Secondary battery containing heterogeneous gel polymer electrolyte and method for manufacturing the same

Abstract

This specification relates to a gel polymer secondary battery that is selectively permeable to only lithium ions within the cell while maintaining a state in which different electrolytes are separated. The present specification discloses a gel polymer secondary battery that includes: a positive electrode impregnated with a positive electrode electrolyte containing a first gel polymer; a negative electrode impregnated with a negative electrode electrolyte containing a second gel polymer; and an electrolyte layer interposed between the positive electrode and the negative electrode and containing a third gel polymer; wherein the content of the third gel polymer in the electrolyte layer is greater than the content of the first gel polymer in the positive electrode electrolyte and the content of the second gel polymer in the negative electrode electrolyte.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0086547, dated July 4, 2023, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present specification discloses a secondary battery including a heterogeneous electrolyte gel polymer electrolyte and a method for manufacturing the same. [Background technology]

[0003] As technological development and demand for electronic devices continues to grow, demand for secondary batteries as energy sources is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, have been commercialized and widely used. Conventionally, liquid electrolytes, particularly ion-conductive organic liquid electrolytes in which salts are dissolved in non-aqueous organic solvents, have been used primarily as electrolytes for lithium secondary batteries. However, such liquid electrolytes have drawbacks, such as a high likelihood of organic solvent volatilization and low stability due to combustion caused by temperature increases at ambient temperatures and the battery itself. In response to this, research has recently been focused on commercializing polymer electrolytes, such as gel polymer electrolytes, instead of liquid electrolytes.

[0004] Meanwhile, the oxidation and reduction stability of electrolyte components is important for battery operation over a wide operating voltage range. While all conventional secondary batteries use a single electrolyte, some solvents or additives that are expected to improve performance can decompose or form undesired by-products due to side reactions at high or low potentials, resulting in degradation of battery performance. This makes it impossible to use certain electrolyte components, or limits the operating potential, resulting in low cell voltage.

[0005] In response to this, there is a demand for a heterogeneous electrolyte secondary battery that can selectively transmit lithium ions while suppressing the fluidity of the electrolyte within the cell and has a wide operating voltage range. Summary of the Invention [Problem to be solved by the invention]

[0006] In response to this, the present inventors aim to provide a heterogeneous electrolyte secondary battery having a wide operating voltage range by solving the problem that the solvent or additive is decomposed or forms undesired by-products due to side reactions at high or low potential, which leads to deterioration of battery performance. [Means for solving the problem]

[0007] Hereinafter, an electrolyte composition for a lithium metal battery according to a specific embodiment of the present invention will be described.

[0008] The 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 as meanings and concepts that correspond to the technical idea of ​​the present invention based on the principle that an inventor can appropriately define the concepts of terms in order to best explain his or her invention.

[0009] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0010] In this specification, the terms "comprises," "includes," "comprises," or "having" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0011] Gel polymer secondary battery According to one embodiment of the present invention, there is provided a gel polymer secondary battery comprising: a positive electrode impregnated with a positive electrode electrolyte containing a first gel polymer; a negative electrode impregnated with a negative electrode electrolyte containing a second gel polymer; and an electrolyte layer interposed between the positive electrode and the negative electrode and containing a third gel polymer; wherein the content of the third gel polymer in the electrolyte layer is greater than the content of the first gel polymer in the positive electrode electrolyte and the content of the second gel polymer in the negative electrode electrolyte.

[0012] electrolyte layer In an exemplary embodiment, the electrolyte layer may include a third gel polymer and an electrolyte solution, where the third gel polymer may include an oligomer or polymer crosslinked in the presence of a polymerization initiator, and the electrolyte solution may include a lithium salt, a solvent, and optional additives.

[0013] In an exemplary embodiment, the third gel polymer may include a crosslinked oligomer or polymer, and may include at least one 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. Such a third gel polymer may be a crosslinked oligomer or polymer obtained by thermally curing a crosslinkable monomer and an electrolyte solvent in the presence of a polymerization initiator.

[0014] In this case, examples of the crosslinkable monomer include ethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, tri(propylene glycol) di(meth)acrylate, tris(2-(meth)acryloethyl)isocyanurate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol di(meth)acrylate. The acrylate may include, but is not limited to, any one of erythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, acrylic acid, isobornyl acrylate, acrylonitrile, ethylene glycol (meth)acrylate, ethylhexyl (meth)acrylate or methyl (meth)acrylate, TMPTA (Trimethylpropane triacrylate), and ETPTA (Trimethylpropane ethoxylate triacrylate).

[0015] In an exemplary embodiment, the electrolyte layer may be a third electrolyte membrane or a separator impregnated with a third electrolyte. In this case, the third electrolyte may include a third gel polymer and an electrolytic solution. For example, the separator may be a conventional porous polymer film, such as a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in a laminated state. Alternatively, the separator may be a conventional porous nonwoven fabric, such as a nonwoven fabric made of a high-melting-point glass fiber or a polyethylene terephthalate fiber, but is not limited thereto.

