Jelly-roll type electrode assembly, method for manufacturing the jelly-roll type electrode assembly, and secondary battery including the same

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to a jelly-roll electrode assembly, a method for manufacturing the jelly-roll electrode assembly, and a secondary battery including the same, and more particularly to a jelly-roll electrode assembly including a flexible film heated by a heating means inserted into a hollow core of the jelly-roll electrode assembly, a method for manufacturing the jelly-roll electrode assembly, and a cylindrical secondary battery including the same. [Background technology]

[0002] In the case of cylindrical batteries, a jelly roll-shaped electrode assembly is manufactured by winding a long electrode having 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 core of the electrode assembly increases significantly.

[0003] Meanwhile, the core of a cylindrical battery is a space where a winding core used for winding a jelly-roll electrode assembly is located, and there is a space, i.e., a hollow space, in the core that is used during the assembly process of the cylindrical battery, such as the process of inserting the jelly-roll electrode assembly into a battery case and the welding process.

[0004] Recently, with the increase in low resistance / high capacity designs, jelly roll-type electrode assemblies are increasingly including multiple tabs or containing silicon-based active materials. As a result, the electrode assembly is more likely to deform due to contraction / expansion, and in particular, core deformation, i.e., the hollow core portion collapses without maintaining its original shape, resulting in a decrease in battery life. In addition, if the separator between the negative and positive electrodes is damaged, the negative and positive electrodes may come into direct contact with each other, resulting in an internal short circuit, which may cause heat generation and fire.

[0005] In order to solve the problems of battery life reduction, separator damage, and internal short circuit occurrence due to deformation of the electrode assembly, it is necessary to develop a technology that can support the hollow core of the relevant region so that it maintains its original shape and suppresses the occurrence of internal short circuit. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a jelly-roll-type electrode assembly with a modified design, a method for manufacturing the jelly-roll-type electrode assembly, and a secondary battery including the same.

[0007] 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]

[0008] One embodiment of the present invention is a jelly roll-type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound, wherein a core portion of the jelly roll-type electrode assembly includes a flexible film disposed between the first separator and the second separator, and the length of the flexible film in the longitudinal direction is 100% to 150% of the circumference of the inner circumferential surface of the jelly roll-type electrode assembly (100%), and the flexible film is heated by a heating means inserted into the hollow of the core portion of the jelly roll-type electrode assembly, and the tensile strength of the heated flexible film is 18 kgf / mm 2 (176.4N / mm 2 ) or more 25kgf / mm 2 (245N / mm 2 ) The present invention provides a jelly roll type electrode assembly having the following structure:

[0009] Another embodiment of the present invention is a method for manufacturing a jelly-roll type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound, the method comprising: (a) winding the first separator and the second separator; (b) inserting a flexible film between the first separator and the second separator; (c) inserting the negative electrode; (d) inserting the positive electrode; and (e) heating the jelly-roll type electrode assembly by a heating means inserted into a hollow core of the jelly-roll type electrode assembly, wherein the length of the flexible film in the longitudinal direction is 100% to 150% of the circumference of the inner circumferential surface of the jelly-roll type electrode assembly (100%), and the heated flexible film has a tensile strength of 18 kgf / mm. 2 (176.4N / mm 2 ) or more 25kgf / mm 2 (245N / mm 2 The present invention provides a method for manufacturing a jelly-roll type electrode assembly and a jelly-roll type electrode assembly manufactured by the method, which are as follows:

[0010] Another 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. [Effects of the Invention]

[0011] The jelly roll-type electrode assembly according to an embodiment of the present invention includes a flexible film that is heated by a heating means inserted into the hollow core and has a certain level of rigidity. This supports the hollow core to maintain its original shape against deformation of the electrode assembly due to contraction / expansion of the electrodes during charge / discharge of the battery. This prevents damage to the positive electrode and separator and prevents internal short circuits between the positive electrode and the negative electrode, thereby improving the safety and lifespan of the battery.

[0012] A method for manufacturing a jelly roll electrode assembly according to an embodiment of the present invention can more simply manufacture a jelly roll electrode assembly including a flexible film having a certain level of rigidity after heating, and the rigidity of the flexible film before heating is suitable for a continuous process using existing roll-to-roll processing equipment, thereby ensuring productivity and economy.

[0013] In addition, the secondary battery according to the present invention can prevent damage to the positive electrode and separator and internal short circuit between the positive electrode and negative electrode by supporting the electrode assembly so that the hollow core maintains its original shape even when the electrode assembly is deformed due to contraction / expansion of the electrodes during charging / discharging of the battery, thereby improving the safety and life characteristics of the battery.

[0014] The effects of the present invention are not limited to those described above, and effects not mentioned above will be apparent to those skilled in the art from this specification and the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1A and 1B are diagrams illustrating a jelly-roll type electrode assembly including a flexible film according to an embodiment of the present invention. [Figure 2] 1A and 1B are schematic diagrams illustrating a method for manufacturing a jelly-roll type electrode assembly including a flexible film according to an embodiment of the present invention. [Figure 3] 10 is a CT image showing the long-term cycle evaluation results of the jelly-roll type electrode assemblies according to Examples 1 and 2. [Figure 4] 10 is a CT image showing the long-term cycle evaluation results of the jelly-roll type electrode assemblies according to Examples 1 and 2. [Figure 5] 10 is a CT image showing the results of a long-term cycle evaluation of jelly-roll type electrode assemblies according to Comparative Examples 1 to 3. [Figure 6] 10 is a CT image showing the results of a long-term cycle evaluation of jelly-roll type electrode assemblies according to Comparative Examples 1 to 3. [Figure 7]10 is a CT image showing the results of a long-term cycle evaluation of jelly-roll type electrode assemblies according to Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0016] Throughout this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless otherwise specified.

[0017] Throughout this specification, when a member is said to be located "on" another member, this includes not only when the member is in contact with the other member, but also when there is another member between the two members.

[0018] Throughout this specification, the term "flexible film" refers to a film having a certain level of rigidity required for easy winding of a jelly roll type electrode assembly, i.e., a rigidity of at least a specific value, and is 16 kgf / mm 2 (156.8N / mm 2 ) means a film having a tensile strength of:

[0019] In one embodiment of the present invention, a jelly roll-type electrode assembly is provided in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound up. The core of the jelly roll-type electrode assembly includes a flexible film disposed between the first separator and the second separator, and the length of the flexible film in the longitudinal direction is 100% to 150% of the circumference of the inner circumferential surface of the jelly roll-type electrode assembly (100%). The flexible film is heated by a heating means inserted into the hollow of the core of the jelly roll-type electrode assembly, and the tensile strength of the heated flexible film is 18 kgf / mm. 2 (176.4N / mm 2 ) or more 25kgf / mm 2 (245N / mm 2 ) The present invention provides a jelly roll type electrode assembly having the following characteristics.

