Electrode assembly and secondary battery including the same

Abstract

An electrode assembly according to one embodiment of the present invention includes a first electrode, a second electrode, and a separator interposed between the first and second electrodes. The first electrode, the second electrode, and the separator are wound together to form a jelly roll structure. The first electrode includes a first electrode collector and a first active material portion formed by coating one or both surfaces of the first electrode collector with an electrode active material. The second electrode includes a second electrode collector and a second active material portion formed by coating one or both surfaces of the second electrode collector with an electrode active material. A first exposed portion of the first electrode collector, which is not coated with the electrode active material, extends in a first direction, and a second exposed portion of the second electrode collector, which is not coated with the electrode active material, extends in a second direction opposite to the first direction. The first exposed portion and the second exposed portion have bending points at each winding turn. The length from the end of the first electrode current collector in the second direction to the bending point of the first exposed portion gradually increases with each turn of winding along the radial direction of the jelly roll structure, which is the direction from the core portion to the outer portion of the jelly roll structure.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0157262 dated November 14, 2023, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly to a jelly-roll type electrode assembly and a secondary battery including the same. [Background technology]

[0003] Secondary batteries, which are highly adaptable to various products and have 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 powered by electrical sources.

[0004] 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 due to the use of energy, and are therefore attracting attention as a new energy source that is environmentally friendly and improves energy efficiency.

[0005] Currently widely used types of secondary batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. The operating voltage of such unit secondary batteries is approximately 2.5 V to 4.5 V. Therefore, if a higher output voltage is required, a battery module or battery pack may be constructed by connecting multiple secondary batteries, i.e., battery cells, in series. Alternatively, a large number of battery cells may be connected in parallel depending on the charge / discharge capacity required for the battery module or battery pack. Therefore, the number of battery cells included in the battery module or battery pack and the electrical connection configuration can be variously set depending on the required output voltage and charge / discharge capacity.

[0006] The electrode assembly built into the battery cell is a chargeable and dischargeable power generating element consisting of a laminated structure of a positive electrode, a separator, and a negative electrode, and is classified into jelly roll, stack, and stack / folded types. The jelly roll type is a long sheet-like positive electrode and negative electrode coated with active material, with a separator interposed between them, which are then wound up. The stack type is a type in which multiple positive electrodes and negative electrodes of a specified size are stacked in order with a separator interposed between them, and the stack / folded type is a combination of the jelly roll and stack types. Among these, the jelly roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per weight.

[0007] Secondary batteries, or battery cells, are classified according to the shape of the battery case into cylindrical batteries, in which an electrode assembly is housed in a cylindrical battery can, prismatic batteries, in which an electrode assembly is housed in a prismatic battery can, and pouch batteries, in which an electrode assembly is housed in a pouch-shaped case made of aluminum laminate sheet. Of these, cylindrical batteries have the advantages of relatively large capacity and structural stability.

[0008] In cylindrical batteries, a separator, an insulator, is interposed between a positive electrode and a negative electrode, which is then wound up to form a jelly-roll-shaped electrode assembly, which is then inserted into a battery can to construct a battery. Strip-shaped electrode tabs are connected to the uncoated portions of the positive and negative electrodes, respectively, and the electrode tabs electrically connect the electrode assembly to the exposed electrode terminals. The positive electrode terminal is a sealed cap assembly that seals the open top of the battery can, and the negative electrode terminal is the battery can itself. However, conventional cylindrical batteries with this structure have problems such as high resistance, excessive heat generation, and poor current collection efficiency due to current concentration at the strip-shaped electrode tabs connected to the positive and negative uncoated portions.

[0009] Small cylindrical batteries with form factors such as 1865 (diameter: 18mm, height: 65mm) and 2170 (diameter: 21mm, height: 70mm) do not pose significant resistance and heat generation issues. However, when the form factor is increased to apply cylindrical batteries to electric vehicles, there is a possibility that the cylindrical battery may catch fire due to the excessive heat generated around the electrode tabs during fast charging.

[0010] To solve these problems, a secondary battery with a structure that improves current collection efficiency by designing the upper and lower ends of the jelly-roll type electrode assembly to have exposed portions where the positive and negative electrode current collectors are exposed, and welding current collector plates to these exposed portions, known as a tab-less secondary battery, has been proposed.

[0011] However, in the jelly-roll-shaped electrode assemblies included in such tableless secondary batteries, the exposed portions are sometimes bent toward the core of the jelly-roll electrode assembly to bond them to the current collector plate. That is, the exposed portions are bent toward the core of the jelly-roll electrode assembly, and these exposed portions are stacked with each winding turn and bonded to the current collector plate. However, due to the characteristics of jelly-roll-shaped electrode assemblies, the thickness of the stacked exposed portions increases toward the core of the jelly-roll electrode assembly. This causes the stacked exposed portions to undergo irregular deformation and collapse, which can directly lead to the risk of fire from secondary batteries including such electrode assemblies. Specifically, if the separator is damaged due to irregular deformation of the stacked exposed portions, a short circuit occurs between the positive and negative electrodes, which can lead to fire or explosion of the secondary battery.

[0012] Therefore, there is a need for an improved method for preventing irregular deformation of the stacked exposed portions in tab-less secondary batteries. Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention provides an electrode assembly and a secondary battery including the same, which can prevent irregular deformation of a bendable exposed portion of a jelly-roll-shaped electrode assembly in which the exposed portion of an electrode current collector functions as a terminal when the electrode current collector is stacked.

[0014] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0015] An electrode assembly according to one embodiment of the present invention includes a first electrode, a second electrode, and a separator interposed between the first and second electrodes. The first electrode, the second electrode, and the separator are wound together to form a jelly roll structure. The first electrode includes a first electrode collector and a first active material portion formed by coating one or both surfaces of the first electrode collector with an electrode active material. The second electrode includes a second electrode collector and a second active material portion formed by coating one or both surfaces of the second electrode collector with an electrode active material. A first exposed portion of the first electrode collector, which is not coated with the electrode active material, extends in a first direction, and a second exposed portion of the second electrode collector, which is not coated with the electrode active material, extends in a second direction opposite to the first direction. The first exposed portion and the second exposed portion have bending points at each winding turn. The length from the end of the first electrode current collector in the second direction to the bending point of the first exposed portion gradually increases with each turn of winding along the radial direction of the jelly roll structure, which is the direction from the core portion to the outer portion of the jelly roll structure.

[0016] The first exposed portion may include a plurality of first segments that are bent independently of each other, and the bending points of the first exposed portion may be points at which the first segments are bent.

[0017] In a K-th winding turn (where K>2) of the jelly roll structure along the radial direction of the jelly roll structure, the length from the end of the first electrode current collector in the second direction to the bending point of the first exposed portion is defined as L1. K When we define L1 K -L1 K-1 is t1*(N1 K *A1 K ) / 2πR1 K-1 ) can satisfy 50% or more and 300% or less of the above. The t1 is the thickness of the first slice, and the N1 K is the number of the first segments along the circumferential direction in the K-th winding turn, and A1 Kis the width of the first segment of the K-th winding turn placed on the K-1-th winding turn, and R1 K-1 is the radius at the K-1th winding turn.

[0018] The first section may be in the form of a square.

[0019] A1 K is the width of the connecting end of the first segment, W1 K It can be calculated as follows.

[0020] The first section may be trapezoidal in shape.

[0021] A1 K is W1 K -2*(D1 K / tanθ1) can be calculated. K is the width of the connecting end of the first segment, and D1 K is the distance between the K-th winding turn and the (K-1)-th winding turn, and θ1 is the interior angle of the connecting end of the first trapezoidal segment.

