the positive electrode. When the separator overlapping part is further included between the positive electrode and the negative electrode facing the first surface or the second surface of the positive electrode, damage to the negative electrode and the separator that may occur due to a step of a free edge of the positive electrode and a step mitigation part is prevented, and even if the separator is damaged, an internal short circuit between the positive electrode and the negative electrode is prevented by the separator overlapping part, thereby improving the stability and life characteristics of the battery. In addition, even when thermal runaway occurs due to an internal short circuit, the problem of an unburned electrode assembly being ejected from the battery case and propagating to an adjacent secondary battery cell can be prevented.

[0034] 3 is a diagram showing a stepped portion including a separator overlapping portion of a jelly roll type electrode assembly according to an embodiment of the present invention. Specifically, (a) of FIG. 3 is a diagram showing a stepped portion 400 including a separator overlapping portion (S) provided between a positive electrode 310 and a negative electrode 110' facing a first surface of the positive electrode, and (b) of FIG. 3 is a diagram showing a separator overlapping portion (S) provided between a positive electrode 310 and a negative electrode 110 facing a second surface of the positive electrode.

[0035] According to one embodiment of the present invention, in the core portion of the electrode assembly, the separator may extend longer than the longitudinal end portion of the negative electrode and be further wound. Specifically, referring to Fig. 3, the separator 200' extending from the longitudinal end portion of the negative electrode 110' and further wound is folded back toward the longitudinal end portion 310e of the positive electrode, thereby forming the separator overlap portion (S) with a simple folding structure without the need for a separate additional separator. That is, the separator overlap portion (S) may include the separator 200 and the separator 200' extending, further wound, and folded.

[0036] Here, the "separator overlapping portion" may refer to a region from the longitudinal end 310e of the positive electrode to one longitudinal end of the additional overlapping separator 200' included in the separator overlapping portion (S), and may refer to a region having a longitudinal length L2, where L2 is the separation distance between the longitudinal end of the separator overlapping portion and the longitudinal end 310e of the positive electrode.

[0037] According to one embodiment of the present invention, the separator overlapping portion may be provided between the positive electrode and the negative electrode facing the first surface of the positive electrode. When the separator overlapping portion is provided in the direction of the first surface of the positive electrode with the longitudinal end of the positive electrode as the center, damage to the negative electrode and the separator facing the first surface of the positive electrode can be more effectively prevented.

[0038] According to one embodiment of the present invention, the separator overlapping portion may be provided between the positive electrode and the negative electrode facing the second surface of the positive electrode. When the separator overlapping portion is provided in the direction of the second surface of the positive electrode with the longitudinal end of the positive electrode as the center, damage to the negative electrode and the separator facing the second surface of the positive electrode can be more effectively prevented.

[0039] According to one embodiment of the present invention, the core part of the electrode assembly may include a hollow having a diameter of 5 mm to 7.5 mm. Specifically, referring to Fig. 1, the core part (C) of the electrode assembly 1000 may include a hollow (H1) having a diameter of 5 mm to 7 mm, 5 mm to 6.5 mm, 5 mm to 6 mm, 5.5 mm to 7 mm, 6 mm to 7 mm, or 5.5 mm to 6.5 mm. For example, the diameter (Φ1) of the core part hollow (H1) may be 6 mm.

[0040] According to one embodiment of the present invention, the diameter of the hollow core portion may be 10% or more and 17% or less based on 100% of the cross-sectional diameter (Φ2) of the electrode assembly 1000 perpendicular to the winding shaft. Specifically, referring to FIG. 2(a), the diameter (Φ1) of the hollow core portion (H1) may be 10% or more, 10.5% or more, 11% or more, 11.5% or more, 12% or more, or 12.5% ​​or more based on 100% of the cross-sectional diameter (Φ2) of the electrode assembly 1000 perpendicular to the winding shaft, and may be 17% or less, 16.5% or less, 16% or less, 15% or less, or 14.5% or less. For example, the diameter (Φ1) of the hollow core portion (H1) may be about 13% based on 100% of the cross-sectional diameter (Φ2) of the electrode assembly 1000 perpendicular to the winding shaft.

[0041] Here, the "diameter of the hollow core" may refer to the diameter of an imaginary circle whose radius is the maximum value among the distances from the winding shaft of the electrode assembly to the innermost layer that contacts the hollow of the electrode assembly, and the "diameter of the cross section of the electrode assembly perpendicular to the winding shaft" may refer to the diameter of an imaginary circle whose radius is the minimum value among the distances from the winding shaft of the electrode assembly to the outermost layer of the electrode assembly.

[0042] When the diameter of the winding core is reduced to an appropriate level for winding the electrode assembly, the curvature of the core part (C) of the jelly roll type electrode assembly increases, and the elasticity of the wound electrode assembly, i.e., the elasticity with which the laminate of electrodes and separators tries to stretch from a bent state, can be further increased.

[0043] Such an increase in elasticity results in an increase in the force applied in a direction from the core of the electrode assembly toward the outer peripheral surface of the electrode assembly, i.e., toward a battery case that houses the electrode assembly, which leads to an increase in the frictional force between the anode / separator / cathode laminates provided for each different winding turn of the wound electrode assembly.

[0044] When the frictional force between the laminates increases, the phenomenon of the electrode assembly trying to unravel from the core portion is reduced, and the phenomenon of the electrode assembly being ejected through the open end of the battery case during thermal runaway, i.e., the phenomenon of ejection from the core portion of the electrode assembly due to internal pressure when at least a portion of the sealing body sealing the open portion of the battery case is removed, can be suppressed.

[0045] In addition, the frictional force between the laminates can be further increased by including a separator overlapping portion in the core portion of the electrode assembly between the positive electrode and the negative electrode facing a first surface of the positive electrode, or between the positive electrode and the negative electrode facing a second surface of the positive electrode. As a result, even when thermal runaway occurs due to an internal short circuit or the like, it is possible to prevent a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell.

[0046] On the other hand, the elasticity can be further reduced when the form factor of the manufactured secondary battery is increased to apply it to automobiles, etc. In particular, in the case of a secondary battery with an increased form factor, it is necessary to ensure the rigidity of the winding core to support the increasing weight of the electrode assembly, and when the diameter of the winding core is increased to ensure the rigidity of the winding core, the diameter of the core hollow (H1) may also increase. As the diameter of the core hollow (H1) increases, the tension of the core part (C) decreases, so that when the electrode assembly is housed inside a battery case and the open part of the battery case is sealed with a sealing body, a jumping up phenomenon of the core electrode assembly may occur.

[0047] Furthermore, when the core electrode assembly jumps up and thermal runaway occurs, the time it takes for the electrode assembly to be ejected from the battery case, i.e., the burn duration time, is shortened, and an unburned electrode assembly may be ejected, which may significantly increase the risk of secondary fire and explosion in adjacent secondary battery cells.

[0048] Here, the "burn duration time" may refer to the time from when thermal runaway occurs, i.e., when at least a part of the sealing body sealing the open part of the battery case is removed, to when an explosion (premature lid pop) occurs due to internal pressure, to when the electrode assembly is discharged or finished, and if it exceeds about 100 ms, it can be determined as pass.

