Manufacturing method for secondary battery

Abstract

A manufacturing method for a secondary battery of the present invention comprises the steps of: forming a stack cell by stacking a negative electrode material layer, a current collector, a positive electrode material layer, and a separator in a first direction, and sealing the side surfaces thereof by means of a sealing layer; pressing the stack cell in the first direction; and forming the sealing layer by providing heat to the stack cell in a second direction perpendicular to the first direction, wherein the sealing layer comprises a sealing resin.

Description

Method for manufacturing secondary batteries

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

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0105099, filed August 7, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for manufacturing a secondary battery, and more specifically, to a method for manufacturing a secondary battery including a sealing layer.

[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] Monopolar secondary batteries using monopolar electrodes have connections connecting the electrodes, and thus their output may be reduced due to the electrical resistance of the connections. In contrast, bipolar secondary batteries using bipolar electrodes have no connections and instead stack the electrodes, thereby minimizing the connection resistance of the electrodes.

[0007] Bipolar electrodes are formed by coating positive and negative active materials on both sides of a current collector with a current collector in between. Typically, when manufacturing a bipolar battery, separators and bipolar electrodes are alternately laminated, and both ends of the separator and bipolar electrodes are sealed with a sealing layer. The sealing layer can be formed by applying a sealing resin, but in the past, it was difficult to form the sealing layers with uniform adhesiveness and thickness during the hot forming step of the sealing layer. In particular, as the number of laminated unit cells increases, uniform forming of the sealing layer becomes more difficult. If the sealing layer is not formed uniformly, distortion of the sealing layer or electrolyte leakage may occur in the future, and problems with gas venting may also occur.

[0008] Therefore, it is necessary to develop a method for forming a sealing layer containing resin to have uniform adhesive strength and thickness during the manufacture of a bipolar battery.

[0009] The present invention aims to provide a method for manufacturing a bipolar battery having excellent stability and battery characteristics by providing uniform heat to each sealing layer of a unit cell in a bipolar battery to form a sealing layer having uniform adhesive strength and uniform thickness.

[0010] The method for manufacturing a secondary battery of the present invention comprises the steps of forming a stack cell by stacking a negative electrode material layer, a current collector, a positive electrode material layer, and a separator in a first direction and sealing their side surfaces with a sealing layer; pressing the stack cell in the first direction; and forming the sealing layer by providing heat to the stack cell in a second direction perpendicular to the first direction; wherein the sealing layer includes a sealing resin.

[0011] In one embodiment, the sealing resin may include at least one of polyimide (PI), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), acrylic resin, phenolic resin, xylene resin, styrene resin, epoxy compound, urethane resin, vinyl resin, and synthetic rubber.

[0012] In one embodiment, the step of forming the sealing layer may be such that the thickness of the sealing layer is compressed from a first thickness to a second thickness that is less than the first thickness.

[0013] In one embodiment, the negative electrode material layer and the positive electrode material layer may be provided in the form of bipolar electrodes coated on both sides of the current collector, respectively.

[0014] In one embodiment, the current collector may include a positive current collector and a negative current collector, the negative electrode material layer may be coated on one surface of the negative current collector, and the positive electrode material layer may be coated on one surface of the positive current collector.

[0015] In one embodiment, the heat may be transferred from the outside to the inside of the sealing layer.

[0016] In one embodiment, the heat is provided by a heat source, which may be provided non-contact to at least one side of the stack cell.

[0017] In one embodiment, the heat source may be provided on two opposite sides of the stack cell.

[0018] In one embodiment, in a press device including an upper plate, a lower plate facing the upper plate, and a column connecting the upper plate and the lower plate, the stack cell is accommodated in an internal space formed by the upper plate, the lower plate, and the column, and the step of pressing the stack cell in the first direction may be pressing the stack cell with the upper plate.

[0019] In one embodiment, the top plate may pressurize the entire upper surface of the stack cell on a plane.

[0020] In one embodiment, the upper plate may pressurize a portion of the upper surface of the stack cell where the sealing layer is located on a plane.