[0022] With each winding turn of the jelly roll structure along the radial direction, the length from the end of the second electrode current collector in the first direction to the bending point of the second exposed portion may gradually increase.

[0023] The second exposed portion may include a plurality of second segments that are bent independently of each other, and the bending points of the second exposed portion may be points at which the second segments are bent.

[0024] In the K-th winding turn of the jelly roll structure (where K>2) along the radial direction of the jelly roll structure, the length from the end of the second electrode current collector in the first direction to the bending point of the second exposed portion is defined as L2 K When we define L2 K -L2 K-1is t2*(N2 K *A2 K ) / 2πR2 K-1 ) can satisfy 50% or more and 300% or less of the above. t2 is the thickness of the second slice, and N2 K is the number of the second segments along the circumferential direction in the K-th winding turn, and A2 K is the width of the second segment of the K-th winding turn placed on the K-1-th winding turn, and R2 K-1 is the radius at the K-1th winding turn.

[0025] The second section may be in the form of a rectangle.

[0026] Said A2 K is the width of the connecting end of the second segment, W2 K It can be calculated as follows.

[0027] The second section may be trapezoidal in shape.

[0028] Said A2 K is W2 K -2*(D2 K / tanθ2) can be calculated. K is the width of the connecting end of the second segment, and D2 K is the distance between the K-th winding turn and the (K-1)-th winding turn, and θ2 is the interior angle of the connecting end of the second segment, which is trapezoidal.

[0029] A secondary battery according to an embodiment of the present invention includes the electrode assembly. [Effects of the Invention]

[0030] According to an embodiment of the present invention, in a jelly-roll type electrode assembly in which the exposed portions of the electrode current collectors function as terminals, the positions of the bending points for each winding turn of the exposed portions are set to vary in the radial direction, thereby preventing irregular deformation of the stacked exposed portions, thereby preventing short circuits between the positive and negative electrodes and the resulting fires and explosions.

[0031] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a view showing an electrode assembly according to an embodiment of the present invention before being wound up; [Figure 2] 1 is a view showing a state in which an electrode assembly according to an embodiment of the present invention is wound up; [Figure 3] 1 is a view illustrating a state in which the electrode assembly according to an embodiment of the present invention has been completely wound up; [Figure 4] FIG. 4 is a top plan view of the electrode assembly of FIG. 3. [Figure 5] FIG. 5 is a cross-sectional view showing a cross section taken along the line AA' in FIG. 4. [Figure 6] FIG. 10 is a cross-sectional view showing a cross section of an electrode assembly according to a comparative example of the present invention. [Figure 7] 1 is a diagram illustrating a state in which a first partial section of a specific winding turn is placed on the previous winding turn in an electrode assembly according to an embodiment of the present invention. [Figure 8] 2 is a partial view showing a part of a first electrode according to an embodiment of the present invention. [Figure 9] 1 is a diagram schematically illustrating only the first electrode in the Kth winding turn. [Figure 10]10 is a diagram illustrating a state in which a split piece at a specific winding turn is placed on the previous winding turn in an electrode assembly according to a modified embodiment of the present invention. [Figure 11] 10 is a partial view showing a part of a first electrode according to a modified embodiment of the present invention; [Figure 12] 10 is a diagram illustrating a state in which a second portion of a specific winding turn is placed on the previous winding turn in an electrode assembly according to an embodiment of the present invention. [Figure 13] 4 is a partial view showing a part of a second electrode according to an embodiment of the present invention. [Figure 14] 10 is a diagram illustrating a state in which a split piece at a specific winding turn is placed on the previous winding turn in an electrode assembly according to a modified embodiment of the present invention. [Figure 15] 10 is a partial view showing a part of a second electrode according to a modified embodiment of the present invention; [Figure 16] 1 is a cross-sectional view of a secondary battery including an electrode assembly according to an embodiment of the present invention. [Figure 17] 10 is a view illustrating a method of bending a first segment of a first electrode according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0034] To clearly describe the present invention, portions unnecessary for the description will be omitted and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0035] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to the size and thickness shown. Thicknesses are exaggerated to clearly show various layers and regions in the drawings. In addition, the thicknesses of some layers and regions are exaggerated in the drawings for the convenience of explanation.

[0036] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly above" that other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" in the opposite direction of gravity.

[0037] Furthermore, throughout the specification, when a part is said to "comprise" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0038] Furthermore, throughout the specification, the term "on a plane" means when the subject part is viewed from above, and the term "on a cross section" means when the subject part is cut vertically and viewed from the side.

[0039] Fig. 1 is a view showing an electrode assembly according to an embodiment of the present invention before being wound up. Fig. 2 is a view showing an electrode assembly according to an embodiment of the present invention being wound up. Fig. 3 is a view showing an electrode assembly according to an embodiment of the present invention after being completely wound up. Fig. 4 is a plan view of the electrode assembly of Fig. 3 as seen from above. Fig. 5 is a cross-sectional view taken along line A-A' of Fig. 4.

[0040] 1 to 5, an electrode assembly 10 according to an embodiment of the present invention includes a first electrode 100, a second electrode 200, and a separator 300 interposed between the first electrode 100 and the second electrode 200. The first electrode 100, the second electrode 200, and the separator 300 are wound together to form a jelly roll structure. That is, the electrode assembly 10 according to this embodiment is a jelly roll-shaped electrode assembly. Furthermore, to prevent the first electrode 100 and the second electrode 200 from contacting each other when wound into a jelly roll shape, a separator 300 may be additionally disposed on the outer side of the first electrode 100 or the second electrode 200, as shown in FIG. 1. That is, the electrode assembly 10 may include two or more separators 300. For example, as shown in FIG. 1, the electrode assembly 10 according to this embodiment is manufactured by stacking the second electrode 200, one separator 300, the first electrode 100, and another separator 300 and winding them in the winding direction (dw).

[0041] The first electrode 100 includes a first electrode current collector 110 and a first active material portion 120 formed by applying an electrode active material to one or both surfaces of the first electrode current collector 110. In addition, a first exposed portion 110E of the first electrode current collector 110, where the electrode active material is not applied, extends in a first direction (d1). Specifically, the portion of the first electrode current collector 110 where the electrode active material is not applied and where the first electrode current collector 110 is exposed may correspond to the first exposed portion 110E.

[0042] The second electrode 200 includes a second electrode current collector 210 and a second active material portion 220 formed by applying an electrode active material to one or both surfaces of the second electrode current collector 210. In addition, a second exposed portion 210E of the second electrode current collector 210, where the electrode active material is not applied, extends in a second direction (d2) opposite to the first direction (d1). Specifically, the portion of the second electrode current collector 210 where the electrode active material is not applied and where the second electrode current collector 210 is exposed may correspond to the second exposed portion 210E.

[0043] The first direction (d1) and the second direction (d2) are opposite directions in the axial direction of the electrode assembly 10, and the axial direction of the electrode assembly 10 corresponds to the direction along the central axis of the wound cylindrical electrode assembly 10. In FIG. 2, the axial direction of the electrode assembly 10 corresponds to the direction parallel to the z-axis.

[0044] For example, one of the first electrode 100 and the second electrode 200 is a positive electrode, and the other is a negative electrode. That is, one of the first electrode current collector 110 and the second electrode current collector 210 is a positive electrode current collector, and the other is a negative electrode current collector. Also, one of the first active material portion 120 and the second active material portion 220 is a positive electrode active material portion coated with a positive electrode active material, and the other is a negative electrode active material portion coated with a negative electrode active material.

