Electrode structure for lithium secondary battery and method for manufacturing same

Abstract

An electrode structure for a lithium secondary battery according to an exemplary embodiment includes a first electrode, a second electrode disposed opposite the first electrode, and a first electrolyte layer and a second electrolyte layer formed in this order between the first electrode and the second electrode. The first electrolyte layer and the second electrolyte layer may respectively include a polymer electrolyte layer, and the first electrolyte layer and the second electrolyte layer may have different compositions from each other. The electrode structure may be manufactured using different types of curing processes.

Description

Technical Field

[0001] The present invention relates to an electrode structure for a lithium secondary battery and a method for manufacturing the same. Background Art

[0002] A secondary battery is a battery that can be repeatedly charged and discharged. With the development of the information communication and display industries, secondary batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptop computers. In addition, in recent years, battery packs including secondary batteries are being developed and used as power sources for eco-friendly vehicles such as hybrid vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, etc. Among them, lithium secondary batteries have a high working voltage and energy density per unit weight, and are advantageous for charging speed and weight reduction. Therefore, active research and development are being carried out.

[0004] A liquid electrolyte can be used as the electrolyte of a lithium secondary battery. However, when using a liquid electrolyte, safety problems such as leakage, explosion, and fire may occur due to rapid environmental changes such as temperature changes and external impacts. Therefore, attempts are being made to ensure safety and increase the energy density by solidifying the electrolyte.

[0005] An all-solid-state battery may include an electrode assembly including a positive electrode, a negative electrode, and an intermediate electrolyte layer, and the all-solid-state battery may further include a separator (separation membrane) between the positive electrode and the negative electrode. The all-solid-state battery may further include an outer packaging material for accommodating the electrode assembly.

[0006] As the application range of all-solid-state batteries expands, longer life, higher capacity, and higher energy density are required. However, when including a separator between the positive electrode and the negative electrode, the energy density per unit volume may decrease, or the electronic conductivity and ionic conductivity may decrease. When removing the separator between the positive electrode and the negative electrode, a short circuit may occur between the positive electrode and the negative electrode. Summary of the Invention

[0007] (I) Technical Problem to be Solved

[0008] One technical problem of the present invention is to provide an electrode structure for a lithium secondary battery having improved energy density and stability.

[0009] One technical problem of the present invention is to provide a method for manufacturing an electrode structure for a lithium secondary battery having improved energy density and stability.

[0010] (II) Technical Solution

[0011] The electrode structure for a secondary battery according to an exemplary embodiment may include: a first electrode; a first electrolyte layer formed on the first electrode, the first electrolyte layer including a first polymer electrolyte; a second electrode disposed on the first electrolyte layer; and a second electrolyte layer formed between the first electrolyte layer and the second electrode, the second electrolyte layer including a second polymer electrolyte. The first electrolyte layer and the second electrolyte layer may have different compositions or different thicknesses from each other.

[0012] In some embodiments, the first polymer electrolyte may include a polymer of a photopolymerizable compound and a lithium salt, and the second polymer electrolyte may include a polymer of a thermosetting compound and a lithium salt.

[0013] In some embodiments, the second electrolyte layer may further include an oxide-based solid electrolyte.

[0014] In one embodiment, the first electrolyte layer may further include an oxide-based solid electrolyte. In one embodiment, the content (by weight) of the oxide-based solid electrolyte in the first electrolyte layer may be less than the content (by weight) of the oxide-based solid electrolyte in the second electrolyte layer.

[0015] In some embodiments, in the total weight of the first electrolyte layer, the content of the oxide-based solid electrolyte in the first electrolyte layer may be greater than 0% by weight and 30% by weight or less.

[0016] In some embodiments, in the total weight of the second electrolyte layer, the content of the oxide-based solid electrolyte in the second electrolyte layer may be less than 70% by weight.

[0017] In some embodiments, the first electrolyte layer may not include an oxide-based solid electrolyte.

[0018] In some embodiments, the second electrolyte layer may not include an oxide-based solid electrolyte.

[0019] In some embodiments, the thickness of the second electrolyte layer may be greater than the thickness of the first electrolyte layer.

[0020] In some embodiments, the first electrode may include a first current collector and a first electrode active material layer formed on the first current collector.

[0021] In one embodiment, the first electrode active material layer may include the first polymer electrolyte.

[0022] In some embodiments, the second electrode may include a second current collector and a second electrode active material layer formed on the second current collector. In one embodiment, the second electrode active material layer may contain the second polymer electrolyte.

[0023] In a method for manufacturing an electrode structure for a secondary battery according to an exemplary embodiment, a first electrolyte composition may be coated on a first electrode, and light may be irradiated onto the first electrolyte composition to form a first electrolyte layer. A second electrode may be disposed at a predetermined interval on the first electrolyte layer, and a second electrolyte composition may be injected to fill the space between the first electrolyte layer and the second electrode. The injected second electrolyte composition may be heated to form a second electrolyte layer.

[0024] In some embodiments, the first electrolyte composition and the second electrolyte composition may each contain a lithium salt and an organic solvent.

[0025] In some embodiments, the first electrolyte composition may further contain a photopolymerizable compound and a photoinitiator, and the second electrolyte composition may further contain a thermosetting compound and a thermal initiator.

[0026] In some embodiments, the second electrolyte composition may further contain an oxide-based solid electrolyte.

[0027] In one embodiment, the first electrolyte composition may further contain an oxide-based solid electrolyte, and the content (by weight %) of the oxide-based solid electrolyte in the first electrolyte composition may be less than the content (by weight %) of the oxide-based solid electrolyte in the second electrolyte composition.

[0028] In one embodiment, the first electrolyte composition may not contain an oxide-based solid electrolyte.

[0029] In one embodiment, the second electrolyte composition may not contain an oxide-based solid electrolyte.

[0030] In one embodiment, the viscosity of the second electrolyte composition may be higher than the viscosity of the first electrolyte composition.

[0031] In some embodiments, when the first electrolyte composition is coated on the first electrode, a part of the first electrolyte composition may be impregnated into the interior of the first electrode.

[0032] In one embodiment, by irradiating light onto the first electrolyte composition, a crosslinked network derived from the first electrolyte composition may be formed between the first electrolyte layer and the first electrode.

[0033] In some embodiments, when the second electrolyte composition is injected between the first electrolyte layer and the second electrode, a part of the second electrolyte composition may be impregnated into the interior of the second electrode.

[0034] (III) Advantageous Effects

[0035] The electrode structure for a secondary battery may include a solid electrolyte layer having a multilayer structure between a first electrode and a second electrode. The electrode structure may have improved ionic conductivity, as well as mechanical stability and chemical stability.

[0036] The first electrolyte layer may be formed by photopolymerization after coating a first electrolyte composition on the first electrode. By directly forming the first electrolyte layer on the first electrode, the lithium ion conductivity of the first electrode can be improved, and the interfacial resistance between the first electrode and the first electrolyte layer can be reduced.

