Electrode assembly and secondary battery comprising same

Abstract

An electrode assembly according to an embodiment of the present invention comprises, a 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 so as 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 surface 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 surface or both surfaces of the second electrode current collector. A first exposed portion of the first electrode current collector, to which the electrode active material is not applied, extends in a first direction, and a second exposed portion of the second electrode current collector, to 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 a bending point with regard to each winding turn. The length from an end portion of the first electrode current collector in the second direction to the bending point of the first exposed portion gradually increases with regard to each winding turn in the radial direction of the jelly roll structure. The radial direction is directed from the core portion of the jelly roll structure toward the outer portion thereof.

Description

Electrode assembly and secondary battery including the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0157262, filed November 14, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly, to a jelly roll-shaped electrode assembly and a secondary battery including the same.

[0004] Secondary batteries, which have high applicability according to product group and electrical characteristics such as high energy density, are widely used not only in portable devices but also in electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by electrical power sources.

[0005] These secondary batteries are attracting attention as a new energy source for environmental friendliness and energy efficiency because they not only have the primary advantage of drastically reducing the use of fossil fuels, but also have the advantage of producing no byproducts from energy use.

[0006] Currently, widely used types of secondary batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. The operating voltage of these unit secondary batteries is approximately 2.5 V to 4.5 V. Therefore, when a higher output voltage is required, multiple secondary batteries, i.e., battery cells, are connected in series to form a battery module or battery pack. In addition, a number of battery cells are connected in parallel depending on the charge and 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 type can be set in various ways depending on the required output voltage or charge and discharge capacity.

[0007] The electrode assembly built into the battery cell is a power plant capable of charging and discharging, consisting of a stacked structure of a cathode, a separator, and anode, and is classified into jellyroll type, stack type, and stack / folding type. The jellyroll type is a form in which a separator is interposed between long sheet-shaped cathodes and anodes coated with active materials and wound around them. The stack type is a form in which a plurality of cathodes and anodes of a predetermined size are sequentially stacked with a separator interposed between them. The stack / folding type is a composite structure of the jellyroll type and the stack type. Among them, the jellyroll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per weight.

[0008] Secondary batteries, or battery cells, are classified into cylindrical batteries in which the electrode assembly is housed in a cylindrical battery can, square batteries in which the electrode assembly is housed in a square battery can, and pouch-type batteries in which the electrode assembly is housed in a pouch-type case made of aluminum laminate sheet, depending on the shape of the battery case. Among these, cylindrical batteries have the advantages of relatively large capacity and structural stability.

[0009] In the case of a cylindrical battery, an insulator separator is interposed between the positive and negative electrodes, and this is wound to form a jelly roll-shaped electrode assembly, which is then inserted into the battery can to form the battery. In addition, a strip-shaped electrode tab may be connected to each of the non-coated portions of the positive and negative electrodes, and the electrode tab electrically connects the electrode assembly and the electrode terminal exposed to the outside. For reference, the positive electrode terminal is a cap assembly of a sealing body that seals the open top of the battery can, and the negative electrode terminal is the battery can itself. However, in a conventional cylindrical battery having such a structure, there was a problem that the resistance was high, a lot of heat was generated, and the current collection efficiency was poor because the current was concentrated on the strip-shaped electrode tab connected to the positive or negative non-coated portion.

[0010] Resistance and heat generation are not major issues for small cylindrical batteries with form factors such as 1865 (diameter: 18 mm, height: 65 mm) or 2170 (diameter: 21 mm, height: 70 mm). However, increasing the form factor for cylindrical batteries for electric vehicles can lead to problems such as excessive heat generation around the electrode tabs during rapid charging, potentially leading to ignition of the cylindrical battery.

[0011] To solve these problems, a secondary battery having a structure with improved current collection efficiency, a so-called tab-less secondary battery, was proposed by designing exposed portions where positive and negative current collectors are exposed at the top and bottom of a jelly roll-shaped electrode assembly, respectively, and welding a current collector plate to these exposed portions.

[0012] However, in the jellyroll-shaped electrode assembly included in such tab-less secondary batteries, in order to bond the exposed portions to the current collector, the exposed portions may be bent toward the core of the jellyroll electrode assembly. That is, the exposed portions may be bent toward the core of the jellyroll electrode assembly, and these exposed portions may be bonded to the current collector while being laminated for each winding turn. However, due to the characteristics of the jellyroll-shaped electrode assembly, the thickness of the portion where the exposed portions are laminated, that is, the laminate thickness, increases as it goes toward the core of the jellyroll electrode assembly. Accordingly, the laminated exposed portions may be irregularly deformed and distorted, which may directly lead to a problem of fire occurring in the secondary battery including the electrode assembly. Specifically, if the separator is damaged due to the irregular deformation of the laminated exposed portions, a short circuit may occur between the positive and negative electrodes, which may cause fire or explosion of the secondary battery.

[0013] Accordingly, there is a need for an improvement method that can prevent irregular deformation of the laminated exposed portions in tab-less secondary batteries.

[0014] The problem to be solved by the present invention is to provide an electrode assembly in the form of a jelly roll in which the exposed portion of the electrode current collector functions as a terminal, which can prevent irregular deformation from occurring when bendable exposed portions are laminated, and a secondary battery including the same.

[0015] However, the problems to be solved by the embodiments of the present invention are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention.

[0016] An electrode assembly according to one embodiment of the present invention comprises: a first electrode; a second electrode; and a separator interposed between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the separator are wound together to form a jellyroll structure. The first electrode comprises 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 comprises 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, and 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. For each winding turn 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 gradually increases. The radial direction is a direction from the core portion of the jelly roll structure toward the outer portion.

[0017] The first exposed portion may include a plurality of first segments that are independently bent. The bending point of the first exposed portion may be a point at which the first segments are bent.

[0018] In the Kth winding turn of the jelly roll structure (provided that K>2) 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 L1. K When defined as 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 thickness of the first segment, and the N1 K is the number of the first segments along the circumferential direction in the Kth winding turn, and the A1 K is 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-1st winding turn.

[0019] The above first segment may be in the shape of a square.

[0020] A1 above K is the width of the connecting end of the first segment, W1 K can be calculated as

[0021] The above first segment may have a trapezoidal shape.

[0022] A1 above K is W1 K -2*(D1 K / tanθ1) can be calculated. The above W1 K is the width of the connecting end of the first segment, and D1 K is the interval between the Kth winding turn and the K-1th winding turn, and θ1 is the interior angle of the connecting section of the first segment having a trapezoidal shape.

[0023] For each winding turn in 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 may gradually increase.

[0024] The second exposed portion may include a plurality of second segments that are independently bent. The bending point of the second exposed portion may be a point at which the second segments are bent.

[0025] In the Kth winding turn of the jelly roll structure (provided that 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 L2. K When defined as L2 K -L2 K-1 is, t2*(N2 K *A2 K ) / (2πR2 K-1 ) can satisfy 50% or more and 300% or less of the above. The above t2 is the thickness of the second segment, and the above N2 K is the number of the second segments along the circumferential direction in the Kth winding turn, and the 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-1st winding turn.

