Method for manufacturing secondary battery

Abstract

A method for manufacturing a secondary battery according to the present invention comprises the steps of: providing a slurry containing an active material; applying the slurry to a substrate and drying and rolling to form an electrode layer having a first thickness; preparing an electrolyte; applying the electrolyte to the electrode layer; measuring the time required for the electrolyte to pass through the electrode layer and appear on the substrate after being dropped onto the electrode layer; and determining whether to apply the electrolyte in consideration of the required time when forming the electrode layer having a first thickness on a current collector using the slurry and applying and curing the electrolyte.

Description

Method for manufacturing a secondary battery

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

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0130867 filed September 26, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] The present invention relates to a method for manufacturing a secondary battery, and more specifically, to a method for manufacturing a secondary battery that measures the time during which an electrolyte is impregnated into an electrode and reflects this in a production manufacturing process.

[0004] In modern society, as the use of portable devices such as mobile phones, laptops, camcorders, and digital cameras has become commonplace, the development of technologies related to such mobile devices is becoming active. Furthermore, rechargeable secondary batteries are being utilized as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (P-HEVs) as a solution to address air pollution caused by conventional gasoline vehicles using fossil fuels; consequently, the need for the development of secondary batteries is increasing.

[0005] Currently commercialized rechargeable batteries include nickel-cadmium, nickel-hydrogen, nickel-zinc, and lithium batteries. Among these, lithium batteries are receiving the most attention due to their advantages of free charging and discharging, low self-discharge rate, and high energy density.

[0006] These secondary batteries are manufactured by impregnating an electrode assembly, comprising a positive electrode, a negative electrode, and a separator, with an electrolyte. For excellent battery performance to be realized, the electrode assembly must be sufficiently impregnated with the electrolyte. Furthermore, with the recent research into high-capacity and high-output secondary batteries, it is crucial that the electrolyte rapidly impregnates the electrode assembly during manufacturing. This is because if the impregnation rate of the electrolyte is poor, it fails to reach the active material particles on the electrode plates, hindering the smooth movement of lithium ions and consequently reducing the current. Additionally, a decrease in the electrolyte impregnation rate lowers the productivity of the secondary battery.

[0007] Therefore, a method capable of accurately evaluating the impregnation of the electrolyte is required, and in particular, a method for evaluating electrolyte impregnation that reflects the structure in which the electrolyte is impregnated into the actual electrode is necessary. Conventionally, a method was used in which the electrode assembly was housed in a battery case, such as a pouch or can, and then the electrolyte was injected into the battery case to achieve impregnation. However, recently, methods for manufacturing secondary batteries have been developed in which the electrolyte is impregnated by coating it onto the electrode assembly rather than injecting it. Therefore, it is necessary to develop an electrolyte impregnation evaluation method that reflects this battery manufacturing method.

[0008] The problem that the present invention aims to solve is to provide a method for manufacturing a secondary battery that reflects a method for manufacturing a secondary battery in which an electrolyte is applied to, impregnated into, and cured on an electrode, evaluates the impregnation properties of the electrolyte in advance, and provides a method for manufacturing a secondary battery that reflects this.

[0009] However, the problems that the embodiments of the present invention aim to solve are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention.

[0010] The method for manufacturing a secondary battery according to the present invention comprises: a step of providing a slurry containing an active material; a step of applying the slurry onto a substrate and drying and rolling to form an electrode layer having a first thickness; a step of preparing an electrolyte; a step of applying the electrolyte to the electrode layer; a step of measuring the time required from the point in time when the electrolyte is dropped onto the electrode layer until the time in time when the electrolyte passes through the electrode layer and appears on the substrate; and a step of determining whether to apply the electrolyte by considering the time required when forming the electrode layer having the first thickness with the slurry on a current collector and applying and curing the electrolyte.

[0011] In one embodiment, the determining step may be a step of determining to apply the electrolyte if the required time is within 30 minutes, and determining not to apply the electrolyte if the required time exceeds 30 minutes.

