Electrode assemblies, secondary batteries, battery packs containing them, and automobiles

Abstract

The electrode assembly of the present invention is an electrode assembly in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are wound around a winding shaft to define a core and an outer circumferential surface, the positive or negative electrode comprising a sheet-shaped current collector having long and short sides and including an uncoated portion at an end of the long side, the uncoated portion including an electrode tab defined section used as an electrode tab and at least one electrode tab undefined section not used as an electrode tab, a maximum current path for the at least one electrode tab undefined section includes a widthwise current path along the short side of the current collector and a lengthwise current path along the long side of the current collector, whereby a current path ratio L2 / L1 is 11 or less, where L1 is the length of the widthwise current path and L2 is the length of the lengthwise current path, respectively.

Description

Technical Field

[0001] The present invention relates to an electrode assembly, a secondary battery, a battery pack including the same, and a vehicle, and more particularly, to a jelly-roll type electrode assembly capable of realizing low resistance, a cylindrical secondary battery including the same, a battery pack including the same, and a vehicle.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0103378 filed on August 5, 2021 and Korean Patent Application No. 10-2022-0089230 filed on July 19, 2022, and all the contents disclosed in the specifications and drawings of the applications are incorporated into this application.

Background Art

[0003] Secondary batteries that are easy to apply according to product groups and have electrical characteristics such as high energy density are not only applied to portable devices but also widely applied to electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by an electric drive source. Such secondary batteries have not only the primary advantage of significantly reducing the use of fossil fuels but also the advantage of being environmentally friendly and improving energy efficiency in that no by-products are generated during energy use, and thus are attracting attention as a new energy source.

[0004] As types of secondary batteries, cylindrical, prismatic, and pouch-type secondary batteries are known. In the case of a cylindrical secondary battery, a separator, which is an insulator, is interposed between a positive electrode and a negative electrode, and the separator is wound to form a jelly-roll type electrode assembly, which is inserted into a battery can to constitute a battery. And strip-shaped electrode tabs may be connected to non-coating portions of each of the positive electrode and the negative electrode, and the electrode tabs electrically connect the electrode assembly and an electrode terminal exposed to the outside.

[0005] Cylindrical rechargeable batteries can increase their capacity by increasing the size of the cells. In this process, the design of low-resistance cells that exhibit excellent quality in terms of energy loss and heat generation, even at high current densities, is required. Ultimately, the key to designing such low-resistance cells lies in minimizing the current path.

[0006] Figure 1 shows the positive and negative electrodes, which are applied to a conventional cylindrical secondary battery, in an expanded state.

[0007] Referring to Figure 1, a positive electrode 1 and a negative electrode 2 are shown as electrodes applied to a conventional cylindrical secondary battery. A strip-shaped positive electrode tab 1b is connected to an uncoated portion 1a formed in the middle of the longitudinal part of the positive electrode 1 so as to protrude upward along the width direction, and strip-shaped negative electrode tabs 2b are connected to uncoated portions 2a formed at both ends of the longitudinal part of the negative electrode 2 so as to protrude downward along the width direction. Figure 1(a) shows the case where there is one positive electrode tab 1b and one negative electrode tab 2b, and Figure 1(b) shows the case where there is one positive electrode tab 1b and two negative electrode tabs 2b.

[0008] Figure 2 is a schematic diagram illustrating the flow of current or electrons outside a conventional cylindrical secondary battery. Figure 3 is a schematic diagram illustrating the flow of current or electrons in the positive and negative electrodes that constitute the electrode assembly in a conventional cylindrical secondary battery.

[0009] Referring to Figures 2 and 3, the current path can be broadly divided into two paths: the path from the module busbar welding position to the electrode tabs 1b and 2b of each electrode 1 and 2 (hereinafter referred to as the "first path"), and the path from the electrode tabs 1b and 2b of each electrode 1 and 2 to the end point of the electrode.

[0010] Figure 2 shows the first path, where the current starting point (indicated by ●) is located at the positive terminal 1c and the negative terminal 2c. The positive terminal 1c is the cap of the seal that seals the open part of the battery can 3, and the negative terminal 2c is the battery can 3. An example is given where the welding position of the module busbar is located at the upper end of the cylindrical secondary battery. A current path is formed starting from the positive terminal 1c and connected to the positive tab 1b, and a current path is formed starting from the negative terminal 2c and connected to the negative tab 2b (the connection positions are indicated by ▲). Thus, the first path is determined by the appearance of the cell.

[0011] When an electrochemical oxidation reaction occurs in the active material layer of an electrode, electrons are generated while metal atoms (Li) are converted to metal cations (Li+) throughout the entire active material layer. The electrons move through the current collector (foil) that makes up the electrode to the electrode tab, and then flow out through the first pathway. In this case, the current flows in the opposite direction to the flow of electrons. On the other hand, when an electrochemical reduction reaction occurs in the electrode, electrons flow from the first pathway through the electrode tab to the current collector (foil) that makes up the electrode, move throughout the entire active material layer of the electrode, combine with cations (e.g., Li+), and the metal cations are converted back into metal. In this case, the current flows in the opposite direction to the flow of electrons.

[0012] On the other hand, when oxidation or reduction reactions occur at an electrode, the paths along which electrons move correspond to current paths. The maximum current path of an electrode is determined by the geometric structure of the current collector (foil) constituting the electrode, as well as the position and number of electrode tabs. The maximum current path of an electrode can be defined as the longest distance between the electrode point furthest from the electrode tab and the electrode tab itself. When an electrochemical oxidation-reduction reaction occurs at the electrode point furthest from the electrode tab, electrons move through multiple paths connecting that electrode point and the electrode tab, and some electrons also move through the maximum current path. As a result, as the maximum current path of an electrode lengthens, the average distance electrons travel increases in terms of the entire electrode, and the resistance of the electrode also increases.

[0013] In the following, for the sake of explanation, the maximum current path that is uniquely determined by the geometric structure of the electrode and the number and position of the electrode tabs will be referred to as the electrode's second path. Figure 3 shows the second path, which is the maximum current path of the electrode, and demonstrates that the length of the second path changes depending on the formation position and number of electrode tabs 1b and 2b.

[0014] Referring to Figure 3(a), the second path (maximum current path) of positive electrode 1 includes a widthwise current path that runs from the positive electrode terminal 1c in Figure 2 along the positive electrode tab 1b inside the cylindrical secondary battery, and a longitudinal current path that crosses the longitudinal direction of positive electrode 1 and ends at the lower right end of positive electrode 1 (the electrode point furthest from the electrode tab is indicated by a square). The second path (maximum current path) of negative electrode 2 includes a widthwise current path that starts from the negative electrode terminal 2c in Figure 2 and runs along the negative electrode tab 2b inside the cylindrical secondary battery, and a longitudinal current path that crosses the longitudinal direction of negative electrode 2 and ends at the upper left end of negative electrode 2.

[0015] Referring to Figure 3(b), the second path of positive electrode 1 is the same as in Figure 3(a). In the case of negative electrode 2, since it includes two negative electrode tabs 2b, the second path (maximum current path) of negative electrode 2 is shorter than in Figure 3(a) because the longitudinal current path is reduced by half. Thus, as the number of electrode tabs increases, the length of the second path decreases accordingly due to the reduction in the longitudinal current path.

[0016] For small cylindrical rechargeable batteries with form factors of 1865 (18mm diameter, 65mm height) and / or 2170 (21mm diameter, 70mm height) currently in use, the resistance through the second path is shown to be very large. Here, form factor refers to the value indicating the diameter and height of the cylindrical rechargeable battery. In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, and the remaining digits indicate the height of the cell.

[0017] As shown in Figure 3, in conventional cylindrical secondary batteries, the longitudinal current path is very long compared to the widthwise current path. The resistance of the battery increases as the current path lengthens. Increasing the number of negative electrode tabs 2b from (a) to (b) in Figure 3 is also done to reduce the longitudinal current path of the negative electrode and lower the resistance.

[0018] The resistance of a cylindrical secondary battery is influenced by the resistance of a first path outside the cell and the resistance of a second path inside the cell, with the resistance of the second path being the dominant factor. This is related to the length of the current (or electron) flow path due to the structure of the electrode assembly. Therefore, considering the main causes of resistance increase, a solution is needed to achieve low resistance in cylindrical secondary batteries. Lower resistance results in less heat generation in actual operating environments and is advantageous during rapid charging and high-rate discharge.

[0019] On the other hand, conventional cylindrical secondary batteries have the problem that current concentrates on the strip-shaped electrode tabs 1b and 2b that are connected to the uncoated parts 1a and 2a, resulting in high resistance, a large amount of heat generation, and poor current collection efficiency. For small cylindrical secondary batteries, resistance and heat generation are not major issues. However, when increasing the form factor to apply cylindrical secondary batteries to electric vehicles, resistance and heat generation become major problems as they can cause fires. To solve these problems, a cylindrical secondary battery (e.g., a tab-less cylindrical secondary battery) has been proposed in which the positive electrode uncoated part and the negative electrode uncoated part are located at the upper and lower ends of a jelly roll type electrode assembly, respectively, and current collection plates are welded to these uncoated parts to improve current collection efficiency.

[0020] Figures 4 to 6 illustrate the manufacturing process of a tablet cylindrical secondary battery. Figure 4 shows the structure of the electrodes, Figure 5 shows the electrode winding process, and Figure 6 shows the process of welding the current collector plate to the bent surface region of the uncoated portion.

[0021] Referring to Figures 4 to 6, the positive electrode 10 and the negative electrode 11 have a structure in which an active material 21 is coated on a sheet-like current collector 20, and include an uncoated portion 22 on one of the longer sides along the winding direction X. The longer side is in a direction parallel to the X-axis direction and refers to the side that is relatively longer in length.

[0022] Electrode assembly A is manufactured by sequentially stacking the positive electrode 10 and the negative electrode 11 together with two separation films 12, as shown in Figure 5, and then winding them in one direction (X direction). At this time, the uncoated portions of the positive electrode 10 and the negative electrode 11 are arranged in opposite directions. The entire uncoated portion 10a of the positive electrode is formed on the upper part of electrode assembly A, and the entire uncoated portion 11a of the negative electrode is formed on the lower part of electrode assembly A.

[0023] After the winding process, the uncoated portion 10a of the positive electrode 10 and the uncoated portion 11a of the negative electrode 11 are bent toward the core. Then, the current collector plates 30 and 31 are welded to the uncoated portions 10a and 11a, respectively, to join them.

[0024] The positive electrode uncoated portion 10a and the negative electrode uncoated portion 11a are not connected to any other electrode tabs, and the current collector plates 30 and 31 are connected to the external electrode terminals. As a result, the current path is formed with a large cross-sectional area along the winding axis direction of the electrode assembly A (see arrow), which has the advantage of lowering the resistance of the secondary battery. This is because resistance is inversely proportional to the cross-sectional area of ​​the path through which the current flows.

[0025] In a tablet cylindrical secondary battery, to improve the welding characteristics of the uncoated portions 10a and 11a and the current collector plates 30 and 31, it is necessary to apply strong pressure to the welding area of ​​the uncoated portions 10a and 11a and bend them to be as flat as possible. However, when bending the welding area of ​​the uncoated portions 10a and 11a, the pattern of the uncoated portions 10a and 11a may be deformed with irregular distortion. In this case, the deformed portion may come into contact with an electrode of opposite polarity, causing an internal short circuit, or it may induce fine cracks in the uncoated portions 10a and 11a. Also, when the uncoated portion 32 adjacent to the core 33 of electrode assembly A is bent, it may block all or a substantial portion of the cavity in the core of electrode assembly A. In this case, problems occur in the electrolyte injection process. That is, the cavity in the core 33 of electrode assembly A is used as a passage through which the electrolyte is injected. However, if this passage is blocked, it becomes difficult to inject the electrolyte. Furthermore, during the process of inserting the electrolyte injector into the cavity in the core 33, interference with the uncoated portion 32 near the core 33 may occur, potentially causing the uncoated portion 32 to tear.

[0026] Furthermore, the bent portions of the uncoated sections 10a and 11a to which the current collector plates 30 and 31 are welded must be superimposed in multiple layers, and no gaps (spaces) should exist. This ensures sufficient welding strength and prevents the problem of the laser penetrating into the electrode assembly A and melting the separation membrane 12 and active material 21, even when using the latest technologies such as laser welding.

[0027] Furthermore, in conventional tablet-type cylindrical secondary batteries, since the entire upper part of the electrode assembly A has an uncoated positive electrode portion 10a, when the outer peripheral surface of the upper end of the battery can is pressed inward to form the beading portion, the peripheral region 34 of the upper end of the electrode assembly A is subjected to pressure from the battery can. Such pressure can cause partial deformation of the electrode assembly A, and in this case, the separation membrane 12 may rupture, causing an internal short circuit. If a short circuit occurs inside the secondary battery, it can cause overheating and explosion.

[0028] Considering these points, the uncoated portions 10a and 11a should not be formed entirely on the upper and lower parts of electrode assembly A, and should be omitted in some sections. When the uncoated portions 10a and 11a are omitted in some sections, the resistance due to the longitudinal current path inside the electrode assembly increases, so the design of a low-resistance cell that minimizes the current path should also be considered in tablet cylindrical secondary batteries. In particular, when increasing the form factor to apply cylindrical secondary batteries to electric vehicles, a large amount of heat is generated during the rapid charging process, which may cause the cylindrical secondary battery to catch fire, making the design of a low-resistance cell that minimizes the current path even more important. [Overview of the project] [Problems that the invention aims to solve]

[0029] The present invention was conceived against the background of the prior art described above, and aims to provide an electrode assembly for a cylindrical secondary battery that minimizes the current path, particularly the longitudinal current path, to achieve low resistance, thereby enabling the cylindrical secondary battery to have high capacity and / or high output while exhibiting excellent quality in terms of the degree of heat generation due to the high current density.

[0030] Another objective of the present invention is to provide a secondary battery including an electrode assembly with an improved structure to minimize the current path, a battery pack including the same, and an automobile including the battery pack.

[0031] The technical problems that this invention aims to solve are not limited to those described above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description of the invention. [Means for solving the problem]

[0032] To achieve the above objectives, the electrode assembly according to the present invention is an electrode assembly in which a core and an outer surface are defined by winding a positive electrode, a negative electrode, and a separation film interposed between the positive electrode and the negative electrode around a winding shaft, wherein the electrode which is the positive electrode or the negative electrode is a sheet-like current collector having a long side and a short side, and includes a current collector with an uncoated portion at the end of the long side, the uncoated portion includes an electrode tab defined section used as an electrode tab and at least one electrode tab undefined section which is not used as an electrode tab, the maximum current path to the at least one electrode tab undefined section includes a current path in the width direction along the short side of the current collector and a current path in the longitudinal direction along the long side of the current collector, and when the lengths of the current path in the width direction and the length of the current path in the longitudinal direction are L1 and L2, respectively, the ratio of current paths L2 / L1 is 11 or less.

[0033] Preferably, the ratio L2 / L1 of the current paths may be 10.15 or less.

[0034] The ratio L2 / L1 of the current path may be 8.5 or less, or it may be between 2 and 5.

[0035] The undefined electrode tab section may have a lower height than the defined electrode tab section.

[0036] The maximum length of the undefined section of the electrode tab can be 4% to 23% of the lengths of the positive and negative electrodes.

[0037] The maximum length of the undefined section of the electrode tab can be 2.5 to 11 times the width of the positive electrode and the negative electrode.

[0038] According to one aspect of the present invention, the uncoated portion includes a first portion adjacent to the core, a second portion adjacent to the outer circumferential surface, and a third portion between the first and second portions, wherein the first portion may have a height smaller than the third portion in the winding axis direction.

[0039] The third portion may be defined as an electrode tab when folded along the radial direction of the electrode assembly.

[0040] The second portion may have the same height as the third portion or a smaller height in the winding axis direction.

[0041] In this way, the second and third portions can be defined as electrode tabs when bent along the radial direction of the electrode assembly.