[0045] In the present invention, the positive electrode current collector and the negative electrode current collector may be made of any metal material known in the art, and the positive electrode active material coated on the positive electrode and the negative electrode active material coated on the negative electrode may be made of any active material known in the art.

[0046] The positive electrode current collector may be a thin metal foil, typically having a thickness of 3 to 500 micrometers. There are no particular limitations on the positive electrode current collector, as long as it has high conductivity and does not induce chemical changes in the battery. Examples include stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may have fine irregularities on its surface to enhance the adhesive strength of the positive electrode active material, and may be in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0047] The positive electrode active material is represented by the general formula A[A x M y ]O 2+z(A contains at least one element of Li, Na, and K; M contains at least one element selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Al, Mo, Sc, Zr, Ru, and Cr; x≧0, 1≦x + y≦2, -0.1≦z≦2; the stoichiometric coefficients x, y, and z are selected so that the compound maintains electrical neutrality) and can contain an alkali metal compound represented by.

[0048] In another example, the positive electrode active material is an alkali metal compound xLiM disclosed in US6,677,082, US6,680,143, etc. 1 O2-(1 - x)Li2M 2 O3(M 1 contains at least one or more elements having an average oxidation state of 3; M 2 contains at least one element having an average oxidation state of 4; 0≦x≦1) may be.

[0049] In yet another example, the positive electrode active material is of the general formula Li a M 1 x Fe 1-x M 2 y P 1-y M 3 z O 4-z (M 1 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, and Al; M 2 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, Al, As, Sb, Si, Ge, V, and S; M 3 contains a halogen group element selectively containing F; 0 < a≦2, 0≦x≦l, 0≦y < 1, 0≦z < 1; the stoichiometric coefficients a, x, y, and z are selected so that the compound maintains electrical neutrality), or lithium metal phosphate represented by Li3M2(PO4)3 [M contains at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg, and Al] may be.

[0050] The negative electrode current collector may be a thin metal foil, typically having a thickness of 3 to 500 micrometers. There are no particular limitations on the negative electrode current collector, as long as it is conductive and does not induce chemical changes in the battery. Examples of such a negative electrode current collector include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Similarly to the positive electrode current collector, the surface may be formed with fine irregularities to strengthen the binding strength of the negative electrode active material. The negative electrode current collector is available in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0051] The negative electrode active material may be a carbon material, lithium metal or a lithium metal compound, silicon or a silicon compound, or tin or a tin compound. Metal oxides such as TiO2 and SnO2, which have a potential of less than 2 V, may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon.

[0052] The separator is a thin insulating membrane interposed between the positive and negative electrodes, with high ion permeability and mechanical strength. The pore diameter of the separator is generally 0.01 to 10 micrometers, and the thickness is generally 5 to 300 micrometers. Examples of such separators include sheets or nonwoven fabrics made of chemically resistant and hydrophobic olefin polymers such as polypropylene, glass fiber, or polyethylene. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte can also serve as the separator.

[0053] Meanwhile, in the electrode assembly 10 according to this embodiment, the first exposed portion 110E and the second exposed portion 210E have bending points (BP) for each winding turn. As will be described later, the electrode assembly 10 according to this embodiment has a tab-less structure in which the first exposed portion 110E and the second exposed portion 210E are directly connected to the current collector plate, rather than having electrode tabs attached to the electrode collector, thereby guiding electrical connection. In this case, to bond the first exposed portion 110E and the second exposed portion 210E to the current collector plate, the first exposed portion 110E and the second exposed portion 210E can be bent toward the core part 10C of the electrode assembly 10 in the jelly roll structure. Here, the points at which the first exposed portion 110E and the second exposed portion 210E are bent are referred to as bending points (BP). The core 10C of the electrode assembly 10 is the starting point of winding and the center of the cylindrical electrode assembly 10 when viewed from above, and refers to the empty space formed in the center of the electrode assembly 10 in a jelly roll structure. Here, viewing the electrode assembly 10 in a jelly roll structure from above means viewing the electrode assembly 10 in an axial direction, i.e., along the z-axis direction or the -z-axis direction, on the xy plane, as shown in FIG.

[0054] In this embodiment, for each winding turn along the radial direction (dr) of the jelly roll structure, the length (L1 K-1 , L1 K) gradually increases. Here, the radial direction (dr) of the jelly roll structure refers to the direction from the core portion 10C to the outer portion 10U of the jelly roll structure. The outer portion 10U of the jelly roll structure refers to the outer periphery of the jelly roll structure when the electrode assembly 10, which is a jelly roll structure, is viewed from above. Therefore, the radial direction (dr) refers to the direction away from the core portion 10C when the electrode assembly 10, which is a jelly roll structure, is viewed from above. In addition, a "winding turn" refers to each portion of the wound first electrode 100 that contacts a certain radial direction (dr). In other words, a "bending point (BP) per winding turn" refers to each point where the first exposed portion 110E is bent to each portion of the wound first electrode 100 that contacts a certain radial direction (dr).

[0055] That is, in this embodiment, the height of the bending point (BP) of the first exposed portion 110E in the first direction (d1) for each winding turn may gradually increase as one moves toward the radial direction (dr). As described above, since the first exposed portion 110E has the bending point (BP) bending toward the core part 10C, the thickness of the portion where the first exposed portion 110E is stacked, i.e., the stacking thickness, increases toward the core part 10C. Here, the direction toward the core part 10C corresponds to the opposite direction of the radial direction (dr).

[0056] As the number of winding turns increases, the number of first exposed portions 110E stacked in the radial direction (dr) also increases, and the first exposed portions 110E that are overstacked in a limited space become irregularly deformed. This irregular deformation of the first exposed portions 110E can damage the separator 300, which can cause a short circuit between the first electrode 100 and the second electrode 200. This problem will be described again with reference to a comparative example of the present invention shown in FIG.

[0057] FIG. 6 is a cross-sectional view showing a cross section of an electrode assembly according to a comparative example of the present invention.

[0058] 6, an electrode assembly according to a comparative example of the present invention may include a first electrode 100′, a second electrode 200′, and a separator 300′. The first electrode 100′ may include a first electrode current collector 110′ and a first active material portion 120′, and the second electrode 200′ may include a second electrode current collector 210′ ​​and a second active material portion 220′. A first exposed portion 110E′ of the first electrode current collector 110′, on which no electrode active material is applied, may extend in a first direction (d1), and a second exposed portion 210E′ of the second electrode current collector 210′, on which no electrode active material is applied, may extend in a second direction (d2) opposite to the first direction (d1). The first exposed portion 110E′ may include a first partial segment 110F′, which will be described later, and the first partial segment 110F′ may have a bending point (BP). The second exposed portion 210E' also includes a second segment 210F', which will be described later, and the second segment 210F' has a bending point (BP).

[0059] Unlike the electrode assembly of this embodiment described above, the electrode assembly of this comparative example has a constant length (L1') from the end of the first electrode current collector 110' in the second direction (d2) to the bending point (BP) of the first exposed portion 110E' for each winding turn along the radial direction (dr) of the jelly roll structure. That is, the height of the bending point (BP) of the first partial segment 110F' of the first exposed portion 110E' is constant for each winding turn. When multiple first exposed portions 110E' are bent and stacked for each winding turn, if the height of the bending point (BP) of the first partial segment 110F' is constant as in this comparative example, some of the first exposed portions 110E' may exhibit irregular deformation and be crushed. In particular, the portion of the first partial segment 110F' near the core may bend further in the direction indicated by "I" because it cannot maintain its axial and perpendicular orientation. Such an unexpectedly bent first segment 110F' may damage the separator 300', and the damaged separator 300' may cause a short circuit between the first electrode 100' and the second electrode 200'. Such a short circuit may ultimately lead to fire or explosion of the secondary battery.

