Jelly roll-type electrode assembly, manufacturing method therefor, and secondary battery comprising same

Abstract

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

Description

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

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

[0002]

[0003] In the case of cylindrical batteries, a long electrode with a fixed width is rolled into a jelly-roll-shaped electrode assembly to manufacture it. The cylindrical battery manufactured by inserting this jelly-roll-shaped electrode assembly into a battery case experiences repeated contraction / expansion of the electrode during charging and discharging. In particular, when a tab is located in the core of the jelly-roll-shaped electrode assembly or when a silicon-based active material is added to the negative electrode to increase the degree of contraction / expansion of the electrode assembly, the pressure acting on the core of the electrode assembly increases significantly.

[0004] Meanwhile, the core portion of the cylindrical battery is a space where a core used for winding a jelly-roll type electrode assembly is located, and there is an empty space, i.e. a hollow core portion, used in the cylindrical battery assembly process, such as the insertion process of the jelly-roll type electrode assembly into the battery case and the welding process.

[0005] Recently, with the increase in low-resistance / high-capacity designs, jelly-roll type electrode assemblies are increasingly including multiple tabs or adding silicon-based active materials. Accordingly, the possibility of deformation of the electrode assembly located in the core portion due to shrinkage / expansion of the electrode assembly increases, and in particular, core deformation, that is, a phenomenon in which the hollow core portion fails to maintain its circular shape and collapses, causes deterioration of the battery life, and when the separator located between the negative electrode and the positive electrode is damaged, there is a problem in which the negative electrode and the positive electrode come into direct contact, causing internal short-circuiting, resulting in heat generation and ignition.

[0006] In order to solve the problems of battery life deterioration, separator damage, and internal short-circuiting due to deformation of the electrode assembly, it is necessary to develop a technology that can support the core cavity in the relevant area to maintain its circular shape and suppress the occurrence of internal short-circuiting.

[0007]

[0008] The present invention provides a jelly-roll type electrode assembly having a modified design, a method for manufacturing a jelly-roll type electrode assembly, and a secondary battery including the same.

[0009] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0010]

[0011] 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 an anode are sequentially laminated and wound, wherein a core part of the jelly-roll type electrode assembly includes a flexible film disposed between the first separator and the second separator, and a longitudinal length of the flexible film is 100% or more and 150% or less based on 100% of an inner circumference of the jelly-roll type electrode assembly, and the flexible film is heated by a heating means inserted into a hollow part of the core part of the jelly-roll type electrode assembly, and a tensile strength of the heated flexible film is 18 kgf / mm. 2 More than 25 kgf / mm 2 A jelly-roll type electrode assembly is provided as follows.

[0012] 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 laminated and wound, comprising the steps of (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 by a heating means inserted into a hollow core portion of the jelly-roll type electrode assembly, wherein the longitudinal length of the flexible film is 100% or more and 150% or less based on 100% of the inner circumference of the jelly-roll type electrode assembly, and the tensile strength of the heated flexible film is 18 kgf / mm. 2 More than 25 kgf / 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.

[0013] 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.

[0014]

[0015] According to one embodiment of the present invention, a jelly-roll type electrode assembly includes a flexible film having a certain level of rigidity after heating is performed by a heating means inserted into a hollow core portion, thereby supporting the hollow core portion to maintain a circular shape from deformation of the electrode assembly due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode, thereby improving battery stability and life characteristics.

[0016] A method for manufacturing a jelly-roll type electrode assembly according to one embodiment of the present invention can manufacture a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity after heating in a simpler manner, and the rigidity of the flexible film before heating is suitable for a continuous process using existing roll-to-roll process equipment, thereby ensuring productivity and economy.

[0017] In addition, the secondary battery according to the present invention can improve battery stability and life characteristics by supporting the core cavity to maintain a circular shape even when the electrode assembly is deformed due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode.

[0018] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and the attached drawings.

[0019]

[0020] FIG. 1 illustrates a jelly-roll type electrode assembly including a flexible film according to one embodiment of the present invention.

[0021] FIG. 2 is a schematic diagram illustrating a method for manufacturing a jelly-roll type electrode assembly including a flexible film according to one embodiment of the present invention.

[0022] FIGS. 3 and 4 are CT images showing the results of long-term cycle evaluations of jelly-roll type electrode assemblies according to Examples 1 and 2.

[0023] Figures 5 to 7 are CT images showing the results of long-term cycle evaluations of jelly-roll type electrode assemblies according to Comparative Examples 1 to 3.

[0024]

[0025] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0026] Throughout this specification, when it is said that an element is "on" another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0027] Throughout this specification, the term 'soft film' means a film having a certain level of rigidity required for easy winding of a jelly-roll type electrode assembly, i.e., a rigidity below a specific value, 16 kgf / mm. 2 It refers to a film having the following tensile strength.

[0028]

[0029] 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 an anode are sequentially laminated and wound, wherein a core part of the jelly-roll type electrode assembly includes a flexible film disposed between the first separator and the second separator, and a longitudinal length of the flexible film is 100% or more and 150% or less based on 100% of an inner circumference of the jelly-roll type electrode assembly, and the flexible film is heated by a heating means inserted into a hollow part of the core part of the jelly-roll type electrode assembly, and a tensile strength of the heated flexible film is 18 kgf / mm. 2 More than 25 kgf / mm2 A jelly-roll type electrode assembly is provided as follows.

[0030] According to one embodiment of the present invention, a jelly-roll type electrode assembly includes a flexible film having a certain level of rigidity after heating is performed by a heating means inserted into a hollow core portion, thereby supporting the hollow core portion to maintain a circular shape from deformation of the electrode assembly due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode, thereby improving battery stability and life characteristics.

[0031] According to one embodiment of the present invention, the core part of the jelly-roll type electrode assembly may include a flexible film disposed between the first separator and the second separator. Here, the 'core part' may refer to a region including a hollow portion located on the winding axis of the electrode assembly and a portion of a 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 corner of the electrode assembly to the ends of the first separator and the second separator. The core part may refer to a region within 3 turns from one longitudinal end of the negative electrode.