[0042] The length of the short side of the current collector is 60 mm to 85 mm, and the length of the long side of the current collector may be 3 m to 5 m.

[0043] Here, the maximum length along the long side of the current collector in the first portion may be 4% to 23% of the length of the long side of the current collector.

[0044] In the first portion, the length along the long side of the current collector may be 660 mm or less.

[0045] The first portion may correspond to the undefined interval of the electrode tab.

[0046] The first portion does not need to be bent along the radial direction of the electrode assembly.

[0047] The second portion does not need to be bent along the radial direction of the electrode assembly.

[0048] In the winding direction of the electrode assembly, the length of the third portion may be longer than the lengths of the first portion and the second portion.

[0049] The first portion may begin from the short side of the core of the current collector, the height of the first portion may be constant along the winding direction, and the first portion may not be bent along the radial direction of the electrode assembly.

[0050] According to another aspect of the present invention, at least a portion of the third portion may be divided into a plurality of independently foldable segmented pieces.

[0051] The segmented pieces are folded and overlapped in the direction of the winding axis.

[0052] Preferably, the length of the short side of the current collector is 60 mm to 85 mm, the length of the long side of the current collector is 3 m to 5 m, the thickness of the current collector is 5 μm to 25 μm, the width of the segmented piece is 10 mm or less, and the height of the segmented piece is 10 mm or less.

[0053] Here, in the first part, the length along the long side of the current collector is 660 mm or less.

[0054] The electrode assembly includes, sequentially along the radial direction with respect to the cross-section in the winding axis direction, segments without segmental segments and segments with uniform height. The plurality of segmental segments are arranged in the uniform height segments and are bent along the radial direction of the electrode assembly to form a bent surface region.

[0055] In another example, the electrode assembly further includes a height-variable section between the segment-omitted section and the height-uniform section in which the height of the segment pieces is variable, and the plurality of segment pieces may be arranged in the height-variable section and the height-uniform section and be bent along the radial direction of the electrode assembly to form a bent surface region.

[0056] The aforementioned segment omission interval may correspond to the electrode tab undefined interval.

[0057] The second portion is not divided into segmented pieces, and the height of the first portion and the height of the second portion may be the same.

[0058] The third portion may include one or more segments omitted along the winding direction of the electrode assembly where no segments are present.

[0059] Here, the height of the uncoated portion in the segmented section may be the same as the height of the first portion.

[0060] The segmented pieces may be located in two or more sectoral or polygonal regions arranged circumferentially with respect to the core.

[0061] The aforementioned segment omission interval may correspond to the electrode tab undefined interval.

[0062] The core is provided with a cavity, the third portion is defined as an electrode tab when bent along the radial direction of the electrode assembly, and the third portion may be divided into a plurality of independently bendable segmental pieces, the bent segmental pieces not obstructing the cavity.

[0063] In such a case, the maximum length along the long side of the current collector in the first part may be 4% to 23% of the length of the long side of the current collector.

[0064] A secondary battery according to the present invention for achieving the other problems described above includes: an electrode assembly according to the present invention; a cylindrical battery housing that houses the electrode assembly through an open portion formed on one side and is connected to an uncoated portion of a negative electrode; a sealing body that seals the open portion of the cylindrical battery housing so as to be insulated from the cylindrical battery housing; and a positive electrode terminal that is riveted through a through hole formed in the bottom of the cylindrical battery housing located on the opposite side of the open portion of the cylindrical battery housing and is connected to an uncoated portion of a positive electrode.

[0065] Preferably, the secondary battery of the present invention further includes a positive electrode current collector plate electrically connected to the uncoated portion of the positive electrode and a negative electrode current collector plate electrically connected to the uncoated portion of the negative electrode, wherein the uncoated portion of the positive electrode is exposed to the outside of the separator membrane, the uncoated portion of the negative electrode is exposed to the outside of the separator membrane in the opposite direction to the uncoated portion of the positive electrode.

[0066] The DC resistance of the aforementioned secondary battery may be 4 mΩ or less, and the AC resistance may be 3 mΩ or less.

[0067] Preferably, the AC resistance of the secondary battery may be 2 mΩ or less.

[0068] The secondary battery may have a diameter-to-height ratio greater than 0.4.

[0069] The sealing body may include a non-polar cap plate and a sealing gasket interposed between the peripheral edge of the cap plate and the open portion of the cylindrical battery housing.

[0070] The positive electrode terminal may include a main body inserted into the through hole, an external flange portion extending along the outer surface from one peripheral edge of the main body exposed on the outer surface of the bottom of the cylindrical battery housing, an internal flange portion extending toward the inner surface from the other peripheral edge of the main body exposed on the inner surface of the bottom of the cylindrical battery housing, and a flat portion provided inside the internal flange portion.

[0071] The secondary battery further includes a positive electrode current collector plate electrically connected to the uncoated portion of the positive electrode and a negative electrode current collector plate electrically connected to the uncoated portion of the negative electrode, wherein the positive electrode terminal can be joined to the positive electrode current collector plate by laser welding in the flat portion.

[0072] An undefined electrode tab section may be a portion where no current path is formed because it is not connected to the negative electrode current collector plate and the positive electrode current collector plate.

[0073] Another problem of the present invention can be solved by a battery pack including a plurality of the above-described secondary batteries.

[0074] Preferably, the rechargeable batteries are arranged in a predetermined number of rows, with the positive terminals of each rechargeable battery and the outer surface of the bottom of the battery housing facing upwards.

[0075] Another problem of the present invention can also be solved by an automobile including at least one of the above-mentioned battery packs. [Effects of the Invention]

[0076] One aspect of the present invention is to provide an upper limit for the ratio of current paths L2 / L1 in the maximum current path. The range of such a current path ratio L2 / L1 is the range in which the electrode assembly can have high capacity while minimizing internal resistance. Therefore, a secondary battery containing such an electrode assembly will have high capacity and / or high output, while exhibiting excellent quality in terms of the degree of heat generation due to the high current density.

[0077] According to another aspect of the present invention, the internal resistance of the secondary battery can be reduced and the energy density increased by using the uncoated portions protruding upward and downward from the electrode assembly as electrode tabs.

[0078] In another aspect of the present invention, the structure of the uncoated portion of the electrode assembly can be improved to prevent the uncoated portion from tearing when it is bent, and the number of overlapping layers of the uncoated portion can be sufficiently increased to improve the welding strength of the current collector plate.

[0079] According to another aspect of the present invention, by applying a segmented segment structure to the uncoated portion of the electrode and optimizing the dimensions (width, height, and spacing pitch) of the segmented segments, the physical properties of the area where the current collector plate is welded can be improved by sufficiently increasing the number of stacked segmented segments in the area used as the welding target area.

[0080] According to yet another aspect of the present invention, an electrode assembly is provided in which energy density is improved and resistance is reduced by applying a structure in which a current collector plate is welded over a wide area to a bent surface region formed by bending a segmented piece.

[0081] In another aspect of the present invention, a cylindrical secondary battery can be provided with an improved design that allows for electrical wiring to be performed at the top.

[0082] In another aspect of the present invention, by improving the positive electrode terminal structure of a cylindrical secondary battery and increasing the cross-sectional area of ​​the current path, the problem of internal heat generation that occurs during rapid charging can be improved.

[0083] According to yet another aspect of the present invention, by improving the structure of the uncoated portion adjacent to the core of the electrode assembly, it is possible to prevent the cavity in the core of the electrode assembly from becoming blocked when the uncoated portion is bent, thereby facilitating the electrolyte injection process and the welding process between the battery housing (or positive electrode terminal) and the current collector plate.

[0084] According to another aspect of the present invention, it is possible to provide a cylindrical secondary battery having a structure that has low internal resistance, prevents internal short circuits, and improves the welding strength between the current collector plate and the uncoated portion, a battery pack including the same, and an automobile.

[0085] In particular, the present invention can provide a cylindrical secondary battery having a DC resistance of 4 mΩ or less, an AC resistance of 3 mΩ or less, and a diameter-to-height ratio of 0.4 or more, as well as a battery pack and an automobile containing the same.

[0086] In addition, the present invention provides various other effects, which will be explained in each embodiment. Effects that can be easily inferred by an ordinary engineer will not be explained.

[0087] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention. Therefore, the invention should not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0088] [Figure 1] This diagram shows the positive and negative electrodes, which are applied to a conventional cylindrical secondary battery, in an expanded state. [Figure 2]This diagram schematically shows the flow of current or electrons outside a conventional cylindrical rechargeable battery. [Figure 3] This diagram schematically shows the flow of current or electrons in the positive and negative electrodes that constitute the electrode assembly in a conventional cylindrical secondary battery. [Figure 4] This is a plan view showing the structure of electrodes used in the manufacture of conventional tablet-type cylindrical secondary batteries. [Figure 5] This diagram shows the electrode winding process for a conventional tablet-type cylindrical secondary battery. [Figure 6] This shows the process of welding the current collector plate to the insulated surface of the uncoated portion in a conventional tablet cylindrical secondary battery. [Figure 7] This is a diagram illustrating an electrode assembly according to one embodiment of the present invention. [Figure 8] Figure 7 is a diagram intended to explain the background behind setting the ratio of the current path to the maximum current path in the electrodes included in the electrode assembly within a certain range, and schematically shows the flow of current or electrons in the positive and negative electrodes that constitute a hypothetical electrode assembly. [Figure 9] This is a plan view showing the electrode structure of the first embodiment included in the electrode assembly shown in Figure 7. [Figure 10] This is a schematic diagram of the electrodes, including the undefined interval of the electrode tabs used in the simulation. [Figure 11] This is a resistance graph based on the number of welding points, as confirmed by simulation. [Figure 12] This is a plan view showing the electrode structure of a second embodiment included in an electrode assembly according to another embodiment of the present invention. [Figure 13] This is a plan view showing the electrode structure of a third embodiment included in an electrode assembly according to another embodiment of the present invention. [Figure 14] This is a plan view showing the electrode structure of a fourth embodiment included in an electrode assembly according to another embodiment of the present invention. [Figure 15] This is a plan view showing the electrode structure of a fifth embodiment included in an electrode assembly according to another embodiment of the present invention. [Figure 16]This figure shows the definitions of the width, height, and spacing pitch of the segmented pieces according to an embodiment of the present invention. [Figure 17] This is a plan view showing the deformed structure of an electrode according to the fifth embodiment of the present invention. [Figure 18] This is a top view showing independent regions where multiple segmented pieces may be located when an electrode according to a modified version of the present invention is wound onto an electrode assembly. [Figure 19] This is a plan view showing the structure of an electrode according to the sixth embodiment of the present invention. [Figure 20] This figure shows the definitions of the width, height, and separation pitch of the segmented pieces included in the electrode according to the sixth embodiment of the present invention. [Figure 21] This is a schematic top perspective view showing an electrode assembly with a bent surface region formed thereon. [Figure 22] This is a cross-sectional view of a jelly roll type electrode assembly, in which one of the electrodes from the 5th and 6th embodiments (and their variations) is applied as the positive and negative electrodes, cut along the Y-axis direction (winding axis direction). [Figure 23] This is a plan view showing the deformed structure of an electrode according to the fifth embodiment of the present invention. [Figure 24] This is a cross-sectional view of a cylindrical secondary battery according to one embodiment of the present invention. [Figure 25] This figure schematically shows the configuration of a battery pack according to an embodiment of the present invention. [Figure 26] Figure 25 is a diagram illustrating an automobile that includes a battery pack. [Modes for carrying out the invention]

[0089] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner appropriate to the technical idea of ​​the present invention, in accordance with the principle that the inventor himself may appropriately define the concepts of terms in order to best describe the invention. Accordingly, it should be understood that the embodiments and configurations shown in the drawings described herein are merely the most preferred embodiments of the present invention and do not represent the entirety of the technical idea of ​​the present invention, and that there may be a variety of equivalents and modifications that can be substituted therein at the time of this application.

[0090] For the purpose of aiding understanding the invention, the accompanying drawings may be exaggerated in some parts and not shown to actual scale. Furthermore, the same reference numeral may be assigned to the same component in different embodiments.

[0091] For two comparison subjects to be "identical" means they are "substantially identical." Therefore, "substantially identical" may include deviations that are considered low in this industry, for example, deviations of 5% or less. Furthermore, uniformity of any parameter within a given domain may mean uniformity from an average perspective.

[0092] Throughout the specification, unless otherwise specified, each component may be singular or plural.

[0093] The placement of any configuration "above (or below)" a component or "above (or below)" a component may mean not only that any configuration is directly placed on the top (or bottom) surface of the component, but also that other configurations may be interposed between the component and any configuration placed above (or below) it.

[0094] Furthermore, when it is stated that one component is “connected,” “joined,” or “connected” to another component, it should be understood that while such components may be directly connected or connected to one another, other components may also be “interposed” between them, or each component may be “connected,” “joined,” or “connected” by other components. Also, “connection” may include electrical or physical connection.

[0095] For the sake of explanation, in this specification, the direction along the longitudinal direction of the winding shaft of an electrode assembly wound in a jelly roll form is referred to as the winding axis direction (Y axis direction). The direction surrounding the winding shaft is referred to as the circumferential direction or rotational direction (X axis direction). The direction approaching or moving away from the winding shaft is referred to as the radial direction.

[0096] One of the features of the present invention is to set the maximum current path in the positive and / or negative electrodes constituting the jelly roll type electrode assembly in order to minimize resistance in a cylindrical secondary battery. In particular, in the maximum current path of the present invention, an upper limit is presented for the ratio of the current path L2 / L1, where L1 is the length of the current path in the width direction along the short side of the current collector and L2 is the length of the current path in the longitudinal direction along the long side of the current collector. The range in which such a ratio of the current path exists is a range in which the internal resistance can be minimized while the electrode assembly has high capacity, and if the upper limit of the ratio of the current path L2 / L1 is exceeded, the requirements for the minimum resistance of the secondary battery (for example, DC resistance of 4 mΩ or less and AC resistance of 3 mΩ or less) cannot be met.

[0097] First, the electrode assembly of the present invention will be described. Figure 7 is a diagram illustrating an electrode assembly according to one embodiment of the present invention.

[0098] Referring to Figure 7, the electrode assembly 100 includes a positive electrode 40, a negative electrode 50, and a separation membrane 60 interposed between them. The electrode assembly 100 may be a jelly roll type electrode assembly having a structure in which the positive electrode 40, the negative electrode 50, and the separation membrane 60 are wound in one direction. Such an electrode assembly 100 can be manufactured by winding a laminate formed by stacking the positive electrode 40, the separation membrane 60, the negative electrode 50, and the separation membrane 60 at least once, in one direction (the X-axis direction in the drawing) around a winding axis B. The innermost part of the electrode assembly 100 is defined as the core, and the outermost part as the outer circumferential surface. The X-axis direction is the winding direction.

[0099] The core may be provided with a cavity. The diameter of the cavity may be, for example, 2 mm or more and 8 mm or less. The cavity may be the area where the core that will become the winding shaft has been removed. The smaller the diameter of the cavity, the more advantageous it is for utilizing the internal space of the battery housing including the electrode assembly 100. However, since the electrode assembly 100 cannot be manufactured without using the core, the diameter of the cavity cannot be set to 0. Also, since the cavity serves as a passage for the movement of the electrolyte when the electrolyte is injected, it must be of a certain size or larger in order to smoothly achieve electrolyte impregnation. For this reason, at an acceptable level of winding process, it is desirable that the diameter of the cavity be at least 2 mm or more, and if the diameter of the cavity exceeds 8 mm, the utilization of the internal space becomes inefficient, which is undesirable from the viewpoint of energy density.

[0100] The positive electrode 40 has a structure in which a positive electrode active material layer 40b is coated on one or both sides of a sheet-like positive electrode current collector having a long side and a short side, and includes a positive electrode uncoated portion 40a at the end of one long side along the winding direction where the active material is not coated. Here, the long side means the side that is parallel to the X-axis direction and is relatively longer in length. The X-axis direction can be called the longitudinal direction. The short side means the side that is parallel to the Y-axis direction in the drawing and is shorter in length than the long side. The Y-axis direction can be called the width direction.