[0060] Referring again to FIG. 5, in the case of the electrode assembly 10 according to this embodiment, in order to prevent such a short circuit problem, as described above, the length (L1) from the end of the first electrode current collector 110 in the second direction (d2) to the bending point (BP) of the first exposed portion 110E is increased for each winding turn along the radial direction (dr) of the jelly roll structure. K-1 , L1 K ) gradually increases. That is, the height of the bending point (BP) of each winding turn of the first exposed portion 110E in the first direction (d1) is designed to increase sequentially toward the radial direction (dr). In this embodiment, the heights of the first exposed portions 110E for each winding turn are different, and the first exposed portions 110E for each winding turn are stacked sequentially, preventing some of the first exposed portions 110E from being crushed due to irregular deformation. This minimizes the occurrence of short circuits between the first electrode 100 and the second electrode 200 due to damage to the separator 300.

[0061] Meanwhile, according to this embodiment, the first exposed portion 110E may include a plurality of first sub-segments 110F that can be bent independently of each other, and the bending points (BP) of the first exposed portion 110E described above may be points where the first sub-segments 110F are bent. Specifically, the first exposed portion 110E is not integral, but has cut grooves of a predetermined depth at regular intervals. That is, the first exposed portion 110E may be divided by the first sub-segments 110F, which are the regions between the cut grooves. If the first exposed portion 110E were integrally formed, when the first exposed portion 110E was bent in the direction of the core portion 10C, the bending space would be narrow, and the first exposed portion 110E may wrinkle irregularly. To prevent this problem, it is preferable to divide the first exposed portion 110E into a plurality of first sub-segments 110F and then bend the first sub-segments 110F.

[0062] 3 and 4 show that a plurality of first sub-segments 110F are bent and stacked in multiple layers to form a flat surface area in the first direction (d1) of the electrode assembly 10. A current collector plate (described later) contacts this surface area of ​​the electrode assembly 10 to guide electrical connections of the electrode assembly 10. That is, the first exposed portion 110E including the first sub-segments 110F guides electrical connections instead of electrode tabs, thereby achieving a tab-less structure. Compared to conventional methods using electrode tabs, the flat surface area formed by the first sub-segments 110F allows for a larger area for electrical connections, thereby increasing the energy density of the electrode assembly and reducing resistance.

[0063] The range of height difference at the bending point (BP) for each winding turn will be explained below.

[0064] 7 is a schematic diagram illustrating a state in which a first partial section of a specific winding turn is placed on the previous winding turn in an electrode assembly according to an embodiment of the present invention, and FIG. 8 is a partial diagram illustrating a portion of a first electrode according to an embodiment of the present invention.

[0065] 7 and 8 together with FIGS. 3 to 5, in the K-th winding turn (where K>2) of the jelly roll structure along the radial direction (dr) of the jelly roll structure, the length from the end of the first electrode current collector 110 in the second direction (d2) to the bending point (BP) of the first exposed portion 110E is defined as L1. K At this time, L1 K -L1 K-1 is t1*(N1 K *A1 K ) / (2πR1 K-1 ) can satisfy the condition of 50% or more and 300% or less. Here, t1 is the thickness of the first section 110F. N1 K is the number of first segments 110F along the circumferential direction (dc) in the K-th winding turn. Kis the width of the first segment 110F of the K-th winding turn placed on the K-1-th winding turn. K-1 is the radius at the (K-1)th winding turn. K is the number of winding turns of the first electrode 100, and is therefore an integer greater than 2.

[0066] Here, the circumferential direction (dc) corresponds to a direction surrounding the core portion 10C, i.e., a circumferential direction, when the electrode assembly 10 is viewed from above. In other words, the circumferential direction (dc) may refer to a direction extending along the outer portion 10U, which is the side surface of the cylindrical electrode assembly 10, when the electrode assembly 10 is viewed from above.

[0067] Also, the number of first segments 110F along the circumferential direction (dc) in the K-th winding turn (N1 K ) means the number of first partial segments 110F present in the portion where the first electrode 100 is wound once for the Kth time.

[0068] On the other hand, the radius of the Kth winding turn (R1 K ) will be explained with reference to FIG.

[0069] FIG. 9 is a diagram that schematically illustrates only the first electrode in the Kth winding turn.

[0070] In FIG. 7, the first electrode 100K at the K-th winding turn and the first electrode 100K-1 at the K-1th winding turn are depicted as being in the shape of a perfect circle, but as shown in FIG. 9, the first electrode 100K at the K-th winding turn may not be in the shape of a perfect circle. In this case, in the present invention, the radius (R1 K ) is the shortest radial distance (R1 K.min ) and the longest distance (R1 K.max) can be defined as the intermediate value of the radius (R1 K ) may be defined as above.

[0071] In this embodiment, L1 K -L1 K-1 corresponds to the height difference between the bending point (BP) of the K-1th winding turn and the Kth winding turn. K *A1 K ) / (2πR1 K-1 The value of D1 is a value for calculating the degree to which the first electrode 110F in the K-th winding turn overlaps the first electrode 100 in the K-1th winding turn, i.e., the overlap ratio of the first electrode 110F in the K-th winding turn to the K-1th winding turn. In order to calculate this overlap ratio, the first electrode 100K in the K-th winding turn and the first electrode 100K-1 in the K-1th winding turn are simply generalized and expressed as concentric circles in FIG. 7. Meanwhile, D1 K is the distance between the first electrode 100K of the K-th winding turn and the first electrode 100K-1 of the K-1-th winding turn, and the radius (R1 K ) and the radius at the K-1th winding turn (R1 K-1 ) can be calculated as the difference.

[0072] For ease of explanation, only three first segments 110F are shown among the multiple first segments 110F present on the first electrode 100K of the Kth winding turn. The multiple first segments 110F present on the first electrode 100K of the Kth winding turn are bent toward the core portion 10C, and the first segments 110F of the first electrode 100K of the Kth winding turn overlap on the first electrode 100K-1 of the K-1th winding turn. In the present invention, the overlap ratio of the first segment 110F of the Kth winding turn to the K-1th winding turn is defined as (N1 K *A1 K) / (2πR1 K-1 Specifically, assuming that the first electrode 100K of the K-th winding turn and the first electrode 100K-1 of the K-1th winding turn are concentric circles, the width (A1 K ) and the number of first-minute segments 110F in the K-th winding turn (N1 K ) and divide the result by the circumference of the (K-1)th winding turn to obtain the overlap ratio.

[0073] By multiplying this overlap ratio by the thickness (t1) of the first section 110F, the lamination thickness of the first section 110F of the Kth winding turn relative to the K-1th winding turn can be calculated. In this embodiment, the height difference between the bending points (BP) of the first sections 110F for each winding turn is in the range of 50% to 300% of the lamination thickness calculated in this manner.

[0074] Suppose, L1 K -L1 K-1 The value of t1*(N1 K *A1 K ) / (2πR1 K-1 If the difference in height between the bending points (BP) of the first section 110F per winding turn is less than 50%, the difference in height between the bending points (BP) of the first section 110F per winding turn is insufficient, and it is not possible to prevent irregular deformation of some of the first section 110F when the first section 110F is bent.

