Manufacturing method for electrode stacks

Abstract

The method for manufacturing an electrode laminate according to the present invention includes a step of preparing an electrode, a step of coating an electrolytic solution on the electrode, a step of disposing an oxygen barrier member on the coated electrolytic solution, and a step of curing the electrolytic solution impregnated inside the electrode and the electrolytic solution coated on the surface of the electrode.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0109521 dated August 30, 2022, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a method for manufacturing an electrode stack. [Background technology]

[0003] As technological development and demand for electric vehicles and energy storage systems (ESS) increase, the demand for batteries as their energy source is rapidly rising. Consequently, diverse research is being conducted on batteries that can meet a variety of requirements. In particular, research on lithium-ion secondary batteries, which possess high energy density and excellent lifespan and cycle characteristics, is actively progressing as power sources for such devices.

[0004] Generally, lithium secondary batteries include a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte. Conventionally, liquid electrolytes, in which lithium salts are dissolved in a non-aqueous organic solvent, have been mainly used as electrolytes for lithium secondary batteries. However, when using liquid electrolytes, there is a high possibility that the electrode material will deteriorate and the organic solvent will volatilize, as well as the risk of combustion or explosion due to rising ambient temperature and the temperature of the battery itself, and leakage, resulting in low safety.

[0005] In recent years, research on various materials and types of solid electrolytes has been actively conducted to overcome the safety issues associated with liquid electrolytes. Among these, gel electrolytes offer the advantage of not only excellent stability and processability, but also superior interfacial stability between the electrode and the electrolyte due to the inherent adhesive strength of the gel.

[0006] On the other hand, gel electrolytes can be manufactured by gelling (crosslinking) a composition of lithium salt, solvent, polymerizable monomer, and initiator at an appropriate temperature and time. However, when the electrolyte is gelled in an oxygen-containing environment, the gel electrolyte does not harden completely, resulting in problems such as the gel electrolyte volatilizing during the cell manufacturing process or detaching upon contact with other electrodes. To solve this, when the electrolyte is gelled in a space where an oxygen-free environment is achieved (for example, a glove box), there is a problem in that it is difficult to manufacture large-area electrode stacks due to the constraints of the space size.

[0007] Therefore, there is a need for technological development in methods that enable the complete curing of gel electrolytes even in oxygen-rich environments, thereby enabling the manufacture of large-area electrode stacks. [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to solve the above-mentioned problems and to provide a method for completely curing a gel electrolyte even in an oxygen-containing environment by blocking contact between the gel electrolyte and oxygen using an oxygen-blocking member. [Means for solving the problem]

[0009] According to one embodiment of the present invention, a method for manufacturing an electrode laminate is provided, which includes the steps of preparing electrodes, coating the electrodes with an electrolyte, arranging an oxygen barrier member on the coated electrolyte, and curing the electrolyte impregnated inside the electrodes and the electrolyte coated on the surfaces of the electrodes.

[0010] According to the electrode laminate manufacturing method of the present invention, an electrolyte layer may be formed on the electrode by hardening of the electrolyte coated on the surface of the electrode.

[0011] The oxygen barrier member may include one or more materials selected from the group consisting of glass, polypropylene (PP), and high-density polyethylene (HDPE).

[0012] The electrolyte may contain 5% to 50% by weight of monomers, 0.01% to 1% by weight of initiator, and 5% to 30% by weight of lithium salt.

[0013] The monomer may contain one or more selected from the group consisting of ethylene glycol diacrylate, triethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate (ETPTA), bisphenol A ethoxylated dimethacrylate, acrylic acid, carboxyethyl acrylate, methyl cyanoacrylate, ethyl cyanoacrylate, ethyl cyanoethoxyacrylate, cyanoacrylic acid, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

[0014] The initiators mentioned above include HMPP (2-hydroxy-2-methylpropiophenone), 1-hydroxycyclohexylphenyl ketone, benzophenone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, 2-[2-oxo-2phenylacetoxyethoxy]ethyl ester, oxyphenyl acetate 2-[2-hydroxyethoxy]ethyl ester, α-dimethoxy-α-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, It may contain at least one selected from the group consisting of 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl), bis[2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl]titanium, 4-isobutylphenyl-4'-methylphenyliodonium, hexafluorophosphate, and methylbenzoyl formate.

[0015] According to the method for manufacturing an electrode laminate of the present invention, the electrolyte layer may be formed by photocuring or thermal curing the electrolyte.