[0049] Therefore, by adjusting the diameter of the hollow core of the electrode assembly within the above-mentioned range, the rigidity of the winding core and the frictional force between the laminates can be adjusted to an appropriate range even in a secondary battery having an increased form factor, and the problem of unburned electrode assembly being ejected from the battery case and propagating to an adjacent secondary battery cell when thermal runaway occurs due to an internal short circuit or the like can be prevented.

[0050] According to one embodiment of the present invention, the separator overlapping portion may be arranged with the separator overlapped three times. If the separator overlapping is less than three times, the effect of preventing damage to the negative electrode and the separator is poor, and if it exceeds three times, stress may be concentrated in the corresponding area due to the formation of additional steps, causing additional damage to the separator, and local problems such as lithium precipitation due to insufficient electrolyte may occur. When the separators overlapping are three times, a manufacturing process using conventional winding equipment is possible without additional equipment modification, and the provision of the separator overlapping portion can be made even easier.

[0051] According to one embodiment of the present invention, the length of the separator overlapping portion in the length direction may be 100% or more and 300% or less based on 100% of the circumference of the inner circumferential surface of the electrode assembly. Specifically, the length of the separator overlapping portion in the length direction may be 100% or more, 150% or more, or 200% or more, or 300% or less, 250% or less, or 200% or less based on 100% of the circumference of the inner circumferential surface of the electrode assembly, and may be 1 turn or more and 3 turns or less on the inner circumferential surface of the core part of the electrode assembly. That is, the separator overlapping portion may be disposed between the positive electrode and the negative electrode facing a first surface of the positive electrode; or between the positive electrode and the negative electrode facing a second surface of the positive electrode, for 1 turn or more and 3 turns or less.

[0052] Here, the "inner circumferential surface" refers to an imaginary circle having a radius that is the largest value among the distances from the winding shaft of the electrode assembly to the innermost layer that contacts the hollow of the electrode assembly, and the "perimeter of the inner circumferential surface" refers to the perimeter of the imaginary circle. Also, referring to FIG. 3, the length (L2) of the separator overlapping portion in the longitudinal direction may refer to the separation distance between the longitudinal end of the separator overlapping portion and the longitudinal end 310e of the positive electrode.

[0053] According to one embodiment of the present invention, the separation distance between the longitudinal end of the separator overlapping portion and the longitudinal end of the positive electrode may be 20 mm or more and 50 mm or less. Specifically, referring to FIG. 3, the separation distance (L2) between the longitudinal end of the separator overlapping portion (S) and the longitudinal end 310e of the positive electrode may be 20 mm or more, 28 mm or more, or 32 mm or more, and may be 50 mm or less, 44 mm or less, or 38 mm or less. That is, the separator overlapping portion may be disposed between the positive electrode and the negative electrode facing the first surface of the positive electrode, or between the positive electrode and the negative electrode facing the second surface of the positive electrode, at a distance of 20 mm or more and 50 mm or less from the longitudinal end 310e of the positive electrode.

[0054] When the length of the separator overlapping part in the longitudinal direction or the distance between the longitudinal end of the separator overlapping part and the longitudinal end of the positive electrode is within the above-mentioned range, the frictional force due to the separator overlapping part is sufficient to prevent a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell when thermal runaway occurs due to an internal short circuit, etc. When the length of the separator overlapping part in the longitudinal direction exceeds the above-mentioned range, lithium ion transfer is excessively hindered due to the increased area of ​​the separator overlapping part, resulting in poor electrochemical properties of the manufactured secondary battery, and when the length of the separator overlapping part in the longitudinal direction does not meet the above-mentioned range, a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell when thermal runaway occurs may occur, resulting in poor stability of the manufactured secondary battery.

[0055] According to an embodiment of the present invention, the jelly roll type electrode assembly may include a plurality of separators. For example, the jelly roll type electrode assembly may have a structure in which a first separator / anode / second separator / cathode are sequentially laminated. The separator 200 separates the anode 110 and the cathode 310 and provides a path for lithium ions to move. Any separator generally used as a separator in a secondary battery may be used without particular limitation. In particular, it is preferable that the separator has low resistance to ion movement of the electrolyte and has excellent electrolyte moisture absorption ability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. In addition, a typical porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, or the like, may be used. The separator may generally have a thickness of 10 μm or more and 20 μm or less, and may be a separator in which the above-mentioned separator material is used as a substrate layer and a slurry containing a ceramic component or a polymeric substance is coated on the substrate layer in order to ensure heat resistance or mechanical strength, or may be selectively used as a single layer or multilayer structure.

[0056] According to an embodiment of the present invention, the separator may include a coating layer provided on both sides of the substrate layer. Specifically, the separator may include a coating layer provided on both sides of the substrate layer, and the friction coefficient may be adjusted by adjusting the components, content, and particle size of the coating layer.

[0057] According to one embodiment of the present invention, the coating layer may include an inorganic component, a binder component, and a lithium salt. By including the above-mentioned components in the separator, the binder for improving adhesion with the electrode and the inorganic component for improving the mechanical strength of the separator are included, but the lithium salt included in the coating layer does not dissolve to cause an increase in internal resistance, and therefore the stability of the cell can be excellent.

[0058] Specifically, the lithium salt may be substantially the same as that contained in the electrolyte of a lithium secondary battery, for example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, and lithium tetraphenylborate.

[0059] The inorganic component is a volatile organic compound that can be used in a range of operating voltages (e.g., Li / Li + There are no particular limitations on the material as long as it does not undergo an oxidation and / or reduction reaction, i.e., an electrochemical reaction, with the positive or negative electrode current collector at a voltage of 0 to 5 V relative to the reference voltage, and does not inhibit electrical conductivity. For example, BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O 3-It may be one or more selected from the group consisting of PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, and TiO2.

[0060] The binder is not particularly limited as long as it exerts a bonding force with the electrodes laminated on the separator and a bonding force between the inorganic component and the lithium salt in the mixed coating layer, and is not easily dissolved in the electrolyte. For example, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate The polyvinyl alcohol may be one or a mixture of two or more selected from the group consisting of PVdF, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide, and preferably PVdF or PVdF-CTFE.

[0061] According to an embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. Specifically, referring to Fig. 3, the positive electrode 310 may include a positive electrode current collector 301 and positive electrode active material layers 302, 303 formed on one or both sides of the positive electrode current collector 301 and including a positive electrode active material. In other words, the positive electrode active material layers 302, 303 are formed on a positive electrode active material coated portion 310b of the positive electrode current collector 301, and a surface on which the positive electrode active material layer is not provided may be referred to as a positive electrode non-coated portion 310a.

[0062] According to an embodiment of the present invention, the positive electrode current collector may include a positive electrode active material-coated portion on which a positive electrode active material is coated, and a positive electrode uncoated portion on which a positive electrode active material is not coated, or may include a tab on the positive electrode uncoated portion. Specifically, the positive electrode 310 may include a positive electrode uncoated portion 310a, or may include a positive electrode tab formed on the positive electrode uncoated portion 310a.

[0063] According to an embodiment of the present invention, the positive electrode 310 may have a positive electrode uncoated portion 310a at one end in the winding axis direction (parallel to the Z-axis). At least a part of the positive electrode uncoated portion 310a may be used as an electrode tab by itself. That is, the positive electrode uncoated portion 310a may function as a positive electrode tab provided on the positive electrode 310. For example, the positive electrode uncoated portion 310a may be provided at an upper portion in the width direction (parallel to the Z-axis) of the electrode assembly 1000 accommodated in the battery case 600. An insulating layer may be further provided at the boundary between the positive electrode uncoated portion 310a and the positive electrode active material coated portion 310b. The insulating layer can prevent short-circuiting of the electrodes even if the separator shrinks.

