Bipolar unit cell, and bipolar battery containing the same.

Abstract

According to one embodiment of the present invention, a bipolar battery is provided that includes a positive electrode current collector, a positive electrode material layer formed on one surface of the positive electrode current collector, a negative electrode current collector, a negative electrode material layer formed on one surface of the negative electrode current collector, and a separation membrane, wherein the positive electrode material layer and the negative electrode material layer are stacked facing each other with the separation membrane in between, and a sealing portion that adheres from the other surface of the positive electrode current collector to the other surface of the negative electrode current collector to integrally form the stack and seal the inside, wherein a conductive layer is formed on the outside of at least one of the positive electrode current collector and the negative electrode current collector, and a bipolar battery is provided having a structure in which two or more of the bipolar unit cells are stacked.

Description

[Technical Field] 【0001】 [Cross-reference of related applications] This application claims priority rights based on Korean Patent Application No. 10-2024-0059696 dated May 7, 2024, and all content disclosed in the said Korean Patent Application is incorporated herein by reference. 【0002】 The present invention relates to a bipolar unit cell and a bipolar battery containing the same. [Background technology] 【0003】 Recently, the application areas of lithium-ion batteries have rapidly expanded from power supply for electronic devices such as electrical, electronic, telecommunications, and computers to power storage and supply for large-area devices such as automobiles and energy storage devices. As a result, there is a growing demand for high-capacity, high-output, and highly stable secondary batteries. 【0004】 Electrodes used in such secondary batteries can be classified into monopolar electrodes, in which an active material having the same polarity is coated on both sides of the current collector, and bipolar electrodes, in which an active material having different polarities is coated on both sides of the current collector. 【0005】 Secondary batteries using monopolar electrodes have connection points that link the electrodes, which may lead to a decrease in output due to the electrical resistance of these connections. Secondary batteries using bipolar electrodes do not have connection points and stack the electrodes, thus minimizing the connection resistance of the electrodes. 【0006】 Despite these advantages, bipolar electrode secondary batteries have difficulty increasing their capacity. Conventionally, bipolar electrodes are formed by coating both sides of a current collector with positive and negative electrode active materials, mainly with a stainless steel current collector in between, and the electrolyte is formed in a structure where it is isolated on both sides with the current collector in the center. 【0007】 However, when stainless steel foil is repeatedly used as a current collector, there are durability issues. Furthermore, because the positive electrode active material and negative electrode active material, which contain different substances, are formed on both sides of the current collector, their flexibility differs, and there are limitations to adjusting them even when the required conditions differ. 【0008】 Furthermore, bipolar batteries using bipolar electrodes contain an electrolyte, and it is extremely important to prevent leakage of this electrolyte, especially if it contains a liquid or gel electrolyte. Conventionally, gaskets were used to seal bipolar batteries, but there is a problem in that gaskets are difficult to manufacture with a thickness of 1 mm or less. If the gasket thickness is too large, the gap between the bipolar electrodes becomes large, resulting in a problem of reduced output relative to the volume. 【0009】 Therefore, there is a need to develop bipolar batteries that can solve these problems while ensuring battery safety and improving performance. [Overview of the project] [Problems that the invention aims to solve] 【0010】 The present invention aims to provide a bipolar unit cell and a bipolar battery that effectively prevent electrolyte leakage in bipolar batteries while filling the space between bipolar electrodes, thereby ensuring the safety of the bipolar battery by preventing electrode warping, preventing battery warping, and ensuring uniform current transmission, while also providing excellent battery performance such as lifespan characteristics. [Means for solving the problem] 【0011】 A laminate comprising a positive electrode current collector, a positive electrode material layer formed on one surface of the positive electrode current collector, a negative electrode current collector, a negative electrode material layer formed on one surface of the negative electrode current collector, and a separation membrane, wherein the positive electrode material layer and the negative electrode material layer are laminated facing each other with the separation membrane in between, It includes a sealing portion that adheres from the other surface of the positive electrode current collector to the other surface of the negative electrode current collector to form the laminate integrally and seal the inside, The internal space formed by the sealing portion contains a liquid electrolyte or a gel electrolyte. A bipolar unit cell is provided, in which a conductive layer is formed on the outside of at least one of the positive electrode current collector and the negative electrode current collector. 【0012】 The conductive layer may have a thickness corresponding to the thickness in the stacking direction of the sealing portion attached to the other surface of the positive electrode current collector and the negative electrode current collector, respectively. 【0013】 Furthermore, the conductive layer may be formed over an area of ​​90% to 100% of the other surface area of ​​the positive electrode current collector or the negative electrode current collector, excluding the area where the sealing portion is formed. 【0014】 Such a conductive layer may be a conductive tape or a conductive sealant, and may contain copper or carbon. 【0015】 The conductive layer may further contain an adhesive substance. In this case, the adhesive substance may include one or more from the group consisting of acrylic resins, phenolic resins, xylene resins, styrene resins, epoxy compounds, urethane resins, vinyl resins, and synthetic rubbers. 【0016】 The electronic conductivity of such a conductive layer is 10 -10 S / m~10 -7 It can be S / m. 【0017】 On the other hand, the sealing portion can be a sealing tape or a curable sealant. 【0018】 The positive electrode current collector can be an Al current collector, and the negative electrode current collector can be a Cu current collector. 【0019】 According to yet another embodiment of the present invention, a bipolar battery comprising two or more bipolar unit cells, The bipolar unit cells are stacked with current collectors of opposite polarities facing each other, and the bipolar battery has a separation space in the stacking direction due to a sealing portion formed on the outer frame of the bipolar unit cells, and a conductive layer is located in the separation space. 