Bipolar battery and manufacturing method therefor

Abstract

According to an embodiment of the present invention, provided are a bipolar battery and a manufacturing method therefor, the bipolar battery comprising: a bipolar assembly including a laminate including a bipolar electrode and a separator, and a gel electrolyte impregnated in the entire laminate; and a battery case, wherein no interfacial gap is included in an interface between the bipolar electrode and the separator, and voids in the gel electrolyte are less than or equal to 5% of the total volume of the gel electrolyte that can be impregnated.

Description

Bipolar battery and method for manufacturing the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0092124, filed July 12, 2024, and Korean Patent Application No. 10-2025-0093154, filed July 10, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a bipolar battery and a method for manufacturing the same.

[0004] Recently, as the application areas of lithium secondary batteries have rapidly expanded to include not only power supply for electronic devices such as electric, electronic, communication, and computer devices, but also power storage for large-area devices such as automobiles and power storage devices, the demand for high-capacity, high-output, and high-stability secondary batteries is increasing.

[0005] The electrodes used in these secondary batteries can be divided into monopolar electrodes in which active materials having the same polarity are coated on both sides of the current collector, and bipolar electrodes in which active materials having different polarities are coated on both sides of the current collector.

[0006] Secondary batteries using monopolar electrodes have connections connecting the electrodes, which can result in reduced output due to the electrical resistance of the connections. Furthermore, the temperature rise caused by Joule heating can pose various safety issues for the cell. Furthermore, the heat dissipation structure, thermal monitoring, and battery components for wiring take up a significant amount of space in the battery pack, resulting in poor space efficiency. On the other hand, secondary batteries using bipolar electrodes stack electrodes without connections, minimizing electrode connection resistance and resulting in excellent output performance. Furthermore, their simplified structure and components offer significant space efficiency, enabling significant improvements in volumetric energy density and power density compared to conventional lithium-ion batteries.

[0007] Despite these advantages, it is very important to prevent leakage of the electrolyte impregnated in bipolar batteries, so a non-flowing all-solid-state electrolyte is used.

[0008] However, current technology has not been able to develop an all-solid-state electrolyte that can be used industrially, so it is still manufactured using liquid electrolyte or gel electrolyte.

[0009] Conventional methods for manufacturing bipolar batteries using the above-mentioned liquid electrolyte or gel electrolyte include direct injection method, electrode coating / impregnation method, and electrode slurry mixing method.

[0010] The above direct injection method is a method of manufacturing the bipolar as a unit cell unit and sealing it to prevent electrolyte leakage, that is, manufacturing it as a sealed structure and then injecting the electrolyte. However, the implementation of this sealed structure is not only complicated, but also, since this process is performed for each unit cell and then an assembly is manufactured, there are problems in that it is difficult in terms of process and takes a long time.

[0011] In addition, the electrode coating / impregnation method is performed by applying an electrolyte on an electrode sheet or a separator, impregnating the electrolyte, and then going through a curing process, and then cutting and laminating the electrode and the separator to manufacture the electrode, and the slurry mixing method is performed by going through a curing process, cutting and laminating to manufacture the electrode by mixing an electrode slurry and an electrolyte together.

[0012] However, in both of the above methods, since the electrode impregnated with the electrolyte or the electrode mixed with the electrolyte is directly exposed to the outside during the manufacturing process, not only does the electrolyte volatilization occur severely, but also the curability is very poor due to the presence of oxygen during the electrolyte curing process, which poses a safety issue.

[0013] In addition, when manufacturing a bipolar battery using a conventional manufacturing method, as illustrated in FIG. 1, the electrolyte (20) on the surface of the electrode (11) is depleted due to the volatilization of the electrolyte (20) generated on the surface of the electrode (11), and accordingly, when manufacturing a unit cell (10), a gel electrolyte volatilization space, i.e., a gel electrolyte interface gap (13) is generated between the interface of the electrode (11) and the separator (12), which acts as battery resistance, and there is a problem that the battery performance is also reduced.

[0014] Therefore, there is a need to develop a bipolar battery with a simplified structure while solving the above problems.

[0015] The present invention aims to provide a bipolar battery and a method for manufacturing the same, in which the gel electrolyte is cured after manufacturing the laminate, thereby having almost no voids in the gel electrolyte inside the laminate and thus improving battery performance.

[0016] The present invention also has the effect of simplifying the structure by applying a gel electrolyte without applying a separate sealed structure.

[0017] Furthermore, the present invention aims to provide a method for manufacturing a bipolar assembly that can uniformly impregnate components within the bipolar assembly with electrolyte and save electrolyte impregnation time.

[0018] The present invention further aims to provide a bipolar battery and a manufacturing method thereof that can be applied to various electrolytes without limitation to electrolyte materials by minimizing volatilization of a gel electrolyte during the manufacture of a bipolar battery.

[0019] According to one embodiment of the present invention,

[0020] A bipolar assembly comprising a laminate including a bipolar electrode and a separator, and a gel electrolyte impregnated throughout the laminate; and a battery case;

[0021] A bipolar battery is provided in which the gel electrolyte voids inside the laminate are 5% or less of the total volume that can be impregnated with the gel electrolyte.

[0022] At this time, the bipolar electrode may include an integrated electrode in which a positive electrode active material layer and a negative electrode active material layer are each coated on both sides of a single current collector, a positive electrode in which a positive electrode active material layer is formed on one side of a positive electrode current collector, or a negative electrode in which a negative electrode active material layer is formed on one side of a negative electrode current collector.

[0023] The above laminate may be a structure in which at least one selected from the group consisting of a unit cell having a structure in which the positive electrode active material layer of the integrated electrode and the separator face each other, a unit cell having a structure in which the positive electrode and the negative electrode are separately included and the separator is interposed between the positive electrode and the negative electrode, a unit cell having a structure in which a cross-sectional electrode and a separator are stacked, and a cross-sectional electrode.

[0024] Additionally, the laminate may have cross-sectional electrodes of different polarities positioned on the outermost sides on both sides in the lamination direction.

[0025] Such laminate may not include a sealing member.

[0026] Meanwhile, the gel electrolyte includes an electrolyte composition having a flash point of less than 90°C, and specifically, the electrolyte composition having a flash point of less than 90°C may be included in an amount of 10% or more based on the total volume of the electrolyte composition included in the gel electrolyte.

[0027] The electrolyte composition having a flash point of less than 90°C may be at least one selected from the group consisting of methyl formate, ethyl formate, 1,2-dimethoxyethane, methyl acetate, 1,3-dioxolane, ethyl acetate, methyl propionate, propyl acetate, methyl butyrate, tris(trimethylsilyl)phosphate, dimethyl carbonate, propyl propionate, ethylmethyl carbonate, diethyl carbonate, ethyl propionate, ethyl butyrate, butyronitrile, ethylmethylsulfone, propyl butyrate, diethylene glycol dimethyl ether, vinylene carbonate, and glycol sulfite.

[0028] Furthermore, according to the present invention, all of the bipolar electrodes and all of the separators included in the laminate may be entirely bonded by the gel electrolyte in a laminated state.

[0029] Furthermore, the outermost electrodes on both sides in the stacking direction of the bipolar assembly may each be attached with a positive terminal and a negative terminal.

[0030] Meanwhile, according to another embodiment of the present invention, as a method for manufacturing the bipolar battery,

[0031] (a) Prepare a unit cell by stacking bipolar electrodes and a separator,

[0032] (b) A laminate is manufactured by stacking two or more of the above unit cells and placing a cross-sectional electrode on the outermost surface,

[0033] (c) A method for manufacturing a bipolar battery is provided, which comprises storing the laminate in a storage member containing a gel electrolyte composition, impregnating the laminate, and curing the gel electrolyte composition under pressure to form a gel electrolyte.

[0034] At this time, the unit cell can be manufactured by cutting the bipolar electrode and the separator into unit sizes and then bonding them together.

[0035] Each of these above unit cells may have a structure that does not include a sealing member.

[0036] The above gel electrolyte composition may include an electrolyte composition having a flash point of less than 90°C in an amount of 10% or more based on the total solvent volume.

[0037] Meanwhile, when impregnating such a gel electrolyte composition, the storage member in which the laminate is stored may be, for example, an open-type electrolyte box with an open top, or a battery case that stores the laminate.