[0021] The method for manufacturing a secondary battery according to the present invention can be configured to form the sealing layers with uniform adhesive strength and thickness by transferring heat energy horizontally and uniformly to the sealing layers during hot forming. Accordingly, even when the secondary battery comprises multiple unit cells in multiple layers, the sealing layers can be uniformly formed, thereby providing a secondary battery with high stability and superior battery characteristics.

[0022] Figure 1 is a cross-sectional view of a unit cell according to one embodiment.

[0023] Figure 2 is a plan view of the unit cell illustrated in Figure 1.

[0024] Figure 3 illustrates one step of a method for manufacturing a secondary battery.

[0025] Figure 4 is a cross-sectional view of a bipolar electrode of one embodiment.

[0026] FIG. 5 is a perspective view of a press device of one embodiment shown in FIG. 3.

[0027] Fig. 6 is a perspective view of a press device according to another embodiment.

[0028] Fig. 7 illustrates one step of a method for manufacturing a secondary battery using the press device of Fig. 6.

[0029] Figure 8 illustrates one step of a method for manufacturing a secondary battery.

[0030] Hereinafter, various 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 invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0031] In this specification, in order to clearly explain the invention, parts that are not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0032] Furthermore, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to the illustrated components. In the drawings, the thicknesses are enlarged to clearly represent various layers and regions. Furthermore, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0033] Furthermore, when we say that a layer, membrane, region, plate, or other part is "on" or "over" another part, this includes not only cases where it is "directly on" the other part, but also cases where there are other parts in between. When we say that a part is "directly on" another part, we mean that there are no other parts in between. Furthermore, when we say that a part is "on" or "over" a reference part, we mean that it is located above or below the reference part, and we do not necessarily mean that it is located "above" or "over" the reference part in the opposite direction of gravity.

[0034] Additionally, throughout the specification, whenever a part is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0035]

[0036] unit cell

[0037] The method for manufacturing a battery cell of the present invention provides a battery cell including a unit cell.

[0038] Figure 1 is a cross-sectional view of a unit cell according to one embodiment.

[0039] Referring to FIG. 1, a unit cell (100) includes a first current collector (111), a negative electrode material layer (112) formed on one surface of the first current collector (111), a second current collector (121), a positive electrode material layer (122) formed on one surface of the second current collector (121), a separator (130), and a sealing layer (140).

[0040] The sealing layer (140) is formed by applying a sealing resin. Specifically, the sealing layer (140) seals between the first current collector (111) and the separator (130) and between the separator (130) and the second current collector (121) to form a partition structure. However, the embodiment of the sealing layer (140) is not limited thereto. In another embodiment, the sealing layer (140) may be formed in a form that covers the outer surfaces of the first current collector (111), the separator (130), and the second current collector (121) and surrounds the edges of the internal components.

[0041] Fig. 2 is a plan view of the unit cell illustrated in Fig. 1. In Fig. 2, a plan view of the unit cell with the first current collector (111) removed is illustrated in order to explain the sealing layer (140). Referring to Figs. 1 and 2 together, the sealing layer (140) may have a square ring shape and be formed on the outer surface of the unit cell (100). Meanwhile, the shape of the sealing layer (140) may be changed depending on the shape of the unit cell (100), and may have a circular ring shape, etc., without being limited to a square ring shape.

[0042] The sealing layer (140) of the present invention includes a sealing resin. The sealing resin may be any material that has good chemical resistance, strong adhesiveness, and is thermoformable, without limitation. For example, the sealing resin may include at least one of polyimide (PI), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), acrylic resin, phenol resin, xylene resin, styrene resin, epoxy compound, urethane resin, vinyl resin, and synthetic rubber.

[0043] In a later process, the space (SP) between the first and second collectors (111, 121), the separator (130), and the sealing layer (140) may be filled with an electrolyte.

[0044] Each of the first current collector (111) and the second current collector (121) is not particularly limited as long as it has conductivity without causing chemical changes in the battery.

[0045] For example, each of the first collector (111) and the second collector (121) may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or a material having its surface treated with carbon, nickel, titanium, silver, or the like.

