Jelly roll type electrode assembly and secondary battery including the same

Abstract

The present invention relates to a jelly-roll type electrode assembly and a secondary battery including the same.

Description

[Technical field]

[0001] The present invention relates to a jelly roll-type electrode assembly and a secondary battery including the same, and more particularly to a jelly roll-type electrode assembly having a peripheral tab structure and a cylindrical secondary battery including the same. This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0130820 filed in the Korean Intellectual Property Office on October 12, 2022, and all contents disclosed in the documents of the Korean patent application are incorporated herein by reference. [Background technology]

[0002] In the case of cylindrical batteries, a jelly roll-shaped electrode assembly is manufactured by winding a long and narrow electrode with a fixed width into a roll. When such a jelly roll-shaped electrode assembly is inserted into a battery case to manufacture a cylindrical battery, the electrodes repeatedly contract and expand during charging and discharging, and stress is generated according to the steps due to the jelly roll structure.

[0003] In particular, in the case of a jelly-roll type electrode assembly having an outermost negative electrode structure, the outermost negative electrode covers the end of the positive electrode, and the space on the side of the free edge of the positive electrode is left empty due to the thickness of the positive electrode. In this case, the step due to the thickness of the positive electrode creates stress in the negative electrode, and this stress is concentrated on the surface opposite to the surface facing the positive electrode during charging and discharging, causing cracks on the outside of the negative electrode.

[0004] In order to prevent such cracks from occurring on the outside of the negative electrode, it is necessary to develop technology that can improve the stress concentration in that area of ​​the negative electrode. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a jelly-roll type electrode assembly having a modified design of the jelly-roll type electrode assembly and a secondary battery including the same.

[0006] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0007] One embodiment of the present invention provides a jelly roll type electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound up, wherein the second electrode includes a second electrode collector; and a second electrode active material layer provided on at least one side of the second electrode collector, and the first electrode includes a first electrode collector; a first electrode active material layer provided on at least one side of the first electrode collector; a breakage prevention part provided on a surface of the first electrode collector opposite a surface facing a longitudinal end of the second electrode; and a welded part electrically connecting the first electrode collector and the breakage prevention part, wherein the breakage prevention part includes a welded part electrically connected to the first electrode collector, and both longitudinal ends of the breakage prevention part do not coincide with the longitudinal ends of the second electrode.

[0008] Another embodiment of the present invention provides a secondary battery comprising the jelly-roll type electrode assembly; and a battery case for housing the electrode assembly. Effect of the Invention

[0009] A jelly-roll type electrode assembly and a secondary battery including the same according to an embodiment of the present invention include a disconnection prevention part, thereby preventing cracks and deformation of the electrode assembly due to stress concentration in the outermost negative electrode.

[0010] In addition, in the jelly-roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention, the breakage prevention part is electrically connected to the electrode current collector via a welded part to provide an additional conductive path, thereby suppressing an increase in resistance even when a break occurs, thereby improving the stability of the battery.

[0011] In addition, the jelly-roll type electrode assembly and the secondary battery including the same according to an embodiment of the present invention can prevent local problems such as lithium deposition due to reduction in roundness and formation of additional steps by adjusting the positions of the disconnection prevention parts and the welded parts, and can minimize the occurrence of additional cracks and deformations of the electrode assembly due to the formation of fixing points.

[0012] The effects of the present invention are not limited to those described above, and effects not mentioned herein will be apparent to those skilled in the art from the specification and accompanying drawings of this application. [Brief description of the drawings]

[0013] [Figure 1] 1 illustrates a jelly-roll type electrode assembly including a breakage prevention unit according to an embodiment of the present invention. [Diagram 2] 1 illustrates a jelly-roll type electrode assembly including a breakage prevention unit according to an embodiment of the present invention. [Diagram 3] 1 is an image showing a jelly roll type electrode assembly according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram illustrating a step portion of a jelly-roll type electrode assembly according to an embodiment of the present invention. [Diagram 5] 1 shows a jelly roll type electrode assembly for reference. [Explanation of symbols]

[0014] 1000 ···Jelly roll type electrode assembly 100, 100'...1st electrode 101: First electrode collector 102, 103...first electrode active material layer 110: End portion in the longitudinal direction of the first electrode 20, 20' separator 300...2nd electrode 301 Second electrode current collector 302, 303...Second electrode active material layer 310 Longitudinal end of second electrode 40 Disconnection prevention part W: Welded part 50 First electrode tab 60 Step 70 ···Disconnection prevention tape L1: Distance between the disconnection prevention part and the first electrode active material layer L2: Length of the breakage prevention part in the longitudinal direction L3: Distance between the disconnection prevention part and the first electrode tab L4, L8: Distance between the welded part and the breakage prevention part L5, L7: Distance between the welded part and the part coated with active material on one side L6: Length of the part coated with active material on one side in the longitudinal direction Lh: Length of the breakage prevention part in the winding axis direction DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Throughout the specification of this application, when a part is said to "comprise" a certain element, this means that it may further include other elements, but not to the exclusion of other elements, unless specifically stated to the contrary.

[0016] Throughout the specification of this application, when an element is said to be "on" another element, this includes not only when the element is in contact with the other element, but also when there is another element between the two elements.

[0017] 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.