【0020】 Here, the conductive layer may have a thickness corresponding to the distance of the separation space in the stacking direction. [Brief explanation of the drawing] 【0021】 [Figure 1] This is a schematic cross-sectional view of a bipolar unit cell according to one embodiment of the present invention. [Figure 2] Figure 1 is a top view of the positive electrode side of the bipolar unit cell. [Figure 3] This is a schematic cross-sectional view of a bipolar battery according to one embodiment of the present invention. [Figure 4] This is a graph showing the lifetime characteristics based on Experimental Example 1. [Modes for carrying out the invention] 【0022】 Hereafter, terms and words used in this specification and claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner and concept consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best describe their inventions. 【0023】 Unless otherwise defined, all terms used herein (including technical and scientific terms) should be used in a sense that is commonly understood by a person of ordinary skill in the art to which this invention pertains. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise. 【0024】 The terms used herein are for illustrative purposes only and are not intended to limit the invention. In this specification, singular terms include plural terms unless otherwise specified in the text. The terms “comprises” and / or “comprising” as used in this specification do not preclude the presence or addition of one or more other components in addition to those mentioned. 【0025】 In this specification, when a part includes a component, this does not exclude other components, unless otherwise stated, but rather means that it may include other components. 【0026】 In this specification, "average particle size D50" refers to the particle size at 50% of the volume-cumulative particle size distribution of the particle powder to be measured (e.g., positive electrode active material powder, negative electrode active material powder, etc.). The average particle size D50 can be measured using the laser diffraction method. For example, the particle powder to be measured can be dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), irradiated with ultrasound at approximately 28 kHz at an output of 60 W, a volume-cumulative particle size distribution graph is obtained, and the particle size corresponding to 50% of the volume-cumulative amount can be determined. 【0027】 Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described below. In this specification and drawings, the same reference numerals indicate the same components. 【0028】 Bipolar unit cell According to one embodiment of the present invention, a bipolar unit cell is provided. 【0029】 Figure 1 schematically shows a cross-sectional view of the bipolar unit cell 100 according to the present invention, and Figure 2 shows a top view of the positive electrode side of the bipolar unit cell 100. 【0030】 Referring to Figure 1, the bipolar unit cell 100 includes a positive electrode current collector 111, a positive electrode material layer 112 formed on one surface of the positive electrode current collector 111, a negative electrode current collector 121, a negative electrode material layer 122 formed on one surface of the negative electrode current collector 121, and a separator membrane 130, and has a structure in which the positive electrode material layer 112 and the negative electrode material layer 122 are stacked facing each other with the separator membrane 130 in between. 【0031】 The positive electrode current collector 111 is not particularly limited, as long as it is conductive and does not induce any chemical changes in the battery. For example, the current collector can be stainless steel, aluminum, nickel, titanium, plastic carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. More specifically, it can be an Al current collector. Here, an Al current collector can be made of Al, and this concept includes cases where other metallic substances are further included in amounts corresponding to impurities. 【0032】 The positive electrode current collector 111 can have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance adhesion to the positive electrode active material layer. For example, it can be used in a variety of forms such as films, sheets, wheels, nets, porous materials, foams, and nonwoven fabrics. 【0033】 The positive electrode layer 121 may include a positive electrode active material, a binder, and a conductive material. 【0034】 The positive electrode active material is a compound capable of reversible intercalation and di-intercalation of lithium, and various combinations are possible. For example, lithium-manganese-based oxides (such as LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (such as LiCoO2, etc.), lithium-nickel-based oxides (such as LiNiO2, etc.), lithium-nickel-manganese-based oxides (such as LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2, etc.), lithium-nickel-cobalt-based oxides (such as LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (such as LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (such as Li(Ni p Co q Mn r )O2 (where 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (such as Li(Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s2 are the atomic fractions of the respective independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (such as Li 1+a1 Fe 1-x1 M x1 (PO 4-b1 )X b1(Here, M is one or more selected from Al, Mg, and Ti, and X is one or more selected from F, S, and N, with -0.5 ≤ a1 ≤ 0.5, 0 ≤ x1 ≤ 0.5, 0 ≤ b1 ≤ 0.1) and so on, and one or more of these compounds may be included. 【0035】 More specifically, it can include lithium transition metal oxides represented by the following chemical formula 1, and more specifically, 0.5 ≤ x ≤ 0.7 and 0 ≤ b ≤ 0.1, and more specifically, LiNi 0.6 Co 0.1 Mn 0.3 Contains O2. 【0036】 [Chemical formula 1] Li 1+a Ni x M 1-x O 2-b X b In the above chemical formula 1, M is one or more elements selected from the group consisting of Mn, Co, Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and X is one or more elements selected from F, S, and N, with 0 ≤ a ≤ 0.5, 0.3 ≤ x < 0.8, and 0 ≤ b ≤ 0.1. 【0037】 Alternatively, it can be lithium iron phosphate oxide. 【0038】 The binder is a component that assists in the bonding between the conductive material, the positive electrode active material, and the positive electrode current collector. 【0039】 Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof. 【0040】 Typically, the binder can be included in an amount of 0.5 to 20% by weight, more specifically 0.5 to 10% by weight, or more specifically 0.5 to 5% by weight, based on the total weight of the positive electrode material layer 112. 【0041】 The conductive material is a component for further improving the conductivity of the positive electrode active material, and such a conductive material is not particularly limited as long as it does not induce a chemical change in the battery and is conductive. Examples of such conductive materials that can be used include 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 crystalline structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. 