[0016] According to the method for manufacturing the electrode stack of the present invention, the solid content in the electrolyte may be 10% to 60%.

[0017] According to the method for manufacturing an electrode stack of the present invention, the viscosity of the electrolyte at 25°C may be 30 cP or less.

[0018] According to the method for manufacturing the electrode laminate of the present invention, the thickness of the electrolyte layer may be 10 μm to 200 μm.

[0019] According to the method for manufacturing an electrode laminate of the present invention, the thickness of the electrode may be 100 μm or less. [Effects of the Invention]

[0020] According to the present invention, by curing the electrolytic solution in a state where the contact between the electrolytic solution and oxygen is blocked using an oxygen-blocking member, the gel electrolyte can be completely cured even in an environment with oxygen. As a result, problems such as volatilization of the gel electrolyte or contact with other electrodes and detachment during the manufacturing process of the cell can be prevented.

[0021] In addition, the electrolytic solution can be cured in a state where it is impregnated to a sufficient depth of the electrode. As a result, even when another liquid electrolytic solution is not injected into the electrode laminate during the manufacture of the lithium secondary battery, the reaction occurs uniformly throughout the electrode, so that the capacity, output, and life characteristics of the lithium secondary battery can be improved.

[0022] Furthermore, according to the present invention, since it is not necessary to gelate the electrolyte in a space such as a glove box where an oxygen-free environment is realized, there is an advantage that a large-area electrode laminate can be manufactured.

Brief Description of the Drawings

[0023] [Figure 1] It is a photograph of the surface of the electrode laminate manufactured in Example 1. [Figure 2] It is a photograph of the surface of the electrode laminate manufactured in Example 2. [Figure 3] It is a photograph of the surface of the electrode laminate manufactured in Comparative Example 1. [Figure 4] It is a capacity (mAh)-voltage (V) graph during charging of the lithium secondary battery manufactured in Example 1. [Figure 5] It is a capacity (mAh)-voltage (V) graph during charging of the lithium secondary battery manufactured in Example 2. [Figure 6] It is a capacity (mAh)-voltage (V) graph during charging of the lithium secondary battery manufactured in Comparative Example 1.

Modes for Carrying Out the Invention

[0024] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and can be realized in a variety of different forms. These embodiments are provided to complete the disclosure of the present invention and to fully communicate the scope of the invention to those who are ordinary skill in the art to which the invention pertains, and the present invention is defined solely by the scope of the claims. Throughout the specification, the same reference numerals indicate the same components.

[0025] Unless otherwise defined, all terms used herein (including technical and scientific terms) should be used in a way that is commonly understood by those skilled in the art to which the invention pertains. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise.

[0026] The terms used herein are for illustrative purposes only and not to limit the invention. In this specification, singular nouns include plural nouns unless otherwise specified in the text. The terms “comprises” and / or “comprising” as used in this specification do not preclude the presence or addition of one or more other components in addition to the components mentioned.

[0027] In this specification, when a part is said to include a component, this means that, unless otherwise stated, it may include other components rather than excluding them.

[0028] In this specification, "A and / or B" means A, or B, or A and B.

[0029] In this specification, "%" means weight percent unless otherwise explicitly indicated.

[0030] In this specification, viscosity can be measured using a viscometer, specifically a Brookfield viscometer (DV-II+PRO Viscometer, Brookfield Corporation) at a temperature of 25°C, a humidity of 50 RH, and a frequency of 30 Hz.

[0031] The present invention will be described in more detail below.

[0032] The method for manufacturing an electrode laminate according to the present invention includes the steps of preparing electrodes, coating the electrodes with an electrolyte, placing an oxygen barrier member on the coated electrolyte, and curing the electrolyte impregnated inside the electrodes and the electrolyte coated on the surface of the electrodes.

[0033] When electrolytes are gelled in an oxygen-rich environment, the gel electrolyte does not fully harden, resulting in problems such as the gel electrolyte volatilizing during the cell fabrication process or detaching upon contact with other electrodes. To solve this, when the electrolyte is gelled in a space that eliminates oxygen (for example, a glove box), the constraints of the space make it difficult to manufacture large-area electrode stacks.

[0034] As a result of extensive research to solve these problems, the inventors of the present invention discovered that by curing the electrolyte while preventing contact between the electrolyte and oxygen using an oxygen-blocking member, the gel electrolyte can be completely cured even in an oxygen-containing environment, thus completing the present invention.