[0038] Therefore, if the storage member is an electrolyte box, the process may further include storing the laminate in a battery case after forming the gel electrolyte.

[0039] Meanwhile, impregnation of the gel electrolyte composition can be performed under vacuum.

[0040] The above vacuum authorization may be performed by repeating vacuum application and vacuum release four or more times.

[0041] The above vacuum application can be maintained for 3 to 10 minutes at a time in the range of -100 kPa to -90 kPa.

[0042] Thereafter, the curing performed with pressurization can be performed by applying heat in a vacuum state at a temperature ranging from 50°C to 80°C for 2 to 10 hours.

[0043] Furthermore, the method for manufacturing a bipolar battery according to the present invention may further include a process of releasing the pressurized state after curing of the gel electrolyte composition.

[0044] A bipolar battery is provided in which a positive terminal and a negative terminal are attached to the outermost electrodes on both sides in the stacking direction of the above bipolar assembly.

[0045] Figure 1 is a cross-sectional schematic diagram of a bipolar unit cell manufactured using a conventional manufacturing method.

[0046] Figure 2 is a cross-sectional schematic diagram of a bipolar assembly according to one embodiment of the present invention.

[0047] Figure 3 is a cross-sectional schematic diagram of a bipolar unit cell according to one embodiment of the present invention.

[0048] Figure 4 is a cross-sectional schematic diagram of a bipolar unit cell according to another embodiment of the present invention.

[0049] Figure 5 is a cross-sectional schematic diagram of a bipolar battery according to one embodiment of the present invention.

[0050] Figure 6 is a schematic diagram of a method for manufacturing a bipolar battery according to one embodiment of the present invention.

[0051] Figure 7 is a comparative graph showing the amount of electrolyte volatilization due to structural differences according to Experimental Example 1.

[0052] Figure 8 is a voltage-capacity graph according to the cycle of Comparative Example 1 according to Experimental Example 2.

[0053] Figure 9 is a voltage-capacity graph according to the cycle of an embodiment according to Experimental Example 2.

[0054] Hereinafter, the terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, and should be interpreted as 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 to explain his or her own invention in the best way.

[0055] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0056] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0057] In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0058] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described below. In addition, like reference numerals throughout this specification and drawings represent like elements.

[0059] In addition, the drawings of the present invention include parts that are indicated by a hatched structure and parts that are not, and the components that have a hatched structure indicate a state in which a gel electrolyte is impregnated, and the parts that do not indicate a state in which a gel electrolyte is not impregnated.

[0060] Accordingly, in FIG. 2, which will be described later, each component is represented using a hatched structure to illustrate a state in which the components are impregnated with a gel electrolyte. In contrast, the unit cells of FIGS. 3 and 4 are impregnated with a gel electrolyte after manufacturing a laminate according to the present invention, and are not represented with a hatched structure because they are not yet impregnated with a gel electrolyte.

[0061]

[0062] According to one embodiment of the present invention, a bipolar assembly including a laminate including a bipolar electrode and a separator, and a gel electrolyte impregnated throughout the laminate; and a battery case,

[0063] A bipolar battery is provided in which the gel electrolyte voids inside the laminate are 5% or less of the total volume that can be impregnated with the gel electrolyte.

[0064]

[0065] Bipolar assembly

[0066] The above bipolar assembly includes a laminate including a bipolar electrode and a separator, and a gel electrolyte impregnated in the laminate, wherein the gel electrolyte voids of the laminate are 5% or less of the total volume that can be impregnated with the gel electrolyte.

[0067] FIG. 2 schematically illustrates a cross-sectional view to more clearly explain the structure of a bipolar assembly (1000), FIG. 3 schematically illustrates a cross-sectional view of a unit cell forming a bipolar assembly (1000) as an example, and FIG. 4 schematically illustrates a cross-sectional view of a unit cell forming a bipolar assembly (1000) as another example.

[0068] Referring to FIG. 2, the bipolar assembly (1000) includes a laminate (1100), and the laminate (1100) has a structure impregnated with a gel electrolyte.

[0069] At this time, according to the present invention, the gel electrolyte voids inside the laminate (1100) may be substantially non-existent, at 5% or less.

[0070] Here, the gel electrolyte pores are formed when the gel electrolyte is volatilized during the manufacturing of the laminate, so that no gel electrolyte exists, and only materials forming the electrode (representatively, 121) or separator (representatively, 122) exist, and it is not necessary for the gel electrolyte pores to exist uniformly throughout.

[0071] At this time, the gel electrolyte pore means the total volume that can be impregnated with the gel electrolyte, that is, the volume that is not impregnated with the gel electrolyte based on the total volume of the pores of the electrode (representatively, 121) and the pores of the separator (representatively, 122).

[0072] Accordingly, the gel electrolyte pore volume is obtained by calculating the pore volume of each electrode and separator, and at this time, the pore volume can be calculated for each component using the thickness and weight. In addition, the weight of the impregnated electrolyte, that is, the weight difference between before and after the electrolyte impregnated inside the laminate is completely volatilized at high temperature, is calculated, and the impregnation volume of the electrolyte is calculated based on the electrolyte density. Afterwards, by subtracting the electrolyte impregnation volume from the total pore volume of the electrode, the gel electrolyte pore volume is obtained, and thus the ratio of the gel electrolyte pore volume to the total pore volume can be calculated.

[0073] That is, the bipolar assembly (1000) according to the present invention has little volatilization of the gel electrolyte, so that the voids of the gel electrolyte that do not contain the gel electrolyte are almost non-existent, and can be contained at 5% or less, specifically 3% or less, more specifically 0.1% to 2%, and most specifically 0.1% to 1%.

[0074] Meanwhile, the laminate (1100) may have a structure in which unit cells (110, 120, 130, 140, 150, 160) are laminated, and the unit cells (120, 130, 140, 150, 160) may each basically include a bipolar electrode (representatively, 121) and a separator (representatively, 122), and the unit cell (110) may be formed of a bipolar electrode (111) so that a cross-sectional electrode may be positioned at the outermost part of the overall structure.

[0075] This laminate (1100) may have a structure in which cross-sectional electrodes (111, 161) of different polarities are positioned on the outermost sides on both sides in the lamination direction.

[0076] At this time, the bipolar electrode (121) may include an integrated electrode in which a positive electrode active material layer and a negative electrode active material layer are each coated on both sides of a single current collector, a positive electrode in which a positive electrode active material layer is formed on one side of a positive electrode current collector, or a negative electrode in which a negative electrode active material layer is formed on one side of a negative electrode current collector.

[0077] Accordingly, the laminate (1100) may be a structure in which at least one selected from the group consisting of a unit cell having a structure in which the positive electrode active material layer and the separator of the integrated electrode face each other, a unit cell having a structure in which the positive electrode and the negative electrode are separately included and the separator is interposed between the positive electrode and the negative electrode, a unit cell having a structure in which a cross-sectional electrode and a separator are stacked, and a cross-sectional electrode.

[0078] Here, the cross-sectional electrode may be a cross-sectional positive electrode or a cross-sectional negative electrode.

[0079] If the laminate (1100) has a structure in which positive and negative electrodes are alternately arranged, it can be formed by one type of laminate, or it can be formed by mixing two types, or it can be formed by mixing three types.

[0080] The unit cell (110) composed of a cross-sectional electrode (111) and the unit cell (160) having a structure in which a cross-sectional electrode (161) and a separator are laminated are as shown in Fig. 2, and therefore, this structure will not be described in further detail.

[0081] Meanwhile, FIGS. 3 and 4 illustrate two types of unit cells (210, 210') excluding a unit cell having a cross-sectional electrode and a structure in which a cross-sectional electrode and a separator are laminated.

[0082] Referring to FIGS. 3 and 4, FIG. 3 illustrates a unit cell (210) including an integrated electrode, and FIG. 4 illustrates a unit cell (210') having both an anode and a cathode as separate electrodes.

[0083] First, referring to FIG. 3, the unit cell (210) includes an integrated electrode having a structure in which a positive electrode active material layer (212) is formed on one surface of a current collector (211) and a negative electrode active material layer (213) is formed on the other surface.