[0037] The second electrolyte layer may be formed by thermal polymerization after injecting a second electrolyte composition between the first electrolyte layer and the second electrode. By directly forming the second electrolyte layer on the second electrode, the interfacial resistance between the second electrode and the second electrolyte layer can be reduced, and the impregnation property of the second electrolyte layer with respect to the first electrode and the second electrode can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic cross-sectional view for explaining an electrode structure for a lithium secondary battery according to an exemplary embodiment.

[0039] Figure 2 is a schematic process flowchart for explaining a method of manufacturing an electrode structure according to an exemplary embodiment.

[0040] Figure 3 and Figure 4 are respectively schematic cross-sectional views showing a part of an electrode structure according to an exemplary embodiment.

[0041] Figure 5 is a schematic view for explaining a method of manufacturing an electrode structure according to an exemplary embodiment.

[0042] Figure 6 is an SEM image of a cross-section of the electrode structure according to Example 1.

[0043] Figure 7 is an SEM image of a cross-section of the first electrolyte layer and the second electrolyte layer of the electrode structure according to Example 1.

[0044] Figure 8It is a SEM image of the cross section of the first electrolyte layer and the second electrolyte layer of the electrode structure according to Comparative Example 1.

[0045] Figure 9 It is a graph showing the discharge capacity according to the cycle of the secondary battery according to the Examples and Comparative Examples. Detailed Description

[0046] According to an embodiment provided by the present invention, there is provided an electrode structure including electrodes disposed opposite to each other and an electrolyte layer formed between the electrodes.

[0047] In addition, according to an embodiment provided by the present invention, there is provided a method for manufacturing the above electrode structure.

[0048] Hereinafter, with reference to the drawings, embodiments of the present invention will be described in more detail. However, the drawings in this specification are used to illustrate some embodiments of the present invention and, together with the above Summary of the Invention, serve to further understand the technical idea of the present invention. Therefore, the present invention should not be construed as being limited to the content described in the drawings.

[0049] Terms such as "upper", "bottom", "first", "second", etc. used in this specification represent the relative positions of the respective components and do not mean an absolute up and down relationship.

[0050] Hereinafter, in this specification, unless otherwise specifically defined, when describing that a part such as a layer, film, thin film, region, plate, etc. is "above" or "on" another part, this may include not only the case where it is "directly" above the other part, but also the case where there are other parts in between.

[0051] Hereinafter, in this specification, "polymer" or "polymer" includes oligomers and includes homopolymers and copolymers. The copolymer may be an alternating polymer, a block copolymer, a random copolymer, a graft copolymer, a crosslinked copolymer, or include all of these copolymers.

[0052] Hereinafter, in this specification, "polymer electrolyte" may refer not only to an all-solid electrolyte but also to a "gel polymer electrolyte" containing an electrolytic solution in a polymer-based electrolyte. For example, depending on the preparation method, the gel polymer electrolyte may be in a form swollen with an electrolytic solution after preparing a polymer matrix (physical gel), or may be in a form prepared by curing a composition in which an electrolytic solution and a monomer are mixed (chemical gel).

[0053] Figure 1 It is a schematic cross-sectional view showing an electrode structure for a lithium secondary battery according to an exemplary embodiment.

[0054] Reference Figure 1 , the electrode structure for a lithium secondary battery (hereinafter, may be simply referred to as "electrode structure") may include a first electrode 100, a first electrolyte layer 140 formed on the first electrode 100, a second electrode 130 disposed on the first electrolyte layer 140, and a second electrolyte layer 150 formed between the first electrolyte layer 140 and the second electrode 130.

[0055] The first electrode 100 and the second electrode 130 may contain an electrode active material capable of intercalating and deintercalating lithium ions.

[0056] For example, the first electrode 100 and the second electrode 130 may each include an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector. The electrode active material layer may contain an electrode active material and may further contain a conductive material, a binder, or a solid electrolyte.

[0057] In one embodiment, the first electrode 100 or the second electrode 130 may be a lithium electrode formed of lithium metal or a lithium alloy. For example, the lithium secondary battery may also be provided as a lithium metal battery.

[0058] The first electrolyte layer 140 and the second electrolyte layer 150 may each contain a polymer electrolyte. For example, the first electrolyte layer 140 may be a solid electrolyte layer containing a first polymer electrolyte, and the second electrolyte layer 150 may be a solid electrolyte layer containing a second polymer electrolyte.

[0059] Since the electrode structure 90 includes a solid electrolyte layer between electrodes disposed opposite to each other, the ionic conductivity of the electrode structure can be improved even without additionally injecting a liquid electrolyte, such as a lithium salt and an organic solvent, into the battery. Therefore, the power and capacity characteristics of the secondary battery can be improved.

[0060] In addition, leakage, ignition, and vaporization caused by the liquid electrolyte can be prevented, and at the same time, mechanical stabilities such as the thermal stability / chemical stability and puncture stability of the electrode structure 90 can be improved.

[0061] According to an exemplary embodiment, the first electrolyte layer 140 may be formed by a photopolymerization process, and the second electrolyte layer 150 may be formed by a thermal polymerization process.

[0062] For example, the first polymer electrolyte may contain a polymer of a photopolymerizable compound, and the second polymer electrolyte may contain a polymer of a thermosetting compound.

[0063] The photopolymerizable compound contains photoreactive functional groups and can be crosslinked by light irradiation. The thermosetting compound contains thermoreactive functional groups and can form a crosslinked network by heat treatment.

[0064] In some embodiments, the content of the polymer contained in the first electrolyte layer 140 and the second electrolyte layer 150 can be 1 wt% to 80 wt% of the total weight of each electrolyte layer. For example, it can be 5 wt% to 80 wt%, 5 wt% to 50 wt%, 10 wt% to 4 wt%, or 10 wt% to 30 wt%.

[0065] Within the above range, the stability and mechanical and physical properties of the electrolyte layer can be further improved, and a decrease in ionic conductivity caused by an excessive amount of polymer can be prevented.

[0066] In one embodiment, the first polymer electrolyte and / or the second polymer electrolyte can each contain a lithium salt and / or a solvent. By means of the lithium salt, a migration channel for lithium ions within the electrolyte layer can be further ensured, and the power characteristics of the secondary battery can be further improved.

[0067] The lithium salt can be selected from LiPF6, LiClO4, LiBF4, LiFSI, LiTFSI, LiSO3CF3, LiBOB, LiFOB, LiDFOB, LiDFBP, LiTFOP, LiPO2F2, LiCl, LiBr, LiI, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, or a combination thereof.

[0068] The solvent can be selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, tetrahydrofuran, or a combination thereof, but is not limited thereto.

[0069] Figure 2 is a schematic process flow diagram for explaining a method for manufacturing an electrode structure according to an exemplary embodiment. Hereinafter, referring toFigure 2 A method for manufacturing a counter electrode structure will be described.

[0070] Referring to Figure 2 , the first electrolyte composition can be coated on at least one surface of the first electrode 100, and a polymerization reaction can be performed on the first electrolyte composition to form the first electrolyte layer 140 (for example, step S10).

