Method for manufacturing secondary battery

Abstract

The present invention provides a method for manufacturing a secondary battery comprising: (S1) a step of housing an electrode assembly in a battery case; (S2) a step of injecting a first electrolyte composition into the battery case to impregnate the electrode assembly; (S3) a step of injecting a second electrolyte composition into the battery case; and (S4) a step of curing the second electrolyte composition; wherein an electrode tab is connected to the electrode assembly and the electrode tab is extended to the outside of the electrode assembly; the first electrolyte composition comprises a first-1 lithium salt comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a first solvent; the second electrolyte composition comprises an oligomer and a second solvent; and the second electrolyte composition does not include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a secondary battery. Background Technology

[0002] As technological development and demand for electronic devices increase, the demand for secondary batteries as an energy source is rapidly rising, and among these secondary batteries, lithium secondary batteries, which possess high energy density and voltage, have been commercialized and are widely used.

[0003] The above secondary battery can be manufactured, for example, by housing an electrode assembly in which electrodes and separators are alternately stacked and an electrode tab connected to the electrode assembly in a battery case, and injecting an electrolyte into the battery case and sealing it.

[0004] Conventionally, liquid electrolytes, particularly ion-conducting organic liquid electrolytes in which salts are dissolved in non-aqueous organic solvents, have been primarily used as electrolytes for secondary batteries. However, these liquid electrolytes present problems such as the possibility of leakage to the outside of the secondary battery, reduced safety, and decreased cell rigidity.

[0005] In this regard, research is emerging to commercialize polymer electrolytes, such as gel polymer electrolytes, instead of liquid electrolytes. The gel polymer electrolyte has advantages in that it can prevent leakage to the outside of the secondary battery and has excellent cell rigidity. However, gel polymer electrolytes have problems with high interfacial resistance and low ionic conductivity compared to liquid electrolytes.

[0006] Meanwhile, considering the reduction of resistance and thermal stability of secondary batteries, the use of lithium salts such as lithium bis(fluorosulfonyl)imide (LiFSI) is being considered, but lithium salts such as lithium bis(fluorosulfonyl)imide have a problem of corroding the electrode tabs of secondary batteries, which is a concern in terms of long-term life characteristics. The problem to be solved

[0007] One objective of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing a secondary battery that is advantageous in terms of long-term lifespan by reducing the resistance of the secondary battery, simultaneously improving cell rigidity and thermal stability, and preventing corrosion of the electrode tab. means of solving the problem

[0008] The present invention provides a method for manufacturing a secondary battery comprising: (S1) a step of housing an electrode assembly in a battery case; (S2) a step of injecting a first electrolyte composition into the battery case to impregnate the electrode assembly; (S3) a step of injecting a second electrolyte composition into the battery case; and (S4) a step of curing the second electrolyte composition; wherein an electrode tab is connected to the electrode assembly and the electrode tab is extended to the outside of the electrode assembly; the first electrolyte composition comprises a first-1 lithium salt comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a first solvent; the second electrolyte composition comprises an oligomer and a second solvent; and the second electrolyte composition does not include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Effects of the invention

[0009] The method for manufacturing a secondary battery according to the present invention is characterized by including a process of injecting an electrolyte composition in two steps. The first electrolyte composition is a liquid electrolyte and includes lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethanesulfonyl)imide as a lithium salt, contributing to the reduction of resistance and improvement of thermal stability of the secondary battery. In addition, the second electrolyte composition does not include lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide in the composition and hardens outside the electrode assembly to form a gel polymer electrolyte. Through the above-described two-step electrolyte composition injection and curing process, lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethanesulfonyl)imide can be placed only inside the electrode assembly, thereby reducing the resistance and improving the thermal stability of the secondary battery, improving cell rigidity, preventing leakage to the outside of the secondary battery, and preventing corrosion of the electrode tab, so that long-term life performance can be improved. Brief explanation of the drawing

[0010] FIG. 1 is a plan view illustrating step (S1) of the method for manufacturing a secondary battery of the present invention, showing an electrode assembly accommodated in a battery case. FIG. 2 is a side view illustrating step (S1) of the method for manufacturing a secondary battery of the present invention, showing an electrode assembly accommodated in a battery case. FIG. 3 is a schematic side view of an electrode assembly to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 4 is a schematic side view of a separator to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 5 is a schematic plan view of a separator or electrode to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 6 is a diagram illustrating the manufacturing process of an electrode assembly, and is intended to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 7 is a diagram illustrating the manufacturing process of an electrode assembly, and is intended to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 8 is a diagram illustrating the manufacturing process of an electrode assembly, and is intended to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 9 is a diagram illustrating the manufacturing process of an electrode assembly, and is intended to explain step (S1) of the method for manufacturing a secondary battery of the present invention. FIG. 10 is a plan view for explaining step (S2) of the method for manufacturing a secondary battery of the present invention, and for explaining the process of injecting the first electrolyte composition after step (S1). FIG. 11 is a side view illustrating step (S2) of the method for manufacturing a secondary battery of the present invention, and illustrating the process of injecting the first electrolyte composition after step (S1). FIG. 12 is a plan view for explaining step (S3) of the method for manufacturing a secondary battery of the present invention, and for explaining the process of injecting a second electrolyte composition after step (S2). FIG. 13 is a plan view for explaining step (S4) of the method for manufacturing a secondary battery of the present invention, and for explaining the curing process of the second electrolyte composition after step (S3). FIG. 14 is a side view illustrating step (S4) of the method for manufacturing a secondary battery of the present invention, and illustrating the curing process of the second electrolyte composition after step (S3). Figure 15 is a surface photograph of a separator included in a secondary battery manufactured from the manufacturing method of Example 1. Specific details for implementing the invention

[0011] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0012] In this specification, the average particle size (D 50 ) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. The above average particle size (D 50 ) can be measured, for example, using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0013] The secondary battery of the present invention will be described in detail below with reference to the drawings. In assigning reference numerals to the components of each drawing, the same components may have the same reference numeral as much as possible, even if they are shown in different drawings. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions could obscure the essence of the present invention, such detailed description may be omitted.

[0015] Method for manufacturing a secondary battery

[0016] The present invention relates to a method for manufacturing a secondary battery, specifically a method for manufacturing a lithium secondary battery.

[0017] The present invention provides a method for manufacturing a secondary battery comprising: (S1) a step of housing an electrode assembly in a battery case; (S2) a step of injecting a first electrolyte composition into the battery case to impregnate the electrode assembly; (S3) a step of injecting a second electrolyte composition into the battery case; and (S4) a step of curing the second electrolyte composition; wherein an electrode tab is connected to the electrode assembly and the electrode tab is extended to the outside of the electrode assembly; the first electrolyte composition comprises a first-1 lithium salt comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a first solvent; the second electrolyte composition comprises an oligomer and a second solvent; and the second electrolyte composition does not include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0019] (1) Receiving step of electrode assembly (Step S1)

[0020] Referring to FIGS. 1 and 2, first, an electrode assembly (100) is housed in a battery case (300). At this time, an electrode tab (400, 500) is connected to the electrode assembly (100), and the electrode tab (400, 500) protrudes outside the electrode assembly (100).

[0021] Hereinafter, the electrode assembly (100), battery case (300), and electrode tabs (400, 500) will be described.

[0023] electrode assembly

[0024] For convenience of explanation, FIGS. 1 and 2 briefly show the configuration of the electrode assembly (100), and an exemplary configuration of the electrode assembly (100) can be described with reference to FIGS. 3 to 9.

[0025] Referring to FIG. 3, the electrode assembly (100) can be manufactured such that electrodes (110, 120) and separators (130) are alternately stacked, and an adhesive (140) is applied to at least one surface of the electrodes (110, 120) and the separator (130) so that the electrodes (110, 120) and the separator (130) are bonded to each other.

[0026] The electrode assembly (100) includes a plurality of electrodes (110, 120) stacked in a vertical direction (P). The electrodes (110, 120) may be two or more. In this specification, “vertical direction” may mean a vertical direction relative to the ground and is intended only to describe the stacking direction of the electrodes and is not intended to limit the angle of the stacking direction.

[0027] The electrodes (110, 120) may include a first electrode (110) and a second electrode (120). As illustrated in FIG. 1, the first electrode (110) and the second electrode (120) may be stacked alternately. The electrodes (110, 120) may be stacked alternately with a separator (130) in between. The first electrode (110) may be an anode and the second electrode (120) may be a cathode. Alternatively, the first electrode (110) may be a cathode and the second electrode (120) may be an anode. The first electrode and the second electrode may each be one or more, specifically two or more.