[0046] Each of the first current collector (111) and the second current collector (121) may have a thickness of 3 μm to 500 μm, and may have fine unevenness formed on the surface to increase adhesion to the active material described later. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0047] Meanwhile, the unit cell (100) of one embodiment may be a bipolar unit cell. However, the embodiment of the present invention is not limited thereto, and the unit cell (100) may also be a monopolar battery cell.

[0048] When the unit cell (100) is a bipolar unit cell, the first current collector (111) and the second current collector (121) are the same current collectors containing the same material.

[0049] When the unit cell (100) is a monopolar unit cell, the first current collector (111) may be a negative current collector, and more specifically, a Cu current collector. Here, the Cu current collector is a concept that includes, in addition to being made of Cu, a metal material other than the impurity content. The second current collector (121) may be a positive current collector, and more specifically, an Al current collector. Here, the Al current collector is a concept that includes, in addition to being made of Al, a metal material other than the impurity content.

[0050] The cathode material layer (112) and the anode material layer (122) are laminated to face each other with the separator (130) in between.

[0051] The cathode material layer (122) may include a cathode active material, a binder, and further a conductive material.

[0052] The above positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and various combinations are possible, for example, lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-Z Ni Z O4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r)O2(wherein, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a1 Fe 1-x1 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, -0.5≤a1≤0.5, 0≤x1≤0.5, 0≤b1≤0.1), and any one or two or more compounds thereof may be included.

[0053] Specifically, it may include a lithium transition metal oxide represented by the following chemical formula 1, and specifically, 0.5≤x≤0.7, 0≤b≤0.1, and more specifically, LiNi 0.6 Co 0.1 Mn 0.3 May contain O2.

[0054] [Chemical Formula 1]

[0055] Li 1+a Ni x M 1-x O 2-b X b

[0056] 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.

[0057] 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), polytetrafluoroethylene (PTFE), 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.

[0058] 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 (122).

[0059] 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.

[0060] 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 above-mentioned positive electrode layer (122).

[0061] 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.

[0062] The negative electrode layer (112) may include a negative electrode active material, a binder, a conductive material, and other additives as described above.

[0063] 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, 및 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.

[0064] Descriptions of the binder, conductive material, and other additives in the cathode layer (112) are omitted because the same contents as described above in the anode layer (122) can be applied.

[0065] Meanwhile, the manufacturing method of the aforementioned positive electrode layer (122) and negative electrode layer (112) follows a general electrode manufacturing process. For example, each of the positive electrode layer (122) and negative electrode layer (112) may be prepared by mixing the aforementioned active material, binder, conductive material, etc. in a solvent to prepare a slurry, then coating the slurry on a current collector, drying, and rolling. At this time, the solvent may generally be an organic solvent or an aqueous solvent, and for example, as the organic solvent, one or a mixture of two or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), methoxy propyl acetate, butyl acetate, glycol acid, butyl ester, butyl glycol, methylalkylpolysiloxane, alkylbenzene, propylene glycol, xylene, monophenylglycol, aralkyl-modified methylalkylpolysiloxane, polyether-modified dimethylpolysiloxane copolymer, polyacrylate solution, alkylbenzene, diisobutyl ketone, organic-modified polysiloxane, butanol, isobutanol, modified polyacrylate, modified polyurethane, and polysiloxane-modified polymer may be preferably used. In addition, water may be used as the aqueous solvent.

[0066] Alternatively, the positive electrode material layer (122) and the negative electrode material layer (112) may each be electrode layers manufactured by a dry process. For example, the above-described active material, binder, conductive material, etc. may be mixed in a dry process without a separate solvent or additive to form a free-standing film, and the free-standing film may be attached and laminated on a current collector to form an electrode. The positive electrode material layer (122) or the negative electrode material layer (112) may be the free-standing film laminated on a current collector. Meanwhile, in a dry manufacturing process, polytetrafluoroethylene (PTFE) may be used as a binder.

[0067] 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.

