Bipolar unit cell, manufacturing method therefor, and bipolar battery comprising same

Abstract

According to one embodiment of the present invention, a bipolar unit cell, a manufacturing method therefor, and a bipolar battery structured as two or more stacked bipolar unit cells are provided, the bipolar unit cell comprising: a positive electrode including a positive electrode current collector and a positive electrode material layer, which is formed on one surface of the positive electrode current collector so that a positive electrode uncoated portion is formed on the edge thereof; a negative electrode including a negative electrode current collector and an negative electrode material layer, which is formed on one surface of the negative electrode current collector so that an negative electrode uncoated portion is formed on the edge thereof; and a separator, wherein the positive electrode material layer and the negative electrode material layer are stacked to face each other with the separator interposed therebetween, and at least one selected from the group consisting of the positive electrode material layer, the negative electrode material layer, and the separator contains a cured gel electrolyte.

Description

Bipolar unit cell, method for manufacturing the same, and bipolar battery including the same

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

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0053382, filed April 22, 2024, and Korean Patent Application No. 10-2025-0040685, filed March 28, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a bipolar unit cell, a method for manufacturing the same, and a bipolar battery including 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, secondary batteries using bipolar electrodes face challenges in increasing their capacity. Conventional bipolar electrodes are typically formed by coating both sides of a stainless steel current collector with positive and negative active materials, with the electrolyte structured to isolate the current collector from the two sides.

[0008] However, when stainless steel foil is repeatedly used for the current collector, there is a problem with durability, and since positive and negative active materials containing different materials are formed on both sides of the current collector, their flexibility is different, and there is a limit to controlling them even though the required conditions are different, and there is a problem that electrode contamination may occur when stored in the form of a roll electrode.

[0009] Furthermore, it is crucial for bipolar batteries using bipolar electrodes to prevent leakage of the electrolyte impregnated within them. Conventionally, gaskets were used to seal bipolar batteries, but these gaskets were difficult to manufacture with a thickness of less than 1 mm. If the gasket thickness was excessively large, the void space between the bipolar electrodes increased, resulting in a decrease in output power relative to volume.

[0010] Therefore, there is a need to develop a bipolar battery that can solve these problems while ensuring battery safety and improving performance.

[0011] The present invention aims to provide a bipolar unit cell and a bipolar battery that can solve the above problems of bipolar batteries, implement a bipolar battery through an easier process, and solve the electrolyte leakage problem.

[0012] In particular, the purpose is to provide a unit cell and a bipolar battery that can effectively solve the problem of electrolyte leakage without forming a sealing member.

[0013] According to one embodiment of the present invention, a cathode including a cathode current collector and a cathode material layer formed on one surface of the cathode current collector so that a cathode non-conductive portion is formed on the edge,

[0014] A negative electrode including a negative electrode current collector, and a negative electrode material layer formed on one surface of the negative electrode current collector so that a negative electrode non-conductive portion is formed on the edge, and a separator,

[0015] The above positive electrode material layer and the negative electrode material layer are laminated to face each other with a separator between them,

[0016] A bipolar unit cell is provided in which at least one selected from the group consisting of the positive electrode layer, the negative electrode layer, and the separator contains a cured gel electrolyte.

[0017] The positive electrode, the negative electrode, and the separator may be bonded to each other by the cured gel electrolyte.

[0018] A positive electrode insulating layer may be formed on the positive electrode non-conductive portion, and a negative electrode insulating layer may be formed on the negative electrode non-conductive portion. In addition, a conductive layer may be formed on at least one of the other surface of the positive electrode current collector and the other surface of the negative electrode current collector.

[0019] The conductive layer may be formed with an area of ​​90% to 100% of the exposed area of ​​the other surface of the positive electrode current collector or the other surface of the negative electrode current collector.

[0020] The conductive layer may be a conductive tape or conductive sealant containing copper or carbon.

[0021] It may further include a sealing member that seals the opening between the positive current collector and the negative current collector, wherein the sealing member may be formed on the inside of the opening between the positive current collector and the negative current collector, or may be a polymer film that connects the other surface of the positive current collector and the other surface of the negative current collector.

[0022] The above cathode material layer may be a dry cathode.

[0023] The above positive electrode current collector may be an Al current collector, and the above negative electrode current collector may be a Cu current collector.

[0024] Meanwhile, according to another embodiment of the present invention, as a method for manufacturing a bipolar unit cell,

[0025] (a) Form a positive electrode material layer on one side of a positive electrode current collector so that a positive electrode non-conductive area is formed on the edge, and form a negative electrode material layer on one side of a negative electrode current collector so that a negative electrode non-conductive area is formed on the edge to prepare a positive electrode and a negative electrode, and prepare a separator.

[0026] (b) impregnating a gel electrolyte composition into at least one selected from the group consisting of the positive electrode layer, the negative electrode layer, and the separator;

[0027] (c) A method for manufacturing a bipolar unit cell is provided, in which the anode and cathode are laminated with the separator interposed between them in a state where the anode and cathode material layers face each other, and then a gel electrolyte composition is cured.