[0032] According to one 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. In other words, the core portion of the jelly-roll type electrode assembly may be a region formed of a first separator, a flexible film, and a second separator.

[0033] According to one embodiment of the present invention, one side and the other side of the flexible film may not be in direct contact with the cathode or the anode. 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.

[0034] In this case, even when the 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 receiving lithium ions or an inhibition of electrolyte impregnation can be minimized.

[0035] 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, and may include a first region having a laminated structure of the first separator and the second separator; and a second region having a laminated structure of the first separator, the flexible film, and the second separator.

[0036] FIG. 1 illustrates a jelly-roll type electrode assembly including a flexible film according to one embodiment of the present invention, and FIG. 2 illustrates a schematic diagram of a method for manufacturing a jelly-roll type electrode assembly including a flexible film according to one embodiment of the present invention.

[0037] Referring to FIGS. 1 and 2, the core portion of the jelly-roll type electrode assembly may include a first region having a laminated structure of a first separator and a second separator; and a second region having a laminated structure of a 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 a first region having a laminated structure of the first separator and the second separator; and a second region having a laminated structure of the first separator, a flexible film, and a 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 core portion (C) may mean a region having a longitudinal length of the sum of the longitudinal length L1 of the first region and the longitudinal length L2 of the second region, that is, L1+L2, and L3 may be 0.

[0038] In this case, the longitudinal ends of the flexible film and the negative electrode may be in contact with each other, and the step may be minimized by adjusting the thickness range of the flexible film as described below. That is, the formation of a step due to a difference in the thickness of the flexible film and the negative electrode and the occurrence of local problems such as lithium precipitation in the step-formed area can be minimized.

[0039] According to one embodiment of the present invention, the longitudinal length of the first region may be 1 turn or more and 1.7 turns or less. Specifically, the longitudinal length (L1) of the first region may be 1.1 turns or more, 1.2 turns or more, or 1.3 turns or more, and may be 1.6 turns or less, 1.5 turns or less, or 1.4 turns or less.

[0040] Here, 1 turn may mean the length required for 360° winding of the separator included in the electrode assembly from a reference point, and the length may be determined according to the outer diameter of the core used for winding the electrode assembly, the thickness 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, the 1 turn may mean the length required for 360° winding of the first separator from a longitudinal end of the first separator in the direction in which the jelly-roll-type electrode assembly is wound.

[0041] When the longitudinal length range of the first region described above is satisfied, the winding of the electrode assembly can be made easier 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 1 turn, the tension for continuous winding may not be sufficient when winding using a core.

[0042] According to one embodiment of the present invention, the core part of the jelly-roll type electrode assembly may further include a third region having a laminated structure of a first separator and a second separator. Specifically, the core part of the jelly-roll type electrode assembly may include a first region having a laminated structure of a first separator and a second separator; a second region having a laminated structure of a first separator, a flexible film, and a second separator; and a third region having a laminated 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 part (C) may mean a region having a longitudinal length of 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, that is, L1+L2+L3, and L3>0.

[0043] In this case, the longitudinal end portions of the flexible film and the negative electrode may not be in contact with each other, and as described below, by controlling the distance between the longitudinal end portions of the flexible film and the negative electrode, damage to the separator caused by the end portions of the electrode or the flexible film can be minimized even when the electrode assembly shrinks / expands.

[0044] According to one embodiment of the present invention, the longitudinal length of the flexible film may be 100% or more and 150% or less, based on 100% of the inner circumference of the jelly-roll type electrode assembly. Specifically, the longitudinal length of the flexible film may be 105% or more, 110% or more, 115% or more, or 120% or more, and may be 145% or less, 140% or less, 135% or less, or 130% or less, based on 100% of the inner circumference of the jelly-roll type electrode assembly.

[0045] Here, the 'inner circumference' may refer to the circumference of an imaginary circle whose radius is the largest value among the distances from the winding axis of the electrode assembly to the innermost layer in contact with the hollow of the electrode assembly, and may have a length determined according to the outer diameter of the winding core used for winding the electrode assembly. For example, the inner circumference may have a value of approximately 10 mm.

[0046] According to one embodiment of the present invention, the longitudinal length of the flexible film may be 0.9 turns or more and 1.4 turns or less. Specifically, the distance between one longitudinal end of the flexible film and one longitudinal end of the cathode 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 longitudinal length of the flexible film may be the same as the longitudinal length L2 of the second region.

[0047] When the longitudinal length of the flexible film satisfies the above-mentioned range, the core support effect by the heated flexible film can be better, and the reduction in battery capacity and energy density can be minimized, thereby preventing deterioration of electrochemical characteristics.

[0048] According to one embodiment of the present invention, the distance between one longitudinal end of the flexible film and one longitudinal end of the cathode may be 0.5 turns or less. Specifically, the distance between one longitudinal end of the flexible film and one longitudinal end of the cathode 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 cathode may be equal to the longitudinal length L3 of the third region.

[0049] In this case, one longitudinal end of the flexible film and the cathode may be in contact with each other, and the step caused by the thickness difference between the electrode and the flexible film can be minimized by adjusting the thickness of the flexible film and the cathode.

[0050] According to one embodiment of the present invention, the distance between one longitudinal end of the flexible film and one longitudinal end of the cathode 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 cathode may be 0.4 turns or more or 0.5 turns or more, and 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 cathode may be equal to the longitudinal length L3 of the third region.

[0051] In this case, the longitudinal end portions of the flexible film and the negative electrode may not be in contact with each other, and by controlling the distance between the longitudinal end portions of the flexible film and the negative electrode, damage to the separator caused by the end portions of the electrode or the flexible film can be minimized even when the electrode assembly shrinks / expands.

[0052] According to one embodiment of the present invention, the flexible film may further include a fixing member on at least one surface. Specifically, the fixing member is intended to minimize sliding of the flexible film, and may be formed using an adhesive or adhesive tape. When the fixing member is further included, damage to the separator caused by the ends of the electrode or the flexible film can be minimized even when the electrode assembly shrinks / expands or the flexible film slides.

