Pouch-type secondary battery and method for manufacturing same

Abstract

The present invention relates to a pouch-type secondary battery comprising: an electrode assembly in which a plurality of electrodes and a plurality of separators are alternately stacked, and which includes a first electrolyte sheet; an electrolyte band surrounding the outer surface of the electrode assembly so that the stacked structure is fixed; and a battery case accommodating the electrode assembly, wherein the first electrolyte sheet is arranged on the surface of at least one of the plurality of electrodes, and each of the first electrolyte sheet and the electrolyte band includes a first polymer electrolyte.

Description

Pouch-type secondary battery and its manufacturing method Cross-citation with related applications This application claims the benefit of priority to Korean Patent Application No. 10-2023-0176097, filed December 6, 2023, and Korean Patent Application No. 10-2024-0179009, filed December 4, 2024, the entire contents of which are incorporated herein by reference. Technical field The present invention relates to a pouch-type secondary battery, and more specifically, to a pouch-type secondary battery with improved stability and electrolyte impregnation. With the advancement of technology in electric vehicles and portable devices, the demand for secondary batteries as an energy source is rapidly increasing. In particular, as the scope of application of secondary batteries expands to electric vehicles (EVs) and hybrid electric vehicles (HEVs), the demand for secondary batteries with stable output and excellent performance is increasing. In general, a secondary battery includes electrodes, a separator, and an electrolyte, and the performance of the secondary battery can be determined according to the types of the electrodes, the separator, and the electrolyte. A secondary battery can be completed through a wetting process of injecting an electrolyte into a battery case accommodating an electrode assembly to impregnate the electrode assembly with the electrolyte, and a packaging process of sealing the battery case. At this time, it is important to sufficiently increase the electrolyte impregnation property of the electrode assembly. If the electrode assembly of the secondary battery is not sufficiently impregnated with the electrolyte, the capacity of the secondary battery may decrease, and electrode deterioration may be accelerated, which may shorten the lifespan of the secondary battery. In order to improve the electrolyte impregnation property of the electrode assembly, methods using a vacuum and methods using pressurization are being used, but there is a problem that bubbles are also injected. In addition, if a swelling phenomenon occurs in the secondary battery due to the bubbles and the gas generated during charging and discharging of the secondary battery, there is a concern that the performance may deteriorate or a fire or explosion may occur due to external impact. In particular, secondary batteries with low physical durability, such as pouch-type secondary batteries, are vulnerable to internal gas generation and external impact, and therefore a technology is needed that can improve the electrolyte impregnation property of the electrode assembly without generating bubbles. In order to solve the above-described problems, the first technical problem to be solved by the present invention is to provide a pouch-type secondary battery in which the stability and electrolyte impregnation property of the electrode assembly are improved by applying a polymer electrolyte that can melt above a certain temperature to the surface of the electrode or the outer surface of the electrode assembly. The second technical problem to be solved by the present invention is to provide a method for manufacturing a pouch-type secondary battery in which the electrolyte impregnation property and processability of an electrode assembly are improved by applying a polymer electrolyte that can melt above a certain temperature to the surface of an electrode or the outer surface of an electrode assembly. [1] The present invention provides a pouch-type secondary battery including an electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately laminated and including a first electrolyte sheet; an electrolyte band wrapping an outer surface of the electrode assembly so as to fix the laminated structure; and a battery case accommodating the electrode assembly, wherein the electrolyte sheet is disposed on a surface of at least one of the plurality of electrodes, and the first electrolyte sheet and the electrolyte band each include a first polymer electrolyte. [2] The present invention provides a pouch-type secondary battery in which the melting point of the first polymer electrolyte in the above [1] is 60°C to 73°C. [3] The present invention provides a pouch-type secondary battery according to [1] or [2], wherein the first polymer electrolyte includes polyethylene oxide (PEO). [4] The present invention is a method for producing a polymer electrolyte comprising: at least one of the above [1] to [3], wherein the first polymer electrolyte comprises lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and aluminum oxide (Al 2 O 3 ) further comprises at least one selected from the group consisting of: [5] The present invention provides a pouch-type secondary battery, wherein in at least one of the above [1] to [4], the electrode assembly further includes a second electrolyte sheet, and the second electrolyte sheet includes a second polymer electrolyte. [6] The present invention provides a pouch-type secondary battery in which the melting point of the second polymer electrolyte in the above [5] is 35°C to 55°C. [7] The present invention provides a pouch-type secondary battery, wherein, in the above [5], the second polymer electrolyte comprises a main component including succinonitrile (SN); and a secondary component including at least one selected from the group consisting of polycarboxylate ether (PCE), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polyethylene carbonate (PEC), and polyacrylonitrile (PAN). [8] The present invention provides a pouch-type secondary battery, wherein in at least one of the above [1] to [7], there are two or more electrolyte bands, and each of the two or more electrolyte bands is arranged at a set interval. [9] The present invention provides a pouch-type secondary battery, wherein, in at least one of the above [1] to [8], each of the plurality of electrodes includes an electrode current collector and an electrode active material layer applied on the electrode current collector, and the first electrolyte sheet is positioned on the electrode active material layer.

