Unit cell and method for manufacturing the same

Abstract

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 in which bending and lifting of electrodes or separator membranes are prevented during the manufacturing of the unit cell and the manufacturing of a battery using the unit cell as a component, and in which lifting of electrodes and separator membranes is prevented during the battery's use.

Description

Technical Field

[0001] The present invention relates to a unit cell and a method for manufacturing the same, and prevents bending and lifting phenomena of electrodes or separator membranes during the manufacturing of unit cells and during the manufacturing of batteries using unit cells as components. The present invention also relates to a unit cell and a method for manufacturing the same that can prevent the lifting phenomenon of electrodes and separator membranes even during the use process of the battery.

Background Art

[0002] Generally, a secondary battery is a battery that can be repeatedly used through discharge that converts chemical energy into electrical energy and a charging process in the reverse direction. Types of secondary batteries 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 (Li-ion Polymer Battery). Among these secondary batteries, lithium secondary batteries, which have a high energy density, voltage, long cycle life, and low self-discharge rate, have been commercialized and widely used.

[0003] The charge and discharge of a lithium secondary battery proceed while the process of insertion (Intercalation) and desorption (Deintercalation) of lithium ions from the lithium metal oxide of the positive electrode to the negative electrode is repeated.

[0004] A secondary battery can generally be manufactured by housing an electrode assembly in which a positive electrode (Cathode), a separator (Separator), and a negative electrode (Anode) are laminated and assembled together with an electrolyte in a case such as a cylindrical can or a rectangular pouch.

[0005] Specifically, a unit cell is manufactured by cutting, laminating, etc. the positive electrode, separator, and negative electrode in a pre-designed manner. The manufactured unit cells can be laminated, folded, or rolled in a predetermined quantity to manufacture an electrode assembly.

[0006] During the manufacturing process of a unit cell, or during the stacking, folding, or rolling of unit cells, electrodes may break or the gap between the separator membrane and the electrode may lift. This can lead to phenomena such as future lithium ion deposition, resulting in a decrease in battery life and performance.

[0007] Furthermore, hydrogen, oxygen, nitrogen, carbon monoxide, carbon dioxide, and C are produced through reactions 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 gases are generated, including hydrocarbons and other organic gases (n=1~5). Specifically, gases can be generated from the electrolyte, active material, and additives during the charging and discharging process of a secondary battery, and the gases generated between the separation membrane and the electrode reduce the contact between the separation membrane and the electrode.

[0008] To solve these problems, a method of joining the electrode and the separation membrane using an adhesive composition has been considered. However, in the area where the adhesive is applied, the movement of the electrolyte and lithium ions may be hindered when the battery is powered, and there is a risk of further gas generation from the adhesive. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention relates to a unit cell and a method for manufacturing the same, and aims to provide a unit cell and a method for manufacturing the same in which bending and lifting of electrodes or separator membranes are prevented even without an adhesive composition during the manufacturing of the unit cell and the manufacturing of a battery using the unit cell as a component, and in which lifting of electrodes and separator membranes is prevented during the battery's use.

[0010] The technical problems that this invention aims to solve are not limited to those described above, and any other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0011] The unit cell according to the present invention includes a positive electrode; a first separation membrane laminated on one surface of the positive electrode; a negative electrode laminated on the upper surface of the first separation membrane; and a second separation membrane laminated on the upper surface of the negative electrode; wherein the area of ​​the first separation membrane and the second separation membrane are larger than the area of ​​the negative electrode and the positive electrode, respectively, and include an edge region that does not contact the negative electrode and the positive electrode, and the first separation membrane and the second separation membrane are joined to each other at the edge region.

[0012] According to one embodiment, 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) system, the negative electrode binder includes one or more of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC), and the materials of the first and second separation membranes include one or more of polyethylene (PE) and polypropylene (PP).

[0013] According to one embodiment, the positive electrode includes a first positive electrode composite layer containing 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; and a second positive electrode composite layer laminated on the upper surface of the positive electrode current collector, containing the positive electrode active material, a conductive material, and the positive electrode binder, wherein the second positive electrode composite layer is bonded to the first separator membrane by the positive electrode binder.

[0014] According to one embodiment, the region in which the first separation membrane and the second separation membrane face each other, the region that does not face the negative electrode, is defined as the bonding target region, and the bonding target region includes a bonding region in which the first separation membrane and the second separation membrane are bonded to each other and a non-bonding region in which they are not bonded to each other, and the bonding region has an area ratio of 0.5 to 0.9 compared to the area of ​​the bonding target region.