[0035] The following describes in more detail each step of the method for manufacturing the electrode stack according to the present invention.

[0036] <Method for manufacturing electrode stacks> (1) Steps to prepare electrodes The method for manufacturing an electrode stack according to the present invention begins with the step of preparing electrodes for a lithium secondary battery. In this case, the electrodes may be positive or negative electrodes.

[0037] The electrode includes a current collector and an electrode active material layer. In this case, the electrode active material layer may be formed on the current collector.

[0038] The current collector may be any material that does not cause a chemical change in the battery and has conductivity, and is not particularly limited. For example, the current collector may be copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel.

[0039] Next, the electrode active material layer may be a positive electrode active material layer containing a positive electrode active material or a negative electrode active material layer containing a negative electrode active material.

[0040] As the positive electrode active material, known positive electrode active materials in the technical field can be used without limitation. For example, lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium iron phosphate, lithium nickel manganese cobalt-based oxides, or combinations thereof can be used. Specifically, as the positive electrode active material, LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, and LiNi a Mn b Co c O2 (where 0 < a, b, c < 1) etc. can be used, but are not limited thereto.

[0041] As the negative electrode active material, natural graphite, artificial graphite, carbonaceous materials; lithium-containing titanium composite oxides (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe metals (Me); alloys composed of the metals (Me); oxides (MeO x ); and one or more negative electrode active materials selected from the group consisting of composites of the metals (Me) and carbon can be mentioned.

[0042] On the other hand, the electrode active material layer may further contain a conductive material and a binder in addition to active materials such as positive electrode active material and negative electrode active material.

[0043] The conductive material is a component that further improves the conductivity of the active material, and such conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. For example, the conductive material may be graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; 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. Specific examples of commercially available conductive materials include acetylene black-based materials (such as those from Chevron Chemical Company, Denka Black (Denka Singapore Private Limited), and Gulf Oil Company), Ketjenblack, EC-based materials (manufactured by Armak Company), Vulcan XC-72 (manufactured by Cabot Company), and Super P (manufactured by Timcal).

[0044] A binder is a component that helps to bond the active material to conductive materials and to current collectors. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0045] The electrode thickness according to the present invention may be 100 μm or less, specifically 20 μm to 100 μm, and more specifically 50 μm to 100 μm. When the electrode thickness satisfies the above numerical range, the electrolyte described later can be cured while impregnated to a sufficient depth in the electrode, and as a result, the reaction occurs uniformly throughout the electrode without injecting another liquid electrolyte into the electrode stack during the manufacture of the lithium secondary battery, thereby improving the capacity, output, and life characteristics of the lithium secondary battery.

[0046] (2) Step of coating the electrodes with an electrolyte solution. Next, the step of coating the electrode with an electrolyte solution will be described.

[0047] The electrolyte according to the present invention may contain monomers, initiators, lithium salts, and solvents.

[0048] Monomers are substances that can form gel electrolytes through polymerization reactions.

[0049] For example, the monomer may be, but is not limited to, ethylene glycol diacrylate, triethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate (ETPTA), bisphenol A ethoxylated dimethacrylate, acrylic acid, carboxyethyl acrylate, methyl cyanoacrylate, ethyl cyanoacrylate, ethyl cyanoethoxyacrylate, cyanoacrylic acid, hydroxyethyl methacrylate, hydroxypropyl acrylate, derivatives thereof, or combinations thereof.

[0050] The monomer may be included in an amount of 5 to 50 parts by weight, more specifically 5 to 30 parts by weight, or more specifically 5 to 20 parts by weight, per 100 parts by weight of the electrolyte. When the monomer is included within the above content range, sufficient crosslinking reactions occur between the monomers, and an electrolyte layer having a specific thickness range can be produced.

[0051] An initiator is a substance that forms an active radical to initiate a monomer polymerization reaction. Specifically, initiators can initiate free radical polymerization reactions of monomers by decomposing at room temperature (5°C to 30°C) with light such as UV, or by decomposing at temperatures between 30°C and 100°C to form radicals.

[0052] The initiator may contain at least one selected from the group consisting of photocuring agents and thermocuring agents.