[0026] The above second segment may be in the shape of a square.

[0027] A2 above K is the width of the connecting end of the second segment, W2 K can be calculated as

[0028] The above second segment may have a trapezoidal shape.

[0029] A2 above K is W2 K -2*(D2 K / tanθ2) can be calculated. The above W2 K is the width of the connecting end of the second segment, and D2 K is the interval between the Kth winding turn and the K-1th winding turn, and θ2 is the interior angle of the connecting section of the second segment having a trapezoidal shape.

[0030] A secondary battery according to one embodiment of the present invention includes the electrode assembly.

[0031] According to embodiments of the present invention, in a jelly-roll-shaped electrode assembly in which the exposed portion of an electrode current collector functions as a terminal, irregular deformation of the laminated exposed portions can be prevented by setting the bending point positions of each winding turn of the exposed portion differently in the radial direction. Accordingly, short circuiting between the positive and negative electrodes can be prevented, and fire or explosion caused thereby can be prevented.

[0032] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0033] FIG. 1 is a drawing showing an electrode assembly according to one embodiment of the present invention before being wound.

[0034] Figure 2 is a drawing showing an electrode assembly being wound according to one embodiment of the present invention.

[0035] Figure 3 is a drawing showing an electrode assembly according to one embodiment of the present invention in a state where the winding is completed.

[0036] Figure 4 is a plan view of the electrode assembly of Figure 3 viewed from above.

[0037] Fig. 5 is a cross-sectional view showing a cross-section taken along the cutting line A-A' of Fig. 4.

[0038] Fig. 6 is a cross-sectional view showing a cross-section of an electrode assembly according to a comparative example of the present invention.

[0039] FIG. 7 is a schematic drawing of an electrode assembly according to one embodiment of the present invention, in which a first segment in a specific winding turn is placed on a previous winding turn.

[0040] FIG. 8 is a partial drawing showing a part of a first electrode according to one embodiment of the present invention.

[0041] Figure 9 is a schematic drawing showing only the first electrode in the Kth winding turn.

[0042] FIG. 10 is a schematic drawing of an electrode assembly according to a modified embodiment of the present invention, in which a segment at a specific winding turn is placed on the previous winding turn.

[0043] FIG. 11 is a partial drawing showing a part of a first electrode according to a modified embodiment of the present invention.

[0044] FIG. 12 is a schematic drawing of an electrode assembly according to one embodiment of the present invention, in which a second segment in a specific winding turn is placed on a previous winding turn.

[0045] FIG. 13 is a partial drawing showing a part of a second electrode according to one embodiment of the present invention.

[0046] FIG. 14 is a schematic drawing of an electrode assembly according to a modified embodiment of the present invention, in which a segment at a specific winding turn is placed on the previous winding turn.

[0047] FIG. 15 is a partial drawing showing a part of a second electrode according to a modified embodiment of the present invention.

[0048] FIG. 16 is a cross-sectional view of a secondary battery including an electrode assembly according to one embodiment of the present invention.

[0049] FIG. 17 is a drawing for explaining a method of bending a first segment of a first electrode according to one embodiment of the present invention.

[0050] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0051] In order to clearly explain the present invention, parts that are not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0052] Furthermore, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to the illustrated components. In the drawings, the thicknesses are enlarged to clearly represent various layers and regions. Furthermore, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0053] Furthermore, when we say that a layer, membrane, region, plate, or other part is "on" or "over" another part, this includes not only cases where it is "directly on" the other part, but also cases where there are other parts in between. Conversely, when we say that a part is "directly on" another part, it means that there are no other parts in between. Furthermore, saying that a part is "on" or "over" a reference part means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "over" the direction opposite to gravity.

[0054] Additionally, throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0055] Additionally, throughout the specification, when we say "in plan", we mean when the target portion is viewed from above, and when we say "in cross section", we mean when the target portion is viewed from the side in a cross-section cut vertically.

[0056] FIG. 1 is a drawing showing an electrode assembly according to an embodiment of the present invention before being wound. FIG. 2 is a drawing showing an electrode assembly according to an embodiment of the present invention being wound. FIG. 3 is a drawing showing an electrode assembly according to an embodiment of the present invention after being wound. FIG. 4 is a plan view of the electrode assembly of FIG. 3 as viewed from above. FIG. 5 is a cross-sectional view taken along the line A-A' of FIG. 4.

[0057] Referring to FIGS. 1 to 5, an electrode assembly (10) according to one 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). In addition, the first electrode (100), the second electrode (200), and the separator (300) are rolled together to form a jellyroll structure. That is, the electrode assembly (10) according to the present embodiment is an electrode assembly in the form of a jellyroll. In addition, in order to prevent the first electrode (100) and the second electrode (200) from coming into contact with each other when rolled into the form of a jellyroll, a separator (300) may be additionally disposed on the outside 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 illustrated in FIG. 1, an electrode assembly (10) according to the present embodiment can be manufactured by winding along the winding direction (dw) while the second electrode (200), one separator (300), the first electrode (100) and the other separator (300) are stacked.

[0058] 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) on which the electrode active material is not applied extends in the first direction (d1). Specifically, a portion of the first electrode current collector (110) on which the electrode active material is not applied and on which the first electrode current collector (110) is exposed may correspond to the first exposed portion (110E).

[0059] 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) on which the electrode active material is not applied extends in a second direction (d2) opposite to the first direction (d1). Specifically, a portion of the second electrode current collector (210) on which the electrode active material is not applied and on which the second electrode current collector (210) is exposed may correspond to the second exposed portion (210E).

[0060] 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 in which the central axis of the rolled cylindrical electrode assembly (10) is connected. In Fig. 2, the axial direction of the electrode assembly (10) corresponds to the direction parallel to the z-axis.

[0061] For example, one of the first electrode (100) and the second electrode (200) may be a positive electrode, and the other may be a negative electrode. That is, one of the first electrode current collector (110) and the second electrode current collector (210) may be a positive electrode current collector, and the other may be a negative electrode current collector. In addition, one of the first active material portion (120) and the second active material portion (220) may be a positive electrode active material portion coated with a positive electrode active material, and the other may be a negative electrode active material portion coated with a negative electrode active material.

[0062] 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 without limitation. Furthermore, the positive electrode active material applied to the positive electrode and the negative electrode active material applied to the negative electrode may be made of any active material known in the art without limitation.

[0063] The positive electrode current collector may be a thin metal foil, and generally has a thickness of 3 to 500 micrometers. The positive electrode current collector is not particularly limited as long as it has high conductivity and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may have fine unevenness on its surface to increase the adhesiveness of the positive electrode active material, and may be in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0064] The above positive electrode active material has the general chemical formula A[A x M y ]O 2+z (A comprises at least one element selected from Li, Na, and K; M comprises 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; stoichiometric coefficients x, y, and z are selected such that the compound maintains electrical neutrality) may include an alkali metal compound represented by the formula (I).