[0015] According to one embodiment, the non-bonded region has an area ratio of 0.1 to 0.5 compared to the area of ​​the bonding target region, and also forms a flow channel region through which gas generated at the negative electrode is discharged or electrolyte flows into the negative electrode.

[0016] According to one embodiment, the negative electrode, the first separation membrane, and the second separation membrane are also rectangular in shape, extending in a first direction and a second direction perpendicular to the first direction.

[0017] According to one embodiment, the negative electrode, the first separator membrane, and the second separator membrane have a length in the first direction that is even longer than their length in the second direction, the bonding target region is formed on both sides of the negative electrode with respect to the second direction, and the length of the bonding target region in the second direction from one end of the negative electrode in the second direction is 1 to 70% of the length of the negative electrode in the second direction.

[0018] According to one embodiment, the length of the flow channel region in the second direction is also from one end of the negative electrode in the second direction to the edge of the first separation membrane or the edge of the second separation membrane.

[0019] According to one embodiment, the flow path region is divided into a plurality of detailed regions, and each of the plurality of detailed regions is separated from each other at a predetermined interval in the first direction.

[0020] The method for manufacturing a unit cell of the present invention includes the steps of: preparing a positive electrode (step S1); laminating a first separation membrane onto one surface of the positive electrode (step S2); laminating a negative electrode onto the upper surface of the first separation membrane (step S3); laminating a second separation membrane onto the upper surface of the negative electrode (step S4); and bonding the laminated positive electrode, negative electrode, first separation membrane, and second separation membrane by applying heat and pressure, wherein the respective areas of the first separation membrane and the second separation membrane are larger than the respective areas of the negative electrode and the positive electrode, and include edge regions that do not come into contact with the negative electrode and the positive electrode, and joining the edge regions of the first separation membrane and the second separation membrane to each other (step S5).

[0021] According to one aspect, in step S5, the edges of the first separation membrane and the second separation membrane are a bonding target region as a region that does not face the negative electrode among the regions where the first separation membrane and the second separation membrane face each other. The bonding target region includes a bonded region where the first separation membrane and the second separation membrane are bonded and a non-bonded region where they are not bonded. The non-bonded region forms a flow path region for discharging the gas generated at the negative electrode or allowing the electrolyte to flow into the negative electrode.

[0022] According to one aspect, in step S5, a heat insulation means also contacts the flow path region.

[0023] According to one aspect, in step S5, a heating means also contacts the bonded region.

Advantages of the Invention

[0024] The unit cell and its manufacturing method of the present invention prevent the bending and lifting phenomena of the electrode or the separation membrane in the manufacturing stage of the unit cell and the manufacturing stage of the battery using the unit cell as a component, and can also prevent the lifting phenomenon of the electrode and the separation membrane during the use process of the battery.

[0025] The unit cell and its manufacturing method of the present invention can prevent the reduction of the battery life and performance by preventing the electrode from breaking or the lifting of the separation membrane and the electrode during the process of manufacturing the unit cell, laminating, folding or rolling the unit cell.

[0026] The unit cell according to the present invention can easily discharge the gas generated between the separation membrane and the electrode, so that it can prevent the reduction of the contact property between the separation membrane and the electrode.

[0027] The unit cell according to the present invention, without a separate adhesive composition, the positive electrode is bonded to the first separation membrane by a binder contained in the positive electrode composite layer, and the negative electrode is physically fixed between the first separation membrane and the second separation membrane, so that it can prevent the gas generation and the reduction of the battery performance caused by the use of the adhesive composition. [Brief explanation of the drawing]

[0028] [Figure 1] This is an exploded perspective view showing a unit cell according to one embodiment. [Figure 2] This is a cross-sectional view showing the stacked structure of a unit cell. [Figure 3] This is a conceptual diagram showing the region to be joined to a unit cell according to one embodiment. [Modes for carrying out the invention]

[0029] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In this process, the size and shape of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, terms specifically defined in consideration of the configuration and operation of the present invention may vary depending on the intent or convention of the user or operator. Definitions of such terms should be based on the overall content of this specification.