[0018] One embodiment of the present invention provides a jelly-roll type electrode assembly in which a first electrode, a separator, and a second electrode are laminated and wound up, the second electrode including a second electrode collector and a second electrode active material layer provided on at least one side of the second electrode collector, the first electrode including a first electrode collector, a first electrode active material layer provided on at least one side of the first electrode collector, a disconnection prevention part provided on a surface of the first electrode collector opposite to a surface facing an end of the second electrode in the longitudinal direction, and a welded part electrically connecting the first electrode collector and the disconnection prevention part, and both ends of the disconnection prevention part in the longitudinal direction do not coincide with the ends of the second electrode in the longitudinal direction. The jelly-roll type electrode assembly according to one embodiment of the present invention and a secondary battery including the same can prevent cracks and deformations of the electrode assembly due to stress concentration in the outermost negative electrode by including the disconnection prevention part. In addition, since the breakage prevention part is electrically connected to the electrode collector via a welded part to provide an additional conductive path, it is possible to suppress an increase in resistance even when a breakage occurs, thereby improving the stability of the battery.

[0019] Figures 1 and 2 show a jelly-roll type electrode assembly including a breakage prevention part according to an embodiment of the present invention. Specifically, Figure 1 shows an embodiment including a weld including a first electrode active material layer on a surface of a first electrode collector facing an end of a second electrode in the longitudinal direction, and Figure 2 shows an embodiment including a weld not including a first electrode active material layer on a surface of a first electrode collector facing an end of a second electrode in the longitudinal direction.

[0020] 1 and 2, a jelly roll type electrode assembly according to an embodiment of the present invention is a jelly roll type electrode assembly in which a first electrode 100, 100', a separator 20, 20', and a second electrode 300 are stacked and wound up. The second electrode 300 includes a second electrode current collector 301; and second electrode active material layers 302, 303 provided on at least one surface of the second electrode current collector 301. The first electrode 100 includes a first electrode current collector 101; The electrode assembly includes first electrode active material layers 102, 103 provided on at least one side; a breakage prevention part 40 provided on the opposite side of the surface of the first electrode collector 101 facing the longitudinal end 310 of the second electrode; and a welded part (W) electrically connecting the first electrode collector 101 and the breakage prevention part 40, and the breakage prevention part 40 includes a welded part (W) electrically connected to the first electrode collector 101, and both ends in the longitudinal direction of the breakage prevention part 40 may not coincide with the longitudinal end 210 of the second electrode. Here, the "lengthwise direction" may mean the length direction of the electrode assembly including the first electrode, the separator, the second electrode, and the electrode assembly in a laminated form before winding, that is, the direction perpendicular to the winding axis direction of the electrode assembly after winding. The "lengthwise ends coincide" may include not only the case where each end is located at the completely same position based on a cross section perpendicular to the longitudinal direction of the electrode assembly, but also the case where there are errors in the process and measurement.

[0021] According to an embodiment of the present invention, the breakage prevention part may be a conductive material. Specifically, the breakage prevention part may be any one selected from copper, stainless steel, aluminum, nickel, titanium, and calcined carbon. More specifically, the breakage prevention part may be copper, stainless steel, or aluminum, and may be surface-treated with carbon, nickel, titanium, silver, or the like. For example, the breakage prevention part may include a transition metal that easily adsorbs carbon, such as copper or nickel. When the breakage prevention part is the conductive material described above, the breakage prevention part is electrically connected to the electrode collector through a welded part to provide an additional conductive path, and therefore, even when the electrode collector is broken, an increase in resistance can be suppressed and the stability of the battery can be improved.

[0022] According to one embodiment of the present invention, the disconnection prevention part may be made of the same material as the first electrode collector. Specifically, the first electrode collector may be conductive and not cause a chemical change in the battery, as described below, and the disconnection prevention part may be made of the same material as the first electrode collector. For example, the first electrode collector and the disconnection prevention part may be made of copper foil (Cu foil). When the first electrode collector and the disconnection prevention part are made of different materials, the part fixed by the fixing point and the part not fixed by the fixing point may have different degrees of deformation or volume change during charging and discharging, and the first electrode collector may be distorted due to partial deformation of the electrode assembly. When a breakage prevention part made of the same material as the first electrode collector is used, the first electrode collector and the breakage prevention part have similar elongation rates and the degree of deformation or volume change during charging and discharging can be similar, so that it is possible to reduce distortion of the electrode collector due to the fixing point and prevent problems such as corrosion that can occur when welding dissimilar materials. In addition, since the material used for the first electrode collector can be used, it is easy to provide the breakage prevention part without additional production equipment.

[0023] According to one embodiment of the present invention, both ends in the length direction of the disconnection prevention part may not coincide with the ends in the length direction of the second electrode. Specifically, the ends in the length direction of the second electrode may be located between both ends in the length direction of the disconnection prevention part. This effectively complements the region of the first electrode collector corresponding to the ends in the length direction of the second electrode, particularly the surface opposite to the surface facing the ends in the length direction of the second electrode, and prevents cracks and deformation due to stress concentration in the outermost first electrode.