[0084] The separator (214) may be formed on one or both sides of the positive electrode active material layer (212) and the negative electrode active material layer (213), and its position is not limited, but in detail, it may be formed on one side facing the positive electrode active material layer (212).

[0085] Accordingly, when unit cells (210) having such a structure are sequentially stacked to form a laminate, a separator is positioned at the outermost side on one side, and a cross-sectional electrode can be further included at the outermost side where the separator is positioned, and by positioning the unit cells composed of the separator and the cross-sectional electrode so that no active material layer exists at the outermost side on the other side, a laminate having a structure as shown in FIG. 2 can be completed.

[0086] Next, referring to FIG. 4, the unit cell (210') has a structure in which a positive electrode including a positive active material layer (212') on one side of a positive current collector (211'), a negative electrode including a negative active material layer (214') on one side of a negative current collector (213'), and a separator (215') is interposed between the positive electrode and the negative electrode.

[0087] When these unit cells (210') are sequentially stacked to form a laminate, cross-sectional electrodes of different polarities are positioned on the outermost sides on both sides, so there is no need to include unit cells having a structure in which separate cross-sectional electrodes or cross-sectional electrodes and separators are stacked.

[0088] However, in a laminate of this structure, the unit cells face each other as current collectors, so a conductive adhesive having conductivity may be applied between the current collectors for a more solid bond.

[0089] Referring back to FIGS. 3 and 4, the current collector (211) used in the integrated electrode having the structure of FIG. 3 must have both a positive electrode active material layer (212) and a negative electrode active material layer (213) formed on both sides, so any material that does not cause a chemical change in the battery and is conductive may be used, and is not particularly limited thereto. For example, stainless steel, nickel, titanium, calcined carbon, or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used, but specifically, stainless steel or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, it may be a clad foil made by rolling two or more metal foils, and may have a structure in which two or more metals such as Al, Cu, Ni, and SUS are bonded by cold rolling, and may also have a structure in which another metal is deposited or coated as a thin film on one metal.

[0090] On the other hand, in the unit cell (210') having the structure of FIG. 4 manufactured by separately using a positive electrode collector (211') and a negative electrode collector (213'), the positive electrode collector (211') may be any material that is conductive and does not cause a chemical change in the battery, and is not particularly limited thereto. For example, the current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., but may be specifically an Al current collector. Here, the Al current collector may be made of Al, and here, the concept includes including a material that further contains other metal materials to the extent of an impurity content.

[0091] The negative electrode current collector (121) is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used, and specifically, it can be a Cu current collector, and here, the Cu current collector can be made of Cu, and here, it is a concept including that other metal materials are further included in the degree of impurity content.

[0092] Regardless of its type, the current collector used in the bipolar assembly (1100) may have a thickness of 3 ㎛ to 500 ㎛, and may form fine unevenness on the surface of the current collector to increase adhesion to the active material layer, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0093] The positive electrode active material layer (212, 212') may include a positive electrode active material, a binder, and further a conductive material.

[0094] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and various combinations are possible, for example, lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(wherein, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a1 Fe 1-x1 Mx1 (PO 4-b1 )X b1 (Here, M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, and -0.5≤a1≤0.5, 0≤x1≤0.5, 0≤b1≤0.1) and the like, and any one or two or more compounds thereof may be included, and specifically, a lithium transition metal oxide represented by the following chemical formula 1 may be included, and specifically, 0.5≤x≤0.7, 0≤b≤0.1 may be satisfied, and more specifically, M may be Co and Mn, or may be Co, Mn, and Al.

[0095] [Chemical Formula 1]

[0096] Li 1+a Ni x M 1-x O 2-b X b

[0097] In the above chemical formula 1, M is at least one element selected from the group consisting of Mn, Co, Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, X is at least one element selected from F, S, and N, and 0≤a≤0.5, 0.3≤x<0.8, 0≤b≤0.1.

[0098] Or more specifically, it may be lithium iron phosphate.

[0099] The above binder is a component that assists in bonding between the conductive material, the positive electrode active material, and the positive electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0100] Typically, the binder may be included in an amount of 0.5 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode active material layer (212, 212').

[0101] The conductive agent is a component for further improving the conductivity of the positive electrode active material, and the conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; carbon nanotubes; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0102] The above-mentioned conductive material may be included in an amount of 0.01 to 20 wt%, specifically 0.1 to 10 wt%, and more specifically 0.1 to 5 wt%, based on the total weight of the positive electrode active material layer (212, 212').

[0103] In addition, other additives, such as fillers that suppress expansion, may be further included. The fillers are not particularly limited as long as they can suppress expansion of the electrode without causing chemical changes in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0104] The negative electrode active material layer (213, 214') may include a negative electrode active material, a binder, a conductive material, and other additives as described above.

[0105] The negative active material is at least one carbon-based material selected from the group consisting of graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon, Si-based material, Si / C composite, Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; Al, Cu, Ge, Si, Sn 등의 금속; 리튬 합금; 규소계 합금; 주석계 합금; SiO, SiO2, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물; 리튬 티타늄 산화물 등을 포함할 수 있지만, 당업계에 알려진 것이라면 이들만으로 한정되는 것은 아니다.

[0106] These positive electrode active material layers and negative electrode active material layers can be manufactured by either a wet or dry method. Specifically, either a wet method in which an electrode material including the active material, binder, conductive material, etc. is dispersed in a solvent and coated, or a dry method in which a free-standing film manufactured by dry mixing the active material, conductive material, etc. with a fibrous binder, such as PTFE, and calendering the mixture can be applied.

[0107] The separator (214, 215') can be used without any special restrictions as long as it is a separator commonly used in lithium secondary batteries, and in particular, it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte retention capacity.

[0108] For example, as the separation membrane (214, 215'), a porous polymer film including a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., may also be used as the separation membrane.

[0109] Alternatively, it may be a Safety Reinforced Separator (SRS) membrane in which a coating layer including a binder and inorganic particles is formed on one or both sides of a polymer substrate as described above.

[0110] The polyolefin substrate of the above SRS separator may use the separator materials described above, and the coating layer includes inorganic particles and a binder.

[0111] Here, the inorganic particles play a dual role: they form micropores by allowing the formation of voids between the inorganic particles, and they also serve as a type of spacer that maintains their physical form. Furthermore, since the inorganic particles generally have a property of not changing their physical properties even at temperatures exceeding 200°C, the formed organic-inorganic mixed layer possesses excellent heat resistance.

[0112] The inorganic particles described above are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly limited as long as they do not undergo oxidation and / or reduction reactions within the operating voltage range of the battery to which they are applied. In particular, when using inorganic particles with ion transfer capabilities, it is preferable to use particles with as high an ion conductivity as possible, as this can enhance performance by increasing the ionic conductivity within the electrochemical device. In addition, when the inorganic particles have a high density, it is difficult to disperse them during manufacturing, and there is also the problem of weight increase during battery manufacturing, so it is preferable to use particles with as low a density as possible. In addition, when using inorganic particles with a high dielectric constant, they can contribute to increasing the dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte. Finally, inorganic particles with thermal conductivity are more preferable, as they have excellent heat absorption capabilities, which suppress the phenomenon of heat being concentrated locally, forming a heating point, and leading to thermal runaway.

[0113] For the reasons mentioned above, the inorganic particles are preferably at least one selected from the group consisting of (a) high-dielectric constant inorganic particles having a dielectric constant of 1 or more, 5 or more, preferably 10 or more, (b) inorganic particles having piezoelectricity, (c) thermally conductive inorganic particles, and (d) inorganic particles having lithium ion transfer capability.

[0114] The above piezoelectric inorganic particles are non-conductive at normal pressure, but when a certain pressure is applied, they are materials that have the property of conducting electricity due to a change in their internal structure. In addition, when a certain pressure is applied and they are stretched or compressed, they generate electric charges, so that one side is charged positively and the other side is charged negatively, and they are materials that have the function of generating a potential difference between the two sides.

[0115] Examples of the above piezoelectric inorganic particles include BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT) hafnia (H f O2) or mixtures thereof, but are not limited thereto.

[0116] The above inorganic particles having lithium ion transfer capability refer to inorganic particles that contain lithium elements but do not store lithium and have the function of transferring lithium ions. Since the inorganic particles having lithium ion transfer capability can transfer and move lithium ions due to a type of defect existing within the particle structure, they can prevent a decrease in lithium mobility and thus a decrease in battery capacity.