[0030] In describing the present invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "up," "down," "left," "right," "vertical," "horizontal," "inside," "outside," "one side," and "other side" are based on the directions or positional relationships shown in the drawings, or the directions or positional relationships in which the product of the present invention is typically arranged during use. They are merely for the purpose of describing and briefly explaining the present invention, and do not imply or suggest that the displayed device or element must necessarily be configured or operated in a specific direction, and should not be understood as limiting the present invention.

[0031] Figure 1 is an exploded perspective view schematically showing the structure of a unit cell according to one embodiment of the present invention. Figure 2 is a cross-sectional view showing the stacked structure of the unit cell. Figure 3 is a conceptual diagram showing the joining target region of the unit cell.

[0032] The unit cell of the present invention will be described below with reference to Figures 1 to 3. In the following description, the x-axis direction shown in Figures 1 to 3 is the first direction, the y-axis direction is the second direction, and the z-axis direction is the up and down direction.

[0033] A unit cell is also the smallest unit cell containing one positive electrode 100 and one negative electrode 300. In other words, a unit cell is also a monocell. More specifically, a unit cell may contain two separation membranes 200 and 400, one positive electrode 100, and one negative electrode 300.

[0034] The unit cells of the present invention are folded, rolled, or stacked in multiples to form electrode assemblies for use. The unit cells of the present invention are used in prismatic batteries, cylindrical batteries, pouch-type batteries, etc. Preferably, they are used in pouch-type batteries.

[0035] As shown in Figure 1, the unit cell includes a positive electrode 100; a first separation membrane 200 laminated on the upper surface of the positive electrode 100; a negative electrode 300 laminated on the upper surface of the first separation membrane 200; and a second separation membrane 400 laminated on the upper surface of the negative electrode 300.

[0036] The areas of the first separation membrane 200 and the second separation membrane 400 are larger than the areas of the negative electrode 300 and the positive electrode 100, respectively, and include edge regions (shaded areas) that do not come into contact with the negative electrode 300 and the positive electrode 100. The edge regions of the first separation membrane 200 and the second separation membrane 400 are joined together by the separation membranes 200 and 400. Specifically, the positive electrode 100 is joined to the first separation membrane 200, and the negative electrode 300 is sandwiched and fixed between the first separation membrane 200 and the second separation membrane 400.

[0037] The positive electrode 100 includes a positive electrode binder, and the negative electrode 300 includes a negative electrode binder. The positive electrode binder includes a polyvinylidene fluoride (PVdF)-based binder, and the negative electrode binder includes one or more of styrene-butadiene rubber (SBR)-based and carboxymethylcellulose (CMC). In this case, the materials of the first separation membrane 200 and the second separation membrane 400 may include one or more of polyethylene (PE) and polypropylene (PP). Therefore, the positive electrode 100 is bonded to the first separation membrane 200 by the positive electrode binder material with appropriate heat and pressure without the need for a separate adhesive.

[0038] Furthermore, the negative electrode 300 is sandwiched between the first separation membrane 200 and the second separation membrane 400, and the edges of the first separation membrane 200 and the second separation membrane 400 are joined by appropriate heat and pressure, so it is fixed without the need for a separate adhesive.

[0039] As mentioned above, the unit cell is prevented from bending or lifting by the bonding and fixing of the positive electrode 100, negative electrode 300, first separation membrane 200, and second separation membrane 400 to each other. Furthermore, it can maintain a stable, unfolded state even during processes such as movement, rolling, and folding of the unit cell.

[0040] Figure 2 illustrates in more detail the stacked structure of a unit cell according to one embodiment. As shown in Figure 2, the positive electrode 100 includes a first positive electrode composite layer 110 containing a positive electrode active material, a conductive material, and the positive electrode binder; a positive electrode current collector 130 laminated on the upper surface of the first positive electrode composite layer 110; and a second positive electrode composite layer 120 laminated on the upper surface of the positive electrode current collector 130, containing the positive electrode active material, a conductive material, and the positive electrode binder. In this case, the second positive electrode composite layer 120 is bonded to the first separator membrane 200 by the positive electrode binder without the need for a separate adhesive.

[0041] As shown in Figure 2, the negative electrode 300 includes a first negative electrode composite layer 310 containing a negative electrode active material, a conductive material, and the negative electrode binder; a negative electrode current collector 330 laminated on the upper surface of the first negative electrode composite layer 310; and a second negative electrode composite layer 320 laminated on the upper surface of the negative electrode current collector 330, which also contains the negative electrode active material, a conductive material, and the negative electrode binder. The first negative electrode composite layer 310 faces the first separation membrane 200, and the second negative electrode composite layer 320 faces the second separation membrane 400.