[0028] The first electrode (110) and the second electrode (120) may have a structure in which an active material slurry is coated on a current collector. The first electrode (110) and the second electrode (120) may have a structure in which the active material slurry is coated, dried, and rolled on both sides of a current collector. The active material slurry may be formed by stirring a state in which granular active material, conductive material, binder, etc. are added to a solvent. Active material, conductive material, binder, etc. used in a positive or negative electrode in the field may be used in the first electrode (110) and the second electrode (120) without limitation.

[0029] The above current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the above current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy. For example, when the electrode (110, 120) is a positive electrode, the current collector used for the electrode (110, 120) may include aluminum, and when the electrode (110, 120) is a negative electrode, the current collector used for the electrode (110, 120) may include copper.

[0030] The above current collector can be used in various forms such as films, sheets, foils, nets, meshes, porous bodies, foams, and nonwoven fabrics. Additionally, the above current collector may include a polymer layer and metal layers disposed on both sides of the polymer layer, and the metal layer may include at least one material selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloy.

[0031] Specifically, when the electrode (110, 120) is a negative electrode, the negative electrode active material included therein may be, for example, a compound capable of reversible intercalation and deintercalation of lithium. Specific examples of negative electrode active materials include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO βExamples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes.

[0032] Additionally, specifically, when the electrode (110, 120) is a positive electrode, the positive electrode active material included therein is not particularly limited, and for example, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; lithium iron oxide such as LiFe3O4; or a compound with the chemical formula Li 1+c1 Mn 2-c1 Lithium manganese oxides such as O4 (0≤c1≤0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7, etc.; chemical formula LiNi1-c2 M c2 Ni-site type lithium nickel oxide represented by O2 (wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, satisfying 0.01≤c2≤0.3); chemical formula LiMn 2-c3 M c3 Examples include lithium manganese composite oxides represented by O2 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, satisfying 0.01≤c3≤0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn); and LiMn2O4 in which a portion of the Li in the chemical formula is substituted with alkaline earth metal ions, but are not limited thereto. The anode may also be a Li-metal anode.

[0033] The binders included in the above electrode are polyvinylidene fluoride polymer, polyvinyl alcohol, styrene butadiene rubber, polyethylene oxide, carboxyl methyl cellulose, cellulose acetate, cellulose acetate butylate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, polymethyl methacrylate, polybutylacrylate, polyacrylonitrile, and polyvinylpyrrolidone. It may be any one binder polymer selected from the group consisting of polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate copolymer, polyarylate, and low molecular weight compounds with a molecular weight of 10,000 g / mol or less, or a mixture of two or more of these.

[0034] The conductive material included in the above electrode is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, Farnes black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, 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 may be used.

[0035] An example of a thickening agent included in the above electrode is carboxymethylcellulose (CMC).

[0037] As illustrated in FIG. 3, the electrode assembly (100) may include a separator (130). The separator is alternately stacked with the electrode.

[0038] As illustrated in FIG. 3, the separator (130) may be folded or bent in a zigzag shape to wrap around one end of the electrodes (110, 120). For example, as illustrated in FIG. 1, when the first electrode (110) and the second electrode (120) are alternately stacked, the separator (130) may be folded to wrap around one end (110a) of the first electrode (110), and then folded again to wrap around one end of the second electrode (110) located opposite the one end (110a) of the first electrode (110). As this folding is repeated, the separator (130) may be folded or bent in a zigzag shape. The electrode assembly (100) may include one separator (130).

[0039] The electrode assembly (100) may be a zigzag stacked electrode assembly in which the separator (130) is folded or bent in a zigzag shape, and the first electrode (110), the separator (130), the second electrode (120), and the separator (130) are sequentially stacked in a basic unit, with one or more, specifically two or more, stacked.

[0040] As illustrated in FIG. 4, the separator (130) may include a porous substrate (131) and ceramic coating layers (132a, 132b) disposed on both sides of the porous substrate.

[0041] The porous substrate (131) is not particularly limited as long as it is typically used as a separator for a secondary battery. Specifically, the porous substrate (131) is preferably low-resistance to the movement of electrolyte ions and has excellent electrolyte moisture retention capacity. More specifically, the porous substrate (131) may include at least one selected from the group consisting of polyolefin-based resins such as polyethylene, polypropylene, polybutylene, and polypentene; fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene; polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate; polyacrylonitrile resin; and cellulose-based resin, and may be a porous film or nonwoven fabric, or a laminated structure of two or more layers thereof, comprising one or more copolymers or mixtures of any one or more of these. The porous substrate (131) may be a porous film, nonwoven fabric, or a laminated structure of two or more layers thereof comprising the polyolefin-based resin.

[0042] The pore size and porosity present in the porous substrate (131) are not particularly limited. Specifically, the porous substrate (131) may be a porous substrate containing pores with an average pore diameter of 0.01 μm to 1 μm, specifically 20 nm to 60 nm, with a porosity of 10 volume% to 90 volume%, specifically 30 volume% to 60 volume%. In this case, it is desirable in that it improves the mechanical strength of the porous substrate (131) and allows ionic materials to move more smoothly between the anode and the cathode. The average pore diameter and porosity may be measured by analysis using a focused ion beam (FIB), gas adsorption, or mercury intrusion.

[0043] The thickness of the porous substrate (131) is not particularly limited, but considering the appropriate mechanical strength as a separator and the ease of movement of ionic materials, it may be specifically 1 μm to 100 μm, specifically 2 μm to 15 μm.

[0044] The ceramic coating layers (132a, 132b) are disposed on both sides of the porous substrate (131).

[0045] The ceramic coating layer (132a, 132b) comprises inorganic particles and a binder. More specifically, the ceramic coating layer may consist only of the inorganic particles and the binder.

[0046] The above inorganic particles may be introduced to prevent thermal shrinkage of the porous substrate at high temperatures and the resulting short circuit between the anode and cathode, and the above inorganic particles may be provided as a type of spacer that maintains the physical shape of the porous substrate and minimizes thermal shrinkage.

[0047] The above-mentioned inorganic particles may be used without special restrictions as long as they are electrochemically stable within the operating voltage range of the battery (e.g., 0V to 5V based on Li / Li+) and do not cause oxidation and / or reduction reactions, i.e., electrochemical reactions. The above-mentioned inorganic particles are lithium phosphate (Li3PO4); lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3); 리튬알루미늄티타늄포스페이트(Li x Al y Ti z (PO4)3, 0 <x<2, 0<y<1, 0<z<3), 14Li2O-9Al2O3-38TiO2-39P2O5와 같은 (LiAlTiP) x O y Glass (0 <x<4, 0<y<13); 리튬란탄티타네이트(Li x La y TiO3, 0 <x<2, 0<y<3); Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x Ge y P z S w , 0 <x<4, 0<y<1, 0<z<1, 0<w<5); Li3N 등과 같은 리튬나이트라이드(Li x N y , 0 <x<4, 0<y<2); Li3PO4-Li2S-SiS2 등과 같은 SiS2계 유리(Li x Si y S z , 0 <x<3, 0<y<2, 0<z<4); LiI-Li2S-P2S5 등과 같은 P2S5계 유리(Li x P y S z , 0 <x<3, 0<y<3, 0<z<7); Al2O3; AlOOH; BaTiO3; BaSO4; MgO; CaO; CeO2; NiO; SiO2; SnO2; SrTiO3; TiO2; Y2O3; ZnO; ZrO2; Pb(Zr,Ti)O3(PZT); Pb1-x La x Zr 1-y TiyO3(PLZT); PB(Mg3Nb 2 / 3 The inorganic particles may be Al2O3; AlOOH; BaTiO3; BaSO4; MgO; CaO; CeO2; NiO; SiO2; SnO2; SrTiO3; TiO2; Y2O3; ZnO; ZrO2; Pb(Zr,Ti)O3(PZT); Pb 1-x La x Zr 1-y TiyO3(PLZT); PB(Mg3Nb 2 / 3 )O3-PbTiO3 (PMN-PT); hafnia (HfO2); may be a mixture of two or more of these, and more specifically may include at least one selected from the group consisting of Al2O3; AlOOH; BaTiO3; BaSO4; and MgO.

[0048] Average particle size (D of the above inorganic particles) 50 ) can be 0.1㎛ to 1㎛, specifically 0.2㎛ to 0.7㎛.

