Electrode assembly, and secondary battery, battery pack, and vehicle including the same

Abstract

The present specification relates to an electrode assembly in which a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode are laminated and wound up, and a secondary battery, a battery pack, and a transportation means including the same.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0184825, filed with the Korean Intellectual Property Office on December 26, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present specification relates to an electrode assembly in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are stacked and wound up, and a secondary battery, a battery pack, and a vehicle including the same. [Background technology]

[0003] In the case of cylindrical batteries, a jelly roll-type electrode assembly is manufactured by winding a long electrode with a predetermined width into a roll. A cylindrical battery manufactured by inserting such a jelly roll-type electrode assembly into a battery case undergoes repeated contraction and expansion of the electrode during charging and discharging. In particular, if a tab is located in the core of the jelly roll-type electrode assembly or if a silicon-based active material is added to the negative electrode, which increases the degree of contraction and expansion of the electrode assembly, the pressure acting on the winding core of the electrode assembly increases significantly.

[0004] Recently, as low resistance / high capacity designs have become more common, jelly roll-type electrode assemblies have increasingly included multiple tabs or silicon-based active materials, which increases the possibility of deformation of the electrode assembly located on the core side due to contraction / expansion of the electrode assembly. In particular, if the separator located between the negative and positive electrodes is damaged, the negative and positive electrodes may come into direct contact, resulting in an internal short circuit, which can cause heat generation and fire.

[0005] In order to solve the problems of separator damage and internal short circuiting caused by deformation of the electrode assembly, it is currently necessary to develop a technology that can protect the positive electrode and separator in the corresponding area and suppress the occurrence of internal short circuiting. Summary of the Invention [Problem to be solved by the invention]

[0006] The present specification provides an electrode assembly in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are stacked and wound up, and a secondary battery, a battery pack, and a transportation means including the same. [Means for solving the problem]

[0007] One embodiment of the present specification provides an electrode assembly in which a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode are stacked and wound up, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode includes a negative electrode holding portion in which the negative electrode active material layer is provided on the negative electrode current collector, and a negative electrode uncoated portion at one end of the negative electrode current collector on the winding core side where the negative electrode active material layer is not provided, wherein the separator and the negative electrode extend further beyond the longitudinal end of the positive electrode on the winding core side of the electrode assembly and are further wound up, and the distance between the winding start point of the negative electrode holding portion and the winding start point of the positive electrode in the winding direction from the winding core of the electrode assembly is equal to or greater than two winding lengths.

[0008] Another embodiment of the present specification provides an electrode assembly in which a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode are stacked and wound up, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode includes a negative electrode holding portion in which the negative electrode active material layer is provided on the negative electrode current collector, and a negative electrode uncoated portion in which the negative electrode active material layer is not provided at one end of the negative electrode current collector on the winding core side, wherein the separator and the negative electrode extend beyond the winding start portion of the positive electrode on the winding core side of the electrode assembly and are further wound up, and in at least one cross section of the electrode assembly perpendicular to the winding core axis, a straight line connecting the winding core to the winding start portion of the positive electrode passes through the negative electrode holding portion two or more times.

[0009] In another embodiment of the present specification, the battery may further include a negative electrode tab provided on the negative electrode uncoated portion.

[0010] In another embodiment of the present specification, the battery may further include an adhesive tape provided on the negative electrode tab and the negative electrode current collector positioned around the negative electrode tab. The adhesive tape may be provided to extend to a winding start portion of the negative electrode holder.

[0011] In another embodiment of the present specification, the negative electrode current collector may further include an additional adhesive tape provided on a surface opposite to the surface on which the negative electrode tab is provided, facing the adhesive tape. The additional adhesive tape may be provided to extend to a winding start portion of the negative electrode holder.

[0012] In still another embodiment of the present specification, in at least one cross section perpendicular to the winding core axis of the electrode assembly, the winding core of the electrode assembly may be centered on any circle having a radius equal to the distance from the center of the circle to the winding start portion of the positive electrode, and the central angle of a minor arc formed from a point where a line extending from the winding start portion of the negative electrode tab to any point around the circle forms a right angle with a tangent to the circle to the winding start portion of the positive electrode may be 90° or less. Specifically, the central angle of the minor arc formed from the contact point to the winding start portion of the positive electrode may be 90° or less, 85° or less, 80° or less, 75° or less, 70° or less, 65° or less, 60° or less, 55° or less, 50° or less, 45° or less, 40° or less, 35° or less, 30° or less, 25° or less, 20° or less, 15° or less, 10° or less, or 5° or less, or may be 0° or more, more than 0°, 1° or more, 2° or more, 3° or more, or 4° or more.

[0013] In another embodiment of the present specification, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode includes a positive electrode uncoated portion where the positive electrode active material layer is not provided, a positive electrode tab is provided on the positive electrode uncoated portion, and a central angle of an arc formed on the arbitrary circle from a contact point where a line extending from a winding start portion of the positive electrode tab to an arbitrary point around the arbitrary circle forms a right angle with a tangent to the arbitrary circle to the winding start portion of the positive electrode may be more than 90° and not more than 180°.

[0014] In another embodiment of the present specification, the positive electrode may include a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode may include two positive electrode holding portions spaced apart from each other and a positive electrode uncoated portion provided between the two positive electrode holding portions, and a positive electrode tab may be provided on the positive electrode uncoated portion.

[0015] In another embodiment of the present specification, the negative electrode may further include an additional negative electrode uncoated portion at one end of an outer corner of the negative electrode current collector where the negative electrode active material layer is not provided, and an additional negative electrode tab may be provided on the additional negative electrode uncoated portion.