[0016] In another embodiment, the third electrolyte membrane may be an electrolyte membrane defined by the third gel polymer, including a third electrolyte containing the third gel polymer and an electrolyte solution without a separate separator. In an exemplary embodiment, the electrolyte layer may be a polymer separator membrane impregnated with the third electrolyte and coated with alumina. The alumina coating may be one commonly used in lithium-ion batteries, and may serve as a location for the third gel polymer matrix to be densely formed in the pore spaces of the coating layer, allowing components larger than Li ions to be physically separated between the positive and negative electrodes.

[0017] In an exemplary embodiment, the content of the third gel polymer relative to the total weight of the electrolyte layer may be 10 to 30 wt %, for example, 10 to 20 wt % or 20 to 30 wt %. This range provides a relatively high gel polymer content compared to the electrode, allowing selective permeation of only lithium ions within the cell.

[0018] In an exemplary embodiment, the difference between the third gel polymer content and the first gel polymer content may be 10 to 20 wt %. The difference between the third gel polymer content and the second gel polymer content may be 10 to 20 wt %. This range provides a relatively high gel polymer content compared to the electrode, allowing selective permeation of only lithium ions within the cell.

[0019] In an exemplary embodiment, the lithium salt can function as a source of lithium ions in the battery to enable basic operation of the lithium secondary battery and can promote the movement of lithium ions between the positive electrode and the negative electrode, and any electrolyte commonly used for lithium secondary batteries can be used without limitation. For example, the lithium salt can contain Li as a cation. + Contains F as an anion - , Cl - , Br - , I - , NO3 - , N(CN)2- , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (F2SO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include at least one selected from the group consisting of:

[0020] The lithium salt may be used alone or in combination of two or more as needed. The lithium salt may be appropriately selected within a range that is generally usable, but in order to obtain an optimal effect of forming a corrosion-preventing coating on the electrode surface, the lithium salt may be contained in the gel polymer electrolyte composition at a concentration of 0.8M to 2M, specifically 0.8M to 1.5M.

[0021] In an exemplary embodiment of the present invention, the solvent contained in the electrolyte solution is not limited as long as it minimizes decomposition due to oxidation or other reactions during the charge and discharge process of the secondary battery and can exhibit desired properties together with the additives. For example, ether-based solvents, ester-based solvents, and amide-based solvents can be used alone or in combination. At least a portion of the solvent can be cured and crosslinked with the crosslinkable monomer to form a third gel polymer.

[0022] Among the organic solvents, the ether-based solvent may be any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether, and ethyl propyl ether, or a mixture of two or more of these, but is not limited thereto.

[0023] The ester solvent may include at least one compound selected from the group consisting of a cyclic carbonate compound, a chain carbonate compound, a chain ester compound, and a cyclic ester compound.

[0024] Specific examples of the cyclic carbonate compound include any one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, and fluoroethylene carbonate (FEC), or a mixture of two or more of these.

[0025] Specific examples of the chain carbonate compound include, but are not limited to, any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate, or a mixture of two or more of these.

[0026] Specific examples of the chain ester compound include, but are not limited to, any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more of these.

[0027] Specific examples of the cyclic ester compound include, but are not limited to, any one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof.

[0028] Among the ester-based solvents, cyclic carbonate-based compounds are preferred because they are highly viscous organic solvents with a high dielectric constant, which allows them to dissociate lithium salts in the electrolyte well. Furthermore, by mixing such cyclic carbonate-based compounds with low viscosity, low dielectric constant chain carbonate-based compounds and chain ester-based compounds, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, a gel polymer electrolyte having high electrical conductivity can be prepared, making them more preferred.

[0029] In an exemplary embodiment, the polymerization initiator may be a conventional polymerization initiator known in the art. For example, representative examples of the polymerization initiator include benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide, and hydrogen peroxide. peroxide) and one or more azo compounds selected from the group consisting of dimethyl 2,2'-azobis(2-cyanobutane), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(methylbutyronitrile), 2,2'-azobis(isobutyronitrile) (AIBN; 2,2'-azobis(isobutyronitrile)), and 2,2'-azobisdimethyl-valeronitrile (AMVN; 2,2'-azobisdimethyl-valeronitrile), but are not limited to these.

[0030] The polymerization initiator is decomposed by heat generated during the thermal curing process or within the battery, for example, at a temperature of 30°C to 100°C, specifically 60°C to 80°C, to form radicals, which react with the crosslinking monomer and optionally a portion of the solvent through free radical polymerization to form a gel polymer electrolyte.

[0031] The polymerization initiator may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the crosslinkable monomer. If the amount of the polymerization initiator exceeds 5 parts by weight, unreacted polymerization initiator may remain during the preparation of the gel polymer electrolyte, which may adversely affect battery performance. On the other hand, if the amount of the polymerization initiator is less than 0.1 part by weight, gelation may not proceed satisfactorily even at a certain temperature or higher.