[0020] A jelly roll-type electrode assembly according to an embodiment of the present invention includes a flexible film that has a certain level of rigidity after being heated by an insertion means in the hollow of the core. This supports the hollow of the core to maintain its original shape against deformation of the electrode assembly due to contraction / expansion of the electrodes during charge / discharge of the battery, thereby preventing damage to the positive electrode and separator and preventing internal short circuits between the positive electrode and negative electrode, thereby improving the safety and life characteristics of the battery.

[0021] According to one embodiment of the present invention, the core portion of the jelly roll-type electrode assembly may include a flexible film disposed between the first separator and the second separator. Here, the "core portion" refers to a hollow portion located on a winding shaft of the electrode assembly and a region including a portion of the laminated structure of the wound electrode assembly, and may refer to a region from one longitudinal end of the negative electrode located at the innermost portion of the electrode assembly to the ends of the first separator and the second separator. The core portion may refer to a region within three turns from one longitudinal end of the negative electrode.

[0022] According to an embodiment of the present invention, the core portion of the jelly roll-type electrode assembly may not include the positive electrode and the negative electrode, that is, the core portion of the jelly roll-type electrode assembly may be a region including a first separator, a flexible film, and a second separator.

[0023] According to an embodiment of the present invention, one side and the other side of the flexible film may not be in direct contact with the negative electrode or the positive electrode, in other words, one side and the other side of the flexible film may be in direct contact with a separator, and the separator may be a first separator and a second separator.

[0024] In this case, even when a flexible film is included in the core portion of the jelly roll-type electrode assembly, problems such as a decrease in charge / discharge capacity due to a decrease in the area of ​​the negative electrode that receives lithium ions or an impregnation inhibition of the electrolyte can be minimized.

[0025] According to an embodiment of the present invention, the core part of the jelly roll-type electrode assembly includes a flexible film disposed between the first separator and the second separator, and may include a first region having a stacked structure of the first separator and the second separator, and a second region having a stacked structure of the first separator, the flexible film, and the second separator.

[0026] FIG. 1 is a diagram illustrating a jelly-roll type electrode assembly including a flexible film according to an embodiment of the present invention, and FIG. 2 is a schematic diagram illustrating a method for manufacturing a jelly-roll type electrode assembly including a flexible film according to an embodiment of the present invention.

[0027] 1 and 2, the core portion of the jelly roll-type electrode assembly may include a first region having a stacked structure of a first separator and a second separator, and a second region having a stacked structure of the first separator, a flexible film, and a second separator. Specifically, the core portion of the jelly roll-type electrode assembly may include a flexible film disposed between the first separator and the second separator, thereby including the first region having a stacked structure of the first separator and the second separator, and the second region having a stacked structure of the first separator, the flexible film, and a second separator. More specifically, the longitudinal length of the first region is L1, and the longitudinal length of the second region is L2. The core portion C refers to a region having a longitudinal length that is the sum of the longitudinal length L1 of the first region and the longitudinal length L2 of the second region, i.e., L1 + L2, and L3 may be 0.

[0028] In this case, the flexible film and one longitudinal end of the negative electrode are in contact with each other, and as described below, the thickness range of the flexible film may be adjusted to minimize the step, i.e., the occurrence of local problems such as the formation of a step due to the thickness difference between the flexible film and the negative electrode and lithium deposition in the step-forming region may be minimized.

[0029] According to one embodiment of the present invention, the length L1 of the first region in the longitudinal direction may be 1 turn or more and 1.7 turns or less. Specifically, the length L1 of the first region in the longitudinal direction may be 1.1 turns or more, 1.2 turns or more, or 1.3 turns or more, or may be 1.6 turns or less, 1.5 turns or less, or 1.4 turns or less.

[0030] Here, one turn refers to the length of the separator included in the electrode assembly required to be wound 360° from a reference point, and the length may be determined depending on the outer diameter of the winding core used to wind the electrode assembly, the thicknesses of the first separator, the flexible film, and the second separator, and the number of turns of the first separator, the flexible film, and the second separator located inside. For example, one turn may refer to the length required to wind the first separator 360° from the longitudinal end of the first separator in the direction in which the jelly roll-type electrode assembly is wound.

[0031] When the longitudinal length of the first region satisfies the above-described range, the electrode assembly can be more easily wound by adjusting the distance between one longitudinal end of the separator and one longitudinal end of the flexible film. When the longitudinal length of the first region is less than one turn, the tension for continuous winding around a winding core may be insufficient.

[0032] According to an embodiment of the present invention, the core portion of the jelly roll-type electrode assembly may further include a third region having a stacked structure of a first separator and a second separator. Specifically, the core portion of the jelly roll-type electrode assembly may include a first region having a stacked structure of the first separator and the second separator, a second region having a stacked structure of the first separator, a flexible film, and the second separator, and a third region having a stacked structure of the first separator and the second separator. More specifically, the longitudinal length of the first region may be L1, the longitudinal length of the second region may be L2, and the longitudinal length of the third region may be L3. The core portion C may refer to a region having a longitudinal length of L1 + L2 + L3, which is the sum of the longitudinal length L1 of the first region, the longitudinal length L2 of the second region, and the longitudinal length L3 of the third region, where L3 may be greater than 0.

[0033] In this case, the flexible film and one longitudinal end of the negative electrode do not contact each other, and as described below, by adjusting the distance between the flexible film and one longitudinal end of the negative electrode, damage to the separator caused by the electrode or the end of the flexible film can be minimized even when the electrode assembly contracts / expands.

[0034] According to an embodiment of the present invention, the length of the flexible film in the longitudinal direction may be 100% to 150% of the 100% circumference of the inner circumferential surface of the jelly-roll-type electrode assembly. Specifically, the length of the flexible film in the longitudinal direction may be 105% to 110%, 115% to 120% of the 100% circumference of the inner circumferential surface of the jelly-roll-type electrode assembly, and may be 145%, 140%, 135%, or 130% or less.

[0035] Here, the "perimeter of the inner peripheral surface" refers to a virtual circumference having a radius equal to the maximum distance from the winding shaft of the electrode assembly to the innermost layer that contacts the hollow of the electrode assembly, and the length may be determined by the outer diameter of the winding core used to wind the electrode assembly. For example, the perimeter of the inner peripheral surface may have a value of approximately 10 mm.

[0036] According to one embodiment of the present invention, the length of the flexible film in the longitudinal direction may be 0.9 turns or more and 1.4 turns or less. Specifically, the distance between one end of the flexible film in the longitudinal direction and one end of the negative electrode in the longitudinal direction may be 1 turn or more or 1.1 turns or more and 1.3 turns or less or 1.2 turns or less. Referring to FIG. 2, the length of the flexible film in the longitudinal direction may be the same as the length L2 of the second region in the longitudinal direction.

