Method for manufacturing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery manufactured by the same

Abstract

According to the method for manufacturing a secondary battery of the present invention, a liquid electrolyte is uniformly impregnated into the battery and then gelled. This allows a secondary battery to be manufactured with a uniformly impregnated and uniformly distributed gel polymer electrolyte. Furthermore, compared to batteries using liquid electrolytes, gel polymer secondary batteries manufactured by the method for manufacturing a secondary battery of the present invention do not leak electrolyte, and have excellent heat resistance, safety, and durability. In addition, since the electrolyte is uniformly distributed inside the battery, the battery exhibits uniform electrochemical characteristics.

Description

[Technical field]

[0001] This application claims priority based on Korean Patent Application No. 10-2021-0135234, filed on October 12, 2021. The present invention relates to a method for manufacturing a lithium secondary battery including a gel polymer electrolyte and a gel polymer electrolyte secondary battery manufactured thereby. [Background technology]

[0002] In recent years, interest in energy storage technology has been increasing. In particular, as the fields of application expand to include mobile phones, video cameras, and laptops, and even the energy of electric vehicles, research and development of electrochemical elements is becoming more concrete. Electrochemical elements are the field that has attracted the most attention in the field of energy storage technology, and among them, interest in secondary batteries that can be charged and discharged is on the rise.

[0003] Among the secondary batteries currently in use, lithium secondary batteries, developed in the early 1990s, have been attracting attention due to the advantages of a high operating voltage and a significantly higher energy density compared to conventional batteries (conventional batteries) that use aqueous electrolytes, such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries.

[0004] This type of lithium secondary battery is divided into lithium ion batteries using a liquid electrolyte and lithium polymer batteries using a polymer electrolyte, depending on the dedicated electrolyte.

[0005] Lithium ion batteries have the advantage of high capacity, but they have the disadvantage that they use a liquid electrolyte containing lithium salt, which means there is a risk of leakage and explosion, and battery design becomes complicated in order to deal with this.

[0006] Meanwhile, lithium polymer batteries use solid polymer electrolytes or gel polymer electrolytes containing electrolyte, which improves safety and flexibility. This allows them to be developed in various forms, such as small or thin-film batteries. Gel polymer electrolytes are divided into coating type and injection type, depending on the manufacturing method. Injection type gel polymer electrolytes can be manufactured by injecting a liquid electrolyte containing a crosslinking monomer into a cell, wetting the electrode assembly uniformly with the liquid electrolyte, and then performing a crosslinking process. During the crosslinking process, the electrolyte forms a matrix and changes into a gel electrolyte with no fluidity.

[0007] On the other hand, after injecting the liquid electrolyte, it is necessary to carry out a crosslinking process after the electrolyte is sufficiently and uniformly impregnated into the battery. This is because if the electrolyte gels before reaching a uniform impregnation state, the gel polymer electrolyte may be distributed non-uniformly inside the battery. When manufacturing a liquid electrolyte battery, after injecting the electrolyte into the battery, an aging process is carried out in which the electrolyte is left under vacuum conditions for a predetermined time, and the electrolyte is uniformly impregnated into the battery. However, if a vacuum aging process is applied during the manufacture of a gel polymer electrolyte battery, the oxygen concentration is reduced and a crosslinking reaction is initiated. For this reason, the electrolyte may gel before reaching a uniform impregnation state. This limits the application of the aging process, making it difficult to ensure the same level of impregnation as a liquid electrolyte battery. For this reason, when manufacturing a gel polymer battery, it is necessary to develop a manufacturing process that ensures uniform impregnation of the battery by the gel polymer electrolyte. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide an effective method for manufacturing a secondary battery containing a gel polymer electrolyte, in which the gel polymer electrolyte is uniformly impregnated and distributed in the battery. Another aim of the present invention is to provide a secondary battery in which the gel polymer electrolyte is uniformly distributed in the battery. It will be easily understood that other objects and advantages of the present invention can be achieved by the means or methods set forth in the claims, and combinations thereof. [Means for solving the problem]

[0009] The first aspect of the present invention is A step (S1) of manufacturing a spare battery by housing the electrode assembly and a first electrolytic solution containing an organic solvent and a polymerizable compound in a battery exterior material; A step (S2) of leaving the spare battery for a predetermined time; Injecting a second electrolyte solution containing an organic solvent and a crosslinking agent into the reserve battery (S3); and (S4) leaving the result of the step (S3) at a temperature of 50 to 80° C. for a predetermined period of time, wherein the first electrolyte does not contain a crosslinking agent.

[0010] In a second aspect of the present invention, in the first aspect, the polymerizable compound includes at least one selected from the group consisting of polymerizable monomers, oligomers, and copolymers.

[0011] In a third aspect of the present invention, in the first or second aspect, the first electrolyte solution, the second electrolyte solution, or both, further comprises a lithium salt.

[0012] In a fourth aspect of the present invention, in any one of the first to third aspects, the second electrolytic solution further contains a polymerizable compound.

[0013] In a fifth aspect of the present invention, in any one of the first to fourth aspects, the step (S2) is carried out under room temperature conditions.

[0014] According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the step (S3) is carried out when the internal temperature of the battery is room temperature, or between room temperature and 100°C.

[0015] In a seventh aspect of the present invention, in any one of the first to sixth aspects, the step (S3) is carried out under vacuum conditions or reduced pressure conditions.

[0016] In an eighth aspect of the present invention, in any one of the first to seventh aspects, the crosslinking agent is at least one selected from the group consisting of an azo compound, a peroxide compound, and a redox compound.