[0010] The present invention provides a method for manufacturing a pouch-type secondary battery, comprising: a step of manufacturing an electrode assembly by alternately stacking a plurality of electrodes and a plurality of separators, and stacking a first electrolyte sheet on at least one of the plurality of electrodes; a step of fixing the electrode assembly with an electrolyte band; and a step of introducing and sealing the electrode assembly fixed with the electrolyte band and an electrolyte into a battery case to obtain an inactive pouch-type secondary battery; wherein each of the first electrolyte sheet and the electrolyte band includes a first polymer electrolyte.

[0011] The present invention provides a method for manufacturing a pouch-type secondary battery in which the melting point of the first polymer electrolyte in the above

[0010] is 60°C to 73°C.

[0012] The present invention provides a method for manufacturing a pouch-type secondary battery, wherein, in the above

[0010] or

[0011] , the step of manufacturing the electrode assembly includes the step of laminating a second electrolyte sheet on at least one of the plurality of electrodes, and the second electrolyte sheet includes a second polymer electrolyte.

[0013] The present invention provides a method for manufacturing a pouch-type secondary battery in which the melting point of the second polymer electrolyte in the above

[0012] is 35°C to 55°C.

[0014] The present invention provides a method for manufacturing a pouch-type secondary battery, wherein, in the above

[0012] or

[0013] , the step of activating the inactive pouch-type secondary battery is further included, and the step of activating the inactive pouch-type secondary battery is to perform charging and discharging of the pouch-type secondary battery at 45°C to 59°C.

[0015] The present invention provides a method for manufacturing a pouch-type secondary battery in which the second electrolyte sheet melts during the activation in the above