[0053] According to one embodiment of the present invention, the flexible film may be heated by a heating means inserted into the hollow core portion of the jelly-roll type electrode assembly.

[0054] According to one embodiment of the present invention, the tensile strength of the flexible film before heating is 9 kgf / mm 2 More than 16 kgf / mm 2 It may be as follows. Specifically, the tensile strength of the above-mentioned flexible film before heating is 10 kgf / mm. 2 Above, 11 kgf / mm 2 or more than 12 kgf / mm 2 It can be more than 15 kgf / mm 2 Below, 14 kgf / mm 2 Less than or equal to 13 kgf / mm 2 It could be as follows:

[0055] According to one embodiment of the present invention, the flexible film may have an increase in tensile strength after heating. Specifically, the flexible film may have an increase in tensile strength according to modification of the flexible film after heating is performed on one or both sides, and the increase in tensile strength may vary depending on the degree of heating of the flexible film, i.e., the heating area, heating temperature, and heating time.

[0056] 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, and may be 190% or less, 180% or less, or 170% or less, based on 100% of the tensile strength before heating.

[0057] According to one embodiment of the present invention, the tensile strength of the heated flexible film is 18 kgf / mm 2 More than 25 kgf / mm 2 It may be as follows. Specifically, the tensile strength of the heated flexible film is 19 kgf / mm. 2 Above, 20 kgf / mm 2 or more than 21 kgf / mm 2It may be more than 24 kgf / mm 2 Below, 23 kgf / mm 2 Less than or equal to 22 kgf / mm 2 It could be as follows:

[0058] Here, the tensile strength of the flexible film may be measured by producing a sample of 20 mm X 100 mm in size and 10 ㎛ in thickness for the heated film sample and using a UTM (Universal Testing Machine) at room temperature and a speed of 2 cm / min.

[0059] When the rigidity of the above-mentioned flexible film before heating satisfies the above-mentioned range, the rigidity of the jelly-roll type electrode assembly including the above-mentioned flexible film may be more suitable for the roll-to-roll process, thereby improving the productivity and economic feasibility of the jelly-roll type electrode assembly.

[0060] When the tensile strength of the heated flexible film satisfies the above-mentioned range, the core support effect by the heated flexible film can be 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.

[0061] According to one embodiment of the present invention, the heating means may be a reform pin. Specifically, referring to (c) of FIG. 2, the heating means may be a reform pin (200) that forms the jelly-roll type electrode assembly (100) by pushing a separator (not shown) located in the hollow core portion (H) of the jelly-roll type electrode assembly (100) toward the inner peripheral surface of the core portion of the jelly-roll type electrode assembly (100) to form a cylindrical hollow portion.

[0062] A pair of cores may be used in the winding process of a jelly-roll type electrode assembly, and the electrode assembly is wound in a jelly-roll shape using the cores, and then the electrode assembly is separated from the cores. At this time, a separator is formed across the hollow portion of the core portion of the jelly-roll type electrode assembly in a shape corresponding to the gap between the pair of cores used for the winding. In order to remove the separator across the hollow portion and restore the central portion of the electrode assembly to a circular shape, the central portion must be cleaned up through a separate reforming process using a reforming pin after the winding process of the electrode assembly.

[0063] When the above heating means is a reformed pin, by removing the separator crossing the hollow core of the jelly-roll type electrode assembly after winding, the subsequent process can be facilitated, thereby improving the productivity of the electrode assembly. In addition, by controlling the degree of heating of the flexible film, i.e., the heating area, heating temperature, and heating time within a specific range, it is possible to secure a certain level of rigidity of the heated flexible film.

[0064] According to one embodiment of the present invention, the heating may be performed on one side of the flexible film. Specifically, the heating may be performed on the entire side of the flexible film.

[0065] According to one embodiment of the present invention, the heating may be performed at a temperature of 50°C or more and 80°C or less, for a time of 5 seconds or more and 15 seconds or less.

[0066] By controlling the degree of heating of the above flexible film, i.e., the heating area, heating temperature, and heating time within a specific range, it is possible to manufacture a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity.

[0067] According to one embodiment of the present invention, the heating may be performed at a temperature of 55°C or higher, 60°C or higher, or 65°C or higher, or may be performed at a temperature of 75°C or lower, 70°C or lower, or 65°C or lower. For example, the heating may be performed at a temperature of 60°C.

[0068] According to one embodiment of the present invention, the heating may be performed for a time of 5 seconds or more and 15 seconds or less. Specifically, the heating may be performed for a time of 6 seconds or more, 7 seconds or more, 8 seconds or more, or 9 seconds or more, or 14 seconds or less, 13 seconds or less, 12 seconds or less, or 11 seconds or less. For example, the heating may be performed for a time of 10 seconds.

[0069] When the above-described heating time and temperature conditions are satisfied, the manufacture of a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity can be easier, and the core support effect by the heated flexible film can be better.

[0070] On the other hand, if the heating is excessive, shrinkage of the separator may occur, and if the heating is insufficient, the increase in rigidity of the heated flexible film may not be sufficient, resulting in inferior core support effect.

[0071] According to one embodiment of the present invention, the core portion of the jelly-roll type electrode assembly may have a longitudinal length of 2 turns or more and 3 turns or less. Specifically, the core portion 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, and 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.

[0072] Referring to FIG. 2, the longitudinal length of the core portion may be equal to 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.

[0073] Here, 1 turn may mean the length required for 360° winding of the separator included in the electrode assembly from a reference point, and the length may be determined according to the outer diameter of the core used for winding the electrode assembly, the thickness 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, the 1 turn may mean the length required for 360° winding of the first separator from a longitudinal end of the first separator in the direction in which the jelly-roll-type electrode assembly is wound.

[0074] When the longitudinal length of the core portion satisfies the above-described range, sufficient space can be secured for arranging the flexible film, and the core portion support effect by the heated flexible film can be better.

[0075] According to one embodiment of the present invention, the width direction length of the flexible film may be 95% or more and 105% or less, based on 100% of the width direction length of the jelly-roll type electrode assembly. Specifically, the width direction length of the flexible film may be 96% or more, 97% or more, 98% or more, 99% or more, or 100% or more, and may be 104% or less, 103% or less, 102% or less, 101% or less, or 100% or less, based on 100% of the width direction length of the jelly-roll type electrode assembly.