[0012] In one embodiment, when it is determined to apply the electrolyte in the step of determining whether to apply the electrolyte, the method may further include: forming the electrode layer having the first thickness with the slurry on the current collector; applying the electrolyte on the electrode layer; waiting for the required time; and curing the electrode layer on which the electrolyte has been applied.

[0013] In one embodiment, the step of measuring the required time may further include the step of calculating the impregnation rate of the electrolyte using the following Equation 1:

[0014] [Equation 1]

[0015] Impregnation rate (㎛ / sec) = Electrode layer thickness (㎛) / Time required (sec).

[0016] In one embodiment, the substrate may be a transparent substrate.

[0017] In one embodiment, the substrate may comprise polypropylene (PP) or polyethylene (PE).

[0018] In one embodiment, the step of applying the electrolyte to the electrode layer may include the step of rolling the surface of the electrode layer with a roller.

[0019] In one embodiment, the curing step may utilize UV ​​curing or thermal curing.

[0020] In one embodiment, the electrolyte may be non-volatile.

[0021] In one embodiment, the electrolyte may be a liquid electrolyte.

[0022] In one embodiment, the slurry may include an anode active material, a binder, and a conductive material.

[0023] In one embodiment, the slurry may include a negative electrode active material, a binder, and a conductive material.

[0024] In one embodiment, the first thickness may be 10 μm or more and 1000 μm or less.

[0025] According to the embodiments, the method for manufacturing a secondary battery of the present invention can improve productivity by evaluating the impregnation of the electrolyte by reflecting the structure in which the actual electrolyte is impregnated into the electrode and applying this to the process.

[0026] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0027] FIG. 1 is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0028] FIG. 2 illustrates the step of applying an electrolyte to an electrode layer according to one embodiment of the present invention.

[0029] FIG. 3 illustrates the step of applying an electrolyte to an electrode layer according to one embodiment of the present invention.

[0030] FIG. 4 illustrates the step of applying an electrolyte to an electrode layer according to one embodiment of the present invention.

[0031] FIG. 5 illustrates the step of applying an electrolyte to an electrode layer according to one embodiment of the present invention.

[0032] FIG. 6 illustrates the step of curing the electrode layer coated with an electrolyte according to one embodiment of the present invention.

[0033] Hereinafter, various embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms other than those described below, and the scope of the present invention is not limited by the embodiments described herein.

[0034] To clearly explain the present invention, parts unrelated to the description have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0035] In addition, the size and thickness of each component shown in the drawings have been arbitrarily enlarged or reduced for convenience of explanation, so it is obvious that the content of the present invention is not limited to what is illustrated. In the drawings below, the thickness of each layer has been enlarged to clearly represent various layers and regions. Also, in the drawings below, the thickness of some layers and regions has been exaggerated for convenience of explanation.

[0036] Furthermore, when describing a part such as a layer, membrane, region, or plate as being "above" or "on" another part, this should be interpreted to include not only cases where the corresponding part is "directly above" the other part, but also cases where there is another part in between. Conversely, when describing a corresponding part such as a layer, membrane, region, or plate as being "directly above" another part, it may mean that there is no other part in between. Additionally, stating that a part is "above" or "on" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" or "on" in the opposite direction of gravity. Meanwhile, just as describing a part as being "above" or "on" another part can be understood by referring to the aforementioned content, describing a part as being "below" or "under" another part can also be understood.

[0037] Furthermore, throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0038] Additionally, the term “impregnation degree” as used in the specification refers to the extent to which the electrolyte penetrates into the electrode layer, and may have the same meaning as terms such as impregnation, wetting, impregnation rate, absorption, and absorption rate.

[0039]

[0040] Hereinafter, a method for manufacturing a secondary battery according to one embodiment of the present invention will be described.