[0075] Also, if L1 K -L1 K-1 The value of t1*(N1 K *A1 K ) / 2πR1 K-1 If the height exceeds 300%, the height difference between the bending points (BP) of the first section 110F per winding turn becomes too large, resulting in a large amount of unnecessary space along the height direction of the jelly roll electrode assembly 10. This is undesirable as it reduces the capacity and energy density of the secondary battery.

[0076] 8, a first exposed portion 110E is formed by exposing a portion of the first electrode current collector 110 of the first electrode 100, and the first exposed portion 110E may include rectangular first partial segments 110F spaced apart at regular intervals.

[0077] When the first segment 110F has a rectangular shape, the A1 K is the width of the connecting end of the first segment 110F, W1 K Here, the connecting end of the first segment 110F is the portion of the first segment 110F that extends from the first exposed portion 110E. In FIG. 8, the connecting end corresponds to the bottom side when the first segment 110F is viewed as a virtual rectangle. Since the width of the first segment 110F, which is a rectangle, is constant, the width (A1 K ) is the width (W1 K ) That is, when the first segment 110F has a rectangular shape, A1 K The value is W1 K The value may be used as is.

[0078] Figure 10 is a schematic view showing a state in which a segment of a specific winding turn is placed on the previous winding turn in an electrode assembly according to a modified embodiment of the present invention, and Figure 11 is a partial view showing a portion of a first electrode according to a modified embodiment of the present invention.

[0079] 10 and 11 together with FIGS. 3 to 5, as described above, in the K-th winding turn (where K>2) of the jelly roll structure along the radial direction (dr) of the jelly roll structure, the length from the end of the first electrode current collector 110 in the second direction (d2) to the bending point (BP) of the first exposed portion 110E is defined as L1. K It can be defined as follows. Also, L1 K -L1 K-1 is t1*(N1 K*A1 K ) / (2πR1 K-1 ) can satisfy the condition of 50% or more and 300% or less. Here, t1 is the thickness of the first section 110F. N1 K is the number of first segments 110F along the circumferential direction (dc) in the K-th winding turn. K is the width of the first segment 110F of the K-th winding turn placed on the K-1-th winding turn. K-1 is the radius of the (K-1)th winding turn. K is the number of winding turns of the first electrode 100, and is therefore an integer greater than 2. A detailed description of this will be omitted as it overlaps with the above description.

[0080] According to a modified embodiment of the present invention, the first partial segments 110F may have a trapezoidal shape. In particular, the first partial segments 110F may have an equilateral trapezoidal shape. As shown in FIG. 11 , a portion of the first electrode current collector 110 of the first electrode 100 is exposed to form a first exposed portion 110E, and the first exposed portion 110E may include trapezoidal first partial segments 110F spaced apart at regular intervals.

[0081] When the first segment 110F has an equilateral trapezoidal shape, the A1 K is W1 K -2*(D1 K / tanθ1) can be calculated. K is the width of the connecting end of the first segment 110F. The connecting end of the first segment 110F is the portion where the first segment 110F extends from the first exposed portion 110E. K is the interval between the K-th winding turn and the K-1-th winding turn. Specifically, D1 K is the distance between the first electrode 100K of the Kth winding turn and the first electrode 100K-1 of the K-1th winding turn, and the radius (R1K) of the K-1th winding turn and the radius (R1 K-1) and the angle θ1 is the interior angle of the connecting end of the trapezoidal first segment 110F.

[0082] The connecting end of the first segment 110F is the portion of the first segment 110F extending from the first exposed portion 110E, and refers to the relatively long side when the first segment 110F is viewed as a virtual trapezoid. Also, the connecting end interior angle (θ1) refers to the interior angle between the long side and both sides when the first segment 110F is viewed as a virtual trapezoid. The connecting end interior angle (θ1) is an acute angle in the trapezoid structure. When the first segment 110F is trapezoidal, A1 K The value is W1 K The value should not be used as is, A1 K is W1 K -2*(D1 K It is preferable to calculate it as follows:

[0083] Hereinafter, the structure of the second exposed portion 210E of the second electrode 200 according to an embodiment of the present invention will be described in detail.

[0084] Referring again to FIG. 5, as described above, the second exposed portion 210E of the second electrode 200 may also have a bending point (BP). In the case of the electrode assembly 10 according to this embodiment, the length (L2) from the end of the second electrode current collector 210 in the first direction (d1) to the bending point (BP) of the second exposed portion 210E is increased for each winding turn along the radial direction (dr) of the jelly roll structure. K-1 , L2 K ) can be gradually increased.

[0085] Since the second exposed portion 210E is bent toward the core portion 10C and has a bending point (BP), the thickness of the portion where the second exposed portion 210E is laminated, i.e., the laminate thickness, increases toward the core portion 10C. Here, the direction toward the core portion 10C corresponds to the opposite direction to the radial direction (dr).

[0086] As the number of winding turns increases, the number of second exposed portions 210E stacked in the radial direction (dr) also increases, and the second exposed portions 210E stacked excessively in a limited space may deform irregularly. Such irregular deformation of the second exposed portions 210E may damage the separator 300, which may cause a short circuit between the first electrode 100 and the second electrode 200.

[0087] Referring again to FIG. 6, in the electrode assembly according to this comparative example, the length (L2') from the end of the second electrode current collector 210' in the first direction (d1) to the bending point (BP) of the second exposed portion 210E' is constant for each winding turn along the radial direction (dr) of the jelly roll structure. That is, the height of the bending point (BP) of the second segment 210F' of the second exposed portion 210E' is constant for each winding turn. When multiple second exposed portions 210E' are bent and stacked for each winding turn, if the height of the bending point (BP) of the second segment 210F' is constant as in this comparative example, some of the second exposed portions 210E' may exhibit irregular deformation and be crushed. In particular, the portion of the second segment 210F' near the core may be unable to maintain a perpendicular orientation to the axial direction and may be further bent in the direction indicated by "I." The second segment 210F' bent in such an unexpected direction may damage the separator 300', and the damaged separator 300' may cause a short circuit between the first electrode 100' and the second electrode 200'. Such a short circuit may ultimately lead to fire or explosion of the secondary battery.

[0088] Referring again to FIG. 5, in the case of the electrode assembly 10 according to this embodiment, in order to prevent such a short circuit problem, as described above, the length (L2 K-1 , L2 K) may gradually increase. That is, the height of the bending point (BP) of each second exposed portion 210E in the second direction (d2) for each winding turn is designed to gradually decrease as it moves in the radial direction (dr). In this embodiment, there is a height difference between each winding turn, and the second exposed portions 210E for each winding turn are stacked sequentially, which prevents some of the second exposed portions 210E from exhibiting irregular deformation and being crushed. This minimizes the occurrence of short circuits between the first electrode 100 and the second electrode 200 due to damage to the separator 300.

[0089] Meanwhile, according to this embodiment, the second exposed portion 210E may include a plurality of second divided segments 210F that can be bent independently of each other, and the bending points (BP) of the second exposed portion 210E described above may be the points at which the second divided segments 210F are bent. Specifically, the second exposed portion 210E is not integral, but has cut grooves of a predetermined depth at regular intervals. That is, the second exposed portion 210E may be divided into the second divided segments 210F, which are the areas between the cut grooves. If the second exposed portion 210E were integrally formed, the second exposed portion 210E may wrinkle irregularly when it is bent in the direction of the core portion 10C due to the narrow bending space. To prevent this problem, it is preferable to divide the second exposed portion 210E into a plurality of second divided segments 210F and then bend the second divided segments 210F.