[0076] When the widthwise length of the above-mentioned flexible film satisfies the above-mentioned range, the length of the above-mentioned flexible film can correspond to the widthwise length of the above-mentioned jelly-roll type electrode assembly, can be advantageous in supporting the core portion of the above-mentioned jelly-roll type electrode assembly, and can have an excellent effect in preventing deformation of the core portion.

[0077]

[0078] *If the widthwise length of the above-mentioned flexible film is excessively short, the effect of preventing deformation of the core portion may be inferior. Conversely, if the above-mentioned flexible film is excessively exposed in the widthwise direction of the jelly-roll type electrode assembly, the occurrence rate of defects increases during the insertion process into the battery case, and local problems such as lithium precipitation due to step formation may occur.

[0079] 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).

[0080] When the material of the flexible film is of the aforementioned type, the rigidity of the heated flexible film may be sufficient to support the core part of the jelly-roll type electrode assembly, and the rigidity of the flexible film before heating may be more suitable for the roll-to-roll process, thereby improving the productivity and economic feasibility of the jelly-roll type electrode assembly.

[0081] According to one embodiment of the present invention, the thickness of the flexible film may be 5% or more and 20% or less based on 100% of the thickness of the cathode. Specifically, the thickness of the flexible film may be 6% or more, 7% or more, 8% or more, 9% or more, or 10% or more, and 19% or less, 18% or less, 17% or less, 16% or less, or 15% or less based on 100% of the thickness of the cathode.

[0082] When the thickness of the flexible film satisfies the aforementioned range, the step may 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 a difference in the thickness of the flexible film and the negative electrode and lithium precipitation in the step-formed area can be minimized.

[0083] According to one embodiment of the present invention, the thickness of the flexible film may be 10 ㎛ or more and 50 ㎛ or less. Specifically, the thickness of the flexible film may be 15 ㎛ or more, 20 ㎛ or more, or 25 ㎛ or more, and may be 45 ㎛ or less, 40 ㎛ or less, or 35 ㎛ or less.

[0084] When the thickness of the flexible film satisfies the above-mentioned range, the rigidity of the heated flexible film may be sufficient to support the core portion of the jelly-roll type electrode assembly, and the rigidity of the flexible film before heating may be more suitable for the roll-to-roll process, thereby improving the productivity and economic feasibility of the jelly-roll type electrode assembly.

[0085] According to one embodiment of the present invention, 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, wherein 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 be in the form of a free-edge.

[0086] Through this, the area of ​​the unnecessary positive electrode current collector non-conducting portion can be reduced to secure economic feasibility, and since the slitting process can be performed after forming the active material layer on the electrode, the roll-to-roll process including the slitting process and the winding process can be performed more efficiently.

[0087] Here, 'same position' means that the longitudinal ends are the same, and may include cases where the ends are formed at substantially the same positions due to process errors that may occur during the slitting process, etc.

[0088] According to one embodiment of the present invention, the positive electrode current collector may include a positive electrode holding portion to which a positive electrode active material is applied and a positive electrode non-coated portion to which the positive electrode active material is not applied, and may include a tab on the positive electrode non-coated portion. Specifically, the positive electrode current collector may include a positive electrode non-coated portion, and may include a positive electrode tab formed on the positive electrode non-coated portion.

[0089] 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. Specifically, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, or the like.

[0090] In addition, the positive electrode current collector may typically have a thickness of 5 μm or more and 30 μm or less, and may form fine irregularities on the surface of the positive electrode current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0091] 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 such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound having the chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4(0≤x≤0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M y Ni-site type lithium nickel oxide represented by O2 (wherein, M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and satisfies 0.01≤y≤0.3); chemical formula LiMn 2-z M z Lithium manganese composite oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 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); LiMn2O4, etc., in which a part of Li in the chemical formula is replaced with an alkaline earth metal ion, but is not limited thereto. The positive electrode may be Li-metal.

[0092] 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 provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and has electronic conductivity may be used without particular limitation. 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, summer black, carbon fiber, etc.; metal powder or metal fiber such as copper, nickel, aluminum, silver, etc.; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxide such as titanium oxide; or conductive polymers such as polyphenylene derivatives, etc., and one of these may be used alone or a mixture of two or more may be used.

[0093] In addition, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesiveness between the positive electrode active material and the positive 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, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0094] 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 provided 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 the negative electrode holding portion of the negative electrode current collector, and a surface on which the negative electrode active material layer is not provided may be expressed as a negative electrode non-conductive portion.

[0095] According to one embodiment of the present invention, the negative electrode current collector may include a negative electrode holding portion where a negative electrode active material layer is formed and a negative electrode non-conductive portion where a negative electrode active material layer is not formed, and may include a tab on the negative electrode non-conductive portion. Specifically, the negative electrode current collector may include a negative electrode non-conductive portion, and may include a negative electrode tab formed on the negative electrode non-conductive portion. Accordingly, the manufactured electrode assembly may include one or more negative electrode tabs.

[0096] According to one 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. In addition, 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; the negative electrode conductive material; and the negative electrode binder may be any material used in the art without limitation.

[0097] According to one embodiment of the present invention, the negative electrode current collector may be any conductive material that does not cause a chemical change in the battery, and is not particularly limited thereto. 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 adsorbs carbon well, such as copper or nickel, may be used as the negative electrode current collector. The thickness of the negative electrode current collector may be 5 μm or more and 30 μm or less, but the thickness of the negative electrode current collector is not limited thereto.

[0098] 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), fluoroelastomer, polyacrylic acid, and a material in which hydrogens thereof are substituted with Li, Na, Ca, or the like, and may also include various copolymers thereof.