[0017] A ninth aspect of the present invention relates to a method for producing a secondary battery according to an embodiment of the present invention, A step (S1) of manufacturing a spare battery by housing the electrode assembly and a first electrolytic solution composed of an organic solvent and a polymerizable compound in a battery exterior material; A step (S2) of leaving the spare battery for a predetermined time; Injecting a second electrolyte solution, which is composed of an organic solvent and a cross-linking agent, into the reserve battery (S3); and a step (S4) of leaving the result of the step (S3) at a temperature of 50 to 80° C. for a predetermined period of time.

[0018] A tenth aspect of the present invention relates to the ninth aspect, wherein at least one of the first electrolytic solution and the second electrolytic solution contains a lithium salt. Effect of the Invention

[0019] According to the method for manufacturing a secondary battery of the present invention, the liquid electrolyte is uniformly impregnated into the battery and then gelled. As a result, a secondary battery having a uniform distribution of gel polymer electrolyte can be manufactured by uniformly impregnating the inside of the battery. In addition, the gel polymer secondary battery manufactured by the method for manufacturing a secondary battery of the present invention does not leak electrolyte compared to a battery using a liquid electrolyte, and has excellent heat resistance, safety, and durability. In addition, since the electrolyte is uniformly distributed inside the battery, the battery exhibits uniform electrochemical characteristics. [Brief description of the drawings]

[0020] The drawings attached to this specification are illustrative of preferred embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited only to the matters described in such drawings. The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the detailed description of the invention described below, and therefore the present invention should not be interpreted as being limited only to the matters described in such drawings. Meanwhile, the shape, size, scale, ratio, etc. of elements in the drawings described in this specification may be exaggerated to emphasize a clearer description.

[0021] [Figure 1] 3 is a schematic diagram showing how the first and second electrolyte solutions permeate and diffuse into the electrode assembly in the battery manufacturing method according to the present invention. [Diagram 2] 3 is a schematic diagram showing how the first and second electrolyte solutions permeate and diffuse into the electrode assembly in the battery manufacturing method according to the present invention. [Diagram 3] 3 is a schematic diagram showing how the first and second electrolyte solutions permeate and diffuse into the electrode assembly in the battery manufacturing method according to the present invention. [Figure 4] 3 is a schematic diagram showing how the first and second electrolyte solutions permeate and diffuse into the electrode assembly in the battery manufacturing method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiment of the present invention will be described in detail. Prior to this, the terms and words used in the present specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as being in accordance with the meaning and concept of the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of the term in order to best describe the invention. Therefore, since the configuration according to the embodiment described in this specification is merely one most preferred embodiment of the present invention and does not represent the entire technical idea of ​​the present invention, it should be understood that there are various equivalents and modifications that can replace them at the time of this application.

[0023] Throughout this specification, when a part "includes," "comprises," "haves," or "has" certain elements, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0024] In addition, the terms "about," "substantially," and the like, used throughout this specification, when the tolerances of manufacturing and materials inherent in the referred meaning are given, are used to mean a numerical value or a value close to that numerical value, and are used to prevent unscrupulous infringers from unfairly taking advantage of the disclosure in which precise numerical values ​​or absolute numerical values ​​are mentioned to aid in the understanding of this application.

[0025] Throughout this specification, the term "A and / or B" means "A or B, or both."

[0026] Certain terminology is used in the following detailed description for convenience only and not for purposes of limitation. The words "right", "left", "top" and "bottom" designate directions in the drawings to which reference is made. The words "inwardly" and "outwardly" designate directions toward or away from the geometric center, respectively, of the designated device, system and components thereof. "Front", "rear", "upper", "lower" and related words and phrases designate locations and orientations in the drawings to which reference is made and are not intended to be limiting. Such terms include the example words above, derivatives thereof and words of similar import.

[0027] The present invention relates to a secondary battery containing a gel polymer electrolyte and a method for producing the same.

[0028] secondary battery The secondary battery includes an electrode assembly in which the negative electrode, the separator, and the positive electrode are stacked in this order so that the negative electrode and the positive electrode are electrically insulated by the separator. The secondary battery also includes an electrolyte, and the electrode assembly is impregnated with the electrolyte. In the present invention, the electrolyte is a gel polymer electrolyte formed by crosslinking a polymerizable compound.

[0029] In the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on at least one or both sides of the positive electrode current collector. The positive electrode active material layer includes a positive electrode mixture, and the positive electrode mixture may include a positive electrode active material, a binder, and a conductive material. In the present specification, it is described that the positive electrode mixture does not include an electrolyte impregnated in the positive electrode. In the present invention, the positive electrode active material layer has a porous characteristic including a plurality of pores, and the pores are filled with an electrolyte as described below.

[0030] The positive electrode current collector is not particularly limited as long as it has conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0031] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specifically, it may include a lithium composite metal oxide containing at least one metal selected from the group consisting of cobalt, manganese, nickel, and aluminum and lithium. More specifically, the lithium composite metal oxide may be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li a (Ni x Co y Mn z M (1-(x+y+z)) ) 2-a O2 (where a is 0.8 or more and 1.3 or less, x, y, and z are each independently 0 or more and 1 or less, but x + y + z = 1, and M is one or more selected from Al, Mg, Fe, V, Cr, Ta, Ti, Mo, W, Zr, Ba) or Li(Ni p1 Co q1 Mnr2 ) 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 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are atomic fractions of independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1)), etc., and may contain any one or two or more of these compounds. In one embodiment of the present invention, the positive electrode active material is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.).

[0032] The positive electrode active material may be contained in an amount of 50% by weight to 99% by weight based on 100% by weight of the positive electrode binder material.