[0041]

[0042] The method for manufacturing a secondary battery according to the present invention is,

[0043] A step of providing a slurry containing an active material;

[0044] A step of applying the above slurry onto a substrate and drying and rolling to form an electrode layer having a first thickness;

[0045] Step of manufacturing the electrolyte;

[0046] A step of applying the electrolyte to the electrode layer;

[0047] A step of measuring the time taken from the point in time when the electrolyte is applied to the electrode layer until the point in time when the electrolyte passes through the electrode layer and appears on the substrate; and

[0048] When forming an electrode layer having the first thickness with the slurry on the current collector and applying and curing the electrolyte, the method includes a step of determining whether to apply the electrolyte by considering the required time.

[0049]

[0050] The method for manufacturing a secondary battery in the present invention includes a method for manufacturing a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery, etc.

[0051] Conventionally, secondary batteries were manufactured by inserting an electrode assembly into a case having a specific size and shape and injecting an electrolyte into the case.

[0052] However, in the present invention, the secondary battery can be manufactured by producing an electrode assembly comprising a positive electrode, a negative electrode, and a separator, and then directly applying and impregnating an electrolyte onto the electrode assembly and curing it. Reflecting this process, in the method for manufacturing the secondary battery of the present invention, in order to evaluate the degree of electrolyte impregnation in advance, the electrolyte impregnation ability was evaluated in the same manner as the method of impregnating the electrolyte into the electrode.

[0053] In addition, the electrode assembly used in the secondary battery includes electrodes such as a positive electrode or a negative electrode, and the electrodes can be classified into a monopolar electrode in which an active material having the same polarity is coated on both sides of a current collector, and a bipolar electrode in which an active material having different polarities is coated on both sides of a current collector.

[0054] A bipolar electrode is formed by coating a positive active material on one side of a current collector and a negative active material on the other side of the current collector, with a current collector in between. Generally, when manufacturing a bipolar battery, a separator and a bipolar electrode are alternately stacked, and both ends of the separator and the bipolar electrode are sealed with a sealing layer. In one embodiment, for an electrode assembly to which a bipolar electrode is applied, a secondary battery can be manufactured by using a method in which an electrolyte is directly applied to the electrode of the electrode assembly to impregnate it, and then cured. In particular, in a bipolar battery, the electrolyte can be impregnated from the positive electrode to the current collector or from the negative electrode to the current collector.

[0055] Accordingly, the present application has invented a method for manufacturing an electrode and a substrate corresponding to an electrode and a current collector, and then directly applying an electrolyte to the electrode at the semi-finished product level and evaluating the impregnation of the electrolyte.

[0056] FIG. 1 is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0057] Referring to FIG. 1, a method for manufacturing a secondary battery according to one embodiment includes the steps of providing a slurry (S100), forming an electrode layer (S200), preparing an electrolyte (S300), applying the electrolyte to the electrode layer (S400), measuring the time required (S500), and determining whether to apply the electrolyte (S600).

[0058]

[0059] Specifically, the step of providing a slurry (S100) is a step of providing a slurry containing an active material. The slurry may be a slurry for a secondary battery electrode, and may be a slurry for a positive electrode or a slurry for a negative electrode.

[0060] A slurry can be prepared by mixing an active material, a binder, and a conductive material in a solvent. The active material may be a positive active material or a negative active material.

[0061] As a positive electrode active material, compounds known in the industry that are capable of reversible intercalation and deintercalation of lithium may be used without limitation.

[0062] Specifically, the positive electrode active material may be a lithium complex metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium.

[0063] Specifically, examples of lithium complex metal oxides include lithium-iron-phosphorus oxides (e.g., Li 1+a Fe 1-s M s (PO 4-b )X b (wherein M is one or more elements selected from Co, Ni, Al, Mg, Ti, and V, X is F, S, or N, -0.5≤a≤+0.5, 0≤b≤0.1, 0≤s≤0.5) etc.), 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 Y1O2(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 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(where, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 Examples include )O2(wherein M is one or more selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are each atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.