[0037] When the longitudinal length of the flexible film satisfies the above-mentioned range, the core support effect of the heated flexible film is better, and the decrease in battery capacity and energy density can be minimized, thereby preventing deterioration of electrochemical properties.

[0038] According to one embodiment of the present invention, the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode may be 0.5 turns or less. Specifically, the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode may be 0.4 turns or less, or 0.3 turns or less. Referring to FIG. 2, the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode may be equal to the longitudinal length L3 of the third region.

[0039] In this case, one end of the flexible film and the negative electrode in the longitudinal direction may be in contact with each other, and the thickness of the flexible film and the negative electrode may be adjusted to minimize a step due to a difference in thickness between the electrode and the flexible film.

[0040] According to one embodiment of the present invention, the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode may be 0.3 turns or more and 0.7 turns or less. Specifically, the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode may be 0.4 turns or more or 0.5 turns or more, or may be 0.6 turns or less or 0.5 turns or less. Referring to FIG. 2, the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode may be the same as the longitudinal length L3 of the third region.

[0041] In this case, one longitudinal end of the flexible film and one longitudinal end of the negative electrode may not be in contact with each other, and by adjusting the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode, damage to the separator caused by the electrode or the end of the flexible film can be minimized even when the electrode assembly contracts / expands.

[0042] According to an embodiment of the present invention, the flexible film may further include a fixing member on at least one surface. Specifically, the fixing member is for minimizing sliding of the flexible film and may be an adhesive or tape. When the fixing member is further included, damage to the separator caused by the electrodes or the edges of the flexible film may be minimized even when the electrode assembly contracts / expands or the flexible film slides.

[0043] According to an embodiment of the present invention, the flexible film may be heated by a heating means inserted into a hollow core of the jelly-roll type electrode assembly.

[0044] According to one embodiment of the present invention, the tensile strength of the flexible film before heating is 9 kgf / mm 2 (88.2N / mm 2 ) or more 16kgf / mm 2 (156.8N / mm 2 Specifically, the tensile strength of the flexible film before heating may be 10 kgf / mm or less. 2(98N / mm 2 ) or more, 11kgf / mm 2 (107.8N / mm 2 ) or more or 12kgf / mm 2 (117.6N / mm 2 ) or more, and 15 kgf / mm 2 (147N / mm 2 ) or less, 14kgf / mm 2 (137.2N / mm 2 ) or less or 13kgf / mm 2 (127.4N / mm 2 ) or less.

[0045] According to an embodiment of the present invention, the tensile strength of the flexible film may increase after heating. Specifically, the tensile strength of the flexible film may increase due to modification of the flexible film after one or both sides are heated, and the rate of increase in the tensile strength may vary depending on the degree of heating of the flexible film, i.e., the heated area, heating temperature, and heating time.

[0046] According to one embodiment of the present invention, the tensile strength of the heated flexible film may be 150% or more and 200% or less, based on 100% of the tensile strength before heating. Specifically, the tensile strength of the heated flexible film may be 160% or more, 170% or more, or 180% or more, or 190% or less, 180% or less, or 170% or less, based on 100% of the tensile strength before heating.

[0047] According to one embodiment of the present invention, the tensile strength of the heated flexible film is 18 kgf / mm 2 (176.4N / mm 2 ) or more 25kgf / mm 2 (245N / mm 2 Specifically, the tensile strength of the heated flexible film may be 19 kgf / mm or less. 2 (186.2N / mm 2 ) or more, 20kgf / mm 2 (196N / mm 2 ) or more or 21kgf / mm 2(205.8N / mm 2 ) or more, and 24 kgf / mm 2 (235.2N / mm 2 ) or less, 23kgf / mm 2 (225.4N / mm 2 ) or less or 22kgf / mm 2 (215.6N / mm 2 ) or less.

[0048] Here, the tensile strength of the flexible film can be measured by preparing a sample of the heated flexible film sample with a size of 20 mm x 100 mm and a thickness of 10 μm using a Universal Testing Machine (UTM) at room temperature and at a speed of 2 cm / min.

[0049] When the rigidity of the flexible film before heating satisfies the above-described range, the rigidity of the jelly-roll type electrode assembly including the flexible film is more suitable for a roll-to-roll process, thereby improving the productivity and economic efficiency of the jelly-roll type electrode assembly.

[0050] When the tensile strength of the heated flexible film satisfies the above-mentioned range, the effect of supporting the core by the heated flexible film is more excellent, and the electrode assembly can be produced in a continuous process using existing roll-to-roll process equipment, thereby ensuring productivity and economy.

[0051] According to an embodiment of the present invention, the heating means may be a reforming pin 200. Specifically, referring to FIG. 2(c), the heating means may be a reforming pin 200 that presses a separator (not shown) located in the hollow H of the core of the jelly roll electrode assembly 100 toward the inner circumferential surface of the core of the jelly roll electrode assembly 100 to form a cylindrical hollow, thereby shaping the jelly roll electrode assembly 100.

[0052] A pair of winding cores may be used in the winding process of a jelly roll electrode assembly. The electrode assembly is wound into a jelly roll shape around the winding cores, and then the electrode assembly is separated from the winding cores. Here, a separator membrane is present in the hollow of the core portion of the jelly roll electrode assembly, and the separator membrane is shaped to cross the hollow and correspond to the gap between the pair of winding cores used in the winding process. In order to remove the separator membrane and restore the center portion of the electrode assembly to its original shape, the center portion must be reformed using a reforming pin after the winding process of the electrode assembly.

[0053] When the heating means is a forming pin, the separation film that crosses the hollow of the core part of the jelly roll type electrode assembly can be removed after winding, thereby facilitating subsequent processes and improving the productivity of the electrode assembly. In addition, the degree of heating of the flexible film, i.e., the heating area, heating temperature, and heating time, can be controlled within specific ranges to ensure that the heated flexible film has a certain level of rigidity.

[0054] According to an embodiment of the present invention, the heating may be performed on one surface of the flexible film, specifically, the heating may be performed on the entire surface of the flexible film.

[0055] According to one embodiment of the present invention, the heating can be carried out at a temperature of 50° C. to 80° C. for a time of 5 seconds to 15 seconds.

[0056] A jelly roll-type electrode assembly including a flexible film having a certain level of rigidity can be manufactured by adjusting the degree of heating of the flexible film, i.e., the heating area, heating temperature, and heating time, within a specific range.

[0057] According to one embodiment of the present invention, the heating may be carried out at a temperature of 55° C. or more, 60° C. or more, or 65° C. or more, and may be carried out at a temperature of 75° C. or less, 70° C. or less, or 65° C. or less. For example, the heating may be carried out at a temperature of 60° C.