[0033] The binder is a component that aids in bonding between the positive electrode active material and the conductive material and bonding to the current collector, and any binder that can be used as a positive electrode binder may be used, and is not particularly limited. In the present invention, the positive electrode active material may be generally contained in an amount of 1 to 30% by weight relative to 100% by weight of the positive electrode mixture. Examples of such binders include polyvinylidene fluoride (PVDF) containing vinylidene fluoride as a polymerization unit, vinylidene fluoride-based polymers, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0034] The conductive material may usually be added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive electrode mixture.

[0035] Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and examples that may be used include carbon powders such as carbon black, acetylene black (or denka black), ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with an advanced crystal structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0036] In the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on at least one or both sides of the negative electrode current collector. The negative electrode active material layer may include a negative electrode mixture, and the negative electrode mixture may include a negative electrode active material, a binder, and a conductive material. In the present specification, it is explained that the negative electrode mixture does not include an electrolyte impregnated in the negative electrode. In the present invention, the negative electrode active material layer has a porous characteristic including a plurality of pores, and the pores are filled with an electrolyte as described below.

[0037] The negative electrode current collector may generally have a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and may be, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, stainless steel surface treated with carbon, nickel, titanium, silver, or aluminum-cadmium alloy. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface to strengthen the binding force of the negative electrode active material, and it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0038] The negative electrode active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of such a metal and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0039] As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, there is no particular limitation as long as it is a carbon-based negative electrode active material generally used in lithium ion secondary batteries. Representative examples thereof include crystalline carbon, amorphous carbon, or both of these may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0040] Examples of the metal composite oxide include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0 ≦ x ≦ 1), Li x WO2(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, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) selected from the group consisting of may be used.

[0041] Examples of the substance capable of doping and dedoping lithium include Si, SiO x(0 < x ≤ 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc. may be mentioned, and at least one of these may be mixed with SiO2 and used. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof may be selected.

[0042] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0043] The negative electrode active material may be 50 to 99% by weight based on 100% by weight of the negative electrode composite material.

[0044] The binder is a component that helps bind between the conductive material, the active material, and the current collector, and is not particularly limited as long as it is a component that can be used as a binder for the negative electrode of a secondary battery. The negative electrode binder can usually be added in an amount of 1 to 30% by weight in 100% by weight of the negative electrode composite material. Examples of such binders include polyvinylidene fluoride (PVDF) containing vinylidene fluoride as a polymerization unit, vinylidene fluoride-based polymers, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers thereof, etc.

[0045] The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1 to 20% by weight relative to 100% by weight of the negative electrode composite. The conductive material may be the same as or different from the conductive material used in the manufacture of the positive electrode, and may be, for example, carbon powder such as carbon black, acetylene black (or denka black), ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with an advanced crystal structure; conductive fibers such as carbon fiber and metal fiber; metal powder such as carbon fluoride, aluminum, 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; or the like.

[0046] The separator serves to block an internal short circuit between the positive and negative electrodes, provide an ion transfer path between the positive and negative electrodes, and retain an electrolyte.

[0047] According to an embodiment of the present invention, the separator may be formed by mixing a polymer resin, a filler such as inorganic particles, and a solvent to prepare a separator composition, and then directly coating and drying the separator composition on an electrode to form a separator film, or by casting and drying the separator composition on a support, and then laminating the separator film peeled off from the support on an electrode.

[0048] Meanwhile, in another embodiment of the present invention, the separator may be a porous polymer film commonly used as a separator for electrochemical devices such as secondary batteries, for example, a porous polymer film made of a polyolefin polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, ethylene / methacrylate copolymer, etc., either alone or in a laminate thereof, or a typical porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc., but is not limited thereto.

[0049] In this case, the pore diameter of the porous separation membrane may be generally 0.01 to 50 μm, and the porosity may be generally 5 to 95 vol%. The thickness of the porous separation membrane may be generally 5 to 300 μm. In the present invention, the separation membrane has a porous characteristic including a large number of pores, and as described above, the pores are filled with an electrolyte.

[0050] Meanwhile, in the present invention, the separation membrane may have a heat-resistant layer formed on at least one surface of the above-mentioned polymer film or nonwoven fabric made of a polymer material. The heat-resistant layer may include inorganic particles and a polymer resin, and the weight ratio thereof may be about 50:50 to about 99:1. Preferably, the heat-resistant layer may have a structure based on an interstitial volume between adjacent inorganic particles.

[0051] Meanwhile, in the present invention, the electrode assembly may be prepared by laminating an anode, a cathode, and a separator such that a separator is disposed between the cathode and the anode, and then bonding the interfaces by applying appropriate pressure and / or heat (lamination process). In such a lamination process, process conditions conventionally used in the technical field to which the present invention belongs may be referred to.

[0052] Meanwhile, the battery case is not limited to a specific material or shape, and may be, for example, a cylindrical or rectangular case using a metal can, a pouch type using a pouch film, or a coin type case.

[0053] Meanwhile, in the present invention, the secondary battery includes a gel polymer electrolyte. The gel polymer electrolyte of the present invention has a gel form formed by crosslinking a polymerizable compound together with an organic solvent, and will be described in detail below together with a method for manufacturing the battery.

[0054] Secondary battery manufacturing method Next, a method for producing the secondary battery according to the present invention will be described.

[0055] In one embodiment of the present invention, the method for producing a secondary battery includes: A step (S1) of manufacturing a spare battery by housing the electrode assembly and a first electrolytic solution containing an organic solvent and a polymerizable compound in a battery exterior material; A step (S2) of leaving the spare battery for a predetermined time; Injecting a second electrolyte solution containing an organic solvent and a crosslinking agent into the reserve battery (S3); and a step (S4) of leaving the result of the step (S3) at a temperature of 50 to 80° C. for a predetermined period of time.

[0056] In particular, in the battery production method of the present invention, the first electrolyte does not contain a crosslinking agent.

[0057] In this specification, the reserve battery is a term used to distinguish it from the final product and refers to an intermediate product in the manufacturing process.