[0032] Optionally, the electrolyte solution may further contain an additive such as vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, vinylethylene carbonate, cyclic sulfite, saturated sultone, unsaturated sultone, acyclic sulfone, or the like, which may be used alone or in combination.

[0033] In this case, examples of the cyclic sulfite include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butylene glycol sulfite. Examples of the saturated sultone include 1,3-propane sultone and 1,4-butane sultone. Examples of the unsaturated sultone include ethene sultone, 1,3-propene sultone, 1,4-butene sultone, and 1-methyl-1,3-propene sultone. Examples of the acyclic sulfone include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone.

[0034] Two or more of the additives may be mixed and included in an amount of 0.01 to 5 wt %, specifically 0.01 to 3 wt %, and preferably 0.05 to 3 wt %, based on the total amount of the electrolyte. If the additive content is less than 0.01 wt %, the effects of improving the low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery are negligible. If the additive content exceeds 5 wt %, excessive side reactions may occur in the electrolyte during battery charge and discharge. In particular, if the additive for forming the SEI film is added in excess, it may not be sufficiently decomposed at high temperatures and may remain unreacted or precipitated in the electrolyte at room temperature. This may result in side reactions that reduce the life or resistance characteristics of the secondary battery.

[0035] positive electrode In a gel polymer secondary battery according to an embodiment of the present invention, a positive electrode can be manufactured by forming a positive electrode mixture layer on a positive electrode current collector and impregnating the resulting layer with a positive electrode electrolyte containing a first gel polymer. The positive electrode mixture layer can be formed by coating a positive electrode current collector with a positive electrode slurry containing a positive electrode active material, a binder, a conductive material, and a solvent, followed by drying and rolling.

[0036] In an exemplary embodiment, the positive electrode electrolyte may include a first gel polymer and an electrolyte solution. The first gel polymer may include an oligomer or polymer crosslinked in the presence of a polymerization initiator, and the electrolyte solution may include a lithium salt, a solvent, and optional additives. In this case, the positive electrode electrolyte (Catholyte) may include a solvent with poor reduction stability or an additive for a positive electrode film-forming material. The polymerization initiator, lithium salt, first gel polymer, and crosslinkable monomer, additive, and / or solvent used in the positive electrode electrolyte may be the same as those used in the electrolyte layer described above.

[0037] In an exemplary embodiment, the first gel polymer may include a crosslinked oligomer or polymer, and may include at least one 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. Such a first gel polymer may be a crosslinked oligomer or polymer obtained by thermally curing a crosslinkable monomer and an electrolyte solvent in the presence of a polymerization initiator.

[0038] In this case, examples of the crosslinkable monomer include ethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, tri(propylene glycol) di(meth)acrylate, tris(2-(meth)acryloethyl)isocyanurate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. The acrylate may include, but is not limited to, any one of acrylate, dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, acrylic acid, isobornyl acrylate, acrylonitrile, ethylene glycol (meth)acrylate, ethylhexyl (meth)acrylate or methyl (meth)acrylate, TMPTA (Trimethylpropane triacrylate), and ETPTA (Trimethylpropane ethoxylate triacrylate).

[0039] In an exemplary embodiment, the content of the first gel polymer relative to the total weight of the positive electrode may be 0.1 to 10 wt %, for example, 0.1 to 5 wt % or 5 to 10 wt %. Within this range, the gel polymer content is relatively low compared to the electrolyte layer, thereby suppressing fluidity and maintaining the isolation of the different electrolytes.

[0040] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like can be used.

[0041] The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium composite metal oxide may be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), a lithium-nickel-cobalt-based oxide (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), a lithium-manganese-cobalt-based oxide (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), a lithium-nickel-manganese-cobalt-based oxide (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or a lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn<00​​)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are atomic fractions of independent elements, respectively, where 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.) and the like can be mentioned, and any one or two or more of these compounds may be included.

[0042] Among these, from the viewpoint of being able to enhance the capacity characteristics and safety of the battery, the lithium composite metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2, and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.).

[0043] The positive electrode active material may be contained at 80% to 99.5% by weight, specifically 85% to 95% by weight, based on the total weight of the solid content in the positive electrode slurry.

[0044] When the content of the positive electrode active material is 80% by weight or less, the energy density may be low and the capacity may decrease.

[0045] The binder is a component that aids in bonding the active material and conductive material, etc., and bonding to the current collector, and is typically added in an amount of 1 to 30 wt % based on the total weight of the solids in the positive electrode slurry. It is added in an amount of 1 to 50 parts by weight, more specifically 3 to 15 parts by weight, based on the total weight of the solids in the positive electrode slurry. If the binder is added in an amount less than 1 part by weight, the adhesive strength between the electrode active material and the current collector may be insufficient. If the binder is added in an amount greater than 50 parts by weight, the adhesive strength is improved, but the content of the electrode active material may be reduced accordingly, resulting in a reduced battery capacity.