[0101] The uncoated positive electrode portion 40a is defined as an electrode tab, distinguishing it from the conventional technology in which a strip-shaped electrode tab is attached separately. Here, being defined as an electrode tab means that, during the manufacturing of the secondary battery, it becomes a part that connects with the current collector plate to form a current path. Furthermore, only a portion of the uncoated positive electrode portion 40a is defined as an electrode tab. This means that a portion of the uncoated positive electrode portion 40a is not used as an electrode tab. The portion not used as an electrode tab may be a part that is not connected to the current collector plate and cannot form a current path, either because its height in the winding axis direction (Y axis direction) is smaller than other parts of the uncoated positive electrode portion 40a, or because it is omitted in some sections. Thus, it is further distinguished from the conventional technology in that only a portion of the uncoated positive electrode portion 40a is defined as an electrode tab. In this way, the uncoated positive electrode portion 40a may include an electrode tab defined section that is used as an electrode tab, and at least one or more electrode tab undefined sections that are not used as an electrode tab.

[0102] The negative electrode 50 also has a structure in which a negative electrode active material layer 50b is coated on one or both sides of a sheet-like negative electrode current collector having a long side and a short side, and includes a negative electrode uncoated portion 50a at the end of one long side along the winding direction where the active material is not coated. The negative electrode uncoated portion 50a is also defined as an electrode tab. Furthermore, only a part of the negative electrode uncoated portion 50a is defined as an electrode tab. Thus, the negative electrode uncoated portion 50a may also include an electrode tab defined section used as an electrode tab and at least one electrode tab undefined section that is not used as an electrode tab.

[0103] The uncoated positive electrode portion 40a and the uncoated negative electrode portion 50a are arranged in opposite directions, and the electrode assembly 100 after winding is approximately cylindrical in shape. The uncoated positive electrode portion 40a is located at the upper end of the electrode assembly 100, and the uncoated negative electrode portion 50a is located at the lower end of the electrode assembly 100. In such an electrode assembly 100, a portion of the uncoated positive electrode portion 40a protruding upward and a portion of the uncoated negative electrode portion 50a protruding downward are used as electrode tabs, and by welding and connecting the respective current collector plates to these tabs, a tabless cylindrical secondary battery with improved current collection efficiency can be manufactured. By using the uncoated portions 40a and 50a protruding upward and downward of the electrode assembly 100 as electrode tabs, the internal resistance of the secondary battery can be reduced and the energy density can be increased.

[0104] An electrode assembly 100 according to one embodiment of the present invention is further distinguished from the prior art in that, in the positive electrode 40 or negative electrode 50 included in the electrode assembly 100, the ratio L2 / L1 ("current path ratio") of the length of the longitudinal current path along the long side of the current collector constituting the second path of the electrode to the length L1 of the widthwise current path along the short side of the current collector constituting the second path of the electrode (maximum current path) is 11 or less.

[0105] The short and long sides of the electrode current collector correspond to the width and length of the electrodes, respectively. As a result, in the maximum current path of the positive electrode 40 or negative electrode 50, the ratio L2 / L1 (length of the longitudinal current path to the length of the widthwise current path L1) is 11 or less.

[0106] In this invention, the background for setting the ratio of current paths in the maximum current path within the electrodes included in the electrode assembly to a certain range as described above will be explained with reference to Figure 8. Figure 8 schematically shows the flow of current or electrons in the positive and negative electrodes constituting a virtual electrode assembly (the connection point between the first and second paths is indicated by ▲, and the end points of the electrodes are indicated by ■).

[0107] The positive electrode 10' and negative electrode 11' shown in Figure 8 have a structure in which, for example, in the prior art described with reference to Figures 4 to 6, a plurality of positive electrode tabs 10c and a plurality of negative electrode tabs 11c are formed by notching the uncoated portion 10a of the positive electrode 10 and the uncoated portion 11a of the negative electrode 11 in the width direction.

[0108] If the electrode assembly including the positive electrode 10' and negative electrode 11' shown in Figure 8 is manufactured into a cylindrical secondary battery, and the module busbar welding position is the same as that of the secondary battery described with reference to Figure 2, then the first path leading to the electrode tabs 10c and 11c of each electrode 10' and 11' should also be the same as that of the secondary battery described with reference to Figure 2. However, the second path (maximum current path) of electrodes 10' and 11' shows a clear difference from that in Figure 3, as shown in Figure 8.

[0109] In Figure 8, the current path length in the width direction of both the positive electrode 10' and the negative electrode 11' is short to the width direction length level, and the longitudinal movement due to the nearly continuous uncoated portions 10a and 11a is shorter than that of the conventional second path shown in Figure 3. In particular, when the positive electrode tab 10c of the positive electrode 10' and the negative electrode tab 11c of the negative electrode 11' are positioned correspondingly to each other at the top and bottom of the electrode assembly, the longitudinal movement is almost nonexistent or very short, as illustrated. As a result, the maximum current path of electrodes 10' and 11' becomes substantially the same as the current path in the width direction of the electrodes.

[0110] In other words, if the positive electrode 10' and the negative electrode 11' have the electrode structure shown in Figure 8, the length of the current path in the width direction of the maximum current path is effectively as short as the distance in the width direction of the electrode, and the current movement path in the longitudinal direction of the electrode is very short. As a result, the ratio of current paths approaches zero.

[0111] However, the length of the longitudinal current path in the maximum current path of the electrode can vary depending on the structure of the electrode tab (uncoated region), as explained with reference to Figure 3. Figure 8 shows a structure in which electrode tabs 10c and 11c are formed almost continuously along the longitudinal direction of electrodes 10' and 11', but preferably, there may be regions where the electrode tabs have been removed.

[0112] For example, an electrode assembly according to an embodiment of the present invention may have a form in which the uncoated portion is bent toward the core. In this case, in order to prevent the bent uncoated portion from obstructing the cavity in the core, the uncoated portion close to the core may not be bent, or its height in the winding direction may be reduced, or a corresponding portion may be removed to create an electrode tab undefined section as described above. The electrode tab undefined section may be formed near the core side of the electrode assembly after the electrode has been wound. Furthermore, the electrode tab undefined section may be provided at multiple locations between one end and the other end in the longitudinal direction, relative to the state before the electrode has been wound. Also, the length of the electrode tab defined section in the winding direction may be set in various ways depending on the position and length of the electrode tab undefined section. If the electrode includes multiple electrode tab undefined sections, the maximum current path of the electrode may be defined in the electrode tab undefined section having the longest length in the winding direction. In the electrode tab undefined section, electrons should move toward the electrode tab defined section, so the maximum current path is defined in the longest electrode tab undefined section. Therefore, as the length of the undefined electrode tab section in the winding direction increases, the proportion of the current path will inevitably become longer than that shown in Figure 8. Furthermore, the proportion of the current path can vary depending on the position of the defined electrode tab section.

[0113] The maximum current path changes depending on how the position of the electrode tab definition section is set, and the smaller the maximum current path, the lower the electrode resistance. However, when designing the electrode assembly, it becomes necessary to include an undefined electrode tab section in some sections of the uncoated part, which is a factor that increases resistance. For this reason, in the present invention, the upper limit of the ratio of the current path in the maximum current path to the undefined electrode tab section L2 / L1 is limited to satisfy the low resistance condition. That is, the range of the current path ratio L2 / L1 can be limited so that the resistance of the secondary battery does not increase beyond a predetermined range.

[0114] Thus, the present invention is characterized by including an undefined electrode tab section in at least a portion of the uncoated area, and limiting the upper limit of the ratio L2 / L1 of the current path in the maximum current path to the undefined electrode tab section to a predetermined range. In other words, the present invention provides guidance on how long the undefined electrode tab section can be set while minimizing the increase in resistance of the secondary battery.

[0115] Figure 9 is a plan view showing the electrode structure of the first embodiment included in the electrode assembly of Figure 7.

[0116] Referring to Figure 9, the electrode 140, which is the positive electrode 40 or negative electrode 50 shown in Figure 7, includes an electrode current collector 141 made of metal foil and an active material layer 142. The metal foil may be a conductive metal, such as aluminum or copper, and is appropriately selected depending on the polarity of the electrode 140. The thickness of the positive electrode current collector (foil) may be 10 μm to 20 μm, and the thickness of the negative electrode current collector (foil) may be 5 μm to 15 μm.

[0117] The length of the short side of the current collector 141 is 60 mm to 85 mm, and the length of the long side of the current collector 141 may be 3 m to 5 m. In this case, the ratio of the short side to the long side of the current collector 141 may be 1.2% to 2.8%, which is significantly smaller than the 6% to 11% level in cylindrical secondary batteries with the 1865 or 2170 form factor. That is, the current collector 141 is very long in the longitudinal direction and has a very large number of turns when wound. The number of turns can be counted relative to the core-side end of the electrode assembly 100.

[0118] An active material layer 142 is formed on at least one surface of the current collector 141. The active material layer 142 is formed along the winding direction (X-axis direction). The electrode 140 includes an uncoated portion 143 at the long side end in the winding direction. The uncoated portion 143 is a part of the current collector 141 where the active material is not coated. A portion of the uncoated portion 143 in the winding direction is set as an electrode tab undefined section, and the remainder is set as an electrode tab defined section.

[0119] The electrode 140 is manufactured by forming an active material layer 142 on a current collector 141 and then crimping it. Preferably, an insulating coating layer 144 can be formed at the boundary between the active material layer 142 and the uncoated portion 143. The insulating coating layer 144 is formed so that at least a portion of it overlaps with the boundary between the active material layer 142 and the uncoated portion 143. The insulating coating layer 144 prevents short circuits between two electrodes 140 with different polarities that are facing each other across a separation membrane (see 60 in Figure 7), namely the positive electrode 40 and the negative electrode 50. The insulating coating layer 144 can cover the boundary portion between the active material layer 142 and the uncoated portion 143 with a width of 0.3 mm to 5 mm. The width of the insulating coating layer 144 can be varied along the winding direction of the electrode 140. The insulating coating layer 144 contains a polymer resin and may contain an inorganic filler such as Al2O3. The portion of the current collector 141 covered by the insulating coating layer 144 is not a region coated with the active material layer, and therefore can be considered an uncoated portion.

[0120] The uncoated portion 143 includes a first portion B1 (uncoated portion on the core side) adjacent to the core of the electrode assembly 100, a second portion B3 (uncoated portion on the outer periphery side) adjacent to the outer periphery surface of the electrode assembly 100, and a third portion B2 (intermediate uncoated portion) between the first portion B1 and the second portion B3.

[0121] The B1 / B2 boundary can be appropriately defined at points where the height (or variation pattern) of the uncoated portion substantially changes as you move from the core side to the outer edge of the electrode assembly, or at predetermined percentage points relative to the radius of the electrode assembly (e.g., 5%, 10%, 15% of the radius). The B2 / B3 boundary can also be defined at points where the height (or variation pattern) of the uncoated portion substantially changes as you move from the outer edge to the core of the electrode assembly, or at predetermined percentage points relative to the radius of the electrode assembly (e.g., 85%, 90%, 95% of the radius). Once the B1 / B2 and B2 / B3 boundaries are identified, the third portion B2 can be automatically identified.

[0122] This does not rule out the possibility of other structures intervening between the first part B1 and the third part B2. Nor does it rule out the possibility of other structures intervening between the third part B2 and the second part B3.

[0123] In this embodiment, the height of the uncoated portion 143 is not constant, and there is a relative difference in the winding direction. That is, the first portion B1 has a shorter height in the winding axis direction than the third portion B2. After forming the uncoated portion 143 so that the height is constant, the uncoated portion of the first portion B1 can be further cut to create a height difference compared to the uncoated portion of the third portion B2. Here, the height of each portion may be the average height or the maximum height, and the same applies hereafter.

[0124] The heights of the first part B1 and the second part B3 in the winding axis direction are 0 or greater, and the heights of the first part B1 and the second part B3 may be the same or different. In this embodiment, the case in which the heights of the first part B1 and the second part B3 are different, and the height of the second part B3 is the same as the height of the third part B2 is given as an example.

[0125] In this embodiment, the first part B1 is an undefined electrode tab section, and the third part B2 is an electrode tab defined section. The second part B3 may also be set as an electrode tab defined section. The third part B2 may be defined as an electrode tab when bent along the radial direction of the electrode assembly 100. Similarly, the second part B3 may also be defined as an electrode tab when bent along the radial direction. Since the first part B1 is not bent along the radial direction and does not electrically contact the current collector plate described later, when an oxidation-reduction reaction occurs in the first part B1, the current (electrons) flows by bypassing it through the adjacent third part B2.

[0126] In an electrode 140 with such a structure, the second portion B3 can be bent to become a welding area. In the winding direction, the length d of the third portion B2 B2 The length of the first part B1 is d B1 It may be longer than this. Length d of the third part B2 B2 The length of the second part B3 is d B3 It may be longer than this. Length d of the third part B2B2 By increasing the length, when folding, the folding parts can be overlapped multiple times. The length d of the third part B2 B2 By increasing the length, a sufficient welding area can be ensured.

[0127] Preferably, the first part B1 which is an electrode tab undefined section is close to the core side. After the first part B1 is wound up first, the third part B2 is wound up. Since the third part B2 is located on the side farther from the core than the first part B1, when the third part B2 is folded, the third part B2 does not deform.

[0128] Since the height of the first part B1 is small and it cannot be folded, the cavity of the core of the electrode assembly 100 is not blocked. If the cavity of the core is not blocked, the electrolyte injection process becomes easy and the electrolyte injection efficiency is improved. Also, the welding process between the current collector plate on the negative electrode (or positive electrode) side and the battery housing (or electrode terminal) can be easily performed by inserting a welding jig from the core.

[0129] After forming the non - coating part 143 with a constant height, the non - coating part of the first part B1 is cut more than the non - coating part of the third part B2 to have a height difference, whereby the first part B1 is not used as an electrode tab. When the electrode tab undefined section is included in the non - coating part 143 like this, the resistance increases as the maximum current path increases compared to the case where the entire non - coating part is designed as an electrode tab defined section.

[0130] Preferably, the first part B1 is required so that the electrode tab defined section is folded and does not block the cavity of the core. The length d of the first part B1 B1 Even if it becomes longer, the length d of the third part B2 B2 and the length d of the second part B3 B3 are relatively long, or if the welding area ensured by the third part B2 is sufficient, the resistance of the whole cell (AC resistance and DC resistance) may not change much, but the resistance in the first part B1 will increase. Therefore, considering the increase in the resistance in the first part B1, the length d of the first part B1 B1It is necessary to limit it.

[0131] In the ratio of the current path to the maximum current path L2 / L1, the denominator is constant as the width of the electrode. This gives the length d of the first part B1. B1 This is the factor that determines the ratio L2 / L1 of the current path to the maximum current path. In this invention, the length d of the first part B1 B1 By adjusting the ratio of the current path to the maximum current path L2 / L1 to 11 or less, the increase in resistance is minimized while preventing the core cavity from being blocked. Preferably, the ratio of the current path to the maximum current path L2 / L1 may be 10.15 or less. More preferably, the ratio of the current path to the maximum current path L2 / L1 may be 8.5 or less. More preferably, the ratio of the current path to the maximum current path L2 / L1 may be 2 to 5. Each value is determined by the electrical, physical, and chemical properties of the current collector 141 and the active material layer 142, the resistance conditions of the secondary battery, and the length d of the first part B1 required not to obstruct the core cavity. B1 The length d of the second part B3 is necessary to have an appropriate number of overlaps and to ensure an effective welding area. B3 , and the length d of the third part B2 B2 This value may be optimized to have a critical effect, taking these factors into consideration. Thus, in this invention, the ratio L2 / L1 of the current path to the maximum current path is limited to a predetermined range, while the number and length of the undefined electrode tab sections are adjusted, and the remainder is designed as an electrode tab defined section.

