Electrode structure for lithium secondary battery and manufacturing method therefor

Abstract

An electrode structure for a lithium secondary battery according to exemplary embodiments may comprise: a negative electrode; and a composite electrolyte layer formed on the negative electrode and including an oxide-based electrolyte and a polymer electrolyte. The oxide-based electrolyte may include a sintered body, and the volume of the oxide-based electrolyte included in the composite electrolyte layer may be more than that of the polymer electrolyte included in the composite electrolyte layer. Accordingly, a lithium secondary battery having improved capacity characteristics and lifespan characteristics can be provided.

Description

Electrode structure for lithium secondary battery and manufacturing method thereof

[0001] The present disclosure relates to an electrode structure for a lithium secondary battery and a method for manufacturing the same. More specifically, the present disclosure relates to an electrode structure for a lithium secondary battery including a polymer electrolyte and a method for manufacturing the same.

[0002]

[0003] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as hybrid and electric vehicles.

[0004] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries, and among these, lithium secondary batteries are being widely developed due to their high operating voltage, energy density per unit weight, high charging speed, and lightweight properties.

[0005] Currently commercialized lithium secondary batteries primarily use liquid organic electrolytes, which boast high discharge capacity and energy density. However, liquid organic electrolytes can be susceptible to leakage, explosion, and fire due to rapid environmental changes, such as temperature fluctuations and external shocks.

[0006] Accordingly, solid electrolytes with high safety and reliability are being developed to replace liquid organic electrolytes. Examples of such solid electrolytes include polymer electrolytes and ceramic electrolytes. However, polymer electrolytes have low ionic conductivity, and ceramic electrolytes can exhibit uneven interfacial contact with the electrode.

[0007]

[0008] An object of the present disclosure is to provide an electrode structure for a lithium secondary battery with improved stability and electrochemical properties.

[0009] An object of the present disclosure is to provide a method for manufacturing an electrode structure for a lithium secondary battery having improved stability and electrochemical properties.

[0010]

[0011] An electrode structure for a secondary battery according to exemplary embodiments includes: a negative electrode; and a composite electrolyte layer formed on the negative electrode and including an oxide-based electrolyte and a polymer electrolyte, wherein the oxide-based electrolyte includes a sintered body, and a volume of the oxide-based electrolyte included in the composite electrolyte layer may be greater than a volume of the polymer electrolyte included in the composite electrolyte layer.

[0012] In some embodiments, the oxide electrolyte and the polymer electrolyte may be included in a volume ratio of 55:45 to 90:10.

[0013] In some embodiments, the oxide-based electrolyte is an LLZO-based compound, an LLTO-based compound, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (0≤x≤1, 0≤y≤1), LiAl x Zr 2-x (PO4)3(0≤x≤1, 0≤y≤1), LiTi x Zr 2-xIt may include at least one sintered body selected from the group consisting of (PO4)3(0≤x≤1, 0≤y≤1), LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, and NASICON-based compounds.

[0014] In some embodiments, the polymer electrolyte may be polymerized by including a monomer containing a (meth)acrylate group.

[0015] In some embodiments, the polymer electrolyte can be polymerized by including at least one monomer selected from the group consisting of trimethylolpropane triacrylate, di-trimethylolpropane tetraacrylate, trimethylolpropane ethoxylate triacrylate, butane diol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane trimethacrylate.

[0016] In some embodiments, the porosity of the composite electrolyte layer may be from 10% to 50% by volume.

[0017] In some embodiments, the composite electrolyte layer may contain at least one selected from the group consisting of phosphorus, sulfur, and fluorine without containing carbon.

[0018] In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.

[0019] In some embodiments, the negative active material layer may include at least one selected from the group consisting of a carbon-based active material and a silicon-based active material.

[0020] In some embodiments, the carbon-based active material may include at least one selected from the group consisting of crystalline carbon and amorphous carbon.

[0021] In some embodiments, the silicon-based active material is a carbon-silicon composite active material, silicon oxide (SiO x, 0 <x<2) 및 퓨어 실리콘으로 이루어진 군에서 선택되는 적어도 하나를 포함할 수 있다.

[0022] In some embodiments, the composite electrolyte layer may further include an anode disposed on the composite electrolyte layer.

[0023] In a method for manufacturing an electrode structure for a secondary battery according to exemplary embodiments, an oxide-based electrolyte composition may be applied onto a negative electrode. The applied oxide-based electrolyte composition may be sintered to form a preliminary composite electrolyte layer. A polymer electrolyte composition may be applied onto the preliminary composite electrolyte layer to form a composite electrolyte layer.

[0024] In some embodiments, the step of forming the preliminary composite electrolyte layer may include photosintering the applied oxide-based electrolyte composition at a temperature in the range of 400°C to 900°C.