[0049] The above inorganic particles are included in the ceramic coating layer (132a, 132b) in an amount of 92% by weight or more and less than 100% by weight. The content of the above inorganic particles should be considered in relation to the content of the binder described later, and can be controlled to prevent a decrease in thermal stability due to thermal shrinkage of the porous substrate while preventing an increase in resistance due to an excess amount of binder. Specifically, the above inorganic particles may be included in the ceramic coating layer in an amount of 93% to 98% by weight.

[0050] The above binder may be included in the ceramic coating layer (132a, 132b) for binding inorganic particles and binding the separator and the electrode.

[0051] At this time, the binder is included in the ceramic coating layer in an amount greater than 0% by weight and less than 8% by weight. If the binder is included in an amount greater than 8% by weight, the binder may be excessively included in the ceramic coating layer, which may lead to an increase in the resistance of the secondary battery. Meanwhile, although there is a concern that the cell rigidity of the secondary battery may decrease due to a decrease in the adhesion between the electrode and the separator when the binder is included in the above-described range, as described below, the present invention can simultaneously achieve an improvement in cell rigidity and mechanical durability along with an improvement in the resistance of the secondary battery by using a combination of a separator having the above-described characteristics and a gel polymer electrolyte.

[0052] Specifically, the binder may be included in the ceramic coating layer in an amount of 2% to 7% by weight, and when within this range, the binding force of the inorganic particles can be maximized while preventing an increase in the resistance of the secondary battery.

[0053] The above binder includes a fluorine group (-F), an acrylate group (CH2=CHCOO-), a methacrylate group (CH2=C(CH3)COO-), and a vinyl acetate group ( -It may be a hydrophobic binder containing one or more hydrophobic functional groups such as CH2=CHOCO-) or nitrile groups (-C≡N); or a hydrophilic binder containing one or more polar groups such as hydroxyl groups (-OH), carboxyl groups (-COOH), maleic anhydride groups (-COOOC-), sulfonic acid groups (-SO3H), or isocyanate groups (-NCO-), and any one or more of these may be used. More specifically, the hydrophobic binder may be polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylacetate, polyethylene-covinylacetate copolymer, polyimide, polyethylene oxide, etc. In addition, the hydrophilic binder may be cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, carboxyl methyl cellulose, polyvinylalcohol, polyacrylic acid, polymaleic anhydride, or polyvinylpyrrolidone, etc.

[0054] Specifically, the binder may be an acrylic binder. The acrylic binder enables good dispersion with the inorganic particles during the manufacture of the ceramic coating layer, thereby preventing the ceramic coating layer from separating into a binder layer on top and inorganic particles on the bottom. Since such separation of layers hinders ion movement at the cathode and anode and causes an increase in resistance, using an acrylic binder as the binder allows the resistance reduction effect intended by the present invention to be exhibited at a superior level.

[0055] The above acrylic binder may include at least one selected from the group consisting of a copolymer of ethylhexyl acrylate and methyl methacrylate; polymethylmethacrylate; polyethylhexyl acrylate; polybutyl acrylate; polyacrylonitrile; and a copolymer of butyl acrylate and methyl methacrylate.

[0056] The ceramic coating layer may contain inorganic particles and a binder in a weight ratio of 92:8 or more and less than 100:0, specifically 93:7 to 98:2.

[0057] The thickness of the ceramic coating layer (132a, 132b) may be 0.1㎛ to 10㎛, specifically 0.5㎛ to 5㎛, more specifically 1.0㎛ to 2.5㎛. Since the ceramic coating layer (132a, 132b) contains a binder in the aforementioned low amount, it is possible to implement a thin separator, thereby further improving the energy density of the secondary battery and achieving low resistance. The thickness of the ceramic coating layer may refer to the thickness of a single ceramic coating layer formed on one surface of the porous substrate.

[0058] The ceramic coating layer (132a, 132b) can be manufactured by applying a composition for forming a ceramic coating layer, in which inorganic particles and a binder are dispersed in a solvent, to the porous substrate and drying it. The method of applying the composition for forming a ceramic coating layer is not particularly limited and may use dip coating, die coating, roll coating, comma coating, gravure coating, etc., and specifically, gravure coating may be used. After applying the composition for forming a ceramic coating layer, the drying method may include natural drying, reversible drying, or hot air drying.

[0059] The thickness of the separator (130) may be 1 μm to 20 μm, specifically 5 μm to 14 μm. According to the present invention, a thin separator can be implemented by reducing the binder content in the ceramic coating layer, thereby further improving the energy density of the secondary battery and achieving low resistance.

[0060] As described above, the ceramic coating layer included in the separator contains a small amount of binder, so an increase in resistance due to an excess amount of binder can be prevented. Meanwhile, in the case of the secondary battery according to the present invention, a gel polymer electrolyte is used as the electrolyte, and the gel polymer electrolyte can compensate for the decrease in cell rigidity of the secondary battery accompanying such resistance reduction. Therefore, the secondary battery manufactured from the method of manufacturing a secondary battery according to the present invention may simultaneously improve the resistance reduction, cell rigidity, and mechanical durability of the secondary battery depending on the combination of the above components.

[0062] As illustrated in FIGS. 3 and 5, the electrode assembly (100) may have an adhesive (140) applied to at least one surface of the electrode (110, 120) and the separator (130) so that the electrode (110, 120) and the separator (130) are bonded to each other.

[0063] The adhesive (140) may be introduced for bonding the electrodes (110, 120) and the separator (130). Specifically, the adhesive may be introduced to fix the alignment position of the electrodes and the separator during the process of stacking, assembling, and stacking the electrodes and the separator during the manufacturing process of the secondary battery. As described above, since the separator (130) according to the present invention has a reduced binder content, the bonding strength between the electrodes and the separator may not be sufficient during the manufacturing of the secondary battery. Therefore, the adhesive (140) can compensate for this problem to easily bond the electrodes and the separator, and prevent the separator from shifting during the manufacturing process of the electrode assembly, thereby enabling the improvement of process efficiency and quality.

[0064] The above adhesive may be an acrylate-based adhesive. By using the above acrylate-based adhesive, the dissolution and removal of the aforementioned adhesive can be easily achieved.

[0065] Specifically, the acrylate-based adhesive may comprise a copolymer comprising repeating units derived from at least one monomer selected from the group consisting of methyl methacrylate (MMA), 2-ethylhexyl acrylate (2-EHA), and 2-hydroxyethyl acrylate (2-HEA).

[0066] The weight-average molecular weight (Mw) of the copolymer may be 120,000 g / mol to 140,000 g / mol. The molecular weight of the copolymer may be measured using conventional methods known in the art. For example, the molecular weight may be measured using the end-group quantification method, which determines the molecular weight by quantitatively analyzing functional groups at the ends of molecular chains; the colligative method using physical properties such as osmotic pressure, vapor pressure lowering, boiling point elevation, and freezing point depression (membrane osmosis method, vapor pressure osmosis method, etc.); the light scattering method using light scattering; the ultracentrifugation method, which measures the molecular weight by analyzing the sedimentation velocity or concentration distribution after centrifuging a polymer solution; the viscosity method using the viscosity of the polymer solution; and gel permeation chromatography (GPC) using high-speed liquid chromatography (HPLC), etc.

[0067] The adhesive described above is used in the manufacture of an electrode assembly by bonding an electrode and a separator, and after the electrode assembly is housed in a battery case and the first electrolyte composition and / or second electrolyte composition described below, specifically the first electrolyte composition, is injected into the battery case, the adhesive may be dissolved in an organic solvent contained in the first electrolyte composition and / or second electrolyte composition, specifically the first electrolyte composition. Since the adhesive according to the present invention is dissolved and removed after being used in the manufacture of the electrode assembly, the electrode and the separator can be easily bonded without increasing the amount of binder in the separator, and furthermore, the energy density of the secondary battery can be further improved by preventing an increase in the thickness of the separator due to an increase in the amount of binder.

[0068] The adhesive may be applied in the form of multiple spaced-apart patterns. Specifically, the adhesive may be applied to at least one surface of the electrode and the separator in the form of multiple spaced-apart patterns. Specifically, the adhesive may be applied to at least one surface of the electrode and the separator in the form of multiple spaced-apart dots.

[0069] The adhesive may be removed by the injection of the first electrolyte composition described below, so that traces of adhesive application may remain on the surface of at least one of the electrodes (110, 120) and the separator (130). Specifically, when the first electrolyte composition is injected into a battery case containing the electrode assembly, the adhesive may be dissolved and removed by the organic solvent in the first electrolyte composition, leaving traces of adhesive application.