[0065] In another example, the positive electrode active material is an alkali metal compound xLiM as disclosed in US6,677,082, US6,680,143, etc. 1 O 2­ (1x)Li2M 2 O3(M 1contains at least one element having an average oxidation state of 3; M 2 contains at least one element having an average oxidation state of 4; 0≤x≤1).

[0066] In another example, the positive electrode active material has the general chemical formula Li a M 1 x Fe 1­x M 2 y P 1­y M 3 z O 4­z (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 may be a lithium metal phosphate represented by Li3M2(PO4)3 [M comprises at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Al, Mg and Al], wherein the compound comprises a halogen element optionally including F; 0 < a ≤2, 0 ≤ x ≤ 1, 0 ≤ y < 1, 0 ≤ z < 1; the stoichiometric coefficients a, x, y and z are selected so that the compound remains electrically neutral].

[0067] The above negative electrode current collector may be a thin metal foil, and generally has a thickness of 3 to 500 micrometers. The negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, similar to the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine unevenness on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0068] The above-mentioned negative active material may be carbon material, lithium metal or a lithium metal compound, silicon or a silicon compound, tin or a tin compound, etc. Metal oxides such as TiO2 and SnO2 with a potential of less than 2 V may also be used as negative active materials. Low-crystalline carbon and high-crystalline carbon may both be used as carbon materials.

[0069] The above separator is interposed between the anode and cathode, and is a thin insulating film with high ion permeability and mechanical strength. The pore diameter of the separator is typically 0.01 to 10 micrometers, and the thickness is typically 5 to 300 micrometers. Examples of such separators include sheets or non-woven 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 may also function as the separator.

[0070] Meanwhile, in the electrode assembly (10) according to the present embodiment, the first exposed portion (110E) and the second exposed portion (210E) have a bending point (BP) for each winding turn. As will be described later, the electrode assembly (10) according to the present embodiment has a tab-less structure in which the first exposed portion (110E) and the second exposed portion (210E) are directly connected to a current collector plate, rather than having electrode tabs attached to the electrode current collector, thereby guiding electrical connection. At this time, in order to join 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 in a direction toward the core portion (10C, Core part) of the electrode assembly (10) of the jellyroll structure. Here, the point where the first exposed portion (110E) and the second exposed portion (210E) bend is referred to as the bending point (BP). In addition, the core portion (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 at the center of the electrode assembly (10) which is a jellyroll structure. Here, viewing the electrode assembly (10) which is a jellyroll structure from above means viewing the electrode assembly (10) in the axial direction on the xy plane, that is, along the z-axis direction or the -z-axis direction, as in FIG. 4.

[0071] In this embodiment, for each winding turn along the radial direction (dr) of the jelly roll structure, the length (L1) from the end of the second direction (d2) of the first electrode current collector (110) to the bending point (BP) of the first exposed portion (110E) K-1 , L1 K) gradually increases. Here, the radial direction (dr) of the jellyroll structure means the direction from the core portion (10C) to the outer portion (10U) of the jellyroll structure. The outer portion (10U) of the jellyroll structure refers to the outer peripheral portion of the jellyroll structure when the electrode assembly (10), which is a jellyroll structure, is viewed from above. Therefore, the radial direction (dr) means the direction away from the core portion (10C) when the electrode assembly (10), which is a jellyroll structure, is viewed from above. In addition, “winding turns” refer to each portion where the first electrode (100) being wound meets a specific radial direction (dr). That is, “bending points (BP) per winding turn” refer to each portion where the first exposed portion (110E) is bent at each portion where the first electrode (100) being wound meets a specific radial direction (dr).

[0072] That is, in the present embodiment, the height of the bending point (BP) of each winding turn of the first exposed portion (110E) in the first direction (d1) may gradually increase as it goes in the radial direction (dr). As described above, since the first exposed portion (110E) has a bending point (BP) while being bent in the direction toward the core portion (10C, Core part), the thickness of the portion where the first exposed portions (110E) are laminated, i.e., the laminated thickness, increases as it goes toward the core portion (10C). Here, the direction toward the core portion (10C) corresponds to the opposite direction to the radial direction (dr).

[0073] As the number of winding turns increases, the number of first exposed portions (110E) stacked along the radial direction (dr) increases, and the first exposed portions (110E) that are excessively stacked in a limited space may be irregularly deformed. Due to such irregular deformation of the first exposed portions (110E), the separator (300) and the like may be damaged, which may cause a short circuit between the first electrode (100) and the second electrode (200). This problem will be described again together with the comparative example of the present invention shown in Fig. 6.

[0074] Fig. 6 is a cross-sectional view showing a cross-section of an electrode assembly according to a comparative example of the present invention.

[0075] Referring to FIG. 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'). In addition, a first exposed portion (110E') of the first electrode current collector (110') on which an electrode active material is not applied may extend in a first direction (d1), and a second exposed portion (210E') of the second electrode current collector (210') on which an electrode active material is not applied may extend in a second direction (d2) opposite to the first direction (d1). In addition, the first exposure portion (110E') includes first segments (110F') described below, and the first segments (110F') have a bending point (BP). In addition, the second exposure portion (210E') includes second segments (210F') described below, and the second segments (210F') have a bending point (BP).

[0076] Unlike the electrode assembly of the present embodiment described above, in the electrode assembly according to the present comparative example, 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 constant for each winding turn along the radial direction (dr) of the jellyroll structure. That is, the height of the bending point (BP) of the first segment (110F') of the first exposed portion (110E') is constant for each winding turn. When a plurality of first exposed portions (110E') are bent and stacked for each winding turn, as in the present comparative example, if the height of the bending point (BP) of the first segment (110F') is constant, some of the first exposed portions (110E') may exhibit irregular deformation and be distorted. In particular, the first segment (110F') portion close to the core may not maintain a direction perpendicular to the axial direction and may bend further in the direction indicated by “I”. The first segments (110F') 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 ignition or explosion of the secondary battery.

[0077] Referring again to FIG. 5, in the case of the electrode assembly (10) according to the present embodiment, in order to prevent the problem of such short-circuit occurrence, as described above, for each winding turn along the radial direction (dr) of the jellyroll structure, 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 K-1 , L1 K) gradually increases. That is, the height of the bending point (BP) of the first exposed portion (110E) per winding turn in the first direction (d1) is designed to gradually increase as it goes in the radial direction (dr). In this embodiment, since the first exposed portions (110E) per winding turn are sequentially stacked with a height difference per winding turn, it is possible to prevent some of the first exposed portions (110E) from being irregularly deformed and crushed. Accordingly, the occurrence of a short between the first electrode (100) and the second electrode (200) due to damage to the separator (300) can be minimized.

[0078] Meanwhile, according to the present embodiment, the first exposed portion (110E) may include a plurality of first segments (110F) that are independently bent, and the bending point (BP) of the first exposed portion (110E) described above may be a point where the first segments (110F) are bent. Specifically, the first exposed portion (110E) may not be formed in a single piece, but may have cut grooves of a predetermined depth provided at a predetermined interval. That is, the first exposed portion (110E) may be divided into first segments (110F) that are areas between these cut grooves. If the first exposed portion (110E) is formed in a single piece, when the first exposed portion (110E) is bent in the direction where the core portion (10C) is located, the first exposed portion (110E) may be irregularly wrinkled because the bending space is narrow. To prevent such problems, it is preferable to divide the first exposed portion (110E) into a plurality of first segments (110F) and then bend these first segments (110F).