[0024] According to one embodiment of the present invention, both ends of the breakage prevention part in the length direction may be spaced 2 mm or more and 10 mm or less from the end of the second electrode in the length direction. Specifically, both ends of the breakage prevention part in the length direction may be spaced 3 mm or more or 5 mm or more, or 9 mm or less or 7 mm or less from the end of the second electrode in the length direction. When both ends of the breakage prevention part in the length direction have a distance from the end of the second electrode in the length direction within the above-mentioned range, the region corresponding to the end of the second electrode in the length direction of the first electrode collector, particularly the opposite surface of the surface facing the end of the second electrode in the length direction, can be effectively complemented, and cracks and deformation due to stress concentration of the outermost first electrode can be prevented. In addition, the area required for welding the breakage prevention part can be sufficiently secured.

[0025] According to an embodiment of the present invention, the breakage prevention part may be provided on a surface of the first electrode collector opposite to a surface facing the end of the second electrode in the longitudinal direction. Specifically, the breakage prevention part may be provided on a surface of the first electrode collector opposite to a surface facing the end of the second electrode in the longitudinal direction, spaced apart from an end of the first electrode active material layer in the longitudinal direction. That is, the breakage prevention part may be provided on a first electrode uncoated part of the first electrode collector on which the first electrode active material layer is not provided. When the breakage prevention part is provided on a surface opposite to a surface facing the end of the second electrode in the longitudinal direction, a problem of additional step formation caused by the thickness of the breakage prevention part can be prevented, and asymmetric formation of the electrode assembly can be minimized to improve the roundness. As a result, damage to the lower end of the electrode assembly in a later process of inserting the electrode assembly into a battery case can be minimized, and local problems such as damage to the electrode assembly due to pressure increase in a specific part when the volume of the electrode assembly changes due to charge and discharge cycles, side reactions due to electrolyte shortage, and lithium precipitation can be reduced. Here, the circularity may refer to a value obtained by subtracting the minimum outer diameter from the maximum outer diameter of the jelly-roll type electrode assembly.

[0026] According to one embodiment of the present invention, the first electrode may further include a first electrode tab provided at an end in the length direction of the first electrode, and the breakage prevention part may be provided between an end in the length direction of the first electrode active material layer and the first electrode tab. The first electrode tab may be welded and electrically connected to a battery case for accommodating the electrode assembly at an outermost portion of the jelly roll type electrode assembly, and may act as a fixing point of the electrode assembly during welding. When the electrode assembly further includes a first electrode tab at the outermost portion, the breakage prevention part may be provided between an end in the length direction of the first electrode active material layer and the first electrode tab, thereby reducing distortion of an additional electrode current collector due to multiple fixing points.

[0027] According to an embodiment of the present invention, the first electrode tab may be provided on a surface of the first electrode collector opposite to a surface facing the end of the second electrode in the longitudinal direction. That is, the first electrode tab may be provided on the same surface as a breakage prevention part provided on the first electrode collector, and may minimize the formation of a step due to the thickness of the first electrode tab and the breakage prevention part. This can prevent the problem of additional step formation that may occur when the first electrode tab is provided on a surface of the first electrode facing the end of the second electrode in the longitudinal direction, and can minimize the asymmetric formation of the electrode assembly to improve the roundness. This can minimize damage to the lower end of the electrode assembly in a later process of inserting the electrode assembly into a battery case, and can reduce the occurrence of local problems such as damage to the electrode assembly due to an increase in pressure at a specific part when the volume of the electrode assembly changes due to charge / discharge cycles, side reactions due to electrolyte shortage, and lithium deposition. In addition, welding between the first electrode tab located at the outermost part of the electrode assembly and the battery case can be made easier, and the electrical connection can be made more stable.

[0028] FIG. 3 is an image showing a jelly roll type electrode assembly according to an embodiment of the present invention.

[0029] According to one embodiment of the present invention, the length of the breakage prevention part in the winding axis direction may be 50% or more and 100% or less based on the length of the first electrode current collector in the winding axis direction. Specifically, referring to FIG. 3, the length (Lh) of the breakage prevention part in the winding axis direction may be 55% or more, 60% or more, or 65% or more based on 100% of the length of the first electrode current collector in the winding axis direction, and the length (Lh) of the breakage prevention part in the winding axis direction may be 95% or less, 90% or less, or 85% or less based on 100% of the length of the first electrode current collector in the winding axis direction. When the length range of the breakage prevention part in the winding axis direction is satisfied within the above-mentioned range, the region of the first electrode current collector corresponding to the end of the second electrode in the length direction, particularly the opposite side of the surface facing the end of the second electrode in the length direction, can be effectively complemented, and the occurrence of problems such as cracks during charging and discharging can be reduced, thereby ensuring the stability of the battery.

[0030] According to one embodiment of the present invention, the length of the breakage prevention part in the longitudinal direction may be 25 mm or more and 400 mm or less. Specifically, referring to FIG. 2, the length (L2) of the breakage prevention part in the longitudinal direction may be 30 mm or more, 35 mm or more, or 40 mm or more, and the length (L2) of the breakage prevention part in the longitudinal direction may be 395 mm or less, 390 mm or less, or 385 mm or less. When the length range of the breakage prevention part in the longitudinal direction is satisfied within the above-mentioned range, the region of the first electrode current collector corresponding to the longitudinal end of the second electrode, particularly the opposite side of the surface facing the longitudinal end of the second electrode, can be effectively complemented, and the occurrence of problems such as cracks during charging and discharging can be reduced, ensuring the stability of the battery.