[0070] The application area of ​​the adhesive may be greater than 0% and less than or equal to 1% with respect to the surface area where the separator and the electrode come into contact, specifically 0.0001% to 0.05%. According to the above range, the electrode and the separator can be bonded with sufficient adhesive strength, and at the same time, it is desirable to prevent the problem of the adhesive being excessively applied and remaining undissolved in the solvent, thereby causing an increase in resistance.

[0072] Hereinafter, an exemplary method of manufacturing the electrode assembly is described with reference to FIGS. 6 to 9.

[0073] Specifically, referring to FIGS. 6 to 9, the electrode (110, 120) includes a first electrode (110) and a second electrode (120), and the electrode assembly (100) can be manufactured by a method including the following steps (a) to (d).

[0074] (a) a step of applying the adhesive (140) to at least a portion of the separator (130) and the first electrode (110);

[0075] (b) a step of bonding the separator (130) and the first electrode (110) through the applied adhesive (140);

[0076] (c) A step of folding one side of the separator (130) to cover the first electrode (110);

[0077] (d) a step of applying the adhesive (140) to at least a portion of the separator (130) and the second electrode (120).

[0078] (e) a step of bonding the separator (130) and the second electrode (120) through the applied adhesive (140); and

[0079] (d) A step of folding the other side of the separator (130) to cover the second electrode (120).

[0081] Referring to FIG. 6, the adhesive (140) is applied to at least a portion of the separator (130) and the first electrode (110). The application of the adhesive (140) may be achieved by applying the adhesive (140) to at least a portion of the separator (130) and the first electrode (110) using a first nozzle (1110). FIG. 6 is illustrated with the adhesive (140) applied to the separator (130), but is not limited thereto, and the adhesive (140) may be applied to at least a portion of the separator (130); the first electrode (110); or both the separator (130) and the first electrode (110).

[0082] As illustrated in FIG. 6, specifically, the separator (130) may be unwound from the separator reel (630) and placed on the upper surface of the table (700).

[0083] Referring to FIG. 7, the separator (130) and the first electrode (110) are bonded together through the applied adhesive (140).

[0084] The first electrode (110) may be formed by cutting a first electrode sheet (1101), which is unwound by a first electrode reel (610) as shown in FIG. 9, with a first cutter (810). At this time, when the first transfer device (910) transfers the first electrode (110), the first header (1010) can adsorb the first electrode. Subsequently, the first electrode (110) may be placed or positioned on the separator (130) depending on the movement of the first header (1010) and / or the table (700).

[0085] Referring to FIG. 8, one side of the separator (130) is folded to cover the first electrode (110); and the adhesive (140) can be applied to at least a portion of the separator (130) and the second electrode (120).

[0086] After the first electrode (110) is attached to the separator (130), one side of the separator (130) is folded to cover the first electrode (110). For example, the folding of the separator (130) can be achieved by moving the side of the table (700).

[0087] Meanwhile, the adhesive (140) is applied to at least a portion of the separator (130) and the second electrode (120). The application of the adhesive (140) may be achieved by applying the adhesive (140) to at least a portion of the separator (130) and the second electrode (120) using a second nozzle (1120). FIG. 8 is illustrated with the adhesive (140) applied to the separator (130), but is not limited thereto, and the adhesive (140) may be applied to at least a portion of the separator (130); the second electrode (120); or both the separator (130) and the second electrode (120).

[0088] Referring to FIG. 9, the separator (130) and the second electrode (120) are bonded together using the applied adhesive (140); and the other side of the separator (130) is folded to cover the second electrode (120).

[0089] A second electrode (120) is attached to the opposite side of the separator (130) and the first electrode (110) that are in contact with each other.

[0090] The second electrode (120) may be formed by cutting a first electrode sheet (1201), which is unwound by a second electrode reel (620) as shown in FIG. 9, with a second cutter (820). At this time, when the second transfer device (920) transfers the second electrode (120), the second header (1020) can adsorb the second electrode. Subsequently, the second electrode may be seated or adhered to the separator as the second header (1020) and / or table (700) move.

[0091] Referring to FIG. 9, after the second electrode (120) is bonded, the other side of the separator (130) is folded to cover the second electrode (120). Accordingly, the first electrode and the second electrode are alternately stacked, a separator is interposed between the first electrode and the second electrode, and the separator is folded in a zigzag shape, thereby enabling the manufacture of an electrode assembly. Subsequently, by repeating the process described above, it is possible to realize an electrode assembly in which a plurality of first electrodes and second electrodes are alternately stacked.

[0092] At this time, in the case of an electrode assembly including a separator folded in a zigzag shape as described above, a slipping phenomenon of the separator and / or electrode occurs due to the folding or bending of the separator during the manufacturing process, which leads to problems such as quality defects and reduced process efficiency. However, according to the present invention, since an adhesive is applied to bond the electrode and the separator, the slipping phenomenon of the electrode and / or separator described above can be prevented to a significant degree, and it is possible to manufacture a secondary battery with improved quality. Such application of the adhesive may be particularly desirable in terms of supplementing the adhesive strength of the separator of the present invention, which contains a low amount of binder.

[0094] electrode tab

[0095] As shown in FIGS. 1 and 2, an electrode tab (400, 500) is connected to the electrode assembly (100), and the electrode tab (400, 500) protrudes to the outside of the electrode assembly (100).

[0096] The electrode tabs (400, 500) may be in the number of cases. Specifically, the electrode tabs (400, 500) are connected to the electrodes (110, 120) of the electrode assembly (100), and more specifically, are connected to the first electrode (110) and the second electrode (120), respectively, and may protrude outside the battery case (300) to form a path through which electrons can move. Additionally, although FIGS. 1 and 2 show two electrode tabs (400, 500) arranged in different directions relative to the electrode assembly (100), they are not limited thereto and may protrude side by side in the same direction from one side of the electrode assembly (100).

[0097] The plurality of electrode tabs (400, 500) may be positive electrode tabs and negative electrode tabs, and may be connected to the positive and negative electrodes, respectively.

[0098] The electrode tab may include aluminum. As described below, since the first electrolyte composition comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide does not come into contact with the electrode tab, the risk of damage to the electrode tab due to aluminum corrosion can be significantly reduced and long-term life characteristics can be improved.

[0099] Specifically, the electrode tab includes an anode tab and a cathode tab, wherein the anode tab comprises aluminum and the cathode tab may comprise nickel.

[0101] battery case

[0102] The above battery case (300) may be provided for the purpose of accommodating an electrode assembly (100). Additionally, within the battery case (300), the first electrolyte composition (210) described later may be placed inside the electrode assembly (100), and the second electrolyte composition (220) described later may be cured and placed outside the electrode assembly (100).

[0103] The battery case (300) may be a pouch-shaped case made of a flexible material, for example, an aluminum pouch battery case.

[0104] If the battery case (300) is an aluminum pouch battery case, the battery case (300) may be formed from a pouch film laminated in the order of a polypropylene layer (PP layer), an aluminum layer, and a polyethylene terephthalate layer (PET layer) from the inside out.

[0105] The battery case (300) may include a cup portion (310) which is a receiving space for housing an electrode assembly.

[0106] The battery case (300) may include a cover (320), and after housing the electrode assembly and curing and gelling of the gel polymer electrolyte composition, the battery case (300) may be sealed with the cover to manufacture a sealed secondary battery.

[0108] (2) Injection of the first electrolyte composition and impregnation of the electrode assembly (Step S2)

[0109] Referring to FIGS. 10 and 11, a first electrolyte composition (210) is injected into the battery case (300) to impregnate the electrode assembly (100). At this time, the first electrolyte composition (210) comprises a first-1 lithium salt containing lithium bis(fluorosulfonyl)imide, a first oligomer, and a first solvent.

[0110] The first electrolyte composition (210) is introduced to be placed inside the electrode assembly (100) along with impregnation of the electrode assembly (100).

[0111] Specifically, the first electrolyte composition (210) can be injected so as not to come into contact with the electrode tab (400, 500) disposed outside the electrode assembly (100). This prevents the lithium bis(fluorosulfonyl)imide included in the first electrolyte composition (210) from coming into contact with the electrode tab (400, 500), specifically the electrode tab (400, 500) containing aluminum, thereby preventing corrosion from occurring.