[0079] In FIGS. 3 and 4, a plurality of first segments (110F) are bent and overlapped in multiple layers to form a flat surface area in the first direction (d1) of the electrode assembly (10). When a collector plate, which will be described later, comes into contact with the surface area of ​​the electrode assembly (10), the electrical connection of the electrode assembly (10) can be guided. That is, a tab-less structure can be implemented by having the first exposed portion (110E) including the first segments (110F) guide the electrical connection instead of the electrode tab. Compared to a method using a conventional electrode tab, the flat surface area formed by the first segments (110F) can implement a wider area for electrical connection, thereby increasing the energy density of the electrode assembly and reducing the resistance.

[0080] Below, the range of height differences at bending points (BP) per winding turn is described.

[0081] Fig. 7 is a schematic drawing of an electrode assembly according to one embodiment of the present invention, wherein a first segment in a specific winding turn is placed on a previous winding turn. Fig. 8 is a partial drawing showing a portion of a first electrode according to one embodiment of the present invention.

[0082] Referring to FIGS. 7 and 8 together with FIGS. 3 to 5, in the K-th winding turn of the jellyroll structure (provided that K>2) along the radial direction (dr) of the jellyroll 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 L1 K can be defined as follows. At this time, 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 thickness of the first segment (110F). Here, the t1 is the thickness of the first segment (110F). The N1 Kis the number of first segments (110F) along the circumferential direction (dc) in the Kth winding turn. The above A1 K is the width of the first segment (110F) of the K-th winding turn placed on the K-1-th winding turn. The R1 K-1 is the radius at the K-1st winding turn. In addition, K is the number of winding turns of the first electrode (100), so it is an integer exceeding 2.

[0083] Here, the circumferential direction (dc) refers to the direction surrounding the core portion (10C), i.e., the circumferential direction, when the electrode assembly (10) is viewed from above. In other words, the circumferential direction (dc) may refer to the 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.

[0084] In addition, the number of first segments (110F) along the circumferential direction (dc) in the Kth winding turn (N1) K ) means the number of first segments (110F) present in the part where the first electrode (100) is wound for the Kth time.

[0085] Meanwhile, the radius (R1) at the Kth winding turn K ) will be explained together with Figure 9.

[0086] Figure 9 is a schematic drawing showing only the first electrode in the Kth winding turn.

[0087] In Fig. 7, the first electrode (100) in the Kth winding turn K ) or the first electrode (100) in the K-1st winding turn K-1 ) is depicted as a perfect circle, but as shown in Fig. 9, the first electrode (100) in the Kth winding turn K ) may not be in the shape of a perfect circle. At this time, in the present invention, the first electrode (100) in the Kth winding turn K ) of the radius (R1)K ) is the shortest distance (R1) among the radial distances from the core part (10C) to the part where the first electrode (100) is wound for the Kth time. K.min ) and the longest distance (R1 K.max ) can be defined as the intermediate value of the first electrode (100 K ) is quite thin, so the first electrode (100) in the Kth winding turn K ) is almost similar to the shape of a circle. Therefore, the first electrode (100) in the Kth winding turn K ) of the radius (R1) K ) may be defined as above.

[0088] In this embodiment, L1 K -L1 K-1 corresponds to the height difference between the bending points (BP) of the K-1th winding turn and the Kth winding turn. At this time, (N1 K *A1 K ) / (2πR1 K-1 ) is a value for calculating the degree to which the first segments (110F) existing in the K-th winding turn overlap on the first electrode (100) of the K-1-th winding turn, i.e., the overlap ratio that the first segments (110F) of the K-th winding turn have with respect to the K-1-th winding turn. In order to calculate this overlap ratio, FIG. 7 shows the first electrode (100) of the K-th winding turn. K ) and the first electrode (100) in the K-1st winding turn K-1 ) is simply expressed by generalizing it into concentric circles. Meanwhile, D1 K is the first electrode of the Kth winding turn (100 K ) and the first electrode (100) in the K-1st winding turn K-1 ) as the interval between the radius (R1) at the Kth winding turn K ) and the radius (R1) at the K-1st winding turn K-1 ) can be calculated as the difference between them.

[0089] Also, for convenience of explanation, the first electrode of the Kth winding turn (100 K ) only three first segments (110F) among several first segments (110F) existing in the K-th winding turn are shown. The first electrode (100 K ) are bent toward the core portion (10C), and the first electrode (100) of the Kth winding turn K ) of the first segment (110F) is the first electrode (100) in the K-1 winding turn K-1 ) are overlapped on the top. In the present invention, the overlap ratio of the first segments (110F) of the K-th winding turn to the K-1-th winding turn is (N1 K *A1 K ) / (2πR1 K-1 ) was calculated as the value of . Specifically, the first electrode (100) of the Kth winding turn K ) and the first electrode (100) in the K-1st winding turn K-1 ) is assumed to be a concentric circle, the width (A1) of the first segment (110F) of the K-th winding turn placed on the K-1-th winding turn K ) and the number of first segments (110F) in the Kth winding turn (N1 K ) can be multiplied by the circumference value of the K-1th winding turn to obtain the above overlapping ratio.

[0090] By multiplying this overlapping ratio by the thickness (t1) of the first segment (110F), the laminate thickness of the first segments (110F) of the K-th winding turn with respect to the K-1-th winding turn can be calculated. In this embodiment, the height difference between the bending points (BP) of the first segments (110F) for each winding turn can be in the range of 50% or more and 300% or less of the laminate thickness thus calculated.

[0091] If, L1 K -L1 K-1 The value of t1*(N1 K *A1 K ) / (2πR1 K-1) is less than 50%, the height difference between the bending points (BP) of the first segments (110F) per winding turn is small, so when the first segments (110F) are bent, it is impossible to prevent irregular deformation from occurring in some of the first segments (110F).

[0092] Also, if L1 K -L1 K-1 The value of t1*(N1 K *A1 K ) / (2πR1 K-1 ) exceeds 300%, the height difference between the bending points (BP) of the first segment (110F) per winding turn is excessive, resulting in a large amount of unnecessary space in the height direction of the jelly roll electrode assembly (10). This is not appropriate because it reduces the capacity or energy density of the secondary battery.

[0093] Meanwhile, according to one embodiment of the present invention, the first segment (110F) may have a rectangular shape. As illustrated in FIG. 8, a portion of the first electrode current collector (110) of the first electrode (100) is exposed to form a first exposed portion (110E), and this first exposed portion (110E) may include first segments (110F) having a rectangular shape and arranged at regular intervals.