[0058] According to one embodiment of the present invention, the heating may be performed for a period of 5 to 15 seconds. Specifically, the heating may be performed for a period of 6 to 15 seconds, such as 6 to 14 seconds, 7 to 12 seconds, 8 to 11 seconds, or 14 to 13 seconds, 12 to 11 seconds. For example, the heating may be performed for 10 seconds.

[0059] When the above-described heating time and temperature conditions are satisfied, a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity can be more easily manufactured, and the core support effect of the heated flexible film can be more excellent.

[0060] On the other hand, excessive heating may cause shrinkage of the separator, and insufficient heating may result in an insufficient increase in the rigidity of the heated flexible film, resulting in poor support for the core.

[0061] According to an embodiment of the present invention, the core part of the jelly roll-type electrode assembly may have a longitudinal length of 2 to 3 turns. Specifically, the core part of the jelly roll-type electrode assembly may have a longitudinal length of 2.1 turns or more, 2.2 turns or more, 2.3 turns or more, 2.4 turns or more, or 2.5 turns or more, or may have a longitudinal length of 2.9 turns or less, 2.8 turns or less, 2.7 turns or less, 2.6 turns or less, or 2.5 turns or less.

[0062] Referring to Figure 2, the longitudinal length of the core portion may be the same as the sum of the longitudinal length L1 of the first region and the longitudinal length L2 of the second region, or the sum of the longitudinal length L1 of the first region, the longitudinal length L2 of the second region, and the longitudinal length L3 of the third region.

[0063] Here, one turn refers to the length required for 360° winding from a reference point of a separator included in an electrode assembly, and the length can be determined depending on the outer diameter of a winding core used for winding the electrode assembly, the thicknesses of the first separator, the flexible film, and the second separator, and the number of windings of the first separator, the flexible film, and the second separator located inside. For example, one turn may refer to the length required for 360° winding of the first separator from the longitudinal end of the first separator in the winding direction of the jelly roll-type electrode assembly.

[0064] When the length of the core in the longitudinal direction satisfies the above-mentioned range, sufficient space can be secured for arranging the flexible film, and the effect of supporting the core by the heated flexible film can be more excellent.

[0065] According to an embodiment of the present invention, the width of the flexible film may be 95% or more and 105% or less of the width of the jelly-roll-type electrode assembly (100%). Specifically, the width of the flexible film may be 96% or more, 97% or more, 98% or more, 99% or more, or 100% or more of the width of the jelly-roll-type electrode assembly (100%), and 104%, 103%, 102%, 101%, or 100% or less.

[0066] When the width of the flexible film satisfies the above-described range, the length of the flexible film can correspond to the width of the jelly-roll-type electrode assembly, which is advantageous for supporting the core of the jelly-roll-type electrode assembly and can provide an excellent effect of preventing deformation of the core.

[0067] If the flexible film is too narrow in the width direction, it may be less effective in preventing deformation of the core portion. On the other hand, if the flexible film is too exposed in the width direction of the jelly-roll type electrode assembly, the rate of defects may increase during the process of inserting the electrode assembly into a battery case, and local problems such as lithium deposition due to the formation of steps may occur.

[0068] According to one embodiment of the present invention, the flexible film may include at least one selected from polypropylene, polyethylene, polyester, and polyamide. Specifically, the flexible film may include at least one selected from polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and polyamide (PA). For example, the flexible film may include polypropylene (PP).

[0069] When the material of the flexible film is of the above-described type, the rigidity of the heated flexible film is sufficient to support the core of the jelly roll-type electrode assembly, and the rigidity of the flexible film before heating is more suitable for a roll-to-roll process, thereby improving the productivity and economic efficiency of the jelly roll-type electrode assembly.

[0070] According to one embodiment of the present invention, the thickness of the flexible film may be 5% to 20% based on 100% of the thickness of the negative electrode. Specifically, the thickness of the flexible film may be 6% to 6%, 7% to 8%, 9% to 10%, and 19%, 18%, 17%, 16%, or 15% based on 100% of the thickness of the negative electrode.

[0071] When the thickness of the flexible film satisfies the above-mentioned range, the step can be minimized by adjusting the thickness range of the flexible film, that is, the occurrence of local problems such as the formation of a step due to the thickness difference between the flexible film and the negative electrode and lithium deposition in the step-formed region can be minimized.

[0072] According to one embodiment of the present invention, the thickness of the flexible film may be 10 μm or more and 50 μm or less. Specifically, the thickness of the flexible film may be 15 μm or more, 20 μm or more, or 25 μm or more, and 45 μm or less, 40 μm or less, or 35 μm or less.

[0073] When the thickness of the flexible film satisfies the above-described range, the rigidity of the heated flexible film is sufficient to support the core of the jelly-roll electrode assembly, and the rigidity of the flexible film before heating is more suitable for a roll-to-roll process, thereby improving the productivity and economic efficiency of the jelly-roll electrode assembly.

[0074] According to an embodiment of the present invention, 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, and the positive electrode current collector and the positive electrode active material layer may have longitudinal ends at the same position. In other words, one longitudinal end of the positive electrode may have a free edge.

[0075] This reduces the area of ​​unnecessary uncoated portions of the positive electrode current collector, ensuring economic efficiency. Furthermore, since the slitting process can be performed after forming the active material layer on the electrode, the roll-to-roll process, which includes the slitting process and the winding process, can be performed more efficiently.

[0076] Here, "the same position" means that the longitudinal ends are the same, and may include cases where the ends are formed at substantially the same position due to process errors that may occur in the slitting process, etc.

[0077] According to one embodiment of the present invention, the positive electrode current collector includes a positive electrode ground portion on which a positive electrode active material is coated and a positive electrode uncoated portion on which no positive electrode active material is coated, and may include a tab on the positive electrode uncoated portion. Specifically, the positive electrode current collector may include a positive electrode uncoated portion and may include a positive electrode tab formed on the positive electrode uncoated portion.

[0078] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and specifically, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, etc. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, etc.

[0079] The positive electrode current collector typically has a thickness of 5 μm to 30 μm, and may have fine irregularities on its surface to enhance adhesion of the positive electrode active material. For example, the current collector may be in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0080] According to one embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound or a compound substituted with one or more transition metals, such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2); a lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+x Mn 2-x O4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-y M y O2 (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 zExamples of the lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides expressed as 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) 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 substituted with an alkaline earth metal ion. The positive electrode may be Li-metal.

[0081] According to one embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart conductivity to the electrode and may be any material that has electronic conductivity without causing chemical changes in the resulting battery. Specifically, the positive 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 fiber; metal powder or metal fiber, such as copper, nickel, aluminum, or silver; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives. These materials may be used alone or in combination.

[0082] The positive electrode binder improves the adhesive strength between particles of the positive electrode active material and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder 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. These may be used alone or in combination.