[0014] . The pouch-type secondary battery and the manufacturing method thereof according to the present invention aim to provide a secondary battery having improved electrolyte impregnation properties and replenishing electrolyte reduced during the charge / discharge process of the pouch-type secondary battery by using an electrolyte sheet and an electrolyte band including a polymer electrolyte that can melt at a certain temperature or higher. The effects obtainable from the exemplary embodiments of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly derived and understood by those skilled in the art to which the exemplary embodiments of the present disclosure belong from the following description. That is, unintended effects resulting from practicing the exemplary embodiments of the present disclosure can also be derived by those skilled in the art from the exemplary embodiments of the present disclosure. Figure 1 is a perspective view showing a pouch-type secondary battery according to the present invention. FIG. 2 is a drawing for explaining an electrode assembly of a pouch-type secondary battery according to the present invention. The terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as having meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to explain his or her own invention in the best manner. In this specification, the terms “electrolyte sheet” and “electrolyte band” mean materials that can function as an electrolyte of a secondary battery, such as a polymer electrolyte, as their constituents, and that maintain a solid state at room temperature, thereby having a sheet-like shape and a band-like shape, respectively. In this specification, the “polymer electrolyte” may mean a material that maintains a solid state at room temperature, can be formed into a shape such as a sheet or band, and changes into an amorphous state by transitioning into a liquid or gel at a melting temperature (Tm) or higher, and the polymer electrolyte may also be referred to as a solid polymer electrolyte (SPE) or a solid electrolyte. It should be understood that the terms “comprise,” “include,” or “have,” as used herein, are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. Each of the phrases "A or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", and "at least one of A, B, or C" can include any one of the items listed in that phrase, or all possible combinations of them. Terms such as "first" or "second" may be used merely to distinguish one component from another, and do not qualify the components in any other respect (e.g., importance or order). Hereinafter, the present invention will be described in detail. A pouch-type secondary battery according to the present invention comprises at least one of the configurations disclosed below, and may comprise any combination between technically possible configurations among the configurations below. A pouch-type secondary battery according to the present invention has a structure in which a plurality of electrodes and a plurality of separators are alternately laminated, and includes an electrode assembly including a first electrolyte sheet; an electrolyte band wrapping an outer surface of the electrode assembly so as to fix the laminated structure of the electrode assembly; and a battery case accommodating the electrode assembly; wherein the electrolyte sheet is arranged on a surface of at least one of the plurality of electrodes, and each of the first electrolyte sheet and the electrolyte band includes a first solid polymer electrolyte (SPE). The pouch-type secondary battery according to the present invention aims to improve the performance of the secondary battery by applying a polymer electrolyte that can melt above a certain temperature as having a shape such as an electrolyte sheet or an electrolyte band included in an electrode assembly. Specifically, by applying a first polymer electrolyte that can exist in a solid state even after an activation process but can melt during the operation of the secondary battery to the first electrolyte sheet and the electrolyte band, the electrolyte that decreases during charging and discharging of the secondary battery can be replenished, thereby realizing a secondary battery with stable output performance. In addition, the electrode assembly of the pouch-type secondary battery according to the present invention may further include a second electrolyte sheet, and the second electrolyte sheet may include a second polymer electrolyte. The second electrolyte sheet including the second polymer electrolyte may be melted during the activation process, thereby realizing an electrode assembly having excellent electrolyte impregnation properties. In this way, when the electrolyte band and electrolyte sheet are utilized as a means for replenishing or impregnating the electrolyte during the activation process or between charge and discharge of the secondary battery, since the means for replenishing or impregnating the electrolyte exist both inside and outside the electrode assembly, the electrolyte can be impregnated and supplied uniformly throughout, and stable performance can be expected. Hereinafter, the present invention will be described in detail with reference to the drawings. <Pouch-type secondary battery> Figure 1 is a perspective view showing a pouch-type secondary battery (100) according to the present invention. Referring to FIG. 1, a pouch-type secondary battery (100) according to the present invention includes an electrode assembly (200) and a battery case (400). The structure of the electrode assembly (200) is not particularly limited, and may include, for example, a jelly-roll type, a stack type, or a stack / folding type structure. The battery case (400) may be a pouch-shaped container made of a metal material and may include, for example, aluminum or an aluminum alloy. The battery case (400) may be sealed while housing the electrode assembly (200) so that a portion of the electrode lead (211), i.e., the terminal portion, is exposed. A pouch-type secondary battery (100) includes an electrolyte band (300) that wraps around an outer surface of an electrode assembly (200). The number of electrolyte bands (300) may be two or more, and each of the two or more electrolyte bands (300) may be arranged at a predetermined interval. The electrolyte band (300) may fix a laminated structure of the electrode assembly (200). Specifically, the electrolyte band (300) may wrap around an outer surface of the electrode assembly (200) so that the laminated structure can be maintained even before the electrode assembly (200) is accommodated in a battery case (400). That is, the electrolyte band (300) may play a role of stably maintaining the laminated structure of the electrode assembly (200) until the electrode assembly (200) is accommodated in the battery case (400) and the battery case (400) is sealed. Due to this, the assembly and structural stability of the pouch-type secondary battery (100) can be improved. In addition, the electrolyte band (300) includes a first solid polymer electrolyte (SPE). The first polymer electrolyte is an electrolyte that can melt at a certain temperature or higher, and the first polymer electrolyte can melt during operation of the secondary battery. For example, when the pouch-type secondary battery is manufactured, it exists in a band shape, but can melt when the internal temperature reaches a certain temperature or higher during operation of the secondary battery. Through this, the electrolyte reduced by charging and discharging the secondary battery can be replenished, and the output performance of the secondary battery can be stably maintained. According to another embodiment of the present invention, a battery module including a pouch-type secondary battery (100) as a unit cell and a battery pack including the same can be provided. Since the battery module and the battery pack include the secondary battery having high capacity, high rate characteristics and cycle characteristics, they can be used as a power source for medium and