[0031] According to one embodiment of the present invention, the separation distance between one end of the breakage prevention part in the length direction and an end of the first electrode active material layer provided on one side of the first electrode collector 101 in the length direction may be 5 mm or more and 100 mm or less. Specifically, referring to Fig. 2, the separation distance (L1) between one end of the breakage prevention part 40 in the length direction and an end of the first electrode active material layer 102 in the length direction provided on one side of the first electrode collector 101 in the length direction may be 10 mm or more, 15 mm or more, or 20 mm or more, and the separation distance (L1) between one end of the breakage prevention part 40 in the length direction and an end of the first electrode active material layer 102 in the length direction provided on one side of the first electrode collector 101 in the length direction may be 95 mm or less, 90 mm or less, or 85 mm or less. When the separation distance (L1) between one longitudinal end of the breakage prevention part and the longitudinal end of the first electrode active material layer provided on one side of the first electrode collector satisfies the above-mentioned range, a welding space that does not damage the first electrode can be secured, and the breakage prevention part can be provided in the jelly-roll type electrode assembly while minimizing the formation of an additional step in relation to the first electrode active material layer.

[0032] According to one embodiment of the present invention, a separation distance between one end of the breakage prevention part in the length direction and the first electrode tab provided on one side of the first electrode collector 101 may be 5 mm or more and 100 mm or less. Specifically, referring to Fig. 2, a separation distance (L3) between one end of the breakage prevention part 40 in the length direction and the first electrode tab 50 provided on one side of the first electrode collector 101 may be 10 mm or more, 15 mm or more, or 20 mm or more, and a separation distance (L3) between one end of the breakage prevention part 40 in the length direction and the first electrode tab 50 provided on one side of the first electrode collector 101 may be 95 mm or less, 90 mm or less, or 85 mm or less. When the separation distance (L3) between one end of the breakage prevention part in the length direction and the first electrode tab provided on one side of the first electrode collector satisfies the above-mentioned range, the breakage prevention part can be provided in the jelly roll type electrode assembly while minimizing the formation of an additional step in relation to the first electrode tab, and it is possible to prevent the first electrode tab and the breakage prevention part from being further welded together during welding, thereby preventing an increase in resistance.

[0033] According to an embodiment of the present invention, the first electrode may include a welded portion electrically connecting the first electrode collector and the breakage prevention portion. Specifically, referring to FIG. 1 and FIG. 2, the welded portion (W) is a region where welding is performed to electrically connect the first electrode collector 101 and the breakage prevention portion 40, and may refer to one region including a cross section perpendicular to the length direction of the first electrode. More specifically, the welded portion may include the breakage prevention portion and the first electrode collector; or the breakage prevention portion, the first electrode active material layer, and the first electrode collector. In addition, the welded portion may be formed in a line or spot shape by a welding method described later, and may have a predetermined length in the winding axis direction, a length in the length direction, and an area required for welding.

[0034] According to one embodiment of the present invention, the welded portion may be formed at both ends of the breakage prevention portion in the length direction, or may be formed at a predetermined distance from both ends of the breakage prevention portion. Specifically, referring to FIG. 2, the separation distance (L4, L8) between the welded portion and both ends of the breakage prevention portion in the length direction may be 2 mm or less. When the separation distance between the welded portion and both ends of the breakage prevention portion in the length direction satisfies the above-mentioned range, it is possible to secure an area required for welding and minimize defects due to bending of the breakage prevention portion during the winding process.

[0035] According to an embodiment of the present invention, the welded portion may not overlap the end of the second electrode in the longitudinal direction. Specifically, the welded portion may be spaced apart from the end of the second electrode in the longitudinal direction by 1 mm or more and 8 mm or less, based on the longitudinal direction of the first electrode. More specifically, the welded portion may be spaced apart from the end of the second electrode in the longitudinal direction by 1 mm or more or 3 mm or more, or 8 mm or less or 6 mm or less. When the welded portion has a distance from the end of the second electrode in the longitudinal direction within the above-mentioned range, a region required for welding the breakage prevention portion can be sufficiently secured, and a problem of additional step formation that may occur when the welded portion overlaps the end of the second electrode in the longitudinal direction can be prevented.

[0036] According to an embodiment of the present invention, the welded portion may be provided in a plurality of portions. Specifically, the welded portion may be provided in a plurality of portions on the first electrode collector to minimize asymmetry due to a fixed point. During charging and discharging, the first electrode collector may repeatedly contract and expand, causing a change in volume, and the welded portion may act as a fixed point, causing distortion of the first electrode collector. By providing the welded portion in a plurality of portions, it is possible to prevent cracks caused by the formation of fixed points at specific positions, and to ensure a sufficient cross-sectional area of ​​the conductive path even in the event of a break, thereby preventing a decrease in electrochemical properties, such as a decrease in cycle efficiency due to an increase in resistance.