[0025] In some embodiments, the step of forming the composite electrolyte layer may include thermally curing the applied polymer electrolyte composition.

[0026] In some embodiments, the thermal curing of the polymer electrolyte composition may be performed at a temperature of 50°C to 80°C.

[0027] In some embodiments, a portion of the polymer electrolyte composition applied on the preliminary composite electrolyte layer may be impregnated into the interior of the negative electrode.

[0028] In some embodiments, the oxide-based electrolyte composition may further include an oxide-based electrolyte, a binder, and a sintering aid.

[0029] In some embodiments, the polymer electrolyte composition may further comprise a polymer electrolyte, a lithium salt, and a thermal initiator.

[0030] In some embodiments, an anode may be disposed on the composite electrolyte layer.

[0031]

[0032] An electrode structure for a secondary battery according to the present disclosure may include a composite electrolyte layer formed on a negative electrode and including an oxide-based electrolyte and a polymer electrolyte. Since the oxide-based electrolyte has uniform interfacial bonding with the electrode and the polymer electrolyte has high electrochemical stability, the capacity characteristics and life characteristics of a secondary battery including the composite electrolyte layer may be improved.

[0033] For example, the oxide-based electrolyte can undergo a photosintering process. This can prevent the generation of impurities due to lithium volatilization, suppress cracking, and ensure sufficient interfacial contact between the oxide-based electrolyte and the electrode. Consequently, the lithium ion conductivity and energy density of the secondary battery can be improved.

[0034]

[0035] FIG. 1 is a schematic cross-sectional view illustrating an electrode structure for a secondary battery according to exemplary embodiments.

[0036] FIG. 2 is a schematic cross-sectional view illustrating an electrode structure for a secondary battery according to exemplary embodiments.

[0037] FIG. 3 is a schematic process flow diagram for explaining a method for manufacturing an electrode structure according to exemplary embodiments.

[0038] FIG. 4 is a schematic cross-sectional view showing a portion of an electrode structure according to exemplary embodiments.

[0039] FIGS. 5A and 5B are SEM images of cross-sections of the cathode and composite electrolyte layer of the electrode structure according to Example 1.

[0040] Figures 6a and 6b are SEM images of cross-sections of the cathode and composite electrolyte layer of the electrode structure according to Comparative Example 1.

[0041] Figure 7 shows the results of EDS (energy dispersive X-ray spectroscopy) analysis of carbon (C), sulfur (S), zirconium (Zr), and oxygen (O) on the cross-section of the cathode and composite electrolyte layer of the electrode structure according to Example 1.

[0042] Figure 8 shows the results of EDS (energy dispersive X-ray spectroscopy) analysis of carbon (C) on the cross-section of the cathode and composite electrolyte layer of the electrode structure according to Comparative Example 1.

[0043] Figure 9 is an SEM image of a cross-section of a composite electrolyte layer of an electrode structure according to Example 1.

[0044] Figure 10a is a graph of the charging curve of the secondary battery according to Example 1 and Comparative Example 1.

[0045] Figure 10b is a discharge curve graph of a secondary battery according to Example 1 and Comparative Example 1.

[0046] Figure 11 is a graph of discharge capacity according to cycle of the secondary battery according to Example 1 and Comparative Example 1.

[0047] Figure 12 is a graph of coulomb efficiency according to the cycle of the secondary battery according to Example 1 and Comparative Example 1.

[0048] Figure 13 is a photograph of the electrode structure of Comparative Example 2.

[0049]

[0050] According to embodiments provided by the present disclosure, an electrode structure is provided including a cathode and a composite electrolyte layer formed on the cathode.

[0051] According to embodiments provided by the present disclosure, a method of manufacturing the electrode structure is provided.

[0052] Unless otherwise defined herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0053] Unless otherwise specifically defined herein, when a part such as a layer, film, thin film, region, or plate is said to be “on” or “over” another part, this may include not only cases where it is “directly on” the other part, but also cases where there is another part in between.

[0054] Unless otherwise specifically defined herein, “(meth)acryl” may be used to mean both “methacryl” and “acryl.”

[0055] In this specification, "polymer electrolyte" may refer not only to an all-solid-state electrolyte, but also to a "gel polymer electrolyte" in which an electrolyte is included in a polymer-based electrolyte. For example, the gel polymer electrolyte may be manufactured by swelling an electrolyte after manufacturing a polymer matrix (physical gel), or by curing a composition in which an electrolyte and a monomer are mixed (chemical gel), depending on the manufacturing method.

[0056] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to the drawings. However, the following drawings attached to this specification illustrate some embodiments of the present disclosure and, together with the contents of the invention described above, serve to further understand the technical concept of the present disclosure. Therefore, the present disclosure should not be interpreted as being limited to the matters described in such drawings.