[0090] Although not specifically shown, multiple second segments 210F may be bent and stacked in multiple layers to form a flat surface area in the second direction (d2) of the electrode assembly 10. A current collector plate (described later) may contact this surface area of ​​the electrode assembly 10 to guide electrical connection of the electrode assembly 10. That is, the second exposed portion 210E including the second segments 210F guides electrical connection instead of electrode tabs, thereby achieving a tab-less structure. Compared to conventional methods using electrode tabs, the flat surface area formed by the second segments 210F allows for a larger area for electrical connection, thereby increasing the energy density of the electrode assembly and reducing resistance.

[0091] The range of height difference at the bending point (BP) for each winding turn will be explained below.

[0092] Figure 12 is a schematic diagram illustrating a state in which a second segment of a specific winding turn is placed on the previous winding turn in an electrode assembly according to an embodiment of the present invention, and Figure 13 is a partial view showing a portion of a second electrode according to an embodiment of the present invention.

[0093] 12 and 13 together with FIGS. 3 to 5, in the K-th winding turn (where K>2) of the jelly roll structure along the radial direction (dr) of the jelly roll structure, the length from the end of the second electrode current collector 210 in the first direction (d1) to the bending point (BP) of the second exposed portion 210E is defined as L2 K At this time, L2 K -L2 K-1 is t2*(N2 K *A2 K ) / (2πR2 K-1 ) can satisfy the condition of 50% or more and 300% or less. Here, t2 is the thickness of the second cut piece 210F. K is the number of second segments 210F along the circumferential direction (dc) in the K-th winding turn. Kis the width of the second segment 210F of the K-th winding turn placed on the K-1-th winding turn. K-1 is the radius at the (K-1)th winding turn. K is the number of winding turns of the second electrode 200, and is therefore an integer greater than 2.

[0094] Here, the circumferential direction (dc) corresponds to a direction surrounding the core portion 10C, i.e., a circumferential direction, when the electrode assembly 10 is viewed from above. In other words, the circumferential direction (dc) may refer to a direction extending along the outer portion 10U, which is the side surface of the cylindrical electrode assembly 10, when the electrode assembly 10 is viewed from above.

[0095] Also, the number of second segments 210F along the circumferential direction (dc) in the K-th winding turn (N2 K ) means the number of second partial segments 210F present in the portion where the second electrode 200 is wound once for the Kth time.

[0096] On the other hand, the radius (R2 K ) is the radius (R1 K ) can be defined in the same way. Although not specifically shown, the radius (R2 K ) can be defined as the median value between the shortest and longest radial distances from the core portion 10C to the Kth wound portion of the second electrode 200.

[0097] In this embodiment, L2 K -L2 K-1 corresponds to the height difference between the bending point (BP) of the K-1th winding turn and the Kth winding turn. At this time, (N2 K *A2 K ) / (2πR2 K-1The value of D2 is a value for calculating the degree to which the second electrode 200K of the K-th winding turn overlaps the second electrode 200 of the K-1th winding turn, i.e., the overlap ratio of the second electrode 210F of the K-th winding turn to the K-1th winding turn. In order to calculate this overlap ratio, the second electrode 200K of the K-th winding turn and the second electrode 200K-1 of the K-1th winding turn are simply expressed as concentric circles in FIG. 12. K is the distance between the second electrode 200K of the K-th winding turn and the second electrode 200K-1 of the K-1-th winding turn, and is the radius (R2K) of the K-1-th winding turn and the radius (R2 K-1 ) can be calculated as the difference between

[0098] For ease of explanation, only three second segments 210F are shown among the multiple second segments 210F present on the second electrode 200K of the Kth winding turn. The multiple second segments 210F present on the second electrode 200K of the Kth winding turn are bent toward the core portion 10C, and the second segments 210F of the second electrode 200K of the Kth winding turn overlap on the second electrode 200K-1 of the K-1th winding turn. In the present invention, the overlap ratio of the second segments 210F of the Kth winding turn to the K-1th winding turn is defined as (N2 K *A2 K ) / (2πR2 K-1 Specifically, assuming that the second electrode 200K of the K-th winding turn and the second electrode 200K-1 of the K-1-th winding turn are concentric circles, the width (A2 K ) and the number of second segments 210F in the K-th winding turn (N2 K ) and divide the result by the circumference value of the (K-1)th winding turn to obtain the overlap ratio.

[0099] By multiplying this overlap ratio by the thickness (t2) of the second section 210F, the lamination thickness of the second section 210F of the Kth winding turn relative to the K-1th winding turn can be calculated. In this embodiment, the height difference between the bending points (BP) of the second sections 210F for each winding turn is in the range of 50% to 300% of the lamination thickness calculated in this way.

[0100] Suppose, L2 K -L2 K-1 The value of t2*(N2 K *A2 K ) / (2πR2 K-1 ), the height difference between the bending points (BP) of the second section 210F per winding turn is insufficient, making it impossible to prevent irregular deformation of some of the second section 210F when the second section 210F is bent.

[0101] Also, if L2 K -L2 K-1 The value of t2*(N2 K *A2 K ) / (2πR2 K-1 If the height difference exceeds 300% of the bending point (BP) of the second section 210F per winding turn, the height difference between the bending points (BP) of the second section 210F becomes too large, resulting in a large amount of unnecessary space along the height direction of the jelly roll electrode assembly 10. This is not appropriate because it reduces the capacity and energy density of the secondary battery.

[0102] 13, a second exposed portion 210E is formed by exposing a portion of the second electrode current collector 210 of the second electrode 200, and the second exposed portion 210E may include rectangular second sub-sections 210F spaced apart at regular intervals.

[0103] When the second section 210F has a rectangular shape, the A2 K is the width of the connecting end of the second segment 210F, W2 KHere, the connecting end of the second segment 210F is the portion of the second segment 210F that extends from the second exposed portion 210E. In FIG. 13, the connecting end can correspond to the upper side when the second segment 210F is viewed as a virtual rectangle. Since the width of the second segment 210F, which is a rectangle, is constant, the width (A2 K ) is the width (W2 K ) That is, when the second segment 210F has a rectangular shape, A2 K The value is W2 K The value may be used as is.

[0104] Figure 14 is a schematic view showing a state in which a segment of a specific winding turn is placed on the previous winding turn in an electrode assembly according to a modified embodiment of the present invention, and Figure 15 is a partial view showing a portion of a second electrode according to a modified embodiment of the present invention.

[0105] 14 and 15 together with FIGS. 3 to 5, as described above, in the K-th winding turn (where K>2) of the jelly roll structure along the radial direction (dr) of the jelly roll structure, the length from the end of the second electrode current collector 210 in the first direction (d1) to the bending point (BP) of the second exposed portion 210E is defined as L2 K It can be defined as follows. Also, L2 K -L2 K-1 is t2*(N2 K *A2 K ) / (2πR2 K-1 ) can satisfy the condition of 50% or more and 300% or less. Here, t2 is the thickness of the second cut piece 210F. K is the number of second segments 210F along the circumferential direction (dc) in the K-th winding turn. K is the width of the second segment 210F of the K-th winding turn placed on the K-1-th winding turn. K-1is the radius of the (K-1)th winding turn. K is the number of winding turns of the second electrode 200, and is an integer greater than 2. A detailed description of this will be omitted as it overlaps with the content described above.