[0064] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; one or more carbon-based materials selected from the group consisting of carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon; Si-based materials; LixFe2O3 (0≤x≤1), LixWO2 (0≤x≤1), and Sn x Me 1-x Me y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements 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 사용할 수 있지만, 당 업계에 알려진 것이라면 이들만으로 한정되는 것은 아니다.

[0065] A binder is used to enhance the bonding between the active material and the conductive material, as well as the bonding to the current collector described later.

[0066] Non-limiting examples of binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethyl methacrylate (PMMA), polyacrylamide (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof.

[0067] Conductive materials are used to further improve the conductivity of the active material. Conductive materials are not particularly limited as long as they have electrical conductivity without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; carbon-based materials such as carbon fibers, single-walled carbon nanotubes, or multi-walled carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, or silver; conductive fibers; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives may be used.

[0068] Generally, an organic solvent or an aqueous solvent may be used as the solvent. For example, as an organic solvent, one or more mixtures selected from the group consisting of N-methyl-2-pyrrolidone (NMP), methoxypropyl acetate, butyl acetate, glycol acid, butyl ester, butyl glycol, methylalkylpolysiloxane, alkylbenzene, propylene glycol, xylene, monophenyl glycol, aralkyl-modified methylalkylpolysiloxane, polyether-modified dimethylpolysiloxane copolymer, polyether-modified dimethylpolysiloxane copolymer, polyacrylate solution, alkylbenzene, diisobutylketone, organic-modified polysiloxane, butanol, isobutanol, modified polyacrylate, modified polyurethane, and polysiloxane-modified polymer may be preferably used. Additionally, water may be used as the aqueous solvent.

[0069] In addition, the slurry may include other additives, for example, a filler as a component to inhibit expansion, or may further include a dispersant to increase the dispersion efficiency of the conductive material. The filler and dispersant may be used without particular restriction as long as they are commonly used in slurries for secondary battery electrodes.

[0070]

[0071] Next, the steps of forming an electrode layer (S200), preparing an electrolyte (S300), and applying the electrolyte to the electrode layer (S400) are performed.

[0072] The step of forming an electrode layer (S200) is to apply the aforementioned slurry onto a substrate and to form an electrode layer by drying and rolling.

[0073] The drying and rolling steps can be carried out under the same conditions as the actual electrode manufacturing process. For example, the drying step can be performed by vacuum drying for 1 to 24 hours at a temperature range of 50 ℃ to 120 ℃ for the anode, and for 2 to 48 hours at a temperature range of 60 ℃ to 150 ℃ for the cathode. The rolling step can be carried out by applying a pressure of 10 MPa to 100 MPa, specifically 20 MPa to 60 MPa, at a temperature range of 0 ℃ to 120 ℃.

[0074] Additionally, the rolling step may be performed considering the porosity of the actual electrode. The electrode layer after rolling may have a porosity of 18 volume% to 30 volume% and a density of 1 g / cc to 4.5 g / cc. For example, if the slurry contains a positive electrode active material, the electrode layer may have a porosity of 18 volume% to 30 volume% and a density of 3.4 g / cc to 4.2 g / cc. Or, if the slurry contains a negative electrode active material, the electrode layer may have a porosity of 20 volume% to 30 volume% and a density of 1.3 g / cc to 1.8 g / cc. However, the conditions of the drying and rolling steps are not limited thereto.

[0075] The step of manufacturing the electrolyte (S300) may be a step of manufacturing a liquid electrolyte, and specifically, a liquid electrolyte comprising an organic solvent and a lithium salt may be manufactured.

[0076] As long as the organic solvent can serve as a medium for the movement of ions involved in the electrochemical reaction of the battery, it may be used without specific restrictions; however, it is preferable to use a non-volatile solvent.

[0077] Lithium salts can be used without special restrictions as long as they are compounds capable of providing lithium ions used in lithium secondary batteries. Lithium salts are used as a medium for ion transfer within lithium batteries; for example, Li as a cation + It includes, and as anion, 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 can be cited.