[0071] The first electrolyte layer 140 is directly formed on the first electrode 100, thereby reducing the interfacial resistance between the first electrode 100 and the first electrolyte layer 140. For example, when the first electrode 100 and the first electrolyte layer 140 are physically calendered or bonded, the adhesiveness at the interface may be reduced, and cracks or fractures caused by external forces may occur.

[0072] As a method for coating the first electrolyte composition, for example, gravure coating, die coating, multi-die coating, dip coating, comma coating, etc. can be used.

[0073] According to an exemplary embodiment, the first electrolyte composition can be photopolymerized to form the first electrolyte layer 140. For example, the first electrolyte composition may contain a photopolymerizable compound and a photoinitiator.

[0074] Since the first electrolyte layer 140 is formed by a photopolymerization reaction, the curing process of the electrolyte layer can be performed at a relatively low temperature. Therefore, damage to the first electrode 100 caused by high-temperature heat treatment can be prevented.

[0075] The photopolymerizable compound may include, for example, ethoxylated trimethylolpropane triacrylate, 1,3-butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, ethylene glycol divinyl ether, diethylene glycol divinyl ether, diethylene glycol diglycidyl ether, (meth)acrylic acid glycidyl ester, triethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, polyethylene glycol diglycidyl ether, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polyethylene glycol polypropylene glycol di(meth)acrylate, or a combination thereof, but is not limited thereto.

[0076] The photoinitiator may include 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP), benzoin ether, dialkyl acetophenone, hydroxylalkylketone, phenyl glyoxylate, Benzyl DimethylKetal, (2,4,6-trimethyl-benzoyl)-trimethylphosphine oxide and other acyl phosphines, α-aminoketone, etc.

[0077] In some embodiments, the curing process for the photopolymerization may use light with a wavelength of 200 nm to 405 nm and an intensity of 200 mW / cm 2 to 1500 mW / cm 2 to proceed. In one embodiment, the curing process may be carried out for 5 seconds to 10 minutes.

[0078] In one embodiment, the curing process may be carried out using an ultraviolet (UV) lamp. For example, the ultraviolet lamp may include a mercury ultraviolet lamp, a metal ultraviolet lamp, an LED lamp, etc.

[0079] In some embodiments, in the total weight of the first electrolyte composition, the content of the photopolymerizable compound in the first electrolyte composition may be 1 wt% to 80 wt%, 5 wt% to 50 wt%, or 10 wt% to 40 wt%. Within the above range, the mechanical and physical properties and the ionic conductivity of the first electrolyte layer 140 can be improved simultaneously.

[0080] Figure 3 and Figure 4 are respectively schematic cross-sectional views showing a part of the electrode structure according to an exemplary embodiment.

[0081] Referring to Figure 3 and Figure 4 , the first electrode 100 may include an electrode current collector 120 and an electrode active material layer 110 formed on the electrode current collector 120. The electrode active material layer 110 may also be formed on both sides (for example, the upper and bottom surfaces) of the electrode current collector 120.

[0082] The first electrolyte layer 140 may be formed on the electrode active material layer 110. For example, the first electrolyte composition may be coated on the upper surface of the electrode active material layer 110 and then photopolymerized to form the first electrolyte layer 140.

[0083] In some embodiments, the first electrode 100 may comprise a first polymer electrolyte. For example, a portion of the polymer electrolyte 142 contained in the first electrolyte layer 140 may be embedded or diffused into the interior of the first electrode 100.

[0084] In one embodiment, during the process of coating the first electrolyte composition on top of the electrode active material layer 110, a portion of the first electrolyte composition may be impregnated into the interior of the electrode active material layer 110. For example, the lithium salt, the photopolymerizable compound, and / or the photoinitiator of the first electrolyte composition may move / diffuse between the electrode active materials 112.

[0085] During the process of irradiating light onto the first electrolyte composition, the photopolymerizable compound impregnated inside the electrode active material layer 110 may also polymerize together. Thus, a crosslinked network derived from the photopolymerizable compound may be formed between the first electrolyte layer 130 and the electrode active material layer 110.

[0086] In one embodiment, through the crosslinked network, the first electrode 100 and the first electrolyte layer 130 may be substantially compounded or integrated. Thus, the interfacial resistance between the first electrode 100 and the first electrolyte layer 130 may be further reduced. In addition, since the first electrode 100 contains a polymer electrolyte, the migration path of ions inside the first electrode 100 may be further ensured, and the ionic conductivity may be further improved.

[0087] The second electrode 130 may be disposed on the first electrode 100 on which the first electrolyte layer 140 is formed (e.g., step S20). The second electrode 130 may be disposed in a manner facing the first electrolyte layer 140.

[0088] In one embodiment, the second electrode 130 may be disposed at a predetermined interval from the first electrolyte layer 140. For example, a gap may be formed between the first electrolyte layer 140 and the second electrode 130. An initial electrode structure or an initial cell may be defined by the first electrode 100, the first electrolyte layer 140, and the second electrode 130. In one embodiment, a porous support may be used to support the initial electrode structure.

[0089] The second electrolyte composition may be injected or filled into the initial electrode structure (e.g., step S30).

[0090] Figure 5 It is a schematic diagram for explaining a method of manufacturing an electrode structure according to an exemplary embodiment.

[0091] Refer to Figure 5, the second electrolyte composition can be injected between the first electrolyte layer 140 and the second electrode 130 of the initial electrode structure 92.

[0092] According to an exemplary embodiment, the second electrolyte composition can be injected to fill the gap between the first electrolyte layer 140 and the second electrode 130. For example, the second electrolyte composition injected into the initial electrode structure 92 can entirely cover one side of the first electrolyte layer 140 and one side of the second electrode 130.

[0093] The initial electrode structure 92 injected with the second electrolyte composition can be heat-treated to form the second electrolyte layer 150 (e.g., step S40). Through the heat treatment, the second electrolyte composition can polymerize or crosslink.

[0094] For example, the second electrolyte composition can include a thermosetting compound and a thermal initiator.

[0095] The thermosetting compound can include substances substantially the same as or similar to the above-mentioned photopolymerizable compounds. For example, the thermosetting compound can include ethoxylated trimethylolpropane triacrylate, 1,3-butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, ethylene glycol divinyl ether, glycidyl (meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, polyethylene glycol diglycidyl ether, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polyethylene glycol polypropylene glycol di(meth)acrylate, etc.

[0096] The thermal initiator can include azo-based compounds such as 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), 2,2'-azobisisobutyronitrile (AIBN), azobisisoheptonitrile (AMVN), etc., and peroxide-based compounds such as benzoyl peroxide, acetyl peroxide, dilauroyl peroxide, di-tert-butyl peroxide, cumyl peroxide, hydrogen peroxide, etc.