[0028] The positive electrode, the negative electrode, and the separator may be bonded to each other and integrated by curing of the gel electrolyte.

[0029] In addition, in the above (b), when impregnating the gel electrolyte composition into the positive electrode material layer or the negative electrode material layer, it can be performed with a masking tape attached to at least one of the positive electrode non-coated portion and the negative electrode non-coated portion.

[0030] Furthermore, the above bipolar unit cell manufacturing method is,

[0031] The method may further include forming a positive electrode insulating layer on the positive electrode non-coated portion and forming a negative electrode insulating layer on the negative electrode non-coated portion. In addition, the method may further include forming a conductive layer on at least one of the other surface of the positive electrode current collector and the other surface of the negative electrode current collector.

[0032] In addition, after the above (c), it may further include sealing the opening between the positive electrode current collector and the negative electrode current collector with a sealing member.

[0033] The above positive electrode material layer may be formed by dry mixing a positive electrode active material, a conductive material, and a binder including a fibrous polymer, forming the mixture into a free-standing film, and then attaching the mixed mixture to one surface of the positive electrode current collector.

[0034] Furthermore, according to another embodiment of the present invention, a bipolar battery having a structure in which two or more bipolar unit cells are stacked is provided, wherein the bipolar unit cells are stacked so that current collectors of different polarities face each other.

[0035] At this time, a conductive layer is positioned between the two or more unit cells, and the bipolar unit cells may be bonded to each other by the conductive layer.

[0036] Among the bipolar unit cells above, electrode terminals may be formed on the outermost electrodes of the bipolar unit cells located at the outermost end.

[0037] FIG. 1 is a cross-sectional schematic diagram of a bipolar unit cell according to one embodiment of the present invention.

[0038] Figure 2 is a cross-sectional schematic diagram of a bipolar unit cell according to another embodiment of the present invention.

[0039] Figure 3 is a schematic diagram of the cathode material formation surface of the cathode in the bipolar unit cell of Figure 2.

[0040] Figure 4 is a cross-sectional schematic diagram of a bipolar unit cell according to another embodiment of the present invention.

[0041] Figure 5 is a cross-sectional schematic diagram of a bipolar unit cell according to another embodiment of the present invention.

[0042] Figure 6 is a schematic diagram of a method for manufacturing the bipolar unit cell of Figure 1.

[0043] Figure 7 is a cross-sectional schematic diagram of a bipolar battery according to one embodiment of the present invention.

[0044] Figure 8 is a cross-sectional schematic diagram of a bipolar battery according to another embodiment of the present invention.

[0045] Figure 9 is a formation graph of Example 1 according to Experimental Example 1.

[0046] Figure 10 is a charge / discharge graph of Example 1 according to Experimental Example 1.

[0047] Figure 11 is a charge-discharge comparison graph of Example 1 and Comparative Example 1 according to Experimental Example 2.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In this specification, "average particle diameter D50" means the particle size at 50% of the volume cumulative particle size distribution of the target particle powder (e.g., positive electrode active material powder, negative electrode active material powder, etc.). The average particle diameter D50 can be measured using a laser diffraction method. For example, the powder of the particles to be measured is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and then ultrasonic waves of about 28 kHz are irradiated at an output of 60 W, and then a volume cumulative particle size distribution graph is obtained, and then the particle size corresponding to 50% of the volume cumulative amount is measured.

[0053] 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.

[0054]

[0055] Bipolar unit cell and manufacturing method thereof

[0056] According to one embodiment of the present invention, a bipolar unit cell is provided.

[0057] FIG. 1 schematically illustrates a cross-sectional view of a bipolar unit cell (100) according to an embodiment of the present invention, FIG. 2 schematically illustrates a cross-sectional view of a bipolar unit cell (100) according to another embodiment of the present invention, and FIG. 3 illustrates a top view from the anode side of FIG. 2.

[0058] Referring to FIG. 1, a bipolar unit cell (100) comprises a positive electrode (110) including a positive electrode current collector (111), a positive electrode material layer (112) formed on one surface of the positive electrode current collector (111) such that a positive electrode non-conducting portion (111a) is formed on the edge, a negative electrode current collector (121), and a negative electrode (120) including a negative electrode material layer (122) formed on one surface of the negative electrode current collector (121) such that a negative electrode non-conducting portion (121a) is formed on the edge, and a separator (130), and is configured to have a structure in which the positive electrode material layer (112) and the negative electrode material layer (122) are laminated to face each other with the separator (130) interposed therebetween.

[0059] At this time, at least one selected from the group consisting of the positive electrode material layer (112), the negative electrode material layer (122), and the separator (130) contains a cured gel electrolyte (not shown), and more specifically, the positive electrode material layer (112), the negative electrode material layer (122), and the separator (130) may all contain a cured gel electrolyte (not shown) in a form in which sufficient impregnation with the electrolyte has occurred.