large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems. Electrode assembly Figure 2 is a drawing for explaining an electrode assembly (200) according to the present invention. Referring to FIG. 2, an electrode assembly (200) according to the present invention has a structure in which a plurality of electrodes (210) and a plurality of separators (220) are alternately laminated, and the electrode assembly includes a first electrolyte sheet. In addition, the electrode assembly may include at least one electrolyte sheet (230) selected from a group consisting of a first electrolyte sheet (230_1) and a second electrolyte sheet (230_2). Additionally, the electrolyte sheet (230) is disposed on the surface of at least one of the electrodes (210). That is, each of the first electrolyte sheet (230_1) and the second electrolyte sheet (230_2) is disposed on the surface of at least one of the electrodes (210). Meanwhile, the stacking order of the first electrolyte sheet (230_1) and the second electrolyte sheet (230_2) stacked in the electrode assembly (200) is not particularly limited. In exemplary embodiments, the electrode assembly (200) may have a structure in which the separator (220), the first electrolyte sheet (230_1), the electrode (210), the second electrolyte sheet (230_2), and the separator (220) are stacked in that order. In exemplary embodiments, the electrode assembly (200) may have a structure in which the separator (220), the first electrolyte sheet (230_1), the electrode (210), and the separator (220) are stacked in that order. In exemplary embodiments, the electrode assembly (200) may have a structure in which the separator, the electrode (210), the second electrolyte sheet (230_1), and the separator (220) are stacked in that order. The first electrolyte sheet (230_1) and the second electrolyte sheet (230_2) may include a polymer electrolyte that can melt at a certain temperature or higher. Specifically, the first electrolyte sheet (230_1) may include a first polymer electrolyte, and the second electrolyte sheet (230_2) may include a second polymer electrolyte. By applying the first polymer electrolyte and the second polymer electrolyte having different melting points to the electrode assembly (200), the timing at which the first electrolyte sheet (230_1) and the second electrolyte sheet (230_2) impregnate the electrode assembly (200) can be adjusted differently. Electrolyte sheet Referring to FIG. 2, an electrolyte sheet (230) may be positioned between an electrode (210) and a separator (220). Specifically, each of the plurality of electrodes (210) may include an electrode collector (not shown) and an electrode active material layer (not shown) applied on the electrode current collector, and the electrolyte sheet (230) may be positioned on the electrode active material layer. The shape of the electrolyte sheet (230) is not limited as long as it has a structure that can be laminated together with a plurality of electrodes (210) and a plurality of separators (220). For example, the electrolyte sheet (230) may be rectangular, circular, oval, or square. The electrolyte sheet (230) is divided into a first electrolyte sheet (230_1) or a second electrolyte sheet (230_2) having different melting points. (1) First electrolyte sheet The first electrolyte sheet (230_1) according to the present invention includes a first polymer electrolyte. The first polymer electrolyte may include polyethylene oxide (PEO), preferably polyethylene oxide (PEO); and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and aluminum oxide (Al 2 O 3) may include at least one selected from the group consisting of; If polyethylene oxide (PEO) having a melting point of about 75°C is used alone as the first polymer electrolyte, it may not melt at the normal operating temperature of the secondary battery. Therefore, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or aluminum oxide (Al) may be added to polyethylene oxide (PEO). 2 O 3 ) can be mixed, the first electrolyte sheet (230_1) including the first polymer electrolyte can be melted during operation of the secondary battery. As a result, the electrolyte can be supplemented to the electrode assembly (200), the electrolyte impregnation property can be improved, and a pouch-type secondary battery (100) having excellent performance can be implemented. Specifically, the first polymer electrolyte may include the polyethylene oxide (PEO) and the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in a weight ratio of 40:1 to 80:1, and preferably 40:1 to 60:1. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) can change the structure of the polyethylene oxide (PEO) from crystalline to amorphous, thereby lowering the melting point of the first polymer electrolyte. When the weight ratio of the polyethylene oxide (PEO) and the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) satisfies the above range, the first electrolyte sheet can melt during the operation of the pouch-type secondary battery (100) without melting during the manufacturing process of the pouch-type secondary battery (100). In addition, the melting point of the first polymer electrolyte may be 60° C. to 73° C., preferably 60° C. to 70° C., and more preferably 60° C. to 66° C. If the melting point of the first polymer electrolyte is lower than 60° C., it completely melts during the manufacturing process of the pouch-type secondary battery (100), and the sheet form cannot be maintained after the pouch-type secondary battery (100) is completed. On the other hand, if the melting point of the first polymer electrolyte is higher than 73° C., the first electrolyte sheet (230_1) does not melt in the normal operating temperature range of the pouch-type secondary battery (100), and thus cannot perform the role of replenishing the electrolyte. Accordingly, preferably, the melting point of the first polymer electrolyte may be 60°C or higher, 61°C or higher, or 62°C or higher, and the melting point of the first polymer electrolyte may be 73°C or lower, 71°C or lower, 70°C or lower, 68°C or lower, or 66°C or lower. The first electrolyte sheet (230_1) may partially melt during the activation process of the pouch-type secondary battery (100) by including the first polymer electrolyte, and the remainder may melt during operation. That is, the first electrolyte sheet (230_1) may be positioned between the electrode (210) and the separator (220) when the manufacture of the pouch-type secondary battery (100) is completed. (2) Second electrolyte sheet The second electrolyte sheet (230_2) according to the present invention includes a second polymer electrolyte. The second polymer electrolyte may include a main component including succinonitrile (SN); and a secondary component including at least one selected from the group consisting of polycarboxylate ether (PCE), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polyethylene carbonate (PEC), and polyacrylonitrile (PAN). In exemplary embodiments, the second polymer electrolyte may include, as the auxiliary component, a combination of polycarboxylate (PCE) and polyethylene oxide (PEO), a combination of polycarboxylate (PCE) and polyvinylpyrrolidone (PVP), a combination of polycarboxylate (PCE) and polyethylene carbonate (PEC), or a combination of polycarboxylate (PCE) and polyacrylonitrile (PAN). In exemplary embodiments, the molecular weight of the polycarboxylate (PCE) may be about 165 g / mol, the molecular weight of the polyethylene oxide (PEO) may be about 100 g / mol, and the molecular weight of the polyvinylpyrrolidine (PVP) may be about 25 g / mol. The second polymer electrolyte may have a melting point of 35°C to 55°C, preferably 35°C to 52°C, and more preferably 42°C to 52°C. The second polymer electrolyte may melt during the manufacturing process of the pouch-type secondary battery (100), and after the second polymer electrolyte melts during the process, it may be impregnated into the electrode and separator, etc., within the electrode assembly and may not return to its original state even if the temperature is lowered again, thereby improving the electrolyte impregnation