[0094] When the first segment (110F) is in the shape of a square, the above A1 K is the width of the connecting end of the first segment (110F), W1 K can be calculated as . Here, the connecting end of the first segment (110F) is the part where the first segment (110F) extends from the first exposed portion (110E). In Fig. 8, the connecting end may correspond to the lower side when the first segment (110F) is viewed as a virtual square. Since the width of the first segment (110F) in the shape of a square is constant, the width (A1) of the first segment (110F) of the K-th winding turn placed on the K-1-th winding turn K) is the width (W1) of the connecting end of the first segment (110F) K ) is the same as A1. That is, when the first segment (110F) is in the shape of a square, A1 K The value is W1 K It's okay to just take the value as is.

[0095]

[0096] Fig. 10 is a schematic drawing of an electrode assembly according to a modified embodiment of the present invention, in which a segment at a specific winding turn is placed on a previous winding turn. Fig. 11 is a partial drawing showing a portion of a first electrode according to a modified embodiment of the present invention.

[0097] Referring to FIGS. 10 and 11 together with FIGS. 3 to 5, as described above, in the K-th winding turn of the jellyroll structure (provided that K>2) along the radial direction (dr) of the jellyroll 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 L1. K can be defined as follows. Also, 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 thickness of the first segment (110F). Here, the t1 is the thickness of the first segment (110F). The N1 K is the number of first segments (110F) along the circumferential direction (dc) in the Kth winding turn. The above A1 K is the width of the first segment (110F) of the K-th winding turn placed on the K-1-th winding turn. The R1 K-1 is the radius at the K-1st winding turn. In addition, K is the number of winding turns of the first electrode (100), and is therefore an integer exceeding 2. A detailed description thereof is omitted as it overlaps with the previously explained content.

[0098] The first segment (110F) according to a modified embodiment of the present invention may have a trapezoidal shape. In particular, the first segment (110F) may have an equilateral trapezoidal shape. As illustrated 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 this first exposed portion (110E) may include trapezoidal first segments (110F) that are spaced apart from each other at a predetermined interval.

[0099] When the first segment (110F) is in the form of an equilateral trapezoid, the above A1 K is, W1 K -2*(D1 K / tanθ1) can be calculated. The above W1 K is the width of the connecting end of the first segment (110F). The connecting end of the first segment (110F) is the part where the first segment (110F) extends from the first exposed portion (110E). The above D1 K is the interval between the Kth winding turn and the K-1th winding turn. Specifically, D1 K is the first electrode of the Kth winding turn (100 K ) and the first electrode (100) in the K-1st winding turn K-1 ) as the interval between the radius (R1) at the Kth winding turn K ) and the radius (R1) at the K-1st winding turn K-1 ) can be calculated as the difference between them. In addition, the above θ1 is the interior angle of the connecting section of the first segment (110F) which is trapezoidal in shape.

[0100] The connecting end of the first segment (110F) is a portion where the first segment (110F) extends from the first exposed portion (110E), and means a relatively long side when the first segment (110F) is viewed as a virtual trapezoid. In addition, the connecting end interior angle (θ1) means the interior angle between the long side and both side sides when the first segment (110F) is viewed as a virtual trapezoid. The connecting end interior angle (θ1) is an acute angle in the trapezoidal structure. When the first segment (110F) is in the shape of a trapezoid, A1 K The value is W1 K You can't just bring the value as is, A1 K is W1 K -2*(D1 K It is desirable to calculate it as / tanθ1).

[0101]

[0102] Hereinafter, the structure of the second exposed portion (210E) of the second electrode (200) according to one embodiment of the present invention will be described in detail.

[0103] 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 the present embodiment, for each winding turn along the radial direction (dr) of the jellyroll structure, 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) K-1 , L2 K ) can gradually increase.

[0104] Since the second exposed portion (210E) has a bending point (BP) as it bends toward the core portion (10C), the thickness of the portion where the second exposed portions (210E) are laminated, i.e., the laminate thickness, increases as it goes toward the core portion (10C). Here, the direction toward the core portion (10C) corresponds to the opposite direction of the radial direction (dr).

[0105] As the number of winding turns increases, the number of second exposed portions (210E) stacked along the radial direction (dr) increases, and the second exposed portions (210E) that are excessively stacked in a limited space may be irregularly deformed. Due to such irregular deformation of the second exposed portions (210E), the separator (300) and the like may be damaged, which may cause a short circuit between the first electrode (100) and the second electrode (200).

[0106] Referring again to FIG. 6, in the case of the electrode assembly according to the present 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 jellyroll 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 a plurality of second exposed portions (210E') are bent and stacked for each winding turn, as in the present comparative example, if the height of the bending point (BP) of the second segment (210F') is constant, some of the second exposed portions (210E') may exhibit irregular deformation and be distorted. In particular, the second segment (210F') portion close to the core may not maintain a direction perpendicular to the axial direction and may bend further in the direction indicated by “I”. The second segments (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 ignition or explosion of the secondary battery.

[0107] Referring again to FIG. 5, in the case of the electrode assembly (10) according to the present embodiment, in order to prevent the problem of such short-circuit occurrence, as described above, for each winding turn along the radial direction (dr) of the jellyroll structure, 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)K-1 , L2 K ) can gradually increase. That is, the height of the bending point (BP) of the second exposed portion (210E) per winding turn in the second direction (d2) is designed to gradually decrease as it goes in the radial direction (dr). In the present embodiment, since the second exposed portions (210E) per winding turn are sequentially stacked with a height difference per winding turn, it is possible to prevent some of the second exposed portions (210E) from showing irregular deformation and being crushed. Accordingly, the occurrence of a short between the first electrode (100) and the second electrode (200) due to damage to the separator (300) can be minimized.

[0108] Meanwhile, according to the present embodiment, the second exposed portion (210E) may include a plurality of second segments (210F) that are independently bent, and the bending point (BP) of the second exposed portion (210E) described above may be a point where the second segments (210F) are bent. Specifically, the second exposed portion (210E) may not be formed in a single piece, but may have cut grooves of a predetermined depth provided at a predetermined interval. That is, the second exposed portion (210E) may be divided into second segments (210F) that are areas between these cut grooves. If the second exposed portion (210E) is formed in a single piece, when the second exposed portion (210E) is bent in the direction where the core portion (10C) is located, the second exposed portion (210E) may be irregularly wrinkled because the bending space is narrow. To prevent such problems, it is preferable to divide the second exposure portion (210E) into a plurality of second segments (210F) and then bend these second segments (210F).

[0109] Although not specifically illustrated, a flat surface area in the second direction (d2) of the electrode assembly (10) may be formed when a plurality of second segments (210F) are bent and overlapped in multiple layers. When a collector plate, which will be described later, comes into contact with the surface area of ​​the electrode assembly (10), the electrical connection of the electrode assembly (10) may be guided. That is, a tab-less structure may be implemented by having the second exposed portion (210E) including the second segments (210F) guide the electrical connection instead of the electrode tab. Compared to a method using a conventional electrode tab, the flat surface area formed by the second segments (210F) may implement a wider area for electrical connection, thereby increasing the energy density of the electrode assembly and reducing the resistance.

[0110] Below, the range of height differences at bending points (BP) per winding turn is described.

[0111] Fig. 12 is a schematic drawing of an electrode assembly according to one embodiment of the present invention, wherein a second segment in a specific winding turn is placed on a previous winding turn. Fig. 13 is a partial drawing showing a portion of a second electrode according to one embodiment of the present invention.