[0016] In another embodiment of the present specification, the positive electrode includes a positive electrode current collector and positive electrode active material layers provided on both surfaces of the positive electrode current collector, and the positive electrode active material layers provided on both surfaces of the positive electrode current collector may have the same or different winding start portions, and preferably may have the same winding start portions.

[0017] In another embodiment of the present specification, the positive electrode includes a positive electrode active material layer provided on both sides of the positive electrode current collector, and the positive electrode active material layers provided on both sides of the positive electrode current collector may have the same or different winding end points, preferably the same.

[0018] In another embodiment of the present specification, the length of the negative electrode tab may be 2 mm or more and 5 mm or less in the winding direction.

[0019] In another embodiment of the present specification, the separator may include a first separator and a second separator, and the electrode assembly may be formed by sequentially stacking the negative electrode, the first separator, the positive electrode, and the second separator and winding them up.

[0020] In another embodiment of the present specification, the negative electrode may be wound so as to be positioned at the outermost corner.

[0021] Another embodiment of the present specification provides a secondary battery including the electrode assembly described above and a battery case for housing the electrode assembly. The electrode assembly may have a vertical cross section of a core axis that is circular, and the battery case may be cylindrical.

[0022] Another embodiment herein provides a battery pack including two or more of the secondary batteries described above.

[0023] Another embodiment of the present disclosure provides a vehicle including the battery pack described above. The vehicle may be any vehicle used to move cargo, people, or perform work while moving, such as a bicycle, heavy machinery, agricultural equipment, automobile, bus, or airplane. [Effects of the Invention]

[0024] In an electrode assembly according to one embodiment of the present specification, by arranging the negative electrode holding part two or more turns closer to the core than the positive electrode winding start part, it is possible to prevent the positive electrode end from slipping during battery charge and discharge.

[0025] In an electrode assembly according to one embodiment of the present specification, the negative electrode tab is disposed behind the positive electrode winding start portion in the positive electrode winding direction, thereby preventing the positive electrode end from slipping during battery charge and discharge.

[0026] By providing an electrode assembly according to another embodiment of the present disclosure, damage to the separator due to deformation of the electrode assembly caused by contraction / expansion of the electrodes during charging / discharging of the battery can be prevented, and internal short circuits between the electrodes can be prevented, thereby improving the stability and lifespan of the battery.

[0027] In an electrode assembly according to another embodiment of the present specification, the negative electrode tab is disposed behind the positive electrode winding start portion in the positive electrode winding direction, thereby enabling the shape of the winding core to be well maintained during battery charge and discharge. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 2 is a perspective view of a wound electrode stack. [Figure 2] 1 illustrates a winding process for an electrode stack according to one embodiment of the present disclosure. [Figure 3] FIG. 2 is a plan view of an electrode stack wound in accordance with one embodiment of the present disclosure. [Figure 4] A plan view of the wound electrode laminate and an arbitrary circle having a radius equal to the distance from the center of the circle to the longitudinal end of the positive electrode based on the plan view are shown. [Figure 5] FIG. 2 is a vertical cross-sectional view of a secondary battery housed in a battery case that houses a wound electrode stack. [Figure 6] 1 is a diagram illustrating a schematic configuration of a battery pack according to an embodiment of the present invention; [Figure 7] FIG. 7 is a diagram for explaining a vehicle including the battery pack of FIG. 6. [Figure 8] 1(b) and Comparative Example 1(a) show an additionally wound negative electrode holding portion in CT images after the batteries are operated. [Figure 9] 1 shows the number of passes of the negative electrode holder in CT images of Example 1(b) and Comparative Example (a) after the batteries are operated. [Figure 10] 1(b) and Comparative Example 1(a) show deformation diagrams in CT images after battery operation. [Figure 11] 10 shows how the tape attached to the negative electrode tab on the winding core side in Example 2(a) and Example 3(b) is provided. [Figure 12] 10 shows CT images of Example 2(a) and Example 3(b) after battery operation. [Figure 13] FIG. 10 is a diagram showing the positioning of the positive electrode winding start part in the embodiment. [Figure 14] This shows a method for checking the degree of deformation of the negative electrode on the winding core side after battery operation using CT images. [Explanation of symbols]

[0029] 1...electrode assembly 10 ···Core 1b: outermost angle 1c...Internal 110...Negative electrode 111...Negative electrode current collector 112...first negative electrode active material layer 113...Second negative electrode active material layer 114 Negative electrode uncoated area 116 Negative electrode tab 120...Positive electrode 121...Positive electrode current collector 122...first positive electrode active material layer 123...Second positive electrode active material layer 131...1st separation membrane 132...Second separation membrane 140 Tape 145 Additional Tape 20...Secondary battery 21 cans 22 Cap assembly 200 battery pack 201 Cylindrical battery cells 202 Pack Housing V...Automotive DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrative purposes only and the scope of the present invention is not limited by the drawings.

[0031] 1 is a perspective view of a wound electrode stack. First, a positive electrode 120, a negative electrode 110, and separators 131 and 132 disposed between the positive electrode 120 and the negative electrode 110 may be stacked. The separator may include two separators. As shown in FIG. 1, a first separator 131 may be disposed between the negative electrode 110 and the positive electrode 120, and an additional second separator 132 may be disposed on the surface of the positive electrode 120 opposite the surface that contacts the first separator 131. Specifically, the second separator 132, the positive electrode 120, the first separator 131, and the negative electrode 110 may be stacked in order.