[0046] Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers.

[0047] The conductive material is a material that does not induce chemical changes in the battery but provides conductivity, and may be added in an amount of 1 to 20 wt % based on the total weight of the solid content in the positive electrode slurry.

[0048] Typical examples of such conductive materials include carbon powders such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; graphite powders such as natural graphite, artificial graphite, and graphite with highly developed crystalline structures; conductive fibers such as carbon fiber and metal fiber; 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.Currently, acetylene black-based conductive materials (manufactured by Chevron Chemical Company, Denka Black (manufactured by Denka Singapore Private Limited), and Gulf Oil Company), Ketjenblack, EC-based (manufactured by Armak Company), Vulcan XC-72 (manufactured by Cabot Company), and Super-P (manufactured by Timcal). Commercially available products under the names (manufactured by Timcal) can also be used.

[0049] The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a suitable viscosity when the positive electrode active material and, optionally, a binder and a conductive material are contained. For example, the solvent may be contained so that the solids concentration in the slurry containing the positive electrode active material and, optionally, a binder and a conductive material, is 10% by weight to 60% by weight, preferably 20% by weight to 50% by weight.

[0050] negative electrode In a gel polymer secondary battery according to an embodiment of the present invention, a negative electrode can be manufactured by forming a negative electrode mixture layer on a negative electrode current collector and impregnating the resulting negative electrode mixture layer with a negative electrode electrolyte containing a second gel polymer. The negative electrode mixture layer can be formed by coating a negative electrode current collector with a negative electrode slurry containing a negative electrode active material, a binder, a conductive material, and a solvent, followed by drying and rolling.

[0051] In an exemplary embodiment, the negative electrode electrolyte may include a second gel polymer and an electrolyte solution. The second gel polymer may include an oligomer or polymer crosslinked in the presence of a polymerization initiator, and the electrolyte solution may include a lithium salt, a solvent, and optional additives. In this case, the negative electrode electrolyte (Anolyte) may include a solvent with poor oxidation stability or an additive for forming a negative electrode film. The polymerization initiator, lithium salt, second gel polymer, crosslinking monomer for forming the second gel polymer, additives, and / or solvent applied to the negative electrode electrolyte may be the same as those applied to the electrolyte layer described above.

[0052] In an exemplary embodiment, the second gel polymer may include a crosslinked oligomer or polymer, and may include at least one 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. Such a second gel polymer may be a crosslinked oligomer or polymer obtained by thermally curing a crosslinkable monomer and an electrolyte solvent in the presence of a polymerization initiator.

[0053] In this case, examples of the crosslinkable monomer include ethylene glycol di(meth)acrylate, poly(ethylene glycol) di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, tri(propylene glycol) di(meth)acrylate, tris(2-(meth)acryloethyl)isocyanurate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. The acrylate may include, but is not limited to, any one of acrylate, dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, acrylic acid, isobornyl acrylate, acrylonitrile, ethylene glycol (meth)acrylate, ethylhexyl (meth)acrylate or methyl (meth)acrylate, TMPTA (Trimethylpropane triacrylate), and ETPTA (Trimethylpropane ethoxylate triacrylate).

[0054] In an exemplary embodiment, the content of the second gel polymer relative to the total weight of the negative electrode may be 0.1 to 10 wt %, for example, 0.1 to 5 wt % or 5 to 10 wt %. Within this range, the content of the second gel polymer is relatively low compared to the electrolyte layer, thereby suppressing fluidity and maintaining the isolation of the different electrolytes.

[0055] The negative electrode current collector may generally have a thickness of 3 to 500 μm. Such a negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. Examples of materials that can be used include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surfaces treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys. Similarly to the positive electrode current collector, the surface may be formed with fine irregularities to strengthen the binding strength of the negative electrode active material, and the negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0056] In addition, the negative electrode active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of such a metal and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0057] The carbon material capable of reversibly intercalating / deintercalating lithium ions may be any carbon-based negative electrode active material commonly used in lithium ion secondary batteries, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination of these. Examples of crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous graphite, such as natural graphite or artificial graphite. Examples of amorphous carbon include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, and calcined coke.

[0058] As the metal or an alloy of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn or an alloy of these metals and lithium can be used.

[0059] As the metal composite oxide, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), and Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) can be used.

[0060] As the substance capable of doping and undoping lithium, Si, SiO x (0 < x < 2), Si-Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element and a combination thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element and a combination thereof, and is not Sn), etc. can be mentioned, and at least one of these can also be used in mixture with SiO2. As the element Y, it can be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and a combination thereof.

[0061] Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0062] The negative electrode active material may be included in an amount of 80 wt % to 99 wt % based on the total weight of the solid content in the negative electrode slurry.