[0053] If the initiator is a photocuring agent, the initiator is HMPP (2-hydroxy-2-methylpropiophenone), 1-hydroxycyclohexylphenyl ketone, benzophenone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, oxyphenylacetic acid 2-[2-oxo-2phenylacetoxyethoxy]-ethyl ester, oxyphenyl acetate 2-[2-hydroxyethoxy]-ethyl ester, α-dimethoxy-α-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1 - May contain at least one selected from the group consisting of butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl), bis[2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl]titanium, 4-isobutylphenyl-4'-methylphenyliodonium, hexafluorophosphate, and methylbenzoyl formate.

[0054] If the initiator is a thermosetting agent, the initiator may include at least one selected from the group consisting of benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide, and hydrogen peroxide, 2,2'-azobis(2-cyanobutane), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN), and 2,2'-azobisdimethyl-valeronitrile (AMVN).

[0055] The initiator may be included in an amount of 0.01 to 1 part by weight, specifically 0.05 to 0.5 parts by weight, or more specifically 0.06 to 0.1 parts by weight, per 100 parts by weight of the electrolyte. When the initiator is included within the above content range, the crosslinking reaction between monomers proceeds smoothly, an electrolyte layer can be formed with a uniform thickness, the polymerization rate in the electrolyte can be controlled, and the drawback of unreacted initiator remaining and adversely affecting the battery performance can be prevented.

[0056] Lithium salts are used as mediators for ion transfer in lithium-ion secondary batteries.

[0057] Lithium salts are substances that dissolve easily in gel electrolytes, such as LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10It may, but is not limited to, a single substance or a mixture of two or more substances selected from the group consisting of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylborate, and imide.

[0058] The lithium salt may be included in an amount of 5 to 30 parts by weight, specifically 10 to 20 parts by weight, or more specifically 10 to 15 parts by weight, per 100 parts by weight of the electrolyte. When the lithium salt is included within the above content range, the cured electrolyte can have sufficient ionic conductivity.

[0059] The solvent is used to dissolve the monomer, initiator, and lithium salt mentioned above.

[0060] The aforementioned solvents are those commonly used in secondary batteries, and may include, for example, ethers, esters (acetates, propionates), amides, linear or cyclic carbonates, and nitriles (acetonitrile, SN, etc.), each used individually or in combination of two or more.

[0061] In particular, carbonate-based solvents containing carbonate compounds such as cyclic carbonates, linear carbonates, or mixtures thereof may be used.

[0062] Specific examples of the cyclic carbonate compounds include single compounds or mixtures of at least two compounds 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, and their halides. Specific examples of the linear carbonate compounds include compounds selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC), or mixtures of at least two compounds, but are not limited to these.

[0063] In particular, among the carbonate-based solvents, propylene carbonate and ethylene carbonate, which are cyclic carbonates, are preferred because they are high-viscosity organic solvents with high dielectric constants that easily dissociate lithium salts in the electrolyte. Furthermore, when these cyclic carbonates are mixed with linear carbonates with low viscosity and low dielectric constant, such as ethyl methyl carbonate, diethyl carbonate, or dimethyl carbonate, in appropriate proportions, it is possible to produce an electrolyte with high electrical conductivity, making them even more preferable.

[0064] Furthermore, among the solvents, the ester may be a single compound selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, α-valerolactone, and ε-caprolactone, or a mixture of at least two such compounds, but is not limited to these.

[0065] The solid content in the electrolyte may be 10% to 60%, specifically 15% to 50%, or more specifically 15% to 35%. When the solid content of the electrolyte satisfies the above numerical range, the electrolyte can have a viscosity sufficient to coat the electrode active material layer. Furthermore, since the solvent is easily removed during the curing of the electrolyte, problems such as the occurrence of side reactions due to solvent residue and a decrease in the mechanical strength of the electrolyte layer can be prevented.

[0066] The viscosity of the electrolyte at 25°C may be 30 cP or less, specifically 5 cP to 30 cP, and more specifically 10 cP to 20 cP. When the viscosity of the electrolyte satisfies the above numerical range, the electrolyte can harden while impregnating the electrode to a sufficient depth, and as a result, the reaction occurs uniformly throughout the electrode without injecting another liquid electrolyte into the electrode stack during the manufacturing of the lithium secondary battery, thereby improving the capacity, output, and life characteristics of the lithium secondary battery.

[0067] Conventional coating methods can be used for coating the electrolyte, such as bar coating, spin coating, roll coating, slot die coating, hand coating, and spray coating. One of these methods may be used alone, or two or more methods may be used in combination.