[0099] According to one embodiment of the present invention, the negative electrode conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0100] According to one embodiment of the present invention, the jelly-roll type electrode assembly may include a plurality of separators. For example, the jelly-roll type electrode assembly may have a structure in which separator / negative electrode / separator / positive electrode are sequentially laminated. The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in secondary batteries may be used without particular limitation, and in particular, a separator having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. 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 laminated structure of two or more layers thereof may be used. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, the above-described separator may be a separator that uses the aforementioned separator material as a substrate layer and coats a slurry containing a ceramic component or a polymer material on the substrate layer to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure. The thickness of the above-described separator may be 10 ㎛ or more and 20 ㎛ or less, but is not limited thereto.

[0101]

[0102] 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 laminated and wound, comprising the steps of (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 by a heating means inserted into a hollow core portion of the jelly-roll type electrode assembly, wherein the longitudinal length of the flexible film is 100% or more and 150% or less based on 100% of the inner circumference of the jelly-roll type electrode assembly, and the tensile strength of the heated flexible film is 18 kgf / mm. 2 More than 25 kgf / 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.

[0103] A method for manufacturing a jelly-roll type electrode assembly according to one embodiment of the present invention can manufacture a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity after heating in a simpler manner, and the rigidity of the flexible film before heating is suitable for a continuous process using existing roll-to-roll process equipment, thereby ensuring productivity and economy.

[0104] In addition, the jelly-roll type electrode assembly manufactured by the above manufacturing method includes a flexible film having a certain level of rigidity after heating in the core portion, thereby supporting the hollow portion of the core portion to maintain a circular shape from deformation of the electrode assembly due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode, thereby improving battery stability and life characteristics.

[0105] According to one embodiment of the present invention, the longitudinal length of the flexible film may be 100% or more and 150% or less, based on 100% of the inner circumference of the jelly-roll type electrode assembly. Specifically, the longitudinal length of the flexible film may be 105% or more, 110% or more, 115% or more, or 120% or more, and may be 145% or less, 140% or less, 135% or less, or 130% or less, based on 100% of the inner circumference of the jelly-roll type electrode assembly.

[0106] When the longitudinal length of the flexible film satisfies the above-mentioned range, the core support effect by the heated flexible film can be better, and the reduction in battery capacity and energy density can be minimized, thereby preventing deterioration of electrochemical characteristics.

[0107] According to one embodiment of the present invention, the tensile strength of the heated flexible film is 18 kgf / mm 2 More than 25 kgf / mm 2 It may be as follows. Specifically, the tensile strength of the heated flexible film is 19 kgf / mm. 2 Above, 20 kgf / mm 2 or more than 21 kgf / mm 2 It may be more than 24 kgf / mm 2 Below, 23 kgf / mm 2 Less than or equal to 22 kgf / mm 2 It could be as follows:

[0108] When the tensile strength of the heated flexible film satisfies the above-mentioned range, the core support effect by the heated flexible film can be 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.

[0109] Here, the meaning of the core portion and the inner circumference, the physical properties of the flexible film, i.e., the tensile strength and tensile strength increase rate of the flexible film before heating, and the tensile strength measuring method of the flexible film may be the same as described above for the jelly-roll type electrode assembly. In addition, the meaning 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 longitudinal length L1+L2+L3 of the core portion may be the same as described above for the jelly-roll type electrode assembly.

[0110] According to one embodiment of the present invention, the method for manufacturing the jelly-roll type electrode assembly may be performed in a roll-to-roll manner. Specifically, steps (a) to (d) may be performed in a roll-to-roll processing manner in which multiple bendable metal foils or the like are processed while moving between rollers.

[0111] Here, the roll-to-roll method may mean a method of unwinding a roll that winds a flexible and thin metal sheet-shaped electrode current collector to supply the electrode current collector, applying an electrode slurry containing an electrode active material to at least one surface of the electrode current collector and drying it to form an electrode mixture layer, and then rewinding the processed electrode current collector on another roll to recover it.

[0112] In addition, the above-mentioned 'input' may mean a part of a series of input and winding processes, i.e., a winding process, performed in a roll-to-roll electrode assembly manufacturing step. Specifically, it may mean a process of additionally inserting a film or electrode wound between a plurality of separators, a portion of which is wound along a longitudinal length from one end thereof on a core, or on one surface of a plurality of separators, a portion of which is wound along a core, and may mean a process of manufacturing an electrode assembly by continuously winding the inserted film or electrode together with the plurality of separators, a portion of which is wound along the core, and may include a slitting process of cutting a portion of the longitudinal length, if necessary.

[0113] A method for manufacturing a jelly-roll type electrode assembly according to one embodiment of the present invention may be capable of continuously producing a jelly-roll type electrode assembly including the heated flexible film using existing roll-to-roll process equipment. In other words, the method for manufacturing a jelly-roll type electrode assembly may be such that step (b) is performed after step (a) and before step (c), and thus the entire process may be performed by a roll-to-roll process used in the art.

[0114] That is, the method for manufacturing a jelly-roll type electrode assembly according to one embodiment of the present invention can secure productivity and economy by enabling the continuous production of a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity after heating using existing roll-to-roll process equipment.

[0115] According to one embodiment of the present invention, the method for manufacturing the jelly-roll type electrode assembly may include a step of heating by a heating means inserted into the hollow core portion of the jelly-roll type electrode assembly. Specifically, the heating means may be a reform pin, and the reform pin may be the same as described above with respect to the jelly-roll type electrode assembly.

[0116] According to one embodiment of the present invention, the reform pin may be inserted into the hollow portion of the electrode assembly, and then repeatedly advances and retreats to push and remove the separator across the hollow portion of the core portion to the innermost layer in contact with the hollow portion of the electrode assembly.

[0117] 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 100% diameter of the hollow core portion. Specifically, the diameter of the reform pin may be 75% or more, 80% or more, or 85% or more, and may be 85% or less, 80% or less, or 75% or less of the 100% diameter of the hollow core portion.

[0118] When the diameter of the reform pin satisfies the above-described range, the degree of heating of the flexible film, i.e., the heating area, heating temperature, and heating time, can be controlled within a specific range, thereby ensuring a certain level of rigidity of the heated flexible film, and preventing the separator from protruding when the reform pin is removed.