[0064] According to an embodiment of the present invention, the electrode assembly may include a positive electrode, a separator, and a negative electrode that are stacked and wound, and the positive electrode may include a positive electrode current collector and a positive electrode active material layer that is provided on at least one side of the positive electrode current collector and has a longitudinal end at the same position as the positive electrode current collector. Specifically, referring to FIG. 3, the electrode assembly may include a positive electrode 310, a separator 200, and a negative electrode 110 that are stacked and wound, and the positive electrode 310 may include a positive electrode current collector 301 and positive electrode active material layers 302, 303 that are provided on at least one side of the positive electrode current collector 301 and have a longitudinal end 310e at the same position as the positive electrode current collector 301. In other words, one longitudinal end 310e of the positive electrode may be in the form of a free edge.

[0065] As a result, the area of ​​the unnecessary uncoated portion of the positive electrode current collector can be reduced to ensure economy, and since the slitting process can be performed after the active material layer is formed on the electrode, the roll-to-roll process including the slitting process and the winding process can be performed more efficiently. Here, "the same position" means that the end portions in the length direction are the same, and may include the case where the end portions are formed at substantially the same position due to process errors that may occur in the slitting process, etc.

[0066] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and specifically, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, etc. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, etc.

[0067] The positive electrode current collector may have a thickness of 3 to 50 μm, and may have fine irregularities formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0068] According to one embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+x Mn 2-x O4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M y Lithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦y≦0.3 is satisfied); 2-z M z Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese oxide represented by Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦z≦0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The positive electrode may be Li-metal.

[0069] According to one embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart electrical conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without causing a chemical change in the battery that is constructed. Specifically, the positive electrode conductive material may be graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one or more of these may be used alone or in mixture.

[0070] The positive electrode binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector.Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof, and one or more of these may be used alone or in combination.

[0071] According to an embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. Specifically, referring to Fig. 3, the negative electrode 110 may include a negative electrode current collector 101 and negative electrode active material layers 102, 103 formed on one or both sides of the negative electrode current collector 101 and including a negative electrode active material. In other words, the negative electrode active material layers 102, 103 are formed on a negative electrode active material coated portion 110b of the negative electrode current collector 101, and a surface on which the negative electrode active material layer is not provided may be referred to as a negative electrode uncoated portion 110a.

[0072] According to an embodiment of the present invention, the negative electrode current collector may include a negative electrode active material coated portion where a negative electrode active material layer is formed, and a negative electrode uncoated portion where a negative electrode active material layer is not formed, and may include a tab on the negative electrode uncoated portion. Specifically, the negative electrode current collector 101 may include a negative electrode uncoated portion 110a, and may include a negative electrode tab formed on the negative electrode uncoated portion 110a. Thus, a manufactured electrode assembly may include one or more negative electrode tabs.

[0073] According to an embodiment of the present invention, the negative electrode 110 may have a negative electrode uncoated portion 110a at one end in a width direction (direction parallel to the Z axis) where a negative electrode active material is not applied. At least a part of the negative electrode uncoated portion 110a may be used as an electrode tab by itself. That is, the negative electrode uncoated portion 110a may function as a negative electrode tab provided on the negative electrode 110. For example, the negative electrode uncoated portion 110a may be provided at a lower portion in a width direction (direction parallel to the Z axis) of the electrode assembly 1000 accommodated in the battery case 600.

[0074] According to an embodiment of the present invention, the positive electrode uncoated portion 310a and the negative electrode uncoated portion 110a may be protruding in opposite directions. For example, referring to Fig. 1 and Figs. 5 to 8, the positive electrode uncoated portion 310a may be protruding toward an upper portion in the width direction (direction parallel to the Z axis) of the electrode assembly 1000, and the negative electrode uncoated portion 110a may be protruding toward a lower portion in the width direction (direction parallel to the Z axis) of the electrode assembly 1000. Thus, the positive electrode uncoated portion 310a provided on the positive electrode 310 and the negative electrode uncoated portion 110a provided on the negative electrode 110 may be protruding in opposite directions along the width direction of the electrode assembly 1000, i.e., along the height direction (direction parallel to the Z axis) of the secondary battery 2000.

[0075] According to an embodiment of the present invention, the negative electrode active material layer may include a negative electrode active material including at least one selected from the group consisting of a silicon-based material and a carbon-based material. The negative electrode active material layer may further include a negative electrode conductive material and a negative electrode binder, and the negative electrode active material, the negative electrode conductive material, and the negative electrode binder may be any material used in the art without limitation.

[0076] According to one embodiment of the present invention, the negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has electrical conductivity. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that easily adsorbs carbon, such as copper or nickel, may be used as the negative electrode current collector. The thickness of the negative electrode current collector may be 6 μm or more and 80 μm or less, but is not limited thereto.

[0077] According to one embodiment of the present invention, the negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0078] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0079] Another embodiment of the present invention provides a secondary battery including the electrode assembly; a positive electrode terminal having a rivet structure; and a sealing body, wherein the electrode assembly is housed inside a battery case, the negative electrode and the battery case are electrically connected, the positive electrode and the positive electrode terminal are electrically connected, and the sealing body seals an open portion of the battery case so as to be insulated from the battery case.

[0080] In a secondary battery according to an embodiment of the present invention, even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery, the separator overlapping portion prevents an internal short circuit between the positive and negative electrodes, thereby improving the stability and life characteristics of the battery. Also, even when thermal runaway occurs due to an internal short circuit, a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell can be prevented.

[0081] FIG. 4 is a diagram showing a secondary battery according to one embodiment of the present invention, FIG. 5 is a longitudinal sectional view of the secondary battery of FIG. 4, and FIGS. 6 to 8 are longitudinal sectional views showing a schematic configuration of a secondary battery according to one embodiment of the present invention.

[0082] According to an embodiment of the present invention, the positive terminal may have a rivet structure. Specifically, referring to Fig. 4 to Fig. 6, the rivet structure may include a battery case 600 having one open side, a positive terminal 330 riveted through a through hole (H5) formed in a bottom part 610 of the battery case, and a terminal gasket 340 provided between the positive terminal 330 and the outer circumference of the through hole (H5).

[0083] According to an embodiment of the present invention, the battery case 600 is a cylindrical container having an open side, and may be made of a conductive material such as a metal. The material of the battery case 600 may be, for example, aluminum. The open portion of the battery case 600 having an open side may be defined as an open end. The side (outer periphery) and the top of the battery case 600 may be integrally formed. The other side of the battery case 600 may be a flat surface (parallel to the XY plane), i.e., a bottom 610. The bottom located opposite to the open end may be defined as a closed end. The battery case 600 may accommodate the electrode assembly 1000 through an open portion formed on one side, and may also accommodate an electrolyte.

[0084] According to an embodiment of the present invention, the battery case 600 may be electrically connected to the electrode assembly 1000. For example, the battery case 600 may be electrically connected to the negative electrode 110 of the electrode assembly 1000. In this case, the battery case 600 may have the same polarity as the negative electrode 110.