[0032] In the winding direction, the second separator 132, the positive electrode 120, the first separator 131, and the negative electrode 110 may be stacked in order and wound on the negative electrode 110 side. When wound in this manner, the separator may be exposed at the outermost corner 1b of the wound electrode assembly.

[0033] If necessary, the electrode assembly may be wound in the opposite direction to the above-described winding direction, toward the positive electrode 120, as shown in FIG. 2. When wound in this manner, the negative electrode 110, or both the negative electrode 110 and the separator (first separator 131, second separator 132) may be exposed at the outermost corner 1b of the wound electrode assembly. In this case, when the negative electrode is exposed at the outermost corner 1b, only the negative electrode uncoated portion (negative electrode uncoated portion 114) on the outer corner where no negative electrode active material layer is provided may be exposed, or both the negative electrode uncoated portion on the outer corner and the negative electrode support portion on the outer corner may be exposed at the outermost corner 1b.

[0034] The interior 1c of the wound electrode assembly 1 shown in Figure 1 refers to the area of the wound electrode assembly excluding the outermost corner 1b. In this case, if the wound electrode assembly is a pillar, the outermost corner 1b refers to the side exposed to the outside, and the interior 1c includes the entire inner area of the pillar excluding the side.

[0035] It can also be seen that the length of one winding of the electrode assembly 1 from the winding core 10 gradually increases up to the outer angle (outermost angle 1b). Specifically, the winding length for one winding from the winding core 10 to the outer angle 1b, and the circumference of the wound electrode assembly 1, gradually increase. From the winding start point on the winding core 10, the first winding length (1 turn), the second winding length (2 turns), the third winding length (3 turns), etc. can continue sequentially up to the outer angle (outermost angle 1b).

[0036] The stacked electrode assembly 1 shown in FIG. 2 can be wound up to produce a wound roll having a plan view as shown in FIG.

[0037] The positive electrode 120 and the negative electrode 110 may each include a current collector and an active material layer provided on at least one surface of the current collector.

[0038] The positive electrode 120 may include a positive electrode current collector 121 and positive electrode active material layers 122 and 123 provided on at least one surface of the positive electrode current collector 121. The positive electrode active material layers 122 and 123 may be provided on both surfaces of the positive electrode current collector 121, or may include a first positive electrode active material layer 122 provided on one surface of the positive electrode current collector 121 and a second positive electrode active material layer 123 provided on the surface opposite to the surface on which the first positive electrode active material layer 122 is provided.

[0039] The positive electrode 120 includes one or more positive electrode tabs, and the positive electrode tabs are located in positive electrode uncoated portions where the positive electrode active material layers (first positive electrode active material layer 122, second positive electrode active material layer 123) are not provided.

[0040] In one embodiment, the positive electrode 120 may include a positive electrode holder in which a positive electrode active material layer is provided on the positive electrode current collector 121, and a positive electrode uncoated portion in which no positive electrode active material layer is provided at one or both end portions of the positive electrode current collector 121. In this case, the positive electrode tab may be located in the positive electrode uncoated portion located at one or both end portions of the positive electrode current collector 121, preferably at one end portion.

[0041] In another embodiment, the positive electrode 120 may include a positive electrode uncoated portion at an outer corner end of the positive electrode current collector 121 where a positive electrode active material layer is not provided, and a positive electrode tab may be formed on the positive electrode uncoated portion.

[0042] In another embodiment, the positive electrode 120 may include two or more positive electrode holders spaced apart in the longitudinal direction on the positive electrode current collector 121, each having a positive electrode active material layer thereon, and a positive electrode uncoated portion between the two or more positive electrode holders, where no positive electrode active material layer is provided. In this case, the positive electrode tab may be located in the positive electrode uncoated portion between the two or more positive electrode holders, preferably in the positive electrode uncoated portion located between two positive electrode holders. In this case, both end portions of the positive electrode 120 may be formed as free edges without a positive electrode uncoated portion.

[0043] The positive electrode 120 may include a positive electrode current collector 121 and positive electrode active material layers 122, 123 provided on both sides of the positive electrode current collector 121, and the first positive electrode active material layer 122 provided on one side of the positive electrode current collector 121 and the second positive electrode active material layer 123 provided on the other side may have the same or different lengths.

[0044] In another embodiment of the present specification, the positive electrode 120 includes a positive electrode current collector 121 and positive electrode active material layers (a first positive electrode active material layer 122, a second positive electrode active material layer 123) provided on both sides of the positive electrode current collector 121, and the positive electrode active material layers (the first positive electrode active material layer 122, the second positive electrode active material layer 123) provided on both sides of the positive electrode current collector 121 may have the same winding start position.

[0045] In another embodiment of the present specification, the positive electrode 120 includes positive electrode active material layers (first positive electrode active material layer 122, second positive electrode active material layer 123) provided on both sides of the positive electrode current collector 121, and the positive electrode active material layers (first positive electrode active material layer 122, second positive electrode active material layer 123) provided on both sides of the positive electrode current collector 121 may have the same winding end portion.

[0046] The negative electrode 110 may include a negative electrode current collector 111 and negative electrode active material layers 112 and 113 provided on at least one surface of the negative electrode current collector 111. The negative electrode active material layers 112 and 113 may be provided on both surfaces of the negative electrode current collector 111, or may include a first negative electrode active material layer 112 provided on one surface of the negative electrode current collector 111 and a second negative electrode active material layer 113 provided on the surface opposite to the surface on which the first negative electrode active material layer 112 is provided.