property of the pouch-type secondary battery (100) during the manufacturing process. Accordingly, the melting point of the second polymer electrolyte may be preferably 35°C or higher, 37°C or higher, 40°C or higher, or 42°C or higher, and the melting point of the second polymer electrolyte may be 55°C or lower, 53°C or lower, 52°C or lower, 50°C or lower, or 48°C or lower. That is, the second electrolyte sheet (230_2) can be melted during the activation process of the pouch-type secondary battery (100) by including the second polymer electrolyte, thereby enabling the implementation of a pouch-type secondary battery (100) with improved electrolyte impregnation properties. Electrolyte Band The electrolyte band (300) according to the present invention can wrap around the outer surface of the electrode assembly (200) so that the laminated structure of the electrode assembly (200) is fixed. The shape of the electrolyte band (300) is not limited as long as it can fix the electrode assembly (200). Meanwhile, the electrolyte band (300) may include the first polymer electrolyte. The content regarding the first polymer electrolyte overlaps with the content described above in the first electrolyte sheet (230_1), so it is omitted. The electrolyte band (300) may partially melt during the activation process of the pouch-type secondary battery (100), and the remainder may melt during the operation of the pouch-type secondary battery (100). The electrolyte band (300) stably fixes the structure of the electrode assembly (200) before the electrode assembly (200) is accommodated in the battery case (400), and provides electrolyte to the electrode assembly (200) after the electrode assembly (200) is accommodated in the battery case (400). As a result, a pouch-type secondary battery (100) with improved processability and electrolyte impregnation can be implemented. electrode Each of the electrodes (210) according to the present invention may include an electrode current collector (not shown) and an electrode active material layer (not shown) applied on the electrode current collector. The electrodes (210) may be classified as positive or negative electrodes. (1) Bipolar The above positive electrode may have a structure in which a positive electrode active material layer is formed on a positive electrode current collector. The positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The above-mentioned positive electrode active material layer includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder. The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ) or a layered compound substituted with one or more transition metals; LiFe 3 O 4 Lithium iron oxide; chemical formula Li 1+a1 Mn 2-a1 O 4 (0≤a1≤0.33), LiMnO 3 , LiMn2 O 3 , LiMnO 2 Lithium manganese oxide, etc.; lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , V 2 O 5 , Cu 2 V 2 O 7 Vanadium oxide, chemical formula LiNi 1 -a 2 Mc 2 O 2 (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≤a2≤0.3) Ni-site type lithium nickel oxide; chemical formula LiMn 2-a3 M c3 O 2 (wherein, M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≤a3≤0.1) or Li 2 Mn 3 MO 8 (wherein, M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); LiMn, a lithium manganese composite oxide expressed by the chemical formula, wherein a portion of Li is replaced by an alkaline earth metal ion. 2 O 4　 These may include, but are not limited to, the anode. The anode may be Li-metal. The above-mentioned positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without special restrictions. Specific examples include 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, and carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. Next, the positive electrode binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof may be used. The above positive electrode can be manufactured according to a conventional electrode manufacturing method. For example, a positive electrode slurry can be manufactured by mixing a positive electrode active material, a positive electrode binder, and / or a positive electrode conductive material in a positive electrode slurry solvent, and the positive electrode slurry can be applied onto a positive electrode current collector, followed by drying and rolling to manufacture a positive electrode current collector having a positive electrode active material layer (222) formed thereon. Meanwhile, solvents commonly used in the relevant technical field can be used as the positive electrode slurry solvent, and for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc. can be used alone or as a mixture of two or more. (2) Cathode The above negative electrode may have a structure in which a negative electrode active material layer is formed on a negative electrode current collector. The negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. The above-described negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. As the negative electrode active material, compounds capable of reversible intercalation and deintercalation of lithium, which are generally used in the relevant technical field, can be used, and the type thereof is not particularly limited. Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Si, Si-Me alloy (wherein Me is at least one selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (wherein, 0 <y<2), Si-C 복합체 등과 같은 실리콘계 물질; 리튬 금속 박막; Sn, Al 등과 같이 리튬과 합금화가 가능한 금속 물질; 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다. The above negative electrode conductive material is used to provide conductivity to the negative electrode, and can be used without special restrictions in the battery being composed, as long as it does not cause a chemical change and has electronic conductivity. The negative electrode conductive material may be the same as the positive electrode conductive material. The above negative electrode binder serves to improve the adhesion between negative electrode active material particles and the adhesive strength between the negative electrode active material and the negative electrode current collector. The above negative electrode binder may be the same as the above positive electrode binder. Meanwhile, the negative electrode can be manufactured according to a conventional electrode manufacturing method. For example, a negative electrode slurry can be manufactured by mixing a negative electrode active material, a negative electrode binder, and / or a negative electrode conductive material in a negative electrode slurry solvent, and the negative electrode slurry can be applied onto a negative electrode current collector, followed by drying and rolling to manufacture a negative electrode current collector having a negative electrode active material layer (212) formed thereon. As the above-mentioned cathode slurry solvent, solvents commonly used in the relevant technical field can be used, and for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc. can be used alone or in a mixture of two or more. Membrane The separator (220) according to the present invention is positioned between the electrodes and can provide a passage for lithium ions to move. Any separator that is commonly used in secondary batteries can be used without special restrictions. Specifically, the separator may be 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. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength. Electrolyte The pouch-type secondary battery (100) according to the present invention further includes a liquid electrolyte (not shown) that is poured inside the battery case (400). The liquid electrolyte is for moving lithium ions generated by an electrochemical reaction of an electrode during charging / discharging of the secondary battery, and may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent. As the organic solvent, any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move may be used without particular limitation. Specifically, the organic solvent may include: ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); Alcohol solvents such as ethyl alcohol, isopropyl alcohol, etc. can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferable. The above lithium salt can be used without any special limitation as long as it is a compound capable of providing lithium ions used in a secondary battery. Specifically, the above lithium salt is LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAl0 4 , LiAlCl4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN(C 2 F 5 SO 3 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 , LiCl, LiI, or LiB(C 2 O 4 ) 2 The above lithium salt concentration is preferably used within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance, and lithium ions can move effectively. <Method for manufacturing pouch-type secondary battery> A method for manufacturing a pouch-type secondary battery (100) according to the present invention includes the steps of: alternately stacking a plurality of electrodes (210) and a plurality of separators (220), and stacking a first electrolyte sheet (230_1) on at least one of the plurality of electrodes (210) to manufacture an electrode assembly (200); fixing the electrode assembly (200) with an electrolyte band (300); and introducing and sealing the electrode assembly (200) fixed with the electrolyte band (300) and a liquid electrolyte (not shown) into a battery case (400) to obtain an inactive pouch-type secondary battery. At this time, the first electrolyte sheet (230_1) includes a first polymer electrolyte. Steps for manufacturing electrode assemblies Meanwhile, the step of manufacturing the electrode assembly (200) may be a step of alternately stacking the electrode (210) and the separator (220), and when stacking the electrode (210) and the separator (220), a first electrolyte sheet (230_1) may be stacked therebetween. The step of manufacturing the electrode assembly (200) according to the present invention may include the step of laminating a second electrolyte sheet (230_2) on at least one electrode among the plurality of electrodes, and the second electrolyte sheet (230_2) may include a second polymer electrolyte. For example, when laminating the electrode (210) and the separator (220), the first electrolyte sheet (230_1) and / or the second electrolyte sheet (230_2) may be laminated. Each of the first electrolyte sheet (230_1) and the electrolyte band (300) includes a first polymer electrolyte, and the second electrolyte sheet (230_2) includes a second polymer electrolyte. Specifically, the first electrolyte sheet and the second electrolyte sheet can be arranged between the electrode and the separator in an appropriate number as needed, and since the first electrolyte sheet can be converted into a liquid phase during the charge / discharge period of the secondary battery, and the second electrolyte sheet can be converted into a liquid phase during the activation period of the secondary battery, the position and number of the first electrolyte sheet and the second electrolyte sheet can be adjusted according to the types of the constituent electrodes and the types of the electrolyte. Since the first polymer electrolyte and the second polymer electrolyte are the same as described above, a detailed description is omitted. In exemplary embodiments, the step of manufacturing the electrode assembly (200) may include the step of manufacturing each of the first electrolyte sheet (230_1) and the second electrolyte sheet (230_2), and if the components include the first polymer electrolyte and the second polymer electrolyte, respectively, the molding method may apply a conventional method to manufacture the electrolyte sheet (230). Step of fixing the above electrode assembly with an electrolyte band The method for manufacturing a pouch-type secondary battery (100) according to the present invention includes a step of fixing an electrode assembly (200) with an electrolyte band (300). Specifically, in order to stably maintain the laminated structure of the electrode assembly (200), the outer surface of the electrode assembly (200) can be wrapped with an electrolyte band (300). In exemplary embodiments, the step of securing the electrode assembly (200) with the electrolyte band (300) may include the step of arranging the electrolyte band (300) at both ends and the center of the electrode assembly (200), arranging it in a direction perpendicular to the direction in which the electrode leads protrude, and at least one, two, or three electrolyte bands may be arranged, and it may be preferable to arrange no more than six. Meanwhile, the electrolyte band includes a first polymer electrolyte, and as described above, includes the first polymer electrolyte as a component of the electrolyte band. A conventional method can be applied for the molding method. However, when molding in the form of a band, it is preferable to impart elasticity, so an additive capable of imparting elasticity can be added or a first polymer electrolyte having elasticity at room temperature can be selected. Steps for obtaining an inactive pouch-type secondary battery The method for manufacturing a pouch-type secondary battery (100) according to the present invention includes a step of: inserting an electrode assembly (200) fixed to a battery case (400) with an electrolyte band (300); and a liquid electrolyte into the electrode assembly and sealing it to obtain an inactive pouch-type secondary battery. Specifically, an electrode assembly (200) fixed with an electrolyte band (300) can be stored inside a battery case (400). Meanwhile, after the electrode assembly (200) is housed in the battery case (400), the liquid electrolyte can be injected into the inside of the battery case (400). The injected liquid electrolyte can penetrate into the pores of the electrode assembly (200). At this time, even without performing an additional process for impregnating the electrode assembly (200) with the liquid electrolyte, the impregnation property of the electrode assembly (200) with the electrolyte can be improved through the first electrolyte sheet (230_1), the second electrolyte sheet (230_2), and the electrolyte band (300). Steps for activating an inactive pouch-type secondary battery In exemplary embodiments, the method for manufacturing a pouch-type secondary battery (100) may further include a step of activating the inactive pouch-type secondary battery (100), and the activation step may be to perform charging and discharging of the pouch-type secondary battery (100) at 45° C. to 59° C. In exemplary embodiments, the temperature of the activation step may be 50° C. to 59° C. In addition, the activation step may include a step in which the second electrolyte sheet (230_2) melts within the battery case (400). That is, the melting point of the second polymer electrolyte included in the second electrolyte sheet (230_2) is lower than the process temperature of the activation step. Through this, an electrode assembly (200) having excellent electrolyte impregnation properties can be implemented. In exemplary embodiments, the activation step may be a process of repeatedly charging and discharging at a specific rate up to a specific voltage, and an aging process may be performed between the charging and discharging during this process, and such charging and discharging and aging may be applied without particular limitation as long as it is a method utilized in this technical field, but a process of increasing the temperature to the aforementioned temperature range during the charging, discharging, and aging during activation needs to be included. Through this, a process of impregnating the second polymer electrolyte into the electrode assembly can be performed. Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. Example 1: Manufacturing of secondary battery (1) Manufacturing of the first electrolyte sheet Lithium bis(trifluoromethanesulfonyl)imide (99.9% purity LiTFSI) stored in a dry room at 110°C for more than 24 hours and polyethylene oxide (PEO) stored at 45°C for 48 hours were prepared. Thereafter, polyethylene oxide:LiTFSI were mixed at a weight ratio of 50:1 and stirred for 12 hours to prepare a first polymer electrolyte. Thereafter, the first polymer electrolyte was cast into a glass container to produce a film form, and dried in a vacuum oven at 50°C for 24 hours to produce a first electrolyte sheet having a melting point of about 60°C. (2) Electrolyte band manufacturing An electrolyte band was manufactured in the same manner as the first electrolyte sheet, except that the first polymer electrolyte was manufactured in a band shape through an injection molding method. (3) Manufacturing of electrode assembly An electrode assembly was manufactured by stacking an electrode, a separator, and the first electrolyte sheet manufactured above, and inserting the first electrolyte sheet between the electrode and the separator. Thereafter, an electrode lead was joined to the electrode assembly. (4) Manufacturing of secondary batteries Three band-shaped polymer electrolytes were arranged at regular intervals on the outer surface of the electrode assembly manufactured above. Afterwards, the above electrode assembly is placed in a battery case, and ethylene carbonate (EC): ethyl methyl carbonate (EMC) is mixed in a volume ratio of 30:70, and then LiPF 6The liquid electrolyte dissolved to make 1.0 M was injected, and the battery case was sealed. After that, the electrode assembly was activated at 45°C to 59°C, and then further aged for 3 days. Finally, a degas process was performed to manufacture a pouch-type secondary battery. Example 2 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that the first polymer electrolyte was manufactured as follows. Lithium salt (LiTFSI) with polyethylene oxide (PEO) and aluminum oxide (Al 2 O 3 ) were mixed in a mass ratio of 9:1 and stirred for 12 hours to produce a first polymer electrolyte having a melting point of approximately 73°C. Example 3 A pouch-type secondary battery was manufactured in the same manner as described above, except that a second electrolyte sheet was manufactured, and an electrode, a separator, and the first electrolyte sheet and the second electrolyte sheet manufactured above were stacked to manufacture an electrode assembly by inserting the first electrolyte sheet on one side of the separator and the second electrolyte sheet on the other side. At this time, the second electrolyte sheet was manufactured by the following method. Specifically, polycarboxylate (PCE) and polyethylene oxide (PEO) dried in a dry room for 24 hours were prepared. Then, polycarboxylate (PCE) and polyethylene oxide (PEO), which were mixed in a mass ratio of 9:1 to a mixture of lithium bis(trifluoromethanesulfonyl)imide (99.9% purity LiTFSI) and succinonitrile (SN), were added so that the amount was 10 wt%, and then stirred at 70°C to manufacture a second polymer electrolyte. Thereafter, the second polymer electrolyte was cast into a glass container to produce a film, and dried in a vacuum oven at 35°C for 24 hours to produce a second electrolyte sheet having a melting point of 42°C. Example 4 A pouch-type secondary battery was manufactured in the same manner as in Example 3, except that the second polymer electrolyte was manufactured as follows. Polycarboxylate (PCE) and polyvinylpyrrolidine (PVP) were prepared by drying in a dry room for 24 hours. Then, polycarboxylate (PCE) and polyvinylpyrrolidine (PVP), which were mixed in a mass ratio of 9:1 to a mixture of lithium bis(trifluoromethanesulfonyl)imide (99.9% purity LiTFSI) and succinonitrile (SN), were added so that 10 wt% of the mixture was obtained, and then stirred at 70°C to produce a second polymer electrolyte having a melting point of approximately 52°C. Comparative Example 1 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that the first electrolyte sheet, the second electrolyte sheet, and the electrolyte band were not applied. Comparative Example 2 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that the first electrolyte sheet was positioned between the electrode collector and the electrode active material layer of the electrode, rather than between the electrode and the separator, and the electrolyte band was not applied. Experimental Example 1: Impregnation Evaluation Each of the pouch-type secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 2 was disassembled to evaluate the electrolyte impregnation property. Specifically, with 1C-rate charge / discharge as one cycle, each of the pouch-type secondary batteries after 100 cycles was disassembled, the battery case was opened, and the degree of electrode impregnation property was evaluated. In Table 1 below, the “○” mark means good, meaning that the electrolyte impregnation area is 80% or more compared to the entire surface of the electrode and separator. The “△” mark means normal, meaning that the electrolyte impregnation area is 50% to 0% compared to the entire surface of the electrode and separator. Experimental Example 2: Evaluation of detachability After disassembling the pouch-type secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 2, it was confirmed whether electrode detachment occurred, and the electrode detachment ability was relatively evaluated based on the number of surfaces where detachment occurred, which is shown in Table 1 below. Specifically, if electrode detachment did not occur, a "○" mark was indicated, and if the degree of electrode detachment was less than 50%, a "△" mark was indicated. Experimental Example 3: Evaluation of electrolyte reduction during use of pouch-type secondary batteries Each of the pouch-type secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 2 was subjected to 1C-rate charge / discharge as one cycle, and after 100 cycles, the pouch-type secondary batteries were disassembled and the battery cases were opened. The amount of electrolyte that escaped due to gas could be confirmed through comparison before and after charge / discharge. The performance for electrolyte reduction was evaluated through relative comparison of weight ratios, and is shown in Table 1 below. In Table 1 below, the “○” mark indicates that the remaining electrolyte result of the pouch-type secondary battery manufactured in Example 1 is 90% or more, and the “X” mark indicates that the remaining electrolyte result is less than 80% based on the result of Example 1. Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Impregnation Island Evaluation ○○○○△△ Desorption Evaluation ○○○○△△ Residual Electrolyte Evaluation ○○○○XX Referring to Table 1 above, it can be confirmed that the impregnation property of the electrode assemblies applied to Examples 1 to 4 for electrolyte is higher than the impregnation property of the electrode assemblies applied to Comparative Examples 1 and 2 for electrolyte. It is believed that this is because the first electrolyte sheet or second electrolyte sheet added in addition to the liquid electrolyte melts during the pouch-type secondary battery manufacturing process, thereby improving the impregnation property of the electrode assembly for electrolyte. In addition, it can be confirmed that the detachment property of the electrode active material layers of Examples 1 to 4 to the electrode current collector is better than that of Comparative Example 2. It is believed that this is because the second electrolyte sheet of Comparative Example 2 is positioned between the electrode active material layer and the electrode separator layer, thereby reducing the adhesive strength of the electrode active material layer. In addition, it can be confirmed that the amount of remaining electrolyte of the pouch-type secondary batteries manufactured in Examples 1 to 4 is better than the amount of remaining electrolyte of the pouch-type secondary batteries manufactured in Comparative Examples 1 and 2. It is believed that this is because not only the second electrolyte sheet but also a portion of the first electrolyte sheet and the electrolyte band melted to replenish the amount of electrolyte. [Explanation of symbols] 100: Pouch-type secondary battery 200: Electrode assembly 210: Electrode 211: Electrode Lead 220: Membrane 230: Electrolyte sheet 230_1: 1st electrolyte sheet 230_2: Second electrolyte sheet 300: Electrolyte Band 400: Battery Case