[0112] The first electrolyte composition (210) is injected into the electrode assembly (100) to impregnate the electrode assembly (100). Specifically, the first electrolyte composition (210) can be injected in an amount calculated in advance, taking into account the size, volume, etc. of the electrode assembly (100), so as not to come into contact with the electrode tabs (400, 500).

[0113] The impregnation of the first electrolyte composition (210) is 10 to 30 It can be performed at a temperature of 0.5 to 72 hours, preferably 15 to 30 It can be carried out for 40 to 65 hours at the temperature.

[0114] The first electrolyte composition (210) comprises a first-1 lithium salt, a first oligomer, and a first solvent, comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI, LiN(FSO2)2) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiN(CF3SO2)2).

[0115] The lithium bis(fluorosulfonyl)imide and / or lithium bis(trifluoromethanesulfonyl)imide that may be included in the above 1-1 lithium salt are injected into the electrode assembly, so they have the advantage of not only reducing the resistance of the electrode assembly but also improving the thermal stability of the secondary battery. Meanwhile, since the second electrolyte composition injected and placed outside the electrode assembly does not contain lithium bis(fluorosulfonyl)imide, the possibility of lithium bis(fluorosulfonyl)imide coming into contact with the electrode tabs (400, 500) is significantly reduced, thereby preventing corrosion of the electrode tabs.

[0116] The above-mentioned lithium salt 1-1 may be included in the above-mentioned first electrolyte composition at a molar concentration of 0.5 M or more, specifically 0.65 M or more. When within this range, the effects of reducing resistance and improving thermal stability of the secondary battery can be more preferably realized. The upper limit of the molar concentration of the above-mentioned lithium salt 1-1 is not specifically limited and may be 5 M or less in terms of easy dissolution of the lithium salt 1-1. In this specification, molar concentration refers to the molar content of a component relative to the volume of the composition, and the unit “M” of “molar concentration” may mean “mol / L”.

[0117] The first electrolyte composition may further include a first-2 lithium salt together with the first-1 lithium salt for the purpose of additional resistance reduction and corrosion prevention effects.

[0118] The above-mentioned first- and second lithium salts are lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonate (LiSbF6), lithium tetraoxoaluminate (LiAlO4), lithium tetrachloroaluminate (LiAlCl4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium nonafluorobutanesulfonate (LiC4F9SO3), lithium chloride (LiCl), lithium iodide (LiI), lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI, LiN(C2F5SO2)2), lithium fluoroalkyl borate (LiFAB) and lithium It may include at least one selected from the group consisting of 2-trifluoromethyl-4,5-dicyanomidazole (LiTDI), and specifically may include LiPF6.

[0119] In the first electrolyte composition above, the ratio of the molar concentration of the first-1 lithium salt and the molar concentration of the first-2 lithium salt may be 0.9:1 to 10:1, and when within this range, the resistance of the secondary battery can be improved while the thermal stability of the secondary battery can be improved to a desirable level. In the first electrolyte composition above, the ratio of the molar concentration of the first-1 lithium salt and the molar concentration of the first-2 lithium salt may be more specifically 0.9:1 to 5:1, and even more specifically 0.9:1 to 1.2:1.

[0120] In the first electrolyte composition above, the sum of the molar concentrations of the first-1 lithium salt and the first-2 lithium salt may be 0.7M or more, specifically 1.2M or more. When within this range, the resistance of the secondary battery can be improved, and the thermal stability of the secondary battery can be improved to a desirable level. The upper limit of the sum of the molar concentrations of the first-1 lithium salt and the first-2 lithium salt is not particularly limited and may be 5M or less, specifically 1.8M or less.

[0121] The first solvent described above may be used for the purpose of dissolving or dispersing the lithium salt of the first-1 described above. The first solvent may be an organic solvent.

[0122] The first solvent mentioned above is one commonly used in secondary batteries, and for example, ether, ester (acetate, propionate), amide, linear carbonate or cyclic carbonate, nitrile (acetonitrile, SN, etc.), etc., can be used individually or in a mixture of two or more types.

[0123] Among these, a carbonate-based solvent comprising a carbonate compound that is typically a cyclic carbonate, a linear carbonate, or a mixture thereof can be used as the first solvent.

[0124] Specific examples of the above-mentioned cyclic carbonate compounds include a single compound 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, or a mixture of at least two of these. Additionally, specific examples of the above-mentioned linear carbonate compounds may include, but are not limited to, compounds selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC), or a mixture of at least two of these.

[0125] In particular, among the carbonate-based solvents mentioned above, propylene carbonate and ethylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents with high dielectric constants that effectively dissociate lithium salts in the electrolyte, so they can be used preferably. Furthermore, if low-viscosity, low-dielectric constant linear carbonates such as ethylmethyl carbonate, diethyl carbonate, or dimethyl carbonate are mixed with these cyclic carbonates in appropriate proportions, an electrolyte with high electrical conductivity can be produced, making it even more preferable to use.

[0126] In addition, as the ester in the first solvent, 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 types, may be used, but is not limited thereto.

[0127] The first electrolyte composition (210) can be used to form a liquid electrolyte that is impregnated inside an electrode assembly. By placing a liquid electrolyte, rather than a gel polymer electrolyte, inside the electrode assembly, it is possible to reduce the resistance of the secondary battery. The first electrolyte composition (210) may not include an oligomer for forming a gel polymer electrolyte.

[0129] (3) Injection of the second electrolyte composition (Step S3)

[0130] Referring to FIG. 12, after step (S2), a second electrolyte composition (220) is injected into the battery case (300). At this time, the second electrolyte composition (220) includes an oligomer and a second solvent, and the second electrolyte composition (220) does not include lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

[0131] As illustrated in FIG. 12, the second electrolyte composition (220) injected into the battery case (300) may be injected outside the electrode assembly (100). Since the second electrolyte composition (220) does not contain lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide, it may not cause corrosion problems on the electrode tabs (400, 500) present outside the electrode assembly (100).

[0132] The second electrolyte composition (220) includes an oligomer and a second solvent. By including the oligomer, the second electrolyte composition can form a gel polymer electrolyte (220a).

[0133] The above oligomer can be polymerized and crosslinked by the curing process of the second electrolyte composition.

[0134] The above oligomer may include one or more selected from the group consisting of polyether-based oligomers, polycarbonate-based oligomers, acrylate-based oligomers, polysiloxane-based oligomers, phosphazene-based oligomers, polyethylene-based oligomers, urethane-based oligomers, epoxy-based oligomers, fluorine-based oligomers, polyethylene oxide, polyester sulfide, polyvinyl alcohol, and polyvinylidene fluoride, specifically at least one selected from fluorine-based oligomers, polycarbonate-based oligomers, and polysiloxane-based oligomers.

[0135] For example, the above-mentioned fluorine-based oligomer may specifically include units derived from fluorine-based monomers. The above-mentioned fluorine-based oligomer has the advantage of further improving battery stability by suppressing the generation of oxygen radicals caused by the decomposition of the cathode active material through the fluorine-based functional groups included therein, and also has excellent flame retardancy. More specifically, the above-mentioned fluorine-based oligomer may include at least one selected from tetrafluoroethylene (TFE)-vinyl acetate copolymer, (allyl 1,1,2,2-tetrafluoroethyl ether)-(2,2,2-trifluoroethyl acrylate) copolymer, tetrafluoroethylene-(2-vinyl-1,3-dioxolane) copolymer, and tetrafluoroethylene-vinyl methacrylate copolymer.

[0136] In addition, the polycarbonate-based oligomer has the advantages of being affinity for the anode, having a structure similar to an organic electrolyte, and having excellent ionic conductivity or ionic dissociation. The polycarbonate-based oligomer may be a polycarbonate having a weight-average molecular weight of 1,000 g / mol to 50,000 g / mol, specifically 4,500 g / mol to 30,000 g / mol, and more specifically 10,000 g / mol to 25,000 g / mol.

[0137] In addition, the above polysiloxane-based oligomer can function as a scavenger for gases (such as HF) generated by side reactions in the electrolyte, and accordingly, can have the effect of improving high-temperature storage characteristics.

[0138] The weight-average molecular weight of the above oligomer may be 1,000 g / mol to 50,000 g / mol, specifically 4,500 g / mol to 30,000 g / mol.

[0139] The above oligomer may be included in the second electrolyte composition in an amount of 0.1% to 30% by weight, specifically 1% to 10% by weight, and when in this range, the second electrolyte composition disposed outside the electrode assembly is cured, thereby improving the rigidity of the secondary battery, preventing leakage of the secondary battery, and further improving the safety of the secondary battery.