[0078] The step of applying an electrolyte to the electrode layer (S400) is the step of applying an electrolyte to the electrode layer prepared above.

[0079] FIGS. 2 and FIGS. 3 illustrate the step of applying an electrolyte to an electrode layer according to one embodiment of the present invention.

[0080] Referring to FIG. 2, the aforementioned slurry is applied onto a substrate (20), dried, and rolled to form an electrode layer (10). The electrode layer (10) can be manufactured considering the thickness of the electrode actually manufactured in the process. The thickness (LL1) of the electrode layer (10) may be a first thickness, and the first thickness may be 10 μm or more and 1000 μm or less, and preferably 10 μm or more and 200 μm or less, but the embodiments are not limited thereto.

[0081] The electrolyte (30) is applied to the upper surface of the electrode layer (10). The amount of the applied electrolyte (30) may be 1 µl or more, for example, 1 µl to 10 µl, specifically 1 µl to 5 µl. If the electrolyte (30) is dropped in an amount less than 1 µl, it may be difficult to observe the time when the electrolyte (30) arrives. Even if the amount of the electrolyte (30) dropped exceeds 10 µl, it does not significantly affect the electrolyte impregnation time.

[0082] Referring to FIG. 3, the step (S400) of applying an electrolyte onto an electrode layer may include the step of rolling the surface of the electrode layer (10) with a roller (40). By rolling the electrode layer (10) with the roller (40), the applied electrolyte (30, see FIG. 2) can be evenly dispersed on the surface of the electrode layer (10). Specifically, the entire surface of the electrode layer (10) may be rolled about 1 to 3 times with the roller (40). In addition, the pressure intensity of the roller (40) is not particularly limited and can be adjusted according to the physical properties of the electrode layer. However, the step of rolling the surface of the electrode layer (10) with the roller (40) may be omitted.

[0083] When the electrolyte (30) is applied, a step (S500) for measuring the time required is performed.

[0084] The step of measuring the time required (S500) is a step of measuring the time required from the point in time when the electrolyte (30) is dropped onto the electrode layer (10) until the point in time when the electrolyte (30) passes through the electrode layer (10) and appears on the substrate (20).

[0085] The step of measuring the required time (S500) can be performed by visual inspection or measurement. Here, the expression "visual inspection or measurement" includes directly checking with the eyes of an observer or indirectly checking through a medium between the object of analysis and the observer, such as a lens, camera, microscope, etc.

[0086] In order to allow visual confirmation or measurement of the electrolyte (30) passing through the electrode layer (10) and appearing on the substrate (20), the substrate (20) may be made of a transparent material. Additionally, the substrate (20) is preferably made of a material capable of withstanding the pressure applied during the rolling step of the electrode layer (10). For example, the substrate (20) may include polypropylene (PP) or polyethylene (PE), but the embodiments are not limited thereto.

[0087] Meanwhile, the step of measuring the required time (S500) may further include the step of calculating the impregnation rate of the electrolyte (30) using the following Equation 1.

[0088] [Equation 1]

[0089] Impregnation rate (㎛ / sec) = Electrode layer thickness (㎛) / Time required (sec).

[0090]

[0091] Afterwards, a step (S600) for determining whether to apply the electrolyte is performed.

[0092] The step of determining whether to apply the electrolyte (S600) is a step of evaluating the impregnation of the electrolyte (30) and determining whether to use the electrolyte (30) in the actual process.

[0093] Specifically, in an actual process, when forming an electrode layer having the first thickness with the slurry on the current collector and applying and curing the electrolyte, the decision to apply the electrolyte can be made by considering the time required measured above. In another embodiment, the impregnation rate calculated in Equation 1 can be considered instead of the time required.

[0094] Specifically, the step (S600) of determining whether to apply the electrolyte is a step of deciding to apply the electrolyte if the time required is within 30 minutes, and deciding not to apply the electrolyte if the time required exceeds 30 minutes. Specifically, the time required may be within 60 seconds to 30 minutes. The time required may vary depending on whether the aforementioned roller (40) is used or the pressure intensity of the roller (40). If the time required exceeds 30 minutes, there is a risk of degradation of the electrolyte.