[0119] According to one embodiment of the present invention, the length of the reform pin may be 100% or more based on 100% of the width direction length of the jelly-roll type electrode assembly.

[0120] When the length of the reform pin satisfies the above-described range, the length of the reform pin may correspond to the widthwise length of the jelly-roll type electrode assembly, and the process of removing the separator across the core portion hollow portion of the electrode assembly and the heating may be performed more uniformly over the entire widthwise length of the electrode assembly.

[0121] According to one embodiment of the present invention, the heating may be performed at a temperature of 50°C or more and 80°C or less, for a time of 5 seconds or more and 15 seconds or less.

[0122] According to one embodiment of the present invention, the heating may be performed at a temperature of 55°C or higher, 60°C or higher, or 65°C or higher, or may be performed at a temperature of 75°C or lower, 70°C or lower, or 65°C or lower. For example, the heating may be performed at a temperature of 60°C.

[0123] According to one embodiment of the present invention, the heating may be performed for a time of 5 seconds or more and 15 seconds or less. Specifically, the heating may be performed for a time of 6 seconds or more, 7 seconds or more, 8 seconds or more, or 9 seconds or more, or 14 seconds or less, 13 seconds or less, 12 seconds or less, or 11 seconds or less. For example, the heating may be performed for a time of 10 seconds.

[0124] When the above-described heating time and temperature conditions are satisfied, the manufacture of a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity can be easier, and the core support effect by the heated flexible film can be better.

[0125] On the other hand, if the heating is excessive, shrinkage of the separator may occur, and if the heating is insufficient, the increase in rigidity of the heated flexible film may not be sufficient, resulting in inferior core support effect.

[0126] FIG. 2 is a schematic diagram illustrating a method for manufacturing a jelly-roll type electrode assembly including a flexible film according to one embodiment of the present invention.

[0127] Referring to Fig. 2, step (a) may be winding the first separator and the second separator. After winding the first separator and the second separator to a predetermined length using a core, step (b) may be performed.

[0128] That is, a flexible film may be inserted between the first separator and the second separator, which are wound to a predetermined length. Through this, the core part of the jelly-roll type electrode assembly may 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 widthwise length, material, and thickness of the inserted flexible film may be the same as those described above with respect to the jelly-roll type electrode assembly.

[0129] Through the above step (b), the flexible film may be provided with a predetermined length, and the core part of the jelly-roll type electrode assembly including the flexible film may also be provided with a predetermined length.

[0130] Next, steps (c) and (d) may be performed sequentially.

[0131] According to one embodiment of the present invention, the step (c) may be to insert the cathode, and specifically, to insert the cathode between the first separator and the second separator.

[0132] The longitudinal end portions of the above flexible film and the above negative electrode may not be in contact with each other, and by controlling the distance between the longitudinal end portions of the above flexible film and the above negative electrode, damage to the separator caused by the end portions of the electrode or the flexible film may be minimized even when the electrode assembly shrinks / expands.

[0133] On the other hand, when the longitudinal ends of the flexible film and the negative electrode are in contact with each other, the thickness range of the flexible film can be adjusted to minimize the step, thereby minimizing the occurrence of local problems such as lithium precipitation in the step formation area.

[0134] Next, the step (e) may be performed after the steps (a) to (d). Specifically, after the jelly-roll-type electrode assembly is wound, heating may be performed 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 crossing the hollow core portion of the electrode assembly and the heating may be performed simultaneously.

[0135] A method for manufacturing a jelly-roll type electrode assembly according to one embodiment of the present invention can manufacture a jelly-roll type electrode assembly including a flexible film having a certain level of rigidity after heating in a simpler manner, and the rigidity of the flexible film before heating is suitable for a continuous process using existing roll-to-roll process equipment, thereby ensuring productivity and economy.

[0136] One embodiment of the present invention provides a jelly-roll type electrode assembly manufactured by the jelly-roll type electrode assembly manufacturing method described above.

[0137] A jelly-roll type electrode assembly according to one embodiment of the present invention includes a flexible film having a certain level of rigidity after heating in the core portion, thereby supporting the hollow portion of the core portion to maintain a circular shape from deformation of the electrode assembly due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode, thereby improving battery stability and life characteristics.

[0138] One embodiment of the present invention provides a secondary battery comprising the jelly-roll-shaped electrode assembly and a battery case for accommodating the electrode assembly. Specifically, the secondary battery may comprise the electrode assembly according to the above-described embodiment and a battery case for accommodating the electrode assembly.

[0139] The secondary battery according to the present invention can improve battery stability and life characteristics by supporting the hollow core portion to maintain a circular shape even when the electrode assembly is deformed due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode.

[0140] According to one embodiment of the present invention, the battery case may be cylindrical. Specifically, the battery case may be cylindrical, square, or pouch-shaped, depending on the intended use, but is not limited thereto.

[0141] According to one embodiment of the present invention, the interior of the battery case may include 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 polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used in the manufacture of a lithium secondary battery. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0142] According to one embodiment of the present invention, the non-aqueous organic solvent may be, for example, an aprotic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyropionate, ethyl propionate, etc. Organic solvents may be used.

[0143] 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.

[0144] According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives, such as, for example, a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine 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 battery capacity decrease, and improving the discharge capacity of the battery.

[0145] One 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 battery pack include the secondary battery with improved high capacity, high battery stability, and lifespan characteristics, and thus 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.

[0146]

[0147] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0148]

[0149] Example

[0150] Example 1

[0151] Electrode assembly manufacturing

[0152] Li(Ni) as a cathode material 0.93 Co 0.01 Mn 0.03 Al 0.03 )O2, CNT as a positive electrode conductive material, and polyvinylidene fluoride (PVdF) as a binder were added to N-methyl-2-pyrrolidone (NMP) at a weight ratio of 98.2:0.8:1.0 to prepare a positive electrode active material slurry. The positive electrode active material slurry was coated on an aluminum current collector having a thickness of 15 μm and a width of 64 mm, and then dried and rolled to form a positive electrode active material layer, thereby preparing a positive electrode having a thickness of 175 μm.

