Unit cell and method for manufacturing same

Abstract

The present invention relates to a unit cell and a method for manufacturing same. The objective of the present invention is to provide a unit cell and a method for manufacturing same, which can prevent folding and lifting of electrodes or separators during the manufacturing of a unit cell and a battery using the unit cell as a component, and can also prevent lifting of electrodes and separators during the use of the battery.

Description

Unit cell and method for manufacturing the same

[0001] The present invention relates to a unit cell and a method for manufacturing the same, and more particularly, to a unit cell and a method for manufacturing the same, which can prevent folding and lifting of electrodes or separators during the manufacturing of the unit cell and the manufacturing of a battery using the unit cell as a component, and which can prevent lifting of electrodes and separators during the use of the battery.

[0002] In general, secondary batteries are batteries that can be reused repeatedly through the process of discharging and charging in the reverse direction, converting chemical energy into electrical energy. Types include nickel-cadmium (Ni-Cd) batteries, nickel-metal hydride (Ni-MH) batteries, lithium-metal batteries, lithium-ion (Li-ion) batteries, and lithium-ion polymer batteries. Among these secondary batteries, lithium secondary batteries have been commercialized and are widely used due to their high energy density and voltage, long cycle life, and low self-discharge rate.

[0003] Charging and discharging of a lithium secondary battery proceeds as the process of lithium ions being inserted (intercalated) and removed (deintercalated) from the lithium metal oxide of the positive electrode to the negative electrode is repeated.

[0004] Secondary batteries can generally be manufactured by housing an electrode assembly, in which a cathode, a separator, and an anode are laminated and assembled, together with an electrolyte, in a case such as a cylindrical can or a square pouch.

[0005] Specifically, a unit cell is manufactured by cutting, laminating, etc. a cathode, a separator, and an anode in a pre-designed manner. The manufactured unit cells can be manufactured into an electrode assembly by laminating, folding, or rolling a set number of the manufactured unit cells.

[0006] During the process of manufacturing a unit cell, stacking, folding, or rolling the unit cell, the electrode may fold or the space between the separator and the electrode may be lifted, which may cause phenomena such as lithium ion precipitation in the future, resulting in a decrease in the lifespan and performance of the battery.

[0007] In addition, hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, and C are produced depending on the reaction within the lithium secondary battery. n H 2n-2 (n=2~5), C n H 2n (n=2~5), C n H 2n+2 Various types of gases, such as hydrocarbons and other organic gases, can be generated (n=1~5). Specifically, gases can be generated from electrolytes, active materials, and additives during the secondary battery charging and discharging process, and the contact between the separator and the electrode can be reduced due to gases generated between the separator and the electrode.

[0008] To solve these problems, a method of bonding the electrode and separator using an adhesive composition is being considered, but in the area where the adhesive is applied, the movement of electrolyte and lithium ions may be hindered during battery operation, and there is a concern that additional gas may be generated due to the adhesive.

[0009] The present invention relates to a unit cell and a method for manufacturing the same, and provides a unit cell and a method for manufacturing the same, which can prevent folding and lifting of an electrode or a separator without an adhesive composition during the manufacturing of a unit cell and the manufacturing of a battery using the unit cell as a component, and can prevent lifting of the electrode and separator during the use of the battery.

[0010] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0011] The unit cell according to the present invention is

[0012] anode;

[0013] A first separator laminated on one surface of the above anode;

[0014] A cathode laminated on the upper surface of the first separator; and

[0015] Including a second separator laminated on the upper surface of the above cathode,

[0016] The area of ​​each of the first separator and the second separator is larger than the area of ​​each of the cathode and the anode, and includes an edge area that does not contact the cathode and the anode,

[0017] The first separator and the second separator are bonded to each other at the edge region.

[0018] According to one aspect, the positive electrode includes a positive electrode binder, the negative electrode includes a negative electrode binder, the positive electrode binder includes a polyvinylidene fluoride (PVdF)-based material, the negative electrode binder includes at least one of a styrene butadiene rubber (SBR)-based material and a carboxymethyl cellulose (CMC), and the materials of the first separator and the second separator may include at least one of polyethylene (PE) and polypropylene (PP).