[0068] For example, as the separator (130), a porous polymer film including a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a typical porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used as the separator. Alternatively, it may be an SRS (Safety Reinforced Separator) separator in which a coating layer including a binder and inorganic particles is formed on one or both sides of a polymer substrate as described above. The polyolefin substrate of the SRS separator may use the separator materials described above, and the coating layer includes inorganic particles and a binder. Here, the inorganic particles form micropores by enabling the formation of empty spaces between the inorganic particles, and also serve as a kind of spacer that can maintain the physical shape. In addition, since the physical properties of inorganic particles generally do not change even at high temperatures of 200℃ or higher, the formed organic-inorganic mixed layer has excellent heat resistance. The inorganic particles 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 applicable battery. In particular, when using inorganic particles with ion transfer capabilities, it is possible to improve performance by increasing the ionic conductivity within the electrochemical device, and therefore, it is preferable to have as high an ionic conductivity as possible. 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 have as low a density as possible.Furthermore, in the case of inorganic materials with high dielectric constants, they can contribute to increasing the degree of dissociation of electrolyte salts, such as lithium salts, within the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte. Finally, inorganic particles with thermal conductivity are even more desirable because their excellent heat absorption capacity suppresses the phenomenon of heat being concentrated locally, forming a hot spot and leading to thermal runaway.

[0069] For the reasons mentioned above, the inorganic particles are preferably at least one selected from the group consisting of (a) high-dielectric 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 transport capability.

[0070] Piezoelectricity refers to a material that is an insulator at normal pressure, but has the property of conducting electricity due to a change in its internal structure when a certain pressure is applied. It not only exhibits a high dielectric constant of 100 or more, but also has the function of generating a potential difference between the two sides when stretched or compressed by applying a certain pressure, so that one side becomes positively charged and the other side becomes negatively charged.

[0071] Examples of inorganic particles with 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, but are not limited thereto.

[0072] 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.

[0073] Examples of inorganic particles having lithium ion transport 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.

[0074] 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.

[0075] Thermally conductive inorganic particles are materials that have 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.

[0076] 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.

[0077] There is no limitation on the size of the inorganic particles, 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, the excessively large pore size may not function as a sufficient coating layer, increasing the probability of internal short circuits occurring during battery charging and discharging.

[0078] There is no particular limitation on the content of the inorganic particles, but it 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. If 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, if 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 deteriorating the mechanical properties of the coating layer.

[0079] 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 it can improve the mechanical properties of the final insulating film.

[0080] In addition, the binder does not necessarily need to have ion-conducting ability, but it is more preferable to use a polymer having ion-conducting ability.

[0081] Therefore, it is desirable for the binder to have a high dielectric constant, and since the degree of salt dissociation in the electrolyte actually depends on the dielectric constant of the electrolyte solvent, a higher dielectric constant of the polymer can improve the degree of salt dissociation in the electrolyte. The dielectric constant of the polymer can be 1 or more, specifically, a range of 1.0 to 100 (measurement frequency = 1 kHz), and a dielectric constant of 10 or more is particularly preferred.

[0082] 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 electrolyte swelling rate. In fact, if the binder is a polymer with excellent electrolyte swelling rate, the electrolyte injected after battery assembly will permeate into the polymer, and the polymer retaining the absorbed electrolyte will have electrolyte ion conductivity. Therefore, if possible, the solubility index should be between 15 and 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.

[0083] Examples of such binders include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, 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.

[0084] 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.

[0085]

[0086] The electrolyte may be a liquid electrolyte or a gel electrolyte.

[0087] The liquid electrolyte contains a lithium salt and a non-aqueous organic solvent.

[0088] Lithium salts can be used in the same or similar way as those commonly used in lithium secondary batteries. Lithium salts are used as a medium to transfer ions within 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

[0089] Specifically, lithium salts include LiCl, LiBr, LiI, LiBF4, LiClO4, and 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 LiN(SO2CF3)2 in terms of excellent stability.

[0090] The lithium salt can be appropriately changed within a normally usable range, but in order to obtain an optimal effect of forming a film for preventing corrosion on the electrode surface, it can be included in the electrolyte at a concentration of 0.5 M to 3 M, specifically, a concentration of 1 M to 2.5 M, and more specifically, a concentration of 1 M to 2 M. When the concentration of the lithium salt satisfies the 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.

[0091] The non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charge / discharge process 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.

[0092] 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.