[0060] Such a bipolar unit cell (100) is manufactured by impregnating at least one selected from the group consisting of a cathode material layer (112), a cathode material layer (122), and a separator (130), specifically all of them, with a gel electrolyte composition, and then laminating the cathode (110) and the cathode (120) so that the separator (130) is interposed between them, and then curing the gel electrolyte composition. Therefore, after manufacturing, the cathode (110), the cathode (120), and the separator (130) are cured in a manner that connects them, and they are adhered to each other by the cured gel electrolyte. It is more preferable to impregnate all of these with the gel electrolyte composition from the beginning because complete impregnation is possible without electrolyte leakage.

[0061] To explain this structure in more detail, FIG. 6 schematically illustrates a method for manufacturing a bipolar unit cell (100) according to the present invention.

[0062] Referring to FIG. 6 together with FIG. 1, a positive electrode material layer (112) is formed on one surface of a positive electrode current collector (111) so that a positive electrode non-conductive portion is formed on the edge, and a negative electrode material layer (122) is formed on one surface of a negative electrode current collector (121) so that a negative electrode non-conductive portion is formed on the edge, thereby preparing a positive electrode (110) and a negative electrode (120), and a separator (130) is prepared (a).

[0063] Thereafter, at least one of the positive electrode layer (112), the negative electrode layer (122), and the separator (130) is impregnated with a gel electrolyte composition (153) (b).

[0064] At this time, the impregnation may be carried out by dropping the gel electrolyte composition (153) using a tool such as a dropper as shown in FIG. 6, but it may also be carried out by immersing the positive electrode (110), negative electrode (120), or separator (130) in a tank containing the gel electrolyte composition (153).

[0065] However, in the latter method, when impregnating the positive electrode material layer (112) or the negative electrode material layer (122), a large amount of gel electrolyte composition (153) may remain on the positive electrode current collector and the negative electrode current collector, which may affect contact properties or volume, and therefore, a method such as that in FIG. 6 may be preferred.

[0066] Meanwhile, in the case of performing the impregnation method using a device such as a dropper as in Fig. 6, the method is not limited thereto, but may be impregnated with the gel electrolyte composition (152, 151) while masking tapes (162, 161) are attached to the anode uncoated portion (111a) and the cathode uncoated portion (121a), respectively, so as to prevent the uncoated portions (111a) and (121a) of the anode (110) and the cathode (120) from being contaminated by the gel electrolyte compositions (151, 152).

[0067] In addition, although the drawing shows a shape in which some of the gel electrolyte compositions (151, 152, 153) are dropped, they are impregnated throughout the positive electrode layer (112), the negative electrode layer (122), and the separator (130) except for the locations where the masking tape is attached.

[0068] When impregnating the separator (130) with a gel electrolyte composition (153), there is no non-stick area, and masking tape may not be attached to impregnate the entire separator (130). However, in order to protect some of the liquid of the gel electrolyte contained in the separator (130) from leaking, masking tape may be attached to the edge portion of one side of the separator (130) excluding the size corresponding to the positive electrode (110) and the negative electrode (120) before impregnating the separator (130) with the gel electrolyte composition.

[0069] The above masking tapes (161, 162) can be removed after impregnation with the electrolyte composition.

[0070] Afterwards, a separator (130) is interposed between the anode (110) and cathode (120) with the anode material layer (112) and cathode material layer (122) facing each other and laminated, and then the gel electrolyte composition (151, 152, 153) is cured to manufacture a bipolar unit cell (100) (c). At this time, the anode (110), the cathode (120), and the separator (130) are bonded to each other and integrated by the curing of the gel electrolyte composition.

[0071] At this time, the curing of the gel electrolyte can be performed simultaneously with pressurization to ensure sufficient impregnation of the gel electrolyte composition (151, 152, 153) and a firm bond between the positive electrode (110), the negative electrode (120), and the separator (130), and can be performed using heat or light. In the case of the thermal curing, it can be performed at 50 to 90 degrees Celsius for 30 minutes to 24 hours. The light curing can be performed by irradiating with UV for 30 seconds to 30 minutes.

[0072] Therefore, according to the present invention, since the gel electrolyte plays a role in bonding the components, there is no need to add a separate adhesive material or perform a lamination process.

[0073] In addition, in this case, since the gel electrolyte is first manufactured and does not have fluidity after being hardened into a gel electrolyte, there is no problem of electrolyte leakage from each unit cell, and thus, as shown in Fig. 1, it is possible to operate as a bipolar battery without a sealing member, and the safety problem due to electrolyte leakage can be resolved.

[0074] Referring again to FIG. 1, the bipolar unit cell (100) is manufactured as a bipolar battery by stacking bipolar unit cells, and insulating layers (113, 123) may be formed on the non-conducting portions to prevent short circuits that may occur between the unit cells when they are driven.

[0075] Specifically, it has a structure in which an anode insulating layer (113) is formed on an anode non-conductive portion (111a), and a cathode insulating layer (123) is formed on an anode non-conductive portion (121a).