[0085] According to one embodiment of the present invention, the battery case 600 may include a beading portion 620 pressed into the inside of the battery case 600 in an area adjacent to an open end; and a crimping portion 630 extending and bent into the inside of the battery case 600 to surround and secure an edge of the cap plate 641 together with a sealing gasket 140.

[0086] Specifically, referring to FIGS. 7 and 8, the beading portion 620 may be formed by pressing into the outer periphery of the battery case 600, and may function as a support on which the sealing body 640 is placed, to prevent the electrode assembly 1000, which may have a size corresponding to the width of the battery case 600, from slipping out through an opening formed at one end of the battery case 600.

[0087] The crimping portion 630 may be formed adjacent to the beading portion 620. Specifically, the crimping portion 630 may have an extended and bent shape to surround an outer circumferential surface of a sealing body 640 disposed adjacent to the beading portion 620 and a portion of a negative electrode current collector 120 described below.

[0088] According to an embodiment of the present invention, the sealing body 640 may include a non-polar cap plate 641 and a seal gasket 140 interposed between an edge of the cap plate 641 and an open end of the battery case 600. Specifically, the sealing body 640 may be placed on a beading portion 620 formed on the battery case 600. Also, the sealing body 640 may be fixed by a crimping portion 630. A seal gasket 140 may be interposed between the sealing body 640 and the crimping portion 630 of the battery case 600 to ensure airtightness of the battery case 600.

[0089] According to an embodiment of the present invention, the sealing body 640 may be made of a metal material to ensure rigidity. Also, the sealing body 640 may cover an open end of the battery case 600. In other words, the sealing body 640 may form one side of the secondary battery 2000, i.e., the other side of the bottom 610.

[0090] According to an embodiment of the present invention, the sealing body 640 may seal the open end of the battery case 600 so as to be insulated from the battery case 600. Specifically, even if the sealing body 640 is made of a metal material having electrical conductivity, the sealing body 640 may not have polarity. In other words, the sealing body 640 may be electrically insulated from the battery case 600 functioning as the negative terminal 130 and the positive terminal 330.

[0091] Therefore, the sealing body 640 does not have to function as the positive terminal 330 or the negative terminal 130. Therefore, the sealing body 640 does not need to be electrically connected to the electrode assembly 1000 and the battery case 600, and the material thereof does not necessarily need to be a conductive metal.

[0092] According to one embodiment of the present invention, the cap plate 641 may include a vent portion 641a that ruptures when the internal pressure of the battery case 600 exceeds a threshold value.

[0093] According to an embodiment of the present invention, the positive electrode terminal 330 may be electrically connected to the positive electrode 310. That is, the positive electrode terminal 330 may be electrically connected to the positive electrode 310 and may have a polarity opposite to that of the battery case 600 electrically connected to the negative electrode 110. For example, the positive electrode terminal 330 may have a surface exposed to the outside.

[0094] According to an embodiment of the present invention, the positive electrode terminal 330 may be made of a metal material having electrical conductivity. The positive electrode terminal 330 may, for example, penetrate the center of a closed end, i.e., a bottom 610, formed at one end of the battery case 600. A part of the positive electrode terminal 330 may be exposed to the outside of the battery case 600, and the remaining part may be located inside the battery case 600. The positive electrode terminal 330 may be fixed on the inner surface of the closed end of the battery case 600 by, for example, riveting. The positive electrode terminal 330 may penetrate the insulator 500 and be coupled to the positive electrode uncoated portion 310a provided on the positive electrode current collector 320 or the positive electrode 310. In this case, the positive electrode terminal 330 may have a positive electrode and may be electrically insulated from the battery case 600 functioning as the negative electrode terminal 130.

[0095] The electrical insulation between the positive terminal 330 and the battery case 600 may be achieved in various ways. For example, the insulation may be achieved by interposing a terminal gasket 340 between the positive terminal 330 and the battery case 600. Meanwhile, the insulation may be achieved by forming an insulating coating layer on a part of the positive terminal 330. Alternatively, the positive terminal 330 may be structurally and firmly fixed so that the positive terminal 330 and the battery case 600 are not in contact with each other, or a combination of the above-mentioned methods may be used.

[0096] According to one embodiment of the present invention, the positive terminal 330 may include a body portion 331 inserted into the through hole (H5); an external flange portion 332 extending from one peripheral edge of the body portion 331 exposed through the external surface 610a of the bottom portion 610 along the external surface 610a; and an internal flange portion 333 extending from the other peripheral edge of the body portion 331 exposed through the internal surface 610b of the bottom portion 610 toward the internal surface 610b.

[0097] According to an embodiment of the present invention, the positive terminal 330 may further include a flat portion 331a provided at an end of the body portion 331 exposed through an inner surface 610b of the bottom portion 610. Specifically, the flat portion 331a and the inner surface 610b of the bottom portion 610 of the battery case 600 may be parallel to each other. Here, "parallel" means that they are substantially parallel when observed with the naked eye.

[0098] According to one embodiment of the present invention, the angle (θ) between the inner flange portion 333 and the inner surface 610b of the bottom portion 610 of the battery case 600 may be 0° or more and 60° or less. The size of the angle may be determined according to the caulking strength when the positive terminal 330 is installed in the through hole (H5) of the battery case 600 by a caulking method. For example, as the caulking strength increases, the angle (θ) may decrease to 0°. If the angle exceeds 60°, the sealing effect of the terminal gasket 340 may decrease.

[0099] According to an embodiment of the present invention, a recess may be provided between the inner flange portion 333 and the flat portion 331a. The recess may be formed according to the shape of a caulking jig when the positive electrode terminal 330 is provided in the through hole (H5) of the battery case 600 by a caulking method.

[0100] According to one embodiment of the present invention, the recess may have a cross-sectional structure of an asymmetric groove. For example, the asymmetric groove may be V-shaped. The asymmetric groove may include a sidewall of the flat portion 331a and an inclined surface of the inner flange portion 333 connected to an end of the sidewall, and the sidewall may be substantially perpendicular to the inner surface 610b of the bottom portion 610 of the battery case 600. Here, "perpendicular" means substantially perpendicular when observed with the naked eye.

[0101] According to an embodiment of the present invention, the terminal gasket 340 is interposed between the battery case 600 and the positive terminal 330, and can prevent the battery case 600 and the positive terminal 330 having opposite polarities from contacting each other. That is, the terminal gasket 340 can block the electrical connection between the battery case 600 and the positive terminal 330. As a result, the closed end of the battery case 600 having a flat shape, i.e., the bottom 610, can function as the negative terminal 130 of the secondary battery 2000.

[0102] According to one embodiment of the present invention, the terminal gasket 340 includes an external gasket portion 342 interposed between the external flange portion 332 and the external surface 610a of the bottom portion 610; and an internal gasket portion 341 interposed between the internal flange portion 333 and the internal surface 610b of the bottom portion 610, and the internal gasket portion 341 may extend longer than the internal flange portion 333. Specifically, the internal gasket portion 341 may form an angle of 0° to 60° with the internal surface 610b of the bottom portion 610 of the battery case 600 and extend longer than the internal flange portion 333.

[0103] According to an embodiment of the present invention, the inner gasket part 341 and the outer gasket part 342 may have different thicknesses depending on the positions. For example, the thickness of the inner gasket part 341 may be relatively small in a region between the inner flange part 333 and the inner side of the through hole (H5) connected to the inner surface 610b of the bottom part 610 of the battery case 600. Specifically, a minimum thickness point may be present in a region of the terminal gasket 340 between the inner side of the through hole (H5) and the inner flange part 333.