[0093] 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.

[0094] The 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.

[0095] The ester organic solvent may include at least one selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0096] As a specific example of the linear ester organic solvent, 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 thereof may be representatively used, but is not limited thereto.

[0097] The 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.

[0098] Among 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 these 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 an appropriate ratio, an electrolyte having high electrical conductivity can be produced, and thus the compounds can be used more preferably.

[0099] Furthermore, the electrolyte may further include functional additives, and the functional additives 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.

[0100] 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.

[0101] The 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 electrolyte. When the content of the sultone-based compound in the 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.

[0102] The 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 electrolyte.

[0103] The 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 electrolyte.

[0104] Sulfate compounds include ethylene sulfate (Esa), trimethylenesulfate (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 electrolyte.

[0105] 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 electrolyte. If the content of the halogen-substituted carbonate compound in the electrolyte exceeds 5 wt%, cell swelling performance may deteriorate.

[0106] 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.

[0107] The 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 electrolyte exceeds 3 wt%, the cell swelling suppression performance may deteriorate.

[0108] The phosphate compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethylsilyl phosphate, trimethylsilyl 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 electrolyte.

[0109] The 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 electrolyte.

[0110] The lithium salt compound is a compound different from the lithium salt contained in the lithium non-aqueous electrolyte, and may include at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalatoborate (LiB(C2O4)2)) and LiBF4, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0111] Two or more functional additives may be mixed and included in an amount of 20 wt% or less, specifically 0.1 wt% to 10 wt%, based on the total weight of the 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 battery charging and discharging. In particular, since they are not 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.

[0112] The gel electrolyte comprises, in addition to a lithium salt and a non-aqueous organic solvent, at least one polymerizable compound selected from the group consisting of polymerizable monomers, oligomers, or copolymers having polymerizable unsaturated functional groups, wherein at least a portion of the polymerizable unsaturated functional groups may be cured.

[0113] A polymerizable compound of a 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-type electrolyte.

[0114] More specifically, the polymerizable monomer or oligomer includes, 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, 4-vinylcyclohexene Dioxide (4-vinylcyclohexenedioxide),Examples thereof include, but are not limited to, 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.

[0115] In addition, the copolymer may include at least one copolymer selected from the group consisting of, as representative examples, 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.

[0116] The polymer formed through the curing of the 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 polymer content 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.

[0117] Meanwhile, the gel-type 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 polymerizable monomers, oligomers, or polymers through free radical polymerization to form a gel-type electrolyte.

[0118] More specifically, examples of polymerization initiators 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.

[0119] The polymerization initiator can be decomposed by heat (non-limiting examples include 30°C to 100°C) within the bipolar unit cell or decomposed at room temperature (5°C to 30°C) to form radicals, which can react with polymerizable unsaturated functional groups of polymerizable monomers, oligomers, or polymers by free radical polymerization to form a gel-like electrolyte.

[0120] 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.

[0121] When the polymerization initiator is in the range of 0.01 to 20 parts by weight, the gel conversion rate can be increased to secure gel-type electrolyte properties, and the pre-gel reaction can be prevented to improve the wetting property of the electrolyte on the electrode.

[0122]

[0123] Method for manufacturing secondary batteries

[0124] Below, a method for manufacturing a secondary battery including the aforementioned unit cell is described.

[0125] In addition, the following describes an embodiment in which the unit cell (100) is a bipolar unit cell and the secondary battery is a bipolar battery including two or more bipolar unit cells (100).

[0126]

[0127] The method for manufacturing the secondary battery of the present invention is as follows:

[0128] A step of forming a stack cell by stacking a negative electrode material layer, a current collector, a positive electrode material layer, and a separator in a first direction and sealing the side surfaces thereof with a sealing layer;

[0129] a step of pressurizing the stack cell in the first direction; and

[0130] A step of forming the sealing layer by providing heat to the stack cell in a second direction perpendicular to the first direction;

[0131] The above sealing layer includes a sealing resin.

[0132]

[0133] A method for manufacturing a secondary battery of the present invention includes a step of forming a stack cell, a step of pressurizing the stack cell, and a step of forming a sealing layer.