[0037] According to an embodiment of the present invention, the welds may be provided in a plurality of positions, and the welds may be formed symmetrically with respect to each other. Specifically, the welds may be formed symmetrically with respect to a center of the breakage prevention part in the longitudinal direction. That is, the separation distances (L4, L8) between the welds and both ends of the breakage prevention part in the longitudinal direction may be the same. Here, the center of the breakage prevention part in the longitudinal direction may mean a half point of the length of the breakage prevention part in the longitudinal direction. Also, the welds may be formed symmetrically with respect to a center of the breakage prevention part in the winding axis direction. Here, the center of the breakage prevention part in the winding axis direction may mean a half point of the length of the breakage prevention part in the winding axis direction. When the welds are formed symmetrically with respect to the center of the breakage prevention part in the longitudinal direction or the center of the winding axis direction, asymmetric formation of the breakage prevention part including the welds may be minimized, and stress acting on both sides of a fixing point of the breakage prevention part may be uniform, thereby minimizing distortion of the breakage prevention part.

[0038] According to one embodiment of the present invention, the welded portion may be provided in a plurality of portions, and the end portion in the longitudinal direction of the second electrode may be located between the plurality of welded portions. Specifically, the welded portion may be provided in a plurality of portions, spaced apart from the end portion in the longitudinal direction of the second electrode by 1 mm to 8 mm, such that the end portion in the longitudinal direction of the second electrode is located between the plurality of welded portions. This effectively complements the surface opposite to the surface facing the end portion in the longitudinal direction of the second electrode, and minimizes defects due to bending of the breakage prevention portion during a winding process.

[0039] According to an embodiment of the present invention, the plurality of welds may be formed symmetrically with respect to a center of the first electrode collector in the winding axis direction. Here, the center of the first electrode collector in the winding axis direction may refer to a point halfway along the length of the first electrode collector in the winding axis direction. When the plurality of welds are formed symmetrically with respect to a center of the first electrode collector in the winding axis direction, asymmetric formation of the electrode assembly including the breakage prevention part can be minimized, and roundness can be improved. As a result, damage to the lower end of the electrode assembly in a post-process of inserting the electrode assembly into a battery case can be minimized, and local problems such as damage to the electrode assembly due to pressure increase at a specific part when the volume of the electrode assembly changes due to charge / discharge cycles, side reactions due to electrolyte shortage, and lithium precipitation can be reduced.

[0040] According to an embodiment of the present invention, the welded portion may include the first electrode active material layer provided on a surface of the first electrode collector facing the longitudinal end of the second electrode. Specifically, referring to FIG. 1, the first electrode collector 101 may have the first electrode active material layer 103 provided on a surface facing the longitudinal end 310 of the second electrode, and the welded portion (W) may be formed in one region in the longitudinal direction of the first electrode including the disconnection prevention portion 40, the first electrode collector 101, and the first electrode active material layer 103. When the welded portion (W) includes the first electrode active material layer 103, the welded portion is suitable for ultrasonic welding or arc welding. Specifically, ultrasonic welding is a method of applying high-frequency transverse vibration to a base material to diffuse atoms in a contact portion by vibration energy to bond the base material, and since it does not involve heating, it is possible to prevent thermal damage to the first electrode during welding. In addition, arc welding is a processing method in which the base material or material is melted using an arc discharge to join the workpieces, and since the breakage prevention part provided on one side is melted while the first electrode collector located below is welded together, one-sided welding is easy.

[0041] According to an embodiment of the present invention, the welded portion may not include the first electrode active material layer on a surface of the first electrode collector facing the longitudinal end of the second electrode. Specifically, referring to FIG. 2(a), the first electrode collector 101 may include a one-side active material coated portion on which the first electrode active material layer 103 is provided, and a plain portion on which the first electrode active material layer is not provided, on a surface facing the longitudinal end 310 of the second electrode, and the welded portion (W) may be formed in one region in the longitudinal direction of the first electrode including the disconnection prevention portion 40 and the plain portion of the first electrode collector 101. In other words, the welded portion may further include a plain portion for welding on a surface of the first electrode collector opposite to the surface on which the disconnection prevention portion is provided. When the welded portion (W) does not include the first electrode active material layer 103, the welded portion is suitable for laser welding or resistance welding. Specifically, laser welding is a method of welding by applying pressure after heating the parts to be joined with an oxyacetylene or propane flame, and a YAG laser or CO2 laser can be used. Also, resistance welding is a processing method that joins two materials by applying pressure without melting the materials, and a strong joint is obtained by applying external pressure while heating the materials through a high-current electric circuit, and it can use equipment normally used for tab welding, so there is no need for additional equipment, ensuring economy.

[0042] According to an embodiment of the present invention, a first electrode active material layer may be provided on a surface of the first electrode collector facing an end portion 310 in the longitudinal direction of the second electrode. Specifically, referring to Fig. 2, the first electrode collector 101 may include a one-sided active material coated portion having a predetermined length, on which a first electrode active material layer 103 is provided, on a surface facing an end portion 310 in the longitudinal direction of the second electrode.