[0042] Positive electrode active materials include LCO (lithium cobalt oxide), LMO (lithium manganese oxide), NCM (nickel cobalt manganese), NCA (nickel cobalt aluminum), and LFP (lithium iron phosphate).

[0043] The negative electrode active material can be graphite-based, silicon-based, or other materials.

[0044] The conductive material is not particularly limited as long as it is used as a conductive material in the art to which the present invention belongs, but as an example, it includes carbon-based conductive materials and metal-based conductive materials, and as a specific example, it is one or more selected from the group consisting of graphite such as natural graphite, artificial graphite, and graphene; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; 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 preferably it is also a carbon-based conductive material.

[0045] The positive electrode binder is also a polyvinylidene fluoride (PVdF) type binder. Specific examples of PVdF type binders include one or more 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).

[0046] To bond the positive electrode and the separator membrane using heat and pressure without adhesive, it is desirable that the positive electrode binder be fused at 70°C or above, or 80°C or above, under a predetermined pressure. To prevent a decrease in the performance of the secondary battery's lifespan, it is desirable that it not melt at temperatures below these levels.

[0047] The negative electrode binder is either a styrene-butadiene rubber (SBR) binder or carboxymethylcellulose (CMC).

[0048] SBR-based binders are, as a specific example, one or more selected from the group consisting of styrene-butadiene rubber (SBR) and styrene-butadiene acrylate rubber.

[0049] Figure 3 is a conceptual diagram showing the joining target region of a unit cell according to one embodiment. As shown in Figure 3, the joining target region 500 is the region where the first separation membrane (not shown) and the second separation membrane 400 face each other, but which does not face the negative electrode 300 (the entire shaded area). The joining target region 500 may include a joining region 510 where the first separation membrane (not shown) and the second separation membrane are joined to each other, and a flow channel region 520 where they are not joined to each other. The area ratio of the entire joining region 510 to the total area of ​​the joining target region 500 is 0.5 to 0.9, and the area ratio of the entire flow channel region 520 is 0.1 to 0.5. Preferably, the area ratio of the total flow channel region 520 to the total area of ​​the bonding target region 500 is 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 channel region 520 allows gas generated in the negative electrode 300 to be discharged, or allows the negative electrode 300 to be impregnated more quickly during electrolyte impregnation.

[0050] Specifically, when the completed secondary battery is charged or discharged, the gas generated in the negative electrode active material or at the negative electrode 300 is discharged through the flow path region 520, preventing the first separation membrane 200 or the second separation membrane 400 from floating away from the negative electrode 300.

[0051] Furthermore, in the secondary battery manufacturing process, after the electrode assembly is placed in the battery case, the electrolyte is injected into the battery case. In this process, the electrolyte flows into the negative electrode 300 more quickly through the flow channel region 520, thereby impregnating the negative electrode active material more rapidly.

[0052] In a preferred embodiment, the negative electrode 300, the first separation membrane 200, and the second separation membrane 400 may be rectangular in shape with sides in the first direction (x) and the second direction (y). In a more specific example, the negative electrode 300 may be rectangular in shape with a length in the first direction (x) being longer than the length in the second direction (y). In this case, a lead tab (not shown) for electrical connection with the outside is connected to the side of the negative electrode 300 extending in the second direction. In the joining target area 500, a flow channel area 520 may not be provided in the joining target area that is in contact with the side of the negative electrode 300 extending in the second direction. This is because a lead tab is formed in this area, and gas may be discharged through the lead tab, and the formation of an additional flow channel area 520 together with the lead tab would be structurally unstable.

[0053] The bonding target region 500 includes regions formed on both sides of the negative electrode 300 with respect to the second direction, and the length (width) of the bonding target region 500 in the second direction from one end of the negative electrode 300 is 1 to 70% of the length (width) of the negative electrode 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 is determined considering the physical properties such as the rigidity of the first separation membrane 200 and the second separation membrane 400. Preferably, the length (width) of the bonding target region 500 in the second direction from one end of the negative electrode 300 is also formed to be 3 to 50% of the length (width) of the negative electrode 300 in the second direction. More preferably, the length (width) of the bonding target region 500 in the second direction from one end of the negative electrode 300 is formed to be 5-30% of the length (width) of the negative electrode 300 in the second direction. For example, the length (width) of the bonding target region 500 in the second direction from one end of the negative electrode 300 is 40-100 μm.