[0153] Next, natural graphite (C, average particle size 10 μm, POSCO Chemical Co.) and SiO (average particle size (D)) were used as negative active materials. 50 ): 5 ㎛) were prepared in a weight ratio of 95:5 (SiO 5 wt%), and a mixture of the negative active material, carbon black as a conductive material, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) as a first binder was mixed in a weight ratio of 98:1:1 to prepare a negative active material composition. Then, 7.8 g of distilled water was added to 5 g of the negative active material composition and stirred to prepare a negative active material slurry. The negative active material slurry was applied to a copper (Cu) metal thin film as a negative electrode current collector having a thickness of 10 ㎛ and a widthwise length of 65 mm, and dried (drying temperature 120°C, 1 minute), thereby forming a negative electrode having an average thickness of 185 ㎛. At this time, the temperature of the circulating air was 60°C.

[0154] Afterwards, a flexible film made of polypropylene (PP) with a width of 65 mm, a length of 15 mm, and a thickness of 50 ㎛, and two separators made of polyethylene (PE) with a thickness of 13 ㎛ as the first and second separators were prepared, respectively. At this time, after producing a sample with a size of 20 mm X 100 mm and a thickness of 10 ㎛ for the flexible film, the tensile strength measured under room temperature and a speed of 2 cm / min using a UTM (Universal Testing Machine) was 11 kgf / mm 2 It was.

[0155] Afterwards, the first separator and the second separator were sequentially arranged and wound using a core having a diameter of 3.4 mm, and then the flexible film was inserted between the first separator and the second separator and additionally wound. After the flexible film was completely wound, the negative electrode and the positive electrode were sequentially inserted and wound at a distance of 6 ㎛ from the flexible film, and at the end where the winding was completed, a seal tape made of PET material was attached and finished to wrap the upper and lower outer peripheral surfaces of the jelly-roll, thereby manufacturing a jelly-roll type electrode assembly. At this time, the inner peripheral circumference of the jelly-roll type electrode assembly was about 12 mm, and the length from the longitudinal end of the negative electrode to the longitudinal end of the first separator was about 15 mm.

[0156] Afterwards, a reforming pin with a diameter of 2.5 mm equipped with a heater was inserted into the hollow of the electrode assembly, and the separator crossing the hollow of the core was pushed out and removed to the innermost layer in contact with the hollow of the electrode assembly by repeating forward and backward movements. At this time, the heater equipped in the reforming pin was adjusted to 60 ℃, and the reforming was performed for 10 seconds. At this time, a sample with a size of 20 mm X 100 mm and a thickness of 10 ㎛ was produced for the heated flexible film, and the tensile strength measured under room temperature and 2 cm / min speed conditions with a UTM (Universal Testing Machine) was 18 kgf / mm. 2 It was.

[0157] Manufacturing of secondary batteries

[0158]

[0159] *After inserting the above jelly-roll type electrode assembly into a cylindrical battery case, an electrolyte solution was injected in which ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) was mixed in a volume ratio of 20:50:30 and LiPF6 was dissolved to 1.3 M, and the cylindrical battery can was sealed with a cap assembly to manufacture a secondary battery.

[0160] Example 2

[0161] A jelly-roll type electrode assembly and secondary battery were manufactured in the same manner as Example 1, except that a film made of polyethylene (PE) was used as the above-mentioned flexible film.

[0162] At this time, after producing a sample of 20 mm X 100 mm in size and 10 ㎛ in thickness for the above soft film, the tensile strength measured under room temperature and 2 cm / min speed conditions using a UTM (Universal Testing Machine) was 15 kgf / mm. 2 And, the tensile strength of the heated flexible film is 25 kgf / mm. 2 It was.

[0163] Comparative Example 1

[0164] 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 introduced.

[0165] Comparative Example 2

[0166] 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. At this time, a sample with a size of 20 mm X 100 mm and a thickness of 10 ㎛ was manufactured for the PI film, and the tensile strength measured under room temperature and a speed of 2 cm / min using a UTM (Universal Testing Machine) was 5 kgf / mm. 2 And, the tensile strength of the heated flexible film is 10 kgf / mm. 2 It was.

[0167] Comparative Example 3

[0168] A jelly-roll type electrode assembly and secondary battery were manufactured in the same manner as Example 1, except that a film having a longitudinal length of 30 mm was used as the above-mentioned flexible film.

[0169] Experimental example

[0170] Experimental Example 1: Cycle Stability Evaluation

[0171] For the secondary batteries manufactured in the above examples and comparative examples, a cycle test was performed at 4.2-2.85 V 0.5 C / 0.5 C under 25°C conditions using an electrochemical charger / discharger, and after 50 cycles, the cycle stability was evaluated by checking for core deformation by performing computed tomography (CT) on the core portion, and the images are shown in FIGS. 3 to 7, respectively.

[0172] Experimental Example 2: Life Evaluation

[0173] In the above examples and comparative examples, the lifespan of the secondary batteries was evaluated using an electrochemical charger / discharger, and the capacity retention rate was evaluated. 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 by charging / discharging at 0.2 C / 0.2 C (4.2-2.85 V) every 100 cycles during the test, and the results are shown in Table 1.

[0174] Life retention rate (%) = {(discharge capacity at Nth cycle) / (discharge capacity at 1st cycle)} Х 100

[0175] Experimental Example 3: Resistance Increase Rate Measurement Evaluation

[0176] In the above experimental example 2, the capacity retention rate was measured by performing 0.2 C / 0.2 C charge / discharge (4.2-2.85 V) every 100 cycles during the test, and then the resistance was measured by discharging with 0.5 C pulse at SOC 50 to compare and analyze the resistance increase rate, and the results are as shown in Table 1 below.