[0019] According to one aspect, the positive electrode includes a first positive electrode composite layer including a positive electrode active material, a conductive material, and the positive electrode binder, a positive electrode current collector laminated on an upper surface of the first positive electrode composite layer, and a second positive electrode composite layer laminated on an upper surface of the positive electrode current collector and including the positive electrode active material, a conductive material, and the positive electrode binder, and the second positive electrode composite layer may be bonded to the first separator by the positive electrode binder.

[0020] According to one aspect, a region of the first separator and the second separator facing each other that does not face the cathode is referred to as a bonding target region, and the bonding target region includes a bonding region where the first separator and the second separator are bonded to each other and a non-bonding region where the first separator and the second separator are not bonded to each other, and the bonding region may have an area ratio of 0.5 to 0.9 relative to the area of ​​the bonding target region.

[0021] According to one aspect, the non-bonded region has an area ratio of 0.1 to 0.5 relative to the area of ​​the bonding target region, and may form a flow path region through which gas generated from the cathode is discharged or electrolyte is introduced into the cathode.

[0022] According to one aspect, the cathode, the first separator and the second separator may have a rectangular shape extending in a first direction and a second direction perpendicular to the first direction.

[0023] According to one aspect, the cathode, the first separator, and the second separator have a length in the first direction that is longer than a length in the second direction, the bonding target area is formed on both sides with the cathode as the center with respect to the second direction, and a length of the bonding target area in the second direction from one end of the cathode in the second direction may be 1% to 70% of the length of the cathode in the second direction.

[0024] According to one aspect, the length of the euro area in the second direction may be from one end of the cathode in the second direction to the edge of the first separator or the edge of the second separator.

[0025] According to one aspect, the euro area may be divided into a plurality of sub-areas, and each of the plurality of sub-areas may be spaced apart from each other by a predetermined interval in the first direction.

[0026] The method for manufacturing a unit cell of the present invention is as follows:

[0027] Step of preparing the anode (S1);

[0028] Step (S2) of laminating a first separator on one surface of the above anode;

[0029] Step (S3) of laminating a cathode on the upper surface of the first separator;

[0030] Step (S4) of laminating a second separator on the upper surface of the cathode;

[0031] The method may include a step (S5) of applying heat and pressure to the laminated anode, cathode, first separator, and second separator to bond them, wherein the area of ​​each of the first separator and the second separator is larger than the area of ​​each of the cathode and the anode, and includes an edge area that does not contact the cathode and the anode, and bonding the edge areas of the first separator and the second separator to each other.

[0032] According to one aspect, in the step S5, the edges of the first separator and the second separator are regions that do not face the cathode among regions where the first separator and the second separator face each other, and are a region to be bonded, and the region to be bonded includes a region where the first separator and the second separator are bonded and a non-bonded region where the first separator and the second separator are not bonded, and the non-bonded region may form a flow path region that allows a gas generated from the cathode to be discharged or an electrolyte to be introduced into the cathode.

[0033] According to one aspect, in the step S5, the heat blocking means may be brought into contact with the euro area.

[0034] According to one aspect, in the step S5, a heating means may be brought into contact with the bonding area.

[0035] The unit cell of the present invention and its manufacturing method can prevent folding and lifting of electrodes or separators during the manufacturing of the unit cell and the manufacturing of a battery using the unit cell as a component, and can also prevent lifting of electrodes and separators during the use of the battery.

[0036] The unit cell of the present invention and its manufacturing method can prevent the lifespan and performance of a battery from deteriorating by preventing the electrode from folding or the separator and electrode from lifting during the process of manufacturing the unit cell or the process of stacking, folding or rolling the unit cell.

[0037] The unit cell according to the present invention can easily discharge gas generated between the separator and the electrode, thereby preventing deterioration of contact between the separator and the electrode.

[0038] In the unit cell according to the present invention, the positive electrode is bonded to the first separator by a binder contained in the positive electrode composite layer without a separate adhesive composition, and the negative electrode is physically fixed between the first separator and the second separator, so that gas generation or deterioration of battery performance due to the use of the adhesive composition can be prevented.

[0039] Figure 1 is an exploded perspective view showing a unit cell according to one embodiment.

[0040] Figure 2 is a cross-sectional view showing the laminated structure of a unit cell.

[0041] Figure 3 is a conceptual diagram showing a bonding target area of ​​a unit cell according to one embodiment.