[0047] The negative electrode 110 includes one or more negative electrode tabs 116, and the negative electrode tabs 116 are located in negative electrode uncoated portions where the negative electrode active material layers (first negative electrode active material layer 112, second negative electrode active material layer 113) are not provided.

[0048] In one embodiment, the negative electrode 110 may include a negative electrode holder in which a negative electrode active material layer is provided on the negative electrode current collector 111, and a negative electrode uncoated portion in which no negative electrode active material layer is provided at one or both end portions of the negative electrode current collector 111. In this case, the negative electrode tab 116 may be located in the negative electrode uncoated portion located at one or both end portions of the negative electrode current collector 111, preferably in the negative electrode uncoated portions at both end portions.

[0049] In another embodiment, the negative electrode 110 may include a negative electrode uncoated portion where the active material layer is not provided at the end of the negative electrode current collector 111 on the winding core side, and a negative electrode tab 116 may be formed on the negative electrode uncoated portion.

[0050] The negative electrode 110 may include a negative electrode current collector 111 and negative electrode active material layers 112 and 113 provided on both sides of the negative electrode current collector 111. The first negative electrode active material layer 112 provided on one side of the negative electrode current collector 111 and the second negative electrode active material layer 113 provided on the other side may have the same or different lengths.

[0051] In another embodiment, the positive electrode 120 may include two positive electrode holding portions spaced apart in the winding direction of the electrode assembly 1 and having the positive electrode active material layers (first positive electrode active material layer 122 and second positive electrode active material layer 123) provided on the positive electrode current collector 121; and a positive electrode uncoated portion between the two holding portions where the positive electrode active material layer is not provided on the positive electrode current collector 121, and one positive electrode tab may be formed on the positive electrode uncoated portion. The negative electrode 110 may include two negative electrode uncoated portions at both side ends of the negative electrode current collector 111 where the negative electrode active material layer is not provided, and one negative electrode tab 116 may be formed on each of the two negative electrode uncoated portions.

[0052] In one embodiment of the present specification, an electrode assembly is provided in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are stacked and wound up. The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode includes a negative electrode holder in which the negative electrode active material layer is disposed on the negative electrode current collector, and a negative electrode uncoated portion at one end of the negative electrode current collector facing the winding core where the negative electrode active material layer is not disposed. On the winding core side of the electrode assembly, the separator and the negative electrode extend beyond the longitudinal end of the positive electrode facing the winding core and are further wound up. In at least one cross section perpendicular to the winding core axis of the electrode assembly, a straight line connecting the winding core to the winding start portion of the positive electrode may pass through the negative electrode holder two or more times. Alternatively, a straight line connecting the winding core to the winding start portion of the positive electrode may pass through the negative electrode holder two or more times, three or more times, four or more times, or five or more times. The more negative electrode holding parts a straight line connecting the winding core to the winding start part of the positive electrode passes through, the greater the internal rigidity of the winding core part that suppresses movement and slippage of the winding start part of the positive electrode.

[0053] In this case, the thickness of the negative electrode uncoated portion is the thickness without the negative electrode active material layer, and is the thickness of only the negative electrode current collector, but the thickness of the negative electrode holding portion is the sum of the thicknesses of the negative electrode current collector and the negative electrode active material layer provided on at least one surface thereof, and is therefore 5 to 15 times the thickness of the negative electrode uncoated portion. When the negative electrode holding portion has negative electrode active material layers on both surfaces of the negative electrode current collector, the thickness is 9 to 15 times the thickness of the negative electrode uncoated portion. Therefore, the internal rigidity of the winding core side can be increased more rapidly by further winding the relatively thick negative electrode holding portion than by further winding up the negative electrode uncoated portion before the positive electrode is wound.

[0054] In yet another embodiment of the present specification, there is provided an electrode assembly in which the distance between the winding start portion of the negative electrode holder and the winding start portion of the positive electrode in the winding direction from the winding core of the electrode assembly is equal to or greater than two winding lengths. The longer the distance between the winding start portion of the negative electrode holder and the winding start portion of the positive electrode, the longer the length of the negative electrode holder that does not correspond to the positive electrode holder on the winding core side, and the more times the negative electrode holder that does not correspond to the positive electrode holder on the winding core side is wound around the winding core side, the greater the internal rigidity of the winding core side.

[0055] In this specification, the winding start portion can be expressed as a single point, namely, a winding start point.

[0056] In this specification, the winding core 10, which is the winding device in FIG. 2, is removed after winding is completed in FIG. 3, and the winding core 10 in FIG. 3 may be a space that is maintained after the winding device is removed, a winding reference line, or the center point of a circle that is a vertical cross section cut perpendicular to the axis of the wound electrode assembly, and the "winding core side" means a region close to the winding core or a direction toward the winding core.

[0057] The distance between the winding start portion of the negative electrode holding portion and the winding start portion of the positive electrode may be two or more winding lengths, three or more winding lengths, four or more winding lengths, or five or more winding lengths. As the length of the negative electrode holding portion that does not correspond to the positive electrode holding portion increases, the internal rigidity of the winding core portion gradually increases, making it possible to prevent internal collapse due to repeated contraction and expansion of the electrode. As the length of the negative electrode holding portion that does not correspond to the positive electrode holding portion increases, loss that cannot participate in the reaction increases, so it is important to ensure appropriate rigidity to prevent internal collapse with the minimum length as necessary.

[0058] In another embodiment of the present specification, the battery may further include a negative electrode tab provided on the negative electrode uncoated portion.

[0059] In another embodiment of the present specification, the battery may further include an adhesive tape provided on the negative electrode tab and the negative electrode current collector positioned around the negative electrode tab.