[0112] Referring to FIGS. 12 and 13 together with FIGS. 3 to 5, in the K-th winding turn of the jellyroll structure (provided that K>2) along the radial direction (dr) of the jellyroll 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 L2. K can be defined as follows. At this time, L2 K -L2 K-1 is, t2*(N2 K *A2 K ) / (2πR2 K-1 ) can satisfy 50% or more and 300% or less of the thickness of the second segment (210F). Here, the t2 is the thickness of the second segment (210F). The N2 Kis the number of second segments (210F) along the circumferential direction (dc) in the Kth winding turn. The above A2 K is the width of the second segment (210F) of the K-th winding turn placed on the K-1-th winding turn. The R2 K-1 is the radius at the K-1st winding turn. In addition, K is the number of winding turns of the second electrode (200), so it is an integer exceeding 2.

[0113] Here, the circumferential direction (dc) refers to the direction surrounding the core portion (10C), i.e., the circumferential direction, when the electrode assembly (10) is viewed from above. In other words, the circumferential direction (dc) may refer to the 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.

[0114] In addition, the number of second segments (210F) in the circumferential direction (dc) at the Kth winding turn (N2 K ) means the number of second segments (210F) present in the part where the second electrode (200) is wound for the Kth time.

[0115] Meanwhile, the radius (R2) at the Kth winding turn K ) is the first electrode (100) in the Kth winding turn described above. K ) of the radius (R1) K ) can be defined in the same way as in . Although not specifically shown, the radius (R2) at the Kth winding turn K ) can be defined as the median value of the shortest distance and the longest distance among the radial distances from the core part (10C) to the part where the second electrode (200) is wound for the Kth time.

[0116] In this embodiment, L2 K -L2 K-1corresponds to the height difference between the bending points (BP) of the K-1th winding turn and the Kth winding turn. At this time, (N2 K *A2 K ) / (2πR2 K-1 ) is a value for calculating the degree to which the second segments (210F) existing in the K-th winding turn overlap on the second electrode (200) of the K-1-th winding turn, i.e., the overlap ratio that the second segments (210F) of the K-th winding turn have with respect to the K-1-th winding turn. In order to calculate this overlap ratio, FIG. 12 shows the second electrode (200) of the K-th winding turn. K ) and the second electrode (200) in the K-1st winding turn K-1 ) is simply expressed by generalizing it into concentric circles. Meanwhile, D2 K is the second electrode of the Kth winding turn (200 K ) and the second electrode (200) in the K-1st winding turn K-1 ) as the interval between the radius (R2) at the Kth winding turn K ) and the radius (R2) at the K-1st winding turn K-1 ) can be calculated as the difference between them.

[0117] Also, for convenience of explanation, the second electrode (200) of the Kth winding turn K ) only three second segments (210F) among several second segments (210F) existing in the K-th winding turn are shown. The second electrode (200 K ) are bent toward the core (10C), and the second electrode (200) of the Kth winding turn K ) of the second segment (210F) is the second electrode (200) in the K-1st winding turn. K-1 ) are overlapped. In the present invention, the overlap ratio of the second segments (210F) of the K-th winding turn to the K-1-th winding turn is (N2 K *A2 K ) / (2πR2 K-1) was calculated as the value of . Specifically, the second electrode (200) of the Kth winding turn K ) and the second electrode (200) in the K-1st winding turn K-1 ) is assumed to be a concentric circle, the width (A2) of the second segment (210F) of the K-th winding turn placed on the K-1-th winding turn K ) and the number of second segments (210F) in the Kth winding turn (N2 K ) can be multiplied by the circumference value of the K-1th winding turn to obtain the above overlapping ratio.

[0118] By multiplying this overlapping ratio by the thickness (t2) of the second segment (210F), the laminate thickness of the second segments (210F) of the K-th winding turn with respect to the K-1-th winding turn can be calculated. In the present embodiment, the height difference between the bending points (BP) of the second segments (210F) for each winding turn can be in the range of 50% or more and 300% or less of the laminate thickness thus calculated.

[0119] If, L2 K -L2 K-1 The value of t2*(N2 K *A2 K ) / (2πR2 K-1 ) is less than 50%, the height difference between the bending points (BP) of the second segments (210F) per winding turn is small, so when the second segments (210F) are bent, it is impossible to prevent irregular deformation from occurring in some of the second segments (210F).

[0120] Also, if L2 K -L2 K-1 The value of t2*(N2 K *A2 K ) / (2πR2 K-1) exceeds 300%, the height difference between the bending points (BP) of the second segment (210F) per winding turn is excessive, resulting in a large amount of unnecessary space in the height direction of the jelly roll electrode assembly (10). This is not appropriate because it reduces the capacity or energy density of the secondary battery.

[0121] Meanwhile, according to one embodiment of the present invention, the second segment (210F) may have a rectangular shape. As illustrated in FIG. 13, a portion of the second electrode current collector (210) of the second electrode (200) is exposed to form a second exposed portion (210E), and this second exposed portion (210E) may include second segments (210F) having a rectangular shape and arranged at regular intervals.

[0122] When the second segment (210F) is in the shape of a square, the above A2 K is the width of the connecting end of the second segment (210F), W2 K can be calculated as . Here, the connecting end of the second segment (210F) is the part where the second segment (210F) extends from the second exposed portion (210E). In Fig. 13, the connecting end may correspond to the upper edge when the second segment (210F) is viewed as a virtual square. Since the width of the second segment (210F) in the shape of a square is constant, the width (A2) of the second segment (210F) of the K-th winding turn placed on the K-1-th winding turn K ) is the width (W2) of the connecting end of the second segment (210F) K ) is the same as A2. That is, when the second segment (210F) is in the shape of a square, A2 K The value is W2 K It's okay to just take the value as is.

[0123]

[0124] Fig. 14 is a schematic drawing of an electrode assembly according to a modified embodiment of the present invention, in which a segment at a specific winding turn is placed on a previous winding turn. Fig. 15 is a partial drawing showing a portion of a second electrode according to a modified embodiment of the present invention.

[0125] Referring to FIGS. 14 and 15 together with FIGS. 3 to 5, as described above, in the K-th winding turn of the jellyroll structure (provided that K>2) along the radial direction (dr) of the jellyroll 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 L2. K can be defined as follows. Also, L2 K -L2 K-1 is, t2*(N2 K *A2 K ) / (2πR2 K-1 ) can satisfy 50% or more and 300% or less of the thickness of the second segment (210F). Here, the t2 is the thickness of the second segment (210F). The N2 K is the number of second segments (210F) along the circumferential direction (dc) in the Kth winding turn. The above A2 K is the width of the second segment (210F) of the K-th winding turn placed on the K-1-th winding turn. The R2 K-1 is the radius at the K-1st winding turn. In addition, K is the number of winding turns of the second electrode (200), so it is an integer exceeding 2. A detailed description thereof is omitted as it overlaps with the previously explained content.