[0104] According to an embodiment of the present invention, the inside of the through hole (H5) may include a surface facing the inner flange portion 333. Meanwhile, the upper and lower ends of the inner wall of the through hole (H5) perpendicular to the bottom 610 of the battery case 600 may be chamfered to form a tapered surface toward the positive terminal 330, and the upper and / or lower ends of the inner wall of the through hole (H5) may be deformed into a gently curved surface having a curvature. In this case, the stress applied to the terminal gasket 340 near the upper and / or lower ends of the inner wall of the through hole (H5) may be further alleviated.

[0105] According to an embodiment of the present invention, the secondary battery may further include a negative electrode current collector. Specifically, the negative electrode current collector 120 may be coupled to the other end of the electrode assembly 1000 in the width direction. The negative electrode current collector 120 may be made of a metal material having electrical conductivity. The negative electrode current collector 120 may be connected to a negative electrode uncoated portion 110a provided on the negative electrode 110. Also, the negative electrode current collector 120 may be electrically connected to the battery case 600. The negative electrode current collector 120 may be fixed by being interposed between an inner surface of the battery case 600 and a seal gasket 140. Meanwhile, the negative electrode current collector 120 may be welded to an inner wall surface of the battery case 600.

[0106] According to an embodiment of the present invention, the negative electrode current collector 120 may have a plurality of projections and recesses formed radially on one side. When the projections and recesses are formed, the negative electrode current collector 120 may be pressed to press the projections and recesses into the negative electrode uncoated portion 110a.

[0107] The negative current collector 120 may be coupled to one end of the negative uncoated portion 110a in the width direction. The coupling between the negative uncoated portion 110a and the negative current collector 120 may be performed, for example, by laser welding. The laser welding may be performed by partially melting the base material of the negative current collector 120, or may be performed in a state where solder for welding is interposed between the negative current collector 120 and the negative uncoated portion 110a. In this case, it is preferable that the solder has a lower melting point than the negative current collector 120 and the negative uncoated portion 110a. Meanwhile, in addition to laser welding, resistance welding, ultrasonic welding, etc. are possible, but the welding method is not limited thereto.

[0108] According to an embodiment of the present invention, the negative current collector plate 120 may be bonded to a bonding surface formed by bending one end of the negative uncoated portion 110a in a direction parallel to the negative current collector plate 120. The bending direction of the negative uncoated portion 110a may be, for example, a direction toward the core part (C) of the electrode assembly 1000. When the negative uncoated portion 110a has a folded shape, the space occupied by the negative uncoated portion 110a is reduced, thereby improving the energy density. In addition, the increase in the bonding area between the negative uncoated portion 110a and the negative current collector plate 120 may improve the bonding force and reduce the resistance.

[0109] FIG. 9 is a diagram showing an exemplary form of a negative current collector according to one embodiment of the present invention.

[0110] 9, the negative electrode current collector 120 may include a center portion 121 welded to the uncoated portion 110a of the negative electrode 110; a tab connecting portion 122 extending from the center portion 121 and connecting to a negative electrode tab provided on the electrode assembly 1000; and a battery case connecting portion 123 extending from the center portion 121 and positioned between adjacent tab connecting portions 122.

[0111] According to an embodiment of the present invention, the battery case coupling portion 123 may be interposed between the beading portion 620 and the sealing gasket 140 and fixed by the crimping portion 630 .

[0112] According to one embodiment of the present invention, the battery case coupling portion 123 of the negative electrode collector plate 120 may include a contact portion 123a fixed by welding to an inner peripheral surface of the beading portion 620 adjacent to the crimping portion 630; and a connecting portion 123b having at least one bending portion whose extension direction is changed, and connecting between the center portion 121 and the contact portion 123a.

[0113] According to one embodiment of the present invention, the negative current collector plate 120 includes a negative current collector hole (H2) formed at a position corresponding to the core hollow (H1) of the electrode assembly 1000, and a difference between a diameter of the negative current collector hole (H2) and a diameter of the core hollow (H1) of the electrode assembly may be 0.1 mm or more and 1 mm or less. Specifically, a difference between a diameter of the negative current collector hole (H2) and a diameter of the core hollow (H1) of the electrode assembly may be 0.1 mm or more, 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, or 0.5 mm or more, or may be 1 mm or less, 0.9 mm or less, 0.8 mm or less, 0.7 mm or less, or 0.6 mm or less. More specifically, it is preferable that the diameter of the core hollow (H1) is larger than the diameter of the negative electrode current collector hole (H2). For example, the diameter of the core hollow (H1) may be formed to be 5 mm or more and 7.5 mm or less, and the diameter of the negative electrode current collector hole (H2) may be formed to be 0.5 mm or more and 1 mm or less smaller than this.

[0114] When the diameter difference is satisfied, ejection of the electrode assembly during thermal runaway can be prevented and processability can be ensured. Specifically, when the diameter of the core hollow (H1) is reduced, it is advantageous to prevent ejection of the electrode assembly during thermal runaway of the secondary battery. However, as described above, in the case of a secondary battery with an increased form factor, it is necessary to ensure the rigidity of the winding core to support the weight of the electrode assembly which increases accordingly, and when the diameter of the winding core is increased to ensure the rigidity of the winding core, the diameter of the core hollow (H1) may also increase. Meanwhile, when the diameter of the negative current collector plate hole (H2) is too small, injection of electrolyte through the negative current collector plate hole (H2) or welding using a laser welder (CRW) is impossible, resulting in a decrease in processability, and when the diameter of the negative current collector plate hole (H2) is too large, it is disadvantageous to prevent ejection of the electrode assembly during thermal runaway, and the reduction in the bonding area between the negative electrode uncoated portion 110a and the negative current collector plate 120 may result in a decrease in bonding force and an increase in resistance. Meanwhile, if the difference between the diameter of the negative collector plate hole (H2) and the diameter of the core hollow (H1) of the electrode assembly is outside a certain range, the electrode assembly and the negative collector plate may not be easily aligned, which may reduce processability.

[0115] According to an embodiment of the present invention, the secondary battery may further include a positive current collector. Specifically, the positive current collector 320 may be welded to a non-coated portion 310a of the positive electrode 310, and at least a portion of the positive current collector 320 may be welded to a flat portion 331a of the positive terminal 330.

[0116] According to an embodiment of the present invention, the positive current collector 320 may be coupled to one widthwise end of the electrode assembly 1000. Specifically, the positive current collector 320 may be coupled to a positive electrode uncoated portion 310a provided on the positive electrode 310 at one widthwise end of the electrode assembly 1000. The positive current collector 320 may be made of a conductive metal material.

[0117] According to an embodiment of the present invention, the positive electrode current collector plate 320 may have a plurality of projections and recesses formed radially on one side. When the projections and recesses are formed, the positive electrode current collector plate 320 may be pressed to press the projections and recesses into the non-coated portion 310a of the positive electrode 310.

[0118] According to an embodiment of the present invention, the positive electrode uncoated portion 310a and the positive electrode collector plate 320 may be bonded together by, for example, laser welding. The laser welding may be performed by partially melting the base material of the positive electrode collector plate 320, or may be performed with solder for welding interposed between the positive electrode collector plate 320 and the positive electrode uncoated portion 310a. In this case, it is preferable that the solder has a lower melting point than the positive electrode collector plate 320 and the positive electrode uncoated portion 310a. Meanwhile, in addition to laser welding, resistance welding, ultrasonic welding, etc. are possible, but the welding method is not limited thereto.