[0117] Examples of inorganic particles having the above lithium ion transfer capability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), 리튬알루미늄티타늄포스페이트(Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), 14Li2O-9Al2O3-38TiO2-39P2O5등과 같은 (LiAlTiP) x O y Series glass (0 <x<4, 0<y<13), 리튬란탄티타네이트(Li x La y TiO3, 0 <x<2, 0<y<3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x Ge y P z S w, 0 <x<4, 0<y<1, 0<z<1, 0<w<5), Li3N 등과 같은 리튬나이트라이드(Li x N y , 0 <x<4, 0<y<2), Li3PO4-Li2S-SiS2등과 같은 SiS2계열 glass (Li x Si y S z , 0 <x<3, 0<y<2, 0<z<4), LiI-Li2S-P2S5등과 같은 P2S5계열 glass (Li x P y S z , 0 <x<3, 0<y<3, 0<z<7), 또는 이들의 혼합물 등이 있으나, 이에 한정되는 것은 아니다.

[0118] Additionally, examples of inorganic particles having a dielectric constant of 1 or greater include, but are not limited to, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, or mixtures thereof.

[0119] The above thermally conductive inorganic particles are a material having insulating properties by providing low thermal resistance but no electrical conductivity, and may be, for example, at least one selected from the group consisting of aluminum nitride (AlN), boron nitride (BN), alumina (Al2O3), silicon carbide (SiC), boehmite, AlO(OH), and beryllium oxide (BeO), but are not limited thereto.

[0120] When the aforementioned high-k inorganic particles, piezoelectric inorganic particles, thermally conductive inorganic particles, and inorganic particles having lithium ion transfer capability are mixed, their synergistic effect can be doubled.

[0121] The size of the above-mentioned inorganic particles is not limited, but it is preferably in the range of 0.001 to 10 ㎛ to ensure an appropriate porosity between the inorganic particles. If it is less than 0.001 ㎛, dispersibility is reduced, making it difficult to control physical properties. If it exceeds 10 ㎛, the thickness increases, resulting in a deterioration in mechanical properties. In addition, due to the excessively large pore size, the coating layer cannot sufficiently function, increasing the probability of an internal short circuit occurring during battery charging and discharging.

[0122] The content of the above-mentioned inorganic particles is not particularly limited, but is preferably in the range of 1 to 99 wt%, and particularly 10 to 95 wt%, per 100 wt% of the mixture of inorganic particles and binder. When it is less than 1 wt%, the content of the binder becomes too high, which may reduce the pore size and porosity due to a decrease in the empty space formed between the inorganic particles, thereby reducing the mobility of lithium ions. Conversely, when it exceeds 99 wt%, the content of the binder becomes too low, which may result in a decrease in the adhesive strength between the inorganic particles, thereby reducing the mechanical properties of the coating layer.

[0123] Meanwhile, the binder is not limited as long as it does not cause a side reaction with the electrolyte, but in particular, one having a glass transition temperature (Tg) as low as possible can be used, preferably in the range of -200 to 200°C. This is because the mechanical properties of the final insulating film can be improved.

[0124] In addition, the above-mentioned binder does not necessarily need to have ion conducting ability, but it is more preferable to use a polymer having ion conducting ability.

[0125] Therefore, it is preferable that the binder have a permittivity constant as high as possible, and since the degree of salt dissociation in the electrolyte actually depends on the permittivity constant of the electrolyte solvent, the higher the permittivity constant of the polymer, the better the degree of salt dissociation in the electrolyte. The permittivity constant of the polymer is preferably 1 or more, specifically, in the range of 1.0 to 100 (measurement frequency = 1 kHz), and is particularly preferably 10 or more.

[0126] In addition to the aforementioned functions, the binder may have the characteristic of being gelled when impregnated with a liquid electrolyte, thereby exhibiting a high degree of swelling. In fact, if the binder is a polymer having an excellent electrolyte impregnation rate, the electrolyte injected after battery assembly permeates the polymer, and the polymer retaining the absorbed electrolyte has electrolyte ion conductivity. Therefore, if possible, the solubility index should be set to be 15 to 45 MPa. 1 / 2 Polymers are preferred, with a viscosity of 15 to 25 MPa. 1 / 2 and 30 to 45 MPa 1 / 2 The range is more desirable. The solubility index is 15 MPa. 1 / 2 Less than and 45 MPa 1 / 2 If it exceeds , it becomes difficult to be impregnated (swelled) by a conventional battery liquid electrolyte.

[0127] Examples of such binders include polyvinylidene fluorideco-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, It may be at least one selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and polyvinylalcohol.

[0128] The total thickness of the separation membrane (214, 215') may be 5 micrometers to 20 micrometers, specifically 5 micrometers to 15 micrometers, and more specifically 6 micrometers to 13 micrometers.

[0129] In a unit cell for a bipolar battery, the separator (214, 215') may have an area of ​​100% of the area of ​​the negative electrode active material layer or 100% of the entire area of ​​the negative electrode based on the negative electrode among the bipolar electrodes.

[0130] Beyond the above range, if the separator is larger than the cathode area, ionic short-circuiting may occur in the bipolar structure. Therefore, it is preferable to make the separator smaller than the cathode area, and the portion of the cathode current collector that is not covered can be insulated with a separate inorganic coating such as Al2O3 or a polymer film such as PP or PET to prevent short-circuiting between the electrodes.

[0131] Referring again to FIGS. 2 to 4, the laminate (1100) including the electrode (representatively, 121) and the separator (representatively, 122) may have an exposed structure in which each unit cell does not include a sealing member, including a cured gel electrolyte. Here, the exposed structure means a state in which a sealing member or the like is not formed, so that there is no physical barrier between the laminate including the bipolar electrode (representatively, 121) and the separator (representatively, 122).

[0132] In addition, since the bipolar assembly (1000) according to the present invention is impregnated with and cured with a gel electrolyte composition after manufacturing the laminate (1100), all bipolar electrodes and all separators are laminated and combined as a whole, and thus can have a structure in which they are joined to each other.

[0133] Meanwhile, the gel electrolyte comprises a lithium salt and a non-aqueous organic solvent, and at least one polymerizable compound selected from the group consisting of a polymerizable monomer, oligomer, or copolymer having a polymerizable unsaturated functional group, and at least a portion of the polymerizable unsaturated functional group may be cured.

[0134] In other words, the gel electrolyte may be a gel electrolyte composition comprising a lithium salt, a non-aqueous organic solvent, and at least one polymerizable compound selected from the group consisting of a polymerizable monomer, oligomer, or copolymer having a polymerizable unsaturated functional group, which is cured by heat or light.

[0135] The above lithium salt can be used in the same or similar manner as that used in a typical lithium secondary battery. The above lithium salt is used as a medium for transferring ions in a lithium battery, for example, Li as a cation. + , and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 -, CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - At least one selected from the group consisting of

[0136] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 , LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl) imide, LiN(SO2CF2CF3)2) and LiTFSI (lithium bis(trifluoromethanesulfonyl) imide, LiN(SO2CF3)2), but it is preferable to include Li(N(SO2CF3)2) in terms of excellent stability.

[0137] The lithium salt may be appropriately changed within a generally usable range, but in order to obtain an optimal effect of forming a film for preventing corrosion on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 3 M, specifically, at a concentration of 1 M to 2.5 M, and more specifically, at a concentration of 1 M to 2 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of the battery is sufficient, and the viscosity of the electrolyte is appropriate, so that the electrolyte impregnation property can be improved.

[0138] The above non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions, etc. during the subsequent charge / discharge process of the bipolar battery, and can exhibit the desired characteristics together with the additive.

[0139] For example, a carbonate-based organic solvent, an ether-based organic solvent, or an ester-based organic solvent can be used alone or in combination of two or more, and more specifically, a carbonate-based organic solvent can be used.

[0140] Among the organic solvents, the carbonate-based organic solvent may include at least one of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. Specifically, the cyclic carbonate-based organic solvent may include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate (FEC), and specifically, may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.

[0141] In addition, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more specifically, may include dimethyl carbonate.

[0142] The above ether organic solvent may be any one selected from the group consisting of ethylene glycol dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more thereof, but is not limited thereto.