[0083] According to one embodiment of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on one or both sides of the negative electrode current collector and including a negative electrode active material. In other words, the negative electrode active material layer is formed on a negative electrode landed portion of the negative electrode current collector, and the surface not including the negative electrode active material layer may be referred to as a negative electrode uncoated portion.

[0084] According to one embodiment of the present invention, the negative electrode current collector includes a negative electrode grounded portion where a negative electrode active material layer is formed and a negative electrode uncoated portion where no negative electrode active material layer is formed, and may include a tab on the negative electrode uncoated portion. Specifically, the negative electrode current collector may include a negative electrode uncoated portion and a negative electrode tab formed on the negative electrode uncoated portion. Therefore, the manufactured electrode assembly may include one or more negative electrode tabs.

[0085] According to an embodiment of the present invention, the negative electrode active material layer may include a negative electrode active material including at least one selected from the group consisting of silicon-based materials and carbon-based materials. The negative electrode active material layer may further include a negative electrode conductive material and a negative electrode binder, and the negative electrode active material, negative electrode conductive material, and negative electrode binder may be materials commonly used in the relevant fields without limitation.

[0086] According to one embodiment of the present invention, the negative electrode current collector may be any material that is conductive without causing chemical changes in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-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 negative electrode current collector. The thickness of the negative electrode current collector may be from 5 μm to 30 μm, but is not limited thereto.

[0087] According to one embodiment of the present invention, the negative 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.

[0088] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it is conductive without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, fanace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used.

[0089] According to one embodiment of the present invention, the jelly roll electrode assembly may include multiple separators. For example, the jelly roll electrode assembly may have a structure in which a separator / anode / separator / cathode are stacked in this order. The separator separates the anode and cathode and provides a path for lithium ions to move. Any separator commonly used in secondary batteries may be used. A separator with low resistance to electrolyte ion movement and excellent electrolyte-containing capacity is preferred. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fiber or polyethylene terephthalate fiber, may also be used. The separator may be formed by coating a substrate layer of the above-described separator material with a slurry containing a ceramic component or a polymeric material to ensure heat resistance or mechanical strength, and may have a single-layer or multi-layer structure. The thickness of the separator may be, but is not limited to, 10 μm to 20 μm.

[0090] Another embodiment of the present invention is a method for manufacturing a jelly-roll type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound, the method comprising: (a) winding the first separator and the second separator; (b) inserting a flexible film between the first separator and the second separator; (c) inserting the negative electrode; (d) inserting the positive electrode; and (e) heating the jelly-roll type electrode assembly by a heating means inserted into a hollow core of the jelly-roll type electrode assembly, wherein the length of the flexible film in the longitudinal direction is 100% to 150% of the circumference of the inner circumferential surface of the jelly-roll type electrode assembly (100%), and the tensile strength of the flexible film is 18 kgf / mm 2 (176.4N / mm 2 ) or more 25kgf / mm 2 (245N / mm 2 ) A method for manufacturing a jelly-roll type electrode assembly and a jelly-roll type electrode assembly manufactured by the method are provided.

[0091] A method for manufacturing a jelly roll electrode assembly according to an embodiment of the present invention can more simply manufacture a jelly roll electrode assembly including a flexible film having a certain level of rigidity after heating, and the rigidity of the flexible film before heating is suitable for a continuous process using existing roll-to-roll processing equipment, thereby ensuring productivity and economy.

[0092] In addition, the jelly roll-type electrode assembly manufactured by the above manufacturing method includes a flexible film in the core portion that has a certain level of rigidity after heating. This allows the hollow core portion to maintain its original shape against deformation of the electrode assembly due to contraction / expansion of the electrodes during charging / discharging of the battery, thereby preventing damage to the positive electrode and separator and preventing internal short circuits between the positive electrode and negative electrode, thereby improving the safety and lifespan of the battery.

[0093] According to an embodiment of the present invention, the length of the flexible film in the longitudinal direction may be 100% to 150% of the 100% circumference of the inner circumferential surface of the jelly-roll-type electrode assembly. Specifically, the length of the flexible film in the longitudinal direction may be 105% to 110%, 115% to 120% of the 100% circumference of the inner circumferential surface of the jelly-roll-type electrode assembly, and may be 145%, 140%, 135%, or 130% or less.

[0094] When the longitudinal length of the flexible film satisfies the above-mentioned range, the core support effect of the heated flexible film is better, minimizing the decrease in battery capacity and energy density and preventing deterioration of electrochemical characteristics.

[0095] According to one embodiment of the present invention, the tensile strength of the heated flexible film is 18 kgf / mm 2 (176.4N / mm 2 ) or more 25kgf / mm 2 (245N / mm 2 Specifically, the tensile strength of the flexible film may be 19 kgf / mm or less. 2 (186.2N / mm 2 ) or more, 20kgf / mm 2 (196N / mm 2 ) or more or 21kgf / mm 2 (205.8N / mm 2 ) or more, and 24 kgf / mm 2 (235.2N / mm 2 ) or less, 23kgf / mm 2 (225.4N / mm 2 ) or less or 22kgf / mm 2 (215.6N / mm 2 ) or less.

[0096] When the tensile strength of the heated flexible film satisfies the above-mentioned range, the effect of supporting the core by the heated flexible film is more excellent, and the electrode assembly can be produced in a continuous process using existing roll-to-roll process equipment, thereby ensuring productivity and economy.

[0097] Here, the definitions of the perimeter of the core portion and the inner peripheral surface, the physical properties of the flexible film, i.e., the tensile strength of the flexible film before heating, the tensile strength increase rate, and the method for measuring the tensile strength of the flexible film, may be the same as those described above for the jelly-roll type electrode assembly. Also, the definitions of the first to third regions included in the core portion, the length L1 of the first region, the length L2 of the second region, the length L3 of the third region, and the length L1+L2+L3 of the core portion in the longitudinal direction may be the same as those described above for the jelly-roll type electrode assembly.

[0098] According to an embodiment of the present invention, the method for manufacturing the jelly-roll electrode assembly may be performed using a roll-to-roll process. Specifically, steps (a) to (d) may be performed using a roll-to-roll process in which a number of flexible metal foils are processed by moving them between rollers.

[0099] Here, the roll-to-roll method may refer to a method in which a roll on which a flexible and thin metal sheet-like electrode collector is wound is unwound to supply the electrode collector, an electrode slurry containing an electrode active material is applied to at least one surface of the electrode collector, and the electrode current collector is dried to form an electrode active material layer, and the processed electrode current collector is then rewound and collected by another roll.