[0140] The type of the second solvent may be the same as that exemplified in the first solvent above. However, the first solvent and the second solvent may be the same or different.

[0141] The above second electrolyte composition (220) may further include a second lithium salt to improve the resistance of the secondary battery.

[0142] The above second lithium salt is lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonate (LiSbF6), lithium tetraoxoaluminate (LiAlO4), lithium tetrachloroaluminate (LiAlCl4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium nonafluorobutanesulfonate (LiC4F9SO3), lithium chloride (LiCl), lithium iodide (LiI), lithium bis(oxalato)borate (LiBOB, LiB(C2O4)2), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI, LiN(C2F5SO2)2), lithium fluoroalkyl borate (LiFAB) and lithium It may include at least one selected from the group consisting of 2-trifluoromethyl-4,5-dicyanomidazole (LiTDI), specifically LiPF6. In this case, the second lithium salt may not include lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide in order to prevent corrosion of the electrode tab.

[0143] The second lithium salt may be included in the second electrolyte composition at a molar concentration of 0.1M to 3.0M, specifically 0.5M to 1.5M, in terms of improving the resistance of the secondary battery.

[0145] (4) Curing of the second electrolyte composition (Step S4)

[0146] Referring to FIGS. 13 and 14, the second electrolyte composition (220) is cured. The second electrolyte composition (220) injected into the battery case (300) can be cured to form a gel polymer electrolyte (220a).

[0147] As shown in FIGS. 13 and 14, after step (S4), the gel polymer electrolyte (220a) formed from the second electrolyte composition (220) can be placed outside the electrode assembly (100).

[0148] The curing of the second electrolyte composition (220) can be performed by photocuring, thermal curing, etc., and specifically by thermal curing.

[0149] The second electrolyte composition (220) can be cured in the presence of a polymerization initiator. The polymerization initiator can be used for the purpose of polymerizing the oligomers contained in the second electrolyte composition to form a polymer network combined into a three-dimensional structure.

[0150] The above polymerization initiator may be included in the second electrolyte composition (220). A curing process may be performed on the second electrolyte composition according to the radical formation by the above polymerization initiator.

[0151] Meanwhile, the polymerization initiator is not included in the second electrolyte composition (220) but is added to the battery case (300) in a separate process to assist in the curing of the second electrolyte composition (220). Specifically, the method for manufacturing a secondary battery according to the present invention may further include a step of injecting the polymerization initiator into the battery case (100) before performing step (S4), specifically after performing step (S3) and before performing step (S4). According to this, pre-gelation, in which the second electrolyte composition is cured by randomly generated radicals without the polymerization initiator, can be prevented, which is desirable in that it enables sufficient impregnation of the electrode assembly and smooth control of the secondary battery manufacturing process.

[0152] The above polymerization initiator may be a photopolymerization initiator or a thermal polymerization initiator depending on the polymerization method.

[0153] Specifically, representative examples of the above photopolymerization initiators include 2-hydroxy-2-methylpropiophenone (HMPP), 1-hydroxy-cyclohexylphenyl-ketone, benzophenone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, oxy-phenylacetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic 2-[2-hydroxyethoxy]-ethyl ester, alpha-dimethoxy-alpha-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and diphenyl It may include at least one compound selected from the group consisting of (2,4,6-trimethylbenzoyl)-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(etha 5-2,4-cyclopentadiene-1-yl), bis[2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl]titanium, 4-isobutylphenyl-4'-methylphenyliodonium, hexafluorophosphate, and methyl benzoyl formate.

[0154] In addition, the above thermal polymerization initiator is, as a representative example, 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; 2,2'-Azobis(iso-butyronitrile)), and 2,2'-azobisdimethyl-valeronitrile (AMVN; It may include at least one compound selected from the group consisting of 2,2'-Azobisdimethyl-Valeronitrile).

[0155] The above polymerization initiator can decompose by heat of 30°C to 100°C within the secondary battery or by light such as UV at room temperature (5°C to 30°C) to form radicals, and can form cross-links through free radical polymerization to enable the polymerization of oligomers.

[0156] The above curing can be performed at a temperature of 50°C to 100°C for 0.5 hours to 48 hours, and preferably at a temperature of 60°C to 80°C for 0.5 hours to 24 hours.

[0157] Meanwhile, the above curing can be performed while the battery case (300) is sealed. For example, the second electrolyte composition (220) can be heat-cured by heat treatment after sealing the battery case (300), in which the electrode assembly (100), the first electrolyte composition (210), and the second electrolyte composition (220) are housed, with a cover (310) or the like.

[0158] After step (S4) above, the first electrolyte composition (210) is placed inside the electrode assembly (100), and the second electrolyte composition (220) is cured to form a gel polymer electrolyte (220a), and the gel polymer electrolyte (220a) can be placed outside the electrode assembly (100). The first electrolyte composition can impregnate the inside of the electrode assembly to achieve a reduction in the resistance of the secondary battery, and the second electrolyte composition can form a gel polymer electrolyte outside the electrode assembly to improve cell rigidity and prevent leakage of the electrolyte. In addition, since the first electrolyte composition (210) includes lithium bis(fluorosulfonyl)imide but the second electrolyte composition (220) does not include lithium bis(fluorosulfonyl)imide, it is possible to achieve a reduction in the resistance of the secondary battery and improve thermal stability, while simultaneously effectively preventing corrosion of the electrode tab.

[0160] After step (S4) above, a process of cooling the cured second electrolyte composition may be further performed. The cooling may be performed, for example, by leaving the cured second electrolyte composition at room temperature.

[0162] After the above step (S4), the battery case (300) can be sealed, and the inside of the battery case (300) can be formed into a vacuum atmosphere. With the formation of the vacuum atmosphere, degassing of gases, etc., generated during curing can be performed.

[0164] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0166] Examples and Comparative Examples

[0167] Example 1

[0168] 1. Manufacture of separator membranes

[0169] Al2O3 as inorganic particles (average particle size (D 50 A composition for forming a ceramic coating layer was prepared by adding an acrylic binder and a 0.5㎛ (0.5㎛) and an acrylic binder to water, which is the solvent, in a weight ratio of 96:4. As the acrylic binder, a mixture of JSR’s product name TRD 202A and APEC’s product name AP-0821 was used.

[0170] A separator (thickness: 12㎛ = 1.5㎛ + 9㎛ + 1.5㎛) was prepared by applying the composition for forming the ceramic coating layer to both sides of a polyethylene porous substrate (thickness: 9㎛, average pore diameter: 0.05㎛, porosity: 45% by gravure coating) and drying it to form a ceramic coating layer (thickness of one layer: 1.5㎛).

[0172] 2. Manufacture of electrode assembly

[0173] The separator reel wound with the separator was unwound, and the separator was placed on the table. An adhesive was applied to the separator using a first nozzle in a pattern of multiple spaced-apart dots. The application area of ​​the adhesive (5.8875 mm²) 2 ) is the surface area where the separator and the anode come into contact (24,889 mm 2 It was 0.002366% with respect to ). The adhesive was an acrylate-based adhesive, which is a copolymer containing repeating units derived from methyl methacrylate (MMA), 2-ethylhexyl acrylate (2-EHA), and 2-hydroxyethyl acrylate (2-HEA) in a weight ratio of 40:30:30. Subsequently, after unwinding the anode sheet from the first electrode reel on which it was wound, the anode was manufactured by cutting it with a first cutter, and the anode was transferred to a first transfer device and adsorbed onto a first header. The first header was moved toward the table side to attach the anode onto the separator.

[0174] Afterwards, the table was moved to the side, and the separator was folded to one side to cover the anode.

[0175] Subsequently, the same adhesive used above was applied to the surface of the separator (the side opposite to the surface where the separator contacts the anode) using a second nozzle in a pattern of multiple spaced-apart dots.

[0176] Afterward, the cathode sheet was unwound from the second electrode reel and cut with a second cutter to manufacture the cathode, and the cathode was transferred to a second transfer device and adsorbed onto a second header. The second header was moved toward the table side to attach the cathode to the surface of the separator (the side opposite to the surface where the separator and the anode come into contact).

[0177] Afterwards, the table was moved to the side again to fold the separator to the other side and cover the cathode.

[0178] By repeating the above process several times, an electrode assembly was manufactured in which 18 basic units, each having a separator / anode / separator / cathode sequentially stacked, were stacked. At this time, the separator was folded in a zigzag shape.

[0179] At this time, an aluminum electrode tab (anode tab) was connected to the anode, and a nickel electrode tab (cathode tab) was connected to the cathode.