[0068] (3) Step of placing an oxygen barrier member on the coated electrolyte. Next, an oxygen-blocking member is placed on the electrolyte coated on the electrode. By covering the electrolyte with the oxygen-blocking member, contact between the electrolyte and oxygen can be blocked.

[0069] The oxygen barrier may be insoluble in the solvent in order to effectively block contact between the electrolyte and oxygen. Specifically, the oxygen barrier may be insoluble in organic solvents.

[0070] For example, the oxygen barrier material may include, but is not limited to, one or more materials selected from the group consisting of glass, polypropylene (PP), and high-density polyethylene (HDPE).

[0071] The thickness of the oxygen barrier may be 100 μm to 2000 μm, more specifically 100 μm to 500 μm, or more specifically 100 μm to 200 μm. When the thickness of the oxygen barrier satisfies the above numerical range, contact between the electrolyte and oxygen is blocked, and the electrolyte can be completely cured.

[0072] (4) A step of curing the electrolyte impregnated inside the electrode and the electrolyte coated on the surface of the electrode. Next, the electrolyte impregnated inside the electrode and the electrolyte coated on the surface of the electrode are cured. In this case, the electrolyte coated on the surface of the electrode is cured, forming an electrolyte layer on the electrode.

[0073] The curing of the electrolyte may be photocuring or thermal curing. Specifically, the curing of the electrolyte involves irradiating the electrolyte, which is covered with an oxygen-blocking member, with ultraviolet light (UV) or applying heat, which causes the monomers contained in the electrolyte to crosslink. By curing the electrolyte while contact between the electrolyte and oxygen is blocked by the oxygen-blocking member, problems such as the electrolyte volatilizing or the electrolyte layer coming into contact with other electrodes and detaching can be prevented.

[0074] The electrolyte layer of the present invention may include a polymer matrix formed by crosslinking monomers and an initiator, and a lithium salt impregnated into the polymer matrix. In this case, since the electrolyte layer contains a lithium salt, it can have ionic conductivity.

[0075] The degree of hardening of the electrolyte layer may be 93% to 100%, specifically 95% to 100%, or more specifically 98% to 100%. When the degree of hardening of the electrolyte layer satisfies the above range, the electrolyte layer can be formed on the active material layer with a uniform thickness, and the phenomenon of the electrolyte layer detaching from the active material layer can be prevented.

[0076] The thickness of the electrolyte layer may be 10 μm to 200 μm, specifically 10 μm to 150 μm, and more specifically 20 μm to 80 μm. When the thickness of the electrolyte layer satisfies the above numerical range, the detachment of the electrolyte layer from the active material layer is prevented, the passage of cations (Li+), which are ion carriers, is facilitated, and the performance degradation due to the total volume of the lithium secondary battery can be minimized.

[0077] After the electrolyte has hardened, the oxygen barrier material placed on the electrolyte layer can be removed.

[0078] <Manufacturing method for lithium secondary batteries> Next, a method for manufacturing a lithium secondary battery according to the present invention will be described.

[0079] The lithium secondary battery according to the present invention includes an electrode assembly.

[0080] According to one embodiment of the present invention, an electrode assembly can be manufactured by arranging an electrode stack having an electrolyte layer formed on it and an electrode without an electrolyte layer formed on it so as to be in contact with each other. In this case, the electrode stack is as described above.

[0081] For example, the electrode assembly of the present invention can be manufactured by arranging an electrode laminate including a negative electrode and an electrolyte layer formed on the negative electrode, and a positive electrode without an electrolyte layer, so as to be in contact with each other. Alternatively, the electrode assembly of the present invention may include an electrode laminate including a positive electrode and an electrolyte layer formed on the positive electrode, and a negative electrode without an electrolyte layer. In this case, the electrolyte layer may be placed between the positive electrode and the negative electrode.

[0082] According to another embodiment of the present invention, the electrode assembly can be manufactured by arranging a plurality of the aforementioned electrode stacks such that the electrolytes are in contact with each other. By forming the electrode assembly in this manner, electrical insulation is improved and stable charging and discharging of the battery can be carried out.

[0083] The lithium secondary battery of the present invention does not need to include a separator that was placed between the positive and negative electrodes in conventional lithium secondary batteries. Specifically, the electrolyte layer included in the electrode stack of the present invention can perform the role of a conventional separator by being placed between the positive and negative electrodes.