【0042】 The conductive material may be included in an amount of 0.1 to 20% by weight, more specifically 0.5 to 10% by weight, or more specifically 0.5 to 5% by weight, based on the total weight of the positive electrode material layer 112. 【0043】 Furthermore, other additives such as fillers that suppress expansion may be included. The filler is not particularly limited as long as it can suppress the expansion of the electrodes without inducing a chemical change in the battery, and for example, olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fibers and carbon fibers; etc. can be used. 【0044】 The negative electrode current collector 121 is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, nickel, titanium, plastic carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy can be used. More specifically, it may be a Cu current collector, where the Cu current collector may consist of Cu, and this concept includes the inclusion of other metallic substances in amounts corresponding to impurities. 【0045】 The negative electrode current collector 121 can typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the negative electrode current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in a variety of forms such as films, sheets, wheels, nets, porous materials, foams, and nonwoven fabrics. 【0046】 The negative electrode layer 122 may include a negative electrode active material and the binder, conductive material, and other additives as described above. 【0047】 The negative electrode active material is one or more carbon-based materials, Si-based materials, Li selected from the group consisting of graphite, amorphous hard carbon, low-crystalline soft carbon, carbon black, acetylene black, Ketjenblack, Super P, graphene, and fibrous carbon. 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, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8) and other metal composite oxides; lithium metal; metals such as Al, Cu, Ge, Si, Sn; lithium alloys; silicon-based alloys; tin-based alloys; metal oxides such as SiO, SiO2, SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanates, etc. can be included, but if it is known in the art, it is not limited to these. 【0048】 The separation membrane 130 can be used without particular limitation as long as it is usually used as a separation membrane in a lithium secondary battery, and it is particularly preferable that it has a low resistance to the ion movement of the electrolyte and excellent electrolyte moisture retention ability. 【0049】 For example, as the separation membrane 130, a porous polymer film containing polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof can be used. Also, a normal porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. may be used as the separation membrane. 【0050】 Alternatively, it may be an SRS (Safety Reinforced Separator) separation membrane in which a coating layer containing a binder and inorganic particles is formed on one or both sides of the polymer base material as described above. 【0051】 The polyolefin base material of the SRS separation membrane can use the separation membrane materials described above, and the coating layer contains inorganic particles and a binder. 【0052】 Here, the inorganic particles serve two purposes: to form micropores by enabling the creation of empty spaces between them, and to act as a kind of spacer that maintains its physical form. Furthermore, since the inorganic particles generally have the property of not changing their physical properties even at high temperatures of 200°C or higher, the resulting inorganic mixed layer will have excellent heat resistance. 【0053】 The inorganic particles are not particularly limited as long as they are electrochemically stable. In other words, 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 capability, it is preferable that they have as high an ionic conductivity as possible, as this can improve performance by increasing the ionic conductivity within the electrochemical element. Furthermore, if the inorganic particles have a high density, it is not only difficult to disperse them during manufacturing, but there is also the problem of increased weight during battery manufacturing, so it is preferable that they have as low a density as possible. In addition, in the case of inorganic materials with a high dielectric constant, it is possible to improve the ionic conductivity of the electrolyte by increasing the degree of dissociation of the electrolyte salt, such as lithium salt, in the liquid electrolyte. Finally, inorganic particles with thermal conductivity are even more preferable because they have excellent heat endothermic capacity, which suppresses the phenomenon of heat concentrating locally, forming heat-generating points, and leading to thermal runaway. 【0054】 For the reasons stated above, the inorganic particles are preferably one or more 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) piezoelectric inorganic particles, (c) thermally conductive inorganic particles, and (d) inorganic particles having lithium ion transport capability. 【0055】 The piezoelectric inorganic particles are substances that are insulators under normal pressure but have the property of conducting electricity due to changes in their internal structure when a certain pressure is applied. They not only exhibit high dielectric constant characteristics with a dielectric constant of 100 or more, but also have the function of generating charges when a certain pressure is applied and stretched or compressed, causing one side to be positively charged and the opposite side to be negatively charged, thereby generating a potential difference between both side surfaces. 【0056】 Examples of the inorganic particles having piezoelectricity 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, etc., but are not limited thereto. 【0057】 The inorganic particles having lithium ion transfer ability refer to inorganic particles that contain lithium elements, do not store lithium, and have the function of moving lithium ions. Since the inorganic particles having lithium ion transfer ability can transfer and move lithium ions due to a kind of defect existing inside the particle structure, it is possible to prevent a decrease in lithium mobility and thus prevent a reduction in battery capacity. 【0058】 Examples of the inorganic particles having lithium ion transfer ability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), 14Li2O-9Al2O3-38TiO2-39P2O5), etc. such as (LiAlTiP) x O ySeries of glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate such as Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride such as Li3N (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 series glass such as Li3PO4 - Li2S - SiS2 (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5 series glass such as LiI - Li2S - P2S5 (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), or mixtures thereof, etc., but not limited thereto. 【0059】 Examples of inorganic particles having a dielectric constant of 1 or more include, but are not limited to, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, or mixtures thereof. 