[0097] The polymerization reaction can be carried out in a state where the second electrolyte composition is injected between the first electrolyte layer 140 and the second electrode 130 to directly form the second electrolyte layer 150 on the first electrolyte layer 140 and the second electrode 130. Therefore, the adhesion between the first electrolyte layer 140 and the second electrolyte layer 150 and the adhesion between the second electrolyte layer 150 and the second electrode 130 can be increased simultaneously, and the overall interface resistance of the electrode structure can be reduced.

[0098] For example, when physically or thermally bonding and pressing electrolyte layers each formed in the form of a film, the adhesiveness at the interface between the electrolyte layers may decrease. When the electrolyte layer contains a solid-state electrolyte, the elastic force or flexibility is relatively insufficient, so that the warping at the interface between the electrolyte layers during charge and discharge may be more serious. Therefore, due to repeated charge and discharge, the interface resistance may gradually increase. In addition, during the pressing of the electrolyte layer, cracks may be generated in the electrode structure body due to the application of physical external force. Therefore, the electrochemical characteristics and stability of the electrode structure body may be reduced.

[0099] According to an exemplary embodiment, since the second electrolyte layer 150 is directly formed on the first electrolyte layer 140 and the second electrode 150, for example, a crosslinked network can be formed at each interface or the adhesiveness can be further enhanced. Therefore, the interface resistance and the overall internal resistance within the electrode structure body 90 can be reduced, and since the electrode structure body 90 can have a substantially integrated structure, the structural stability can be maintained even during repeated charge and discharge processes.

[0100] In addition, since the second electrolyte layer 150 is formed by a thermal polymerization reaction, the crosslinking density and the mechanical and physical properties of the second electrolyte layer 150 can be further improved. For example, when a photopolymerization reaction is performed on the second electrolyte composition, the first electrolyte layer 140 and the second electrode 130 may block or interfere with the irradiated light, which may lead to a decrease in polymerizability.

[0101] In some embodiments, the second electrode 130 may include a second polymer electrolyte. For example, during the process of injecting the second electrolyte composition into the initial electrode structure body 92, a part of the second electrolyte composition may be impregnated into the interior of the electrode active material layer of the second electrode 130.

[0102] Therefore, the adhesiveness between the second electrolyte layer 150 and the second electrode 130 can be further improved, so that the interface resistance can be further reduced. In addition, through the polymer electrolyte impregnated into the second electrode 130, the ionic conductivity of the second electrode 130 can be further improved.

[0103] In some embodiments, the thermal polymerization reaction of the second electrolyte composition can be carried out at a temperature of 30 °C to 80 °C for 30 minutes to 24 hours.

[0104] In some embodiments, in the total weight of the second electrolyte composition, the content of the thermosetting compound in the second electrolyte composition can be 1 wt% to 80 wt%, for example, it can be 5 wt% to 50 wt% or 10 wt% to 40 wt%. Within the above range, the stability and the mechanical and physical properties of the electrolyte layer can be further improved, and the decrease in ionic conductivity caused by an excessive amount of polymer can be prevented.

[0105] According to an exemplary embodiment, the electrode structure 90 may not include a separator. For example, since the first electrolyte layer 140 is formed on the first electrode 100, short circuit between the first electrode 100 and the second electrode 130 can be prevented even without including a separator.

[0106] For example, when an electrolyte composition is injected between electrodes disposed opposite to each other, short circuit may occur between the electrodes. To prevent short circuit, a porous support such as a separator may be disposed between the electrodes, but due to the separator having low ionic conductivity, a non-capacitance region may be formed between the electrodes. In this case, the power characteristics and energy density of the lithium secondary battery may be reduced.

[0107] According to an exemplary embodiment, the first electrolyte layer 140 substantially prevents short circuit within the electrode structure 90, and thus the electrode structure 90 may not include a separator. Accordingly, a lithium secondary battery having high power and high capacity can be provided.

[0108] In some embodiments, the first electrolyte layer 140 may cover the entire surface of the first electrode 100 disposed opposite to the second electrode 130. Accordingly, direct contact between the first electrode 100 and the second electrode 130 can be prevented, and thus the fire prevention stability of the electrode structure can be further improved.

[0109] In some embodiments, the first electrolyte composition and the second electrolyte composition may include a lithium salt, an organic solvent, or a plasticizer. For example, the first electrolyte composition and the second electrolyte composition may include a liquid electrolyte.

[0110] In one embodiment, the content of the lithium salt respectively included in the first electrolyte composition and the second electrolyte composition may be 0.01 M to 5 M in each electrolyte composition, for example, it may be 0.1 M to 3 M. Within the above range, the resistance and ionic conductivity of the electrolyte layer can be further improved without reducing the thermal stability and chemical stability.

[0111] In some embodiments, the second electrolyte composition may further include an oxide-based solid electrolyte. In one embodiment, the first electrolyte composition may also include an oxide-based solid electrolyte.

[0112] The oxide-based solid electrolyte has high ionic conductivity, and thus can improve the ionic conductivity of the electrolyte layers (140, 150). For example, through the oxide-based solid electrolyte, the ionic conductivity of the polymer electrolyte can be supplemented, thereby improving the power characteristics and capacity characteristics of the secondary battery, and further improving safety.

[0113] According to an exemplary embodiment, the content (by weight %) of the oxide-based solid electrolyte in the first electrolyte composition may be less than the content (by weight %) of the oxide-based solid electrolyte in the second electrolyte composition. For example, the content of the oxide-based solid electrolyte in the first electrolyte layer 140 may be less than the content of the oxide-based solid electrolyte in the second electrolyte layer 150.

[0114] The oxide-based solid electrolyte has a high reflectivity to light, so the light reflection of the electrolyte composition may increase as the content of the oxide-based solid electrolyte increases. Since the light irradiated onto the electrolyte composition is reflected by the oxide-based solid electrolyte, the photopolymerizable compound or photoinitiator may not transmit and absorb sufficient light energy. In this case, fewer free radicals or reactive molecules may be formed within the electrolyte composition, thereby reducing the polymerization reactivity, and the polymerization rate and crosslink density may decrease.

[0115] According to an exemplary embodiment, since the second electrolyte layer 150 is formed by a thermal polymerization reaction, a high polymerization reaction rate and crosslink density can be maintained even when the content of the oxide-based solid electrolyte in the second electrolyte composition is high.

[0116] By making the first electrolyte composition that undergoes a photopolymerization reaction contain a relatively low content of the oxide-based solid electrolyte, a decrease in the polymerizability and mechanical stability of the first electrolyte layer 140 can be prevented. In addition, by making the second electrolyte composition contain a relatively high content of the oxide-based solid electrolyte, the ionic conductivity of the electrode structure 90 can be supplemented, and the power and capacity of the secondary battery can be further improved.

[0117] In some embodiments, in the total weight of the first electrolyte composition, the content of the oxide-based solid electrolyte in the first electrolyte composition may be 30 wt% or less. For example, in the total weight of the first electrolyte layer, the content of the oxide-based solid electrolyte in the first electrolyte layer 140 may be 30 wt% or less.