[0143] The above ester organic solvent may include at least one selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0144] Specific examples of the linear ester organic solvent include, but are not limited to, one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more thereof.

[0145] The above cyclic ester organic solvent may be, as a specific example, one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof, but is not limited thereto.

[0146] Among the above ester solvents, cyclic carbonate compounds are preferably used as high-viscosity organic solvents with high dielectric constants, which facilitate the dissociation of lithium salts in the electrolyte. When low-viscosity, low-dielectric constant linear carbonate compounds and linear ester compounds, such as dimethyl carbonate and diethyl carbonate, are mixed and used in an appropriate ratio with these cyclic carbonate compounds, an electrolyte with high electrical conductivity can be produced, and thus the compounds can be used more preferably.

[0147] Furthermore, the electrolyte may further include a functional additive, and the functional additive may be included to prevent cathode collapse from occurring in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and swelling improvement effects during high-temperature storage.

[0148] Specifically, the functional additive may include at least one functional additive selected from the group consisting of, as representative examples, sultone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogen-substituted carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and lithium salt compounds.

[0149] The above sultone-based compound may include at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, and may be included in an amount of 0.3 wt% to 5 wt%, specifically 1 wt% to 5 wt%, based on the total weight of the gel electrolyte. When the content of the sultone-based compound in the gel electrolyte exceeds 5 wt%, an excessively thick film may be formed on the electrode surface, which may cause an increase in resistance and a deterioration in output, and the resistance may also increase due to an excessive amount of additive, which may deteriorate the output characteristics.

[0150] The above sulfite compound may include at least one compound selected from the group consisting of ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butylene glycol sulfite, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0151] The above sulfone compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methylvinyl sulfone, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0152] The above sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS), and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0153] In addition, the halogen-substituted carbonate compound may include fluoroethylene carbonate (FEC) and may be included in an amount of 5 wt% or less based on the total weight of the gel electrolyte. If the content of the halogen-substituted carbonate compound in the gel electrolyte exceeds 5 wt%, cell swelling performance may deteriorate.

[0154] In addition, the nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0155] The above cyclic carbonate compound may be vinylene carbonate (VC) or vinylethylene carbonate, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte. If the content of the cyclic carbonate compound in the gel electrolyte exceeds 3 wt%, the cell swelling inhibition performance may deteriorate.

[0156] The above phosphate compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethyl silyl phosphate, trimethyl silyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0157] The above borate compound may include lithium oxalyldifluoroborate, and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0158] The lithium salt-based compound is a compound different from the lithium salt included in the lithium non-aqueous electrolyte, and may include at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2) and LiBF4), and may be included in an amount of 3 wt% or less based on the total weight of the gel electrolyte.

[0159] The functional additives may be mixed in an amount of two or more, or less than 20 wt%, specifically 0.1 wt% to 10 wt%, based on the total weight of the gel electrolyte. If the content of the functional additive exceeds 20 wt%, there is a possibility that excessive side reactions may occur within the electrolyte during charging and discharging of the battery. In particular, since they may not be sufficiently decomposed at high temperatures, they may exist as unreacted substances or precipitated substances within the electrolyte at room temperature. As a result, side reactions that reduce the lifespan or resistance characteristics of the battery may occur.

[0160] Meanwhile, the bipolar assembly (1000) according to the present invention can drastically reduce electrolyte volatilization during the manufacturing process by the manufacturing method according to the present invention described below, and thus, it is not necessary to include an electrolyte composition having a volatilization temperature (flash point) of less than 90°C as the non-aqueous organic solvent or functional additive, and the degree of freedom in selecting the electrolyte is high.

[0161] More specifically, the bipolar assembly (1000) according to the present invention may include an electrolyte composition having a flash point of less than 90° C. in an amount of 10% or more, specifically 20% to 100%, more specifically 30% to 70%, and most specifically 60% to 80%, based on the total solvent volume of the electrolyte composition included in the gel electrolyte.

[0162] The content of the electrolyte composition having a flash point of less than 90°C can be determined through solvent analysis of the entire gel electrolyte. More specifically, the content can be determined by dissolving the gel electrolyte in a specific solvent, such as acetone, and then performing an electrolyte composition analysis.

[0163] The electrolyte composition having a flash point of less than 90°C may be, for example, a linear ester solvent or a linear carbonate solvent.

[0164] More specifically, the electrolyte composition having a flash point of less than 90°C may be at least one selected from the group consisting of methyl formate, ethyl formate, 1,2-dimethoxyethane, methyl acetate, 1,3-dioxolane, ethyl acetate, methyl propionate, propyl acetate, methyl butyrate, tris(trimethylsilyl)phosphate, dimethyl carbonate, propyl propionate, ethylmethyl carbonate, diethyl carbonate, ethyl propionate, ethyl butyrate, butyronitrile, ethylmethylsulfone, propyl butyrate, diethylene glycol dimethyl ether, vinylene carbonate, and glycol sulfite, and among these, as non-aqueous organic solvents and functional additives listed above, carbonate-based and propionate-based materials may be more suitably used, and for example, dimethyl carbonate, propyl propionate, At least one selected from the group consisting of ethyl methyl carbonate, diethyl carbonate, ethyl propionate, and vinylene carbonate may be included in an amount of 10% by volume or more, specifically 20% to 100% by volume, more specifically 30% to 70% by volume, and most specifically 60% to 80%.

[0165] The electrolyte composition having a flash point of less than 90°C has high volatility, but has excellent high-temperature storage characteristics and has a positive effect on improving rate characteristics and life characteristics, and thus has high utility in batteries.

[0166] In conventional manufacturing methods, these materials were difficult to use due to their high volatility, but in the present invention, since electrolyte volatilization can be drastically reduced, these electrolyte compositions can be used.

[0167] In addition, the gel electrolyte must contain a polymerizable compound of a polymerizable monomer, oligomer or copolymer for gelation, and the polymerizable compound is a substance having a polymerizable unsaturated functional group, for example, a polymerizable unsaturated functional group selected from the group consisting of a vinyl group, an epoxy group, an allyl group and a (meth)acrylic group, and is a compound that can be changed into a gel form by polymerization or crosslinking, and is not particularly limited as long as it is a polymerizable monomer, oligomer or polymer used for manufacturing a conventional gel electrolyte.

[0168] More specifically, the polymerizable monomer or oligomer may be, but is not limited to, tetraethyleneglycoldiacrylate, polyethylene glycol diacrylate (molecular weight 50 to 20,000), 1,4-butanediol diacrylate, 1,6-hexandioldiacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol. Pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, poly(ethyleneglycol) diglycidylether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexenedioxide, 1,2,7,8-diepoxyoctane,Examples thereof include, but are not limited to, 4-vinylcyclohexenedioxide, butyl glycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidylmethacrylate, and these compounds may be used alone or in combination of two or more.

[0169] In addition, the copolymer may include at least one copolymer selected from the group consisting of representative examples thereof, such as allyl 1,1,2,2-tetrafluoroethyl ether (TFE)-(2,2,2-trifluoroethyl acrylate) polymer, TFE-vinyl acetate, TFE-(2-vinyl-1,3-dioxolane) polymer, TFE-vinyl methacrylate polymer, TFE-acrylonitrile polymer, TFE-vinyl acrylate polymer, TFE-methyl acrylate polymer, TFE-methyl methacrylate (MMA) polymer, and TFE-2,2,2-trifluoroethyl acrylate (FA) polymer.

[0170] The polymer formed through the curing of the above materials may be included in an amount of 0.01 wt% to 20 wt% based on the total weight of the gel electrolyte. If the content of the polymer exceeds 20 wt%, the amount of polymerizable material increases during the manufacture of the gel electrolyte, resulting in a disadvantage in that gelation occurs too quickly or is formed too densely, resulting in a gel with high resistance. Conversely, if the content is less than 0.01 wt%, the effect of gelation cannot be obtained, which is undesirable.

[0171] Meanwhile, the gel electrolyte of the present invention may further include a polymerization initiator for polymerization of the polymerizable unsaturated functional group, and a conventional thermal or photoinitiator known in the art may be used. For example, the initiator may be decomposed by heat to form radicals, which may react with a polymerizable monomer, oligomer, or polymer through free radical polymerization to form a gel electrolyte.