【0060】 The thermally conductive inorganic particles provide low thermal resistance but do not provide electrical conductivity and are substances having insulating properties. For example, they are one or more selected from the group consisting of aluminum nitride (AlN), boron nitride (BN), alumina (Al2O3), silicon carbide (SiC), and beryllium oxide (BeO), but not limited thereto. 【0061】 When the aforementioned high dielectric constant inorganic particles, piezoelectric inorganic particles, thermally conductive inorganic particles, and inorganic particles with lithium ion transfer capability are used in combination, their effects can be doubled. 【0062】 While there are no restrictions on the size of the inorganic particles, it is preferable that they be in the range of 0.001 to 10 μm to ensure an appropriate porosity between the inorganic particles. If the size is less than 0.001 μm, dispersibility decreases and it becomes difficult to adjust the physical properties. If the size exceeds 10 μm, the thickness increases and mechanical properties deteriorate. Furthermore, excessively large pore size prevents the coating layer from functioning adequately, increasing the probability of internal short circuits during battery charging and discharging. 【0063】 The content of the inorganic particles is not particularly limited, but it is preferably in the range of 1 to 99% by weight per 100% by weight of the mixture of inorganic particles and binder, and more preferably 10 to 95% by weight. If it is less than 1% by weight, the binder content will be excessively high, which may reduce the pore size and porosity due to the decrease in the empty spaces formed between the inorganic particles, and may reduce the mobility of lithium ions. Conversely, if it exceeds 99% by weight, the binder content will be too low, which will weaken the adhesive strength between the inorganic materials and reduce the mechanical properties of the coating layer. 【0064】 On the other hand, the binder is not limited as long as it does not undergo a side reaction with the electrolyte, but in particular, one with the lowest possible glass transition temperature (Tg) can be used, preferably in the range of -200 to 200°C. This is because it can improve the mechanical properties of the final insulating film. 【0065】 Furthermore, while the binder does not necessarily need to have ion-conducting ability, it is even more preferable to use a polymer that does have ion-conducting ability. 【0066】 Therefore, it is preferable that the binder has as high a dielectric constant as possible, because the degree of salt dissociation in the electrolyte actually depends on the dielectric constant of the electrolyte solvent. The higher the dielectric constant of the polymer, the better the degree of salt dissociation in the electrolyte can be improved. The dielectric constant of the polymer can be 1 or higher, more specifically in the range of 1.0 to 100 (measurement frequency = 1 kHz), and is particularly preferably 10 or higher. 【0067】 In addition to the functions described above, the binder may have the characteristic of gelling upon impregnation with a liquid electrolyte, thereby exhibiting a high electrolyte impregnation rate (degree of swelling). In fact, if the binder is a polymer with excellent electrolyte impregnation rate, the electrolyte injected after battery assembly will penetrate the polymer, and the polymer holding the absorbed electrolyte will acquire electrolyte ion conductivity. Therefore, if possible, the solubility index should be 15-45 MPa. 1 / 2 A polymer is preferred, and the pressure is 15-25 MPa. 1 / 2 and 30-45 MPa 1 / 2 A range is even more preferable. Solubility index of 15 MPa 1 / 2 Less than and 45 MPa 1 / 2 If the value exceeds a certain level, it becomes difficult for the material to be impregnated (swelled) by a typical liquid electrolyte used in batteries. 【0068】 Examples of such binders include polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. It can be one or more selected from the group consisting of propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, and polyvinyl alcohol. 【0069】 The total thickness of the separation membrane 130 can be 5 micrometers to 20 micrometers, more specifically 5 micrometers to 15 micrometers, and even more specifically 6 micrometers to 13 micrometers. 【0070】 On the other hand, as can be seen in conjunction with Figures 1 and 2, in order to more effectively prevent leakage of the electrolyte impregnated into the components thereafter, each bipolar unit cell 100 is connected and attached from the other side of the positive electrode current collector 111 to the other side of the negative electrode current collector 121 to form the components as a single unit, and a sealing portion 140 that seals the inside is formed in such a way that it surrounds the periphery of the positive electrode current collector 111 and the negative electrode current collector 121 as a frame. 【0071】 Furthermore, when the sealing portion 140 is formed on the outside of the other side of the current collectors 111 and 121 in this manner, there is no need to reduce the area or volume of the positive electrode material layer 112 and the negative electrode material layer 122 by the sealing portion 140, which is even better in terms of battery capacity, and process efficiency is improved because the sealing layer does not need to be formed internally but can be formed on the outside after lamination. 【0072】 Such a sealing portion 140 can be a sealing tape or a curable sealant, but more specifically, since it must be bonded and sealed to the outer surfaces of the positive electrode current collector 111 and the negative electrode current collector 121, it may be a sealing tape. In this case, the sealing tape is not limited as long as it is a material with good chemical resistance and strong adhesive strength, but for example, it can be a material selected from the group consisting of polyimide (PI), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). The curable sealant can be a material selected from the group consisting of acrylic resins, phenolic resins, xylene resins, styrene resins, epoxy compounds, urethane resins, vinyl resins, and synthetic rubber, and can be a material that hardens with light or heat. 【0073】 In the internal space formed by such a sealing portion 140, the components are impregnated with a liquid electrolyte or a gel electrolyte. The injection and impregnation of the impregnated liquid electrolyte or gel electrolyte can be performed before sealing or during the sealing process, and are not limited to these methods. 【0074】 The liquid electrolyte contains a lithium salt and a non-aqueous organic solvent. 【0075】 The lithium salt can be the same as or similar to those commonly used in lithium secondary batteries. The lithium salt is used as a mediator for transmitting ions in a lithium battery. For example, as a cation, it contains Li + and as an anion, it includes 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 at least one selected from the group consisting of SCN - . 【0076】 Specifically, the lithium salts are LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB 10 Cl 10 It may contain a single substance or a mixture of two or more substances selected from the group consisting of 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) due to its superior stability. 