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Throughout this process, the sizes and shapes of components depicted in the drawings may be exaggerated for clarity and convenience. Furthermore, terms specifically defined in consideration of the structure and operation of the present invention may vary depending on the intentions or practices of the user or operator. Definitions of these terms should be based on the overall content of this specification.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms “center,” “upper,” “lower,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “one side,” “other side,” etc., is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is normally placed when used, and is only for the purpose of explaining and briefly explaining the present invention, and does not suggest or imply that the indicated device or element must have a specific orientation and be configured or operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0044] Fig. 1 is an exploded perspective view schematically illustrating the structure of a unit cell according to one embodiment of the present invention. Fig. 2 is a cross-sectional view illustrating the laminated structure of a unit cell. Fig. 3 is a conceptual diagram illustrating a bonding target area of ​​a unit cell.

[0045] Hereinafter, the unit cell of the present invention will be described with reference to FIGS. 1 to 3. In the following description, the x-axis direction illustrated in FIGS. 1 to 3 is a first direction, the y-axis direction is a second direction, and the z-axis direction is an up-down direction.

[0046] A unit cell may be a minimum unit cell including one anode (100) and one cathode (300). That is, the unit cell may be a monocell. More specifically, the unit cell may include two separators (200, 400), one anode (100), and one cathode (300).

[0047] The unit cell of the present invention can be processed into an electrode assembly by folding, rolling, or multiply stacking and used. The unit cell of the present invention can be used in square batteries, cylindrical batteries, pouch-shaped batteries, etc. Preferably, it can be used in pouch-shaped batteries.

[0048] As shown in Figure 1, the unit cell is

[0049] Bipolar (100);

[0050] A first separator (200) laminated on the upper surface of the above anode (100);

[0051] A cathode (300) laminated on the upper surface of the first separator (200); and

[0052] It may include a second separator (400) laminated on the upper surface of the above cathode (300).

[0053] The area of ​​each of the first separator (200) and the second separator (400) is larger than the area of ​​each of the negative electrode (300) and the positive electrode (100), and includes an edge region (shaded region) that does not contact the negative electrode (300) and the positive electrode (100), and the edge regions of the first separator (200) and the second separator (400) can be joined to each other as separators (200, 400). Specifically, the positive electrode (100) can be joined to the first separator (200), and the negative electrode (300) can be sandwiched and fixed between the first separator (200) and the second separator (400).

[0054] The positive electrode (100) includes a positive electrode binder, and the negative electrode (300) includes a negative electrode binder. The positive electrode binder may include a polyvinylidene fluoride (PVdF)-based binder, and the negative electrode binder may include at least one of a styrene-butadiene rubber (SBR)-based binder and a carboxymethyl cellulose (CMC). At this time, the materials of the first separator (200) and the second separator (400) may include at least one of polyethylene (PE) and polypropylene (PP). Therefore, the positive electrode (100) can be bonded to the first separator (200) by appropriate heat and pressure without a separate adhesive due to the positive electrode binder material.

[0055] In addition, the cathode (300) is sandwiched between the first separator (200) and the second separator (400), and the edges of the first separator (200) and the second separator (400) are bonded by appropriate heat and pressure, so that they can be fixed without a separate adhesive.

[0056] As described above, the unit cell can prevent folding, lifting, etc. by combining and fixing the positive electrode (100), negative electrode (300), first separator (200), and second separator (400) to each other. In addition, the unit cell can be stably maintained in an unfolded state even during processes such as movement, rolling, and folding.

[0057] FIG. 2 illustrates in more detail the laminated structure of a unit cell according to one embodiment. As illustrated in FIG. 2, the positive electrode (100) may include a first positive electrode composite layer (110) including a positive electrode active material, a conductive material, and the positive electrode binder, a positive electrode current collector (130) laminated on an upper surface of the first positive electrode composite layer (110), and a second positive electrode composite layer (120) laminated on an upper surface of the positive electrode current collector (130) and including the positive electrode active material, a conductive material, and the positive electrode binder. At this time, the second positive electrode composite layer (120) may be bonded to the first separator (200) by the positive electrode binder without a separate adhesive.

[0058] As illustrated in FIG. 2, the negative electrode (300) may include a first negative electrode composite layer (310) including a negative electrode active material, a conductive material, and the negative electrode binder, a negative electrode current collector (330) laminated on an upper surface of the first negative electrode composite layer (310), and a second negative electrode composite layer (320) laminated on an upper surface of the negative electrode current collector (330) and including the negative electrode active material, the conductive material, and the negative electrode binder. The first negative electrode composite layer (310) may face the first separator (200), and the second negative electrode composite layer (320) may face the second separator (400).