Claims

1. An electrode assembly having a structure in which a plurality of electrodes and a plurality of separators are alternately laminated and including a first electrolyte sheet; an electrolyte band wrapping an outer surface of the electrode assembly so as to fix the laminated structure; and a battery case accommodating the electrode assembly; The above electrolyte sheet is disposed on the surface of at least one of the plurality of electrodes, A pouch-type secondary battery, wherein each of the first electrolyte sheet and the electrolyte band contains a first polymer electrolyte.

2. In paragraph 1, A pouch-type secondary battery wherein the melting point of the first polymer electrolyte is 60°C to 73°C.

3. In paragraph 1, A pouch-type secondary battery wherein the first polymer electrolyte contains polyethylene oxide.

4. In paragraph 3, A pouch-type secondary battery, wherein the first polymer electrolyte further comprises at least one selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide and aluminum oxide.

5. In paragraph 1, The above electrode assembly further comprises a second electrolyte sheet, A pouch-type secondary battery wherein the second electrolyte sheet includes a second polymer electrolyte.

6. In paragraph 5, A pouch-type secondary battery wherein the melting point of the second polymer electrolyte is 35°C to 55°C.

7. In paragraph 5, The above second polymer electrolyte, A main ingredient comprising succinonitrile; and A pouch-type secondary battery comprising an auxiliary component including at least one selected from the group consisting of polycarboxylate, polyethylene oxide, polyvinyl pyrrolidine, polyethylene carbonate, and polyacrylonitrile.

8. In paragraph 1, A pouch-type secondary battery having two or more electrolyte bands, each of which is spaced apart from the other at a set interval.

9. In paragraph 1, Each of the above plurality of electrodes includes an electrode current collector and an electrode active material layer applied on the electrode current collector, A pouch-type secondary battery wherein the first electrolyte sheet is positioned on the electrode active material layer.

10. A step of manufacturing an electrode assembly by alternately stacking a plurality of electrodes and a plurality of separators, and stacking a first electrolyte sheet on at least one of the plurality of electrodes; A step of fixing the above electrode assembly with an electrolyte band; and A step of obtaining an inactive pouch-type secondary battery by introducing and sealing an electrode assembly and an electrolyte fixed to the electrolyte band into a battery case; A method for manufacturing a pouch-type secondary battery, wherein each of the first electrolyte sheet and the electrolyte band includes a first polymer electrolyte.

11. In paragraph 10, A method for manufacturing a pouch-type secondary battery wherein the melting point of the first polymer electrolyte is 60°C to 73°C.

12. In paragraph 10, The step of manufacturing the electrode assembly comprises the step of laminating a second electrolyte sheet on at least one of the plurality of electrodes, A method for manufacturing a pouch-type secondary battery, wherein the second electrolyte sheet includes a second polymer electrolyte.

13. In paragraph 12, A method for manufacturing a pouch-type secondary battery wherein the melting point of the second polymer electrolyte is 35°C to 55°C.

14. In paragraph 12, Further comprising a step of activating the above inactive pouch-type secondary battery, A method for manufacturing a pouch-type secondary battery, wherein the step of activating the above-mentioned inactive pouch-type secondary battery is to perform charging and discharging of the pouch-type secondary battery at a temperature of 45°C to 59°C.

15. In paragraph 14, A method for manufacturing a pouch-type secondary battery, wherein the second electrolyte sheet melts during the activation.

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