[0058] First, an electrode assembly and a first electrolyte solution are prepared, and then housed in a battery exterior material (S1).

[0059] The electrode assembly is the same as that described for the secondary battery according to the present invention. Therefore, for the sake of convenience, the repeated description will be omitted as appropriate. In one embodiment of the present invention, the electrode assembly can be prepared as a wound jelly roll type electrode assembly, a stack type electrode assembly, or a stack / folding type electrode assembly according to the purpose and use of the battery. Although not particularly limited, the process can be performed in the order of housing the electrode assembly in a battery exterior material and then injecting a first electrolyte solution.

[0060] In one embodiment of the present invention, the first electrolyte solution may contain an organic solvent and a polymerizable compound. The first electrolyte solution may further contain a lithium salt. Meanwhile, in the present invention, the first electrolyte solution is characterized in that it does not contain a crosslinking agent.

[0061] In one embodiment of the present invention, the amount of the organic solvent injected using the first electrolytic solution may be 30 to 80% by weight based on the total amount injected. The first electrolytic solution functions as a medium for uniformly diffusing the polymerizable compound inside the electrode assembly together with the organic solvent, so that an appropriate amount can be injected to diffuse the polymerizable compound inside the electrode assembly.

[0062] The organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charge and discharge process of the secondary battery and can exhibit desired properties together with the additives. For example, carbonate-based organic solvents, ether-based organic solvents, and ester-based organic solvents can be used alone or in combination of two or more.

[0063] The carbonate organic solvent among the organic solvents may include at least one of a cyclic carbonate organic solvent and a linear carbonate organic solvent. Specifically, the cyclic carbonate 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.

[0064] In addition, the linear carbonate 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, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, and more specifically may include dimethyl carbonate.

[0065] The ether-based organic solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more of these, but is not limited thereto.

[0066] The ester-based organic solvent may be at least one selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents.

[0067] Specific examples of the linear ester-based organic solvent include, but are not limited to, any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more of these.

[0068] Specific examples of the cyclic ester organic solvent include, but are not limited to, any one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more of these.

[0069] Among the ester-based solvents, cyclic carbonate-based compounds are preferably used since they are high-viscosity organic solvents that have a high dielectric constant and can easily dissociate the lithium salt in the electrolyte. When such cyclic carbonate-based compounds are mixed in an appropriate ratio with linear carbonate-based compounds and linear ester-based compounds having low viscosity and low dielectric constant, such as dimethyl carbonate and diethyl carbonate, a gel polymer electrolyte having high electrical conductivity can be prepared, and thus the cyclic carbonate-based compounds can be more preferably used.

[0070] The polymerizable compound, that is, the polymerizable monomer, oligomer, or copolymer, is a compound that has a polymerizable functional group selected from the group consisting of a vinyl group, an epoxy group, an allyl group, and a (meth)acrylic group, which can undergo a polymerization reaction in its structure, and can be gelled by polymerization or crosslinking, and is not particularly limited as long as it is used as a polymerizable monomer, oligomer, or copolymer for producing a general gel polymer electrolyte.

[0071] Among these, examples of the polymerizable monomer include, but are not limited to, tetraethylene glycol diacrylate, polyethylene glycol diacrylate (molecular weight (Mw) 50 to 20,000), 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, and the like. tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, poly(ethylene glycol) diglycidylether, 1,5-hexadiene diepoxide, glycerol propoxylate triglycidyl ether, vinylcyclohexene dioxide, 1,2,7,8-diepoxyoctane (1,2,7,Examples of the glycidyl ether include, but are not limited to, 8-diglycidyloctane, 4-vinylcyclohexene dioxide, butyl glycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, ethylene glycol diglycidyl ether, glycerol triglycidyl ether, and glycidyl methacrylate. These compounds may be used alone or in combination of two or more. 。

[0072] Representative examples of the copolymer include at least one selected from the group consisting of allyl 1,1,2,2-tetrafluoroethyl ether (TFE)-(2,2,2-trifluoroethyl acrylate) copolymer, TFE-vinyl acetate copolymer, TFE-(2-vinyl-1,3-dioxolane) copolymer, TFE-vinyl methacrylate copolymer, TFE-acrylonitrile copolymer, TFE-vinyl acrylate copolymer, TFE-methyl acrylate copolymer, TFE-methyl methacrylate (MMA) copolymer, and TFE-2,2,2-trifluoroethyl acrylate (FA) copolymer.

[0073] The polymerizable compound may be contained in an amount of 0.01 to 20% by weight based on the total weight of the first electrolyte solution. If the content of the polymerizable compound exceeds 20% by weight, it may lead to excessive gelation or excessive densification (concentration) in the steps described below, resulting in a gel with high resistance. Conversely, if the content of the polymerizable compound is less than 0.01% by weight, it is difficult to expect the effect of the gel polymer electrolyte. Meanwhile, in one embodiment of the present invention, the polymerizable compound is preferably adjusted to be injected in an amount of 0.5% by weight or more and 10% by weight or less based on the total weight of the electrolyte injected into the battery.

[0074] The lithium salt is used as an electrolyte salt in a lithium secondary battery and is used as a medium for transferring ions. Generally, lithium salts contain Li as a cation. + The anion is F. - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (F2SO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - It may include at least one selected from the group consisting of:

[0075] The lithium salt may be used alone or in a mixture of two or more kinds as necessary. The lithium salt may be appropriately changed within a range that is normally usable, but in order to obtain an optimal coating formation effect for preventing corrosion of the electrode surface, the lithium salt may be contained in the gel polymer electrolyte at a concentration of 0.5 to 2M, specifically 0.9 to 1.5M, in the entire finally obtained battery. By containing 0.5M or more of lithium salt, the gel polymer electrolyte of the present invention can reduce resistance due to depletion of lithium ions during high-rate charging and discharging. In addition, when the concentration of the electrolyte salt in the gel polymer electrolyte of the present invention satisfies the above range, the lithium cations present in the composition for gel polymer electrolyte increase, and thus the lithium cations (Li + ) can ensure high ion transport properties (i.e., cation transfer number), thereby achieving a reduction in the diffusion resistance of lithium ions and improving cycle capacity characteristics.