[0126] The second segment (210F) according to a modified embodiment of the present invention may have a trapezoidal shape. In particular, the second segment (210F) may have an equilateral trapezoidal shape. As illustrated in FIG. 15, a portion of the second electrode current collector (210) of the second electrode (200) is exposed to form a second exposed portion (210E), and this second exposed portion (210E) may include second trapezoidal segments (210F) spaced apart from each other at regular intervals.

[0127] When the second segment (210F) is in the form of an equilateral trapezoid, the above A2 K is, W2 K -2*(D2 K / tanθ2) can be calculated. The above W2 K is the width of the connecting end of the second segment (210F). The connecting end of the second segment (210F) is the part where the second segment (210F) extends from the second exposed portion (210E). The above D2 K is the interval between the Kth winding turn and the K-1th winding turn. Specifically, D2 K is the second electrode of the Kth winding turn (200 K ) and the second electrode (200) in the K-1st winding turn K-1 ) as the interval between the radius (R2) at the Kth winding turn K ) and the radius (R2) at the K-1st winding turn K-1 ) can be calculated as the difference between them. In addition, the above θ2 is the interior angle of the connecting section of the second segment (210F) which is trapezoidal in shape.

[0128] The connecting end of the second segment (210F) is a portion where the second segment (210F) extends from the second exposed portion (210E), and refers to a relatively long side when the second segment (210F) is viewed as a virtual trapezoid. In addition, the connecting end interior angle (θ2) refers to the interior angle between the long side and both side sides when the second segment (210F) is viewed as a virtual trapezoid. The connecting end interior angle (θ2) is an acute angle in the trapezoidal structure. When the second segment (210F) is in the shape of a trapezoid, A2 K The value is W2 K You can't just bring the value as is, A2 K is W2 K -2*(D2 K It is desirable to calculate it as / tanθ2).

[0129]

[0130] Hereinafter, a secondary battery including an electrode assembly according to one embodiment of the present invention will be described in detail.

[0131] FIG. 16 is a cross-sectional view of a secondary battery including an electrode assembly according to one embodiment of the present invention.

[0132] Referring to FIGS. 3 and 16 together, a secondary battery according to one embodiment of the present invention includes an electrode assembly (10). In FIG. 16, the secondary battery according to the present embodiment is represented as a cylindrical battery, but this is only one example of the structure of the secondary battery of the present invention, and a secondary battery according to another embodiment of the present invention may be a square battery.

[0133] A secondary battery according to the present embodiment may include a battery can (20) that houses an electrode assembly (10) and has an open top; and a cap assembly (30) 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).

[0134] The battery can (20) according to the present embodiment may be a cylindrical case with an open top, and may store an electrode assembly (10) and an electrolyte (not shown) in an internal storage space, and may include a metal material such as aluminum (Al).

[0135] A cap assembly (30) according to the present embodiment may include a top cap (31) having a plate shape and a connecting plate (32) electrically and mechanically connected to the top cap (31). The top cap (31) may include a metal material having electrical conductivity and may cover an open upper portion of a battery can (20). The top cap (31) may be electrically connected to the first segments (110F) of the first exposed portion (110E), and at the same time, may be electrically insulated from the battery can (20) by a gasket (50). Therefore, the top cap (31) according to the present embodiment may function as an external terminal of a first electrode (100) of a secondary battery.

[0136] Specifically describing the electrical connection between the top cap (31) and the first segments (110F), the secondary battery according to the present embodiment may further include a first current collector (41) positioned on the upper portion of the electrode assembly (10). The first current collector (41) may include a conductive metal material such as aluminum, copper, steel, nickel, etc., and may be electrically connected to the first segments (110F) of the electrode assembly (10). The electrical connection may be achieved through welding. A lead (60) may be connected to the first current collector (41). The lead (60) may extend upward from the electrode assembly (10) and be coupled to the connecting plate (32). In another embodiment, the lead (60) may be directly coupled to the lower surface of the top cap (31). The coupling between the lead (60) and other components may be achieved through welding. Additionally, the first collector plate (41) may be formed integrally 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 collector plate (41).

[0137] The first collector plate (41) may have a plurality of protrusions (not shown) formed radially on its lower surface. When the radial protrusions are provided, the first collector plate (41) may be pressed to press the protrusions into the bent first segments (110F). The connection between the first collector plate (41) and the first segments (110F) may be performed by, for example, laser welding. Laser welding may be performed by partially melting the base material of the first collector plate (41). In a variation, welding between the first collector plate (41) and the first segments (110F) may be performed with solder interposed. In this case, the solder may have a lower melting point compared to the first collector plate (41) and the first segments (110F). Laser welding may be replaced by resistance welding, ultrasonic welding, spot welding, etc.

[0138] Meanwhile, the secondary battery according to the present embodiment may further include a second current collector (42) positioned at the bottom of the electrode assembly (10). Specifically, the second current collector (42) may be positioned between the electrode assembly (10) and the bottom (20F) of the battery can (20). The second current collector (42) may include a conductive metal material such as aluminum, copper, steel, nickel, etc., and may be electrically connected to the second segments (210F) of the electrode assembly (10). One side of the second current collector (42) may be coupled to the second segments (210F), and the opposite side of the second current collector (42) may be coupled to the bottom (20F) of the battery can (20). Welding may be applied to the coupling of the second current collector (42). Accordingly, the battery can (20) according to the present embodiment can function as an external terminal of the second electrode (200) of the secondary battery.

[0139] Meanwhile, the secondary battery according to the present embodiment may include an insulating plate (70).

[0140] The insulating plate (70) can cover the first collector plate (41). The insulating plate (70) covers the first collector plate (41) on the upper surface of the first collector plate (41), thereby preventing the first collector plate (41) from contacting the battery can (20), particularly the beading part (20B) of the battery can (20) described later. In addition, the insulating plate (70) can be provided with a separate lead hole so that a lead (60) extending upward from the first collector plate (41) can be drawn out. The lead (60) can be drawn out 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).

[0141] The peripheral area of ​​the insulating plate (70) can be interposed between the first current collector (41) and the beading portion (20B) of the battery can (20), thereby fixing the assembly of the electrode assembly (10) and the first current collector (41). Accordingly, the assembly of the electrode assembly (10) and the first current collector (41) can be restricted from moving in the axial direction of the electrode assembly (10), thereby improving the assembly stability of the secondary battery. The insulating plate (70) can be made of an insulating polymer resin. In one example, the insulating plate (70) can include one or more materials selected from the group consisting of polyethylene, polypropylene, polyimide, and polybutylene terephthalate.

[0142] Meanwhile, the battery can (20) according to the present embodiment may include a crimping part (20C) and a beading part (20B).

[0143] 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 with the gasket (50) interposed therebetween. That is, the crimping portion (20C) can be formed in the battery can (20). More specifically, the crimping portion (20C) is formed by positioning the gasket (50) between the battery can (20) and the cap assembly (30), and then bending the upper end of the battery can (20) in the direction in which the cap assembly (30) is positioned.