[0119] According to an embodiment of the present invention, the secondary battery may further include an insulator. Specifically, the insulator 500 may prevent contact between the positive electrode uncoated portion 310a and the battery case 600 and / or contact between the positive electrode current collector plate 320 and the battery case 600. That is, the insulator 500 may be accommodated inside the battery case 600 and configured to cut off electrical connection between the positive electrode uncoated portion 310a and the battery case 600. Therefore, the insulator 500 may be made of a material having insulating properties, and may include, for example, a polymer material.

[0120] According to an embodiment of the present invention, the insulator 500 may be interposed between the positive current collector 320 and an inner surface 610b of the bottom 610 of the battery case 600, and between the inner peripheral surface of the battery case 600 and the electrode assembly 1000. Specifically, the insulator 500 may be provided between one end in the width direction of the electrode assembly 1000 and the inner surface 610b of the bottom 610 of the battery case 600, or between the positive current collector 320 coupled to one end in the width direction of the electrode assembly 1000 and the inner peripheral surface of the battery case 600.

[0121] According to one embodiment of the present invention, the insulator 500 may include a welding hole (H4) that exposes the flat portion 331a of the positive terminal 330 to the positive current collector plate 320 side, and may cover a surface of the positive current collector plate 320 and one edge of the electrode assembly 1000.

[0122] According to an embodiment of the present invention, the secondary battery may be a cylindrical secondary battery. In other words, a battery case in which the jelly-roll type electrode assembly is housed may be cylindrical. The size of the battery case may be a circular diameter of 30 mm to 55 mm at both ends in the width direction and a height of 60 mm to 120 mm. For example, the circular diameter x height of the cylindrical battery case may be 40 mm x 60 mm, 40 mm x 80 mm, 40 mm x 90 mm, or 40 mm x 120 mm. The secondary battery may be a secondary battery cell.

[0123] Preferably, the cylindrical secondary battery cell may be, for example, a cylindrical secondary battery cell having a form factor ratio (defined as the diameter of a cylindrical secondary battery cell divided by its height, i.e., the ratio of the diameter (Φ) to the height (H)) greater than about 0.4.

[0124] Here, the form factor may refer to a value indicating the diameter and height of a cylindrical battery cell. Cylindrical secondary battery cells according to an embodiment of the present invention may be, for example, a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, a 46800 cell, and a 46900 cell. In the value indicating the form factor, the first two digits indicate the diameter of the cell, the next two digits indicate the height of the cell, and the final digit 0 indicates that the cross section of the cell is circular.

[0125] A secondary battery cell according to one embodiment of the present invention may be a cylindrical secondary battery cell having a cylindrical shape with a diameter of about 46 mm, a height of about 110 mm, and a form factor ratio of 0.418.

[0126] A secondary battery cell according to another embodiment may be a cylindrical secondary battery cell having a cylindrical shape with a diameter of about 48 mm, a height of about 75 mm, and a form factor ratio of 0.640.

[0127] A secondary battery cell according to another embodiment may be a cylindrical secondary battery cell having a diameter of about 48 mm, a height of about 110 mm, and a form factor ratio of 0.418.

[0128] A secondary battery cell according to yet another embodiment may be a cylindrical secondary battery cell having a cylindrical shape with a diameter of about 48 mm, a height of about 80 mm, and a form factor ratio of 0.600.

[0129] A secondary battery cell according to yet another embodiment may be a cylindrical secondary battery cell having a cylindrical shape with a diameter of about 46 mm, a height of about 80 mm, and a form factor ratio of 0.575.

[0130] A battery cell according to yet another embodiment may be a cylindrical secondary battery cell having a cylindrical shape with a diameter of about 46 mm, a height of about 90 mm, and a form factor ratio of 0.511.

[0131] Conventionally, battery cells with a form factor ratio of about 0.4 or less have been used. That is, conventionally, for example, 18650 cells, 21700 cells, etc. have been used. In the case of an 18650 cell, its diameter is about 18 mm, its height is about 65 mm, and its form factor ratio is 0.277. In the case of a 21700 cell, its diameter is about 21 mm, its height is about 70 mm, and its form factor ratio is 0.300.

[0132] An embodiment of the present invention provides a battery pack including at least one secondary battery according to the above-described embodiment, and a vehicle including at least one of the battery packs.

[0133] A battery pack and a vehicle according to an embodiment of the present invention can suppress heat generation and fire caused by an internal short circuit in a secondary battery cell, and can prevent a problem in which an unburned electrode assembly is ejected from a battery case and spreads to an adjacent secondary battery cell even when thermal runaway occurs in each secondary battery cell, thereby improving stability.

[0134] The secondary battery according to the above-described embodiment may be used in manufacturing the battery pack.

[0135] 10 is a diagram showing a battery pack according to an embodiment of the present invention, specifically, a schematic configuration of a battery pack including the secondary battery of FIG.

[0136] 10, a battery pack 3000 according to an embodiment of the present invention may include an assembly of electrically connected secondary batteries 2000 and a pack housing 700 that accommodates the secondary batteries 2000. The secondary batteries 2000 may be the secondary battery cells according to the above-described embodiments.

[0137] According to an embodiment of the present invention, the battery pack may further include components such as a bus bar for electrically connecting the secondary battery 2000, a cooling unit, and an external terminal.

[0138] According to an embodiment of the present invention, the battery pack 3000 may be mounted on an automobile 4000. Specifically, the automobile may be an electric automobile, a hybrid automobile, or a plug-in hybrid automobile. The automobile may include a four-wheeled automobile or a two-wheeled automobile.

[0139] Fig. 11 is a diagram showing a vehicle according to an embodiment of the present invention, specifically, Fig. 11 is a diagram showing a schematic configuration of a vehicle including the battery pack of Fig. 10.

[0140] 11, an automobile 4000 according to an embodiment of the present invention may include a battery pack 3000 according to an embodiment of the present invention. The automobile 4000 may be operated by receiving power from the battery pack 3000 according to an embodiment of the present invention. EXAMPLES

[0141] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the present invention. However, the examples according to the present invention may be modified in various different forms, and the scope of the present invention should not be construed as being limited to the following examples. The examples in the present specification are provided to more completely explain the present invention to those having average knowledge in the art.

[0142] <Example 1> (Manufacturing of electrode assemblies) A negative electrode (negative electrode current collector: Cu foil, negative electrode active material: graphite), a separator made of a polyethylene material on which an SRS coating layer was formed, and a positive electrode (positive electrode current collector: Al foil, active material: NCM) were prepared.

[0143] Before winding the jelly roll type electrode assembly, two separators were stacked and a separator extension was provided in the direction opposite to the winding direction, with a length corresponding to two turns of the winding core.

[0144] Then, the first and second separators were folded back in the winding direction at points corresponding to two turns of the winding core from the longitudinal ends thereof to start winding, and the negative and positive electrodes were sequentially inserted to manufacture a jelly roll type electrode assembly.