[0076] The lithium salt may be contained in the first electrolyte solution in its entirety, may be contained separately in the first electrolyte solution and the second electrolyte solution, or may be entirely contained in the second electrolyte solution. When the lithium salt is contained separately in the first and second electrolyte solutions, the ratio of the lithium salt to be divided is not set to a specific range.

[0077] The reserve battery may be provided to a next step in a sealed state by sealing an exterior material after the electrode assembly and the first electrolyte are contained therein.

[0078] Next, an aging step (S2) is performed in which the spare battery manufactured in step (S1) is left for a predetermined time. Since the first electrolyte injected in step (S1) does not contain a crosslinking agent, crosslinking of the polymerizable compound does not proceed, and the uncrosslinked state is maintained, and the electrolyte maintains a liquid state. This allows the first electrolyte to permeate and diffuse into the spare battery, particularly the electrode assembly, and thus the electrode assembly is impregnated with the first electrolyte. The aging step may be performed under vacuum maintenance conditions to more uniformly impregnate the electrode assembly with the electrolyte. For example, the aging step may be performed by alternately leaving the battery under vacuum conditions and normal pressure conditions.

[0079] Specifically, the battery may be left under normal pressure conditions for aging, and then the battery case may be partially opened, and one or more steps selected from vacuum treatment, pressurization, and degassing may be further performed. The vacuum wetting step may be performed under reduced pressure conditions of -70 to -99 kPa. Meanwhile, after the injection, the battery may be pressurized to promote impregnation of the electrolyte into the electrode assembly. At this time, the pressurization may be performed within a range of 0 to 190 kPa. The vacuum wetting may be performed within a few minutes, or may be performed two or more times. In a specific embodiment of the present invention, after forming a vacuum atmosphere under reduced pressure conditions of about -95 kPa, the vacuum wetting may be performed eight times for 1 to 5 minutes. In addition, the vacuum treatment has the effect of sufficiently transmitting the electrolyte to fine voids in the electrodes and separator, thereby improving the wetting property of the electrode assembly.

[0080] The aging is not particularly limited, and may be performed within a few hours to a few days. For example, the step may be performed within 72 hours. In the present invention, the aging is preferably performed under room temperature conditions in terms of promoting impregnation. Meanwhile, the step (S2) may be performed under room temperature conditions. In the present invention, the room temperature may be 18 to 28°C.

[0081] FIG. 1 is a schematic cross-sectional view of an electrode assembly 100 in which a negative electrode and a positive electrode are stacked with a separator interposed therebetween. Referring to FIG. 1, the positive electrode includes a positive electrode active material 101, and the negative electrode includes a negative electrode active material 102. Meanwhile, materials such as conductive materials and binders other than the electrode active materials are not shown, but it goes without saying that these electrode materials are included in the electrodes as described above. When a first electrolyte solution 201 is injected into the electrode assembly prepared in this manner, the empty space of the electrode assembly is impregnated with the electrolyte, and the impregnation can be further promoted by the aging process described above. FIG. 2 is a schematic view showing the state in which the inside of the battery is impregnated with the first electrolyte solution 201 after the injection of the first electrolyte solution 201.

[0082] Next, after the aging process of step (S2) is performed, the second electrolyte solution 202 is injected (S3). The second electrolyte solution may contain an organic solvent and a crosslinking agent. As a result of the injection of the first electrolyte solution, the second electrolyte solution does not contain a polymerizable compound or a lithium salt, or the content of these is low even if it further contains them. Therefore, the concentration and viscosity of the solid content of the second electrolyte solution are lower than the concentration and viscosity of the solid content of the first electrolyte solution. Furthermore, in the above-mentioned step, the electrode assembly is already impregnated with the first electrolyte solution. As a result, when the second electrolyte solution 202 is injected, the second electrolyte solution rapidly permeates into the electrode assembly by liquid-liquid diffusion. Figure 3 is a schematic diagram of the liquid-liquid diffusion shape of the third electrolyte solution containing an initiator. Arrow A in Figure 3 indicates the direction in which the second electrolyte solution permeates into the electrode assembly 100 by liquid-liquid diffusion.

[0083] The amount of the organic solvent injected using the second electrolytic solution may be appropriately adjusted within the range of 20 to 70% by weight based on the total amount of the organic solvent injected.

[0084] In one embodiment of the present invention, in the step (S3), the internal temperature of the battery may be room temperature or a temperature range of room temperature to 100°C. Since the electrolyte and the electrode assembly are usually stored at room temperature, the internal temperature of the battery when the electrolyte is injected may be room temperature. In one embodiment of the present invention, the electrolyte may be heated and injected in order to promote diffusion of the electrolyte in the battery. Meanwhile, in one embodiment of the present invention, the injection of the electrolyte in the step (S3) may be performed under vacuum or reduced pressure conditions, for example, under conditions of -70 to -99 kpa. Meanwhile, after the injection, the battery may be pressurized to promote impregnation of the electrolyte into the electrode assembly. At this time, the pressurization may be performed within a range of 0 to 190 kPa.

[0085] The crosslinking agent may be a conventional thermal or photopolymerization initiator known in the art, for example, the polymerization initiator may be decomposed by heat to form radicals, which may react with the crosslinking agent by free radical polymerization to form a gel polymer electrolyte.