[0076] Here, the positive electrode insulating layer (113) and the negative electrode insulating layer (123) can be formed on the non-coated portion of the surface on which the positive electrode material layer (112) and the negative electrode material layer (122) are formed.

[0077] These insulating layers (113, 123) can be formed using various materials such as insulating coating layers and insulating tapes used in conventional secondary batteries, and are not limited thereto. For example, the insulating coating layer or insulating tape may be composed of a polymer or may contain a polymer and inorganic particles.

[0078] Therefore, short circuits between unit cells can be prevented by these insulating layers (113, 123). The thickness (t1) of the insulating layers (113, 123) can be 1 to 100 μm, and specifically, 1 to 20 μm.

[0079] Beyond the above range, forming it too thin is difficult in terms of process, and forming it too thick is not desirable because it reduces efficiency in the manufacturing process.

[0080] The process of forming these insulating layers (113, 123) is not separately illustrated in FIG. 6, but the insulating layers (113, 123) can be formed after process (c) in FIG. 6, and can be formed by a conventionally known method such as a process of coating, drying, etc., in the form of a simple attachment using a tape, and so called a coating layer. The method is not limited.

[0081] Here, the positive electrode current collector (111) is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. 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 other metal materials further included in the level of impurity content.

[0082] The positive electrode current collector (111) may have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to increase adhesion to the positive electrode active material layer. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0083] The cathode material layer (121) may include a cathode active material, a binder, and further a conductive material.

[0084] 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 Y2O2 (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 M x1 (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.

[0085] [Chemical Formula 1]

[0086] Li 1+a Ni x M 1-xO 2-b X b

[0087] 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.

[0088] Or more specifically, it may be lithium iron phosphate.

[0089] 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, 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.

[0090] 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 layer (112).

[0091] 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; 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.

[0092] The above-mentioned conductive material may be included in an amount of 0.1 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 layer (112).

[0093] 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.

[0094] Meanwhile, the positive electrode (110) may be a wet positive electrode manufactured through a process of mixing the positive electrode active material, conductive material, and binder as described above in a solvent to manufacture a slurry, and then coating, drying, and rolling, or may be a dry positive electrode manufactured in the absence of a solvent.

[0095] When the positive electrode (110) is a dry positive electrode, the positive electrode material layer (112) can be manufactured as a dry free-standing film. Specifically, it can be manufactured by dry-mixing a binder including a fibrous polymer together with the positive electrode active material and conductive material as described above, and molding the result into a free-standing film.

[0096] Here, the fiberizing binder may be polytetrafluoroethylene (PTFE). Since this fiberizing binder is fiberized by shearing, a dry freestanding film can be manufactured by mixing the positive electrode active material, conductive material, and binder and performing shearing without a separate solvent.

[0097] At this time, the fiber binder may be included in an amount of 50% by weight or more, and may be 100% by weight, based on the total weight of the binder.

[0098] After forming into a dry free-standing film in this way, the positive electrode (110) can be manufactured by attaching it to one surface of the positive electrode current collector.

[0099] When the positive electrode (110) is manufactured dry compared to the wet method, the uniformity of electrode loading is improved, the adhesive strength is increased, and edges and drag lines that appear in the wet manufacturing process are alleviated, thereby improving electrode quality. In addition, a high-loading electrode can be implemented, so the dry positive electrode can be used more preferably.

[0100] 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, the concept includes including other metal materials further included in the level of impurity content.

[0101] The negative electrode current collector (121) can typically have a thickness of 3 ㎛ to 500 ㎛, and, like the positive electrode current collector, can have fine irregularities formed on the surface of the negative electrode current collector to enhance the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0102] The negative electrode layer (122) may include a negative electrode active material, a binder, a conductive material, and other additives as described above.

[0103] 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, 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.

[0104] The negative electrode (120) may also be a wet negative electrode manufactured through a process of mixing the above-described negative electrode active material, conductive material, and binder in a solvent to manufacture a slurry, followed by coating, drying, and rolling. However, it may also be a dry negative electrode manufactured in the absence of a solvent, and the present invention is not limited thereto. The dry negative electrode may also be manufactured using a binder containing a fibrous polymer, and the method is similar to that described for the dry positive electrode.

[0105] The separator (130) 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 moisture retention capacity.

[0106] For example, 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 as the separator (130). 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 separator.

[0107] Alternatively, it may be a Safety Reinforced Separator (SRS) membrane having a coating layer including a binder and inorganic particles formed on one or both sides of a polymer substrate as described above.

[0108] 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.

[0109] Here, the inorganic particles play a dual role: they form micropores by allowing the formation of empty spaces 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] The above thermally conductive inorganic particles are materials 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), and beryllium oxide (BeO), but are not limited thereto.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] The total thickness of the separation membrane (130) may be 5 micrometers to 20 micrometers, specifically 5 micrometers to 15 micrometers, and more specifically 6 micrometers to 13 micrometers.

[0127] 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, wherein at least a portion of the polymerizable unsaturated functional group may be cured.