[0060] In another embodiment of the present specification, the adhesive tape may be provided so as to extend up to a winding start portion of the negative electrode holding portion.

[0061] In another embodiment of the present specification, the negative electrode current collector may further include an additional adhesive tape provided on a surface opposite to the surface on which the negative electrode tab is provided, facing the adhesive tape.

[0062] In another embodiment of the present specification, the additional adhesive tape may be provided so as to extend up to the winding start portion of the negative electrode holding portion.

[0063] In another embodiment of the present specification, there is provided an electrode assembly in which the winding core of the electrode assembly 1 is the center of a circle, and the radius of the circle is the distance from the center of the circle to the longitudinal end of the positive electrode 120 on the winding core side, i.e., the winding start point of the positive electrode 120, and the central angle a of a minor arc formed from the contact point where a line extending from the winding start point of the negative electrode tab 116 to an arbitrary point around the arbitrary circle forms a right angle with a tangent to the arbitrary circle to the longitudinal end of the positive electrode 120 is 90° or less. Specifically, the central angle of the minor arc formed from the contact point to the longitudinal end of the positive electrode may be 90° or less, 85° or less, 80° or less, 75° or less, 70° or less, 65° or less, 60° or less, 55° or less, 50° or less, 45° or less, 40° or less, 35° or less, 30° or less, 25° or less, 20° or less, 15° or less, 10° or less, or 5° or less, or may be 0° or more, greater than 0°, 1° or more, 2° or more, 3° or more, or 4° or more. In this case, the winding start portion of the positive electrode 120 may be the winding start portion of a positive electrode holder on which the positive electrode active material layers (first positive electrode active material layer 122, second positive electrode active material layer 123) are provided.

[0064] Another embodiment of the present specification relates to an electrode assembly 1 in which a positive electrode 120, a negative electrode 110, and a separator (first separator 131, second separator 132) provided between the positive electrode 120 and the negative electrode 110 are stacked and wound up, the negative electrode 110 includes a negative electrode current collector 111 and a negative electrode active material layer (first negative electrode active material layer 112, second negative electrode active material layer 113) provided on at least one surface of the negative electrode current collector 111, the negative electrode 110 has a negative electrode tab 116 provided at one end of the negative electrode current collector 111 on the winding core side, the separator (first separator 131, second separator 132) and the negative electrode 110 extend further beyond the longitudinal end of the positive electrode 120 on the winding core side of the electrode assembly 1 and are further wound up, In at least one cross section of the electrode assembly 1 in the vertical direction of the winding core, a straight line L connecting the winding core to the longitudinal end of the positive electrode 120 on the winding core side ce and a straight line L connecting the winding core to the winding start point of the negative electrode tab 116. at The angle θ1 formed by the straight line L may be 90° or less. ceFrom the line L at The angle in the counterclockwise direction to the line L at From the line L ce The angle in the clockwise direction to the line L ce From the line L at The angle in the winding direction is

[0065] 4, the angle θ1 is the central angle a of the minor arc formed from the contact point where a line extending from the winding start portion of the negative electrode tab 116 to any point around the arbitrary circle forms a right angle with a tangent to the arbitrary circle, to the longitudinal end portion on the winding core side of the positive electrode. On the arbitrary circle, the contact point with the winding start portion of the negative electrode tab 116 is within a range of 90° or less in the winding direction, based on the longitudinal end portion on the winding core side of the positive electrode.

[0066] Because the negative electrode 110 is wound around the winding core so as to extend further than the positive electrode 120, the negative electrode tab 116 on the winding core side is wound first, and then the positive electrode 120 is wound. As shown in FIG. 4 , in any circle, if the contact point of the winding start portion of the negative electrode tab 116 is within a range of 90° or less in the winding direction with respect to the longitudinal end of the positive electrode 120 on the winding core side, the negative electrode tab 116 is positioned behind the winding start portion of the positive electrode 120 in the winding direction. In this case, the negative electrode tab 116, which is wound relatively earlier than the positive electrode 120 and is relatively rigid, presses the end of the positive electrode 120 on the winding core side by centrifugal force, thereby suppressing movement, i.e., slippage, of the end of the positive electrode 120 on the winding core side.

[0067] In another embodiment of the present specification, the length of the negative electrode tab 116 may be 2 mm or more and 5 mm or less in the winding direction, in which case rigidity is imparted to the end of the positive electrode 120 on the winding core side, thereby suppressing its movement.

[0068] In another embodiment of the present specification, the negative electrode 110 may further include an additional negative electrode uncoated portion at one end of an outer corner of the negative electrode current collector 111 where the negative electrode active material layer is not provided, and an additional negative electrode tab may be provided on the additional negative electrode uncoated portion.

[0069] In another embodiment of the present specification, a straight line L connecting the winding core to the longitudinal end of the positive electrode 120 on the winding core side ce and a straight line L connecting the winding core to the winding start point of the positive electrode tab (not shown). ae The angle θ2 formed by the straight line L may be greater than 90° and less than or equal to 180°. ce From the line L ae The angle in the counterclockwise direction to the line L ae From the line L ce The angle in the clockwise direction to the line L ce From the line L ae The angle θ2 may be a central angle b of a minor arc formed from the point where a line extending from the winding start point of the positive electrode tab (not shown) to any point around the arbitrary circle forms a right angle with a tangent to the arbitrary circle, to the longitudinal end of the positive electrode 120 on the winding core side.

[0070] If the positions within the arbitrary circle are likened to a clock, as shown in FIG. 4, the longitudinal end of the positive electrode 120 on the winding core side can be expressed as the 6 o'clock position, the winding start portion of the negative electrode tab 116 as the 4 o'clock position, and the winding start portion of the positive electrode tab (not shown) as the 12 o'clock position.