[0132] Figure 9 shows the maximum current path according to one embodiment (the connection point between the first and second paths is indicated by ▲, and the end points of the electrodes are indicated by ■). The maximum current path is included in the first section B1, which is an undefined section of the electrode tab. The maximum current path is the path in the first section B1 where the length of the path through which the current (electrons) flows is maximized when an electrochemical redox reaction occurs.

[0133] The length L1 of the current path in the width direction of the maximum current path is short, at the level of the length of the short side of the current collector 141 and the electrode 140. Specifically, the length L1 of the current path in the width direction is the minimum length from one end of the long side of the uncoated portion 143 to the other end of the long side of the current collector 141. Since the heights of the second portion B3 and the third portion B2 are the same, the length of the current path in the width direction of the electrode 140 is the same as the length (width) of the short side of the electrode 140, and since the uncoated portion of the second portion B3 is not cut, it is also the same as the length of the short side of the current collector 141.

[0134] In this embodiment, the ratio of the current path to the maximum current path is L2 / L1, and since L1 corresponds to the width of electrode 140, the ratio of the current path is the length d of the first part B1. B1 It can be adjusted using [this method].

[0135] The upper limit of the current path ratio L2 / L1 may be a value such that the DC resistance of the secondary battery including the electrode assembly 100 is 4 mΩ or less and the AC resistance is 3 mΩ or less. More preferably, the upper limit of the current path ratio L2 / L1 may be a value such that the AC resistance of the secondary battery including the electrode assembly 100 is 2 mΩ or less.

[0136] The resistance of a secondary battery varies depending on the electrical, physical, and chemical properties of the current collector 141 and the active material layer 142. For example, when the length of the short side of the current collector 141 is 60 mm to 85 mm, the length of the long side of the current collector 141 is 3 m to 5 m, and the thickness of the current collector 141 is 5 μm to 20 μm, the length d of the first part B1 B1 It may be 660 mm or less. In such a case, the length d of the first part B1 B1 The maximum value is 660 mm, and considering the length of the longer side of the current collector 141, the length d of the first part B1 is B1 The maximum value can be 13.2% to 22% of the length of the long side of the current collector 141. If the length or thickness of the long side of the current collector 141 changes, the length d of the first part B1 B1The maximum value can be 4% to 23%. That is, the maximum length of the portion of electrode 140 that is not defined as an electrode tab, i.e., the undefined electrode tab section, is 660 mm, which can be said to be 4% to 23% of the length of electrode 140, considering that the length of the long side of the current collector 141 is the same as the length of the long side of electrode 140. Also, if the length of the short side of current collector 141 is the same as the length of the short side of electrode 140, then the maximum value of 660 mm for the portion of electrode 140 that is not defined as an electrode tab is 9.4 to 11 times the width of electrode 140. If the length or thickness of the short side of current collector 141 changes, the length d of the first part B1 B1 The maximum value can range from 2.5 times to 11 times.

[0137] Also, the length d of the first part B1 B1 If the length is 660 mm, and the length of the long side of the current collector 141 is 4 mm, then the ratio of the current path L2 / L1 may be 10.15. The length of the first part B1 is d B1 By reducing the length to less than 660 mm, the ratio of the current path L2 / L1 can be further reduced.

[0138] The upper limit of the current path ratio L2 / L1 may satisfy the minimum resistance requirement of the secondary battery. That is, it may be determined to show a secondary battery resistance smaller than the maximum resistance of the secondary battery. The values ​​of 4mΩ, which is the maximum DC resistance, and 3mΩ, which is the maximum AC resistance, applied in this embodiment may vary depending on the specifications of the secondary battery.

[0139] The inventors confirmed through simulation that the resistance of the secondary battery increases as the length of the undefined electrode tab section increases, as shown in Part B1 of the first section. However, they confirmed that once the length of the undefined electrode tab section exceeds a certain level, the resistance does not increase further and converges. By investigating the correlation between the length of the undefined electrode tab section and the resistance of the secondary battery, they were able to determine the length of the undefined electrode tab section that satisfies the minimum resistance requirement of the secondary battery.

[0140] Figure 10 is a schematic diagram of the electrode including the undefined electrode tab section used in the simulation, and Figure 11 is a resistance graph based on the number of welding points confirmed by the simulation.

[0141] Figure 10 shows the case where the electrode tabs 143a1 are spaced at equal intervals, with the connection points of the first and second paths indicated by ▲ and the end points of the electrodes indicated by ■. For example, if there are 6 electrode tabs 143a1, there are 7 undefined electrode tab sections 143a2, and if there are 7 electrode tabs 143a1, there are 8 undefined electrode tab sections 143a2. Thus, when the number of electrode tabs 143a1 is Q, we assumed an equal spacing condition in which the number of undefined electrode tab sections 143a2 is Q+1. Since each electrode tab 143a1 is welded to the current collector plate, the number of welding points is the same as the number of electrode tabs 143a1.

[0142] During the simulation, it was assumed that the length of the short side of the current collector 141' included in electrode 140' was 60mm to 85mm, the length of the long side of the current collector 141' was 3m to 5m, and the thickness of the current collector 141' was 5μm to 20μm.

[0143] The AC resistance of a secondary battery containing an electrode assembly in which such electrodes 140' are included as both the positive and negative electrodes was simulated while increasing the number of electrode tabs 143a1 from 1 to 50. Referring to Figure 11, which shows the results, it was found that the resistance converges as the number of electrode tabs 143a1 increases, and the result was obtained that the number of electrode tabs 143a1 required for the AC resistance of the secondary battery to be 2mΩ or less under the simulation conditions is 6.

[0144] The number of electrode tabs 143a1 can be converted to the length of the undefined electrode tab section 143a2. When the width of the electrode tabs 143a1 is 10 mm, if there are 6 electrode tabs 143a1 that are equally spaced in a current collector 141' with a long side length of 3 m to 5 m, the length of one undefined electrode tab section 143a2 is 660 mm. If there are 7 electrode tabs 143a1, the length of one undefined electrode tab section 143a2 is 564 mm. When there are 7 electrode tabs 143a1, the AC resistance of the secondary battery was simulated to be 1.7 mΩ.

[0145] From these simulations, it was found that it is desirable to keep the length of the undefined electrode tab section 143a2 to 660 mm or less. Considering that the length of the shorter side of the current collector 141' is 60 mm to 85 mm, the ratio of the length of the undefined electrode tab section 143a2, which is the longitudinal current path, to the length of the shorter side of the current collector 141', which is the widthwise current path, becomes 11 or less. As a result, it was found that if the ratio of current paths L2 / L1 is 11 or less, including the undefined electrode tab section, the low resistance condition of the secondary battery's AC resistance being 2 mΩ or less can be satisfied.

[0146] Based on these simulation results, the length d of the first part B1 is as proposed in this embodiment. B1 It is desirable to keep the length 660mm or less. In other words, the length of the undefined electrode tab section 143a2 can be controlled so that it does not exceed 660mm, thereby ensuring that the cell resistance satisfies the minimum resistance requirement for a secondary battery.

[0147] Part 1 B1 Length d B1 As the length increases, the ratio L2 / L1 of the current path increases, and the length d of the first part B1 increases. B1 If the length of the first part B1 becomes shorter, the ratio of the current path L2 / L1 becomes smaller. B1 This can be designed under conditions that satisfy the current path ratio L2 / L1 by applying the condition that when the uncoated portion of the third part B2 is bent toward the core, the cavity provided in the core of the electrode assembly 100 is not obstructed.

[0148] That is, the length d of the first part B1 B1 The length of the first part B1 is d, which can be determined by requirements and is 660 mm or less. B1 When the length is 660 mm and the length of the shorter side of the current collector 141 is 65 mm, the ratio of the current path L2 / L1 becomes 10.15, so the length of the first part B1 is d B1 This ensures that the ratio of current paths L2 / L1 is 10.15 or less. In other words, if the electrode 140 is designed to include the first part B1, the ratio of current paths increases compared to the case where the first part B1 does not exist and the entire electrode includes an uncoated portion like the third part B2. However, the length d of the first part B1 serves as a guide to satisfy the minimum resistance until the ratio of current paths L2 / L1 is 10.15 or less. B1 Because this increases the amount of material available, when the uncoated portion of the third part B2 is bent toward the core, it is possible to prevent it from obstructing the cavity provided in the core of the electrode assembly 100.

[0149] Figure 12 is a plan view showing the electrode structure of a second embodiment included in an electrode assembly according to another embodiment of the present invention.

[0150] The electrode 145a shown in Figure 12 differs from the first embodiment only in that the height of the second portion B3 gradually decreases as it moves toward the outer circumference; the rest of the configuration is substantially the same. In one modified example, the second portion B3 can be deformed in a stepped manner (see dotted line) in which the height decreases in stages. Here, the second portion B3 becomes smaller in height than the third portion B2. By making the second portion B3 smaller in height than the third portion B2, the deformation of the third portion B2 can be further suppressed when the second portion B3 is folded and then folded onto the folded third portion B2.

[0151] Figure 13 is a plan view showing the electrode structure of a third embodiment included in an electrode assembly according to another embodiment of the present invention.

[0152] In the third embodiment, the electrode 145b has a height of 0 or greater for the first portion B1 and the second portion B3, and is relatively smaller than that of the third portion B2. Also, the heights of the first portion B1 and the second portion B3 are the same. Similar to the first portion B1, the second portion B3 corresponds to an undefined electrode tab section, and the uncoated portion of the second portion B3 is not defined as an electrode tab, while the third portion B2 is defined as an electrode tab. In the winding direction, the length of the second portion B3 is equal to the length d of the first portion B1. B1 Shorter than the first portion. The second portion B3 may be an uncoated portion of the electrode area including the outermost winding turn. The third portion B2 may be defined as an electrode tab when bent along the radial direction of the electrode assembly 100. The first portion B1 and the second portion B3 are not bent along the radial direction. According to this embodiment, when the electrode assembly is inserted into the battery housing and the outer circumferential surface of the battery housing is pressed inward to form the beading portion, it is possible to prevent the beading portion and the second portion B3 from coming into contact with each other and causing an internal short circuit during the process in which the beading portion is pressurized around the second portion B3.

[0153] Figure 14 is a plan view showing the electrode structure of a fourth embodiment included in an electrode assembly according to another embodiment of the present invention.

[0154] In the fourth embodiment, the electrode 150 has a height of 0 or greater for the first portion B1 and the second portion B3, but is relatively smaller than that of the third portion B2. Also, the heights of the first portion B1 and the second portion B3 may be the same or different.

[0155] Preferably, the height of the third section B2 may be stepped, increasing gradually from the core side to the outer periphery side.

[0156] Patterns 1 to 7 divide the third section B2 around the position where the height of the uncoated portion 143 changes. Preferably, the number of patterns and the height (length in the Y-axis direction) and width (length in the X-axis direction) of each pattern can be adjusted to maximize stress distribution during the bending process of the uncoated portion 143. Stress distribution is intended to prevent the uncoated portion 143 from tearing when it is bent toward the core side of the electrode assembly.

[0157] Part 1 B1 Length d B1 The design applies the condition that when the pattern of the third part B2 is folded toward the core, it does not obstruct the cavity provided in the core. In one example, the length d of the first part B1 is B1 This can increase in proportion to the fold length of pattern 1. The fold length is the height of the pattern relative to the fold point of the pattern.

[0158] Preferably, the length d of the first part B1 B1 The radial width of the winding turn formed by the first part B1 can be set to be greater than or equal to the bending length of pattern 1. In the modified example, the length d of the first part B1 is B1 This can be set such that the value obtained by subtracting the radial width of the winding turn formed by the first part B1 from the bending length of pattern 1 is less than 0, or less than or equal to 10% of the core radius.

[0159] In a specific example, if electrode 150 is used to manufacture an electrode assembly for a cylindrical secondary battery with a form factor of 4680, the length d of the first part B1 is B1 The length can be set from 180mm to 350mm depending on the core diameter and the bending length of pattern 1. In this case, the ratio of the current path L2 / L1 can be 2.57 to 5.83. The length d of the first part B1 B1 Further adjustments can be made to ensure that the ratio of current paths L2 / L1 is between 2 and 5.

[0160] In one embodiment, the width of each pattern may be designed to constitute one or more winding turns of the electrode assembly.

[0161] In one modified example, the height of the third section B2 may be stepped, increasing from the core side to the outer periphery before decreasing.

[0162] In other modifications, the second part B3 may be modified to have the same structure as in the second embodiment.

[0163] Furthermore, in other variations, the pattern structure applied to the third part B2 can be extended to the second part B3 (see dotted line).

[0164] Figure 15 is a plan view showing the electrode structure of a fifth embodiment included in an electrode assembly according to another embodiment of the present invention.

[0165] Preferably, in electrode 160, the third portion B2 may include a plurality of segmented pieces 161. In other words, at least a portion of the third portion B2 may be divided into a plurality of independently foldable segmented pieces 161.

[0166] The height of the multiple segmented pieces 161 may increase gradually from the core side to the outer periphery side. The multiple segmented pieces 161 have a geometric shape in which the width decreases from the bottom to the top. Preferably, the geometric shape may be a trapezoid. As will be described later, the shape of the geometric shape can be deformed in various ways.

[0167] The segmented pieces 161 may be laser-notched. The segmented pieces 161 may be formed by known metal foil cutting processes such as ultrasonic cutting or punching. The segmented pieces 161 are folded and overlapped in the direction of the winding axis.

[0168] Since the segmented pieces 161 can be folded independently, it is desirable that the deformation of the uncoated portion 143 can be further suppressed when the segmented pieces 161 are folded. Furthermore, it has the advantage that the segmented pieces 161 can be folded and superimposed in multiple layers to prevent gaps from forming. The structure of the segmented pieces 161 prevents the uncoated portion 143 from tearing when it is folded.

[0169] The first section B1 begins from the short side of the core of the current collector 141, and the height of the first section B1 is constant along the winding direction and is not bent along the radial direction. Only the segmented piece 161 of the third section B2 is defined as an electrode tab. Therefore, in the electrode 160, in order to make the current path ratio L2 / L1, which is the ratio of the length of the longitudinal current path along the long side of the current collector 141 to the length of the widthwise current path L1 along the short side of the current collector 141, 11 or less, the length from the core-side end of the electrode 160 to the lower end of the first segmented piece 161 located longitudinally is defined as the length d of the first section B1. B1 Its length can be adjusted in the same way.

[0170] Preferably, the thickness of the current collector 141 is 5 μm to 25 μm, the width of the segmented piece 161 (see D in Figure 16) is 3 mm to 10 mm, and the height of the segmented piece (see H in Figure 16) may be 10 mm or less.

[0171] On one surface, multiple segmental pieces 161 may form multiple segmental piece groups as they move from the core side to the outer periphery side. At least one of the width, height, and spacing pitch of segmental pieces belonging to the same segmental piece group may be substantially the same. Preferably, the width, height, and spacing pitch of segmental pieces belonging to the same segmental piece group may be the same as each other.

[0172] The dimensions (width, height, spacing pitch) of the segmented pieces 161 can be adjusted considering factors such as resistance, ease of processing (e.g., whether laser notching can be applied without cracking), ease of bending, and the degree of overlap between multiple segmented pieces 161.

[0173] Preferably, the width and height of segments belonging to the same segment group may be substantially identical.

[0174] Figure 16 shows the definitions of the width D, height H, and spacing pitch P of the trapezoidal segment 161.

[0175] Referring to Figure 16, the width D, height H, and separation pitch P of the segmented piece 161 are designed to sufficiently increase the number of overlaps of the uncoated portion 143 to prevent abnormal deformation of the uncoated portion 143, thereby preventing the uncoated portion 143 near the bending point from tearing during bending and ensuring sufficient welding strength.

[0176] The bending of the segmented piece 161 is performed along or above the line G that passes through the lower end of the cutting groove 163. The cutting groove 163 facilitates smooth and easy bending of the segmented piece 161 radially of the electrode assembly.