[0134]

[0135] FIG. 3 illustrates one step of a method for manufacturing a secondary battery according to one embodiment.

[0136] Referring to FIG. 3, the step of forming a stack cell is a step of stacking a negative electrode layer, a current collector, a positive electrode layer, and a separator in a first direction while sealing their side surfaces with a sealing layer. In one embodiment, the negative electrode layer and the positive electrode layer may be provided in the form of bipolar electrodes coated on both sides of the current collector, respectively. The bipolar electrodes will be described with reference to FIG. 4.

[0137] Figure 4 is a cross-sectional view of a bipolar electrode of one embodiment.

[0138] Referring to FIG. 4, the bipolar electrode (150) includes a current collector (110) and a negative electrode material layer (112) and a positive electrode material layer (122) coated on both sides of the current collector (110). The current collector (110) may be the first current collector (111) or the second current collector (121) described above in the unit cell (100). When the unit cell (100) is a bipolar unit cell, the first current collector (111) and the second current collector (121) may be the same current collector including the same material. The description given above in the unit cell (100) also applies equally to the negative electrode material layer (112) and the positive electrode material layer (122).

[0139] Referring to FIGS. 3 and 4 together, the step of forming a stack cell is a step of alternately stacking bipolar electrodes (150) and separators (130) and sealing their side surfaces with a sealing layer (140). The sealing layer (140) seals and attaches the current collector (110) of the separator (130) and the bipolar electrode (150), which are positioned adjacent to each other, at both ends. In addition, the sealing layer (140) can prevent the flow and leakage of the electrolyte to be injected later.

[0140] In the present invention, the sealing layer (140) is formed by applying a sealing resin. The sealing resin includes a material that can be molded by heat. As described above in the unit cell (100, see FIG. 1), the sealing resin may include at least one of polyimide (PI), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), acrylic resin, phenol resin, xylene resin, styrene resin, epoxy compound, urethane resin, vinyl resin, and synthetic rubber.

[0141] By repeating these operations, a unit cell (100) is defined, and a stack cell (10) including two or more unit cells (100) is formed. The stack cell (10) may include two or more unit cells (100), for example, four or more, eight or more, or sixteen or more, and includes a plurality of unit cells (100).

[0142] Inside the stack cell (10), the negative electrode material layer (112) and the positive electrode material layer (122) are connected in series. The negative electrode material layer (112) and the positive electrode material layer (122) face each other with the separator (130) between them, and the negative electrode material layer (112) and the positive electrode material layer (122) face each other with the current collector (110) between them.

[0143] In addition, in the bipolar electrode (150) arranged on the outermost surface of the stack cell (10), the electrode material layer is formed only on one surface of the current collector (110), and the electrode material layer is omitted on the other surface. Specifically, the negative electrode material layer (112) is omitted on the lowermost surface of the stack cell (10), and the current collector (110) is arranged on the outside. The positive electrode material layer (122) is omitted on the uppermost surface of the stack cell (10), and the current collector (110) is arranged on the outside.

[0144]

[0145] After the step of forming the stack cell as described above, a step of pressurizing the stack cell is performed. In one embodiment, the stack cell can be pressed using the press device illustrated in FIG. 5.

[0146] FIG. 5 is a perspective view of a press device of one embodiment shown in FIG. 3.

[0147] Referring to FIG. 5, the press device (200) may include an upper plate (201), a lower plate (202) facing the upper plate (201), and a column (203) connecting the upper plate (201) and the lower plate (202).

[0148] Referring to FIGS. 3 and 5 together, the stack cell (10) is housed in an internal space formed by the upper plate (201), the lower plate (202), and the column (203).

[0149] The step of pressurizing the stack cell is a step of pressurizing the stack cell (10) in a first direction (DR1). Specifically, the entire upper surface of the stack cell (10) can be pressed by the upper plate (201). A uniform force can be applied to the entire inside of the stack cell (10) by the upper plate (201). Before pressurization is performed, the sealing layer (140) included in the unit cell (100) has a first thickness (t1), and the pressurization is provided in the first direction (DR1) which is the same as the thickness direction of the sealing layer (140).