[0084] Furthermore, the lithium secondary battery of the present invention does not need to contain the liquid electrolyte that was injected during the manufacture of conventional lithium secondary batteries. Specifically, the aforementioned electrolyte of the present invention can perform the role of a conventional liquid electrolyte by being cured while impregnated to a sufficient depth in the electrodes.

[0085] The lithium secondary battery of the present invention can be manufactured by placing the aforementioned electrode assembly into a cylindrical or rectangular battery case and sealing it. The battery case may be one of those commonly used in the art, and there are no restrictions on its external shape depending on the battery's application. For example, it may be cylindrical, rectangular, pouch-shaped, or coin-shaped, but is not limited to these.

[0086] A lithium secondary battery according to one embodiment of the present invention can be used not only as a battery cell used as a power source for small devices, but also suitably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells. Preferred examples of such medium- and large-sized devices include electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems (ESS).

[0087] Hereinafter, the present invention will be described more specifically with reference to specific examples. However, the following examples are merely illustrative for understanding the present invention and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications can be made within the scope of the description and the scope of the technical idea, and it is needless to say that such variations and modifications belong to the scope of the appended claims.

[0088] Examples and Comparative Examples Example 1 (1) Manufacture of Electrode Laminate As a negative electrode current collector, a copper (Cu) metal thin film with a thickness of 10 μm was prepared, and a 70-μm negative electrode active material layer containing artificial graphite as a negative electrode active material was formed on one surface of the copper metal thin film to manufacture a negative electrode with a total thickness of 80 μm.

[0089] A monomer, an initiator, and a lithium salt were dissolved in a solvent with a volume ratio of ethylene carbonate (EC) to propylene carbonate (PC) of 5:5 at a weight ratio of 3.98:0.04:5.98 to produce an electrolytic solution. At this time, the solid content of the electrolytic solution was 25%, and the viscosity at 25 °C was 15 cP.

[0090] The manufactured electrolytic solution was coated on the active material layer, and the coated electrolytic solution was covered with a polypropylene film. Next, ultraviolet light with a wavelength of 556 nm was irradiated on the polypropylene film for 1 minute to cure the electrolytic solution. After the curing of the electrolytic solution was completed, the polypropylene film was removed, and finally, an electrode laminate in which an electrolyte layer was formed on the electrode active material layer was manufactured. At this time, the thickness of the electrolyte layer was 40 μm.

[0091] (2) Manufacture of Lithium Secondary Battery As a positive electrode active material, a 60-μm positive electrode containing Li(Ni 0.8 Mn 0.1 Co 0.1 )O2 was prepared.

[0092] The electrolyte layer of the manufactured electrode laminate was arranged in contact with the positive electrode to manufacture an electrode assembly.

[0093] A lithium secondary battery was manufactured by placing the electrode assembly into a battery case and then sealing it.

[0094] Example 2 An electrode laminate was manufactured in the same manner as in Example 1, except that a glass plate was used instead of a polypropylene film. In this case, the thickness of the electrolyte layer was 30 μm.

[0095] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the aforementioned electrode stack was used.

[0096] Comparative Example 1 An electrode laminate was manufactured in the same manner as in Example 1, except that the electrolyte was cured without being covered with a polypropylene film. In this case, the thickness of the electrolyte layer was 10 μm.

[0097] A lithium secondary battery was manufactured in the same manner as in Example 1, except that the aforementioned electrode stack was used.

[0098] Experimental Example 1 - Evaluation of the coating properties of the electrolyte layer The surfaces of the electrode stacks manufactured in Examples 1 and 2, and Comparative Example 1, were photographed and are shown in Figures 1 to 3.

[0099] Specifically, Figure 1 is a photograph of the surface of the electrode stack manufactured in Example 1, Figure 2 is a photograph of the surface of the electrode stack manufactured in Example 2, and Figure 3 is a photograph of the surface of the electrode stack manufactured in Comparative Example 1.

[0100] Furthermore, the surface of the electrode stack was visually inspected, and the presence or absence of detachment or lifting of the electrolyte layer from the active material layer is shown in Table 1 below. X: No detachment or lifting. O: Detachment or lifting present.