[0100] Furthermore, the term "insertion" may refer to a series of insertion and winding processes, i.e., part of a winding process, performed in the manufacture of an electrode assembly using a roll-to-roll method. Specifically, it refers to a process of inserting a film or electrode to be further wound between a plurality of separators wound from one longitudinal end of a winding core along a portion of the longitudinal length thereof, or onto one surface of a plurality of separators wound partially around a winding core, and refers to a process of manufacturing an electrode assembly by continuously winding the inserted film or electrode together with the partially wound separators, and may include a slitting process of cutting a portion of the longitudinal length thereof, as necessary.

[0101] In the method for manufacturing a jelly roll electrode assembly according to an embodiment of the present invention, the jelly roll electrode assembly including the heated flexible film can be produced in a continuous process using existing roll-to-roll process equipment. In other words, in the method for manufacturing a jelly roll electrode assembly, step (b) can be performed after step (a) and before step (c), and therefore, all processes can be performed using a roll-to-roll process commonly used in the art.

[0102] That is, the method for manufacturing a jelly-roll type electrode assembly according to an embodiment of the present invention enables a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity after heating to be produced in a continuous process using existing roll-to-roll process equipment, thereby ensuring productivity and economy.

[0103] According to an embodiment of the present invention, the method for manufacturing the jelly-roll electrode assembly may include heating the jelly-roll electrode assembly using a heating means inserted into a hollow core of the jelly-roll electrode assembly. Specifically, the heating means may be a reform pin, and the reform pin may be any of those described above with respect to the jelly-roll electrode assembly.

[0104] According to one embodiment of the present invention, the reform pin may be inserted into the hollow of the electrode assembly and then repeatedly move forward and backward to push and remove the separation membrane that crosses the hollow of the core part to the innermost layer that contacts the hollow of the electrode assembly.

[0105] According to one embodiment of the present invention, the diameter of the reform pin may be 70% or more and 90% or less of the diameter of the hollow core portion (100%). Specifically, the diameter of the reform pin may be 75% or more, 80% or more, or 85% or more of the diameter of the hollow core portion (100%), or may be 85% or less, 80% or less, or 75% or less of the diameter of the hollow core portion (100%).

[0106] When the diameter of the reform pin satisfies the above-mentioned range, the degree of heating of the flexible film, i.e., the heating area, heating temperature, and heating time, can be adjusted within a specific range to ensure a certain level of rigidity of the heated flexible film, and protrusion of the separation membrane can be prevented when the reform pin is removed.

[0107] According to an embodiment of the present invention, the length of the reform pin may be 100% or more based on 100% of the width of the jelly-roll type electrode assembly.

[0108] When the length of the reform pin satisfies the above-mentioned range, the length of the reform pin can correspond to the widthwise length of the jelly roll-type electrode assembly, and the process of removing the separator that crosses the hollow of the core part of the electrode assembly and heating can be performed more uniformly across the entire widthwise length of the electrode assembly.

[0109] According to one embodiment of the present invention, the heating can be carried out at a temperature of 50° C. to 80° C. for a time of 5 seconds to 15 seconds.

[0110] According to one embodiment of the present invention, the heating may be carried out at a temperature of 55° C. or more, 60° C. or more, or 65° C. or more, and may be carried out at a temperature of 75° C. or less, 70° C. or less, or 65° C. or less. For example, the heating may be carried out at a temperature of 60° C.

[0111] According to one embodiment of the present invention, the heating may be performed for a period of 5 to 15 seconds. Specifically, the heating may be performed for a period of 6 to 15 seconds, such as 6 to 14 seconds, 7 to 13 seconds, 8 to 12 seconds, or 11 to 14 seconds. For example, the heating may be performed for 10 seconds.

[0112] When the above-described heating time and temperature conditions are satisfied, a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity can be more easily manufactured, and the supporting effect of the core part by the heated flexible film can be more excellent.

[0113] On the other hand, excessive heating may cause shrinkage of the separator, and insufficient heating may result in an insufficient increase in the rigidity of the heated flexible film, resulting in poor support for the core.

[0114] FIG. 2 is a schematic diagram of a method for manufacturing a jelly roll-type electrode assembly including a flexible film according to an embodiment of the present invention.

[0115] Referring to Figure 2, step (a) may involve winding up the first and second separators. After the first and second separators are wound up to a predetermined length around a winding core, step (b) may be carried out.

[0116] That is, a flexible film may be inserted between the first separator and the second separator wound to a predetermined length. Therefore, the core of the jelly roll-type electrode assembly does not include the positive electrode and the negative electrode, and one side and the other side of the flexible film may not be in direct contact with the negative electrode or the positive electrode. Here, the width, material, and thickness of the inserted flexible film may be the same as those described above for the jelly roll-type electrode assembly.

[0117] In step (b), the flexible film may have a predetermined length, and the core of the jelly-roll type electrode assembly including the flexible film may also have a predetermined length.

[0118] Then, steps (c) and (d) can be carried out sequentially.

[0119] According to an embodiment of the present invention, step (c) may involve inserting the negative electrode, specifically, inserting the negative electrode between the first separator and the second separator.

[0120] The flexible film and one longitudinal end of the negative electrode are not in contact with each other, and the distance between one longitudinal end of the flexible film and one longitudinal end of the negative electrode is adjusted, thereby minimizing damage to the separator caused by the electrode or the end of the flexible film when the electrode assembly contracts / expands.

[0121] Meanwhile, when one longitudinal end of the flexible film and the negative electrode contact each other, the thickness range of the flexible film may be adjusted to minimize the step, thereby minimizing the occurrence of local problems such as lithium deposition in the step-forming region.

[0122] Next, step (e) may be performed after steps (a) to (d). Specifically, after the jelly roll-type electrode assembly is wound, it may be heated by a heating means inserted into the hollow core portion. More specifically, when the heating means is a reform pin, the process of removing the separator traversing the hollow core portion of the electrode assembly and the heating may be performed simultaneously.

[0123] A method for manufacturing a jelly roll electrode assembly according to an embodiment of the present invention can more simply manufacture a jelly roll electrode assembly including a flexible film having a certain level of rigidity after heating, and the rigidity of the flexible film before heating is suitable for a continuous process using existing roll-to-roll processing equipment, thereby ensuring productivity and economy.

[0124] An embodiment of the present invention provides a jelly-roll type electrode assembly manufactured by the above-described method for manufacturing a jelly-roll type electrode assembly.

[0125] The jelly roll-type electrode assembly according to an embodiment of the present invention includes a core made of a flexible film that has a certain level of rigidity after heating. This allows the hollow core to maintain its original shape despite deformation of the electrode assembly due to contraction / expansion of the electrodes during charging / discharging of the battery. This prevents damage to the positive electrode and separator, and prevents internal short circuits between the positive electrode and the negative electrode, thereby improving the safety and lifespan of the battery.