【0077】 The lithium salt can be appropriately modified within a range of normal use, but in order to obtain the optimal effect of forming a protective film to prevent corrosion on the electrode surface, it can be included in the electrolyte at a concentration of 0.5 M to 3 M, more specifically, 1 M to 2.5 M, and more specifically, 1 M to 2 M. When the concentration of the lithium salt meets the above range, the effect of improving the cycle characteristics during high-temperature storage of the battery is sufficient, the viscosity of the electrolyte is appropriate, and the electrolyte impregnation is improved. 【0078】 The aforementioned non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charging and discharging process of the bipolar battery and can exhibit the desired properties together with the additive. For example, carbonate-based organic solvents, ether-based organic solvents, or ester-based organic solvents can be used individually or in combination of two or more types, and in particular, carbonate-based organic solvents can be used. 【0079】 The carbonate organic solvent among the aforementioned organic solvents may include at least one of cyclic carbonate organic solvents and linear carbonate organic solvents. Specifically, the cyclic carbonate organic solvent may include at least one selected from the group consisting of ethylene carbonate (ethylene carbonate, EC), propylene carbonate (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). Specifically, it may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively lower melting point compared to ethylene carbonate. 【0080】 Furthermore, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may contain at least one selected from the group consisting of dimethylcarbonate (DMC), diethylcarbonate (DEC), dipropylcarbonate, ethylmethylcarbonate (EMC), methylpropylcarbonate, and ethylpropylcarbonate, and more specifically, it may contain dimethylcarbonate. 【0081】 The ether-based organic solvent may be 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 of these, but is not limited thereto. 【0082】 The ester-based organic solvent mentioned above is at least one selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents. 【0083】 The linear ester-based organic solvent can typically be any 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 of these, but is not limited to these examples. 【0084】 The cyclic ester organic solvent may, but is not limited to, 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 of these. 【0085】 Among the ester-based solvents, cyclic carbonate compounds are preferred because they have a high dielectric constant as high-viscosity organic solvents and effectively dissociate lithium salts in the electrolyte. Furthermore, when such cyclic carbonate compounds are mixed with low-viscosity, low-dielectric-constant linear carbonate compounds and linear ester compounds, such as dimethyl carbonate and diethyl carbonate, in appropriate ratios, an electrolyte with high electrical conductivity can be produced, and this method is even more preferred. 【0086】 Furthermore, the electrolyte may further contain a functional additive, which may be included to prevent the induction of negative electrode collapse in high-power environments, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and swelling improvement effects during high-temperature storage. 【0087】 Specifically, the functional additive may include, as a representative example, one or more functional additives selected from the group consisting of 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. 【0088】 The sultone compound mentioned above includes at least one compound selected from the group consisting of 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, and 1-methyl-1,3-propensultone, and can be included in an amount of 0.3% to 5% by weight, specifically 1% to 5% by weight, based on the total weight of the electrolyte. If the content of the sultone compound in the electrolyte exceeds 5% by weight, an excessively thick film may be formed on the electrode surface, potentially causing increased resistance and output degradation. In addition, excessive additives may increase resistance and degrade the output characteristics. 【0089】 The aforementioned sulfite compounds include one or more compounds 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-dimethylpropylene sulfite, 4,5-diethylpropylene sulfite, 4,6-dimethylpropylene sulfite, 4,6-diethylpropylene sulfite, and 1,3-butylene glycol sulfite, and can be included in an amount of 3% by weight or less based on the total weight of the electrolyte. 【0090】 The sulfone compound mentioned above includes one or more compounds selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone, and can be included in an amount of 3% by weight or less based on the total weight of the electrolyte. 【0091】 The sulfate compounds mentioned above include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyltrimethylene sulfate (MTMS), and can be included in an amount of 3% by weight or less based on the total weight of the electrolyte. 【0092】 Furthermore, the halogen-substituted carbonate compound may be fluoroethylene carbonate (FEC), and may be included in an amount of 5% by weight or less based on the total weight of the electrolyte. If the content of the halogen-substituted carbonate compound in the electrolyte exceeds 5% by weight, the cell swelling performance may deteriorate. 【0093】 Furthermore, the nitrile compounds include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile. 【0094】 The cyclic carbonate compound may be vinylene carbonate (VC) or vinylethylene carbonate, and may be present in an amount of 3% by weight or less based on the total weight of the electrolyte. If the content of the cyclic carbonate compound in the electrolyte exceeds 3% by weight, the cell swelling suppression performance may deteriorate. 【0095】 The phosphate compound mentioned above includes one or more compounds selected from the group consisting of lithium difluoro(bisoxalato) phosphate, lithium difluorophosphate, tetramethyltrimethylsilyl phosphate, trimethylsilyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphate, and can be included in an amount of 3% by weight or less based on the total weight of the electrolyte. 【0096】 The borate compound mentioned above is lithium oxalyl difluoroborate, and can be included in an amount of 3% by weight or less based on the total weight of the electrolyte. 【0097】 The lithium salt compound is a compound different from the lithium salt contained in the lithium non-aqueous electrolyte and includes one or more compounds selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2) and LiBF4), and can be included in an amount of 3% by weight or less based on the total weight of the electrolyte. 【0098】 The functional additives may be a mixture of two or more types, and may be included in an amount of 20% by weight or less, specifically 0.1% to 10% by weight, based on the total weight of the electrolyte. If the content of the functional additives exceeds 20% by weight, excessive side reactions may occur in the electrolyte during battery charging and discharging. In particular, they may not decompose sufficiently at high temperatures and may remain unreacted or precipitated in the electrolyte at room temperature. This may cause side reactions that reduce the battery's lifespan or resistance characteristics. 