[0145] Specifically, the core of the jelly roll type electrode assembly has a separator overlapping portion between one side of the positive electrode in the winding axis direction and one side of the negative electrode, with a separator extension portion having a length corresponding to one turn from the longitudinal end of the positive electrode being interposed, thereby having a structure as shown in FIG. 3(a).

[0146] In this case, the hollow diameter of the core part of the electrode assembly was adjusted to 6 mm, the diameter of one end of the electrode assembly perpendicular to the winding shaft was adjusted to 45 mm, and the length of the separator overlap part in the longitudinal direction was adjusted to 20 mm.

[0147] (Secondary battery manufacturing) The manufactured electrode assembly was inserted into a cylindrical battery case (diameter: 45 mm to 47 mm, material: steel) with an opening on one side, and then an electrolyte solution in which ethylene carbonate (EC): ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:70 and LiPF6 was dissolved to a concentration of 1.0 M was poured into the battery case, and the cylindrical battery case was sealed with a seal to manufacture a secondary battery.

[0148] In this case, a rivet structure of the positive terminal is manufactured such that a positive terminal is riveted through a through hole formed in the bottom of the battery case, and a terminal gasket is provided between the positive terminal and the outer diameter of the through hole, so that in a secondary battery including the same, the negative electrode of the electrode assembly is electrically connected to the battery case, the positive electrode is electrically connected to the positive terminal, and the sealed body is insulated from the battery case.

[0149] <Example 2> A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a separator overlapping portion was provided in the core of the jelly-roll type electrode assembly by interposing a separator extension portion having a length corresponding to 1.6 turns from an end of the positive electrode in the longitudinal direction between the separator located on one side of the positive electrode in the winding axis direction and one side of the negative electrode. In this case, the length of the separator overlapping portion in the longitudinal direction was adjusted to about 40 mm.

[0150] <Example 3> A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a separator overlapping portion was provided in the core of the jelly-roll type electrode assembly by interposing a separator extension portion having a length corresponding to 2.0 turns from an end of the positive electrode in the longitudinal direction between the separator located on one side of the positive electrode in the winding axis direction and one side of the negative electrode. In this case, the length of the separator overlapping portion in the longitudinal direction was adjusted to about 50 mm.

[0151] <Reference example 1> A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a separator overlapping portion was provided in the core of the jelly-roll type electrode assembly by interposing a separator extension portion having a length corresponding to 0.4 turns from an end of the positive electrode in the longitudinal direction between the separator located on one side of the positive electrode in the winding axis direction and one side of the negative electrode. In this case, the length of the separator overlapping portion in the longitudinal direction was adjusted to about 10 mm.

[0152] <Reference example 2> A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a separator overlapping portion was provided in the core of the jelly-roll type electrode assembly by interposing a separator extension portion having a length corresponding to 0.6 turns from an end of the positive electrode in the longitudinal direction between the separator located on one side of the positive electrode in the winding axis direction and one side of the negative electrode. In this case, the length of the separator overlapping portion in the longitudinal direction was adjusted to about 15 mm.

[0153] <Comparative Example 1> A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that the diameter of the hollow core of the electrode assembly was adjusted to 8 mm.

[0154] <Experimental Example> (Experimental Example 1 - Appearance Evaluation) The secondary batteries manufactured in Example 1 and Comparative Example 1 were prepared, and the electrode assemblies were housed inside a battery case. Immediately after the opening of the battery case was sealed (vented) with a sealing body, the occurrence of the jumping phenomenon of the core electrode assembly was evaluated using external images and computed tomography (CT) images, and the results are shown in Table 1. Specifically, when the jumping of the core part occurred by 7 mm or more and the core part was observed with the naked eye from the external appearance of the secondary battery cell, it was indicated with "O", and when the jumping of the core part was not observed with the naked eye, it was indicated with "X".

[0155] Referring to Table 1 below, it was confirmed that the secondary battery of Comparative Example 1 had a core part jumping up by about 10 to 20 mm, whereas the secondary battery according to one embodiment of the present invention did not have the core part electrode assembly jumping up.

[0156] As a result, the jelly roll type electrode assembly and secondary battery according to an embodiment of the present invention can improve the stability and life characteristics of the battery by preventing an internal short circuit between the positive and negative electrodes due to the separator overlapping portion even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery. It can also prevent a problem in which an unburned electrode assembly is ejected from the battery case and propagates to an adjacent secondary battery cell when thermal runaway occurs due to an internal short circuit or the like.

[0157] (Experimental Example 2 - Evaluation of the Safety of Secondary Batteries) Secondary batteries manufactured in Examples 1 to 3, Reference Examples 1 and 2, and Comparative Example 1 were prepared, and the safety of the secondary batteries was evaluated by measuring the flame duration time under thermal runaway conditions, and the results are shown in Table 1 below. In this case, the flame duration was measured as the time from when an explosion (premature lid pop) occurs due to internal pressure when at least a part of a sealed body sealing an opening of a battery case is removed until the electrode assembly is discharged or finished. If the flame duration is less than 1000 ms, there is a high possibility that an unburned electrode assembly will be discharged, so it was confirmed whether the flame duration was 1000 ms or more.

[0158] [Table 1-1] [Table 1-2]

[0159] Referring to Table 1, it was confirmed that the secondary batteries of Examples 1 to 3, in which the diameter of the hollow core is 6 mm, have a flame duration time of 1000 ms or more, and thus have a sufficient flame duration without ejection of the electrode assembly when thermal runaway occurs.

[0160] In contrast, it was confirmed that the secondary battery of Comparative Example 1, in which the diameter of the hollow core is 8 mm, sometimes had a flame maintenance time of less than 1000 ms. Specifically, it was confirmed that the secondary battery cells of Comparative Examples 1-5 and 1-6, in which the flame maintenance times were 82 ms and 97 ms, respectively, ejected unburned electrode assemblies when thermal runaway occurred. In addition, it was confirmed that the secondary battery cell of Comparative Example 1-8 had a short flame maintenance time of 250 ms, which was not enough to burn the electrode assembly in which thermal runaway occurred.

[0161] As a result, it can be seen that a secondary battery according to one embodiment of the present invention can prevent a problem in which an unburned electrode assembly is ejected from a battery case and propagates to an adjacent secondary battery cell when thermal runaway occurs due to an internal short circuit, even in a secondary battery having an increased form factor, by adjusting the diameter of the core portion of the electrode assembly within a specific range.

[0162] On the other hand, it was confirmed that in the secondary batteries of Reference Examples 1 and 2, in which the diameter of the hollow core is 6 mm, when the longitudinal length of the separator overlapping portion is adjusted to 0.4 turns and 0.6 turns, respectively, the electrode assembly in which thermal runaway occurs does not have a flame maintenance time sufficient to burn, similar to the secondary battery cells of Reference Examples 1-5 and 2-2, in which the flame maintenance time is 310 ms and 501 ms, respectively.

[0163] As a result, it can be seen that a secondary battery according to one embodiment of the present invention has an excellent effect of preventing a problem in which an unburned electrode assembly is ejected from a battery case and propagates to an adjacent secondary battery cell when thermal runaway occurs due to an internal short circuit or the like, by adjusting the longitudinal length of the separator overlapping portion within a specific range.

[0164] That is, the jelly roll type electrode assembly and secondary battery according to an embodiment of the present invention can improve the stability and life characteristics of the battery by preventing an internal short circuit between the positive and negative electrodes due to the separator overlapping portion even when the electrode assembly is deformed due to the contraction / expansion of the electrodes during charging / discharging of the battery. It can also prevent a problem in which an unburned electrode assembly is ejected from a battery case and propagates to an adjacent secondary battery cell when thermal runaway occurs due to an internal short circuit or the like.