[0043] According to an embodiment of the present invention, the length of the single-sided active material coated portion in the longitudinal direction may be 20 mm or more and 200 mm or less. Specifically, referring to FIG. 2, the length (L6) of the single-sided active material coated portion provided on the surface of the first electrode collector 101 facing the longitudinal end 310 of the second electrode may be 25 mm or more, 30 mm or more, or 35 mm or more, and the length (L6) of the single-sided active material coated portion in the longitudinal direction may be 195 mm or less, 190 mm or less, or 185 mm or less. When the length (L6) of the single-sided active material coated portion in the longitudinal direction satisfies the above-mentioned range, the single-sided active material coated portion can be included in the jelly roll type electrode assembly, and the formation of an additional step in relation to the first electrode active material layer can be minimized, and the design capacity of the cell and the internal space of the battery case can be maintained constant. Here, the internal space of the battery case may refer to the internal volume of the battery case excluding the volume of the jelly roll type electrode assembly and the volume of the electrolyte contained therein.

[0044] According to one embodiment of the present invention, the welds may be formed at a predetermined distance from both ends of the single-sided active material coated portion in the longitudinal direction. Specifically, the separation distance (L5, L7) between the welds and both ends of the single-sided active material coated portion in the longitudinal direction may be 2 mm or more. When the separation distance between the welds and both ends of the single-sided active material coated portion in the longitudinal direction satisfies the above-mentioned range, it is easier to form the welds by laser welding or resistance welding.

[0045] FIG. 4 is a schematic diagram illustrating a step portion of a jelly-roll type electrode assembly according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating the jelly-roll type electrode assembly as a reference.

[0046] 4 and 5, the jelly roll type electrode assembly according to an embodiment of the present invention may include a step portion 60, which is an empty space formed in an area where the first electrode 100 covers the end portion 310 of the second electrode 300 in the longitudinal direction, and the disconnection prevention portion may be provided on an opposite surface of the first electrode current collector to the step portion 60, i.e., an opposite surface of the first electrode current collector to the end portion 310 of the second electrode in the longitudinal direction. Specifically, in the electrode assembly according to an embodiment of the present invention, the outermost first electrode 100 may extend longer than the end portion 310 of the second electrode 300 in the longitudinal direction and may be further wound outside the electrode assembly, the step portion 60, which is an area where a step is formed due to the thickness of the second electrode, may be formed on the side of the end portion 310 of the second electrode 300 in the longitudinal direction, and the disconnection prevention portion 50 may be provided on the opposite surface of the first electrode 100 to the end portion 60.

[0047] In other words, the jelly roll type electrode assembly may form a stacked structure of the first electrode / separator / second electrode / separator / first electrode when wound up. In this case, the length of the second electrode may be shorter than the remaining layers, and the outermost part of the wound electrode assembly may have a region forming a stacked structure of the first electrode / separator / vacant space / separator / first electrode, i.e., a step portion 60. In this case, the inner circumferential surface of the first electrode 100 to which the end portion 310 in the length direction of the second electrode 300 located at the outermost position is in contact may be subjected to stress concentration during contraction and expansion due to charging and discharging, and may cause cracks due to the stress concentration in the inner circumferential surface, which may cause an increase in resistance and problems in stability of the battery when the wire breaks. A break prevention tape 70 may be attached to the surface opposite to the step portion 60, but if the break prevention tape 70 does not have a sufficient thickness, the effect of preventing cracks in the electrode may be insignificant, and the effect of improving the resistance increase and stability problems of overcharging when a wire breaks may be poor. In contrast, the electrode assembly according to the present invention has a breakage prevention part 40 provided on the surface opposite to the surface facing the stepped portion 60 of the first electrode 100, and the breakage prevention part 40 includes a welded part (W) electrically connected to the first electrode collector 101, thereby preventing cracks and deformation of the electrode assembly due to stress concentration in the outermost negative electrode and providing an additional conductive path, thereby suppressing an increase in resistance even in the event of a breakage, and improving the stability of the battery.

[0048] According to one embodiment of the present invention, the first electrode may be a negative electrode and the second electrode may be a positive electrode. Specifically, the first electrode, which is the outermost layer of the electrode assembly, may be a negative electrode, and the electrode assembly may have a negative electrode outermost structure in which a negative electrode / separator / positive electrode / separator are wound. In other words, the outermost part of the jelly roll type electrode assembly may have an outer peripheral tab structure exposing the negative electrode.

[0049] According to one embodiment of the present invention, the first electrode may include a first electrode collector and a first electrode active material layer provided on the first electrode collector. Specifically, the first electrode may include a first electrode collector and a first electrode active material layer formed on one or both sides of the first electrode collector and including a first electrode active material. In other words, the first electrode active material layer is formed on a first electrode-coated portion of the first electrode collector, and the surface on which the first electrode active material layer is not provided can be referred to as a first electrode uncoated portion.

[0050] According to one embodiment of the present invention, the first electrode collector may include a first electrode coated portion on which a first electrode active material layer is formed and a first electrode uncoated portion on which the first electrode active material layer is not formed, and may include a first electrode tab on the first electrode uncoated portion. Specifically, the first electrode collector may include a first electrode uncoated portion, and may include a first electrode tab formed in the first electrode uncoated portion. Thus, the manufactured electrode assembly may include one or more first electrode tabs.

[0051] According to one embodiment of the present invention, the first electrode active material layer may include a first electrode active material including at least one selected from the group consisting of a silicon-based material and a carbon-based material. The first electrode active material layer may further include a first electrode conductive material and a first electrode binder, and the first electrode active material, the first electrode conductive material, and the first electrode binder may be any material used in the art as a negative electrode active material, a negative electrode conductive material, and a negative electrode binder, without any limitations.