[0059] The cathode active material may be LCO (lithium cobalt oxide), LMO (lithium manganese oxide), NCM (nickel cobalt manganese), NCA (nickel cobalt aluminum), LFP (lithium iron phosphate), etc.

[0060] The negative active material can be a graphite-based material, a silicon-based material, etc.

[0061] The conductive material is not particularly limited as long as it is used as a conductive material in the technical field to which the present invention belongs, and includes, for example, a carbon-based conductive material and a metal-based conductive material, and specific examples thereof include graphite such as natural graphite, artificial graphite, and graphene; carbon black such as acetylene black, Ketjen black, channel black, paneth black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbons; conductive metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; and conductive organic compounds such as polyphenylene derivatives; and the like, and preferably, the conductive material may be a carbon-based conductive material.

[0062] The positive electrode binder may be a polyvinylidene fluoride (PVdF)-based binder. Specific examples of the PVdF-based binder include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), polyvinylidene fluoride-co-trichloroethylene (PVdF-TCE), poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVdF-CTFE), poly(vinylidene fluoride-co-tetrafluoroethylene) (PVdF-TFE), and poly(vinylidene fluoride-co-trifluoroethylene (PVdF-TrFE).

[0063] In order to enable the positive electrode and the separator to be bonded by heat and pressure without an adhesive, the positive electrode binder is preferably fused at a temperature of 70°C or higher or 80°C or higher under a given pressure, and in order to prevent degradation of the secondary battery life performance, it is preferable not to melt at a temperature lower than that.

[0064] The cathode binder may be a styrene-butadiene rubber (SBR)-based binder or carboxymethylcellulose (CMC).

[0065] The SBR binder may be, for example, at least one selected from the group consisting of styrene-butadiene rubber (SBR) and acrylated styrene-butadiene rubber.

[0066] FIG. 3 is a conceptual diagram illustrating a bonding target area of ​​a unit cell according to one embodiment. As illustrated in FIG. 3, an area (entire shaded area) that does not face the cathode (300) among areas where the first separator (not shown) and the second separator (400) face each other is a bonding target area (500). The bonding target area (500) may include a bonding area (510) where the first separator (not shown) and the second separator are bonded to each other and a flow path area (520) where the first separator (not shown) and the second separator are not bonded to each other. The area ratio of the entire bonding area (510) to the entire area of ​​the bonding target area (500) may be 0.5 to 0.9, and the area ratio of the entire flow path area (520) may be 0.1 to 0.5. Preferably, the area ratio of the entire flow area (520) to the entire area of ​​the bonding target area (500) may be 0.15 or more, 0.2 or more, or 0.25 or more, and 0.45 or less, 0.4 or less, or 0.35 or less, and more preferably 0.28 to 0.32, or about 0.3. The flow area (520) allows gas generated from the cathode (300) to be discharged or allows the cathode (300) to be impregnated more quickly during electrolyte impregnation.

[0067] Specifically, when the completed secondary battery is charged or discharged, gas generated from the negative active material or the negative electrode (300) portion is discharged through the flow region (520), and the phenomenon of the first separator (200) or the second separator (400) being lifted from the negative electrode (300) can be prevented.

[0068] In addition, in the process of housing the electrode assembly in the battery case during the secondary battery manufacturing process and then injecting the electrolyte into the battery case, the electrolyte flows into the negative electrode (300) more quickly through the flow path area (520), so that the negative electrode active material can be impregnated more quickly.

[0069] According to a preferred embodiment, the cathode (300), the first separator (200), and the second separator (400) may be provided in a rectangular shape with sides in the first direction (x) and the second direction (y). As a more specific example, the cathode (300) may be provided in a rectangular shape whose length in the first direction (x) is longer than its length in the second direction (y). At this time, a lead tab (not shown) for electrical connection with the outside may be connected to the side of the cathode (300) extending in the second direction. The flow path area (520) may not be provided in the flow path area (500) that is in contact with the side of the cathode (300) extending in the second direction. Since the lead tab may be formed in the area, gas may be discharged through the lead tab, and formation of an additional flow path area (520) together with the lead tab may become structurally unstable.