[0071] Another embodiment of the present specification provides a secondary battery including the above-described electrode assembly 1 and a battery case for accommodating the electrode assembly 1.

[0072] 5 shows an example of a secondary battery 20 housed in a battery case that houses a wound electrode assembly 1. The electrode assembly 1 has a circular vertical cross section of the winding core axis, and the battery case may be cylindrical. The battery case may include a can 21 and a cap assembly 22.

[0073] In one embodiment of the present specification, the secondary battery may have a form factor ratio (defined as the ratio of the diameter Φ to the height H, i.e., the diameter divided by the height of a cylindrical battery) of approximately 0.4 or less. Here, the form factor refers to values indicating the diameter and height of a cylindrical secondary battery. For example, the secondary battery may be an 18650 cell, a 21700 cell, or the like. In the case of an 18650 cell, the diameter is approximately 18 mm, the height is approximately 65 mm, and the form factor ratio is approximately 0.277. In the case of a 21700 cell, the diameter is approximately 21 mm, the height is approximately 70 mm, and the form factor ratio is approximately 0.300.

[0074] In one embodiment of the present specification, the secondary battery may be a cylindrical secondary battery with a form factor ratio of greater than 0.4.

[0075] A cylindrical secondary battery according to an embodiment of the present specification may be a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, or a 46800 cell. In the number representing the form factor, the first two digits represent the diameter of the cell, the next two digits represent the height of the cell, and the final digit 0 indicates that the cross section of the cell is circular.

[0076] The secondary battery according to one embodiment of the present specification may be a cylindrical secondary battery that is a cylindrical cell having a diameter of 46 mm, a height of 110 mm, and a form factor ratio of 0.418.

[0077] The secondary battery according to one embodiment of the present specification may be a cylindrical secondary battery that is a cylindrical cell having a diameter of 48 mm, a height of 75 mm, and a form factor ratio of 0.640.

[0078] The secondary battery according to one embodiment of the present specification may be a cylindrical secondary battery that is a cylindrical cell having a diameter of 48 mm, a height of 110 mm, and a form factor ratio of 0.436.

[0079] The secondary battery according to one embodiment of the present specification may be a cylindrical secondary battery that is a cylindrical cell having a diameter of 48 mm, a height of 80 mm, and a form factor ratio of 0.600.

[0080] The secondary battery according to one embodiment of the present specification may be a cylindrical secondary battery that is a cylindrical cell having a diameter of 46 mm, a height of 80 mm, and a form factor ratio of 0.575.

[0081] The can 21 may have a columnar structure with a space formed therein. The can 21 may accommodate a battery assembly 1 including electrodes and a separator, and an electrolyte (not shown) in the space. One side of the can 21 may be open, and the other side may be sealed. Here, the terms "one side" and "other side" refer to the upper and lower ends of the can 21 along the direction of gravity or the central axis of the can 21.

[0082] Can 21 may be constructed from a lightweight, conductive metallic material such as aluminum or an aluminum alloy.

[0083] A cap assembly 22 may be coupled to the top of the can 21 and may include a top cap, a safety vent, and a current interrupt device.

[0084] The top cap protrudes from the top of the cap assembly 22 and serves as an electrode terminal for electrical connection to the outside. The safety vent can release high-pressure gas when internal pressure rises and gas is generated above a certain level, and the current interruption device can interrupt current when the internal pressure of the battery rises.

[0085] The top cap may be coupled to the top of the can 21. That is, the top cap may be coupled to a crimping portion located at the top of the can 21.

[0086] The secondary battery 20 according to the present invention may include a gasket between the crimping portion and the top cap, which can increase the sealing strength of the case.

[0087] The top cap may include a protrusion that protrudes upward in the direction of gravity, a rim that couples with the gasket, and a connecting portion that connects the protrusion and the rim.

[0088] The safety vent may be located under the top cap and coupled to an end of the top cap. The safety vent may contact an end of the top gap by a certain length, and the portion of the safety vent excluding the contact length may be spaced a certain distance from the top cap.

[0089] The safety vent may be bent at least one time. For example, the safety vent may have two notches in a portion that does not contact the top cap. That is, the safety vent 12 may be bent at the notches, and the center of the safety vent may be recessed to form a concave central portion. The safety vent may also have a vent portion that connects the end that contacts the top cap and the concave central portion.

[0090] The current interrupt element may be positioned below the safety vent and may be in at least partial contact with the safety vent.

[0091] The current interrupting element may include a central portion that protrudes toward the safety vent and a CID filter portion located outside the central portion. Therefore, the cap assembly 22 may be configured so that the central portion of the current interrupting element and the recessed central portion of the safety vent come into contact with each other.

[0092] The cap assembly 22 according to the present invention may be provided with a CID gasket at the end of the CID filter section, which can prevent the safety vent from contacting the current interrupting element at any portion other than the center.

[0093] Another embodiment of the present disclosure provides a battery pack including two or more of the above-described secondary batteries. Figure 6 is a diagram schematically illustrating the configuration of a battery pack according to an embodiment of the present invention.

[0094] 6, a battery pack 200 according to an embodiment of the present invention includes an assembly of electrically connected secondary battery cells (cylindrical battery cells 201) and a pack housing 202 that accommodates the assembly. The cylindrical secondary battery cells (cylindrical battery cells 201) are the battery cells according to the above-described embodiments. For convenience of illustration, components such as bus bars for electrically connecting the cylindrical battery cells 201, a cooling unit, and external terminals are omitted from the drawing.