[0180] In this case, for the anode, Li[Ni 0.8 Co 0.1 Mn 0.1 An anode slurry was prepared by adding O2, PVdF as a binder, and carbon black as a conductive material to N-methylpyrrolidone (NMP) as a solvent in a weight ratio of 97.5:1.5:1.0, and the anode slurry was applied to both sides of an aluminum current collector as an anode current collector, and then dried and rolled to form an anode active material layer, which was used.

[0181] In addition, for the cathode, a cathode slurry was prepared by adding graphite as a cathode active material, styrene-butadiene rubber as a binder, carbon black as a conductive material, and carboxymethylcellulose (CMC) as a thickener to water as a solvent in a weight ratio of 95.5:2.5:1.0:1.0, and the cathode slurry was applied to both sides of a copper current collector as a cathode current collector, and a cathode active material layer was formed by drying and rolling.

[0183] 3. Preparation of electrolyte composition

[0184] (1) Preparation of the first electrolyte composition

[0185] A first electrolyte composition was prepared by adding lithium bis(fluorosulfonyl)imide (LiFSI) as the first lithium salt and LiPF6 as the second lithium salt to a solvent (a mixture of ethyl carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7) so that the molar concentrations were 0.7M and 0.3M, respectively.

[0186] (2) Preparation of the second electrolyte composition

[0187] LiPF6 was added to the second electrolyte composition as a second lithium salt to a molar concentration of 1.0 M relative to the second electrolyte composition, trimethylolpropane triacrylate was added to the solvent (a mixture of ethyl carbonate (EC) and ethylmethyl carbonate (EMC) in a volume ratio of 3:7) as an oligomer to a concentration of 5% by weight of the second electrolyte composition, and AIBN (Azobisisobutyronitrile) was added as a polymerization initiator to a concentration of 0.02% by weight relative to the weight of the second electrolyte composition to prepare the second electrolyte composition.

[0189] 4. Manufacturing of secondary batteries

[0190] A pouch-type battery case made of aluminum was prepared as the battery case, and an electrode assembly was housed in the receiving space of the battery case. At this time, the positive electrode tab and the negative electrode tab were connected to the electrode assembly and positioned to protrude outside the electrode assembly.

[0191] Subsequently, the amount of the first electrolyte composition was calculated and adjusted so that only the electrode assembly could be impregnated, the first electrolyte composition was injected into the battery case, and the electrode assembly was impregnated. After injecting the first electrolyte composition, the inside of the electrode assembly was vacuum-sealed and impregnated at room temperature for 60 hours.

[0192] Subsequently, the second electrolyte composition was injected so as to be placed outside the electrode assembly. After injecting the second electrolyte composition, the battery case was vacuum sealed.

[0193] Subsequently, the second electrolyte composition injected into the battery case was cured to form a gel polymer electrolyte. The curing was performed by heat treatment at a temperature of 65°C for 5 hours.

[0194] Subsequently, the battery case was cooled, sealed, and degassing to manufacture a secondary battery.

[0195] Meanwhile, upon the injection of the first electrolyte composition, the adhesive present in the electrode assembly was dissolved and removed by the solvent of the first electrolyte composition. As described below, the adhesive was removed, leaving traces of adhesive application on the separator and the electrode.

[0197] Example 2

[0198] A first electrolyte composition was prepared in the same manner as in Example 1, except that the first-1 lithium salt and the first-2 lithium salt were added to the solvent to achieve molar concentrations of 0.7M and 0.7M, respectively.

[0199] A secondary battery was manufactured in the same manner as in Example 1, except that the first electrolyte composition prepared above was used.

[0201] Example 3

[0202] A first electrolyte composition was prepared in the same manner as in Example 1, except that the first-1 lithium salt and the first-2 lithium salt were added to the solvent to molar concentrations of 0.6M and 0.2M, respectively.

[0203] A secondary battery was manufactured in the same manner as in Example 1, except that the first electrolyte composition prepared above was used and the process of adding an additional lithium salt was not performed.

[0205] Example 4

[0206] A secondary battery was manufactured in the same manner as in Example 1, except that the second lithium salt was not added to the second electrolyte composition.

[0208] Example 5

[0209] A secondary battery was manufactured in the same manner as in Example 2, except that the second lithium salt was not added to the second electrolyte composition.

[0211] Comparative Example 1

[0212] 1. Preparation of electrolyte composition

[0213] An electrolyte composition was prepared in the same manner as the first electrolyte composition of Example 1, except that the first-1 lithium salt was not used and the first-2 lithium salt (LiPF6) was added to the solvent to a molar concentration of 1.0 M.

[0215] 2. Manufacturing of secondary batteries

[0216] A pouch-type battery case made of aluminum was prepared as the battery case, and an electrode assembly was housed in the receiving space of the battery case. At this time, the positive electrode tab and the negative electrode tab were connected to the electrode assembly and positioned to protrude outside the electrode assembly. The battery case, electrode assembly, positive electrode tab, and negative electrode tab used above are the same as those used in Example 1.

[0217] Afterwards, the electrolyte composition prepared above was injected into the internal space of the battery case and vacuum sealed to impregnate the inside of the electrode assembly at room temperature for 60 hours.

[0218] Subsequently, the battery case was cooled, sealed, and degassing to manufacture a secondary battery.

[0219] The manufacturing of the secondary battery prepared above differs from Example 1 in that it does not use two different types of electrolyte compositions, but rather injects one type of electrolyte composition into the battery case in a single step, and uses only a liquid electrolyte without applying a gel polymer electrolyte.

[0221] Comparative Example 2

[0222] 1. Preparation of electrolyte composition

[0223] An electrolyte composition was prepared in the same manner as the first electrolyte composition of Example 1, except that the first-2 lithium salt was not used and the first-1 lithium salt (LiFSI) was added to the solvent to a molar concentration of 1.0 M.

[0225] 2. Manufacturing of secondary batteries

[0226] A pouch-type battery case made of aluminum was prepared as the battery case, and an electrode assembly was housed in the receiving space of the battery case.

[0227] Afterwards, the electrolyte composition prepared above was injected into the internal space of the battery case and vacuum sealed to impregnate the inside of the electrode assembly at room temperature for 60 hours.

[0228] Subsequently, the battery case was cooled, sealed, and degassing to manufacture a secondary battery.

[0229] The manufacturing of the secondary battery prepared above differs from Example 1 in that it does not use two different types of electrolyte compositions, but rather injects one type of electrolyte composition into the battery case in a single step, and uses only a liquid electrolyte without applying a gel polymer electrolyte.

[0231] Comparative Example 3

[0232] 1. Preparation of electrolyte composition

[0233] An electrolyte composition was prepared in the same manner as the first electrolyte composition of Example 1, except that the first-1 lithium salt and the first-2 lithium salt were added to the solvent to molar concentrations of 0.3M and 0.7M, respectively.

[0235] 2. Manufacturing of secondary batteries

[0236] A pouch-type battery case made of aluminum was prepared as the battery case, and an electrode assembly was housed in the receiving space of the battery case.

[0237] Afterwards, the electrolyte composition prepared above was injected into the internal space of the battery case and vacuum sealed to impregnate the inside of the electrode assembly at room temperature for 60 hours.

[0238] Subsequently, the battery case was cooled, sealed, and degassing to manufacture a secondary battery.

[0239] The manufacturing of the secondary battery prepared above differs from Example 1 in that it does not use two different types of electrolyte compositions, but rather injects one type of electrolyte composition into the battery case in a single step, and uses only a liquid electrolyte without applying a gel polymer electrolyte.

[0241] Experimental Example

[0242] 1. Observation of adhesive application traces on the separator surface

[0243] The separator corresponding to the surface where the electrode and the separator were in contact in the secondary battery of Example 1 was cut, and its surface was observed. A photograph of the surface of the separator separated from the secondary battery of Example 1 is shown in Fig. 15.

[0244] As can be seen in Fig. 15, traces of adhesive application were observed on the surface photograph of the separator of Example 1.

[0246] 2. Resistance Evaluation

[0247] In the secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 3, the resistance value was calculated using the voltage change amount (ΔV) measured when discharged for 10 seconds at a rate of 2.5C at 50% SOC.

[0248] When the resistance value of the secondary battery of Comparative Example 1 is set to 100%, the relative ratios of the resistance values ​​of the secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0250] 3. Observation of tap corrosion

[0251] After fully charging the secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3, they were stored at 60°C for 2 weeks, and then visually observed whether corrosion had occurred on the positive electrode tab. Five secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 3 were prepared for each, and the experiment was performed 5 times.