[0106] 15, a second electrode current collector 210 of a second electrode 200 is exposed to form a second exposed portion 210E, and the second exposed portion 210E may include trapezoidal second sub-segments 210F spaced apart at regular intervals.

[0107] When the second segment 210F has an equilateral trapezoidal shape, the A2 K is W2 K -2*(D2 K / tanθ2) can be calculated. K is the width of the connecting end of the second segment 210F. The connecting end of the second segment 210F is the portion where the second segment 210F extends from the second exposed portion 210E. K is the interval between the K-th winding turn and the K-1-th winding turn. Specifically, D2 K is the distance between the second electrode 200K in the K-th winding turn and the second electrode 200K-1 in the K-1th winding turn, and the radius (R2K) in the K-1th winding turn and the radius (R2 K-1 ) and θ2 is the interior angle of the connecting end of the trapezoidal second segment 210F.

[0108] The connecting end of the second segment 210F is the portion of the second segment 210F extending from the second exposed portion 210E, and refers to the relatively long side when the second segment 210F is viewed as a single imaginary trapezoid. Also, the connecting end interior angle (θ2) refers to the interior angle between the long side and both sides when the second segment 210F is viewed as a single imaginary trapezoid. The connecting end interior angle (θ2) is an acute angle in the trapezoid structure. When the second segment 210F is trapezoidal, A2 K The value is W2 K The value should not be used as is, A2 K is W2 K -2*(D2 K It is preferable to calculate it as follows:

[0109] Hereinafter, a secondary battery including an electrode assembly according to an embodiment of the present invention will be described in detail.

[0110] FIG. 16 is a cross-sectional view of a secondary battery including an electrode assembly according to an embodiment of the present invention.

[0111] 3 and 16, a secondary battery according to an embodiment of the present invention includes an electrode assembly 10. In Fig. 16, the secondary battery according to this embodiment is described as a cylindrical battery, but this is only one example structure of a secondary battery according to other embodiments of the present invention, and secondary batteries according to other embodiments of the present invention may be prismatic batteries.

[0112] The secondary battery according to this embodiment may include a battery can 20 that houses an electrode assembly 10 and has an open top, and a cap assembly 30 that is coupled to the open top of the battery can 20. A gasket 50 may be interposed between the battery can 20 and the cap assembly 30.

[0113] The battery can 20 according to this embodiment may be a cylindrical case with an open top, and may contain the electrode assembly 10 and an electrolyte (not shown) in the internal storage space, and may include a metal material such as aluminum (Al).

[0114] The cap assembly 30 according to this embodiment may include a plate-shaped top cap 31 and a connecting plate 32 electrically and mechanically coupled to the top cap 31. The top cap 31 includes an electrically conductive metal material and may cover the open top of the battery can 20. The top cap 31 may be electrically connected to the first section 110F of the first exposed portion 110E and may be electrically insulated from the battery can 20 by the gasket 50. Therefore, the top cap 31 according to this embodiment may function as an external terminal of the first electrode 100 of the secondary battery.

[0115] Regarding the electrical connection between the top cap 31 and the first portion 110F in detail, the secondary battery according to this embodiment may further include a first current collecting plate 41 located on the upper portion of the electrode assembly 10. The first current collecting plate 41 may include a conductive metal material such as aluminum, copper, steel, or nickel, and is electrically connected to the first portion 110F of the electrode assembly 10. The electrical connection may be achieved by welding. A lead 60 is connected to the first current collecting plate 41. The lead 60 may extend toward the upper portion of the electrode assembly 10 and be connected to the connecting plate 32. In another embodiment, the lead 60 may be directly connected to the lower surface of the top cap 31. The connection between the lead 60 and other components may be achieved by welding. Alternatively, the first current collecting plate 41 may be integrally formed with the lead 60. In this case, the lead 60 may have a long plate shape extending outward from near the center of the first current collecting plate 41.

[0116] The first current collecting plate 41 may have a plurality of radially formed projections and recesses (not shown) on its underside. When the radial projections and recesses are provided, the first current collecting plate 41 can be pressed to press the projections and recesses into the bent first sub-segment 110F. The first current collecting plate 41 and the first sub-segment 110F can be joined by, for example, laser welding. Laser welding can be performed by partially melting the base material of the first current collecting plate 41. In a modified example, the first current collecting plate 41 and the first sub-segment 110F can be welded using solder. In this case, the solder may have a lower melting point than the first current collecting plate 41 and the first sub-segment 110F. Laser welding can be replaced by resistance welding, ultrasonic welding, spot welding, etc.

[0117] Meanwhile, the secondary battery according to this embodiment may further include a second current collecting plate 42 located below the electrode assembly 10. Specifically, the second current collecting plate 42 may be located between the electrode assembly 10 and the bottom 20F of the battery can 20. The second current collecting plate 42 may include a conductive metal material such as aluminum, copper, steel, or nickel, and is electrically connected to the second portion 210F of the electrode assembly 10. One side of the second current collecting plate 42 may be coupled to the second portion 210F, and the opposite side of the second current collecting plate 42 may be coupled to the bottom 20F of the battery can 20. Welding may be used to connect the second current collecting plate 42. As a result, the battery can 20 according to this embodiment may function as an external terminal for the second electrode 200 of the secondary battery.

[0118] Meanwhile, the secondary battery according to this embodiment may include an insulating plate 70 .

[0119] The insulating plate 70 may cover the first current collecting plate 41. By covering the upper surface of the first current collecting plate 41, the insulating plate 70 may prevent the first current collecting plate 41 from contacting the battery can 20, particularly a beading portion 20B of the battery can 20 (described later). In addition, the insulating plate 70 may have a separate lead hole through which the lead 60 extending upward from the first current collecting plate 41 can be extracted. The lead 60 may be extracted upward through the lead hole of the insulating plate 70 and coupled to the lower surface of the connecting plate 32 or the lower surface of the top cap 31.

[0120] The peripheral region of the insulating plate 70 is interposed between the first current collector plate 41 and the beading portion 20B of the battery can 20, thereby fixing the electrode assembly 10 and the first current collector plate 41 together. This limits the axial movement of the electrode assembly 10 and the first current collector plate 41 together, improving the assembly stability of the secondary battery. The insulating plate 70 may be made of an insulating polymer resin. For example, the insulating plate 70 may include one or more materials selected from the group consisting of polyethylene, polypropylene, polyimide, and polybutylene terephthalate.

[0121] Meanwhile, the battery can 20 according to this embodiment may include a crimping part 20C and a beading part 20B.

[0122] The crimping portion 20C is a portion of the battery can 20 that surrounds the cap assembly 30 and the gasket 50. Specifically, the battery can 20 and the cap assembly 30 can be crimped together with the gasket 50 therebetween. That is, the battery can 20 and the cap assembly 30 are connected together by crimping. This allows the crimping portion 20C to be formed in the battery can 20. More specifically, after the gasket 50 is positioned between the battery can 20 and the cap assembly 30, the crimping is performed by bending one upper end of the battery can 20 in the direction where the cap assembly 30 is positioned.

[0123] The beading portion 20B refers to a portion of the side surface of the battery can 20 that is indented toward the center in an area above the electrode assembly 10, and serves to stably position the cap assembly 30 and prevent the electrode assembly 10 from moving. That is, the cap assembly 30 and the gasket 50 surrounding it according to this embodiment can be secured onto the beading portion 20B of the battery can 20. The above-described crimping connection is performed with the cap assembly 30 and the gasket 50 surrounding it secured to the beading portion 20B.