[0128] 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.

[0129] 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

[0130] 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.

[0131] 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.

[0132] The above non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during subsequent charge / discharge processes of the bipolar battery and can exhibit the desired properties together with additives. For example, carbonate-based organic solvents, ether-based organic solvents, or ester-based organic solvents can be used alone or in combination of two or more, and specifically, carbonate-based organic solvents can be used.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] The polymerizable compound of the above polymerizable monomer, oligomer or copolymer 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 producing a conventional gel electrolyte.

[0154] 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.

[0155] 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.

[0156] The polymer formed through the curing of the above materials may be included in an amount of 0.01 wt% to 10 wt% based on the total weight of the gel electrolyte. If the content of the polymer exceeds 10 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] Meanwhile, FIG. 2 shows a cross-sectional schematic diagram of a bipolar unit cell (100') according to another embodiment, and FIG. 3 shows a schematic diagram of the upper surface of the cathode (120') side of the bipolar unit cell (100').

[0163] Referring to FIGS. 2 and 3, the bipolar unit cell (100') is configured to include, as described in FIG. 1, a positive electrode (110') including a positive electrode current collector (111'), a positive electrode material layer (112') formed on one surface of the positive electrode current collector (111') such that a positive electrode non-coated portion (111'a) is formed on the edge, a negative electrode current collector (121'), and a negative electrode (120') including a negative electrode material layer (122') formed on one surface of the negative electrode current collector (121') such that a negative electrode non-coated portion (121'a) is formed on the edge, and a separator (130'), and the positive electrode material layer (112') and the negative electrode material layer (122') are laminated to face each other with the separator (130') therebetween.

[0164] At this time, at least one selected from the group consisting of a positive electrode layer (112'), a negative electrode layer (122'), and a separator (130') contains a cured gel electrolyte (not shown).

[0165] In addition, the bipolar unit cell (100') has a structure in which an anode insulating layer (113') is formed on the anode non-conductive portion (111'a) on the side where the anode material layer (112') is formed, and a cathode insulating layer (123') is formed on the cathode non-conductive portion (121'a) on the side where the cathode material layer (122') is formed.

[0166] Above, the specific details of the bipolar unit cell (100') are as described above.

[0167] Meanwhile, the bipolar unit cell (100') may further have conductive layers (141, 142) formed on the other surface of the positive electrode current collector (111') and the other surface of the negative electrode current collector (121') in addition to the bipolar unit cell (100) of FIG. 1.

[0168] The drawing discloses a structure formed on both sides, but at least one of them may have a conductive layer formed on it.

[0169] Here, conductive layers (141, 142) can be formed for subsequent adhesion between bipolar unit cells.

[0170] Meanwhile, the formation area of ​​the conductive layers (141, 142) may be formed specifically in an area of ​​60% to 100%, specifically 90% to 100%, of the area exposed on the other surface of the positive electrode current collector (111') and the other surface of the negative electrode current collector (121').

[0171] The thickness (t2) of these conductive layers (141, 142) may be 1 to 100 μm, and more specifically, 1 to 20 μm.

[0172] Beyond the above range, it is difficult to form it too thinly in terms of process, and if it is formed too thickly, the current transfer speed becomes slow or the overall volume increases, which is not desirable.

[0173] These conductive layers (141, 142) may be conductive tapes or conductive sealants. That is, they may be formed as tapes or formed as sealant layers.

[0174] Here, the conductive tape may be a copper tape or a carbon tape containing copper or carbon, which are conductive materials.

[0175] When conductive layers (141, 142) in tape form are formed in this way, the process is easy.

[0176] Additionally, the conductive sealant may include conductive particles and an adhesive material.

[0177] At this time, the conductive particle is not limited to a particle having conductivity, and may be, for example, a material such as carbon or a metal, and specifically, may be carbon such as carbon black, carbon nanotubes, or graphene, or a metal such as copper, aluminum, platinum, silver, titanium, or nickel. More specifically, it may include copper particles or carbon particles.

[0178] Here, the average particle diameter (D50) of the above-mentioned challenging particles may be 300 nm to 10 μm, and specifically, 300 nm to 2 μm.

[0179] If it is too large outside the above range, it is difficult to easily control the thickness of the conductive layers (141, 142), and if it is too small, there is a problem that the conductive path becomes long.

[0180] The above adhesive material may include at least one member selected from the group consisting of acrylic resin, phenol resin, xylene resin, styrene resin, and epoxy compound, and more specifically, may be an epoxy compound.

[0181] These conductive layers (141, 142) should enable even transfer of current between the positive and negative electrodes as described above, and depending on this transfer, the performance of the bipolar battery is affected. Therefore, the electronic conductivity of the conductive layers (141, 142) may be 1 S / m to 1 GS / m, specifically 10 S / m to 100 MS / m, and more specifically 100 S / m to 100 MS / m.

[0182] Having an electronic conductivity within the above range is desirable for battery performance, and if it is lower than the above range, sufficient conductivity cannot be obtained, and it is not easy to manufacture a conductive layer having a conductivity higher than the above range.