【0099】 The gel electrolyte, in addition to the lithium salt and non-aqueous organic solvent, comprises at least one polymerizable compound selected from the group consisting of polymerizable monomers, oligomers, or copolymers having polymerizable unsaturated functional groups, and at least a portion of the polymerizable unsaturated functional groups may be cured. 【0100】 The polymerizable monomer, oligomer, or copolymer polymer is a substance having a polymerizable unsaturated functional group, for example, a polymerizable unsaturated functional group selected from the group consisting of vinyl groups, epoxy groups, allyl groups, and (meth)acrylic groups, and is a compound that can be transformed into a gel type by polymerization or crosslinking, and is not particularly limited as long as it is used as a polymerizable monomer, oligomer, or polymer in the production of ordinary gel-type electrolytes. 【0101】 More specifically, the polymerizable monomer or oligomer is, as non-limiting examples, tetraethylene glycol diacrylate, polyethylene glycol diacrylate (molecular weight 50-20,000), 1,4-butanediol diacrylate, 1,6-hexandiold diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, and pentaerythritol ethoxylate tetraacrylate. (ethoxylate tetraacrylate), dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, polyethylene glycol diglycidyl ether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane (1,2,7,Examples include, but are not limited to, 8-diepoxyoctane, 4-vinylcyclohexenedioxide, butyl glycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate. These compounds can be used individually or in combination of two or more. 【0102】 Furthermore, typical examples of the copolymer include at least one copolymer selected from the group consisting of 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. 【0103】 The polymer formed through the curing of the aforementioned substance can be included in an amount of 0.01% to 10% by weight based on the total weight of the gel-type electrolyte. If the polymer content exceeds 10% by weight, the amount of polymerizable substance increases during the production of the gel-type electrolyte, resulting in the disadvantage of excessively rapid gelation or excessively dense formation, which leads to a gel with high resistance. Conversely, if the content is less than 0.01% by weight, the effects of gelation are not obtained, which is undesirable. 【0104】 On the other hand, the gel-type electrolyte of the present invention may further contain a polymerization initiator for polymerization of the polymerizable unsaturated functional group, and conventional thermal or photoinitiators known in the art may be used. For example, the initiator may be decomposed by heat to form radicals, which can then react with polymerizable monomers, oligomers, or polymers by free radical polymerization to form a gel-type electrolyte. 【0105】 More specifically, examples of polymerization initiators include benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide, and hydrogen peroxide. Examples include, but are not limited to, organic peroxides such as peroxides, hydroperoxides, and one or more azo compounds selected from the group consisting of 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN; 2,2'-Azobis(iso-butyronitrile)), and 2,2'-azobisdimethyl-valeronitrile (AMVN; 2,2'-Azobisdimethyl-Valeronitrile). 【0106】 The polymerization initiator can be decomposed within a bipolar unit cell by heat, in non-limiting examples, at temperatures of 30°C to 100°C, or at room temperature (5°C to 30°C) to form radicals, and the polymerizable monomer, oligomer, or polymerizable unsaturated functional groups can react by free radical polymerization to form a gel-type electrolyte. 【0107】 The polymerization initiator may be included in an amount of 0.01 to 20 parts by weight, more specifically 0.01 to 1 part by weight, based on 100 parts by weight of the polymerizable compound. 【0108】 When the polymerization initiator is in the range of 0.01 to 20 parts by weight, the gel conversion rate can be increased to ensure gel-type electrolyte properties, and the free-gel reaction can be prevented, thereby improving the electrolyte wetting properties to the electrode. 【0109】 On the other hand, a conductive layer 150 is formed on the outside of at least one of the positive electrode current collector 111 and the negative electrode current collector 121. 【0110】 Since the sealing portion 140 is formed on the other side of the positive electrode current collector 111 and the other side of the negative electrode current collector 121, it is formed on the outer surface of the bipolar unit cell 100. 【0111】 In this case, when multiple bipolar unit cells 100 are stacked, the sealing portion 140 creates a separation space between each bipolar unit cell 100. However, when such a separation space is formed, contact between the electrodes of adjacent bipolar unit cells 100 is not made properly, resulting in uneven current flow and reduced electrolyte preservation. Furthermore, the separation space not only prevents uniform pressure from being applied during pressurization, but also increases the risk of electrode warping due to expansion and contraction of the electrodes during charging and discharging of the bipolar battery. This can also lead to warping of the entire bipolar battery, thus compromising safety. 【0112】 Therefore, in order to fill the separation space, a conductive layer 150 having both electronic conductivity and adhesive properties is formed on the outer surface of the positive electrode current collector 111, the negative electrode current collector 121, or all of them. 【0113】 Such a conductive layer 150 is intended to eliminate the separation space and prevent the electrodes from warping, and therefore can have a thickness t that corresponds to the thickness t in the stacking direction of the sealing portion 140 attached to the other surface of the positive electrode current collector and the negative electrode current collector, respectively. 【0114】 In other words, the thickness tc of the conductive layer 150 can be the same as the thickness t of the sealing portion 140, or if there is a predetermined difference, it can be formed to have a thickness difference of within 10%, more specifically within 5%, or even more specifically within 1% of the thickness t of the sealing portion 140. 【0115】 In other words, by forming them with nearly the same thickness, it is possible to achieve not only the prevention of electrode warping intended by this invention, but also a uniform current transmission effect, thereby improving battery performance. 【0116】 Similarly, the area Sc of the conductive layer 150 can be formed with an area Sc of 80% to 100% of the other surface area of ​​the positive electrode current collector 111 or negative electrode current collector 121 on which the conductive layer 150 is formed, excluding the area on which the sealing portion 140 is formed. More specifically, it can be formed with an area Sc of 90% to 100%. 【0117】 Here, the conductive layer 150 can be a conductive tape or a conductive sealant. In other words, it can be formed with a tape or a sealant layer. 