[0172] More specifically, examples of the polymerization initiator include organic peroxides or hydroperoxides such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butylperoxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide and hydrogen peroxide, and 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN; 2,2'-Azobis(iso-butyronitrile)). One or more azo compounds selected from the group consisting of 2,2'-azobisdimethyl-valeronitrile (AMVN), but is not limited thereto.

[0173] The above polymerization initiator can be decomposed by heat, for example, heat of 30°C to 100°C, within a bipolar unit cell, or decomposed at room temperature (5°C to 30°C) to form radicals, and a polymerizable unsaturated functional group of a polymerizable monomer, oligomer, or polymer can react by free radical polymerization to form a gel electrolyte.

[0174] The polymerization initiator may be included in an amount of 0.01 to 20 parts by weight, specifically 0.01 to 1 part by weight, based on 100 parts by weight of the polymerizable compound.

[0175] When the above polymerization initiator is in the range of 0.01 to 20 parts by weight, the gel conversion rate can be increased to secure gel electrolyte properties, and the pre-gel reaction can be prevented to improve the electrolyte wetting property for the electrode.

[0176]

[0177] bipolar battery

[0178] FIG. 5 schematically illustrates a cross-sectional view of a bipolar battery (2000) including a bipolar assembly (1000).

[0179] Referring to FIG. 5, a bipolar battery (2000) has a structure in which a positive terminal (2100) and a negative terminal (2200) are attached to each of the cross-sectional electrodes located at the outermost part of the bipolar assembly (1000) and are built into a battery case (2300).

[0180] At this time, the positive terminal (2100) and the negative terminal (2200) may have a structure that extends to the outside of the battery case (2300) so that electrical withdrawal to the outside is possible, and may be a structure in which charging and discharging are performed through electrical connection.

[0181] The drawing shows a form in which the positive terminal (2100) and the negative terminal (2200) are attached separately, but instead of the terminal form, the current collector of the outermost electrode may take over that role, or a separate metal plate with a size of 50% to 110% of the current collector area may be attached to the outside of the current collector to take over that role.

[0182] The battery case (2300) may be a conventional pouch-type battery case or a metal battery case, and is not limited thereto, but specifically may be a pouch-type battery case, and as another example, a polymer plastic material such as polyolefin, specifically, polypropylene, may also be used.

[0183]

[0184] Bipolar battery manufacturing method

[0185] According to another embodiment of the present invention, a method for manufacturing the bipolar battery comprises:

[0186] (a) Prepare a unit cell by stacking bipolar electrodes and a separator,

[0187] (b) A laminate is manufactured by stacking two or more of the above unit cells and placing a cross-sectional electrode on the outermost surface,

[0188] (c) A method for manufacturing a bipolar assembly is provided, which comprises storing the laminate in a storage member containing a gel electrolyte composition, impregnating the laminate, and curing the gel electrolyte composition under pressure to form a gel electrolyte.

[0189] For convenience of understanding, FIG. 6 schematically illustrates a method for manufacturing a bipolar assembly (1000) according to the present invention.

[0190] First, to manufacture a bipolar assembly (1000), a unit cell is manufactured by stacking a bipolar electrode (211) and a separator (212) (a).

[0191] Specifically, the bipolar electrode (211) and separator (212) are each cut into unit sizes before lamination, and a unit cell is manufactured by bonding them together.

[0192] At this time, the adhesion of the bipolar electrode (211) and the separator (212) can be achieved by using an adhesive or laminating them.

[0193] In the drawing, the structure in which the bipolar electrode (211) and the separator (212) are laminated one by one is depicted, but it is obvious that the unit cell can be formed in various structures as described above.

[0194] That is, according to the manufacturing method of the present invention, a unit cell is manufactured without impregnating a separate gel electrolyte composition into the bipolar electrode (201) and the separator (202). Therefore, the problem of volatilization of the gel electrolyte composition does not occur during the manufacturing process of the bipolar electrode (201) and the separator (202) and the manufacturing process of the unit cell.

[0195] Additionally, unit cells may have an exposed structure without forming a separate isolation membrane or sealing member. Accordingly, since a sealing structure is not formed for each unit cell, the unit cells can be manufactured in a simpler manner, thereby increasing the efficiency of the assembly process.

[0196] Afterwards, a laminate (210) is manufactured by stacking two or more unit cells including a bipolar electrode (201) and a separator (202) and placing cross-sectional electrodes (203) on both outermost sides (b).

[0197] At this time, each unit cell and cross-sectional electrode are aligned and stacked so that the positive and negative electrodes are alternately arranged. Since no separate pressurization is performed, each unit cell is not completely joined and can have a predetermined space between them.

[0198] Therefore, the impregnation of the gel electrolyte composition to be performed later can be easily accomplished by impregnating the components of each unit cell.

[0199] In addition, since the laminate (210) has cross-sectional electrodes (203) arranged on both sides of the outermost shell, a current collector is positioned on the outermost shell. Since the current collector is made of a material such as a metal foil, it can act as a protective film that prevents volatilization of the gel electrolyte composition impregnated in the bipolar electrode (201) and separator (202).

[0200] Accordingly, according to the manufacturing method of the present invention, since the laminate (210) is manufactured before the gel electrolyte composition is impregnated, even if the gel electrolyte composition is subsequently impregnated into the bipolar electrode (201) and separator (202), the possibility of the gel electrolyte composition being exposed to the surface and volatilizing can be drastically reduced.

[0201] Meanwhile, after manufacturing the laminate (210) in this manner, it is stored in a storage member (220) containing a gel electrolyte composition (221) and impregnated (c).

[0202] That is, according to the manufacturing method of the present invention, electrolyte impregnation is possible by simply housing the laminate (210) in a housing member (220) containing a gel electrolyte composition (221). Therefore, the manufacturing process can also be simplified. At this time, the housing member (220) may be an open-type electrolyte box with an open top, or a battery case housing the laminate (210).

[0203] That is, as in one example in FIG. 6, a bipolar battery can be manufactured by manufacturing a bipolar assembly (1000) impregnated with a gel electrolyte through a process of placing the laminate (210) separately in an electrolyte box and impregnating it, then removing the laminate (210) to remove the gel electrolyte composition (221) remaining on the outside of the laminate (210) and curing it, and then storing it in a battery case.

[0204] Alternatively, although not shown in Fig. 6, the laminate (210) may be housed in a battery case, a gel electrolyte composition may be injected, and then the case may be sealed and then subjected to a curing process in that state.

[0205] Meanwhile, in any case, in order to uniformly impregnate the gel electrolyte composition (221) into the bipolar electrode (201) and the separator (202), the impregnation of the gel electrolyte composition (221) may be performed under vacuum.

[0206] Specifically, the laminate (210) is stored in the storage member (220), and more specifically, one side of the storage member (220) is opened, and the gel electrolyte composition (221) can be impregnated by repeatedly applying and releasing vacuum in the vacuum chamber (230).

[0207] At this time, vacuum application may be repeated four or more times to apply and release the vacuum.

[0208] At this time, the vacuum application can be maintained for 3 to 10 minutes per time in the range of -100 kPa to -90 kPa, and more specifically, can be maintained for 5 to 7 minutes per time in the range of -97 kPa to -93 kPa.

[0209] The above vacuum release can be maintained for 1 to 10 minutes per session.

[0210] The vacuum application including such vacuum application and release may be performed four or more times, specifically, five or more times and ten or less times, and, considering both the impregnation property of the gel electrolyte composition and the manufacturing time, more specifically, seven or eight times.

[0211] Thereafter, a room temperature aging process may be performed so that the gel electrolyte composition can be sufficiently impregnated into each material, and for example, the laminate (210) may be stored in a storage member (220) at room temperature for about 24 hours to 5 days.

[0212] When the gel electrolyte composition (221) is sufficiently impregnated into the laminate (210) in this way, the gel electrolyte composition (221) is cured under pressure to form a gel electrolyte (d).

[0213] At this time, in one example, as illustrated in FIG. 6, the curing of the gel electrolyte composition (221) can be performed while the laminate (210) is pressurized by an external jig (250).

[0214] Alternatively, although not shown in the drawing, if the storage member is a battery case, the storage member may be sealed and the laminate may be stored within the storage member and pressurized by an external jig.