[0052] According to one embodiment of the present invention, the first electrode collector is not particularly limited as long as it does not cause a chemical change in the battery and has electrical conductivity. For example, the first electrode collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that easily adsorbs carbon, such as copper or nickel, may be used as the first electrode collector.

[0053] The thickness of the first electrode current collector may be 8 μm or more and 180 μm or less, but the thickness of the first electrode current collector is not limited thereto.

[0054] According to one embodiment of the present invention, the first electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0055] According to one embodiment of the present invention, the first electrode conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and examples of the conductive material that may be used include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0056] According to one embodiment of the present invention, the second electrode may include a second electrode collector and a second electrode active material layer provided on the second electrode collector. Specifically, the second electrode may include a second electrode collector and a second electrode active material layer formed on one or both sides of the second electrode collector and including a second electrode active material. In other words, the second electrode active material layer is formed on a second electrode-coated portion of the second electrode collector, and the surface on which the second electrode active material layer is not provided can be referred to as a second electrode uncoated portion.

[0057] According to one embodiment of the present invention, the second electrode collector may include a second electrode coated portion on which a second electrode active material layer is formed and a second electrode uncoated portion on which a second electrode active material layer is not formed, and may include a second electrode tab on the second electrode uncoated portion. Specifically, the second electrode collector may include a second electrode uncoated portion, and may include a second electrode tab formed in the second electrode uncoated portion. Thus, the manufactured electrode assembly may include one or more second electrode tabs.

[0058] According to one embodiment of the present invention, the second electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. Specifically, the second electrode current collector may be made of stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like.

[0059] The second electrode current collector may have a thickness of 60 μm to 200 μm, and may have fine irregularities on the surface of the second electrode current collector to enhance the adhesive strength of the second electrode active material. For example, the second electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0060] According to one embodiment of the present invention, the second electrode active material may be a commonly used positive electrode active material. Specifically, the second electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; 1+x Mn 2-x O4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M y Lithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦y≦0.3 is satisfied); 2-z M z Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese oxide represented by Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and 0.01≦z≦0.1 is satisfied), or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The second electrode may be Li-metal.

[0061] According to one embodiment of the present invention, the second electrode active material layer may further include a second electrode conductive material and a second electrode binder. The second electrode conductive material is used to impart electrical conductivity to the electrode, and may be used without any particular limitation as long as it has electronic conductivity without causing a chemical change in the battery that is constructed. Specifically, the second electrode conductive material may be graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one or a mixture of two or more of these may be used.

[0062] The second electrode binder serves to improve adhesion between the second electrode active material particles and adhesion between the second electrode active material and the second electrode current collector.Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof, and one or more of these may be used alone or in combination.

[0063] According to an embodiment of the present invention, the end of the second electrode in the length direction may be formed at the same position of the second electrode collector and the second electrode active material layer. In other words, the end of the second electrode in the length direction may be a free edge. Here, the free edge shape refers to a shape in which the end of the electrode active material layer and the end of the electrode collector coincide with each other, and may include a case in which the end of the length direction coincides completely with a plane perpendicular to the length direction, as well as a case in which there is an error in the process and measurement. That is, the jelly roll type electrode assembly according to an embodiment of the present invention may have a structure in which the end of the second electrode in the length direction, which is in the free edge shape, is covered by the first electrode, which is the outermost layer, and may include a step portion, which is an empty space, formed in a region where the first electrode covers the second end of the second electrode.

[0064] 4 and 5, the first electrode 100 is present at the outermost part of the jelly roll type electrode assembly 1000, and the first electrode 100 may include a non-coating area and have first electrode active material layers 102 and 103 on both sides of a first electrode collector 101. Meanwhile, the second electrode 300 is present at the outermost part of the electrode assembly 1000, and the second electrode 300 may include second electrode active material layers 302 and 303 on both sides of a second electrode collector 301, but may not include a non-coating area. In other words, the second electrode may have a free edge shape in which the ends of the second electrode collector and the second electrode active material layer are aligned. That is, the lengthwise end 310 of the second electrode 300 may include ends of the second electrode active material layers 302 and 303 and an end of the second electrode current collector 301 having the same length in the length direction, or the lengthwise end 310 of the second electrode 300 may coincide with the ends of the second electrode active material layers 302 and 303 and the end of the second electrode current collector 301. Meanwhile, according to one embodiment of the present invention, a non-coated portion on a surface of the first electrode 100 opposite to the surface facing the end of the lengthwise end 310 of the second electrode 300 may further include a breakage prevention tape 70 attached to reduce the possibility of short circuit or crack occurrence due to stress concentration in the region.

[0065] According to an embodiment of the present invention, the jelly roll type electrode assembly may further include a plurality of separators. For example, the jelly roll type electrode assembly may have a structure in which a first electrode / separator / second electrode / separator are sequentially laminated. The separator separates the first electrode and the second electrode and provides a path for lithium ion movement. Any separator that is generally used as a separator in a secondary battery may be used without particular limitation. In particular, it is preferable that the separator has low resistance to ion movement of the electrolyte and has excellent electrolyte moisture absorption ability. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. In addition, a normal porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, or the like may be used. The separator may have a thickness of typically 10 μm to 20 μm. In order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material may be used, and the separator may be selectively used as a single-layer or multi-layer structure.