[0150] Meanwhile, the press device (200) may include a gap guide (204). The gap guide (204) is installed in the column (203) and guides the height at which the upper plate (201) descends. One end of the gap guide (204) contacts the lower plate (202), and the other end of the gap guide (204) is located within the column (203). The length of the gap guide (204) is set to a length at which the stack cell (10) is compressed. The upper plate (201) can pressurize the stack cell (10) by descending to the other end of the gap guide (204).

[0151]

[0152] As described above, a step of forming a sealing layer is performed while pressurizing the stack cell.

[0153] The step of forming a sealing layer is a step of forming a sealing layer (140) by providing heat to the stack cell (10) in a second direction (DR2) perpendicular to the first direction (DR1).

[0154] Heat (HA) is provided by a heat source (300), and the heat source (300) can be provided in a non-contact manner to at least one side of the stack cell (10). In FIG. 3, an example in which the heat source (300) is provided to one side of the stack cell (10) is shown, but the heat source (300) can also be provided to two facing sides of the stack cell (10), and its location is not limited.

[0155] The heat source (300) according to one embodiment is a non-contact heating means, and may include, but is not limited to, an infrared heat source, an induction heating heat source, a laser heat source, a hot air heat source, an electromagnetic wave heat source, etc. depending on the heating method and principle.

[0156] An infrared heat source is a heating means that converts electrical energy into heat and transmits radiant heat to a heating target. Examples include, but are not limited to, a quartz tube heater, a carbon heater, a ceramic heater, and a halogen lamp.

[0157] An induction heating heat source is a heating means that generates heat in a heating object by generating an induced current through electromagnetic induction, and by the induced current. Examples of such sources include, but are not limited to, an induction heating coil.

[0158] Heat (HA) transfers heat energy at a uniform rate to the stack cell (10), and is particularly transferred to the sealing layer (140) located at the edge of the stack cell (10). The heat (HA) is transferred from the outside to the inside of the sealing layer (140) and heats the sealing layer (140) to a target temperature. Since the stack cell (10) is heated in a pressurized state, the sealing layer (140) heated to the target temperature can be easily rolled to the target thickness. In addition, the sealing layer (140) can have sufficient adhesive strength to the current collector (110) and the separator (130) through the heating step.

[0159] In the present invention, since the heat source (300) is provided to correspond to the side surface of the stack cell (10), heat (HA) can be uniformly transferred to the stacked sealing layers (140). Accordingly, even if the stack cell (10) includes a larger number of unit cells (100) than in the prior art, uniform heat (HA) can be transferred from the sealing layer (140) located at the lowest to the sealing layer (140) located at the uppermost. That is, the temperature deviation of the sealing layers (140) according to position is minimized, and the sealing layers (140) can be formed with a uniform thickness and uniform adhesive strength. Accordingly, structural distortion or leakage problems caused by uneven forming of the sealing layer, which occur in the prior art, can be prevented.

[0160]

[0161] Fig. 6 is a perspective view of a press device according to another embodiment.

[0162] Fig. 7 illustrates one step of a method for manufacturing a secondary battery using the press device of Fig. 6.

[0163] Referring to FIGS. 6 and 7 together, a press device (200-1) according to one embodiment may have a shape in which the upper plate (201-1) and the lower plate (202-1) are each separated.

[0164] For example, the upper plate (201-1) may include two rectangular plates positioned on the same plane and spaced apart from each other. The lower plate (202-1) may also have a shape corresponding to the upper plate (201-1). The upper plate (201-1) and the lower plate (202-1) may be positioned to overlap the sealing layer (140) on the plane. In addition, the shapes of the upper plate (201-1) and the lower plate (202-1) may be changed according to the purpose, and may have a square ring shape like the shape of the sealing layer (140) of FIG. 2.

[0165] Meanwhile, the description of other configurations in Fig. 7 applies equally to the content described above in Fig. 4.

[0166] Figure 8 illustrates one step of a method for manufacturing a secondary battery.

[0167] Figure 8 illustrates the completed sealing layer forming step.