[0070] The above-mentioned bonding target area (500) includes areas formed on both sides with the cathode (300) as the center with respect to the second direction, and the length (width) of the bonding target area (500) from one end of the cathode (300) in the second direction may be 1% to 70% of the length (width) of the cathode (300) in the second direction, for example, 2% or more, 3% or more, 4% or more, 5% or more, and 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, or 30% or less. The length may be determined in consideration of physical properties such as rigidity of the first separator (200) and the second separator (400). Preferably, the length (width) of the bonding target area (500) in the second direction from one end of the cathode (300) may be formed to be 3% to 50% of the length (width) of the cathode (300) in the second direction. More preferably, the length (width) of the bonding target area (500) in the second direction from one end of the cathode (300) may be formed to be 5% to 30% of the length (width) of the cathode (300) in the second direction. For example, the length (width) of the bonding target area (500) in the second direction from one end of the cathode (300) may be 40 μm to 100 μm.

[0071] The length of the euro area (520) in the second direction from one end of the cathode (300) in the second direction may be to the edge of the first separator (200) or the edge of the second separator (400).

[0072] The above-mentioned flow region (520) may be one, but as illustrated in FIG. 3, the flow region (520) may be divided into a plurality of sub-regions at the end of the cathode (300) in the second direction, and each of the plurality of sub-regions may be spaced apart from each other by a predetermined distance in the first direction. The spacing may or may not be constant. The length of each of the plurality of sub-regions in the first direction may be the same or different. That is, the flow region (520) is divided into a plurality of sub-regions, and each of the plurality of sub-regions is spaced apart from each other by a predetermined distance in the first direction, and each of the plurality of sub-regions may have one end connected to the cathode (300) in the second direction and the other end touching the edge of the first separator (200) or the second separator (400). Therefore, the gas generated at the cathode (300) can be discharged outside the area surrounded by the first separator (200) and the second separator (400) through the euro area (520).

[0073] When the unit cell of the present invention is used in the manufacture of a jelly roll type electrode, the length and spacing between the junction region (510) and the flow region (520) can be appropriately changed considering that the curvature of the center is greater.

[0074] A unit cell manufacturing method for manufacturing a unit cell of the present invention,

[0075] Step (S1) of preparing the positive electrode (100);

[0076] Step (S2) of laminating a first separator (200) on one surface of the above anode (100);

[0077] Step (S3) of laminating a cathode (300) on the upper surface of the first separator (200);

[0078] Step (S4) of laminating a second separator (400) on the upper surface of the cathode (300); and

[0079] The method may include a step (S3S5) of bonding the stacked positive electrode (100), the negative electrode (300), the first separator (200) and the second separator (400) by applying heat and pressure, wherein the area of ​​each of the first separator (200) and the second separator (400) is larger than the area of ​​each of the positive electrode (100) and the negative electrode (300) and includes an edge area that does not contact the negative electrode and the positive electrode, and bonding the edge areas of the first separator (200) and the second separator (400) to each other.

[0080] According to a preferred embodiment, in the step S5, the edges of the first separator (200) and the second separator (400) are regions where the first separator (200) and the second separator (400) face each other, and are regions that do not face the cathode (300), and are a bonding target region (500), and the bonding target region (500) includes a bonding region (510) where the first separator (200) and the second separator (400) are bonded and a non-bonding region where they are not bonded, and the non-bonding region may form a flow path region (520) that allows a gas generated from the cathode (300) to be discharged or an electrolyte to be introduced into the cathode (300).

[0081] Specifically, in the above step S5, a heat blocking means may be in contact with the euro area (520), and a heating means may be in contact with the bonding area (510).

[0082] The heat-blocking means may be a block of insulating material or a cooling jig equipped with a heat-dissipating means capable of rapidly dissipating heat to the outside. When the anode, first separator, cathode, and second separator are laminated under heat and pressure, such heat-blocking means can be used to secure a flow path area.

[0083] The heating means may be a heating jig equipped with an IR heater, etc. In order to allow the first separator and the anode, or the first separator and the second separator to be bonded to each other only by heat and pressure without an adhesive, it is preferable to apply a predetermined pressure. It is preferable that the heating temperature of the heating jig be adjustable to 60 to 200°C.

[0084] While the embodiments of the present invention have been described above, they are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible. Therefore, the true scope of technical protection of the present invention should be defined by the following claims.