[0054] The length of the flow channel region 520 in the second direction from one end of the negative electrode 300 in the second direction is also the length to the edge of the first separation membrane 200 or the edge of the second separation membrane 400.

[0055] The flow path region 520 may be a single entity, but as shown in Figure 3, at the end of the negative electrode 300 in the second direction, the flow path region 520 is divided into a plurality of detail regions, each of which is spaced apart from each other in the first direction at a predetermined interval. The spacing may be constant or not. The lengths of each of the plurality of detail regions in the first direction may be the same or different from each other. That is, the flow path region 520 is divided into a plurality of detail regions, each of which is spaced apart from each other in the first direction at a predetermined interval, and each of the plurality of detail regions has one end connected to the negative electrode 300 in the second direction, and the other end in contact with the edge of the first separation membrane 200 or the second separation membrane 400. Therefore, the gas generated from the negative electrode 300 is discharged through the flow path region 520 to the outside of the region surrounded by the first separation membrane 200 and the second separation membrane 400.

[0056] When the unit cell of the present invention is used in the manufacture of jelly roll type electrodes, the length and separation distance between the bonding region 510 and the flow channel region 520 can be appropriately changed, taking into account the even greater curvature of the central part.

[0057] The method for manufacturing a unit cell of the present invention includes the steps of: preparing a positive electrode 100 (step S1); laminating a first separation membrane 200 onto one surface of the positive electrode 100 (step S2); laminating a negative electrode 300 onto the upper surface of the first separation membrane 200 (step S3); laminating a second separation membrane 400 onto the upper surface of the negative electrode 300 (step S4); and applying heat and pressure to bond the laminated positive electrode 100, negative electrode 300, first separation membrane 200, and second separation membrane 400, respectively, where the area of ​​the first separation membrane 200 and the second separation membrane 400 is larger than the area of ​​the positive electrode 100 and the negative electrode 300, respectively, and includes edge regions that do not come into contact with the negative electrode and the positive electrode, and joining the edge regions of the first separation membrane 200 and the second separation membrane 400 to each other (step S5).

[0058] In a desirable embodiment, in step S5, the edges of the first separation membrane 200 and the second separation membrane 400 are a joining target region 500, which is a region where the first separation membrane 200 and the second separation membrane 400 face each other but does not face the negative electrode 300. The joining target region 500 includes a joining region 510 where the first separation membrane 200 and the second separation membrane 400 are joined and an unjoined region where they are not joined. The unjoined region also forms a flow path region 520 that discharges gas generated at the negative electrode 300 or allows electrolyte to flow into the negative electrode 300.

[0059] Specifically, in step S5, the thermal blocking means is in contact with the flow path region 520, and the heating means is in contact with the joining region 510.

[0060] The thermal insulation means may be a block of insulating material or a cooling jig equipped with a heat dissipation means that can quickly release heat to the outside. When the positive electrode, first separator membrane, negative electrode, and second separator membrane are laminated under heat and pressure, such thermal insulation means can be used to secure the flow path area.

[0061] The heating means may also be a heating jig equipped with an IR heater or the like. To bond the first separation membrane and the positive electrode, or the first separation membrane and the second separation membrane, to each other solely by heat and pressure without adhesive, it is desirable to apply a predetermined pressure. The heating temperature of the heating jig should preferably be adjustable between 60 and 200°C.

[0062] Although embodiments of the present invention have been described above, these are merely illustrative, and those skilled in the art will understand that a wide range of variations and equivalent embodiments are possible. Therefore, the true scope of technical protection of the present invention must be determined by the claims. [Explanation of symbols]

[0063] 100: Positive electrode 110: First positive electrode composite layer 120: Second positive electrode composite layer 130: Positive electrode current collector 200: 1st separation membrane 300: Negative electrode 310: First negative electrode composite layer 320: Second negative electrode composite layer 330: Negative electrode current collector 400:Second separation membrane 500: Area to be joined 510:Joining area 520: Flow channel area