[0177] The width D of the segmented piece 161 is defined as the distance between two points where two straight lines extending from the side edges 163b of the segmented piece 161 intersect with a straight line extending from the bottom 163a of the cutting groove 163. The height H of the segmented piece 161 is defined as the shortest distance between the uppermost edge of the segmented piece 161 and a straight line extending from the bottom 163a of the cutting groove 163. The spacing pitch P of the segmented pieces 161 is defined as the distance between two points where a straight line extending from the bottom 163a of the cutting groove 163 intersects with straight lines extending from the two side edges 163b connected to the bottom 163a. ​​When the side edges 163b and / or the bottom 163a are curves, the straight lines may instead be tangents extending from the side edges 163b and / or the bottom 163a at the intersection where the side edges 163b and the bottom 163a intersect.

[0178] Preferably, the width D of the segmented piece 161 is 1 mm or more. If D is less than 1 mm, when the segmented piece 161 is bent toward the core, areas or spaces (gaps) may occur where the segmented piece 161 does not overlap to an extent that sufficient welding strength can be ensured.

[0179] Preferably, the width D of the segmented piece 161 can be adaptively adjusted according to the radius of the winding turn in which the segmented piece 161 is located, such that the superposition of the segmented piece 161 is well performed radially when the segmented piece 161 is bent toward the core.

[0180] The height H of the segmented piece 161 may be 2 mm or more. If the height H of the segmented piece 161 is less than 2 mm, when the segmented piece 161 is bent toward the core, areas or spaces (gaps) may occur where the segmented piece 161 does not overlap to an extent that sufficient welding strength can be ensured.

[0181] The height H of the segmented piece 161 can be determined by applying the condition that the segmented piece 161 does not obstruct the core cavity when it is bent toward the core. Preferably, the height H of the segmented piece 161 can be adjusted so that more than 90% of the diameter of the core is open to the outside.

[0182] Preferably, the height H of the segmented piece 161 can gradually increase from the core side to the outer circumference side, depending on the radius of the winding turn in which the segmented piece 161 is located and the radius of the core.

[0183] In one embodiment, the height H of the segmented piece 161 increases from h1 to h as the radius of the winding turn increases. N It can increase gradually over N steps.

[0184] For example, if the overall radius of the winding turns of electrode 160 is 22 mm, and the height of the segmented piece 161 starts at 3 mm, the height of the segmented piece 161 increases sequentially to 3 mm, 4 mm, 5 mm, and 6 mm for each 1 mm increase in the radius of the winding turns including the segmented piece 161, and the height can be maintained substantially the same at 6 mm for the remaining winding turns. That is, the radial width of the variable height section of the segmented piece 161 within the radius of the overall winding turns is 3 mm, and the remaining radial section is a uniform height section.

[0185] In another example, the core radius r cWhen the length is 3m, the starting radii r1, r2, r3, and r4 of the winding turns containing segmented pieces 161 with heights of 3mm(h1), 4mm(h2), 5mm(h3), and 6mm(h4) are 6mm, 7mm, 8mm, and 9mm, respectively, and the height of the segmented piece 161 can be maintained at 6mm from radius 9mm to the last winding turn. Also, winding turns with radii smaller than 6mm(r1) do not need to contain segmented pieces 161. In such an example, since the segmented piece 161 with a height of 3mm(h1) that is closest to the core C is located from a winding turn with a radius of 6mm, even if the segmented piece 161 is bent toward the core C, it will only cover the radius section from 3mm to 6mm and will not substantially shield the core cavity.

[0186] In the height-variable section of the segmented piece 161, the height H of the segmented piece 161 may be 10 mm or less. For electrical insulation, the ends of the separator membrane 60 may extend further outward from the ends of the electrode 160 to a length corresponding to the insulation gap. Also, considering that the ends of the separator membrane 60 will meander when the electrode 160 and the separator membrane 60 are wound together, a section that provides the minimum meandering margin of the separator membrane 60 must be allocated to the uncoated portion 143. Furthermore, in order to cut the segmented piece 161, a minimum cutting scrap margin must be allocated to the ends of the current collector foil.

[0187] Preferably, the insulation gap may be 0.2 mm to 6 mm when the electrode 160 is the positive electrode. Also, when the electrode 160 is the negative electrode, the insulation gap may be 0.1 mm to 2 mm. Preferably, the minimum meandering margin of the separation film 60 may be 0 to 1 mm. Preferably, the cutting scrap margin may be 1.5 mm to 8 mm. The cutting scrap margin may not be allocated by the process of forming the segmented piece 161. For example, the cutting groove 163 may be formed so that the upper edge of the segmented piece 161 and the upper edge of the current collector foil coincide with each other, in which case the cutting scrap margin may be 0.

[0188] Considering the above conditions, the maximum height of the segmented segment 161 in the height-variable section of the segmented segment 161 can be set to 10 mm. This allows the height of the segmented segment 161 in the height-variable section of the segmented segment 161 to increase stepwise or progressively along the radial direction of the electrode assembly in the range of 2 mm to 10 mm.

[0189] Referring to Figure 16, the separation pitch P of the segmented pieces 161 can be adjusted in the range of 0.05 mm to 1 mm. If the separation pitch P is less than 0.05 mm, when the electrode 160 is run during the winding process, etc., stress may cause cracks in the uncoated portion 143 near the lower end of the cutting groove 163. On the other hand, if the separation pitch P exceeds 1 mm, when the segmented pieces 161 are bent, regions or spaces (gaps) may be created in which the segmented pieces 161 do not overlap each other to the extent that sufficient welding strength can be ensured.

[0190] On the other hand, if the current collector 141 of the electrode 160 is made of aluminum, it is more desirable to set the separation pitch P to 0.5 mm or more. When the separation pitch P is 0.5 mm or more, even if the electrode 160 runs at a speed of 100 mm / sec or more under a tension of 300 gf or more during the winding process, it is possible to prevent the occurrence of cracks in the lower part of the cutting groove 163.

[0191] As shown in Figure 16, a cutting groove 163 is interposed between two adjacent segmented pieces 161 in the winding direction. The cutting groove 163 is the space created by removing the uncoated portion 143. Preferably, the corners at both ends of the lower part of the cutting groove 163 have a rounded shape. That is, the cutting groove 163 includes a substantially flat bottom 163a and a rounded portion 163c. The rounded portion 163c connects the bottom 163a to the side edge 163b of the segmented piece 161. In a modified example, the bottom 163a of the cutting groove 163 may be arc-shaped. In this case, the side edge 163b of the segmented piece 161 can be smoothly connected by the arc shape of the bottom 163a.

[0192] The lower interior angle θ of the multiple segmented pieces 161 may increase as you move from the core side to the outer periphery side. In one example, the lower interior angle θ of the multiple segmented pieces 161 may increase gradually or stepwise as you move from the core side to the outer periphery side. The lower interior angle θ is the angle between the straight line extending from the bottom 163a of the cutting groove 163 and the straight line extending from the side edge 163b of the segmented piece 161. When the segmented piece 161 is symmetrical, the lower interior angles θ on the left and right sides are substantially the same.

[0193] As the radius of the electrode assembly increases, the radius of curvature increases. If the lower interior angle θ of the segmented piece 161 increases along with the radius of the electrode assembly, the stress generated in the radial and circumferential directions when the segmented piece 161 is bent can be relieved. Furthermore, as the lower interior angle θ increases, when the segmented piece 161 is bent, the overlapping area and number of overlaps with the inner segmented piece 161 also increase, thereby ensuring uniform welding strength in the radial and circumferential directions and forming a flat bent surface region.

[0194] Preferably, the lower interior angle θ can be determined by the radius of the winding turn in which the segmented piece 161 is located and the width D of the segmented piece 161. In one example, if the electrode 160 forms a winding structure with a diameter of 22 mm and a core radius of 4 mm, the lower interior angle of the segmented piece 161 can be increased progressively or stepwise in the 60° to 85° range of the height-variable section.

[0195] Referring further to Figure 15, the length d of the first part B1 is B1 The design ensures that when the segmented piece 161 of the third part B2 is folded toward the core, the core is exposed to the outside by more than 90% of its diameter. The length d of the first part B1 B1 This can increase in proportion to the folded length of the segmented piece 161 of the first group. The folded length is the length from the folding point to the upper edge of the segmented piece 161.

[0196] The bending point of the segmented piece 161 can be set on a line passing through the lower end of the cutting groove 163 or at a predetermined distance above that line. When the segmented piece 161 is bent toward the core at a predetermined distance from the lower end of the cutting groove 163, the radial superposition of the segmented pieces becomes easier. When the segmented piece 161 is bent, the outer segmented piece presses against the inner segmented piece with respect to the center of the core. In this case, if the bending point is at a predetermined distance from the lower end of the cutting groove 163, the inner segmented piece is pressed in the winding axis direction by the outer segmented piece, making the superposition of the segmented pieces easier. The separation distance of the bending point is preferably 1 mm or less. Since the minimum height of the segmented piece is 2 mm, the ratio of the separation distance of the bending point to the minimum height may be 50% or less.

[0197] In one embodiment, the width of each segment group may be designed to constitute the same winding turn of the electrode assembly. Here, the winding turn can be counted relative to the end of the first section B1 when the electrode 160 is in a wound state.

[0198] In other modifications, the width of each segment group may be designed to constitute at least one winding turn of the electrode assembly.

[0199] Groups 1 through 8 are merely examples of segmented piece groups included in part B2. The number of groups, the number of segmented pieces 161 in each group, and the width of the groups can preferably be adjusted so that the segmented pieces 161 overlap in multiple layers, thereby maximally distributing stress during the bending process of the uncoated portion 143 and ensuring sufficient welding strength with the current collector.

[0200] In the third part B2, the sections in which the height of the segmented piece 161 increases in stages with respect to the winding direction of the electrode 160 (groups 1 to 7) are defined as sections with variable segmented piece height, and the last group of segmented pieces (group 8) may be defined as a section with uniform height where the height of the segmented piece is maintained uniformly.

[0201] That is, in the third part B2, the height of segment 161 is h1~h N When it increases gradually up to h1~h N-1 The interval in which segmented pieces 161 having a height of (where N is the height index and is a natural number greater than or equal to 2) are placed becomes a height-variable interval, h N The section in which the segmented piece 161 having a certain height is placed becomes a section with uniform height.

[0202] The width of the first group may be 35-40% of the width of the first part B1. The width of the second group may be 130-150% of the width of the first group. The width of the third group may be 120-135% of the width of the second group. The width of the fourth group may be 85-90% of the width of the third group. The width of the fifth group may be 120-130% of the width of the fourth group. The width of the sixth group may be 100-120% of the width of the fifth group. The width of the seventh group may be 90-120% of the width of the sixth group. The width of the eighth group may be 115-130% of the width of the seventh group. Length d of the second part B3 B3 The width of the first section B1 can be between 180mm and 350mm.

[0203] The reason why the widths of groups 1 through 8 do not show a constant increasing or decreasing pattern is that while the width of the segmented pieces gradually increases from group 1 to group 8, the number of segmented pieces included in each group is limited to an integer, and the thickness of the electrodes has a slight deviation in the winding direction. As a result, the number of segmented pieces may decrease in a particular group of segmented pieces. Consequently, the width of the groups may show an irregular pattern of change as one moves from the core side to the outer circumference side, as illustrated above.

[0204] According to the above embodiments, the welding strength of the current collector plate can be improved by sufficiently increasing the number of overlapping segments 161. By optimizing the dimensions (width, height, and spacing pitch) of the segments 161 and sufficiently increasing the number of overlapping segments 161 in the area used as the welding target area, the physical properties of the area where the current collector plate is welded can be improved.

[0205] Figure 15 also shows typical current paths. The connection point between the first and second paths is indicated by ▲, and the electrode end points are indicated by ■. The connection point between the first and second paths can be any position in the second section B3 and the third section B2, but for the sake of illustration, it is shown as one location in the first group and one location in the eighth group. The electrode end points can also be any position, but it is shown as one location to indicate the length L1 of the current path in the width direction and as one location at the maximum current path.

[0206] Here again, L2, which determines the upper limit of the current path ratio L2 / L1, is the distance to the end point of the electrode in the third part B2 defined as the electrode tab, and the length d of the first part B1. B1 This is the result. The length of the first part B1 is d. B1 The ratio of the current paths L2 / L1 can be adjusted by adjusting the current path ratio L2 / L1. Although such a ratio of current paths L2 / L1 may slightly increase the resistance, it will satisfy the minimum resistance requirement of the secondary battery. Therefore, when further consideration is given to the degree of superposition of the segmented pieces 161, ensuring welding strength, etc., it can be reduced to 11 or less, 10.15 or less, 8.5 or less, or in the range of 2 to 5. For example, the length d of the third part B2 B2 If it is necessary to increase the degree of overlap of the segmented segments 161 by making the segmented segments 161 sufficiently long or by forming more of them, the current path ratio L2 / L1 may be reduced to 8.5 or less, or to a range of 2 to 5. The significance of this invention lies in the fact that it sets an upper limit for the current path ratio L2 / L1 from the viewpoint of designing a low-resistance cell that minimizes the current path. If the upper limit for the current path ratio L2 / L1 is exceeded, the minimum resistance requirement for the secondary battery cannot be met.

[0207] In an electrode 160 with such a structure, the third portion B2 can be bent to become a welding area. In the winding direction, the length d of the third portion B2 B2 The length of the first part B1 is d B1 It may be longer than this. Length d of the third part B2 B2 The length of the second part B3 is d B3 It may be longer than this. Length d of the third part B2B2 By increasing the length, multiple bends can be superimposed during folding. Length d of the third part B2 B2 By lengthening the welding area, a sufficient welding area can be secured.

[0208] Furthermore, according to other modifications, when the uncoated portion 143 of the electrode 160 has a segmented structure, the electrode 160 may include segmented section omission sections 164 in which some of the multiple segmented sections are omitted regularly or irregularly, as shown in Figure 17. Figure 17 is a plan view showing a modified electrode structure according to a fifth embodiment of the present invention.

[0209] Referring to Figure 17, preferably, there may be multiple segmental omission sections 164. In one example, the width of the segmental omission section 164 may be constant as you move from the core side to the outer periphery side. In another example, the width of the segmental omission section 164 may increase or decrease regularly or irregularly as you move from the core side to the outer periphery side. Preferably, the height of the uncoated portion present in the segmental omission section 164 may correspond to the height of the first portion B1 and / or the second portion B3.

[0210] The number of segmented segments 161 present in the segmented segment omission section 164 can be at least one. The electrode 160 may include uncoated sections in which the number of segmented segments 161 present in the segmented segment omission section 164 increases as you move from the core towards the outer circumference, as shown in Figure 17.

[0211] Even when a segmented section 164 is placed in the middle of the uncoated portion 143 in this manner, the segmented section 164 corresponds to an undefined electrode tab section, so the length of the segmented section 164 can be determined by considering the condition that the ratio of current paths L2 / L1 in the undefined electrode tab section is 11 or less.

[0212] Figure 18 is an upper plan view showing independent regions where multiple segmented pieces can be located when an electrode according to a modified version of the present invention is wound onto an electrode assembly.

[0213] Preferably, the width of the segmented section omitted section 164 can be set such that, as shown in Figure 18, when the electrode 160 is wound, the segmented section located at each winding turn is located within a predetermined independent region 166 with respect to the core C of the electrode assembly 200.

[0214] In other words, when the electrode assembly 200 is viewed from the winding axis direction, the multiple segmented pieces 161 can be located within multiple independent regions 166 with respect to the core C. The number of independent regions 166 can be varied to two, three, four, five, or the like.

[0215] Preferably, the independent region 166 may be a sector. In this case, the angles between the independent regions 166 may be substantially the same. Also, the inscribed angle δ of the independent region 166 may be 20° or more, selectively 25° or more, selectively 30° or more, selectively 35° or more, or selectively 40° or more.

[0216] In the modified example, the independent region 166 may have the form of a geometric figure such as a square, rectangle, balanced quadrilateral, or trapezoid.

[0217] In the above-described case, a welded portion with the current collector plate can be formed only in the independent region 166, and the current collector plate can be designed to have a leg structure corresponding to the independent region 166, which is advantageous in terms of current collection efficiency.