【0118】 Here, the conductive tape may be a copper tape or a carbon tape containing copper or carbon, which are conductive materials. 【0119】 Forming the conductive layer 150 in tape form in this way simplifies the process. 【0120】 Furthermore, the conductive sealant may contain conductive particles and an adhesive substance. 【0121】 In this case, the conductive particles are any conductive particles, and may be, for example, carbon, metal, or other materials. More specifically, they may be carbon such as carbon black, carbon nanotubes, or graphene, or metals such as copper, aluminum, platinum, silver, titanium, or nickel. More specifically, they may include copper particles or carbon particles. 【0122】 Here, the average particle size D50 of the conductive particles may be 100 nm to 1000 μm, and more specifically, 10 μm to 100 μm. 【0123】 If the thickness is too large and falls outside the aforementioned range, it becomes difficult to easily adjust the thickness of the conductive layer 150, and if it is too small, there is a problem that the conductive path becomes long. 【0124】 The adhesive substance, like the sealing portion, may contain one or more materials from the group consisting of acrylic resins, phenolic resins, xylene resins, styrene resins, epoxy compounds, urethane resins, vinyl resins, and synthetic rubbers, and more specifically, it may be an acrylic resin. 【0125】 As explained above, such a conductive layer 150 must enable uniform current transmission between the positive and negative electrodes, and since such transmission affects the performance of the bipolar battery, the electronic conductivity of the conductive layer 150 must be 10 -10 S / m~10 -5 It may be S / m, see 10 for details. -10 S / m~10 -7 It may be S / m, and for more details, see 10 -10 S / m~10 -8 It can be S / m. 【0126】 Having an electronic conductivity within the above range is preferable for battery performance. If it is lower than the above range, sufficient conductivity cannot be obtained, and it is not easy to manufacture a conductive layer with a conductivity higher than the above range. 【0127】 bipolar battery According to yet another embodiment of the present invention, a bipolar battery is provided that includes two or more of the bipolar unit cells. 【0128】 Figure 3 schematically shows a cross-sectional view of such a bipolar battery 1000. 【0129】 Referring to Figure 3, the bipolar battery 1000 consists of a structure in which two or more bipolar unit cells 100, 200, and 300 are stacked facing each other, with current collectors 111, 121, 211, and 222 having opposite polarities. 【0130】 Specifically, the negative electrode current collector 121 of the bipolar unit cell 100 and the positive electrode current collector 211 of the bipolar unit cell 200 are stacked facing each other, and the bipolar unit cell 200 and the bipolar unit cell 300 are also stacked with current collectors of opposite polarities facing each other. Therefore, current can be obtained through contact between these components. 【0131】 However, as pointed out in the explanation of the bipolar unit cell 100 in Figure 1, the bipolar unit cells 100, 200, and 300 of this application have sealing portions 140, 240, and 340 formed on their outer surfaces, respectively. As a result, the bipolar unit cells 100, 200, and 300 have a separation space in the stacking direction at a distance of approximately twice the thickness of the sealing portions 140, 240, and 340. 【0132】 Therefore, these separation spaces may cause electrode warping to occur in the bipolar battery 1000 during the charging and discharging process, making it difficult to transmit current uniformly and potentially leading to a phenomenon where current concentrates in only a part of the battery, thus increasing resistance. For this reason, conductive layers 150' and 250' can be formed in these separation spaces. 【0133】 At this time, the conductive layers 150' and 250' formed in the separation space are formed in advance on the surface of each bipolar unit cell 100, 200, and 300 when they are manufactured, corresponding to the thickness of the sealing portion, so that they can come into contact with each other. Alternatively, when stacking the bipolar unit cells 100, 200, and 300, a conductive layer can be filled in the separation space between them, or the conductive layers 150' and 250' can be formed on the surfaces of the bipolar unit cells 100, 200, and 300 that come into contact with each other to be approximately twice the thickness of the sealing portion 140, 240, and 340, and stacked in various ways. The manufacturing method is not limited as long as a conductive layer is formed in the separation space between them. 【0134】 In this case, the conductive layers 150' and 250' can be formed with a thickness tc corresponding to the distance d in the stacking direction of the separation space. 【0135】 In this case, the corresponding thickness can be formed to be the same as the distance d of the separation space of the conductive layer 150, or if there is a predetermined difference, it can be a slight difference, that is, a thickness difference of within 10%, more specifically within 5%, or even more specifically within 1% of the distance d of the separation space. 【0136】 On the other hand, although not shown in the drawings, the bipolar battery 1000 manufactured in this manner has a structure in which a positive electrode lead is connected to the positive electrode current collector located on the outermost side of the stacked bipolar unit cells, enabling electrical extraction to the outside, and a negative electrode lead is connected to the negative electrode current collector located on the outermost side, enabling electrical extraction to the outside, thereby enabling charging and discharging through electrical connection. 【0137】 The following will be a description with reference to examples to demonstrate that the present invention exhibits the improved effects intended. 【0138】 <Example 1> A cathode slurry was prepared by dispersing LiFePO4 as the cathode active material, carbon nanotubes as the conductive material, and PVDF as the binder in an NMP solvent in a weight ratio of 98:1:1. This slurry was then coated onto one side of an Al metal thin film to a thickness of 100 micrometers, leaving a frame portion, and then dried and rolled to produce the cathode. 【0139】 A negative electrode slurry was prepared by dispersing a mixture of natural graphite and artificial graphite (weight ratio 50:50) as the negative electrode active material, carbon black as the conductive material, styrene-butadiene rubber (SBR) as the binder, and carboxymethylcellulose (CMC) as the filler in an aqueous solvent in a weight ratio of 96:1:2:1. This slurry was then coated onto one side of a Cu metal thin film to a thickness of 120 micrometers, leaving a frame portion, and then dried and rolled to produce the negative electrode. 【0140】 A CCS separation membrane (thickness: 13 micrometers) was used as the separation membrane, in which an inorganic mixed layer (Al2O3:PVdF=95:5) was formed on both sides of a polyolefin substrate. 