[0124] The gasket 50 according to this embodiment is positioned between the battery can 20 and the cap assembly 30 to improve the sealing performance of the secondary battery. In addition, the gasket 50 may include an electrically insulating material to prevent a short circuit from occurring between the battery can 20, which functions as a terminal for the second electrode 200, and the cap assembly 30, which functions as a terminal for the first electrode 100. The gasket 50 may include one or more materials selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and perfluoroalkoxy alkane (PFA).

[0125] FIG. 17 is a view illustrating a method of bending a first segment of a first electrode according to an embodiment of the present invention.

[0126] 5 and 17, in order to form a flat surface area in the first direction (d1) of the electrode assembly 10, the first segment 110F of the first electrode 100 is bent toward the core portion as described above. However, the first segment 110F is not bent all at once. Instead, the first segment 110F is first bent slightly to have a certain inclination. Then, after the first electrode 100 is wound, strong pressure is applied to the slightly bent first segment 110F to completely bend the first segment 110F, as shown in FIGS. 3 and 5.

[0127] In this case, rolls R1 and R2 having inclined portions (SP) can be used to slightly bend the first segment 110F to have a predetermined inclination, as shown in FIG. 17. Specifically, the first electrode 100 having the first segment 110F can be inserted between two rolls R1 and R2 along the d3 direction. The two rolls R1 and R2 have inclined portions (SP) with a predetermined inclination at the point where the first segment 110F is inserted, and the inclined portions (SP) may be frustum-shaped. The inserted first segment 110F is bent by the inclined portions (SP), and the point where the first segment 110F is bent by the inclined portions (SP) corresponds to the bending point (BP). While the first electrode 100 is being inserted, the roll R2 having the inclined portions (SP) can gradually move in the d4 direction. That is, the roll (R2) having the inclined portion (SP) can be gradually moved in the direction in which the first segment 110F protrudes from the first electrode 100. As such, the roll (R2) having the inclined portion (SP) can be designed to gradually move, so that the height of the bending point (BP) in the first direction (d1) for each winding turn of the first electrode 100 gradually increases.

[0128] Although not specifically shown, the height of the bending point (BP) for each winding turn of the second segment 210F of the second electrode 200 can also be adjusted in the same manner as the first electrode 100.

[0129] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are used for convenience of explanation and may differ depending on the position of the object of interest, the position of the observer, etc.

[0130] A plurality of secondary batteries according to the present embodiment may be assembled to form a battery module, and one or more battery modules may be mounted together with various control and protection systems, such as a battery management system (BMS), a battery disconnect unit (BDU), and a cooling system, to form a battery pack.

[0131] The secondary battery, the battery module, or the battery pack can be applied to various devices, specifically, transportation means such as electric bicycles, electric cars, and hybrids, and energy storage systems (ESS), but is not limited thereto, and can be applied to various devices that can use secondary batteries.

[0132] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0133] 10 Electrode Assembly 100 1st electrode 110 First electrode current collector 110E 1st exposed part 110F 1st section 120 1st active material section 200 2nd electrode 210 Second electrode current collector 210E 2nd exposed part 210F 2nd section 220 2nd active material section 300 Separation membrane

Claims

1. first electrode; a second electrode; and a separator interposed between the first electrode and the second electrode; the first electrode, the second electrode, and the separator are wound together to form a jelly roll structure; the first electrode includes a first electrode current collector and a first active material portion formed by applying an electrode active material to one or both surfaces of the first electrode current collector; the second electrode includes a second electrode current collector and a second active material portion formed by applying an electrode active material to one or both surfaces of the second electrode current collector, a first exposed portion of the first electrode current collector, on which the electrode active material is not applied, extends in a first direction; a second exposed portion of the second electrode current collector, on which the electrode active material is not applied, extends in a second direction opposite to the first direction; the first exposed portion and the second exposed portion have bending points for each winding turn; a length from the end of the first electrode current collector in the second direction to the bending point of the first exposed portion gradually increases with each winding turn of the jelly roll structure in the radial direction, The radial direction is a direction from the core portion to the outer portion of the jelly roll structure.

2. the first exposed portion includes a plurality of first sections that can be bent independently of each other; The electrode assembly according to claim 1 , wherein the bending point of the first exposed portion is a point at which the first segment is bent.

3. In a K-th winding turn (where K>2) of the jelly roll structure along the radial direction of the jelly roll structure, the length from the end of the first electrode current collector in the second direction to the bending point of the first exposed portion is defined as L1. Ｋ When we define L1 Ｋ -L1 Ｋ－１ is t1*(N1 Ｋ *A1 Ｋ ) / (2πR1 Ｋ－１ ) and meet the following criteria: 50% or more and 300% or less. t1 is the thickness of the first slice, N1 Ｋ is the number of the first segments along the circumferential direction in the K-th winding turn, A1 Ｋ is the width of the first segment of the Kth winding turn placed on the K-1th winding turn, The R1 Ｋ－１ 3. The electrode assembly of claim 2, wherein k is the radius at the K-1 th winding turn.

4. 4. The electrode assembly of claim 3, wherein the first segment is rectangular in shape.

5. A1 Ｋ is the width of the connecting end of the first segment, W1 Ｋ 5. The electrode assembly of claim 4, wherein:

6. 4. The electrode assembly of claim 3, wherein the first segment is trapezoidal in shape.

7. A1 Ｋ is W1 Ｋ −2*(D1 Ｋ / tan θ1), W1 Ｋ is the width of the connecting end of the first segment, D1 Ｋ is the interval between the K-th winding turn and the K-1-th winding turn, 7. The electrode assembly according to claim 6, wherein θ1 is an interior angle of a connecting end of the first trapezoidal segment.

8. 2. The electrode assembly according to claim 1, wherein a length from the end of the second electrode current collector in the first direction to the bending point of the second exposed portion gradually increases with each winding turn of the jelly roll structure in the radial direction.

9. the second exposed portion includes a plurality of second sections that can be bent independently of each other; The electrode assembly of claim 8 , wherein the bending point of the second exposed portion is a point where the second segment is bent.

10. In the K-th winding turn (where K>2) of the jelly roll structure along the radial direction of the jelly roll structure, the length from the end of the second electrode current collector in the first direction to the bending point of the second exposed portion is defined as L2 Ｋ When we define L2 Ｋ -L2 Ｋ－１ is t2 * (N2 Ｋ *A2 Ｋ ) / (2πR2 Ｋ－１ ) and meet the following criteria: 50% or more and 300% or less. t2 is the thickness of the second slice, N2 Ｋ is the number of the second segments along the circumferential direction in the K-th winding turn, Said A2 Ｋ is the width of the second segment of the K-th winding turn placed on the K-1-th winding turn, The R2 Ｋ－１ 10. The electrode assembly of claim 9, wherein k is the radius at the K-1 th winding turn.

11. 11. The electrode assembly of claim 10, wherein the second segment is rectangular in shape.

12. Said A2 Ｋ is the width of the connecting end of the second segment, W2 Ｋ The electrode assembly of claim 11, wherein the calculated

13. The electrode assembly of claim 10, wherein the second segment is trapezoidal in shape.

14. Said A2 Ｋ is W2 Ｋ −2*(D2 Ｋ / tan θ2), W2 Ｋ is the width of the connecting end of the second segment, D2 Ｋ is the interval between the K-th winding turn and the K-1-th winding turn, The electrode assembly according to claim 13, wherein θ2 is an interior angle of a connecting end of the second trapezoidal segment.

15. A secondary battery comprising the electrode assembly according to any one of claims 1 to 14.

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