[0063] The binder is a component that helps bind the conductive material, active material, and current collector together, and is typically added in an amount of 1 to 30 wt% based on the total weight of the solids in the negative electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0064] The conductive material may be the same material as that used in manufacturing the positive electrode, and may be added in an amount of 1 to 20 wt % based on the total weight of the solid content in the negative electrode slurry.

[0065] The solvent may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount that results in a suitable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, the solvent may be included so that the concentration of the solids, including the negative electrode active material and, optionally, a binder and a conductive material, is 50% by weight to 95% by weight, preferably 70% by weight to 90% by weight.

[0066] In an exemplary embodiment, the first gel polymer, the second gel polymer, and the third gel polymer may be the same or different. For example, the first gel polymer may have the functionality of suppressing a specific side reaction at the positive electrode. Meanwhile, the content of the third gel polymer in the electrolyte layer may be greater than the content of the first gel polymer in the positive electrode electrolyte and the content of the second gel polymer in the negative electrode electrolyte. In this case, the content of the first gel polymer in the positive electrode electrolyte and the content of the second gel polymer in the negative electrode electrolyte may be substantially the same or different. That is, the content of the first gel polymer in the positive electrode electrolyte may be greater or smaller than the content of the second gel polymer in the negative electrode electrolyte.

[0067] In an exemplary embodiment, the electrolyte layer may be in direct contact with the positive electrode and the negative electrode. Specifically, an additional layer may not be provided between the electrolyte layer and the positive electrode or between the electrolyte layer and the negative electrode, and at least a portion of the electrolyte layer may be in direct contact with the positive electrode and the negative electrode. Therefore, in a gel polymer secondary battery according to an embodiment of the present invention, the positive electrode / separator / negative electrode may be pressed and cured to provide adhesive strength, thereby eliminating the need for a separate adhesive material or lamination process.

[0068] Gel polymer secondary battery manufacturing method According to another embodiment of the present invention, there is provided a method for manufacturing a gel polymer secondary battery, including the steps of impregnating a spare positive electrode and a spare negative electrode with a positive electrode electrolyte and a negative electrode electrolyte, respectively; impregnating a separator with a third electrolyte or preparing an electrolyte layer with a third electrolyte membrane; and sequentially stacking the positive electrode, the electrolyte layer, and the negative electrode.

[0069] In the manufacturing method according to the embodiment of the present invention, the electrodes and the electrolyte layer are pre-impregnated before the assembly process, so the amount of electrolyte can be reduced by using a minimum amount of electrolyte, which is advantageous in terms of safety and cost. Furthermore, with the exception of the electrode electrolyte impregnation and crosslinking processes, the current mass production process can be used in the same way, so there is no need to add or modify special equipment.

[0070] First, a positive electrode and a negative electrode can be prepared by impregnating a preliminary positive electrode and a preliminary negative electrode with a positive electrode electrolyte and a negative electrode electrolyte, respectively. Specifically, a preliminary positive electrode manufactured by forming a positive electrode mixture layer on a positive electrode current collector can be impregnated with a positive electrode electrolyte containing a first gel polymer, and a preliminary negative electrode manufactured by forming a negative electrode mixture layer on a negative electrode current collector can be impregnated with a negative electrode electrolyte containing a second gel polymer. This impregnation can be performed using a method commonly used in the art.

[0071] In an exemplary embodiment, the impregnation step may be performed at room temperature for 2 to 48 hours to ensure uniform impregnation of the entire positive electrode and negative electrode. The content of the first gel polymer relative to the total weight of the positive electrode after impregnation may be 0.1 to 10 wt %, and the content of the second gel polymer relative to the total weight of the negative electrode after impregnation may be 0.1 to 10 wt %, which corresponds to a lower value than the content of the third gel polymer relative to the total weight of the electrolyte layer described below.

[0072] A high content of gel polymer in the electrolyte layer prevents the migration of large molecular weight substances between the positive and negative electrodes, while a low content of gel polymer in the electrode prevents the fluidity of the electrolyte. These properties can be utilized to selectively allow only lithium ions to pass through the cell, and applying a low content of gel polymer to the electrode can maintain isolation of different electrolytes. Figure 1 shows a schematic diagram of the mechanism by which anions and additives are prevented from migrating between the positive and negative electrodes in a gel polymer secondary battery. A dense gel polymer matrix is ​​formed in the pore spaces of the coating layer and separator, physically isolating components larger than Li ions between the positive and negative electrodes.

[0073] Alternatively, the separator may be impregnated with a third electrolyte, or an electrolyte layer may be prepared using a third electrolyte membrane. Specifically, the separator and third electrolyte may be the same as those described above, or may be impregnated in the same manner as the electrodes. Such an electrolyte layer may be a separator impregnated with a minimal amount of a high content of the third electrolyte, or a thin gel polymer film with a high content, thereby minimizing the increase in resistance.