[0183] These conductive layers (141, 142) also, although the formation process thereof is not separately illustrated in FIG. 6, can be formed after process (c) in FIG. 6, and if it is a tape, it can be formed by a simple attachment method, and if it is a coating layer, it can be formed by a conventionally known method such as a coating or drying process. The method is not limited.

[0184] Furthermore, FIGS. 4 and 5 each show cross-sectional schematic diagrams of bipolar unit cells (100'', 100''') according to another embodiment.

[0185] Referring to FIGS. 4 and 5, the bipolar unit cell (100'', 100''') may further include sealing members (151, 152, 151', 152') that seal the opening between the positive electrode collector and the negative electrode collector, compared to the bipolar unit cell (100') of FIG. 2.

[0186] Here, the sealing members (151, 152, 151', 152') are formed on the inside of the opening between the positive electrode current collector and the negative electrode current collector, as shown in FIG. 4, to separate the gel electrolyte impregnated in at least one of the positive electrode material layer, the negative electrode material layer, and the separator from other bipolar unit cells to prevent leakage, or, as shown in FIG. 5, a polymer film that connects the other surface of the positive electrode current collector and the other surface of the negative electrode current collector can be applied to separate the gel electrolyte.

[0187] At this time, the shape of the sealing member is not limited as long as it is in a form that can separate the gel electrolyte contained in one bipolar unit cell from the gel electrolyte contained in another bipolar unit cell so that they are not mixed.

[0188] Meanwhile, when forming the conductive layer described above, since the conductive layer has a constant thickness, it is more preferable that the sealing member be formed with a thickness corresponding to the conductive layer as in Fig. 5, and from this, the formation of the conductive layer or the formation of the sealing member can offset each other without a thickness deviation due to the formation of the conductive layer or the sealing member, thereby providing a more solid structure.

[0189] The process of forming these sealing members (151, 152, 151', 152') is not separately illustrated in FIG. 5, but they can be formed after process (c) in FIG. 5, and the method is not limited.

[0190] Such sealing members may include, for example, one or more materials selected from the group consisting of polypropylene, polypropylene with inorganic fillers, polyphthalamide, polyethylene, polyurethane, general-purpose plastics, thermoplastic olefin rubber, polyamide-based synthetic resins, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyethylene naphthalate, and silicone rubber.

[0191] Specifically, the sealing member may have a three-layer structure in which thermoplastic resin films are positioned on both sides and a thermosetting resin film is positioned between them. This structure is most preferable because the adhesive strength is enhanced by the thermoplastic resin and the film shape retention is enhanced by the thermosetting resin.

[0192]

[0193] bipolar battery

[0194] According to another embodiment of the present invention, a bipolar battery including two or more of the bipolar unit cells is provided.

[0195] Figures 7 and 8 schematically illustrate cross-sectional views of these bipolar cells (1000, 1000'').

[0196] First, referring to FIG. 7, a bipolar battery (1000) is configured with a structure in which two or more bipolar unit cells (100, 200, 300) are stacked so that current collectors of different polarities face each other.

[0197] Specifically, the positive current collector (111) of the bipolar unit cell (100) and the negative current collector (221) of the bipolar unit cell (200) are stacked so that they face each other, and the bipolar unit cell (200) and the bipolar unit cell (300) are also stacked so that current collectors of different polarities face each other. Therefore, a flow of current can be obtained by contacting them, etc.

[0198] In addition, as pointed out in the description of the bipolar unit cell (100) of FIG. 1, the bipolar unit cells (100, 200, 300) of the present invention may have insulating layers (representatively, 113, 123) formed on one surface of the non-conductive portions of the current collector.

[0199] Specifically, an insulating layer (113) is formed on one surface where the positive electrode material layer and the negative electrode material layer are formed at the edge portion of each of the positive electrode current collector (111) and the negative electrode current collector (221).

[0200] Meanwhile, conductive layers (142) may be formed between each bipolar unit cell (100, 200, 300).

[0201] A bipolar battery (1000) manufactured in this manner may have a positive electrode tab (301) formed on a positive electrode current collector so that one of the bipolar unit cells located at the outermost end among the stacked bipolar unit cells can be electrically withdrawn to the outside by connecting a positive electrode lead, and another may have a negative electrode tab (101) formed on a negative electrode current collector so that the negative electrode lead can be electrically withdrawn to the outside by connecting a negative electrode lead. From this, it may be a structure in which charging and discharging are performed by electrical connection.

[0202] Furthermore, referring to FIG. 8, the bipolar battery (1000'') of FIG. 8 is identical to the bipolar battery (1000) of FIG. 7, except that it has a structure in which a sealing member is formed in each of the bipolar unit cells (100'', 200'', 300'') as in FIG. 4.

[0203]

[0204] Hereinafter, examples will be described to demonstrate that the present invention exhibits the intended improved effects.