[0126] An embodiment of the present invention provides a secondary battery including the jelly-roll type electrode assembly and a battery case for housing the electrode assembly. Specifically, the secondary battery may include the electrode assembly according to the above-described embodiment and a battery case for housing the electrode assembly.

[0127] The secondary battery according to the present invention can improve the safety and life characteristics of the battery by preventing damage to the positive electrode and separator and preventing internal short circuits between the positive electrode and negative electrode, as the hollow core maintains its original shape despite deformation of the electrode assembly due to contraction / expansion of the electrodes during charge / discharge of the battery.

[0128] According to an embodiment of the present invention, the battery case may be cylindrical. Specifically, the battery case may have a cylindrical shape, a square shape, a pouch shape, or the like depending on the application, but is not limited thereto.

[0129] According to one embodiment of the present invention, the interior of the battery case may contain an electrolyte. Specifically, the electrolyte may include, 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.

[0130] According to one embodiment of the present invention, the non-aqueous organic solvent may be an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethyl carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, ethyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, or ethyl propionate.

[0131] According to one embodiment of the present invention, the metal salt may be a lithium salt. The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte solution, and the anion of the lithium salt may be, for example, 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:

[0132] According to an embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives, such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate 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.

[0133] An embodiment of the present invention provides a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery, which has high capacity, high battery safety, and improved life characteristics, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0134] MODE FOR CARRYING OUT THE INVENTION

[0135] Hereinafter, the present invention will be described in detail based on examples in order to specifically explain the present invention. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples in this specification are provided to more completely explain the present invention to those skilled in the art.

[0136] Example

[0137] Example 1

[0138] Electrode assembly manufacturing

[0139] Li(Ni) as a cathode material 0.93 Co 0.01 Mn 0.03 Al0.03 A cathode active material slurry was prepared by adding O2, CNT as a cathode conductor, and polyvinylidene fluoride (PVdF) as a binder to N-methyl-2-pyrrolidone (NMP) in a weight ratio of 98.2:0.8:1.0. The cathode active material slurry was coated on an aluminum current collector with a thickness of 15 μm and a width of 64 mm, and then dried and rolled to form a cathode active material layer, preparing a cathode with a thickness of 175 μm.

[0140] Next, natural graphite (C, average particle size 10 μm, manufactured by POSCO Chemical Co., Ltd.) and SiO (average particle size (D 50 A negative electrode active material composition was prepared by mixing carbon black as a conductive material for the negative electrode active material and a mixture of styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as a first binder in a weight ratio of 98:1:1 (SiO 5 wt%). 7.8 g of distilled water was then added to 5 g of the negative electrode active material composition and stirred to prepare a negative electrode active material slurry. The negative electrode active material slurry was applied to a copper (Cu) metal thin film negative electrode current collector with a thickness of 10 μm and a width of 65 mm, and dried (drying temperature: 120°C, 1 minute) to form a negative electrode with an average thickness of 185 μm. The circulating air temperature was 60°C.

[0141] Then, a flexible film made of polypropylene (PP) material with a width of 65 mm, a length of 15 mm, and a thickness of 50 μm was prepared, and two separators made of polyethylene (PE) material with a thickness of 13 μm were prepared as the first and second separators. A sample of the flexible film with a size of 20 mm x 100 mm and a thickness of 10 μm was prepared, and the tensile strength measured at room temperature and a speed of 2 cm / min using a Universal Testing Machine (UTM) was 11 kgf / mm. 2 (107.8N / mm 2 ) was.

[0142] Next, a first separator and a second separator were sequentially arranged and wound around a 3.4 mm diameter core, and then the flexible film was inserted between the first and second separators and further wound. After the flexible film was fully wound, the negative electrode and the positive electrode were sequentially inserted and wound 6 mm apart from the flexible film. A jelly roll-type electrode assembly was manufactured by attaching and finishing PET sealing tape to the wound ends to wrap the outer periphery of the top and bottom ends of the jelly roll. Here, the inner periphery of the jelly roll-type electrode assembly was approximately 12 mm, and the length from the longitudinal end of the negative electrode to the longitudinal end of the first separator was approximately 15 mm.

[0143] Then, a 2.5 mm diameter reform pin equipped with a heater was inserted into the hollow of the electrode assembly, and the reform pin was repeatedly moved forward and backward to push out and remove the separator traversing the hollow of the core portion to the innermost layer in contact with the hollow of the electrode assembly. Here, the heater equipped on the reform pin was adjusted to 60°C, and the reforming was carried out for 10 seconds. Here, a sample of 20 mm x 100 mm and 10 μm thick was prepared from the heated flexible film, and the tensile strength was measured at room temperature and at a speed of 2 cm / min using a Universal Testing Machine (UTM) and was 18 kgf / mm. 2 (176.4N / mm 2 ) was.

[0144] Secondary battery manufacturing

[0145] The jelly roll type electrode assembly was inserted into a cylindrical battery case, and then ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) were mixed in a volume ratio of 20:50:30 to form a battery containing 1.3M (mol / dm 3 The cylindrical battery can was sealed with a cap assembly to manufacture a secondary battery.

[0146] Example 2

[0147] A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a polyethylene (PE) film was used as the flexible film.

[0148] Here, a sample of 20mm x 100mm and 10μm thick was prepared for the polyethylene (PE) film, and the tensile strength measured at room temperature and a speed of 2cm / min using a Universal Testing Machine (UTM) was 15kgf / mm 2 (147N / mm 2 ) and the tensile strength of the heated flexible film is 25 kgf / mm 2 (245N / mm 2 ) was.

[0149] Comparative Example 1

[0150] A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that the flexible film was not used.

[0151] Comparative Example 2

[0152] A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a PI (polyimide) film was used as the flexible film. A sample of the PI film with a size of 20 mm x 100 mm and a thickness of 10 μm was prepared, and the tensile strength was measured at room temperature and at a speed of 2 cm / min using a Universal Testing Machine (UTM). 2 (49N / mm 2 ) and the tensile strength of the heated flexible film is 10 kgf / mm 2 (98N / mm 2 ) was.

[0153] Comparative Example 3

[0154] A jelly-roll type electrode assembly and a secondary battery were manufactured in the same manner as in Example 1, except that a film having a length of 30 mm in the longitudinal direction was used as the flexible film.

[0155] Experimental Example

[0156] Experimental example 1: Evaluation of cycle safety

[0157] The secondary batteries manufactured in the examples and comparative examples were subjected to a cycle test at 25°C, 4.2-2.85 V, 0.5 C / 0.5 C, using an electrochemical charger / discharger. After 50 cycles, the cores were subjected to computed tomography (CT) to check for core deformation and evaluate cycle safety. The images are shown in Figures 3 to 7, respectively.