[0074] Next, prior to the lamination step described below, the electrolyte layer can be thermally cured. Specifically, this thermal curing crosslinks the crosslinkable monomer and solvent in the presence of a polymerization initiator to form a third gel polymer, which can be incorporated into the electrolyte layer. After the electrolyte impregnation, the impregnated separator can be thermally cured first to prevent mixing with different gel electrolytes during the cell assembly and curing process, and then the cell can be assembled, thereby maintaining isolation between different electrolytes in the electrodes.

[0075] For example, the thermal curing step of the electrolyte layer can be performed at a temperature of 50°C to 100°C for 0.5 to 48 hours, preferably at a temperature of 60°C to 80°C for 0.5 to 24 hours. Next, the positive electrode, electrolyte layer, and negative electrode can be sequentially stacked and cured. For example, the positive electrode, electrolyte layer, and negative electrode can be sequentially arranged to form an electrode assembly. Specifically, the electrode assembly can be a laminated structure including two electrodes, a positive electrode and a negative electrode, and an electrolyte layer as a separator interposed between the electrodes or disposed on the top or bottom of one of the electrodes to insulate the electrodes from each other. The laminated structure can be in various forms, including, but not limited to, a stack of positive and negative electrodes of a predetermined specification with a separator interposed therebetween, or wound in a jelly roll shape. A positive electrode tab and a negative electrode tab can be connected to the electrode assembly. Specifically, the positive electrode tab and the negative electrode tab are connected to the positive electrode and the negative electrode of the electrode assembly, respectively, and can protrude to the outside of the secondary battery case to provide a path for electron transport. The third electrolyte of the electrolyte layer may be pre-cured so that the positive and negative electrode electrolytes remain separated during lamination.

[0076] The stacked positive electrode, electrolyte layer, and negative electrode can then be thermally cured. Specifically, the positive electrode electrolyte impregnated in the positive electrode, the negative electrode electrolyte impregnated in the negative electrode, and the third electrolyte in the electrolyte layer can be cured. This curing step can be performed by a thermal curing process. Through this curing step, the positive electrode electrolyte, the negative electrode electrolyte, and the electrolyte layer can form a first gel polymer, a second gel polymer, and a third gel polymer, respectively, with cross-linked oligomers or polymers formed by thermally curing the cross-linkable monomer and the electrolyte solution solvent in the presence of a polymerization initiator. For example, the thermal curing step can be performed under the same conditions as the pre-curing of the electrolyte layer, at a temperature of 50°C to 100°C for 0.5 to 48 hours, preferably at a temperature of 60°C to 80°C for 0.5 to 24 hours. [Effects of the Invention]

[0077] As described above, the gel polymer secondary battery according to the embodiment of the present invention can suppress the migration of large molecular weight materials between the positive and negative electrodes by applying a high content of gel polymer to the electrolyte layer, while suppressing the fluidity of the electrolyte by applying a low content of gel polymer to the electrodes, thereby selectively allowing only lithium ions to pass through the cell and maintaining the isolation of different electrolytes. In addition, applying a high content of gel polymer to the electrolyte layer can minimize the increase in resistance. [Brief explanation of the drawings]

[0078] [Figure 1] 10A and 10B are schematic diagrams illustrating a mechanism for inhibiting the migration of anions and additives between a positive electrode and a negative electrode in a gel polymer secondary battery according to an embodiment of the present invention. [Figure 2] The results of XPS analysis of gel polymer secondary batteries according to Comparative Examples 1 to 3 and Examples 1 and 2 of the present invention are shown for comparison. [Figure 3] The results of XPS analysis of gel polymer secondary batteries according to Comparative Examples 1 to 3 and Examples 1 and 2 of the present invention are shown for comparison. [Figure 4] The results of charge / discharge analysis of gel polymer secondary batteries according to Examples 3 and 4 of the present invention are shown for comparison. [Figure 5] The results of charge / discharge analysis of gel polymer secondary batteries according to Examples 3 and 4 of the present invention are shown for comparison. DETAILED DESCRIPTION OF THE INVENTION

[0079] Although the present invention may be embodied in various different forms, it is to be understood that the present invention is not limited to the following examples and comparative examples, and may be embodied in various different forms, such as by way of example only, and not by way of limitation.

[0080] Comparative Example 1: Cell with 1M LiPF6-added liquid electrolyte A liquid electrolyte was prepared by dissolving 1M LiPF6 in a solvent (ethylene carbonate (EC): propylene carbonate (PC) = 5:5 volume ratio) and adding 0.06 wt% AIBN as a polymerization initiator. A graphite anode and a PE separator were sequentially stacked, and the prepared liquid electrolyte was poured into the half cell "S1."

[0081] Comparative Example 2: Cell with 2M LiFSI-added liquid electrolyte A liquid electrolyte was prepared by dissolving 2M LiFSI in a solvent (ethylene carbonate (EC): propylene carbonate (PC) = 5:5 volume ratio) and adding 0.06 wt% AIBN as a polymerization initiator. A graphite anode and a PE separator were sequentially stacked, and the prepared liquid electrolyte was poured into the half-cell "S2."