[0205]

[0206] <Example 1>

[0207] As a cathode active material, LiNi 0.8 Co 0.05 Mn 0.1 Al 0.05 O2, carbon nanotubes as a conductive agent, and PVDF as a binder were dispersed in an NMP solvent at a weight ratio of 98:1:1, and the cathode slurry was coated on one side of an Al metal thin film, leaving a border, to a thickness of 60 micrometers, dried, and rolled to manufacture the cathode.

[0208] 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, leaving a border thereon, to a thickness of 70 micrometers, dried, and rolled to manufacture a negative electrode.

[0209] As a separator, a CCS separator (thickness: 13 micrometers) with an organic-inorganic mixed layer (Al2O3: PVdF = 95:5) formed on both sides of a polyolefin substrate was used.

[0210] 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.

[0211] After attaching masking tape to the edges of each of the positive and negative electrodes, the gel electrolyte composition was impregnated into the positive and negative electrodes. At this time, vacuum was applied and released five times, and then the excess residual gel electrolyte composition remaining on the surface was removed. Similarly, the separator was also impregnated with the gel electrolyte composition. The positive electrode impregnated with the gel electrolyte composition and the negative electrode impregnated with the gel electrolyte composition were laminated with the separator impregnated with the gel electrolyte composition interposed therebetween, and then pressed and heat-cured (65 degrees Celsius, 600 minutes) to manufacture a unit cell. After preparing two unit cells manufactured in this way, a conductive adhesive (carbon sealant) was applied (2 μm) to the other surface of the Cu metal film of the negative electrode of one unit cell, and then the other surface of the Al metal film of the positive electrode of the other unit cell was laminated to face each other, thereby manufacturing a semi-solid bipolar cell.

[0212]

[0213] <Example 2>

[0214] A semi-solid bipolar cell was manufactured as in Example 1 above, and a non-porous PE film (polyethylene, thickness 20 ㎛) with a porosity of 20% was attached to the Al metal thin film and the edge of the Cu metal thin film of the semi-solid bipolar cell to seal it.

[0215]

[0216] Experimental Example 1

[0217] To confirm whether the semi-solid bipolar cells manufactured in Examples 1 and 2 above operate normally, they were formed by charging at 0.02C (1.22mA) and 7.2V cut-off, and after degassing, CC-CV charging and discharging were performed at 0.1C (6.1mA) and 5V-8.4V.

[0218] As a result, the graphs are shown in Figures 6 and 7 below.

[0219] Referring to FIGS. 9 and 10, it was confirmed that the formation was expressed at normal capacity, and in both cases, the initial capacity was similar at approximately 61.09 mAh and the initial efficiency was similar at approximately 83.5% in one charge / discharge cycle.

[0220]

[0221] <Comparative Example 1>

[0222] An electrode assembly was manufactured by interposing a separator (thickness: 13 micrometers) coated with a mixture composition of Al2O3:PVDF (95:5 weight ratio) on a polyolefin material substrate between the two positive electrodes manufactured in Example 1 and the double-sided negative electrode, and then storing this in a pouch battery case, and then injecting the gel electrolyte composition of Example 1 and impregnating it by repeating vacuum application and release five times, and then thermally curing (65 degrees Celsius, 600 minutes) to manufacture a semi-solid secondary battery.

[0223] The above semi-solid secondary battery was formed by charging it at 0.02C (1.22mA) and 4.2V cut-off, and then degassing was performed.

[0224]

[0225] Experimental Example 2

[0226] CC-CV charging and discharging was performed at 0.1 C on the semi-solid bipolar cells of Examples 1 and 2 and the semi-solid secondary battery of Comparative Example 1, which performed formation and degassing, and the graph thereof is shown in FIG. 11 below, and the results obtained therefrom are shown in Table 1 below.

[0227] Example 1 / Example 2Comparative Example 1Capacity (mAh) 61120Operating voltage range (V) 5-8.4V 2.5-4.2V

[0228] Referring to Table 1 above and FIG. 11 below, when manufactured as a bipolar cell as in Examples 1 and 2 of the present invention, it can be confirmed that it operates well in the form of a high-voltage cell with a small capacity while maintaining similar coulombic efficiency and voltage profile behavior compared to the manufacturing method of a general lithium secondary battery.

[0229] 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.

[0230] The bipolar unit cell and bipolar battery according to the present invention have a structure in which a positive electrode active material is formed and bonded to a positive electrode current collector and a negative electrode active material is formed and bonded to a negative electrode current collector, and thus, compared to the conventional structure in which the positive electrode active material is formed on both sides of a single current collector, each of the required conditions can be satisfied.

[0231] In addition, by pre-impregnating at least one of the positive and negative electrodes, or a separator interposed therebetween, with a gel electrolyte and then laminating and curing the components of the bipolar unit cell, the bipolar battery can be operated without a separate lamination process or sealing member.

[0232] Of course, the problem of electrolyte leakage can be effectively prevented by further increasing the sealing force, including the sealing member.