[0118] In one embodiment, in the total weight of the first electrolyte composition, the content of the oxide-based solid electrolyte in the first electrolyte composition may be greater than 0 wt% and 30 wt% or less, greater than 0 wt% and 20 wt% or less, greater than 0 wt% and 10 wt%, or greater than 0 wt% and 5 wt% or less.

[0119] When the content of the oxide-based solid electrolyte in the first electrolyte composition is greater than 30 wt%, the crosslink density and polymerizability of the first electrolyte layer 140 may decrease.

[0120] In some embodiments, in the total weight of the second electrolyte composition, the content of the oxide-based solid electrolyte in the second electrolyte composition may be less than 70% by weight. For example, in the total weight of the second electrolyte layer, the content of the oxide-based solid electrolyte in the second electrolyte layer 150 may be less than 70% by weight.

[0121] In one embodiment, in the total weight of the second electrolyte composition, the content of the oxide-based solid electrolyte in the second electrolyte composition may be greater than 0% by weight and less than 70% by weight, more than 10% by weight and less than 70% by weight, or greater than 20% by weight and 50% by weight.

[0122] Within the above range, the mechanical and physical properties and the structural stability of the second electrolyte layer 150 can be further improved, and the ionic conductivity and power characteristics of the secondary battery can be further enhanced.

[0123] In some embodiments, the first electrolyte layer 140 or the first electrolyte composition may not contain an oxide-based solid electrolyte. In one embodiment, the second electrolyte layer 150 or the second electrolyte composition may also not contain an oxide-based solid electrolyte.

[0124] In some embodiments, the oxide-based solid electrolyte may include a metal oxide or an oxygen-containing ion-conductive compound.

[0125] Examples of the oxide-based solid electrolyte may include metal oxides such as Al2O3, ZnO2, Ce2O3, TiO2, ZrO2, HfO2, MnO2, MgO, WO2, V2O5, garnet-based compounds, perovskite-based compounds, sodium superionic conductor (NASICON)-based compounds, lithium phosphorus oxynitride (LIPON)-based compounds, Li6La2CaTa2O 12 、Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 、Li3BO 2.5 N 0.5 、Li9SiAlO8 and other ion-conductive compounds.

[0126] The NASICON-based compound may include a phosphate-based compound. For example, it may include Li 1+ x Al x Ge 2-x (PO4)3 (0 < x < 2) and other lithium aluminium germanium phosphate (LAGP)-based compounds or Li1+x Al x Ti 2-x (PO4)3(0 < x < 2), Li 1+x Ti 2-x-y Al x Si y (PO4) 3-y (0 ≤ x ≤ 1, 0 < y ≤ 1), etc., lithium aluminum titanium phosphate (LATP) - based compounds, LiAl x Zr 2-x (PO4)3(0 ≤ x ≤ 1, 0 ≤ y ≤ 1), LiTi x Zr 2-x (PO4)3(0 ≤ x ≤ 1, 0 ≤ y ≤ 1), etc.

[0127] The perovskite - based compound may include Li 0.5 La 0.5 TiO3 and other lithium lanthanum titanate (LLTO) - based compounds.

[0128] The garnet - based compound may include lithium lanthanum zirconium oxide (LLZO) - based compounds. For example, the LLZO - based compound may include an oxide represented by the following Chemical Formula 1.

[0129] [Chemical Formula 1]

[0130] Li 7-3x+y-z A x La 3-y B y Zr 2-z M z O 12

[0131] In Chemical Formula 1, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1 may hold. A may be a doping element substituting the Li site, B may be a doping element substituting the La site, and M may be a doping element substituting the Zr site. A and B may each independently include at least one selected from aluminum (Al), gallium (Ga), barium (Ba), magnesium (Mg), calcium (Ca), strontium (Sr), potassium (K), cerium (Ce), and rubidium (Rb). M may include at least one selected from molybdenum (Mo), tungsten (W), antimony (Sb), yttrium (Y), niobium (Nb), and tantalum (Ta).

[0132] In some embodiments, when the electrode structure 90 includes an oxide-based solid electrolyte, the total content of the oxide-based solid electrolyte may be 5 wt% or more, 10 wt% or more, or 15 wt% or more of the total weight of the first electrolyte layer 140 and the second electrolyte layer 150, and may be 50 wt% or less, 40 wt% or less, or 30 wt% or less. Within the above ranges, a decrease in the thermal stability and chemical stability of the electrolyte layer can be prevented, and at the same time, the high-rate characteristics and power characteristics of the electrode structure 90 can be further improved.

[0133] In some embodiments, the first electrolyte layer 140 or the second electrolyte layer 150 may further include a sulfide-based solid electrolyte.

[0134] For example, the sulfide-based solid electrolyte may be an LPS-based solid electrolyte containing Li, P, and S, an LGPS-based solid electrolyte containing Li, P, Ge, and S, or an LSiPSCl-based solid electrolyte containing Li, Si, P, S, and Cl.

[0135] For example, the sulfide-based solid electrolyte may use Li2S-P2S5, Li 10 GeP2S 12 , Li 10 SnP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li 10 (Ge 0.5 Sn 0.5 )P2S 12 , Li 10 (Si 0.5 Sn 0.5 )P2S 12 , Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li9P3S9O3, Li 10.35 Ge 1.35 P 1.65 S 12 , Li 10.35 Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P2.19 S 12 、 Li 9.42 Si 1.02 P 2.1 S 9.96 O 2.04 、 Li6PS5Cl, etc.

[0136] In one embodiment, the viscosity of the second electrolyte composition can be higher than that of the first electrolyte composition. For example, the second electrolyte composition contains a relatively high content of oxide-based solid electrolyte, so the viscosity of the second electrolyte composition can be increased.

[0137] In one embodiment, the thickness of the first electrolyte layer 140 can be from 10 μm to 100 μm. For example, it can be from 40 μm to 80 μm or from 10 μm to 50 μm. Within the above range, the ionic conductivity can be improved while preventing an increase in resistance and short circuit, and the power characteristics of the secondary battery can be further improved.

[0138] In one embodiment, the thickness of the second electrolyte layer 150 can be from 10 μm to 150 μm. For example, it can be from 50 μm to 120 μm or from 20 μm to 50 μm. Within the above range, the low-resistance characteristics and mechanical and physical properties of the second electrolyte layer 150 can be further improved, and the capacity and life characteristics of the secondary battery can be further enhanced.

[0139] In some embodiments, the thickness of the second electrolyte layer 150 can be greater than that of the first electrolyte layer 140. Since the first electrolyte layer 140 has a thin thickness, a short circuit between the first electrode and the second electrode can be prevented, and at the same time, the energy density per unit volume and the low-resistance characteristics of the electrode structure can be further improved.

[0140] The second electrolyte layer 150 can act as a support layer between the first electrode and the second electrode. Therefore, since the second electrolyte layer 150 has a relatively large thickness, the elastic force, physical strength, crack resistance, etc. of the second electrolyte layer 150 can be further improved.

[0141] In one embodiment, the thickness of the first electrolyte layer 140 can be greater than that of the second electrolyte layer 150. For example, by calendering and heat-treating the second electrolyte composition, the second electrolyte layer 150 with a relatively thin thickness can be formed.