[0215] In any case, since the bipolar electrode (241) and separator (242) are impregnated and cured with the gel electrolyte composition (221) in the state of a laminate (210), the electrolyte volatilization is drastically reduced, and the area where the gel electrolyte does not exist, i.e., the gel electrolyte pores, can be drastically reduced, and since both the electrode (241) and the separator (242) can be bonded by the curing of the gel electrolyte composition (221), the overall structure can be firmly bonded. Therefore,

[0216] There is an effect that the thickness of the laminate (210) can be adjusted to the range of the design thickness while further improving the battery performance.

[0217] This curing can also be performed in a vacuum, and can be performed by applying light irradiation or heat. The light irradiation has the advantage of enabling curing in a short time, but since it is difficult to uniformly apply light irradiation to the inside of the laminate (210) due to the external jig (250), it can be performed by applying heat, specifically.

[0218] Specifically, the method of applying heat to harden the laminate (210) or the laminate (210) stored in a storage member while being pressurized by an external jig (250) can be performed by placing the laminate (210) in a vacuum high-temperature chamber (260) and applying heat.

[0219] The above heat application can be performed in the range of 50°C to 80°C for 2 to 10 hours, specifically in the range of 60°C to 80°C for 4 to 8 hours, and more specifically in the range of 60°C to 70°C for 4 to 6 hours.

[0220] Additionally, the vacuum state can be achieved by connecting a vacuum pump capable of creating a vacuum within the high-temperature chamber. When the curing process is performed under vacuum, the absence of oxygen enhances curing properties, further enhancing the performance of the resulting bipolar battery.

[0221] Meanwhile, according to the bipolar battery manufacturing method of the present invention, after the gel electrolyte composition (221) is cured, a process of removing the pressure may be further included (d).

[0222] The above pressure relief is performed by separating the external jig (250). By removing the pressure in this manner, a bipolar assembly (1000) completely impregnated with a gel electrolyte is manufactured.

[0223] Although not shown in the drawing, if the storage member is a battery case, a bipolar battery is manufactured.

[0224] Meanwhile, when manufacturing as a bipolar assembly, an additional process of removing impurities from the outside can be performed, and a bipolar battery can be manufactured through additional processes such as packaging and electrode terminal attachment to manufacture a bipolar battery.

[0225]

[0226] Hereinafter, examples will be described to demonstrate that the present invention exhibits the intended improved effects.

[0227]

[0228] <Comparative Example 1>

[0229] As a cathode active material, LiFePO4, as a conductive material, carbon nanotubes, and as a binder, PVDF were dispersed in an NMP solvent at a weight ratio of 96:1:3, and the cathode slurry was coated on one side of an Al metal thin film to a thickness of 110 micrometers, dried, and rolled to manufacture a cathode.

[0230] In addition, LiPF6 was dissolved to 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC) : ethyl methyl carbonate (EMC) = 30 : 70 (volume ratio). A gel electrolyte composition was prepared by adding 10 wt% of trimethylolpropane triacrylate as a polymerizable compound based on the total weight and 0.4 wt% of azobisisobutyronitrile (AIBN, V59) as a polymerization initiator based on 100 wt% of the polymerizable compound.

[0231] The positive electrode was immersed in an electrolyte box containing the above gel electrolyte composition, a vacuum was applied, and the positive electrode was stored for 3 days after impregnation. The positive electrode was removed, a transparent film was covered on the electrode surface to prevent the surface electrolyte from volatilizing, and then the positive electrode was cured.

[0232] The above vacuum application was repeated 8 times by applying -95 kPa for about 5 minutes and then releasing the vacuum, and then stored at room temperature for 3 days.

[0233] Curing of the above gel electrolyte composition was performed by UV photocuring.

[0234]

[0235] Comparative Example 2

[0236] The positive electrode manufactured in Comparative Example 1 was used.

[0237] In addition, LiPF6 was dissolved to 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC) : gamma-butyrolactone (GBL) = 30 : 70 (volume ratio). A gel electrolyte composition was prepared by adding 10 wt% of trimethylolpropane triacrylate as a polymerizable compound based on the total weight and 0.4 wt% of azobisisobutyronitrile (AIBN, V59) as a polymerization initiator based on 100 wt% of the polymerizable compound.

[0238] The positive electrode was immersed in an electrolyte box containing the above gel electrolyte composition, a vacuum was applied, and the positive electrode was stored for 3 days after impregnation. The positive electrode was removed, a transparent film was covered on the electrode surface to prevent the surface electrolyte from volatilizing, and then the positive electrode was cured.

[0239] The above vacuum application was repeated 8 times by applying -95 kPa for about 5 minutes and then releasing the vacuum, and then stored at room temperature for 3 days.

[0240] Curing of the above gel electrolyte composition was performed by UV photocuring.

[0241]

[0242] <Example>

[0243] As a negative electrode active material, a mixture of graphite and SiO (weight ratio 95:5), carbon black as a conductive material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a filler were dispersed in a water solvent at a weight ratio of 96:1:2:1, and the resulting negative electrode slurry was coated on one side of a Cu metal thin film to a thickness of 80 micrometers, dried, and rolled to manufacture a negative electrode.

[0244] A unit cell was manufactured by interposing a CCS separator (thickness: 13 micrometers) formed with an organic / inorganic mixed layer (Al2O3: PVdF = 95:5) on both sides of a polyolefin substrate as a separator between the positive electrode and the negative electrode manufactured in the comparative example above.

[0245] The above unit cell was placed in an electrolyte box containing the gel electrolyte composition of the comparative example, and vacuum application was repeated 8 times by applying -95 kPa for about 5 minutes and then releasing the vacuum. After that, the unit cell was taken out from the electrolyte box and stored at room temperature for 3 days.

[0246] Thereafter, the gel electrolyte composition was cured, and the curing was performed by applying heat at about 60°C for 5 hours.

[0247]

[0248] Experimental Example 1

[0249] In order to compare the degree of electrolyte volatilization between the case where the electrode and separator themselves were impregnated with electrolyte and a bipolar assembly was manufactured, and the case where the electrolyte was impregnated after manufacturing a laminate according to the present invention, the following experiment was conducted.

[0250] Specifically, in order to measure the electrolyte volatilization amount of the electrodes manufactured in Comparative Examples 1 and 2 and the unit cells manufactured in the examples, the weight change over time was measured while leaving them at room temperature before curing the gel electrolyte composition, and the electrolyte volatilization amount was measured in the following manner, and the results are shown in Table 1 and Fig. 7 below.

[0251] *Total volatile amount (%) = (Total weight of electrolyte before storage - Weight of electrolyte after storage) / Total weight of electrolyte after storage *100

[0252] The above electrolyte weight is the weight of the electrode or unit cell after impregnation minus the weight of the electrode or unit cell before impregnation.

[0253] At this time, since the example consists of two electrodes, the total volatility was calculated by dividing it by two.

[0254] Time(min)Comparative Example 1(%)Comparative Example 2(%)Example(%)0000113.93.70.32218.64.90.56324.46.30.60426.76.80.61529.07.40.741034.88.70.842040.710.20.843044.111.01.066046.511.61.18

[0255] Referring to Table 1 above and FIG. 7 below, when manufacturing using a conventional manufacturing method, it can be confirmed that the amount of electrolyte volatilization over time is very large because the electrode is exposed to the surface, and furthermore, it can be confirmed that the volatility is high even when an electrolyte solvent having a volatilization temperature of 90°C or higher is used. On the other hand, when going through a manufacturing process like the present invention, it can be confirmed that the amount of electrolyte volatilization is significantly reduced, and thus, according to the present invention, the degree of freedom in selecting the electrolyte composition can be increased. In addition, it can be expected that the bipolar battery according to the present invention has almost no gel electrolyte volatilization.

[0256]

[0257] Experimental Example 2

[0258] As a negative electrode active material, a mixture of graphite and SiO (weight ratio 95:5), carbon black as a conductive material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a filler were dispersed in a water solvent at a weight ratio of 96:1:2:1, and the resulting negative electrode slurry was coated on one side of a Cu metal thin film to a thickness of 70 micrometers, dried, and rolled to manufacture a negative electrode.