[0082] Comparative Example 3: Cell with LiPF6 and LiFSI mixed gel polymer electrolyte A gel polymer electrolyte composition was prepared by mixing LiPF6 and LiFSI at a 1:1 wt% ratio in a solvent (ethylene carbonate (EC):propylene carbonate (PC) = 5:5 volume ratio), adding 10% ETPTA (ethoxylated trimethylolpropane triacrylate) oligomer and 0.06 wt% AIBN as a polymerization initiator. A graphite anode, PE separator, and NCM811 cathode were sequentially stacked, and the prepared liquid electrolyte was poured into the "S3" cell.

[0083] Example 1: Cells with different gel electrolytes The negative electrode electrolyte was prepared by dissolving 1M LiPF6 in a solvent (ethylene carbonate (EC):propylene carbonate (PC) = 5:5 volume ratio) and adding 0.06 wt% AIBN as a polymerization initiator. The graphite negative electrode was impregnated with this. The positive electrode electrolyte was prepared by dissolving 2M LiFSI in a solvent (ethylene carbonate (EC):propylene carbonate (PC) = 5:5 volume ratio) and adding 0.06 wt% AIBN as a polymerization initiator. The NCM811 positive electrode was impregnated with this.

[0084] In addition, a gel polymer electrolyte composition was prepared by adding 10 wt% ETPTA (ethoxylated trimethylolpropane triacrylate) oligomer and 0.06 wt% AIBN as a polymerization initiator to a solvent (ethylene carbonate (EC): propylene carbonate (PC) = 5:5 volume ratio), and the PE separator was impregnated with the composition. The impregnated PE separator was then heat-cured at 60°C for 5 hours.

[0085] The prepared materials were stacked in the order of positive electrode / separator / negative electrode, pressed, and heat-cured to manufacture the "S4" cell.

[0086] Example 2: Cells with different gel electrolytes An "S5" cell was fabricated in the same manner as in Example 1, except that the content of ETPTA oligomer in the gel polymer electrolyte composition was 20 wt %.

[0087] Experimental example 1: XPS analysis The cells prepared in Comparative Examples 1-3 and Examples 1-2 were subjected to three 0.1C charge-discharge cycles, then disassembled to separate the negative electrodes. Quantitative elemental analysis of the negative electrode coating, which changed with the addition of lithium salt, was performed using an X-ray photoelectron spectroscopy (XPS, Sigma probe). The elements F and P, which account for a large proportion of the negative electrode coating, were analyzed, and the separation of different electrolytes in the high-content gel polymer electrolyte was verified. The results are shown in Figures 2 and 3.

[0088] 2 and 3, it was confirmed that Comparative Example 1 (S1) containing LiPF6 lithium salt formed a coating richer in F and P than Comparative Example 2 (S2) containing LiFSI.

[0089] Comparative Example 3 (S3) is based on the assumption that the high-content gel polymer electrolyte impregnated in the separator cannot prevent the infiltration of different electrolytes between the positive and negative electrodes, and shows a composition ratio of F and P that is intermediate between Comparative Example 1 (S1) and Comparative Example 2 (S2).

[0090] In addition, Example 1 (S4) and Example 2 (S5) are cells using a 2M LiFSI-impregnated positive electrode, a 1M LiPF6-impregnated negative electrode, and different gel electrolytes. It was confirmed that Example 1 (S5), which uses a high-content gel polymer electrolyte, tends to form a coating that is richer in F and P than Example 2 (S4).

[0091] This confirms that the higher the polymer content in the gel polymer electrolyte-impregnated separator of the present invention, the more effective it is in separating different electrolytes between the positive and negative electrodes.

[0092] Example 3: Cells with different gel electrolytes The positive electrode electrolyte was prepared by dissolving 1M LiPF6 in a solvent (ethylene carbonate (EC):propylene carbonate (PC) = 5:5 volume ratio) and adding 5 wt% ETPTA (ethoxylated tri-methylolpropane triacrylate) oligomer and 0.06 wt% AIBN as a polymerization initiator. The positive electrode electrolyte was impregnated into an NCM811 positive electrode. The negative electrode electrolyte was prepared by dissolving 2M LiFSI in a solvent (ethylene carbonate (EC):propylene carbonate (PC) = 5:5 volume ratio) and adding 5 wt% ETPTA (ethoxylated tri-methylolpropane triacrylate) oligomer and 0.06 wt% AIBN as a polymerization initiator. The negative electrode electrolyte was impregnated into a graphite negative electrode.

[0093] A gel polymer electrolyte composition was prepared by adding 20 wt% ETPTA (ethoxylated trimethylolpropane triacrylate) oligomer and 0.06 wt% AIBN as a polymerization initiator to a solvent (ethylene carbonate (EC): propylene carbonate (PC) = 5:5 volume ratio), and then impregnating an alumina-coated PP separator with the composition at room temperature. The impregnated separator was then heat-cured at 60°C for 5 hours.