[0095] Since the method for manufacturing a secondary battery of the present invention performs a process of curing after applying an electrolyte to an electrode, it is preferable that the time for the electrolyte to be impregnated be within 30 minutes, and the time required in the semi-finished product state can be measured in advance to determine whether to use the electrolyte.

[0096] In addition, in the step (S600) of determining whether to apply the electrolyte, the time required for the electrolyte is measured in advance and compared by electrolyte or by electrode, and the result may be applied to the design of the electrode (porosity, electrode structure).

[0097] The method for manufacturing a secondary battery according to the present invention may further include a step of proceeding with an actual process when it is determined to apply an electrolyte in the step (S600) of determining whether to apply an electrolyte.

[0098] Specifically, when it is decided to apply an electrolyte, the method for manufacturing a secondary battery of the present invention may further include the steps of forming an electrode layer on a current collector, applying an electrolyte on the electrode layer, waiting for a required time, and curing the electrode layer on which the electrolyte is applied. The step of curing the electrode layer on which the electrolyte is applied is a step not only to impregnate the electrolyte onto the electrode layer but also to prevent the electrolyte from migrating to other places. In the curing step, the state of the electrolyte changes from liquid to gel.

[0099] FIGS. 4 and 5 illustrate the step of applying an electrolyte to an electrode layer according to one embodiment of the present invention.

[0100] Referring to FIG. 4, the step of forming an electrode layer on a current collector is to form an electrode layer (100) on a current collector (200) using the slurry used in FIG. 2. The thickness (LL2) of the electrode layer (100) formed on the current collector (200) has a first thickness equal to the thickness (LL1) of the electrode layer (10) formed on the substrate (20) in FIG. 2.

[0101] Meanwhile, the current collector (200) is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, a surface treated with carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, an aluminum-cadmium alloy, etc. may be used. In addition, the thickness of the current collector (200) may be 3㎛ or more and 50㎛ or less, and preferably 10㎛ or more and 20㎛ or less. The current collector (200) may have various forms such as, for example, a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, etc.

[0102] The step of applying an electrolyte on the electrode layer is the step of applying the electrolyte (30) used in FIG. 2 onto the electrode layer (100).

[0103] Referring to FIG. 5, the step of applying an electrolyte onto an electrode layer may include the step of rolling the surface of the electrode layer (100) with a roller (40). By rolling the electrode layer (100) with the roller (40), the applied electrolyte (30, see FIG. 4) can be evenly dispersed on the surface of the electrode layer (10). Specifically, the entire surface of the electrode layer (100) may be rolled about 1 to 3 times with the roller (40). However, the step of rolling the surface of the electrode layer (100) with the roller (40) may be omitted. Specifically, it may be carried out or omitted in the same way as the rolling step in the aforementioned step of applying an electrolyte onto an electrode layer (S400).

[0104] Afterward, a waiting stage is performed for the required time. The required time is the time measured in the step (S500) for measuring the required time. During the required time, the electrolyte (30) passes through the electrode layer (100) and reaches the current collector (200), and the electrode layer (100) is completely impregnated.

[0105] Subsequently, a step of curing the electrode layer coated with the electrolyte is carried out.

[0106] FIG. 6 illustrates the step of curing the electrode layer coated with an electrolyte according to one embodiment of the present invention.

[0107] Referring to FIGS. 4 and FIGS. 6 together, after the required time has elapsed, a step of curing the electrode layer (100) coated with the electrolyte (30) is performed. The curing (50) can be performed by thermal curing or UV curing. Conventionally, after injecting the electrolyte into a battery case containing an electrode assembly, it was stored for 2 to 3 days for impregnation. However, in the present invention, it takes less than 60 seconds for the electrolyte (30) to impregnate the electrode (100), and the manufacture of the battery can be completed through subsequent curing (50). As such, in the method for manufacturing a secondary battery of the present invention, since curing proceeds after the electrolyte (30) is applied and impregnated into the electrode layer (100), it is important to accurately measure the time required for the impregnation of the electrolyte (30) in order to design the curing time.