[0168] Referring to Fig. 8, the upper plate (201) is lowered to a position where it contacts the gap guide (204), and the sealing layer (140) is formed to a target thickness. Specifically, the sealing layer (140) is compressed to a second thickness (t2) that is smaller than the first thickness (t1) before pressurization in Fig. 3.

[0169] In addition, as the sealing layer (140) is compressed to the second thickness (t2), the negative electrode material layer (112) and the separator (130) that face each other come into contact, and the separator (130) and the positive electrode material layer (122) that face each other come into contact. Accordingly, current can flow in series from the current collector (110) located on the upper side, through the bipolar electrode (150) and the separator (130), to the current collector (110) located on the other outer side.

[0170]

[0171] As described above, the method for manufacturing a secondary battery of the present invention includes the steps of forming a stack cell, pressurizing the stack cell in a vertical direction, and forming a sealing layer by heating the stack cell in a horizontal direction, thereby uniformly forming the sealing layer included in the stack cell, and each sealing layer having a uniform thickness and uniform adhesive strength, thereby providing a secondary battery having excellent stability and battery characteristics. In addition, the method for manufacturing a secondary battery of the present invention forms a sealing layer having a uniform thickness and uniform adhesive strength by heating the stack cell in a horizontal direction, even when the stack cell includes a plurality of unit cells, thereby providing a method for manufacturing a highly reliable secondary battery.

[0172]

[0173] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0174] [Explanation of symbols]

[0175] 100: Unit cell

[0176] 10: Stack Cell

[0177] 110: Whole house

[0178] 111: First House

[0179] 112: Cathode layer

[0180] 121: Second House

[0181] 122: Anode layer

[0182] 130: Membrane

[0183] 140: Ceiling layer

[0184] 150: Bipolar electrode

Claims

1. A step of forming a stack cell by stacking a negative electrode material layer, a current collector, a positive electrode material layer, and a separator in a first direction and sealing the side surfaces thereof with a sealing layer; a step of pressurizing the stack cell in the first direction; and A step of forming the sealing layer by providing heat to the stack cell in a second direction perpendicular to the first direction; A method for manufacturing a secondary battery, wherein the sealing layer includes a sealing resin.

2. In paragraph 1, A method for manufacturing a secondary battery, wherein the sealing resin comprises at least one of polyimide (PI), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), acrylic resin, phenol resin, xylene resin, styrene resin, epoxy compound, urethane resin, vinyl resin, and synthetic rubber.

3. In paragraph 1, A method for manufacturing a secondary battery, wherein the step of forming the sealing layer is such that the thickness of the sealing layer is compressed from a first thickness to a second thickness that is smaller than the first thickness.

4. In paragraph 1, A method for manufacturing a secondary battery, wherein the negative electrode layer and the positive electrode layer are provided in the form of bipolar electrodes coated on both sides of the current collector, respectively.

5. In paragraph 1, The above current collector includes a positive current collector and a negative current collector, A method for manufacturing a secondary battery, wherein the negative electrode material layer is coated on one surface of the negative electrode current collector, and the positive electrode material layer is coated on one surface of the positive electrode current collector.

6. In paragraph 1, A method for manufacturing a secondary battery, wherein the heat is transferred from the outside to the inside of the sealing layer.

7. In paragraph 1, A method for manufacturing a secondary battery, wherein the heat is provided by a heat source, and the heat source is provided non-contactly to at least one side of the stack cell.

8. In paragraph 7, A method for manufacturing a secondary battery, wherein the heat source is provided on two facing sides of the stack cell.

9. In paragraph 1, In a press device including an upper plate, a lower plate facing the upper plate, and a column connecting the upper plate and the lower plate, The stack cell is housed in an internal space formed by the upper plate, the lower plate, and the column, A method for manufacturing a secondary battery, wherein the step of pressing the stack cell in the first direction is to press the stack cell with the upper plate.

10. In paragraph 9, A method for manufacturing a secondary battery, wherein the upper plate presses the entire upper surface of the stack cell on a plane.

11. In paragraph 9, A method for manufacturing a secondary battery, wherein the upper plate presses a portion of the upper surface of the stack cell where the sealing layer is located on a plane.

Images