[0218] Figure 19 is a plan view showing the structure of an electrode according to the sixth embodiment of the present invention.

[0219] Referring to Figure 19, the electrode 170 of the sixth embodiment is substantially identical in its remaining configuration, except that the shape of the segmented piece 161' differs from that of the previously described embodiment. Therefore, unless otherwise specified, the configuration of the fifth embodiment is also applicable to the sixth embodiment.

[0220] The segmented piece 161' has the form of a geometric figure with substantially the same width at the top and bottom. Preferably, the segmented piece 161' may have the form of a quadrilateral.

[0221] Figure 20 shows the definitions of the width, height, and spacing pitch of the segmented pieces included in the electrode according to the sixth embodiment of the present invention.

[0222] Referring to Figure 20, the width D, height H, and separation pitch P of the segmented piece 161' can be set to prevent the uncoated portion 143 from tearing during bending and to prevent abnormal deformation of the uncoated portion 143 while sufficiently increasing the number of overlaps of the uncoated portion 143 to improve the welding strength with the current collector. Abnormal deformation means that the uncoated portion below the bending point collapses and deforms irregularly without being able to maintain a straight state.

[0223] The width D of the segmented piece 161' is defined as the distance between two points where two straight lines extending from the side edges of the segmented piece 161' intersect with a straight line extending from the bottom 163a of the cutting groove 163. The height H of the segmented piece 161' is defined as the shortest distance between the uppermost edge of the segmented piece 161' and a straight line extending from the bottom 163a of the cutting groove 163. The spacing pitch P of the segmented pieces 161' is defined as the distance between two points where a straight line extending from the bottom 163a of the cutting groove 163 intersects with two straight lines extending from the two side edges 163b connected to the bottom 163a. ​​If the side edges 163b and / or the bottom 163a are curves, the straight lines may instead be tangents extending from the side edges 163b and / or the bottom 163a at the intersection where the side edges 163b and the bottom 163a intersect.

[0224] Preferably, the conditions relating to the width D, height H, and separation pitch P of the segmented piece 161' are substantially the same as those of the fifth embodiment described above, so a repetitive explanation is omitted. However, since the segmented piece 161' has a rectangular shape, the lower interior angle of the segmented piece 161' can be kept constant at 90°.

[0225] Similar to the electrode 160 of the fifth embodiment, the electrode 170 of the sixth embodiment may also include segment omission sections 164 in which some of the multiple segment pieces are omitted regularly or irregularly.

[0226] As in the fifth and sixth embodiments, when the third portion B2 includes multiple segmental pieces 161, 161', the shape of each segmental piece 161, 161' can be varied.

[0227] According to yet another aspect of the present invention, after the electrodes 160 and 170 are wound up as an electrode assembly, the segmented pieces exposed on the upper and lower parts of the electrode assembly can be superimposed in multiple layers along the radial direction of the electrode assembly to form a bent surface region.

[0228] The bent surface region F, formed by bending the segmented piece 161 toward the core C side of the electrode assembly 200, can be formed on both the upper and lower parts of the electrode assembly 200. Figure 21 is a schematic upper perspective view showing an electrode assembly with the bent surface region formed thereon.

[0229] Referring to Figure 21, the bent surface region F has a structure in which segmented pieces 161 are superimposed in multiple layers in the direction of the winding axis. The direction of superimposition is the winding axis.

[0230] The height, width, and spacing pitch of the segmented segments 161 can be adjusted according to the radius of the winding turn containing the segmented segments 161, and the number of layers of segmented segments 161 at each position in the bent surface region F can be optimized to match the required welding strength of the current collector plate.

[0231] The electrode structures of the above-described embodiments (and modifications) are applicable to positive and negative electrodes included in jelly roll type or other types of electrode assemblies known in the art.

[0232] In the present invention, the positive electrode active material coated on the positive electrode and the negative electrode active material coated on the negative electrode can be any active material known in the industry without limitation.

[0233] For example, the positive electrode active material is a material with the general chemical formula A[A] x M y ]O 2+z(A contains at least one or more elements of Li, Na, and K; M contains at least one or more elements selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, 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 such that the compound maintains electrical neutrality.) may contain an alkali metal compound represented thereby.

[0234] In other examples, 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 (M contains at least one or more elements having an average oxidation state of ³; M 2 (M contains at least one or more elements having an average oxidation state of ⁴; 0≦x≦1).

[0235] In still other examples, the positive electrode active material has the general chemical formula Li a M 1 x Fe 1‐x M 2 y P 1‐y M 3 z O 4‐z (M 1 (M contains at least one or more elements selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, and Mg; M 2 (M contains at least one or more elements selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Al, Mg, As, Sb, Si, Ge, V, and S; M 3 (M contains a halogen group element selectively containing F; 0 < a≦2, 0≦x≦1, 0≦y < 1, 0≦z < 1; the stoichiometric coefficients a, x, y, and z are selected such that the compound maintains electrical neutrality.), or it may be a 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, and Mg.].

[0236] Preferably, the positive electrode active material may contain primary particles and / or secondary particles formed by aggregation of primary particles.

[0237] For example, the negative electrode active material may be a carbon material, lithium metal or lithium metal compound, silicon or silicon compound, tin or tin compound, etc. Metal oxides such as TiO2 and SnO2, which have a potential of less than 2V, can also be used as negative electrode active materials. As for carbon materials, both low-crystallinity carbon and high-crystallinity carbon can be used.

[0238] The separation membrane may be made from porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, or ethylene / methacrylate copolymers, either alone or in laminations thereof. In another example, the separation membrane may be made from ordinary porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fibers or polyethylene terephthalate fibers.

[0239] At least one surface of the separation membrane may include a coating layer of inorganic particles. Furthermore, the separation membrane itself may consist of a coating layer of inorganic particles. The particles constituting the coating layer may have a structure in which they are bound to a binder such that an interstitial volume exists between adjacent particles.

[0240] Inorganic particles can consist of inorganic materials with a dielectric constant of 5 or more. As an unrestricted example, the inorganic particles may be Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb) 2 / 3It may contain at least one substance selected from the group consisting of O3-PbTiO3 (PMN-PT), BaTiO3, hafnia (HfO2), SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, and Y2O3.

[0241] Figure 22 is a cross-sectional view of a jelly roll type electrode assembly, in which one of the electrodes from the 5th and 6th embodiments (and their variations) is applied as the positive and negative electrodes, cut along the Y-axis direction (winding axis direction).

[0242] Referring to Figure 22, the positive electrode uncoated portion 143a includes a first portion B1 adjacent to the core of the electrode assembly 200, a second portion B3 adjacent to the outer peripheral surface of the electrode assembly 200, and a third portion B2 interposed between the first portion B1 and the second portion B3.

[0243] The height of the first part B1 is relatively smaller than the height of the third part B2. Also, the bend length of the innermost uncoated positive electrode portion 143a in the third part B2 is the same as or smaller than the radial length R of the first part B1. The bend length H' is the distance from the point where the uncoated positive electrode portion 143a is bent to the upper end of the uncoated positive electrode portion 143a. In the modified example, the bend length H' may be smaller than the sum of the radial length R of the first part B1 and 10% of the core C radius.

[0244] Therefore, even if the third part B2 is bent, more than 90% of the diameter of the core C of the electrode assembly 200 remains open to the outside. The core C is located in the center of the electrode assembly 200 and has a cavity. If the cavity of the core C is not blocked, the electrolyte injection process is facilitated and the efficiency of electrolyte injection is improved. In addition, a welding jig can be inserted through the core C to facilitate the welding process between the negative electrode (or positive electrode) side current collector plate and the battery housing (or electrode terminal).

[0245] The height of the second part B3 is relatively smaller than the height of the third part B2. This can prevent the phenomenon that the beading part of the battery housing and the second part B3 come into contact with each other and cause an internal short circuit during the process of pressurizing the beading part near the second part B3.

[0246] The non-coated part 143b of the negative electrode has the same structure as the non-coated part 143a of the positive electrode. In a modified example, the non-coated part 143b of the negative electrode may have a conventional electrode structure or an electrode structure of other embodiments (modified examples).

[0247] In a modified example, unlike that shown in FIG. 22, the height of the second part B3 may decrease gradually or stepwise. Also, in FIG. 22, although a part of the outer peripheral side of the height of the third part B2 is the same, the height of the third part B2 may increase gradually or stepwise from the boundary between the first part B1 and the third part B2 to the boundary between the third part B2 and the second part B3. When the third part B2 is divided into a plurality of segmented pieces, the section where the height of the non-coated part 143a of the positive electrode changes becomes the height variable section E2 of the segmented piece.

[0248] More specifically, based on the cross-section in the winding axis direction, the electrode assembly 200 sequentially includes a segmented piece omission section E1 where there is no segmented piece, a height variable section E2 where the height of the segmented piece is variable, and a height uniform section E3 where the height of the segmented piece is uniform, along the radial direction.

[0249] The ends 201 of the non-coated part 143a of the positive electrode and the non-coated part 143b of the negative electrode can be bent from the radial direction of the electrode assembly 200, for example, from the outer peripheral side to the core side. At this time, the first part B1 and the second part B3 are not bent.

[0250] The aforementioned segmented pieces 161 and 161' are arranged in the height-variable section E2 and the height-uniform section E3, and are bent along the radial direction of the electrode assembly 200 to form a bent surface region (F in Figure 21). Since a structure in which a current collector plate is welded over a wide area to the bent surface region F formed by bending the segmented pieces 161 and 161' can be applied, the energy density of the electrode assembly 200 including it can be improved and the resistance can be reduced.

[0251] When the third part B2 includes multiple segmented pieces, the bending stress is relieved, which prevents tearing or abnormal deformation of the positive electrode uncoated portion 143a and the negative electrode uncoated portion 143b near the bending point. Furthermore, when the width and / or height and / or spacing pitch of the segmented pieces 161, 161' are adjusted according to the numerical range of the above-described embodiment, the segmented pieces 161, 161' are bent toward the core C side and overlapped in multiple layers to the extent that sufficient welding strength can be ensured, without forming holes (gaps) in the bent surface region.

[0252] In this embodiment, the segmental omission section E1 corresponds to the first part B1.

[0253] On the other hand, a modified version is also possible in which the height-adjustable section E2 is omitted from the electrode assembly 200.

[0254] Figure 23 is a plan view showing the deformed structure of the electrode according to the fifth embodiment of the present invention.

[0255] In Figure 23, the modified electrode 180 has a uniform height for the segmented pieces 161, and when manufactured as an electrode assembly 200 as in Figure 22, it includes only a segmented piece omitted section E1 and a uniform height section E3, without a height variable section E2, except that the rest of the configuration is substantially the same. Thus, unless otherwise specified, the configuration of the fifth embodiment is also applicable to this modified example. Furthermore, the second part B3 is not divided into segmented pieces, and the height of the first part B1 and the height of the second part B3 are the same.

[0256] Figure 23 shows the maximum current paths L1 and L2 (the connection point between the first and second paths is indicated by ▲, and the end points of the electrodes are indicated by ■).

[0257] In an electrode 180 having the structure shown in Figure 23, the length d of the first portion B1 B1 After manufacturing secondary batteries of the examples and comparative examples by varying the parameters, AC resistance, DC resistance, low-temperature cycle, and rapid-charge cycle were tested. The number of segmented pieces 161 was 115, with the widest part of each segmented piece being 8 mm and the height being 6 mm. The negative electrode current collector was made of copper with a thickness of 10 μm, and the positive electrode current collector was made of aluminum with a thickness of 15 μm. For each current collector, the short side length, which is approximately close to L1, was 65 mm, and the long side length was 4 m. The positive electrode active material contained a lithium composite transition metal oxide, and the negative electrode active material contained graphite. A polyolefin separation membrane was used. The electrolyte was a solvent prepared by dissolving 1.4 M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 20:70:10.

[0258] For example, AC resistance can be evaluated by applying a 1kHz AC current using a commonly used AC impedance meter. In this experiment, after formation with a 200mA current (0.1C), CC / CV charging was repeated three times under the conditions of 4.2V, 666mA (0.3C, 0.05C cutoff), and CC discharge was repeated three times under the conditions of 2.5V, 666mA (0.3C). Subsequently, AC resistance was measured in the range of 10mHz to 100kHz using a multi-impedance analyzer (Biologic, model: VMP3) at a temperature of 25°C and a State of Charge (SOC) of 50%.

[0259] For example, DC resistance can be measured using a commonly used DC resistance meter by placing a probe on the surface of the electrode so that the current flows only on the electrode surface. In this experiment, a fully charged secondary battery was discharged to 50% of its state of charge (SOC) at room temperature, and the voltage drop that occurred when it was discharged with a current of 0.5C for 10 seconds was recorded. The DC resistance (DC-IR) value was then calculated using Ohm's law (R=V / I) [discharge pulse (0.5C pulse applied for 10 seconds), DC-IR=(V0-V1) / I, where V0 is the voltage before the discharge pulse and V1 is the voltage after the discharge pulse was applied].

[0260] Low-temperature cycle performance (low-temperature life characteristic evaluation) was performed by first forming the battery at 200mA current (0.1C), then repeating CC / CV charging under conditions of 4.2V, 666mA (0.3C, 0.05C cutoff) and CC discharge under conditions of 2.5V, 666mA (0.3C) 300 times (cycles) at 10°C. The first discharge capacity was then used as the initial capacity, and the 300th discharge capacity was compared to the initial capacity to calculate the capacity retention rate in %. Discharge capacity measurement can be performed using equipment such as the PNE-0506 charge / discharger (manufacturer: PNE Solutions Co., Ltd., 5V, 6A).

[0261] Rapid cycle performance was evaluated by repeatedly performing a 25-minute rapid charge from 10% SOC to 80% SOC, followed by a discharge to 10% SOC, 500 times. All charge and discharge cycles were performed in CC mode. After 500 cycles, the percentage change in charge capacity was calculated.

[0262] The secondary battery of Example 1 has a length d of the first part B1 that determines L2. B1 The length of the first part B1 of the secondary battery of Comparative Example 1 is 556 mm, and the length of the first part B1 is d B1 The length of the first part B1 of the secondary battery of Comparative Example 2 is 680 mm, and the length of the first part B1 is d B1 The length was 920 mm. Example 1 is the length d of the first part B1. B1 Since it is 556 mm, it satisfies the requirement of being 660 mm or less, which is the length of the undefined electrode tab section 143a2 confirmed by simulation. Comparative Examples 1 and 2 have a length d of the first part B1. B1is greater than 660 mm, which is the length of the electrode tab undefined section 143a2 confirmed by simulation.

[0263] Table 1 organizes and shows the conditions and experimental result values of Example 1, Comparative Example 1, and Comparative Example 2.

[0264]

Table 1

[0265] Referring to Table 1, in the case of Example 1, the AC resistance was 1.5 mΩ and the DC resistance was measured to be 3.6 mΩ. As a result of simulation, the AC resistance satisfies less than 2 mΩ, and the DC resistance also satisfies the requirement conditions for the minimum resistance of the secondary battery (the DC resistance is 4 mΩ or less and the AC resistance is 3 mΩ or less).

[0266] The DC resistance measured in Comparative Example 1 was 3.9 mΩ and the AC resistance was 1.7 mΩ, so it satisfies the requirement conditions for the minimum resistance of the secondary battery. However, since the low-temperature cycle was 76% and the rapid charge cycle was 83%, the performance was inferior compared to Example 1 where the low-temperature cycle was 82% and the rapid charge cycle was 87%. In particular, from the perspective of the rapid charge cycle, when the length d of the first part B1 is B1 660 mm or less, it can be seen that it is advantageous.

[0267] Since the DC resistance measured in Comparative Example 2 was 4.3 mΩ, it does not satisfy the requirement conditions for the minimum resistance of the secondary battery. Since the low-temperature cycle was 58% and the rapid charge cycle was measured to be 64%, the performance was inferior to that of Comparative Example 1. That is, as the length d of the first part B1 B1 increases beyond 660 mm (680 mm → 920 mm), the resistance increases, and it can be seen that the low-temperature cycle and rapid charge cycle performance are inferior.