[0086] More specifically, non-limiting examples of the polymerization initiator include benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butylperoxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide, and hydrogen peroxide. and organic peroxides and hydroperoxides, and one or more azo compounds selected from the group consisting of 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN), and 2,2'-azobisdimethyl-valeronitrile (AMVN).

[0087] The polymerization initiator may be decomposed in the battery by heat, for example at 30 to 100° C. or at room temperature of 5 to 30° C., to form radicals, and the polymerizable oligomer may react with an acrylate compound through free radical polymerization to form a gel polymer electrolyte.

[0088] The crosslinking agent may be contained in an amount of 0.01 to 20 parts by weight, specifically 0.1 to 10 parts by weight, based on 100 parts by weight of the injected polymerizable compound. When the crosslinking agent is contained in the range of 0.01 to 20 parts by weight, the conversion rate of the gel polymer can be increased to ensure the electrolytic properties of the gel polymer, and the pre-gel reaction can be prevented to improve the wetting of the electrolyte to the electrode.

[0089] On the other hand, if necessary, the second electrolytic solution may further contain a lithium salt and / or a polymerizable compound.

[0090] Next, a crosslinking reaction of the polymerizable compound is carried out (S4). In the present invention, the crosslinking reaction may be carried out by placing the spare battery in a predetermined heating device and leaving it for a predetermined time. In the method for producing a lithium secondary battery of the present invention, the step (S4) may be carried out under conditions of 50 to 80°C. In a specific embodiment of the present invention, the step (S4) may be carried out under conditions of 60 to 70°C. Meanwhile, the step (S4) may be carried out for 30 minutes to 24 hours. In a specific embodiment of the present invention, the step (S4) may be carried out at about 65°C for 5 hours or less.

[0091] The gel polymer electrolyte battery obtained by the above manufacturing method has uniform electrochemical properties throughout the battery since the gel polymer electrolyte is uniformly distributed in the electrode assembly. Figure 4 is a schematic diagram of the gel polymer electrolyte 204 impregnated inside the battery.

[0092] Meanwhile, in one embodiment of the present invention, the first and / or second electrolyte solution may further include an additive capable of forming a more stable ion-conductive coating on the electrode surface as necessary to prevent the gel polymer electrolyte from being decomposed under a high-power environment during preparation, thereby inducing collapse of the negative electrode, or to further improve the effects of low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and improvement of swelling during high-temperature storage.

[0093] Specifically, representative examples of the additional additive include at least one first additive selected from the group consisting of sultone-based compounds, sulfite-based compounds, sulfone-based compounds, sulfate-based compounds, halogen-substituted carbonate-based compounds, nitrile-based compounds, cyclic carbonate-based compounds, phosphate-based compounds, borate-based compounds, and lithium salt-based compounds.

[0094] The sultone-based compound may be 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, which may be contained in an amount of 0.3 to 5 wt%, specifically 1 to 5 wt%, based on the total weight of the composition for gel polymer electrolyte. If the content of the sultone-based compound in the composition for gel polymer electrolyte exceeds 5 wt%, an excessively thick coating may be formed on the surface of the electrode, causing an increase in resistance and a deterioration in output, and an excessive amount of additive in the composition for gel polymer electrolyte may cause an increase in resistance and a deterioration in output characteristics.

[0095] The sulfite compound may be 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 contained in an amount of 3 wt % or less based on the total weight of the gel polymer electrolyte composition.

[0096] The sulfone-based compound may be at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone, and may be contained in an amount of 3 wt % or less based on the total weight of the first and second electrolytic solutions.

[0097] The sulfate-based compound may be ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS), and may be contained in an amount of 3 wt % or less based on the total weight of the gel polymer electrolyte.

[0098] The halogen-substituted carbonate-based compound may be fluoroethylene carbonate (FEC), which may be contained in an amount of 5% by weight or less based on the total weight of the gel polymer electrolyte composition. If the content of the halogen-substituted carbonate-based compound in the entire gel polymer electrolyte exceeds 5% by weight, the cell swelling performance may deteriorate.

[0099] Examples of the nitrile compound 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.

[0100] The cyclic carbonate compound may be vinylene carbonate (VC) or vinyl ethylene carbonate, and may be contained in an amount of 3% by weight or less based on the total weight of the gel polymer electrolyte composition. If the content of the cyclic carbonate compound in the gel polymer electrolyte exceeds 3% by weight, the cell swelling suppression performance may be deteriorated.

[0101] The phosphate-based compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyltrimethylsilylphosphate, trimethylsilylphosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphite, and may be contained in an amount of 3 wt % or less based on the total weight of the gel polymer electrolyte.

[0102] The borate-based compound includes lithium oxalyl difluoroborate, which may be contained in an amount of 3% by weight or less based on the total weight of the gel polymer electrolyte.

[0103] The lithium salt-based compound is a compound different from the lithium salt contained in the gel polymer electrolyte composition, and includes at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bis(oxalato)borate (LiB(C2O4)2)), and LiBF4, and may be contained in an amount of 3 wt% or less based on the total weight of the gel polymer electrolyte.

[0104] The additional additive may be mixed and contained in an amount of 20% by weight or less, specifically 0.1 to 10% by weight, based on the total weight of the gel polymer electrolyte. If the content of the additional additive is less than 0.01% by weight, the effect of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is insignificant, and if the content of the additional additive is more than 20% by weight, excessive side reactions may occur in the gel polymer electrolyte during charging and discharging of the battery. In particular, the additive may not be fully decomposed at high temperatures, and therefore may remain as an unreacted substance or precipitate in the gel polymer electrolyte at room temperature. This may cause side reactions that reduce the life and resistance characteristics of the secondary battery.