[0177] Capa. (mAh)@1 cycle 0.2 C / 0.2 C, 4.2-2.85 V @25 ℃ Capa. Retention@600 cycle 0.33 C / 0.33 C, 4.2-3.11 V @25 ℃ Resistance Increase %@600 cycle(SOC 50) Example 1534692.712.5 Example 2532191.313.2 Comparative Example 1527984.536.1 Comparative Example 2532389.113.1 Comparative Example 3512290.411.2

[0178] Referring to Table 1 and FIGS. 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 that the rigidity of the flexible film increases through heating using a reform pin after assembling the jelly-roll type electrode assembly, thereby improving core deformation. In addition, it was confirmed that the secondary batteries according to Examples 1 and 2 can express the designed capacity and improve the lifespan and resistance characteristics at the same time. On the other hand, in the case of Comparative Examples 1 to 3, when the flexible film is not included or the tensile strength is 18 kgf / mm even after heating, 2 Hereinafter, it was confirmed that when using a film with inferior rigidity, core deformation occurs, increasing internal battery resistance and deteriorating life characteristics. Furthermore, it was confirmed that when the longitudinal length of the flexible film increases excessively, the longitudinal length of the electrode decreases, reducing the design capacity and actual achievable discharge capacity.

[0179] Through this, the jelly-roll type electrode assembly according to one embodiment of the present invention and the secondary battery including the same include a flexible film having a certain level of rigidity after heating is performed by a heating means inserted into the hollow core portion, thereby supporting the hollow core portion to maintain a circular shape from deformation of the electrode assembly due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short between the positive electrode and negative electrode, so that the battery stability and life characteristics can be improved.

[0180]

[0181] The detailed description above is intended to illustrate and explain the present invention. Furthermore, the foregoing merely illustrates and describes preferred embodiments of the present invention. As described above, the present invention can be utilized in various other combinations, modifications, and environments, and variations or modifications can be made within the scope of the inventive concepts disclosed herein, the scope equivalent to the above-described disclosure, and / or the scope of technology or knowledge in the art. Therefore, the detailed description of the invention above is not intended to limit the present invention to the disclosed embodiments. Furthermore, the appended claims should be construed to include other embodiments.

[0182]

[0183] According to one embodiment of the present invention, a jelly-roll type electrode assembly and a secondary battery including the same include a flexible film having a certain level of rigidity after heating is performed by a heating means inserted into a hollow core portion, thereby supporting the hollow core portion to maintain a circular shape from deformation of the electrode assembly due to shrinkage / expansion of the electrode during battery charging / discharging, thereby preventing damage to the positive electrode and separator and preventing internal short circuit between the positive electrode and negative electrode, thereby improving battery stability and life characteristics.

[0184]

[0185] [Explanation of symbols]

[0186] 10: First membrane

[0187] 20: Cathode

[0188] 30: Second membrane

[0189] 40: Bipolar

[0190] 50: Soft film

[0191] 100: Jelly-roll type electrode assembly

[0192] 200: Reform Pin

[0193] L1: longitudinal length of the first region

[0194] L2: longitudinal length of the second region

[0195] L3: Longitudinal length of the third region

[0196] C: Core

[0197] H: Core hollow

Claims

1. In a jelly-roll type electrode assembly in which a first separator; a cathode; a second separator and an anode are sequentially laminated and wound, The core portion of the jelly-roll type electrode assembly includes a flexible film disposed between the first separator and the second separator, The longitudinal length of the above flexible film is 100% or more and 150% or less based on 100% of the inner circumference of the jelly-roll type electrode assembly, The above soft 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 More than 25 kgf / mm 2 A jelly-roll type electrode assembly as follows.

2. In paragraph 1, A jelly-roll type electrode assembly wherein the above heating means is a reformed pin.

3. In paragraph 1, A jelly-roll type electrode assembly wherein the above heating is performed at a temperature of 50°C or higher and 80°C or lower for a time of 5 seconds or higher and 15 seconds or lower.

4. In paragraph 1, A jelly-roll type electrode assembly, wherein the core portion of the jelly-roll type electrode assembly has a longitudinal length of 2 turns or more and 3 turns or less.

5. In paragraph 1, A jelly-roll type electrode assembly, wherein the core part of the jelly-roll type electrode assembly does not include the positive electrode and the negative electrode.

6. In paragraph 1, A jelly-roll type electrode assembly wherein one side and the other side of the above-mentioned flexible film do not directly contact the above-mentioned negative electrode or the above-mentioned positive electrode.

7. In paragraph 1, A jelly-roll type electrode assembly, wherein the width direction length of the above-mentioned flexible film is 95% or more and 105% or less based on 100% of the width direction length of the jelly-roll type electrode assembly.

8. In paragraph 1, A jelly-roll type electrode assembly wherein the thickness of the above-mentioned flexible film is 5% or more and 20% or less based on 100% of the thickness of the above-mentioned negative electrode.

9. In paragraph 1, A jelly-roll type electrode assembly wherein the thickness of the above soft film is 10 ㎛ or more and 50 ㎛ or less.

10. In paragraph 1, The positive electrode comprises a positive electrode current collector; and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, A jelly-roll type electrode assembly in which 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 cathode; a second separator and an anode are sequentially laminated and wound, (a) a step of winding the first separator and the second separator; (b) a step of inserting a flexible film between the first separator and the second separator; (c) a step of introducing the cathode; (d) a step of introducing the above anode; and (e) A step in which heating is performed by a heating means inserted into the hollow core of the jelly-roll type electrode assembly. Including, The longitudinal length of the above flexible film is 100% or more and 150% or less based on 100% of the inner circumference of the jelly-roll type electrode assembly, The tensile strength of the heated flexible film is 18 kgf / mm 2 More than 25 kgf / mm 2 A method for manufacturing a jelly-roll type electrode assembly as follows.

12. In paragraph 11, A method for manufacturing a jelly-roll type electrode assembly wherein the above heating means is a reformed pin.

13. In paragraph 12, A method for manufacturing a jelly-roll type electrode assembly, wherein the diameter of the reform pin is 70% or more and 90% or less of the diameter of the hollow core portion of 100%.

14. In paragraph 11, A method for manufacturing a jelly-roll type electrode assembly, wherein the heating is performed at a temperature of 50°C or higher and 80°C or lower for a time of 5 seconds or higher and 15 seconds or lower.

15. A jelly-roll type electrode assembly manufactured by the manufacturing method according to Article 11.

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

17. In paragraph 16, The above battery case is a secondary battery having a cylindrical shape.

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