[0142] In some embodiments, the first electrode 100 may be a lithium electrode, and the second electrode 200 may be a positive electrode or a negative electrode having an electrode active material layer. For example, in the case of thermal polymerization, the time required for the polymerization reaction may be relatively long. Therefore, since the second electrode 200 has a form of an electrode active material layer including pores, the impregnation of the electrolyte into the second electrode 200 during the polymerization reaction can be increased.

[0143] In some embodiments, the first electrode 100 may be a positive electrode. For example, the first electrode 100 may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The second electrode 130 may be a negative electrode or a lithium electrode.

[0144] The positive electrode current collector may include, for example, stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof. For example, it may include aluminum or an aluminum alloy.

[0145] The positive electrode active material layer may contain a positive electrode active material. Examples of the positive electrode active material may include one or more compounds selected from lithium iron phosphate-based compounds, lithium cobalt-based oxides, lithium manganese-based oxides, lithium nickel-based oxides, or lithium composite oxides, etc. For example, the positive electrode active material may include layered compounds such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2VO7, lithium iron phosphate oxide such as LiFePO4, etc.

[0146] In one embodiment, the positive electrode active material may include a compound represented by the following Chemical Formula 2.

[0147] [Chemical Formula 2]

[0148] Li a Ni b M 1-b O2

[0149] In Chemical Formula 2, 0.95 ≤ a ≤ 1.08, b ≥ 0.5, and M may be at least one element selected from Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Ba, and Zr.

[0150] In one embodiment, the positive electrode active material may contain nickel (Ni), and may further contain at least one of cobalt (Co) or manganese (Mn). For example, nickel-cobalt-manganese (NCM)-based lithium oxide may be used as the positive electrode active material.

[0151] For example, nickel (Ni) can be provided as a metal related to the capacity of a lithium secondary battery. As the nickel content increases, the capacity and power of the lithium secondary battery can be improved, but when the nickel content increases excessively, the lifespan may be shortened, and it may be disadvantageous in terms of mechanical stability and electrical stability.

[0152] In one embodiment, the conductivity or resistance of a lithium secondary battery can be improved by cobalt (Co), and the mechanical stability and electrical stability of the lithium secondary battery can be improved by manganese (Mn).

[0153] The chemical structure represented by Chemical Formula 2 represents the bonding relationship included in the lattice structure or crystal structure of the positive electrode active material, and does not exclude other additional elements. For example, M can be provided as the main active element of the positive electrode active material. Chemical Formula 2 is provided to represent the bonding relationship of the main active element, and it should be understood that Chemical Formula 2 is a formula including the introduction and substitution of additional elements.

[0154] In one embodiment, in addition to including the main active element, an auxiliary element for enhancing the chemical stability of the positive electrode active material or the crystal structure can be further included. The auxiliary element can be mixed into the crystal structure together and form a bond, and it should be understood that this situation is also included within the scope of the chemical structure represented by Chemical Formula 2.

[0155] According to an exemplary embodiment, the positive electrode active material layer can further include a conductive material.

[0156] The conductive material can be included to promote electron migration between positive electrode active material particles. For example, the conductive material can include carbon-based conductive materials such as graphite, carbon black, graphene, carbon nanotubes, etc. and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc.

[0157] In some embodiments, the positive electrode active material layer can further include a positive electrode binder. For example, the positive electrode binder can include organic binders such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, etc.; water-based binders such as styrene-butadiene rubber (SBR).

[0158] In some embodiments, the first electrode 100 may be a negative electrode. For example, the first electrode 100 may include a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The second electrode 130 may be a positive electrode or a lithium electrode.

[0159] The negative electrode current collector may include gold, stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof. For example, it may include copper or a copper alloy.

[0160] The negative electrode active material layer may contain a negative electrode active material. The negative electrode active material may be a material known in the art for allowing lithium ions to be intercalated and deintercalated without particular limitation. For example, the negative electrode active material may use carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.; lithium alloys; silicon or tin, etc. As an example of the amorphous carbon, hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1500 °C or lower, mesophase pitch-based carbon fiber (MPCF), etc. may be cited. As an example of the crystalline carbon, graphite-based carbon such as natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc. may be cited. As an element contained in the lithium alloy, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc. may be cited.

[0161] The negative electrode active material layer may further contain a negative electrode binder and / or a negative electrode conductive material. The negative electrode binder and conductive material may be substantially the same or similar materials as the above-mentioned positive electrode binder and conductive material. For example, the negative electrode binder may be an aqueous binder such as styrene-butadiene rubber (SBR). The negative electrode binder may be used together with a thickener such as carboxymethyl cellulose (CMC).

[0162] The tabs (positive electrode tab and negative electrode tab) may respectively protrude from the positive electrode current collector and the negative electrode current collector and extend to one side of the housing of the secondary battery. The tabs may be fused to the one side of the housing and form electrode leads (positive electrode lead and negative electrode lead) extending to the outside of the housing or exposed to the outside of the housing.

[0163] The lithium secondary battery according to an exemplary embodiment may include the above electrode structure. For example, the lithium secondary battery may be provided as an all-solid battery.

[0164] According to an exemplary embodiment, a battery cell may be defined by the above electrode structure, and an electrode assembly may be formed by stacking a plurality of the battery cells.

[0165] In one embodiment, since no separator is provided between the first electrode and the second electrode, an electrode assembly can be formed by stacking a plurality of electrode structures. Therefore, the space for winding and folding the separator is not required, and the internal space efficiency of the electrode assembly can be improved, thereby increasing the capacity.

[0166] In addition, the first electrolyte layer is directly formed on the first electrode, and the second electrolyte layer is directly formed on the first electrolyte layer and the second electrode, thereby preventing an internal short circuit due to misalignment of the electrode structures.

[0167] The electrode assembly can be housed in a case, thereby defining a lithium secondary battery. The lithium secondary battery can be made, for example, in a cylindrical shape using a can, a prismatic shape, a pouch type, a coin type, or the like.

[0168] The lithium secondary battery according to an embodiment of the present invention can be widely applied to green technology fields such as electric vehicles, battery charging stations, other battery-utilizing solar power generation, and wind power generation. In addition, the lithium secondary battery according to an embodiment of the present invention can be used for eco-friendly electric vehicles (EVs) and hybrid vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions.

[0169] Hereinafter, in order to help understand the present invention, preferred embodiments are presented. However, these embodiments are only for illustrating the present invention and do not limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope and technical idea of the present invention, which is obvious to those skilled in the art. Such variations and modifications are naturally within the scope of the claims.

[0170] Production Example 1

[0171] (1) Production of a photocurable electrolyte layer (first electrolyte layer)

[0172] After dissolving 1.0 M LiPF6 in an organic solvent having a composition of EC / EMC (3:7, v / v), 2 parts by weight of fluoroethylene carbonate (FEC) is added to 100 parts by weight of the organic solvent to prepare a liquid electrolyte.