[0268] Thus, by the example of the present invention, the length d of the first part B1 B1When the ratio L2 / L1 of the current path is set within a predetermined range to be 11 or less, it is possible to design a low-resistance cell that satisfies the requirement for the minimum resistance of the secondary battery, and it can have excellent performance from the viewpoints of low-temperature cycles and rapid charge cycles. Therefore, it can be confirmed that it is suitable for manufacturing a cylindrical secondary battery with an increased form factor for application to electric vehicles.

[0269] The structures of various electrode assemblies according to embodiments of the present invention can be applied to cylindrical secondary batteries.

[0270] Preferably, the cylindrical secondary battery can be, for example, a cylindrical secondary battery in which the ratio of the form factor (a value obtained by dividing the diameter of the cylindrical secondary battery by the height, that is, the ratio of the diameter Φ to the height H) is greater than about 0.4.

[0271] Preferably, the diameter of the cylindrical secondary battery can be 40 mm to 50 mm, and the height can be 60 mm to 130 mm. The form factor of the cylindrical secondary battery according to an embodiment can be, for example, 46110, 4875, 4811, 4880 or 4680. In the numerical value indicating the form factor, the first two digits indicate the diameter of the secondary battery, and the remaining digits indicate the height of the secondary battery.

[0272] When applying a tabless electrode assembly to a cylindrical secondary battery with a form factor ratio exceeding 0.4, when bending the non-coated portion, the stress applied in the radial direction is large and the non-coated portion is likely to break. Also, when welding a current collector to the bent surface area of the non-coated portion, in order to ensure sufficient welding strength and reduce resistance, it is necessary to sufficiently increase the number of layers of the non-coated portion in the bent surface area. Such requirements can be achieved by the electrodes and electrode assemblies according to embodiments (modified examples) of the present invention. In particular, such requirements can be achieved by making the ratio (L2 / L1) of the current path 11 or less, so a low-resistance design is possible. <##

[0273] An embodiment of the present invention is a substantially cylindrical secondary battery, having a diameter of approximately 46 mm, a height of approximately 110 mm, and a form factor ratio of 0.418.

[0274] Another embodiment of the secondary battery may be a cylindrical secondary battery with a nearly cylindrical shape, a diameter of approximately 48 mm, a height of approximately 75 mm, and a form factor ratio of 0.640.

[0275] Furthermore, the secondary battery according to the other embodiment may be a cylindrical secondary battery with a diameter of approximately 48 mm, a height of approximately 110 mm, and a form factor ratio of 0.436.

[0276] Furthermore, the secondary battery according to the other embodiment may be a cylindrical secondary battery with a diameter of approximately 48 mm, a height of approximately 80 mm, and a form factor ratio of 0.600.

[0277] Furthermore, a secondary battery according to another embodiment may be a cylindrical secondary battery with a nearly cylindrical shape, having a diameter of approximately 46 mm, a height of approximately 80 mm, and a form factor ratio of 0.575.

[0278] Traditionally, rechargeable batteries with a form factor ratio of approximately 0.4 or less were used. Specifically, for example, 18650 and 21700 rechargeable batteries were used. In the case of an 18650 battery, its diameter is approximately 18 mm, its height is approximately 65 mm, and its form factor ratio is 0.277. In the case of a 21700 battery, its diameter is approximately 21 mm, its height is approximately 70 mm, and its form factor ratio is 0.300.

[0279] The following describes in detail a cylindrical secondary battery according to an embodiment of the present invention.

[0280] Figure 24 is a cross-sectional view of a cylindrical secondary battery according to one embodiment of the present invention. The secondary battery 300 in Figure 24 includes an electrode assembly 200, which is a jelly roll type electrode assembly in which one of the electrodes from the fifth embodiment and the sixth embodiment (and their variations) is applied as the positive and negative electrodes. Figure 24 is a cross-sectional view of such a secondary battery 300 cut along the winding axis.

[0281] Referring to Figure 24, in the electrode assembly 200, the uncoated positive electrode portion 143a and the uncoated negative electrode portion 143b are arranged in opposite directions. The uncoated positive electrode portion 143a and the uncoated negative electrode portion 143b are exposed to the outside of the separation membrane (see 60 in Figure 7). In such an electrode assembly 200, only a portion of the uncoated positive electrode portion 143a and the uncoated negative electrode portion 143b may be defined and used as electrode tabs. For example, only a portion of the uncoated positive electrode portion 143a may be used as the positive electrode tab, and only a portion of the uncoated negative electrode portion 143b may be used as the electrode tab.

[0282] Furthermore, the secondary battery 300 includes a cylindrical battery housing 305 that houses the electrode assembly 200 and is connected to the uncoated negative electrode portion 143b. The battery housing 305 is made of a conductive metal material. For example, the battery housing 305 may be made of iron, nickel-plated iron, or stainless steel (SUS) and may be a battery can, but the present invention is not limited thereto.

[0283] Preferably, one side of the battery housing 305 (the lower part in this embodiment) is open to form an open portion. In the battery housing 305, the side opposite the open portion is a closed portion. In this embodiment, the closed portion is the bottom 310 of the battery housing 305. The bottom 310 of the battery housing 305 is circular. The side surface (outer surface) and the bottom 310 of the battery housing 305 may be formed integrally. The bottom 310 of the battery housing 305 has a substantially flat shape. The battery housing 305 houses the electrode assembly 200 through the open portion and also houses the electrolyte. The side surface of the battery housing 305 extends from the bottom 310 for a certain length.

[0284] The bottom portion 310 of the battery housing 305 has a structure in which the positive electrode terminal 315 is riveted into the through hole 320 by a crimping process. The secondary battery 300 may also include a rivet gasket 325 interposed between the positive electrode terminal 315 and the through hole 320.

[0285] The positive terminal 315 is made of a conductive metallic material. For example, the positive terminal 315 may be made of a material mainly composed of aluminum, but the present invention is not limited thereto. The positive terminal 315 may be made of a 10-series aluminum alloy that is easy to rivet and has low resistance. Part of the positive terminal 315 is inserted inside the battery housing 305, and the other part is exposed outside the battery housing 305.

[0286] The rivet gasket 325 may be made of a polymer resin having insulating and elastic properties. For example, the rivet gasket 325 may be made of polypropylene, polybutylene terephthalate, polyfluorinated ethylene, etc., but the present invention is not limited to these.

[0287] The secondary battery 300 includes a positive electrode current collector plate 330 connected to the positive electrode uncoated portion 143a. The connection between the positive electrode uncoated portion 143a and the positive electrode current collector plate 330 can be performed by welding. The positive electrode current collector plate 330 is connected to the electrode tab-defining section of the positive electrode uncoated portion 143a. The positive electrode current collector plate 330 is also connected to the positive electrode terminal 315. The positive electrode current collector plate 330 and the positive electrode terminal 315 are connected by laser welding. The positive electrode current collector plate 330 may be made of the same metal as the positive electrode current collector and / or the positive electrode terminal 315, or of a material that is easily welded to them. For example, the positive electrode current collector plate 330 may be made of a material mainly composed of aluminum. For example, it may be iron, nickel-plated iron, or stainless steel. The positive electrode terminal 315 is connected to the positive electrode uncoated portion 143a via the positive electrode current collector plate 330.

[0288] Furthermore, the secondary battery 300 may include a sealant 335 that seals the open portion of the battery housing 305 in a manner that provides insulation from the battery housing 305. Preferably, the sealant 335 may include a non-polar cap plate 340 and a sealing gasket 345 interposed between the peripheral edge of the cap plate 340 and the open portion of the battery housing 305.

[0289] The cap plate 340 may be made of a conductive metal material such as aluminum, iron, nickel-plated iron, or SUS. The sealing gasket 345 may be made of insulating and elastic polypropylene, polybutylene terephthalate, polyfluorinated ethylene, etc. However, the present invention is not limited by the materials of the cap plate 340 and the sealing gasket 345. The cap plate 340 may cover the open portion of the battery housing 305. The cap plate 340 is non-polar even if it is made of a conductive metal material. Non-polarity may mean that the cap plate 340 is not connected to the electrode assembly 200. It may also mean that it is electrically insulated from the battery housing 305 and the positive electrode terminal 315. Because it is non-polar, the cap plate 340 does not function as an electrode terminal. The cap plate 340 does not need to be connected to the electrode assembly 200 and the battery housing 305, and its material does not necessarily need to be a conductive metal.

[0290] The cap plate 340 may include a vent notch 350 that ruptures when the internal pressure of the battery housing 305 exceeds a critical value. The vent notch 350 may be formed on one or both sides of the cap plate 340. The vent notch 350 may form a continuous or discontinuous circular pattern, a linear pattern, or other pattern on the surface of the cap plate 340. For example, the vent notch 350 may be formed in the shape of a substantially circular ring with a certain width. Such a circular ring-shaped vent notch 350 may have the same center as the center of the cap plate 340 and have a radius smaller than the radius of the cap plate 340.

[0291] The rupture pressure of the battery housing 305 can be controlled by controlling the depth and width of the vent notch 350. For example, the vent notch 350 can be used to control the internal pressure of the battery housing 305 to 15-35 kgf / cm². 2 It can be set to rupture when it reaches a certain range. The vent notch 350 can be formed by partially reducing the thickness of the battery housing 305 by notching. The vent notch 350 may have a thickness gradient. A thickness gradient means that the cross section of the vent notch 350 is formed at a constant angle with respect to a predetermined horizontal plane. Such a vent notch 350 ruptures when the internal pressure of the battery housing 305 rises abnormally, releasing all the internal gas to the outside.

[0292] The battery housing 305 is bent inward to secure the seal 335 and may include a crimping part 355 that, together with the sealing gasket 345, surrounds and secures the periphery of the cap plate 340. Preferably, the lower surface of the cap plate 340 may be located above the lower end of the crimping part 355. In such a case, a vent space is formed below the cap plate 340, allowing for smooth gas release when the vent notch 350 ruptures.

[0293] The battery housing 305 may further include a beading part 360 that is press-fitted inward into the region adjacent to the opening. The beading part 360 is recessed inward into the battery housing 305. The beading part 360 supports the peripheral edge of the sealant 335, in particular the outer circumferential surface of the sealant gasket 345, when the sealant 335 is secured by the crimping part 355.

[0294] The secondary battery 300 may further include a negative electrode current collector plate 365 connected to the uncoated negative electrode portion 143b. The connection between the uncoated negative electrode portion 143b and the negative electrode current collector plate 365 may be made by welding. The negative electrode current collector plate 365 is connected to the electrode tab-defining section of the uncoated negative electrode portion 143b. The negative electrode current collector plate 365 may be made of the same metal as the negative electrode current collector, or of a material that is easily welded to it. For example, it may be copper or a copper alloy, nickel or a nickel alloy, iron, SUS, or a composite material thereof. Preferably, at least a portion 365a of the edge of the negative electrode current collector plate 365 that does not come into contact with the uncoated negative electrode portion 143b may be interposed between the beading portion 360 and the sealing gasket 345 and secured by a crimping portion 355. Selectively, at least a portion 365a of the edge of the negative electrode current collector plate 365 may be fixed by welding to the inner circumferential surface 360a of the beading portion 360 adjacent to the crimping portion 355. This connects the negative electrode current collector plate 365 to the battery housing 305, and the battery housing 305 is connected to the negative electrode uncoated portion 143b by the negative electrode current collector plate 365. The negative electrode current collector plate 365 may also have a current collector hole (not shown) in its center. The current collector hole does not obstruct the cavity of the core C. The negative electrode current collector plate 365, by including the current collector hole, allows the laser beam to pass through when welding the positive electrode current collector plate 330 to the positive electrode terminal 315, so that the laser beam reaches the positive electrode current collector plate 330.

[0295] Each current collector plate 330 and 365 guides the current generated at each electrode of the electrode assembly 200 to the positive terminal 315 and the battery housing 305. Each current collector plate 330 and 365 is a component connected to the ends of each electrode, namely the uncoated positive electrode portion 143a and the uncoated negative electrode portion 143b, to derive current. Because the current is introduced and deduced by directly connecting each current collector plate 330 and 365 to the uncoated positive electrode portion 143a and the uncoated negative electrode portion 143b by welding or other means, a separate current collector tab is unnecessary. This eliminates the need for the current collector tab installation process, thereby improving productivity. Furthermore, the space required to house the current collector tab can be reduced, resulting in a more compact battery structure overall and improved space utilization.

[0296] Furthermore, the secondary battery 300 has a structure that allows the area remaining on the outer surface 310a of the battery housing 305, excluding the area occupied by the positive terminal 315, to be used as the positive terminal and negative terminal, respectively. In other words, it has a structure that allows almost the entire surface opposite the open portion of the battery housing 305 to be used as the negative terminal. This has the advantage of providing a sufficient area for welding connecting components such as busbars for electrical wiring.

[0297] The positive terminal 315 can increase the space efficiency within the battery housing 305. Therefore, the internal resistance of the secondary battery 300 containing it can be reduced, increasing its energy density. The positive terminal 315 may be improved to enlarge the cross-sectional area of ​​the current path. This improves the internal heat generation problem that occurs during rapid charging in the secondary battery 300 containing it.

[0298] The positive terminal 315 may include a main body portion 315a inserted into the through hole 320, an external flange portion 315b extending along the outer surface 310a from one peripheral edge of the main body portion 315a exposed on the outer surface 310a of the bottom portion 310 of the battery housing 305, an internal flange portion 315c extending toward the inner surface 310b from the other peripheral edge of the main body portion 315a exposed on the inner surface 310b of the bottom portion 310 of the battery housing 305, and a flat portion 315d provided inside the internal flange portion 315c.

[0299] Preferably, at least a portion of the positive electrode current collector plate 330 may be laser-welded to the flat portion 315d of the positive electrode terminal 315. Preferably, the flat portion 315d and the inner surface 310b of the bottom portion 310 of the battery housing 305 may be parallel to each other. Here, “parallel” means substantially parallel when observed visually.

[0300] The diameter of the flat portion 315d can be between 3 mm and 14 mm. The flat portion 315d can determine the size of the weldable area. If the diameter of the weldable area is less than 3 mm, it may be difficult to ensure adequate welding strength. If the diameter of the weldable area exceeds 14 mm, the diameter of the outer flange portion 315b of the positive terminal 315 is too large, making it difficult to secure sufficient area on the outer surface 310a of the bottom portion 310 of the battery housing 305 used as the negative terminal.

[0301] Laser welding is used to connect the flat portion 315d to the positive electrode current collector plate 330. Laser welding can be performed with the electrode assembly 200 inserted through the opening of the battery housing 305 and the opening of the battery housing 305 open. During laser welding, the laser beam can reach the welding area of ​​the positive electrode current collector plate 330 through the cavity present in the core C of the electrode assembly 200. When the positive electrode current collector plate 330 is welded to the flat portion 315d of the positive electrode terminal 315, the positive electrode terminal 315 can support the welding area of ​​the positive electrode current collector plate 330. Also, because the flat portion 315d of the positive electrode terminal 315 has a large area, a large welding area can be secured. This reduces the contact resistance of the welding area, thereby reducing the internal resistance of the secondary battery 300. The face-to-face welding structure of the riveted positive electrode terminal 315 and the positive electrode current collector plate 330 is very useful for rapid charging. This is because it is possible to lower the current density per unit area in the cross-section in the direction of current flow, thereby reducing the amount of heat generated in the current path compared to conventional methods.