[0108]

[0109] The method for manufacturing a secondary battery according to the present invention reflects the structure of applying, impregnating, and curing an electrolyte onto an electrode during the actual manufacturing of a secondary battery. By directly applying the electrolyte to the electrode in a semi-finished state, the impregnation time of the electrolyte can be measured and the impregnation properties of the electrolyte can be evaluated. Furthermore, by evaluating the impregnation properties of the electrolyte in advance, the composition or structure of the electrode layer can be designed to select the electrolyte and ensure an appropriate time. Accordingly, the method for manufacturing a secondary battery according to the present invention can improve reliability and productivity.

[0110]

[0111] Although 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 by those skilled in the art using the basic concept of the present invention as defined in the following claims are also included within the scope of the present invention.

[0112] [Explanation of the symbol]

[0113] 10: Electrode layer

[0114] 20: Substrate

[0115] 30: Electrolyte

[0116] 100: Electrode layer

[0117] 200: Whole house

[0118] 40: Roller

[0119] 50: Hardening

Claims

1. A step of providing a slurry containing an active material; A step of applying the above slurry onto a substrate and drying and rolling to form an electrode layer having a first thickness; Step of manufacturing the electrolyte; A step of applying the electrolyte to the electrode layer; A step of measuring the time taken from the point in time when the electrolyte is applied to the electrode layer until the point in time when the electrolyte passes through the electrode layer and appears on the substrate; and A method for manufacturing a secondary battery comprising: a step of determining whether to apply the electrolyte by considering the required time when forming the electrode layer having the first thickness with the slurry on the current collector and applying and curing the electrolyte.

2. In Paragraph 1, A method for manufacturing a secondary battery, wherein the above-mentioned determining step is a step of determining to apply the electrolyte if the above-mentioned time is within 30 minutes, and determining not to apply the electrolyte if the above-mentioned time exceeds 30 minutes.

3. In Paragraph 1, If it is decided to apply the electrolyte in the step of determining whether to apply the electrolyte, A step of forming the electrode layer having the first thickness on the current collector using the slurry; A step of applying the electrolyte onto the electrode layer; A step of waiting for the above required time; and A method for manufacturing a secondary battery, further comprising the step of curing the electrode layer coated with the above electrolyte.

4. In Paragraph 1, A method for manufacturing a secondary battery, wherein the step of measuring the required time further includes the step of calculating the impregnation rate of the electrolyte using the following Equation 1: [Equation 1] Impregnation rate (㎛ / sec) = Electrode layer thickness (㎛) / Time required (sec).

5. In Paragraph 1, A method for manufacturing a secondary battery in which the above substrate is a transparent substrate.

6. In Paragraph 1, A method for manufacturing a secondary battery in which the substrate comprises polypropylene (PP) or polyethylene (PE).

7. In Paragraph 1, A method for manufacturing a secondary battery, wherein the step of applying the electrolyte to the electrode layer includes the step of rolling the surface of the electrode layer with a roller.

8. In Paragraph 3, A method for manufacturing a secondary battery in which the above-mentioned curing step utilizes UV curing or thermal curing.

9. In Paragraph 1, A method for manufacturing a secondary battery in which the above electrolyte is non-volatile.

10. In Paragraph 1, A method for manufacturing a secondary battery in which the above electrolyte is a liquid electrolyte.

11. In Paragraph 1, A method for manufacturing a secondary battery in which the above slurry comprises a positive electrode active material, a binder, and a conductive material.

12. In Paragraph 1, A method for manufacturing a secondary battery in which the above slurry comprises a negative electrode active material, a binder, and a conductive material.

13. In Paragraph 1, A method for manufacturing a secondary battery in which the first thickness is 10 μm or more and 1000 μm or less.

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