【0141】 Furthermore, an electrolyte composition was prepared by dissolving LiPF6 in a non-aqueous organic solvent having a composition of ethylene carbonate (EC):ethyl methyl carbonate (EMC) = 30:70 (volume ratio) to a concentration of 1.0 M. 【0142】 The positive electrode, negative electrode, and separation membrane were impregnated with the electrolyte composition. During this process, a vacuum was applied and released five times, after which any excess electrolyte composition remaining on the surface was removed. The positive electrode and the negative electrode, both impregnated with the electrolyte composition, were laminated with the separation membrane impregnated with the electrolyte composition in between, and then pressed together. To seal them, a sealing tape PI was applied, covering the other side of the negative electrode from the other side of the positive electrode. After preparing two such unit cells, a semi-solid bipolar cell was manufactured by laminating the other side of the Cu metal thin film of the negative electrode of one unit cell opposite the other side of the Al metal thin film of the positive electrode of the other unit cell, and filling the separation space formed between them with a conductive adhesive (carbon sealant). 【0143】 <Comparative Example 1> A semi-solid bipolar cell was manufactured in the same manner as in Example 1, except that a conductive adhesive was not filled between the two unit cells. 【0144】 <Experimental Example 1> The semi-solid bipolar cells of Example 1 and Comparative Example 1 manufactured above were charged at 0.02C (1.22mA) and 6.4V cut-off, then degassed, and subjected to 10 CC-CV charge-discharge cycles at 0.1C (6.1mA) and 5V-7.2V to confirm the capacity retention rate. 【0145】 The capacity retention rate was calculated as the ratio of the discharge capacity in each cycle to the discharge capacity in the first discharge after formation, and the results are shown in Figure 4 below. 【0146】 Referring to Figure 4, it can be seen that the volume retention rate of Comparative Example 1 is significantly lower than that of Example 1, and that the volume retention rate of Example 1 is well maintained. 【0147】 Anyone with ordinary skill in the art to which this invention belongs can make various applications and modifications within the scope of this invention based on the above description. [Industrial applicability] 【0148】 The bipolar unit cell and bipolar battery according to the present invention have a structure in which the positive electrode active material is formed on the positive electrode current collector and the negative electrode active material is formed on the negative electrode current collector and bonded together. Compared to the conventional method in which these are formed on both sides of a single current collector, this structure can satisfy the required conditions. 【0149】 Furthermore, since each bipolar unit cell, which consists of the positive electrode, the negative electrode, and the separation membrane interposed between them, has a sealing section formed to connect the outer surfaces of the positive and negative electrodes and completely seal the interior, it not only effectively prevents electrolyte leakage compared to the case where a gasket is installed, but also prevents the loss of positive electrode active material and negative electrode active material, and has the effect of increasing capacity. 【0150】 Furthermore, although a separation space is formed between bipolar unit cells on the outer surface of the bipolar unit cell formed by the sealing portion, filling this space with a conductive layer prevents electrode warping and battery warping caused by the separation space, allows for uniform pressure to be applied when pressurized, and enables uniform current transmission between electrodes due to overall contact. This not only enhances the safety of the bipolar battery but also improves battery performance, such as lifespan characteristics.

Claims

[Claim 1] A laminate comprising a positive electrode current collector, a positive electrode material layer formed on one surface of the positive electrode current collector, a negative electrode current collector, a negative electrode material layer formed on one surface of the negative electrode current collector, and a separation membrane, wherein the positive electrode material layer and the negative electrode material layer are laminated facing each other with the separation membrane in between, It includes a sealing portion that adheres from the other surface of the positive electrode current collector to the other surface of the negative electrode current collector to form the laminate integrally and seal the inside, The internal space formed by the sealing portion contains a liquid electrolyte or a gel electrolyte. A bipolar unit cell in which a conductive layer is formed on the outside of at least one of the positive electrode current collector and the negative electrode current collector. [Claim 2] The bipolar unit cell according to claim 1, wherein the conductive layer has a thickness corresponding to the thickness in the stacking direction of the sealing portion attached to the other surfaces of the positive electrode current collector and the negative electrode current collector, respectively. [Claim 3] The bipolar unit cell according to claim 1, wherein the conductive layer is formed over an area of ​​90% to 100% of the area of ​​the other surface area of ​​the positive electrode current collector or the negative electrode current collector, excluding the area where the sealing portion is formed. [Claim 4] The bipolar unit cell according to claim 1, wherein the conductive layer is a conductive tape or a conductive sealant. [Claim 5] The bipolar unit cell according to claim 1, wherein the conductive layer comprises copper or carbon. [Claim 6] The bipolar unit cell according to claim 1, wherein the conductive layer further comprises an adhesive material. [Claim 7] The bipolar unit cell according to claim 6, wherein the adhesive substance comprises one or more from the group consisting of acrylic resins, phenolic resins, xylene resins, styrene resins, epoxy compounds, urethane resins, vinyl resins, and synthetic rubber. [Claim 8] The electronic conductivity of the conductive layer is 10 －１０ S / m ~ 10 －７ A bipolar unit cell according to claim 1, wherein the density is S / m. [Claim 9] The bipolar unit cell according to claim 1, wherein the sealing portion is a sealing tape or a curable sealant. [Claim 10] The bipolar unit cell according to claim 1, wherein the positive electrode current collector is an Al current collector and the negative electrode current collector is a Cu current collector. [Claim 11] A bipolar battery comprising two or more bipolar unit cells as described in claim 1, The aforementioned bipolar unit cell is constructed by stacking current collectors of opposite polarities facing each other. The bipolar battery has a separation space in the stacking direction due to a sealing portion formed on the outer frame of the bipolar unit cell. A bipolar battery in which a conductive layer is located in the aforementioned separation space. [Claim 12] The bipolar battery according to claim 11, wherein the conductive layer has a thickness corresponding to the distance of the separation space in the stacking direction.

Images