[0302] Furthermore, a secondary battery 300 to which a riveted structure is applied to the positive terminal 315 allows for unidirectional electrical wiring. In the secondary battery 300, the cap plate 340 of the encapsulant 335 does not have polarity. Instead, since the negative current collector plate 365 is connected to the battery housing 305, the outer surface 310a of the bottom 310 of the battery housing 305 has opposite polarity to the positive terminal 315. This simplifies the connection structure when connecting multiple secondary batteries 300, as both the positive and negative terminals can be connected in one direction. As a result, when attempting to connect multiple secondary batteries 300 in series and / or parallel for the manufacture of a battery pack, wiring such as busbar connections can be performed on the top of the secondary batteries 300 using the outer surface 310a of the bottom 310 of the battery housing 305 and the positive terminal 315. This increases the number of secondary batteries that can be mounted in the same space, improves energy density, and facilitates electrical wiring work. Therefore, due to its good spatial efficiency and high electrical wiring efficiency, it significantly improves work efficiency during the assembly process of electric vehicles, as well as during the assembly and maintenance of battery packs.

[0303] Furthermore, since the electrical wiring is performed on the side where the positive terminal 315 is located and the outer surface 310a of the bottom 310 of the battery housing 305, and electrical wiring does not need to be provided on the cap plate 340 located on the opposite side, the effect of the vent notch 350 formed in the cap plate 340 can be maximized. In addition, by arranging a heat sink, cooling plate, or tray on the cap plate 340 side, the purposes of assembly and cooling can be effectively achieved regardless of the electrical wiring connection points. Also, by assembling the battery so that the vent notch 350 is located at the bottom, the gas discharged from inside the secondary battery will be discharged downwards. Normally, secondary batteries are mounted lower than the occupants of vehicles such as EVs, so if gas is discharged upwards from the secondary battery, there is a risk of harm to the occupants. However, the secondary battery 300 of the present invention is not only capable of effectively releasing the high-pressure gas inside the secondary battery, but is also safe regardless of the electrical wiring connection point at the top, and furthermore, when the vent notch 350 is ruptured and the gas is released downwards, it does not harm the occupants and thus safety is greatly improved.

[0304] The secondary battery 300 may further include an insulator 370 interposed between the closing portion of the battery housing 305 and the positive electrode current collector plate 330. The insulator 370 may be interposed between the positive electrode current collector plate 330 and the inner surface 310b of the bottom portion 310 of the battery housing 305, and between the inner circumferential surface 305a of the side wall of the battery housing 305 and the electrode assembly 200.

[0305] Preferably, the insulator 370 may include a welding hole 370a that exposes the flat portion 315d of the positive electrode terminal 315 to the positive electrode current collector plate 330. The welding hole 370a may also expose the internal flange portion 315c and the internal gasket 325b along with the flat portion 315d of the electrode terminal. Preferably, the welding hole 370a does not obstruct the cavity of the core C. This does not hinder the movement of gas that would otherwise try to move towards the cap plate 340 through the cavity of the core C if a large amount of gas is generated due to a malfunction in the secondary battery. Therefore, when a large amount of gas is generated, the internal pressure control action of the vent notch 350 can be made smoother. In addition, by including the welding hole 370a in the cap plate 340, the laser beam is allowed to pass through when the positive electrode current collector plate 330 is welded to the positive electrode terminal 315, so that the laser beam reaches the positive electrode current collector plate 330.

[0306] Preferably, the insulator 370 can cover at least the surface of the positive electrode current collector plate 330 and one side (upper) end of the electrode assembly 200. This prevents the positive electrode current collector plate 330 and the uncoated positive electrode portion 143a, which have different polarities from the battery housing 305, from coming into contact with each other.

[0307] Preferably, the insulator 370 is made of an insulating resin and may include an upper plate 370b and a side sleeve 370c. For example, the upper plate 370b and the side sleeve 370c may be a single injection-molded product. Alternatively, the side sleeve 370c can be replaced with insulating tape or the like. The insulating tape may cover the outer edge of the positive electrode current collector plate 330 together with the uncoated positive electrode portion 143a exposed on the outer circumferential surface of the electrode assembly 200.

[0308] Preferably, the insulator 370 and the inner surface 310b of the bottom 310 of the battery housing 305 can be in close contact with each other. Here, "close contact" means that there is no visible space (gap). In order to eliminate the space (gap), the distance from the inner surface 310b of the bottom 310 of the battery housing 305 to the flat portion 315d of the positive terminal 315 may be the same as or slightly smaller than the thickness of the insulator 370.

[0309] On the other hand, Figure 24 shows the path (first path) from the welding position of the module busbar to the electrode tabs of each electrode 140, namely the uncoated positive electrode portion 143a and the uncoated negative electrode portion 143b (current starting points are indicated by ●, and connection points by ▲). The current starting points are located at the positive electrode terminal 315 and the negative electrode terminal. The negative electrode terminal is the battery housing 305. The module busbar welding position is located at the upper end of the secondary battery 300. A current path is formed starting from the positive electrode terminal 315 and connecting to the uncoated positive electrode portion 143a, and a current path is formed starting from the negative electrode terminal and connecting to the uncoated negative electrode portion 143b.

[0310] Compared to the conventional cylindrical secondary battery shown in Figure 2, the first path is similar to the first path, but the second path in the electrode 140 constituting the electrode assembly 200 has a significant difference from the conventional second path described with reference to Figure 3 and the hypothetical second path described with reference to Figure 8, as also shown in Figure 15, and the ratio of the current path L2 / L1 is set to 11 or less, and for this purpose the length of the undefined section of the electrode tab, for example, the length d of the first part B1 B1 A key feature of this invention is setting a range.

[0311] In the present invention, unlike the conventional electrode structure described with reference to Figures 1 to 3, when viewed from the unfolded state before winding the electrode, an electrode tab consisting of an uncoated portion is formed on the long side of the electrode, thereby preventing the current from moving along the longitudinal direction of the electrode and causing it to move along the width direction, thereby minimizing the current path and reducing resistance. Furthermore, by setting a portion of the uncoated portion as an electrode tab undefined portion, deformation does not occur when bending the welded area of ​​the uncoated portion, and the cavity present in the core of the electrode assembly does not become blocked. In addition, when manufacturing a jelly roll type electrode assembly and a cylindrical secondary battery containing the same using an electrode with such a structure, the length of the electrode tab undefined portion or the spacing between adjacent segmented pieces is adjusted so that the ratio of the current path in the maximum current path L2 / L1 is 11 or less, as described above.

[0312] The cylindrical secondary battery according to the above-described embodiment (modified version) can be used to manufacture a battery pack.

[0313] Figure 25 is a schematic diagram showing the configuration of a battery pack according to an embodiment of the present invention.

[0314] Referring to Figure 25, the battery pack 400 according to an embodiment of the present invention includes an assembly to which a secondary battery 401 is electrically connected and a pack housing 402 that houses it. The secondary battery 401 may be any of the secondary batteries according to the embodiments (modifications) described above. For convenience of illustration, the drawings omit the depiction of components such as busbars for the electrical connection of the secondary battery 401, cooling units, and external terminals.

[0315] The battery pack 400 can be installed in an automobile. The automobile may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The automobile may include four-wheeled or two-wheeled vehicles.

[0316] Figure 26 is a diagram illustrating an automobile including the battery pack 400 shown in Figure 25.

[0317] Referring to Figure 26, an automobile V according to one embodiment of the present invention includes a battery pack 400 according to one embodiment of the present invention. The automobile V operates by receiving power from the battery pack 400 according to one embodiment of the present invention.

[0318] Although the present invention has been described above with reference to limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and that various modifications and variations are possible within the equivalent scope of the technical concept and claims of the present invention by persons with ordinary skill in the art to which the present invention pertains. [Explanation of symbols]

[0319] 100, 200 electrode assembly 140, 150, 160, 170, 180 electrodes 141 Current collector 142 Active material layer 143 Uncoated parts 143a Positive electrode uncoated portion 143b Negative electrode uncoated section 161, 161' segmental piece 164 Segment Omission Section 166 Independent Area 300, 401 Secondary battery 305 Battery Housing 315 Positive terminal 330 Positive electrode current collector plate 335 Sealing body 340 Cap Plate 345 Sealing gasket 365 Negative electrode current collector plate 400 Battery Pack

Claims

1. An electrode assembly in which a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode are wound around a winding shaft to define a core and an outer surface, The electrode which is the positive electrode or the negative electrode is a sheet-like current collector having a long side and a short side, and includes a current collector with an uncoated portion at the end of the long side. The uncoated portion includes an electrode tab defined section used as an electrode tab and at least one electrode tab undefined section that is not used as an electrode tab. The maximum current path for at least one undefined electrode tab section includes a current path in the width direction along the short side of the current collector and a current path in the longitudinal direction along the long side of the current collector, and when the lengths of the current path in the width direction and the current path in the longitudinal direction are L1 and L2, respectively, the ratio of the current paths L2 / L1 is 11 or less. The ratio L2 / L1 of the current path is 2 to 5. The uncoated portion includes a first portion adjacent to the core, a second portion adjacent to the outer circumferential surface, and a third portion between the first and second portions. An electrode assembly characterized in that the first portion has a smaller height than the third portion in the winding axis direction.

2. The electrode assembly according to claim 1, characterized in that the undefined electrode tab section has a smaller height than the defined electrode tab section.

3. The electrode assembly according to claim 1, characterized in that the maximum length of the undefined section of the electrode tab is 4% to 23% of the lengths of the positive electrode and the negative electrode.

4. The electrode assembly according to claim 1, characterized in that the maximum length of the undefined section of the electrode tab is 2.5 to 11 times the width of the positive electrode and the negative electrode.

5. The electrode assembly according to claim 1, characterized in that the third portion is defined as an electrode tab when bent along the radial direction of the electrode assembly.

6. The electrode assembly according to claim 1, characterized in that the second portion is the same height as or smaller than the third portion in the winding axis direction.

7. The electrode assembly according to claim 6, characterized in that the second and third portions are defined as electrode tabs when bent along the radial direction of the electrode assembly.

8. The electrode assembly according to claim 1, characterized in that the length of the short side of the current collector is 60 mm to 85 mm, and the length of the long side of the current collector is 3 m to 5 m.

9. The electrode assembly according to claim 8, characterized in that the maximum length along the long side of the current collector in the first portion is 4% to 23% of the length of the long side of the current collector.

10. The electrode assembly according to claim 8, characterized in that the length along the long side of the current collector in the first portion is 660 mm or less.

11. The electrode assembly according to claim 1, characterized in that the first portion corresponds to the undefined section of the electrode tab.

12. The electrode assembly according to claim 1, characterized in that the first portion is not bent along the radial direction of the electrode assembly.

13. The electrode assembly according to claim 1, characterized in that the second portion is not bent along the radial direction of the electrode assembly.

14. The electrode assembly according to claim 1, characterized in that the length of the third portion is longer than the length of the first portion and the length of the second portion in the winding direction of the electrode assembly.

15. The electrode assembly according to claim 1, characterized in that the first portion starts from the short side on the core side of the current collector, the height of the first portion is constant along the winding direction, and the first portion is not bent along the radial direction of the electrode assembly.

16. The electrode assembly according to claim 1, characterized in that at least a portion of the third portion is divided into a plurality of independently foldable segmented pieces.

17. The electrode assembly according to claim 16, characterized in that the segmented pieces are bent and overlapped in the direction of the winding axis.

18. The electrode assembly according to claim 16, characterized in that the length of the short side of the current collector is 60 mm to 85 mm, the length of the long side of the current collector is 3 m to 5 m, the thickness of the current collector is 5 μm to 25 μm, the width of the segmented piece is 10 mm or less, and the height of the segmented piece is 10 mm or less.

19. The electrode assembly according to claim 18, characterized in that the length along the long side of the current collector in the first part is 660 mm or less.

20. The electrode assembly according to claim 16, characterized in that the electrode assembly includes, sequentially along the radial direction with respect to the cross-section in the winding axis direction, sections where no segmental pieces are present and sections where the height of the segmental pieces is uniform, wherein the plurality of segmental pieces are arranged in the sections where the height is uniform and are bent along the radial direction of the electrode assembly to form a bent surface region.

21. The electrode assembly according to claim 20, characterized in that the electrode assembly further includes a height-variable section between the segment-omitted section and the height-uniform section in which the height of the segment-like segments is variable, and the plurality of segment-like segments are arranged in the height-variable section and the height-uniform section and are bent along the radial direction of the electrode assembly to form a bent surface region.

22. The electrode assembly according to claim 20, characterized in that the segment omitted section corresponds to the electrode tab undefined section.

23. The electrode assembly according to claim 20, characterized in that the second portion is not divided into segmented pieces, and the height of the first portion and the height of the second portion are the same.

24. The electrode assembly according to claim 16, characterized in that the third portion includes one or more segments without segments along the winding direction of the electrode assembly.

25. The electrode assembly according to claim 24, characterized in that the height of the uncoated portion in the segmented portion omitted section is the same as the height of the first portion.

26. The electrode assembly according to claim 24, characterized in that the segmented pieces are located in two or more sector-shaped or polygonal regions arranged circumferentially with respect to the core.

27. The electrode assembly according to claim 24, characterized in that the segment omitted section corresponds to the electrode tab undefined section.

28. The electrode assembly according to claim 1, characterized in that the core is provided with a cavity, the third portion is defined as an electrode tab when bent along the radial direction of the electrode assembly, the third portion is divided into a plurality of independently bendable segmental pieces, and the bent segmental pieces do not obstruct the cavity.

29. The electrode assembly according to claim 28, characterized in that, in the first part, the maximum length along the long side of the current collector is 4% to 23% of the length of the long side of the current collector.

30. An electrode assembly according to any one of claims 1 to 29, A cylindrical battery housing, which houses the electrode assembly through an open portion formed on one side and is connected to the uncoated portion of the negative electrode, A sealing body that seals the open portion of the cylindrical battery housing so as to be insulated from the cylindrical battery housing, A positive electrode terminal is riveted through a through hole formed in the bottom of the cylindrical battery housing, located on the opposite side of the opening of the cylindrical battery housing, and connected to the uncoated portion of the positive electrode. A secondary battery characterized by containing [something].

31. The uncoated portion of the positive electrode is exposed to the outside of the separation membrane, and the uncoated portion of the negative electrode is exposed to the outside of the separation membrane in the opposite direction to the uncoated portion of the positive electrode. The secondary battery according to claim 30, further comprising a positive electrode current collector plate electrically connected to the uncoated portion of the positive electrode and a negative electrode current collector plate electrically connected to the uncoated portion of the negative electrode.

32. The secondary battery according to claim 30, characterized in that the DC resistance of the secondary battery is 4 mΩ or less and the AC resistance is 3 mΩ or less.

33. The secondary battery according to claim 30, characterized in that the AC resistance of the secondary battery is 2 mΩ or less.

34. The secondary battery according to claim 30, characterized in that the ratio of the diameter to the height is greater than 0.

4.

35. The secondary battery according to claim 30, characterized in that the sealing body includes a non-polar cap plate and a sealing gasket interposed between the peripheral edge of the cap plate and the open portion of the cylindrical battery housing.

36. The aforementioned positive terminal is The main body portion inserted into the aforementioned through hole, An external flange portion extending along the outer surface from one peripheral edge of the main body portion exposed on the outer surface of the bottom of the cylindrical battery housing, An internal flange portion extending toward the inner surface from the other peripheral edge of the main body portion exposed on the inner surface of the bottom of the cylindrical battery housing, A flat portion provided on the inside of the aforementioned internal flange portion, A secondary battery according to claim 30, characterized by including the following:

37. The secondary battery further includes a positive electrode current collector plate electrically connected to the uncoated portion of the positive electrode and a negative electrode current collector plate electrically connected to the uncoated portion of the negative electrode, The secondary battery according to claim 36, characterized in that the positive electrode terminal is joined to the positive electrode current collector plate by laser welding in the flat portion.

38. The secondary battery according to claim 31, characterized in that the undefined electrode tab section is a portion where no current path is formed because it is not connected to the negative electrode current collector plate and the positive electrode current collector plate.

39. A battery pack characterized by including a plurality of secondary batteries as described in claim 30.

40. The battery pack according to claim 39, characterized in that a plurality of secondary batteries are arranged in a predetermined number of rows, and the positive terminal of each secondary battery and the outer surface of the bottom of the battery housing are positioned to face upward.

41. An automobile comprising at least one battery pack as described in claim 39.

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