[0085] [Explanation of symbols]

[0086] 100...Anode 110...First cathode composite layer 120...Second cathode composite layer 130...Anode current collector 200...First separator 300...Anode 310...First cathode composite layer 320...Second cathode composite layer 330...Anode current collector 400...Second separator 500...Bonding target area 510...Bonding area 520...Flow path area

Claims

1. Bipolar; A first separator laminated on one surface of the above anode; A cathode laminated on the upper surface of the first separator; and Including a second separator laminated on the upper surface of the above cathode, The area of ​​each of the first separator and the second separator is larger than the area of ​​each of the cathode and the anode, and includes an edge area that does not contact the cathode and the anode, A unit cell in which the first separator and the second separator are joined to each other at the edge regions.

2. In paragraph 1, The above positive electrode includes a positive electrode binder, The above cathode includes a cathode binder, The above positive electrode binder comprises polyvinylidene fluoride (PVdF) system, The above negative electrode binder includes at least one of styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC), A unit cell in which the material of the first separator and the second separator includes at least one of polyethylene (PE) and polypropylene (PP).

3. In paragraph 2, The above anode is, A first positive electrode composite layer including a positive electrode active material, a conductive material, and the positive electrode binder, A positive electrode current collector laminated on the upper surface of the first positive electrode composite layer, A second positive electrode composite layer is laminated on the upper surface of the positive electrode collector and includes the positive electrode active material, a conductive material, and the positive electrode binder, A unit cell in which the second anode composite layer is bonded to the first separator by the anode binder.

4. In paragraph 1, Among the areas where the first separator and the second separator face each other, an area that does not face the cathode is a bonding target area, and the bonding target area includes a bonding area where the first separator and the second separator are bonded to each other and a non-bonding area where the first separator and the second separator are not bonded to each other. A unit cell in which the area of ​​the above bonding region has an area ratio of 0.5 to 0.9 compared to the area of ​​the above bonding target region.

5. In paragraph 4, A unit cell in which the non-bonded region has an area ratio of 0.1 to 0.5 compared to the area of ​​the bonding target region, and forms a flow path region through which gas generated from the cathode is discharged or electrolyte is introduced into the cathode.

6. In paragraph 5, A unit cell, wherein the cathode, the first separator, and the second separator have a rectangular shape extending in a first direction and a second direction perpendicular to the first direction.

7. In paragraph 6, The cathode, the first separator, and the second separator have a length in the first direction that is longer than a length in the second direction, The above bonding target area is formed on both sides centered on the cathode with respect to the second direction, A unit cell, wherein the length of the bonding target region in the second direction from one end of the cathode is 1% to 70% of the length of the cathode in the second direction.

8. In paragraph 6, A unit cell in which the length in the second direction of the euro area is from one end of the cathode in the second direction to the edge of the first separator or the edge of the second separator.

9. In paragraph 8, The above Euro area is divided into multiple sub-areas, A unit cell in which each of the plurality of detailed regions is spaced apart from each other by a predetermined interval in the first direction.

10. Step of preparing the positive electrode (S1); Step (S2) of laminating a first separator on one surface of the above anode; Step (S3) of laminating a cathode on the upper surface of the first separator; Step (S4) of laminating a second separator on the upper surface of the cathode; A method for manufacturing a unit cell, comprising the step of applying heat and pressure to the laminated anode, cathode, first separator, and second separator to bond them, wherein the area of ​​each of the first separator and the second separator is larger than the area of ​​each of the cathode and the anode, and includes an edge area that does not come into contact with the cathode and the anode, and bonding the edge areas of the first separator and the second separator to each other (S5).

11. In paragraph 10, In the above step S5, the edges of the first separator and the second separator are the areas where the first separator and the second separator face each other, and are the areas that do not face the cathode and are the areas to be bonded, A method for manufacturing a unit cell, wherein the above-mentioned bonding target region includes a bonding region where the first separator and the second separator are bonded and a non-bonding region where the first separator and the second separator are not bonded, and the non-bonding region forms a flow path region through which gas generated from the negative electrode is discharged or electrolyte is introduced into the negative electrode.

12. In paragraph 11, In the above step S5, A method for manufacturing a unit cell in which a heat-blocking means is in contact with the above-mentioned euro area.

13. In paragraph 11, In the above step S5, A method for manufacturing a unit cell in which a heating means is in contact with the above-mentioned bonding area.

14. A secondary battery comprising a unit cell according to paragraph 1.

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