[0101] [Table 1]

[0102] As shown in Table 1 and Figures 1 to 3, in Comparative Example 1, in which no oxygen-blocking member was used during the curing of the electrolyte, unlike Examples 1 and 2 in which an oxygen-blocking member was used during the curing of the electrolyte, it can be confirmed that the electrolyte layer contained in the electrode laminate detached from or lifted away from the active material layer.

[0103] Experimental Example 2 - Evaluation of whether a lithium secondary battery is operational or not. To evaluate whether the lithium secondary batteries manufactured in Examples 1 and 2 and Comparative Example 1 were operational, the capacity (mAh)-voltage (V) graphs during battery charging were measured using a Biologic SP-300. The measurement results are shown in Figures 4 to 6 attached to this document.

[0104] Figure 4 shows the capacity (mAh)-voltage (V) graph during charging of the lithium secondary battery manufactured in Example 1, Figure 5 shows the capacity (mAh)-voltage (V) graph during charging of the lithium secondary battery manufactured in Example 2, and Figure 6 shows the capacity (mAh)-voltage (V) graph during charging of the lithium secondary battery manufactured in Comparative Example 1.

[0105] As shown in Figures 4 to 6, in Comparative Example 1, where no oxygen barrier was used during electrolyte curing, it can be confirmed that the battery voltage did not increase as the battery capacity increased during charging. This means that in Comparative Example 1, the electrolyte layer, which acts as a separator, detached from the active material layer, and therefore the lithium secondary battery was not charged.

[0106] In contrast, in Examples 1 and 2, where an oxygen-blocking member was used during the curing of the electrolyte, it was confirmed that the battery voltage increased as the battery capacity increased during charging. This means that in Examples 1 and 2, the electrolyte layer, which acts as a separator, did not detach from the active material layer, and therefore the battery was able to be charged normally.

Claims

1. Steps to prepare electrodes, The steps include coating the electrode with an electrolyte solution, The steps include placing an oxygen barrier member on the coated electrolyte, A method for manufacturing an electrode laminate, comprising the steps of curing an electrolyte impregnated into the inside of the electrode and an electrolyte coated on the surface of the electrode.

2. The method for manufacturing an electrode laminate according to claim 1, wherein an electrolyte layer is formed on the electrode by hardening the electrolyte coated on the surface of the electrode.

3. The method for manufacturing an electrode laminate according to claim 1, wherein the oxygen barrier member includes one or more selected from the group consisting of glass, polypropylene (PP), and high-density polyethylene (HDPE).

4. The aforementioned electrolyte is The monomer is present in an amount of 5% to 50% by weight. The initiator is 0.01% to 1% by weight. A method for producing an electrode laminate according to claim 1, comprising 5% to 30% by weight of a lithium salt.

5. The monomers are ethylene glycol diacrylate, triethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate (ETPTA), bisphenol A ethoxylated dimethacrylate, acrylic acid, carboxyethyl acrylate, methyl cyanoacrylate, and ethyl cyanoacrylate. A method for producing an electrode laminate according to claim 4, comprising one or more selected from the group consisting of cyanoacrylate, ethyl cyanoethoxyacrylate, cyanoacrylic acid, hydroxyethyl methacrylate, and hydroxypropyl acrylate.

6. The initiators are HMPP (2-hydroxy-2-methylpropiophenone), 1-hydroxycyclohexylphenyl ketone, benzophenone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, oxyphenylacetic acid 2-[2-oxo-2phenylacetoxyethoxy]ethyl ester, oxyphenyl acetate 2-[2-hydroxyethoxy]ethyl ester, α-dimethoxy-α-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1- A method for producing an electrode laminate according to claim 4, comprising at least one selected from the group consisting of [4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl), bis[2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl]titanium, 4-isobutylphenyl-4'-methylphenyliodonium, hexafluorophosphate, and methylbenzoyl formate.

7. The method for manufacturing an electrode laminate according to claim 2, wherein the electrolyte layer is formed by photocuring or thermal curing the electrolyte.

8. The method for manufacturing an electrode laminate according to claim 1, wherein the solid content in the electrolyte is 10% to 60%.

9. The method for manufacturing an electrode laminate according to claim 1, wherein the viscosity of the electrolyte at 25°C is 30 cP or less.

10. The method for manufacturing an electrode laminate according to claim 2, wherein the thickness of the electrolyte layer is 10 μm to 200 μm.

11. The method for manufacturing an electrode laminate according to claim 1, wherein the thickness of the electrode is 100 μm or less.

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