[0066] One embodiment of the present invention provides a secondary battery including the jelly-roll type electrode assembly; and a battery case for accommodating the electrode assembly, wherein the contents included in the jelly-roll type electrode assembly are as described above.

[0067] According to one embodiment of the present invention, the secondary battery may include a cap assembly coupled to an opening of the battery case, and the cap assembly may include a top cap, a safety vent, and a current interrupting element.

[0068] According to one embodiment of the present invention, the first electrode may be in direct contact with an inner surface of the battery case, and the battery case may serve as a first electrode terminal.

[0069] According to one embodiment of the present invention, an electrolyte may be included inside the battery case. Specifically, the electrolyte may be, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used in manufacturing a lithium secondary battery. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0070] According to one embodiment of the present invention, the non-aqueous organic solvent may be, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, or ethyl propionate.

[0071] According to one embodiment of the present invention, the metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt is F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 -, CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0072] According to one embodiment of the present invention, in addition to the constituent components of the electrolyte, the electrolyte may further contain one or more additives such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0073] According to one embodiment of the present invention, the battery case may be cylindrical. That is, the jelly roll type electrode assembly according to the present invention may be housed in a cylindrical battery case, and since the battery case containing the assembly including the first electrode, the separator, and the second electrode, the cap assembly, and the electrolyte has a cylindrical shape, the shape of the manufactured secondary battery itself may be cylindrical.

[0074] Although preferred embodiments have been presented above to aid in understanding the present invention, the above-described embodiments are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description, and it is natural that such changes and modifications fall within the scope of the accompanying claims.

Claims

1. A jelly roll type electrode assembly in which a first electrode, a separator, and a second electrode are stacked and wound up, the second electrode includes a second electrode current collector; and a second electrode active material layer provided on at least one surface of the second electrode current collector, the first electrode includes a first electrode collector; a first electrode active material layer provided on at least one surface of the first electrode collector; a disconnection prevention portion provided on a surface of the first electrode collector opposite a surface facing an end portion of the second electrode in a longitudinal direction; and a weld portion electrically connecting the first electrode collector and the disconnection prevention portion, a breakage prevention portion having a lengthwise end portion that does not coincide with a lengthwise end portion of the second electrode;

2. The jelly-roll type electrode assembly according to claim 1 , wherein the breakage prevention portion is made of the same material as the first electrode current collector.

3. The jelly-roll type electrode assembly according to claim 1 , wherein a longitudinal end of the second electrode is located between both longitudinal ends of the breakage prevention part.

4. the first electrode further includes a first electrode tab provided at an end of the first electrode in a longitudinal direction, The jelly roll type electrode assembly of claim 1 , wherein the breakage prevention portion is provided between an end portion of the first electrode active material layer in a longitudinal direction and the first electrode tab.

5. The jelly roll type electrode assembly of claim 4 , wherein the first electrode tab is provided on a surface of the first electrode collector opposite to a surface facing an end of the second electrode in the longitudinal direction.

6. The breakage prevention portion is a longitudinal end portion of the first electrode active material layer provided on a surface of the first electrode collector opposite to a longitudinal end portion of the second electrode; 2. The jelly roll type electrode assembly according to claim 1, wherein the second electrode is provided between the first electrode tab and a first electrode tab provided on a surface of the first electrode collector opposite to a surface facing the longitudinal end of the second electrode.

7. 2 . The jelly roll type electrode assembly of claim 1 , wherein the length of the breakage prevention part in the winding axis direction is 50% or more and 100% or less of the length of the first electrode current collector in the winding axis direction.

8. The jelly-roll type electrode assembly of claim 1 , wherein the welded portion does not overlap an end portion of the second electrode in the longitudinal direction.

9. The welded portion is provided in plurality, The jelly roll type electrode assembly of claim 1 , wherein the longitudinal end of the second electrode is located between the plurality of welds.

10. The welded portion is provided in plurality, The jelly-roll type electrode assembly of claim 1 , wherein the welds are symmetrically formed with respect to each other.

11. 2 . The jelly-roll type electrode assembly of claim 1 , wherein the welded portion comprises the first electrode active material layer provided on a surface of the first electrode current collector facing an end portion of the second electrode in the longitudinal direction.

12. 2 . The jelly-roll type electrode assembly of claim 1 , wherein the welded portion does not include the first electrode active material layer on a surface of the first electrode current collector facing an end portion in the longitudinal direction of the second electrode.

13. 2. The jelly roll type electrode assembly of claim 1, wherein the first electrode extends longer than a longitudinal end of the second electrode and is further wound outside the jelly roll type electrode assembly.

14. The jelly roll type electrode assembly of claim 1 , wherein the second electrode has a longitudinal end at a position where the second electrode current collector and the second electrode active material layer are aligned.

15. 2. The jelly roll type electrode assembly of claim 1, wherein the first electrode is a negative electrode and the second electrode is a positive electrode.

16. The jelly roll type electrode assembly according to any one of claims 1 to 15; and A battery case for housing the jelly-roll type electrode assembly. A secondary battery comprising:

17. The secondary battery according to claim 16 , wherein the battery case is cylindrical.

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