[0252] If no corrosion occurred on the anode tab, it was evaluated as "Pass", and if corrosion occurred, it was evaluated as "Fail". The results are shown in Table 1, which shows the number of times "Pass" was evaluated out of the total number of experiments (indicated as Total, 5 times).

[0254] 4. Measurement of leakage amount

[0255] The amount of electrolyte leakage was measured for Examples 1 to 5 and Comparative Examples 1 to 3. A 5 cm incision was made in the side of each secondary battery, and the amount of electrolyte leakage from each secondary battery was measured after leaving it for 3 days with the incision facing downward. The results are shown in Table 1 below.

[0257] Experimental Example 2 Experimental Example 3 Experimental Example 4 Comparative Example 1 Relative ratio (%) to resistance value Tap Corrosion Observation (Pass / Total) Measurement of leakage amount Example 1 93.3 0 / 5 Less than 1g Example 2 92.2 0 / 5 Less than 1g Example 3 98.1 0 / 5 Less than 1g Example 4 93.9 0 / 5 Less than 1g Example 5 93.1 0 / 5 Less than 1g Comparative Example 1 100.0 0 / 5 15.1g Comparative Example 2 91.2 5 / 5 17.3g Comparative Example 3 97.4 5 / 5 12.3g

[0259] Referring to Table 1, the secondary batteries of Examples 1 to 5 had reduced resistance, no tab corrosion was observed, and almost no electrolyte leakage occurred.

[0260] However, in the case of Comparative Example 1, since lithium bis(fluorosulfonyl)imide was not used, corrosion of the electrode tab did not occur, but the resistance increased significantly, and since the gel polymer electrolyte was not placed outside the electrode assembly, a significant amount of electrolyte leakage occurred outside the secondary battery.

[0261] In addition, Comparative Examples 2 and 3 are undesirable because the lithium bis(fluorosulfonyl)imide is placed outside the electrode assembly and comes into contact with the electrode tab, so corrosion of the electrode tab is observed, and a significant amount of electrolyte leakage occurs outside the secondary battery because the gel polymer electrolyte is not placed outside the electrode assembly. Explanation of the symbols

[0263] 100: Electrode assembly U: Basic unit 110: First electrode 110a: One end of the first electrode 120: Second electrode 120a: One end of the second electrode 130: Separator 131: Porous substrate 132a, 132b: Ceramic coating layer 140: Applied adhesive 210: First electrolyte composition 220: Second electrolyte composition 220a: Gel polymer electrolyte 300: Battery case 310: Cup 320: Cover 400, 500: Electrode tabs 610: First electrode reel 620: Second electrode reel 630: Separator Reel 700: Table 810: 1st Cutter 820: 2nd Cutter 910: First transfer device 920: Second transfer device 1010: 1st header 1020: 2nd header 1101: First electrode sheet 1201: Second electrode sheet 1110: 1st nozzle 1120: 2nd nozzle

Claims

Claim 1 (S1) a step of housing the electrode assembly in a battery case; (S2) a step of injecting a first electrolyte composition into the battery case to impregnate the electrode assembly; (S3) a step of injecting a second electrolyte composition into the battery case; A method for manufacturing a secondary battery comprising: (S4) a step of curing the second electrolyte composition; wherein an electrode tab is connected to the electrode assembly and the electrode tab is extended to the outside of the electrode assembly; the first electrolyte composition comprises a first-1 lithium salt comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a first solvent; the second electrolyte composition comprises an oligomer and a second solvent; the second electrolyte composition does not comprise lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); the first electrolyte composition is injected so as not to come into contact with the electrode tab, and the second electrolyte composition is injected to the outside of the electrode assembly. Claim 2 In claim 1, the first electrolyte composition comprises lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonate (LiSbF6), lithium tetraoxoaluminate (LiAlO4), lithium tetrachloroaluminate (LiAlCl4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium nonafluorobutanesulfonate (LiC4F9SO3), lithium chloride (LiCl), lithium iodide (LiI), lithium bis(oxalato)borate (LiB(C2O4)2), lithium bis(pentafluoroethanesulfonyl)imide (LiN(C2F5SO2)2), lithium fluoroalkyl borate (LiFAB), and lithium 2-trifluoromethyl-4,5-dicyanomidazole (LiTDI). A method for manufacturing a secondary battery further comprising a first- and second lithium salt comprising at least one selected from the group formed. Claim 3 Claim 2, wherein the first and second lithium salts comprise LiPF6, a method for manufacturing a secondary battery. Claim 4 A method for manufacturing a secondary battery according to claim 2, wherein in the first electrolyte composition, the ratio of the molar concentration of the first-1 lithium salt to the molar concentration of the first-2 lithium salt is 0.9:1 to 10:

1. Claim 5 A method for manufacturing a secondary battery according to claim 2, wherein the sum of the molar concentrations of the first-1 lithium salt and the first-2 lithium salt is 0.7M or more. Claim 6 In claim 1, the second electrolyte composition further comprises a second lithium salt, wherein the second lithium salt is lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonate (LiSbF6), lithium tetraoxoaluminate (LiAlO4), lithium tetrachloroaluminate (LiAlCl4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium nonafluorobutanesulfonate (LiC4F9SO3), lithium chloride (LiCl), lithium iodide (LiI), lithium bis(oxalato)borate (LiB(C2O4)2), lithium bis(pentafluoroethanesulfonyl)imide (LiN(C2F5SO2)2), lithium fluoroalkyl borate (LiFAB), and lithium A method for manufacturing a secondary battery comprising at least one selected from the group consisting of 2-trifluoromethyl-4,5-dicyanomidazole (LiTDI). Claim 7 A method for manufacturing a secondary battery according to claim 1, wherein the oligomer is included in the second electrolyte composition in an amount of 0.1% to 30% by weight. Claim 8 A method for manufacturing a secondary battery according to claim 1, wherein the oligomer comprises at least one selected from the group consisting of a fluorine-based oligomer, a polycarbonate-based oligomer, and a polysiloxane-based oligomer. Claim 9 A method for manufacturing a secondary battery according to claim 1, wherein the second electrolyte composition further comprises a polymerization initiator. Claim 10 Claim 1, a method for manufacturing a secondary battery wherein the electrode tab comprises aluminum. Claim 11 delete Claim 12 delete Claim 13 A method for manufacturing a secondary battery according to claim 1, wherein after step (S4), the first electrolyte composition is disposed inside the electrode assembly, the second electrolyte composition is cured to form a gel polymer electrolyte, and the gel polymer electrolyte is disposed outside the electrode assembly. Claim 14 A method for manufacturing a secondary battery according to claim 1, wherein the electrode assembly has electrodes and separators alternately stacked, and an adhesive is applied to the surface of at least one of the electrodes and the separators so that the electrodes and the separators are bonded to each other. Claim 15 A method for manufacturing a secondary battery according to claim 14, wherein the separator comprises a porous substrate and a ceramic coating layer disposed on both sides of the porous substrate, and the ceramic coating layer comprises 92% by weight or more and less than 100% by weight of inorganic particles and more than 0% by weight or less of a binder. Claim 16 A method for manufacturing a secondary battery according to claim 15, wherein the binder comprises an acrylic binder. Claim 17 A method for manufacturing a secondary battery according to claim 14, wherein the adhesive is an acrylate-based adhesive. Claim 18 A method for manufacturing a secondary battery according to claim 14, wherein the adhesive is applied in the form of a plurality of spaced-apart patterns. Claim 19 A method for manufacturing a secondary battery according to claim 14, wherein the adhesive dissolves in the first electrolyte composition upon injection of the first electrolyte composition. Claim 20 A method for manufacturing a secondary battery according to claim 19, wherein, after the adhesive is dissolved, traces of adhesive application exist on the surface of the separator and one of the electrodes. Claim 21 A method for manufacturing a secondary battery according to claim 14, wherein the electrode comprises a first electrode and a second electrode, and the electrode assembly is manufactured by a method comprising the following steps (a) to (d): (a) applying the adhesive to at least a portion of the separator and the first electrode; (b) bonding the separator and the first electrode through the applied adhesive; (c) folding one side of the separator to cover the first electrode; (d) applying the adhesive to at least a portion of the separator and the second electrode; (e) bonding the separator and the second electrode through the applied adhesive; and (d) folding the other side of the separator to cover the second electrode.

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