[0095] Another embodiment of the present specification provides a vehicle including the above-described battery pack 200. The vehicle may be any vehicle that moves cargo, people, etc., or performs work while moving, and may be a bicycle, heavy machinery, agricultural equipment, a car, a bus, an airplane, etc.

[0096] The battery pack 200 may be mounted on a vehicle V. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle V may be a four-wheeled vehicle or a two-wheeled vehicle. FIG. 7 is a diagram illustrating the vehicle V including the battery pack 200 of FIG. 6.

[0097] 7, an automobile V according to an embodiment of the present specification includes a battery pack 200 according to an embodiment of the present specification. The automobile V operates by receiving power from the battery pack 200 according to an embodiment of the present specification. [Example]

[0098] As described above, the present invention has been described using limited embodiments and drawings, but the present invention is not limited thereto, and it goes without saying that various modifications and variations can be made by a person having ordinary skill in the art to which the present invention pertains within the technical spirit of the present invention and the equivalent scope of the claims described below.

[0099] Manufacturing example As shown in Figure 2, a jelly roll (J / R) with a cross-sectional diameter of 20.5 mm was fabricated by stacking a negative electrode, a positive electrode, and two separators between them and winding the electrode assembly. The thickness of the positive electrode current collector was approximately 0.015 mm, and the total thickness of the positive electrode holder, in which positive electrode active material layers were provided on both sides of the positive electrode current collector, was approximately 0.150 mm. The thickness of the negative electrode current collector was approximately 0.008 mm, and the total thickness of the negative electrode holder, in which negative electrode active material layers were provided on both sides of the negative electrode current collector, was approximately 0.180 mm.

[0100] The jelly roll assembly was inserted into a cylindrical can (cross-sectional diameter: 21 mm), and then a carbonate-based electrolyte was poured into the can and sealed to complete the batteries of the example and comparative example.

[0101] [Experimental Example] The batteries of the examples and comparative examples were charged and discharged once under the following conditions, and then the presence or absence of deformation of the jelly roll was observed.

[0102] <Test Condition> Temperature: 25℃ Charge:4.25V 1C 50mA cut,rest 10min Discharge:1C 2.5V cut,rest 20min

[0103] To confirm the deformation of the battery after one charge / discharge, CT imaging was performed using an XSCAN-8225 device at 225 kV and a frame rate of 3 fps, and the results are shown in Figures 8 to 10 and 12.

[0104] 8 to 10, 12, and 14 are CT images, and the separator is not visible. The thicker lines represent the positive electrode, and the thinner lines represent the negative electrode. In these images, the negative electrode holder and the positive electrode holder have the same or similar thickness, but the carbon-based active material in the negative electrode holder allows light to pass through, so the negative electrode active material layer is not visible in the CT images, and only the negative electrode current collector is visible, making it appear relatively thin in the CT images.

[0105] 8, 9, and 10 are the same CT images. Here, Fig. 8(a), Fig. 9(a), and Fig. 10(a) are CT images of Comparative Example 1, and Fig. 8(b), Fig. 9(b), and Fig. 10(b) are CT images of Example 1. In this case, Comparative Example 1 and Example 1, which are compared together, were manufactured identically in all other factors except for the differences in the indicated arrangements.

[0106] FIG. 8 shows the winding directions of a) of Comparative Example 1 and b) of Example 1, and the distance between the winding start point of the negative electrode holding part and the winding start point of the positive electrode is It can be seen from JPEG0007718630000001.jpg3626 that the winding length of Comparative Example 1 a) does not reach two turns, while the winding length of Example 1 b) is two turns or more.

[0107] In FIG. 9, the dotted lines indicate the straight lines connecting the winding cores of Comparative Example 1 a) and Example 1 b) to the winding start points of the positive electrodes, and it can be seen that Comparative Example 1 a) passes through the negative electrode holding part once, while Example 1 b) passes through the negative electrode holding part twice.

[0108] FIG. 10 shows that the degree of deformation after battery operation can be confirmed based on the positioning difference confirmed in FIGS. 8 and 9. In a similar manner to FIG. 14, the degree of deformation of the negative electrode on the winding core side near the positive electrode winding start point can be confirmed from the angle of deformation relative to the reference line. The results are shown in Table 1 below.

[0109] [Table 1]

[0110] As shown in FIG. 10, the battery of Comparative Example 1 experienced deformation on the winding core side due to electrode expansion during charge and discharge. However, in the example in which the battery was further wound for more than two winding lengths and had a double rigid negative electrode holder on the winding core side of the positive electrode winding start, movement of the positive electrode winding start was suppressed, and deformation that could cause an internal short circuit was reduced by 94.9% ((52.9-2.7) x 100 / 52.9). Meanwhile, FIGS. 12(a) and 12(b) are additional examples that confirm the effect of the tape attachment method as in FIG. 11. Other factors were the same as in FIG. 11, except for the tape attachment method. In FIG. 12(a), tape (tape 140, additional tape 145) was attached to the negative electrode tab in the same manner as in FIG. 11(a) (Example 2). In FIG. 12(b), tape (tape 140, additional tape 145) was attached to the negative electrode tab at the same time as in FIG. 11(b) (Example 3).

[0111] The degree of deformation after battery operation due to differences in the tape placement as shown in Figure 11 can be confirmed, and the degree of deformation was measured using the method shown in Figure 14 and is shown in Table 2 below.