[0158] Experimental example 2: Life evaluation

[0159] In the examples and comparative examples, the secondary batteries were subjected to a lifespan evaluation using an electrochemical charger / discharger to evaluate the capacity retention rate. The secondary batteries were subjected to a cycle test at 4.2-2.85 V, 1 C / 1 C, and the capacity retention rate was measured every 100 cycles by charging / discharging at 0.2 C / 0.2 C (4.2-2.85 V). The results are shown in Table 1.

[0160] Lifetime retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at 1st cycle)} x 100 Experimental example 3: Measurement and evaluation of resistance increase rate

[0161] In Experimental Example 2, the capacity retention rate was measured by charging / discharging at 0.2 C / 0.2 C (4.2-2.85 V) every 100 cycles, and then the resistance was measured by discharging at 0.5 C pulse at SOC50, and the resistance increase rate was compared and analyzed. The results are shown in Table 1 below.

[0162] [Table 1]

[0163] 3 to 7, it was confirmed that the secondary battery according to one embodiment of the present invention includes a flexible film in the core portion, and after assembling the jelly-roll type electrode assembly, the rigidity of the flexible film is increased by heating using a reforming pin, thereby improving core deformation. In addition, it was confirmed that the secondary batteries according to Examples 1 and 2 can achieve the designed capacity and also improve the lifespan and resistance characteristics. On the other hand, the secondary batteries according to Comparative Examples 1 to 3, which do not include a flexible film or have a tensile strength of 18 kgf / mm even after heating, 2 (176.4N / mm 2 ) In other words, when a film with low rigidity is used, core deformation occurs, which increases the internal resistance of the battery and reduces the lifespan characteristics. Also, when the longitudinal length of the flexible film is too long, the longitudinal length of the electrode decreases, which reduces the designed capacity and the actual discharge capacity.

[0164] Therefore, the jelly roll-type electrode assembly and the secondary battery including the same according to an embodiment of the present invention include a flexible film having a certain level of rigidity after being heated by a heating means inserted into the hollow core portion. This allows the hollow core portion to maintain its original shape against deformation of the electrode assembly due to contraction / expansion of the electrodes during charging / discharging of the battery, thereby preventing damage to the positive electrode and separator and preventing internal short circuits between the positive electrode and negative electrode, thereby improving the safety and life characteristics of the battery.

[0165] The above detailed description exemplifies and explains the present invention. Furthermore, the above content merely illustrates and describes preferred embodiments of the present invention. As stated above, the present invention can be used in various other combinations, modifications, and environments, and changes or modifications can be made within the scope of the inventive concept disclosed herein, the scope of equivalents to the above disclosure, and / or the skill or knowledge of the relevant art. Therefore, the above detailed description of the invention is not intended to limit the present invention to the disclosed embodiments. Furthermore, the appended claims should be construed to include other embodiments. [Industrial Applicability]

[0166] The jelly roll-type electrode assembly and secondary battery including the same according to an embodiment of the present invention include a flexible film having a certain level of rigidity after being heated by a heating means inserted into the hollow core portion. This allows the hollow core portion to maintain its original shape against deformation of the electrode assembly due to contraction / expansion of the electrodes during charging / discharging of the battery, thereby preventing damage to the positive electrode and separator and preventing internal short circuits between the positive electrode and negative electrode, thereby improving the safety and life characteristics of the battery. [Explanation of symbols]

[0167] 10 First separation membrane 20 negative electrode 30 Second separation membrane 40 positive electrode 50 Flexible Film 100 Jelly roll type electrode assembly 200 Reform Pins L1 Longitudinal length of the first area L2 Longitudinal length of the second region L3 Longitudinal length of the third region C Core H Hollow core

Claims

1. A jelly roll type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound, a core portion of the jelly-roll type electrode assembly including a flexible film disposed between the first separator and the second separator; a length in a longitudinal direction of the flexible film is 100% to 150% based on 100% of a circumference of an inner circumferential surface of the jelly-roll type electrode assembly; The flexible film is heated by a heating means inserted into the hollow core of the jelly roll type electrode assembly, The tensile strength of the heated flexible film is 18 kgf / mm ２ (176.4N / mm ２ ) or more 25kgf / mm ２ (245N / mm ２ ) or less.

2. 2. The jelly roll type electrode assembly according to claim 1, wherein the heating means is a reform pin.

3. 2. The jelly-roll type electrode assembly according to claim 1, wherein the heating is performed at a temperature of 50° C. to 80° C. for 5 seconds to 15 seconds.

4. The jelly-roll type electrode assembly according to claim 1 , wherein the core portion of the jelly-roll type electrode assembly has a length in a longitudinal direction of at least 2 turns and at most 3 turns.

5. The jelly-roll type electrode assembly according to claim 1 , wherein a core portion of the jelly-roll type electrode assembly does not include the positive electrode and the negative electrode.

6. The jelly-roll type electrode assembly according to claim 1 , wherein one surface and the other surface of the flexible film are not in direct contact with the negative electrode or the positive electrode.

7. The jelly-roll type electrode assembly of claim 1 , wherein the width of the flexible film is 95% to 105% of the width of the jelly-roll type electrode assembly (100%).

8. The jelly-roll type electrode assembly of claim 1 , wherein the thickness of the flexible film is 5% to 20% of the thickness of the negative electrode (100%).

9. The jelly-roll type electrode assembly of claim 1 , wherein the flexible film has a thickness of 10 μm to 50 μm.

10. 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 jelly-roll type electrode assembly according to claim 1 , wherein the positive electrode current collector and the positive electrode active material layer have longitudinal ends at the same position.

11. A method for manufacturing a jelly roll-type electrode assembly in which a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound, (a) winding up the first separation membrane and the second separation membrane; (b) inserting a flexible film between the first separator and the second separator; (c) adding the negative electrode; (d) adding the positive electrode; (e) heating the jelly roll type electrode assembly by a heating means inserted into the hollow core of the jelly roll type electrode assembly; Including, a length in a longitudinal direction of the flexible film is 100% to 150% based on 100% of a circumference of an inner circumferential surface of the jelly-roll type electrode assembly; The tensile strength of the heated flexible film is 18 kgf / mm ２ (176.4N / mm ２ ) or more 25kgf / mm ２ (245N / mm ２ ) or less.

12. The method for manufacturing a jelly roll type electrode assembly according to claim 11, wherein the heating means is a reform pin.

13. The method of claim 12, wherein the diameter of the reform pin is 70% to 90% of the diameter of the hollow core portion (100%).

14. The method for manufacturing a jelly-roll type electrode assembly according to claim 11, wherein the heating is performed at a temperature of 50° C. to 80° C. for 5 seconds to 15 seconds.

15. A jelly-roll type electrode assembly manufactured by the manufacturing method of claim 11.

16. The jelly roll type electrode assembly according to any one of claims 1 to 10 and claim 15; a battery case for accommodating the jelly-roll type electrode assembly.

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

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