[0105] As described above, in the method for manufacturing a secondary battery according to the present invention, the liquid electrolyte is uniformly impregnated into the battery, and then the electrolyte is gelled. As a result, a secondary battery having a uniform distribution of gel polymer electrolyte can be manufactured by uniformly impregnating the inside of the battery. In addition, the gel polymer secondary battery manufactured by the method for manufacturing a secondary battery according to the present invention does not leak electrolyte compared to a battery using a liquid electrolyte, and has excellent heat resistance, safety, and durability. In addition, since the electrolyte is uniformly distributed inside the battery, the entire battery exhibits uniform electrochemical characteristics.

[0106] In the present invention, the secondary battery is preferably a lithium secondary battery, and non-limiting examples of the lithium secondary battery include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0107] Hereinafter, the present invention will be described in detail with reference to examples in order to specifically explain the present invention. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those having average knowledge in the art.

[0108] Working Example (1) Example 1 to Example 2 (Manufacturing of electrode assemblies) (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 A positive electrode active material slurry (solid content 50 wt%) was prepared by adding 94 wt% O2, 3 wt% carbon black as a conductive material, and 3 wt% polyvinylidene fluoride (PVDF) as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent. The positive electrode active material slurry was applied to an aluminum (Al) thin film as a positive electrode current collector having a thickness of about 20 μm, dried, and then roll pressed to prepare a positive electrode.

[0109] A negative electrode active material slurry (solid content 80 wt%) was prepared by adding 96 wt% carbon powder (graphite) as a negative electrode active material, 3 wt% PVDF as a binder, and 1 wt% carbon black as a conductive material to NMP as a solvent. The negative electrode active material slurry was applied to a copper (Cu) thin film as a negative electrode current collector having a thickness of 10 μm, dried, and then roll pressed to prepare a negative electrode.

[0110] The positive electrodes, negative electrodes, and a separator having three layers of polypropylene / polyethylene / polypropylene (PP / PE / PP) were alternately stacked to prepare a stack-type electrode assembly including 20 positive electrodes.

[0111] (Production of the first electrolyte solution) A non-aqueous electrolyte solution was prepared by dissolving LiPF6 at a concentration of 1.0M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30: 70 (volume ratio). A first electrolyte solution was prepared by adding trimethylolpropane triacrylate as a polymerizable compound to the non-aqueous electrolyte solution in an amount of 3 wt% in Example 1 and 5 wt% in Example 2 relative to 100 wt% of the total gel polymer electrolyte. The amount of the organic solvent in the first electrolyte solution was 70 wt% relative to 100 wt% of the injection design amount.

[0112] (Production of second electrolyte) A second electrolyte solution was prepared by adding AIBN (methyl 2,2'-azobis(2-methylpropionate)) at 0.02 wt% relative to 100 wt% of the gel polymer electrolyte to an organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30: 70 (volume ratio). The amount of the organic solvent in the second electrolyte solution was 30 wt% relative to 100 wt% of the injection design amount.

[0113] (Manufacture of lithium secondary batteries) The electrode assembly thus manufactured was placed in a battery case, and the first electrolyte was injected. The first electrolyte was injected under reduced pressure conditions of -70 to -99 kPa, and then pressurized. The battery case was then sealed and left to rest for 3 days at room temperature. Then, a part of the battery case was opened, and the battery case was degassed 8 times for 5 minutes under reduced pressure conditions of -95 kPa. Next, the second electrolyte was injected and sealed. The second electrolyte was injected under reduced pressure conditions of -70 to -99 kPa, and then pressurized. Next, the battery was placed in a heating chamber and held for 5 hours. The heating chamber was maintained at 60 to 70°C. Then, the battery was removed from the chamber and left at room temperature for 1 hour, thus obtaining a battery.

[0114] (2) Comparative Example 1 An electrode assembly was manufactured in the same manner as in the example. The electrode assembly was placed in a battery case, and an electrolyte was injected. The electrolyte was injected under reduced pressure conditions of -70 to -99 kPa, and then pressurized. The electrolyte was a non-aqueous organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30:70 (volume ratio) containing LiPF6 at a concentration of 1.0 M. Next, the battery case was sealed and left to rest at room temperature for 3 days. Thereafter, a part of the battery case was opened, and the battery case was degassed 8 times for 5 minutes under reduced pressure conditions of -95 kPa, and then resealed.

[0115] (3) Comparative Example 2 An electrode assembly was manufactured in the same manner as in the examples. Next, the electrode assembly was placed in a battery case, and a composition for a gel polymer electrolyte was poured into the battery case. The composition for a gel polymer electrolyte was poured under reduced pressure conditions of -70 to -99 kPa, and then pressurized. The composition for a gel polymer electrolyte was a non-aqueous organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30: 70 (volume ratio) containing LiPF6 at a concentration of 1.0 M. In addition, trimethylolpropane triacrylate and AIBN were further added as polymerizable compounds. The polymerizable compound was added at 3 wt% relative to 100 wt% of the composition for a gel polymer electrolyte, and the AIBN was added at 0.02 wt% relative to 100 wt% of the composition for a gel polymer electrolyte. The battery case was sealed and left to rest at room temperature for 3 days. Then, a part of the battery case was opened, and degassed 8 times for 5 minutes under reduced pressure conditions of -95 kPa. Next, the battery was placed in a heating chamber and held there for 5 hours. The heating chamber was maintained at 60 to 70° C. Thereafter, the battery was taken out of the chamber and left at room temperature for 1 hour, thus obtaining a battery.

[0116] (4) Comparative Example 3 An electrode assembly was manufactured in the same manner as in the example.