[0233] Moreover, when an insulating layer is formed on the non-conductive portion of the positive and negative electrodes, a short circuit between the positive and negative electrodes can be prevented.

[0234] Furthermore, when a conductive layer is formed between two or more unit cells and bonded to each other, the bipolar unit cells can be firmly bonded, thereby increasing the safety of the bipolar battery.

Claims

1. A positive electrode including a positive electrode current collector and a positive electrode material layer formed on one surface of the positive electrode current collector so that a positive electrode non-conductive portion is formed on the edge, A negative electrode including a negative electrode current collector, and a negative electrode material layer formed on one surface of the negative electrode current collector so that a negative electrode non-conductive portion is formed on the edge, and Contains a separator, The above positive electrode material layer and the negative electrode material layer are laminated to face each other with a separator between them, A bipolar unit cell comprising a cured gel electrolyte in at least one selected from the group consisting of the positive electrode layer, the negative electrode layer, and the separator.

2. In paragraph 1, A bipolar unit cell in which the positive electrode, the negative electrode, and the separator are bonded to each other by the cured gel electrolyte.

3. In paragraph 1, A bipolar unit cell in which an anode insulating layer is formed on the anode non-conductive portion and a cathode insulating layer is formed on the cathode non-conductive portion.

4. In paragraph 1, A bipolar unit cell in which a conductive layer is formed on at least one of the other surfaces of the positive electrode current collector and the other surfaces of the negative electrode current collector.

5. In paragraph 4, A bipolar unit cell in which the conductive layer is formed with an area of ​​90% to 100% of the exposed area of ​​the other surface of the positive electrode current collector or the other surface of the negative electrode current collector.

6. In paragraph 4, The above conductive layer is a bipolar unit cell which is a conductive tape or conductive sealant containing copper or carbon.

7. In paragraph 1, A bipolar unit cell further comprising a sealing member that seals an opening between the positive electrode collector and the negative electrode collector.

8. In paragraph 7, A bipolar unit cell in which the sealing member is a polymer film formed on the inside of an opening between the positive electrode current collector and the negative electrode current collector, or which connects the other surface of the positive electrode current collector and the other surface of the negative electrode current collector.

9. In paragraph 1, The above cathode material layer is a bipolar unit cell which is a dry cathode.

10. In paragraph 1, A bipolar unit cell in which the positive electrode current collector is an Al current collector and the negative electrode current collector is a Cu current collector.

11. A method for manufacturing a bipolar unit cell according to paragraph 1, (a) Form a positive electrode material layer on one side of a positive electrode current collector so that a positive electrode non-conductive area is formed on the edge, and form a negative electrode material layer on one side of a negative electrode current collector so that a negative electrode non-conductive area is formed on the edge to prepare a positive electrode and a negative electrode, and prepare a separator. (b) impregnating a gel electrolyte composition into at least one selected from the group consisting of the positive electrode layer, the negative electrode layer, and the separator; (c) A method for manufacturing a bipolar unit cell, wherein the separator is interposed between the anode and cathode while the anode material layer and the cathode material layer face each other, and then the gel electrolyte composition is cured.

12. In paragraph 11, A method for manufacturing a bipolar unit cell, wherein the positive electrode, the negative electrode, and the separator are bonded to each other and integrated by curing the gel electrolyte.

13. In paragraph 11, In the above (b), a method for manufacturing a bipolar unit cell is performed while attaching masking tape to at least one of the positive electrode non-conductive part and the negative electrode non-conductive part when impregnating the gel electrolyte composition into the positive electrode material layer or the negative electrode material layer.

14. In paragraph 11, The above bipolar unit cell manufacturing method is, A method for manufacturing a bipolar unit cell further comprising forming an anode insulating layer on the anode non-conductive portion and forming a cathode insulating layer on the cathode non-conductive portion.

15. In paragraph 11, The above bipolar unit cell manufacturing method is, A method for manufacturing a bipolar unit cell further comprising forming a conductive layer on at least one of the other surface of the positive electrode current collector and the other surface of the negative electrode current collector.

16. In paragraph 11, A method for manufacturing a bipolar unit cell further comprising, after the above (c), sealing an opening between the positive electrode collector and the negative electrode collector with a sealing member.

17. In paragraph 11, A method for manufacturing a bipolar unit cell, wherein the above-mentioned positive electrode material layer is formed by dry mixing a positive electrode active material, a conductive material, and a binder including a fibrous polymer, forming the same into a free-standing film form, and then attaching it to one surface of the positive electrode current collector.

18. A bipolar battery having a structure in which two or more bipolar unit cells according to any one of claims 1 to 10 are stacked, The above bipolar unit cells are bipolar batteries in which current collectors of different polarities are stacked so that they face each other.

19. In paragraph 18, A bipolar battery in which a conductive layer is positioned between the two or more unit cells, and the bipolar unit cells are bonded to each other by the conductive layer.

20. In paragraph 18, A bipolar battery in which electrode terminals are formed on each of the outermost electrodes of the bipolar unit cells located at the outermost portion among the above bipolar unit cells.

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