[0165] The above detailed description is illustrative and explanatory of the present invention. Moreover, the above content merely shows and describes preferred embodiments of the present invention, and as stated above, the present invention can be used in various other combinations, modifications, and environments, and changes or modifications can be made within the scope of the inventive concept disclosed herein, the scope of the above disclosure, and / or the skill or knowledge of the art. Therefore, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Moreover, the appended claims should be construed to include other embodiments. [Explanation of symbols]

[0166] 1000...electrode assembly C: Core section H1: Hollow core Φ1: Diameter of hollow core Φ2: Cross-sectional diameter of the electrode assembly perpendicular to the winding shaft 110, 110'...Negative electrode 101...Negative electrode current collector 102, 103...Negative electrode active material layer 110a...Negative electrode plain area 110b...Anode active material coating section 120 Negative current collector plate 121...center 122 Tab joint 123 Battery case connection part 123a...Contact part 123b...Connection part H2: Negative electrode collector plate hole 130...Negative terminal 140 ···Seal gasket 200, 200' separator S: Separator overlapping section 310...Positive electrode 301...Positive electrode current collector 302, 303...Cathode active material layer 310a Positive electrode uncoated area 310b: Positive electrode active material coating section 310e: Positive electrode longitudinal end 320 Positive current collector plate 321...center 330 Positive terminal 331 Body 331A...Flat area 332 External flange portion 333 Internal flange portion 340 Terminal gasket 341 Internal gasket part 342 External gasket part 400 ···Step H3: Free space at the step L1: The separation distance between the longitudinal end of the step and the longitudinal end of the positive electrode T: Thickness of positive electrode L2: Distance between the longitudinal end of the separator overlap and the longitudinal end of the positive electrode 500 ···Insulator H4: Welding hole 600 ···Battery case 610...Bottom 620 Beading section 630 Crimping section 640... Sealed body 641 Cap plate 641a Vent H5...Through hole 700···Pack Housing 2000...Secondary battery 3000 ··· Battery pack 4000 ···Automobiles

Claims

1. A jelly-roll type electrode assembly in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound, The positive electrode includes a first surface in a winding axis direction of the jelly roll type electrode assembly and a second surface opposite to the first surface, a separator overlapping portion is included in a core portion of the electrode assembly between the positive electrode and the negative electrode facing a first surface of the positive electrode, or between the positive electrode and the negative electrode facing a second surface of the positive electrode; A jelly roll type electrode assembly, wherein a core portion of the electrode assembly includes a hollow having a diameter of 5 mm or more and 7.5 mm or less.

2. The jelly roll type electrode assembly according to claim 1 , wherein the separator overlapping portion is formed by overlapping three separators.

3. The length of the separator overlapping portion in the longitudinal direction is 3. The jelly-roll type electrode assembly according to claim 1, wherein the inner peripheral surface of the electrode assembly has a peripheral length of 100% or more and 300% or less.

4. The separator includes a coating layer provided on both sides, 3. The jelly roll type electrode assembly of claim 1, wherein the coating layer comprises an inorganic component, a binder component, and a lithium salt.

5. 3. The jelly roll type electrode assembly according to claim 1, wherein the positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector and having an end in a longitudinal direction at the same position as the positive electrode current collector.

6. A secondary battery comprising the electrode assembly according to claim 1 or 2; a positive electrode terminal having a rivet structure; and a sealing body, the electrode assembly is housed in a battery case, the negative electrode is electrically connected to the battery case, and the positive electrode is electrically connected to the positive electrode terminal; The sealing body seals the open portion of the battery case so as to be insulated from the battery case.

7. The rivet structure includes: Battery case open on one side; a positive electrode terminal riveted through a through hole formed in the bottom of the battery case; and A terminal gasket provided between the positive electrode terminal and the outer diameter of the through hole. The secondary battery according to claim 6 .

8. The positive terminal is a body portion inserted into the through hole; an external flange portion extending along the exterior surface from one peripheral edge of the body portion exposed through the exterior surface of the bottom portion; and an inner flange portion extending from the other peripheral edge of the body portion exposed through the inner surface of the bottom portion toward the inner surface; The secondary battery according to claim 7 .

9. The secondary battery according to claim 8 , wherein the positive terminal further comprises a flat portion provided at an end of the body portion exposed through the inner surface of the bottom portion.

10. The secondary battery according to claim 9 , wherein a recess is provided between the inner flange portion and the flat portion.

11. The secondary battery according to claim 10 , wherein the recess has an asymmetric groove cross-sectional structure.

12. the terminal gasket includes an outer gasket portion interposed between the outer flange portion and an outer surface of the base; and an inner gasket portion interposed between the inner flange portion and an inner surface of the base, The secondary battery of claim 8 , wherein the internal gasket portion extends longer than the internal flange portion.

13. the sealing body includes a non-polarized cap plate and a seal gasket interposed between an edge of the cap plate and an open end of the battery case; 7. The secondary battery according to claim 6, wherein the battery case includes: a beading portion pressed into the inside of the battery case in an area adjacent to an open end; and a crimping portion extending and bent into the inside of the battery case to surround and fix an edge of the cap plate together with the sealing gasket.

14. The secondary battery according to claim 13 , wherein the cap plate includes a vent portion that ruptures when an internal pressure of the battery case exceeds a threshold value.

15. Further comprising a negative electrode current collector, The negative electrode current collector plate has a center portion welded to an uncoated portion of the negative electrode; a tab coupling portion extending from the center portion and coupling with a negative electrode tab provided on the electrode assembly; and a battery case coupling portion extending from the central portion and positioned between adjacent tab coupling portions; The secondary battery according to claim 13 , wherein the battery case coupling portion is interposed between the beading portion and the seal gasket and is fixed by the crimping portion.

16. the battery case coupling portion of the negative electrode current collector plate is a contact portion fixed by welding to an inner circumferential surface of the beading portion adjacent to the crimping portion; and a connecting portion that has at least one bending portion where an extension direction is changed and connects the center portion and the contact portion; The secondary battery according to claim 15 .

17. the negative electrode current collector plate includes a negative electrode current collector hole formed at a position corresponding to a core hollow of the electrode assembly, The secondary battery according to claim 15 , wherein a difference between a diameter of the hole in the negative electrode current collector plate and a diameter of the hollow core of the electrode assembly is 0.1 mm or more and 1 mm or less.

18. Further comprising a positive electrode current collector, The positive electrode current collector is welded to the uncoated portion of the positive electrode, The secondary battery according to claim 13 , wherein at least a portion of the positive electrode current collector plate is welded to a flat portion of the positive electrode terminal.

19. The battery further includes an insulator interposed between the positive electrode current collector and an inner surface of a bottom of the battery case; and between an inner peripheral surface of the battery case and the electrode assembly, The secondary battery according to claim 18 , wherein the insulator includes a welding hole that exposes a flat portion of the positive terminal to the positive current collector plate side, and covers a surface of the positive current collector plate and one edge of the electrode assembly.

20. A battery pack comprising at least one secondary battery according to claim 6.

21. 21. A motor vehicle comprising at least one battery pack according to claim 20.

Images