[0094] The prepared materials were stacked in the order of positive electrode / separator / negative electrode, pressed, and heat-cured to produce the 'Set1' cell.

[0095] Example 4: Cells with different gel electrolytes A "Set2" cell was manufactured in the same manner as in Example 3, except that LiPF6 and LiFSI were mixed and dissolved in a solvent (ethylene carbonate (EC): propylene carbonate (PC) = 5:5 volume ratio) at a molar concentration ratio of 1:2, and 5 wt% of ETPTA (ethoxylated tri-methylolpropane triacrylate) oligomer and 0.06 wt% of AIBN as a polymerization initiator were added to prepare an electrolyte. The NCM811 positive electrode and graphite negative electrode were impregnated with the electrolyte, respectively.

[0096] Experimental example 2: Charge / discharge analysis The charge / discharge analysis was performed using a 0.1C (0.518mA applied) CC / CV charge / CC discharge with the coin cell capacity as the reference (Figure 4). After cell activation, the discharge capacity was measured by 3 cycles of 0.1C and 3 cycles of 0.33C (1.709mA) CC / CV charge / CC discharge (Figure 5).

[0097] The PC uses Li during the initial charging process. + Li-(PC) coordinated with n When 2M LiFSI is applied, Li + The coordination number between -PC is reduced, which significantly reduces performance degradation due to peeling.

[0098] 4 and 5, Example 4 (Set 2), which simulates a situation in which the electrolyte impregnated in the positive electrode migrates and mixes with the electrolyte impregnated in the negative electrode, shows a significant decrease in capacity and lifespan, confirming that the high-content oligomer gel electrolyte effectively blocks mass transfer between the positive and negative electrodes.

[0099] Experimental Example 3: Reducing the amount of electrolyte A total of eight cells using different gel electrolytes of Example 3 were manufactured, and the average cell weight was calculated as shown in Table 1 below. The excess electrolyte amount was calculated from the average cell weight as shown in Table 2. In this case, the electrolyte density was 1.388 g / mol, and the polymer content relative to the total electrolyte in the cell was 6.6%.

[0100] [Table 1]

[0101] [Table 2]

[0102] As a result, it was confirmed that the electrolyte reduction was approximately 10% (excess amount = approximately 130%) compared to LIBs using liquid electrolytes, and that the amount of electrolyte reduction increased as the polymer content increased.

[0103] Therefore, the gel polymer secondary battery according to the present invention can maintain the separation of the different electrolytes between the positive and negative electrodes by applying a high content of gel polymer electrolyte, thereby achieving a wide operating voltage range and reducing the amount of electrolyte.

Claims

1. a positive electrode impregnated with a positive electrode electrolyte including a first gel polymer; a negative electrode impregnated with a negative electrode electrolyte comprising a second gel polymer; and an electrolyte layer interposed between the positive electrode and the negative electrode and including a third gel polymer; a third gel polymer content of the electrolyte layer greater than a first gel polymer content of the positive electrode electrolyte and a second gel polymer content of the negative electrode electrolyte;

2. The gel polymer secondary battery according to claim 1 , wherein the electrolyte layer is a third electrolyte membrane or a separator impregnated with a third electrolyte.

3. 2. The gel polymer secondary battery according to claim 1, wherein the electrolyte layer is a polymer separator impregnated with a third electrolyte and coated with alumina.

4. 10. The gel polymer secondary battery of claim 1, wherein the content of the third gel polymer relative to the total weight of the electrolyte layer is 10% by weight to 30% by weight.

5. 5. The gel polymer secondary battery of claim 4, wherein the content of the third gel polymer relative to the total weight of the electrolyte layer is 20% by weight to 30% by weight.

6. the content of the first gel polymer relative to the total weight of the positive electrode is 0.1 wt % to 10 wt %; The gel polymer secondary battery of claim 1, wherein the content of the second gel polymer relative to the total weight of the negative electrode is 0.1 wt % to 10 wt %.

7. The difference between the third gel polymer content and the first gel polymer content, and the difference between the third gel polymer content and the second gel polymer content, are each 10% by weight to 20% by weight. A gel polymer secondary battery according to any one of claims 1 to 6.

8. 2. The gel polymer secondary battery according to claim 1, wherein the first gel polymer, the second gel polymer, and the third gel polymer each comprise 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.

9. The gel polymer secondary battery according to claim 1 , wherein the electrolyte layer is in direct contact with the positive electrode and the negative electrode.

10. preparing a positive electrode and a negative electrode by impregnating a spare positive electrode and a spare negative electrode with a positive electrode electrolyte and a negative electrode electrolyte, respectively; impregnating the separator with a third electrolyte or providing an electrolyte layer with a third electrolyte membrane; and and laminating the positive electrode, the electrolyte layer, and the negative electrode in order.

11. The method for manufacturing a gel polymer secondary battery according to claim 10 , further comprising: thermally curing the positive electrode electrolyte, the negative electrode electrolyte, or the electrolyte layer.

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