[0057] The terms “upper”, “lower”, “top”, “lower”, “bottom”, “first”, “second”, etc. used in this disclosure indicate the relative positions of each component and do not imply an absolute superior-subordinate relationship.

[0058]

[0059] <Electrode structure for lithium secondary batteries>

[0060] FIG. 1 is a schematic cross-sectional view showing an electrode structure for a lithium secondary battery according to exemplary embodiments.

[0061] Referring to FIG. 1, an electrode structure for a lithium secondary battery (hereinafter, abbreviated as “electrode structure”) may include a negative electrode (110) and a composite electrolyte layer (130) formed on the negative electrode (110). For example, the composite electrolyte layer (130) may cover the upper surface of the negative electrode (110) and may be in direct contact with the negative electrode (110).

[0062] The negative electrode (110) may include an electrode active material capable of absorbing and releasing lithium ions.

[0063] For example, the negative electrode (110) may include a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and may further include a conductive material, a binder, or a solid electrolyte.

[0064] In one embodiment, the negative electrode (110) may be a lithium electrode formed of lithium metal or a lithium alloy. For example, the lithium secondary battery may be provided as a lithium metal battery. Elements included in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium.

[0065] The negative electrode current collector may include gold, stainless steel, nickel, aluminum, titanium, copper or an alloy thereof, for example, copper or a copper alloy.

[0066] In some embodiments, the negative active material layer may include at least one selected from the group consisting of a carbon-based active material and a silicon-based active material.

[0067] In some embodiments, the carbon-based active material may include at least one selected from the group consisting of crystalline carbon and amorphous carbon.

[0068] For example, the crystalline carbon may include natural graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc., and the amorphous carbon may include hard carbon, coke, mesocarbon microbeads (MCMB) calcined at 1500°C or lower, mesophase pitch-based carbon fiber (MPCF), etc.

[0069] In some embodiments, the silicon-based active material is a carbon-silicon composite active material, silicon oxide (SiO x , 0 <x<2) 및 퓨어 실리콘으로 이루어진 군에서 선택되는 적어도 하나를 포함할 수 있다.

[0070] For example, the carbon-silicon composite active material may include carbon particles including micropores and a silicon coating formed inside and / or on the surface of the carbon particles. The carbon particles may include activated carbon, carbon nanotubes, carbon nanowires, graphene, carbon fibers, carbon black, graphite, porous carbon, pyrolyzed cryogel, pyrolyzed xerogel, and pyrolyzed aerogel.

[0071] In one embodiment, the negative electrode active material may be mixed and stirred with a binder, a conductive agent, and / or a dispersing agent in a solvent to prepare a slurry. After coating the slurry on a negative electrode current collector, the slurry may be compressed and dried to prepare a negative electrode active material layer.

[0072] The conductive material may be included to promote electron transfer between the negative electrode active materials. For example, the conductive material may include a carbon-based conductive material such as graphite, carbon black, graphene, carbon nanotubes, and / or a metal-based conductive material including a perovskite material such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0073] The above binder may include an organic binder such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, PPC-LiTFSI, or an aqueous binder such as SBR, and may be used together with a thickener such as CMC.

[0074] According to exemplary embodiments, the composite electrolyte layer (130) may include an oxide-based electrolyte and a polymer electrolyte.

[0075] For example, since the oxide-based electrolyte has uniform interfacial bonding with the electrode and the polymer electrolyte has high electrochemical stability, a secondary battery including a composite electrolyte layer (130) can have improved capacity characteristics and life characteristics.

[0076] In one embodiment, the oxide-based electrolyte may include a sintered body. For example, the sintered body may be obtained by photo-sintering or thermal sintering of the oxide-based electrolyte.

[0077] In one embodiment, the sintered body can be obtained by photosintering, and can be obtained by photosintering at a temperature in the range of, for example, 400°C to 900°C. For example, the photosintering can be performed at a temperature condition of 450°C to 850°C, 500°C to 800°C, 550°C to 750°C, 500°C to 700°C, 600°C to 800°C, or 600°C to 700°C.

[0078] When the oxide electrolyte is subjected to photosintering within the above temperature range, lithium deficiency and impurity generation due to lithium volatilization can be prevented, crack formation can be suppressed, and sufficient interfacial contact between the oxide electrolyte and the electrode can be achieved. Accordingly, the output characteristics, capacity characteristics, and life characteristics of the secondary battery can be improved.

[0079] In some embodiments, the oxide-based electrolyte is an LLZO-based compound, an LLTO-based compound, Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (0≤x≤1, 0≤y≤1), LiAl x Zr 2-x (PO4)3(0≤x≤1, 0≤y≤1), LiTi x Zr 2-x It may include at least one sintered body selected from the group consisting of (PO4)3(0≤x≤1, 0≤y≤1), LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, and NASICON-based compounds.