[0144] The beading portion (20B) refers to a portion of the battery can (20) that is recessed toward the center in a region above the electrode assembly (10) among the side portions of the battery can (20), and is for the stable placement of the cap assembly (30) and the prevention of movement of the electrode assembly (10). That is, the cap assembly (30) according to the present embodiment and the gasket (50) surrounding it can be seated on the beading portion (20B) of the battery can (20). The above-described crimping connection can be performed in a state where the cap assembly (30) and the gasket (50) surrounding it are seated on the beading portion (20B).

[0145] The gasket (50) according to the present embodiment is positioned between the battery can (20) and the cap assembly (30), and can enhance the sealing property of the secondary battery. In addition, the gasket (50) may include an electrically insulating material, and can prevent a short circuit from occurring between the battery can (20), which functions as a terminal of the second electrode (200), and the cap assembly (30), which functions as a terminal of 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).

[0146] FIG. 17 is a drawing for explaining a method of bending a first segment of a first electrode according to one embodiment of the present invention.

[0147] Referring to FIGS. 5 and 17, in order to form a flat surface area in the first direction (d1) of the electrode assembly (10), the first segments (110F) of the first electrode (100) are bent toward the core portion as described above. However, the first segments (110F) are not bent all at once. First, the first segments (110F) can be slightly bent to have a predetermined incline. Then, after the first electrode (100) is wound, strong pressure is applied to the slightly bent first segments (110F), so that the first segments (110F) can be completely bent, as shown in FIGS. 3 and 5.

[0148] At this time, in order to slightly bend the first segments (110F) to have a predetermined incline in the first stage, as illustrated in FIG. 17, rolls (R1, R2) provided with an inclined portion (SP) may be used. Specifically, the first electrode (100) provided with the first segments (110F) may be introduced between the two rolls (R1, R2) along the d3 direction. At this time, an inclined portion (SP) having a predetermined incline may be provided at the point where the first segments (110F) are introduced among the two rolls (R1, R2), and the inclined portion (SP) may have a truncated cone shape. The introduced first segments (110F) are bent by the inclined portion (SP), and the point where the first segments (110F) are bent by the inclined portion (SP) corresponds to the bending point (BP). While the first electrode (100) is being introduced, the roll (R2) having the inclined portion (SP) can gradually move in the direction d4. That is, the roll (R2) having the inclined portion (SP) can gradually move along the direction in which the first segments (110F) protrude from the first electrode (100). In this way, as the roll (R2) having the inclined portion (SP) gradually moves, the height of the bending point (BP) of each winding turn of the first electrode (100) along the first direction (d1) can be designed to gradually increase.

[0149] Although not specifically shown, the height of the bending point (BP) per winding turn of the second segments (210F) of the second electrode (200) can also be adjusted in the same manner as in the first electrode (100).

[0150] In this example, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are only for convenience of explanation and may vary depending on the location of the target object or the location of the observer.

[0151] The secondary batteries according to the aforementioned embodiments can be assembled in multiples to form a battery module. Furthermore, one or more battery modules can 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.

[0152] The secondary battery, battery module, or battery pack described above can be applied to various devices. Specifically, it can be applied to transportation vehicles such as electric bicycles, electric vehicles, and hybrid vehicles, or ESS (Energy Storage Systems), but is not limited thereto, and can be applied to various devices capable of using secondary batteries.

[0153] 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.

[0154] Description of the symbol

[0155] 10: Electrode assembly

[0156] 100: First electrode

[0157] 110: First electrode current collector

[0158] 110E: First exposure

[0159] 110F: First segment

[0160] 120: First active material section

[0161] 200: Second electrode

[0162] 210: Second electrode current collector

[0163] 210E: Second exposure

[0164] 210F: Second segment

[0165] 220: Second active material section

[0166] 300: Membrane

Claims

1. First electrode; a second electrode; and Including 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 jellyroll 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. Among the first electrode current collectors, the first exposed portion, to which the electrode active material is not applied, extends in the first direction, Among the second electrode current collectors, the second exposed portion, to which the electrode active material is not applied, extends in a second direction opposite to the first direction, The above first exposure portion and the above second exposure portion have bending points for each winding turn, For each winding turn along the radial direction of the jellyroll structure, the length from the end of the first electrode collector in the second direction to the bending point of the first exposed portion gradually increases. The above radial direction is an electrode assembly in which the direction is from the core portion of the jelly roll structure to the outer portion.

2. In paragraph 1, The first exposure portion includes a plurality of first segments that are independently bent from each other, The bending point of the first exposed portion is an electrode assembly at which the first segment bends.

3. In paragraph 2, In the Kth winding turn of the jellyroll structure (wherein K>2) along the radial direction of the jellyroll 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 L1. K When defined as, L1 K -L1 K-1 is, t1*(N1 K *A1 K ) / (2πR1 K-1 ) satisfies 50% or more and 300% or less of the The above t1 is the thickness of the first segment, N1 above K is the number of the first segments along the circumferential direction in the Kth winding turn, A1 above K is the width of the first segment of the K-th winding turn placed on the K-1-th winding turn, R1 above K-1 The electrode assembly is the radius at the K-1th winding turn.

4. In paragraph 3, The above first segment is an electrode assembly having a square shape.

5. In paragraph 4, A1 above K is the width of the connecting section of the first segment, W1 K Electrode assembly calculated as .

6. In paragraph 3, The above first segment is an electrode assembly having a trapezoidal shape.

7. In paragraph 6, A1 above K is W1 K -2*(D1 K / tanθ1) is calculated, Above W1 K is the width of the connecting section of the first segment, Above D1 K is the interval between the Kth winding turn and the K-1th winding turn, The above θ1 is an electrode assembly which is an inner angle of a connecting section of the first segment having a trapezoidal shape.

8. In paragraph 1, An electrode assembly, wherein, for each winding turn in 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 gradually increases.

9. In paragraph 8, The second exposed portion comprises a plurality of second segments that are independently bent from each other, The bending point of the second exposed portion is an electrode assembly at which the second segment bends.

10. In Article 9, In the Kth winding turn of the jellyroll structure (wherein K>2) along the radial direction of the jellyroll 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 L2. K When defined as, L2 K -L2 K-1 is, t2*(N2 K *A2 K ) / (2πR2 K-1 ) satisfies 50% or more and 300% or less of the The above t2 is the thickness of the second segment, N2 above K is the number of the second segments along the circumferential direction in the Kth winding turn, A2 above K is the width of the second segment of the K-th winding turn placed on the K-1-th winding turn, R2 above K-1 is the radius at the K-1st winding turn, the electrode assembly 11. In Article 10, The above second segment is an electrode assembly in the shape of a square.

12. In Article 11, A2 above K is the width of the connecting section of the second segment, W2 K Electrode assembly calculated as .

13. In Article 10, The above second segment is an electrode assembly having a trapezoidal shape.

14. In paragraph 13, A2 above K is W2 K -2*(D2 K / tanθ2) is calculated, W2 above K is the width of the connecting section of the second segment, Above D2 K is the interval between the Kth winding turn and the K-1th winding turn, The above θ2 is an electrode assembly which is an internal angle of a connecting section of the second segment having a trapezoidal shape.

15. A secondary battery comprising an electrode assembly according to paragraph 1.

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