Claims

1. Positive electrode and, A first separation membrane is laminated on one surface of the positive electrode, A negative electrode is laminated on the upper surface of the first separation membrane, The negative electrode includes a second separation membrane laminated on the upper surface of the negative electrode, The area of ​​the first separation membrane and the second separation membrane is larger than the area of ​​the negative electrode and the positive electrode, and includes an edge region that does not come into contact with the negative electrode and the positive electrode. The first separation membrane and the second separation membrane are joined together at their respective edge regions. Of the regions where the first separation membrane and the second separation membrane face each other, the region that does not face the negative electrode is the bonding target region, and the bonding target region includes a bonding region where the first separation membrane and the second separation membrane are bonded to each other and a non-bonding region where they are not bonded to each other. The non-jointed region forms a flow path region that discharges gas generated in the unit cell from the unit cell and / or allows electrolyte to flow into the unit cell. The joining target region extends in a first direction and in a second direction perpendicular to the first direction, and the joining target region extending in the second direction does not have the flow path region. A unit cell in which a lead tab for electrically connecting to the outside is connected to the negative electrode side extending in the second direction.

2. The positive electrode includes a positive electrode binder. The negative electrode includes a negative electrode binder. The positive electrode binder comprises a polyvinylidene fluoride (PVdF) system. The negative electrode binder comprises one or more of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC). The unit cell according to claim 1, wherein the material of the first separation membrane and the second separation membrane includes one or more of polyethylene (PE) and polypropylene (PP).

3. The aforementioned positive electrode is, A first positive electrode composite layer comprising a positive electrode active material, a conductive material, and the positive electrode binder, A positive electrode current collector is laminated on the upper surface of the first positive electrode composite layer, The positive electrode current collector is laminated on the upper surface of the positive electrode current collector and includes a second positive electrode composite layer containing the positive electrode active material, a conductive material, and the positive electrode binder, The unit cell according to claim 2, wherein the second cathode composite layer is bonded to the first separator membrane by the cathode binder.

4. The unit cell according to claim 1, wherein the area of ​​the joining region has an area ratio of 0.5 to 0.9 compared to the area of ​​the region to be joined.

5. The unit cell according to claim 4, wherein the non-joined region has an area ratio of 0.1 to 0.5 compared to the area of ​​the region to be joined.

6. The unit cell according to claim 5, wherein the negative electrode, the first separation membrane, and the second separation membrane are rectangular in shape.

7. The negative electrode, the first separation membrane, and the second separation membrane have a length in the first direction that is even longer than the length in the second direction. The bonding target region is formed on both sides of the negative electrode with respect to the second direction, The unit cell according to claim 6, wherein the length from one end of the negative electrode to the joining target region in the second direction is 1 to 70% of the length of the negative electrode in the second direction.

8. The unit cell according to claim 6, wherein the length of the flow channel region in the second direction is from one end of the negative electrode in the second direction to the edge of the first separation membrane or the edge of the second separation membrane.

9. The aforementioned flow path region is divided into a plurality of detailed regions, The unit cell according to claim 8, wherein each of the plurality of detail regions is separated from each other at a predetermined interval in the first direction.

10. The stage of preparing the positive electrode (step S1), Step S2: Laminating a first separation film onto one surface of the positive electrode, Step S3 is the step of stacking a negative electrode on the upper surface of the first separation membrane, Step S4 involves laminating a second separation membrane onto the upper surface of the negative electrode, The stacked positive electrode, negative electrode, first separator membrane, and second separator membrane are joined by applying heat and pressure, but the area of ​​the first separator membrane and the second separator membrane is larger than the area of ​​the negative electrode and the positive electrode, and includes an edge region that does not come into contact with the negative electrode and the positive electrode, and the edge regions of the first separator membrane and the second separator membrane are joined together (step S5), Includes, In step S5, the edges of the first separation membrane and the second separation membrane are the bonding target regions, which are the regions where the first separation membrane and the second separation membrane face each other but do not face the negative electrode. The bonding target region includes a bonding region where the first separation membrane and the second separation membrane are bonded and a non-bonding region where they are not bonded. The non-jointed region forms a flow channel region that discharges gas generated in the unit cell and / or allows electrolyte to flow into the unit cell. The joining target region extends in a first direction and in a second direction perpendicular to the first direction, and the joining target region extending in the second direction does not have the flow path region. A method for manufacturing a unit cell, wherein a lead tab for electrically connecting to the outside is connected to the side of the negative electrode extending in the second direction.

11. In step S5, The method for manufacturing a unit cell according to claim 10, wherein a thermal barrier means is in contact with the flow channel region.

12. In step S5, The method for manufacturing a unit cell according to claim 10, wherein a heating means is brought into contact with the bonding region.

13. A secondary battery comprising the unit cell described in claim 1.

Images