[0117] (Production of the first electrolyte solution) A non-aqueous electrolyte was prepared by dissolving LiPF6 at a concentration of 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30: 70 (volume ratio). The amount of the organic solvent in the first electrolyte was 70 wt% with respect to the injection design amount of 100 wt%.

[0118] (Production of second electrolyte) A second electrolyte solution was prepared by adding 5% trimethylolpropane triacrylate as a polymerizable compound to an organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30: 70 (volume ratio) relative to 100% of the gel polymer electrolyte, and adding 0.02% AIBN to 100% of the gel polymer electrolyte. The amount of the organic solvent in the second electrolyte solution was 30% by weight relative to 100% by weight of the injection design amount.

[0119] (Manufacture of lithium secondary batteries) The electrode assembly was placed in a battery case, and the first electrolyte was injected. The battery case was then sealed and left to rest at room temperature for 3 days. Then, a part of the battery case was opened, and the battery case was degassed 8 times for 5 minutes under reduced pressure conditions of -95 kPa. Next, the second electrolyte was injected and sealed. Next, the battery was placed in a heating chamber and held for 5 hours. The heating chamber was maintained at 60 to 70°C. Then, the battery was removed from the chamber and left at room temperature for 1 hour, and a battery was obtained in this manner. The first and second electrolyte injections were performed under reduced pressure conditions of -70 to -99 kPa, respectively, and pressurization was performed after injection of each electrolyte. The batteries manufactured in each of the examples and comparative examples were designed to have a capacity of about 40 ampere-hours (Ah).

[0120] [Table 1]

[0121] From the above, it was confirmed that the batteries of Example 1 and Example 2 have superior resistance characteristics compared to the batteries of Comparative Example 2 and Comparative Example 3. The resistance characteristics of the batteries of Example 1 and Example 2 were achieved at a similar level to the liquid electrolyte battery of Comparative Example 1. Meanwhile, it was confirmed that the amount of leakage of the liquid electrolyte was larger in the battery of Comparative Example 1 compared to the Examples. The battery according to the present invention can be applied as a unit battery of a battery module for a power source of a medium-sized or large-sized device such as an electric vehicle. The battery module is manufactured by combining and electrically connecting several to several tens of the unit batteries, and the performance of the battery module is represented by accumulating the performance of the unit batteries, so that the improvement of the performance of the unit battery is directly related to the improvement of the performance of the battery module. When the battery manufactured by the method according to the present invention is applied to the battery module, the performance of the medium-sized or large-sized device to which it is applied can be improved.

[0122] Resistance measurement The resistance of the batteries obtained in each of the examples and comparative examples was measured by electrochemical impedance spectroscopy under the conditions of 25° C. and a scan range of 100,000 Hz to 10,000 Hz using a Solaton 1470E cell test system and a Frequency Response Analyzer 1255B.

[0123] The actual capacity of the battery compared to its design capacity (%), In each of the examples and comparative examples, the gel polymer battery was charged at a constant current of 0.1 C until the voltage reached 4.2 V, and then discharged at the same current until the voltage reached 2.5 V. Using the discharge capacity obtained at this time, the efficiency of the initial discharge capacity and the actual discharge capacity was calculated according to the following formula 1.

[0124] <Expression 1> Actual discharge efficiency (%) = [1st cycle discharge capacity / cell target discharge capacity] x 100

[0125] Leakage measurement In each of the examples and comparative examples, a hole of about <1.0 mm was formed in the battery case of the gel polymer battery, and then the battery was left for 24 hours with the angle between the battery and the ground (experimental table) at 1 degree. The weight was measured before and after the battery was left for 24 hours. [Explanation of symbols]

[0126] 100 electrode assembly 201 First electrolyte 202 Second electrolyte 203 Gel polymer electrolyte A Liquid-liquid diffusion direction 101 Cathode active material 102 Negative electrode active material

Claims

1. A step (S1) of manufacturing a spare battery by housing an electrode assembly and a first electrolytic solution containing an organic solvent and a polymerizable compound in a battery exterior material; A step (S2) of leaving the spare battery for a predetermined time; A step (S3) of injecting a second electrolytic solution containing an organic solvent, a polymerizable compound, and a crosslinking agent into the reserve battery; Step (S4) of leaving the result of step (S3) at a temperature of 50 to 80° C. for a predetermined time; Including, The method for producing a secondary battery, wherein the first electrolytic solution does not contain a crosslinking agent.

2. The method for producing a secondary battery according to claim 1 , wherein the polymerizable compound includes at least one selected from the group consisting of polymerizable monomers, oligomers, and copolymers.

3. The method for producing a secondary battery according to claim 1 , wherein the first electrolytic solution, the second electrolytic solution, or both of them further contain a lithium salt.

4. The method for producing a secondary battery according to claim 1 , wherein the step (S2) is performed under room temperature conditions.

5. The method for manufacturing a secondary battery according to claim 1 , wherein the step (S3) is performed when the internal temperature of the battery is at room temperature or at room temperature to 100° C.

6. The method for producing a secondary battery according to claim 1 , wherein the step (S3) is carried out under vacuum or reduced pressure conditions.

7. The method for producing a secondary battery according to claim 1 , wherein the crosslinking agent is at least one selected from the group consisting of an azo compound, a peroxide compound, and a redox compound.

8. A step (S1) of manufacturing a spare battery by housing an electrode assembly and a first electrolytic solution including an organic solvent, a lithium salt, and a polymerizable compound in a battery exterior material; A step (S2) of leaving the spare battery for a predetermined time; A step (S3) of injecting a second electrolytic solution containing an organic solvent, a polymerizable compound, and a crosslinking agent into the reserve battery; Step (S4) of leaving the result of step (S3) at a temperature of 50 to 80° C. for a predetermined time; A method for manufacturing a secondary battery comprising the steps of:

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