[0173] Poly(ethylene glycol) diacrylate (PEGDA), which is a photo-polymerizable compound, and 2-Hydroxy-2-methylpropiophenone (HMPP), which is a photoinitiator, are mixed into the liquid electrolyte to prepare a photo-curable electrolyte. The liquid electrolyte and PEGDA are mixed at a weight ratio of 8:2. 1 part by weight of HMPP is added relative to 100 parts by weight of PEGDA.

[0174] The photo-curable electrolyte and the oxide solid electrolyte prepared above are mixed in the ratio (weight ratio) shown in Table 1 below to prepare a photo-curable electrolyte composition. Al-doped LLZO (Li7La3Zr2O 12 )(Ampcera Inc.) is used as the oxide solid electrolyte.

[0175] 1 ml of the photo-curable electrolyte composition is coated on a release film, and then irradiated with ultraviolet light (UV) having a wavelength of 365 nm and an intensity of 1000 mW / cm 2 for 10 seconds to carry out a polymerization reaction, thereby manufacturing a solid electrolyte membrane.

[0176] During the above manufacturing process, whether the photo-curable electrolyte composition is slurried and whether the solid electrolyte membrane is cross-linked are observed and shown in Table 1 below.

[0177] (2) Manufacture of a thermosetting electrolyte layer (first electrolyte layer)

[0178] After dissolving 1.0 M LiPF6 in an organic solvent composed of EC / EMC (3:7, v / v), 2 parts by weight of FEC is added relative to 100 parts by weight of the organic solvent to prepare a liquid electrolyte.

[0179] PEGDA, which is a thermosetting compound, and tert-butyl peroxypivalate (t-BPP), which is a thermal initiator, are mixed into the liquid electrolyte to prepare a thermosetting electrolyte. The liquid electrolyte and PEGDA are mixed at a weight ratio of 9:1. 1 part by weight of t-BPP is added relative to 100 parts by weight of PEGDA.

[0180] The thermosetting electrolyte and the oxide solid electrolyte prepared above are mixed in the ratio (weight ratio) shown in Table 2 below to prepare a thermosetting electrolyte composition. Al-doped LLZO (Li7La3Zr2O 12 )(Ampcera Inc.) is used as the oxide solid electrolyte.

[0181] Apply 1 ml of the thermosetting electrolyte composition onto a release film, and then conduct a crosslinking reaction at a temperature of 60 °C in a vacuum oven for 30 minutes to fabricate a solid electrolyte membrane.

[0182] During the above manufacturing process, observe whether the thermosetting electrolyte composition is pulped and whether the solid electrolyte membrane is crosslinked, and the results are shown in Table 2 below.

[0183] [Table 1]

[0184]

[0185] [Table 2]

[0186]

[0187] In the "Whether Pulped" of Table 1 and Table 2 above, when the electrolyte slurry is in a high-viscosity slurry state and can be applied onto the release film, it is indicated as "O". In addition, when the electrolyte slurry has a very low viscosity and cannot be applied onto the release film, it is indicated as "X".

[0188] In the "Whether Crosslinked" of Table 1 and Table 2 above, when the solid electrolyte membrane is in a solid state with a certain shape, it is indicated as "O". When the solid electrolyte membrane does not have a certain shape and is in a liquid state or a high-viscosity slurry state, it is indicated as "X".

[0189] Referring to Table 1 and Table 2 above, in the case of the photocurable electrolyte composition, as the content of the oxide-based solid electrolyte increases, the crosslinking degree of the electrolyte layer decreases. For example, in the case of photocurable electrolyte composition 4 and photocurable electrolyte composition 5 where the content of the oxide-based solid electrolyte is 30 wt% or more of the total weight of the composition, as the crosslinking degree of the electrolyte membrane decreases, the electrolyte membrane does not have a certain shape and the lower end exists in a slurry state.

[0190] In the case of the thermosetting electrolyte composition, even if the content of the oxide-based solid electrolyte increases, the crosslinking degree of the electrolyte layer does not decrease. For example, in the case of an electrolyte composition where the content of the oxide-based solid electrolyte is 30 wt% or more of the total weight of the composition, a solid-state electrolyte membrane is also formed.

[0191] Therefore, since the second electrolyte layer is formed by a thermal curing process, a high content of the oxide-based solid electrolyte can be used, thereby supplementing the ionic conductivity and electrochemical safety of the polymer electrolyte layer.

[0192] Manufacturing Example 2

[0193] (1) Fabrication of the first electrode

[0194] Li[Ni 0.6 Co 0.2 Mn 0.2 O2, carbon black as the conductive material, and polyvinylidene fluoride (PVDF) as the binder are mixed at a weight ratio of 95:2.5:2.5 to prepare the first electrode paste. The first electrode paste is uniformly coated on an aluminum foil with a thickness of 12 μm and vacuum dried at 130 °C. The dried paste is calendered to manufacture the first electrode.

[0195] (2) Fabrication of the second electrode

[0196] Natural graphite as the active material, carbon black as the conductive material, and styrene-butadiene rubber (SBR) / carboxymethyl cellulose (CMC) as the binder are mixed at a weight ratio of 96:1:3 to prepare the second electrode paste. The second electrode paste is coated on a Cu foil with a thickness of 10 μm, and then dried and calendered to manufacture the second electrode.

[0197] (3) Fabrication of the electrode structure

[0198] Example 1

[0199] The photocurable electrolyte composition 1 is coated on the first electrode prepared above and calendered, and then irradiated with ultraviolet light (UV) with a wavelength of 365 nm and an intensity of 1000 mW / cm 2 for 10 seconds to form the first electrolyte layer (with a thickness of 20 μm).

[0200] After that, the second electrode is disposed on the first electrolyte layer at a predetermined interval to form an initial battery cell. The thermosetting electrolyte composition 6 is injected into the initial battery cell, and a crosslinking reaction is carried out at a temperature of 60 °C in a vacuum oven for 30 minutes to form the second electrolyte layer (with a thickness of 40 μm).

[0201] The electrode structure prepared above is assembled in a pouch-type battery packaging material.

[0202] Example 2

[0203] An electrode structure is fabricated by the same method as in Example 1, except that the thermosetting electrolyte composition 3 is used instead of the thermosetting electrolyte composition 6.

[0204] Example 3

[0205] An electrode structure is fabricated by the same method as in Example 1, except that the thermosetting electrolyte composition 1 is used instead of the thermosetting electrolyte composition 6.

[0206] Comparative Example 1

[0207] The photocurable electrolyte composition 1 was coated on the first electrode prepared above and rolled, and then irradiated with an LED lamp with a wavelength of 365 nm and an intensity of 1000 mW / cm 2 The first composite body was formed with a first electrolyte layer (having a thickness of 40 μm).

[0208] The photocurable electrolyte composition 1 was coated on the second electrode and rolled, and then irradiated with an LED light with a wavelength of 365 nm and an intensity of 1000 mW / cm 2 The second composite body was formed with ultraviolet rays (UV) of 40 μm for 10 seconds, in which the second electrolyte layer (with a thickness of 40 μm) was formed.