[0112] [Table 2]

[0113] 11, it can be seen that Example 3, in which the tape was applied extending to the negative electrode holding portion, showed a 51.3% ((19.5-9.5) × 100 / 19.5) reduction in deformation compared to Example 2. To achieve the arrangements shown in Figures 10b), 12a), and 12b, the position of the positive electrode winding start point was adjusted based on the laminate of Comparative Example 1 in Figure 10a. That is, the positive electrode winding start point was moved closer to the negative electrode tab. The changed position of the positive electrode winding start point was determined taking into account the size of the winding core 10, the target diameter of the wound jelly roll, and the diameter of the battery case.

[0114] As shown in Figure 13, if the cumulative winding length from the winding start part of the negative electrode tab on the winding core side to the winding start part of the positive electrode is divided according to the number of windings and expressed as the number of turns, in the nth turn of winding length to which the winding start part of the positive electrode belongs, the winding start part of the positive electrode was positioned at a position that was at least 3 / 4 and less than 4 / 4 of the winding length of the nth turn. It was also confirmed that when wound in this position, the negative electrode tab was positioned behind the positive electrode winding start part in the winding direction of the positive electrode, and movement of the positive electrode end part on the winding core side was suppressed.

Claims

1. An electrode assembly in which a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode are stacked and wound, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode includes a negative electrode support portion in which the negative electrode active material layer is provided on the negative electrode current collector, and a negative electrode uncoated portion in which the negative electrode active material layer is not provided at one end of the negative electrode current collector on the winding core side, At the winding core side of the electrode assembly, the separator and the negative electrode extend beyond the winding start portion of the positive electrode and are further wound, an electrode assembly, in which in at least one cross section perpendicular to a winding core axis of the electrode assembly, a distance between a winding start portion of the negative electrode holding portion and a winding start portion of the positive electrode in a winding direction from the winding core of the electrode assembly is equal to or greater than two winding lengths.

2. 2. The electrode assembly according to claim 1, wherein in at least one cross section of the electrode assembly in a direction perpendicular to the winding core axis, a straight line connecting the winding core and the winding start portion of the positive electrode passes through the negative electrode holding portion two or more times.

3. The electrode assembly of claim 1 , further comprising a negative electrode tab provided on the negative electrode uncoated portion.

4. The electrode assembly according to claim 3 , further comprising an adhesive tape extending to a winding start portion of the negative electrode tab, the negative electrode current collector positioned around the negative electrode tab, and the negative electrode holder.

5. The electrode assembly according to claim 4 , further comprising an additional adhesive tape provided on a surface of the negative electrode current collector opposite to the surface on which the negative electrode tab is provided, facing the adhesive tape.

6. The electrode assembly according to claim 5 , wherein the additional adhesive tape extends to a winding start portion of the negative electrode holding portion.

7. In at least one cross section perpendicular to the core axis of the electrode assembly, 4. The electrode assembly according to claim 3, wherein the winding core of the electrode assembly is the center of a circle, and the radius of the circle is the distance from the center of the circle to the winding start portion of the positive electrode.

5. The electrode assembly according to claim 3, wherein a minor arc formed from a point where a line extending from the winding start portion of the negative electrode tab to a point around the circle forms a right angle with a tangent to the circle, to the winding start portion of the positive electrode, has a central angle greater than 0 degrees and not greater than 90 degrees.

8. the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode includes a positive electrode uncoated portion on which the positive electrode active material layer is not provided, and a positive electrode tab is provided on the positive electrode uncoated portion; 8. The electrode assembly according to claim 7, wherein a central angle of a minor arc formed from a point where a line extending from the winding start portion of the positive electrode tab to any point around the circle forms a right angle with a tangent to the circle, to the winding start portion of the positive electrode, is greater than 90 degrees and is not greater than 180 degrees.

9. the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode includes the positive electrode active material layer, two positive electrode holding portions spaced apart from each other, and a positive electrode uncoated portion provided between the two positive electrode holding portions, The electrode assembly according to claim 1 , wherein a positive electrode tab is provided on the positive electrode uncoated portion.

10. 4. The electrode assembly of claim 3, wherein the negative electrode further comprises an additional negative electrode uncoated portion at an end of an outer corner of the negative electrode current collector where the negative electrode active material layer is not provided, and an additional negative electrode tab is provided on the additional negative electrode uncoated portion.

11. the positive electrode includes a positive electrode current collector and positive electrode active material layers provided on both surfaces of the positive electrode current collector, The electrode assembly according to claim 1 , wherein the positive electrode active material layers provided on both sides of the positive electrode current collector have the same winding start position.

12. the positive electrode includes a positive electrode active material layer provided on both sides of the positive electrode current collector, The electrode assembly according to claim 9 , wherein the positive electrode active material layers provided on both sides of the positive electrode current collector have the same winding end point.

13. The electrode assembly according to claim 3 , wherein the length of the negative electrode tab is 2 mm to 5 mm in the winding direction.

14. The separation membrane includes a first separation membrane and a second separation membrane, The electrode assembly of claim 1 , wherein the electrode assembly is formed by sequentially stacking and winding the negative electrode, the first separator, the positive electrode, and the second separator.

15. The electrode assembly according to claim 14 , wherein the electrode assembly is wound so that the negative electrode is positioned at the outermost corner.

16. A secondary battery comprising the electrode assembly according to any one of claims 1 to 15 and a battery case for accommodating the electrode assembly.

17. The secondary battery according to claim 16, wherein the electrode assembly has a circular vertical cross section of the winding core axis, and the battery case is cylindrical.

18. A battery pack comprising two or more secondary batteries according to claim 16.

19. 20. A vehicle comprising the battery pack of claim 18.

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