[0259] The negative electrode was immersed in an electrolyte box containing the above gel electrolyte composition, vacuum was applied, and the negative electrode was stored for 3 days after impregnation. The negative electrode was removed, a transparent film was covered on the electrode surface to prevent the surface electrolyte from volatilizing, and then cured. The curing method was as described in the comparative example.

[0260] In addition, as a separator, a CCS separator (thickness: 13 micrometers) having an organic-inorganic mixed layer (Al2O3: PVdF = 95:5) formed on both sides of a polyolefin substrate was immersed in an electrolyte box, vacuum was applied, and after impregnation, it was stored for 3 days, the separator was removed, covered with a transparent film to prevent the surface electrolyte from volatilizing, and then cured. Using a positive electrode, a negative electrode, and a separator each impregnated with a gel electrolyte, 3 stacks were laminated to manufacture a bipolar battery of Comparative Example 1. During the manufacturing process, the amount of the electrolyte of Comparative Example 1 was reduced from 1.91 cc to 1.66 cc, a decrease of about 13.1 volume%.

[0261] In addition, a bipolar battery of the embodiment was manufactured using the unit cell of the embodiment. The amount of electrolyte of the embodiment was reduced from 2.07 cc to 2.02 cc, a decrease of approximately 1.75 volume percent. Therefore, it can be seen that the gel electrolyte voids within the laminate are less than 2%. This is almost similar to the case where the gel electrolyte voids are obtained by subtracting the volume of the impregnated electrolyte from the total void volume using the method defined above, with an error range of less than 1%.

[0262]

[0263] The bipolar battery of Comparative Example 1 manufactured above and the bipolar battery of the Example were subjected to initial (one-time) charge and discharge using an electrochemical charger / discharger. At this time, charging was performed by applying current at a current density of 0.1 C-rate up to a voltage of 4.3 V, and discharging was performed at the same current density up to 2.5 V. Such charge and discharge were performed a total of 5 times.

[0264] During the above charging and discharging process, the voltage and capacity of the positive and negative electrodes included in each battery were measured, and the results are shown in Figures 8 and 9 below. In addition, the discharge capacity of each battery is shown in Table 2 below.

[0265] Cycle Comparison Example 1 (mAh) Example (mAh) 139.81497.721238.96494.907336.03293.439434.07690.301531.3885.938

[0266] Referring to the following Figures 8 and 9 and Table 2, in the case of the bipolar battery of Comparative Example 1, many pores are generated due to the gel electrolyte volatilized from the electrodes and separator, and precipitation occurs severely due to the lack of electrolyte, resulting in a very large battery irreversibility and a rapid decrease in capacity, whereas the bipolar battery of the example shows improved life performance.

[0267] Anyone with ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

[0268] The bipolar battery according to the present invention has the effect of minimizing electrolyte volatilization during the impregnation and curing process of the gel electrolyte, thereby uniformly impregnating the bipolar electrode and separator with the gel electrolyte, and since almost no gel electrolyte pores are generated inside the laminate, the performance of the bipolar battery can also be improved.

[0269] The bipolar battery of the present invention also has the effect of simplifying the structure by applying a gel electrolyte without applying a separate sealing structure.

[0270] Furthermore, since the method for manufacturing a bipolar battery according to the present invention has a structure in which a plurality of unit cells are laminated and impregnated at once by placing the laminated body itself into a storage member rather than injecting electrolyte into individual unit cells, volatilization of the gel electrolyte composition during the manufacturing process can be minimized, and since even a volatile gel electrolyte material can be applied, there is a high degree of freedom in selecting the type of electrolyte, and the electrolyte impregnation time can be saved.

Claims

1. A bipolar assembly comprising a laminate including a bipolar electrode and a separator, and a gel electrolyte impregnated throughout the laminate; and a battery case; A bipolar battery in which the gel electrolyte voids within the laminate are 5% or less of the total volume that can be impregnated with the gel electrolyte.

2. In paragraph 1, The above bipolar electrode is a bipolar battery including an integrated electrode in which a positive electrode active material layer and a negative electrode active material layer are each coated on both sides of a single current collector, a positive electrode in which a positive electrode active material layer is formed on one side of a positive electrode current collector, or a negative electrode in which a negative electrode active material layer is formed on one side of a negative electrode current collector.

3. In paragraph 2, The laminate is a bipolar battery having a structure in which at least one selected from the group consisting of a unit cell having a structure in which the positive electrode active material layer of the integrated electrode and the separator face each other, a unit cell having a structure in which the positive electrode and the negative electrode are separately included and the separator is interposed between the positive electrode and the negative electrode, a unit cell having a structure in which a cross-sectional electrode and a separator are stacked, and a cross-sectional electrode.

4. In paragraph 1, The above laminate is a bipolar battery in which cross-sectional electrodes of different polarities are positioned on the outermost sides on both sides in the stacking direction.

5. In paragraph 1, The above laminate is a bipolar battery that does not include a sealing member.

6. In paragraph 1, A bipolar battery comprising an electrolyte composition having a flash point of less than 90°C, wherein the gel electrolyte is 7. In paragraph 6, A bipolar battery in which the electrolyte composition having a flash point of less than 90°C is included in the gel electrolyte in an amount of 10% or more based on the total volume of the electrolyte composition.

8. In paragraph 6, A bipolar battery, wherein the electrolyte composition having a flash point of less than 90°C comprises at least one selected from the group consisting of methyl formate, ethyl formate, 1,2-dimethoxyethane, methyl acetate, 1,3-dioxolane, ethyl acetate, methyl propionate, propyl acetate, methyl butyrate, tris(trimethylsilyl)phosphate, dimethyl carbonate, propyl propionate, ethylmethyl carbonate, diethyl carbonate, ethyl propionate, ethyl butyrate, butyronitrile, ethylmethylsulfone, propyl butyrate, diethylene glycol dimethyl ether, vinylene carbonate, and glycol sulfite.

9. In paragraph 1, A bipolar battery in which all of the bipolar electrodes and all of the separators included in the laminate are laminated and combined as a whole by the gel electrolyte.

10. In paragraph 1, A bipolar battery in which a positive terminal and a negative terminal are attached to the outermost electrodes on both sides in the stacking direction of the above bipolar assembly.

11. A method for manufacturing a bipolar battery, (a) Prepare a unit cell by stacking bipolar electrodes and a separator, (b) A laminate is manufactured by stacking two or more of the above unit cells and placing a cross-sectional electrode on the outermost surface, (c) A method for manufacturing a bipolar battery, comprising: storing the laminate in a storage member containing a gel electrolyte composition, impregnating the laminate, and curing the gel electrolyte composition under pressure to form a gel electrolyte.

12. In paragraph 11, The above unit cell is a method for manufacturing a bipolar battery, wherein the above bipolar electrode and the above separator are each cut into unit sizes and then bonded to each other.

13. In paragraph 11, A method for manufacturing a bipolar battery, wherein each of the above unit cells does not include a sealing member.

14. In paragraph 11, A method for manufacturing a bipolar battery, wherein the gel electrolyte composition comprises an electrolyte composition having a flash point of less than 90°C in an amount of 10% or more based on the total solvent volume.

15. In paragraph 11, A method for manufacturing a bipolar battery, wherein the above-mentioned storage member is an open-type electrolyte box with an open upper portion or a battery case that stores the above-mentioned laminate.

16. In paragraph 15, A method for manufacturing a bipolar battery further comprising a process of storing the laminate in a battery case after forming the gel electrolyte, when the storage member is the electrolyte box.

17. In paragraph 11, A method for manufacturing a bipolar battery, wherein the impregnation of the above gel electrolyte composition is performed under vacuum.

18. In paragraph 17, A method for manufacturing a bipolar battery, wherein the above vacuum application is performed by repeating vacuum application and vacuum release four or more times.

19. In paragraph 18, A method for manufacturing a bipolar battery, wherein the above vacuum application is maintained for 3 to 10 minutes at a time in the range of -100 kPa to -90 kPa.

20. In paragraph 11, A method for manufacturing a bipolar assembly, wherein the above curing is performed by applying heat in a vacuum state at a temperature ranging from 50°C to 80°C for 2 to 10 hours.

21. In paragraph 11, A method for manufacturing a bipolar battery further comprising a step of releasing a pressurized state after curing the gel electrolyte composition.

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