[0209] The first complex and the second complex are bonded so that the first electrolyte layer and the second electrolyte layer face each other.

[0210] The electrode structure prepared above is assembled into a soft pack battery outer packaging material.

[0211] Experimental Example 1: Evaluation of Interface Characteristics

[0212] A scanning electron microscope (SEM) image of a cross section of the electrode structure prepared above was taken using a scanning electron microscope (Apreo, Thermo Fisher).

[0213] Figure 6 This is a SEM image of a cross section of the electrode structure according to Example 1.

[0214] Reference Figure 6 , it can be confirmed that the electrode structure according to Example 1 has high adhesion at all interfaces within the electrode structure.

[0215] Figure 7 : is an SEM image of a cross section of the first electrolyte layer and the second electrolyte layer in the electrode structure according to Example 1.

[0216] Reference Figure 7 , the first electrolyte layer and the second electrolyte layer were in close contact with each other, and no lifting and peeling at the interface were observed.

[0217] Figure 8 This is an SEM image of a cross section of the first electrolyte layer and the second electrolyte layer in the electrode structure according to Comparative Example 1.

[0218] Reference Figure 8 , the adhesion between the first electrolyte layer and the second electrolyte layer decreases, and the interface between the electrolyte layers is unevenly formed, and warping at the interface or voids between the electrolyte layers are observed.

[0219] Experimental Example 2: Evaluation of charge-discharge characteristics

[0220] The battery prepared above was evaluated for charge and discharge with a constant current applied. Based on the current density of the first electrode, at room temperature, charging (CC-CV 0.2C, cut-off at 4.2V) and discharging (CC 0.2C, cut-off at 2.5V) were taken as one cycle, and the discharge capacity of each cycle was measured.

[0221] The measurement results are shown in the following Figure 9 and Table 3 below.

[0222] [Table 3]

[0223]

[0224] See Table 3 and Figure 9 , the lithium secondary battery cell according to the embodiment has improved interlayer adhesion and interface characteristics in the electrode structure body, and has a high initial capacity. In addition, the stability at the interface is improved, so the life characteristics are also improved. In Embodiment 1 and Embodiment 2, the electrolyte layer contains an oxide-based solid electrolyte, so the safety of the lithium secondary battery is further improved.

[0225] However, in the case of Comparative Example 1, the performance of the secondary battery is reduced as a whole. For example, the interface characteristics between the first electrolyte layer and the second electrolyte layer are reduced, and the initial capacity and cycle characteristics of the lithium secondary battery cell are reduced.

Claims

1. An electrode structure for a secondary battery, comprising: A first electrode; A first electrolyte layer formed on the first electrode, the first electrolyte layer containing a first polymer electrolyte; A second electrode disposed on the first electrolyte layer; And A second electrolyte layer formed between the first electrolyte layer and the second electrode, the second electrolyte layer containing a second polymer electrolyte, the second electrolyte layer having a composition or thickness different from that of the first electrolyte layer.

2. The electrode structure for a secondary battery according to claim 1, wherein, The first polymer electrolyte contains a polymer of a photopolymerizable compound and a lithium salt, and the second polymer electrolyte contains a polymer of a thermosetting compound and a lithium salt.

3. The electrode structure for a secondary battery according to claim 1, wherein, The second electrolyte layer further contains an oxide-based solid electrolyte.

4. The electrode structure for a secondary battery according to claim 3, wherein, The first electrolyte layer further contains an oxide-based solid electrolyte, The content of the oxide-based solid electrolyte in the first electrolyte layer is less than the content of the oxide-based solid electrolyte in the second electrolyte layer.

5. The electrode structure for a secondary battery according to claim 4, wherein, In the total weight of the first electrolyte layer, the content of the oxide-based solid electrolyte in the first electrolyte layer is greater than 0% by weight and 30% by weight or less.

6. The electrode structure for a secondary battery according to claim 4, wherein, In the total weight of the second electrolyte, the content of the oxide-based solid electrolyte in the second electrolyte layer is less than 70% by weight.

7. The electrode structure for a secondary battery according to claim 3, wherein, The first electrolyte layer does not contain an oxide-based solid electrolyte.

8. The electrode structure for a secondary battery according to claim 1, wherein, The thickness of the second electrolyte layer is greater than the thickness of the first electrolyte layer.

9. The electrode structure for a secondary battery according to claim 1, wherein, The first electrode includes a first current collector and a first electrode active material layer formed on the first current collector.

10. The electrode structure for a secondary battery according to claim 9, wherein, The first electrode active material layer contains the first polymer electrolyte.

11. The electrode structure for a secondary battery according to claim 9, wherein, The second electrode includes a second current collector and a second electrode active material layer formed on the second current collector, the second electrode active material layer containing the second polymer electrolyte.

12. A method for manufacturing an electrode structure for a secondary battery, comprising the following steps: Irradiating light onto a first electrolyte composition coated on a first electrode to form a first electrolyte layer; Disposing a second electrode on the first electrolyte layer at a predetermined interval to form an initial electrode structure; Injecting a second electrolyte composition into the initial electrode structure to fill the space between the first electrolyte layer and the second electrode; And Heating the initial electrode structure to form a second electrolyte layer between the first electrolyte layer and the second electrode.

13. The method for manufacturing an electrode structure for a secondary battery according to claim 12, wherein, The first electrolyte composition and the second electrolyte composition each contain a lithium salt and an organic solvent.

14. The method for manufacturing an electrode structure for a secondary battery according to claim 13, wherein, The first electrolyte composition further contains a photopolymerizable compound and a photoinitiator, and the second electrolyte composition further contains a thermosetting compound and a thermal initiator.

15. The method for manufacturing an electrode structure for a secondary battery according to claim 14, wherein, The second electrolyte composition further contains an oxide-based solid electrolyte.

16. The method for manufacturing an electrode structure for a secondary battery according to claim 15, wherein, The first electrolyte composition further contains an oxide-based solid electrolyte, The content of the oxide-based solid electrolyte in the first electrolyte composition is less than the content of the oxide-based solid electrolyte in the second electrolyte composition.

17. The method for manufacturing an electrode structure for a secondary battery according to claim 15, wherein, The first electrolyte composition does not contain an oxide-based solid electrolyte.

18. The manufacturing method of the electrode structure for a secondary battery according to claim 12, wherein, The viscosity of the second electrolyte composition is higher than that of the first electrolyte composition.

19. The method for manufacturing an electrode structure for a secondary battery according to claim 12, wherein, A part of the first electrolyte composition coated on the first electrode is impregnated into the interior of the first electrode. By irradiating light onto the first electrolyte composition, a crosslinked network derived from the first electrolyte composition is formed between the first electrolyte layer and the first electrode.

20. The manufacturing method of the electrode structure for a secondary battery according to claim 12, wherein, In the step of injecting the second electrolyte composition into the initial electrode structure, a part of the second electrolyte composition is impregnated into the interior of the second electrode.

Images