[0080] For example, the above sintered bodies are ion-conducting metal compounds containing oxygen, and have high ionic and electrical conductivities, so they can improve the conductivity of the composite electrolyte layer (130).

[0081] In some embodiments, the polymer electrolyte may be polymerized by including a monomer comprising a (meth)acrylate group, wherein the monomer may include 2 to 6, specifically 2 to 4, (meth)acrylate groups.

[0082] Specifically, the polymer electrolyte can be polymerized by including at least one monomer selected from the group consisting of trimethylolpropane triacrylate, di-trimethylolpropane tetraacrylate, trimethylolpropane ethoxylate triacrylate, butane diol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane trimethacrylate.

[0083] For example, the polymer electrolyte can be evenly distributed in the oxide-based electrolyte. Accordingly, the stability of the composite electrolyte layer (130) can be further improved, and a more stable electrode-electrolyte interface can be formed.

[0084] According to exemplary embodiments, the volume of the oxide-based electrolyte included in the composite electrolyte layer (130) may be greater than the volume of the polymer electrolyte included in the composite electrolyte layer (130). The volume may refer to a volume-based content.

[0085] For example, the composite electrolyte layer (130) may be a free-standing layer that maintains a certain shape without being supported by other materials, and the oxide-based electrolyte may function as a support or frame to maintain the shape of the composite electrolyte layer (130).

[0086] Therefore, when the volume of the oxide-based electrolyte included in the composite electrolyte layer (130) is less than the volume of the polymer electrolyte, the shape of the composite electrolyte layer (130) collapses, making it difficult to manufacture the electrode structure described above, and the long-term life characteristics of the lithium secondary battery may deteriorate.

[0087] In some embodiments, the oxide electrolyte and the polymer electrolyte may be included in a volume ratio of 55:45 to 90:10.

[0088] For example, the mixing volume ratio of the oxide electrolyte and the polymer electrolyte included in the composite electrolyte layer (130) may be 51:49 to 95:5, 55:45 to 90:10, 55:45 to 80:20, 65:35 to 90:10, 65:35 to 85:15, 70:30 to 90:10, 70:30 to 85:15, 70:30 to 80:20, or 75:25 to 80:20.

[0089] Within the above range, the shape of the composite electrolyte layer (130) can be maintained, thereby improving the structural stability of the electrode structure, and enhancing electrode / electrolyte interface adhesion and lithium ion conductivity. Accordingly, the capacity characteristics, life characteristics, and safety of a secondary battery including the composite electrolyte layer (130) can be improved.

[0090] For example, if the above mixing volume ratio is outside the above-described range, the composite electrolyte layer (130) may become brittle or ductile rapidly.

[0091] In some embodiments, the porosity of the composite electrolyte layer (130) may be from 10% to 50% by volume. For example, the porosity of the composite electrolyte layer (130) may be from 5% to 55% by volume, from 10% to 40% by volume, from 15% to 30% by volume, or from 18% to 25% by volume.

[0092] For example, the oxide-based electrolyte may have a porous structure. Accordingly, when the porosity satisfies the above-described range, the polymer electrolyte can be evenly distributed in the oxide-based electrolyte, and the stability of the composite electrolyte layer (130) can be further improved.

[0093] For example, an oxide-based electrolyte having the above porous structure can be obtained through photosintering.

[0094] In some embodiments, the composite electrolyte layer (130) may contain at least one selected from the group consisting of phosphorus, sulfur, and fluorine without containing carbon.

[0095] In one embodiment, the composite electrolyte layer (130) may contain sulfur without containing carbon.

[0096] For example, the pores of the oxide electrolyte can be filled with a polymer electrolyte containing one or more elements selected from the group consisting of phosphorus, sulfur, and fluorine.

[0097] Accordingly, in the composite electrolyte layer (130) in which the polymer electrolyte is evenly distributed in the oxide-based electrolyte, no carbon atoms remain, and one or more of the elements listed above can be distributed within the pores of the oxide-based electrolyte. Accordingly, electrode / electrolyte interface bonding and lithium ion conductivity can be improved.

[0098] For example, when an oxide electrolyte is sintered by light irradiation, carbon volatilization may occur, creating pores, and the polymer electrolyte may be incorporated into the pores.

[0099] In some embodiments, the composite electrolyte layer (130) may include a lithium salt and an organic solvent. The lithium salt may secure a passage for lithium ions to move within the composite electrolyte layer (130), thereby further improving the output characteristics of the secondary battery.

[0100] For example, the lithium salts include 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 and LiC(CF3SO2)3.

[0101] For example, the organic solvent may be at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate (DPC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoroethylene carbonate (TFEC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran.

[0102] In some embodiments, the negative electrode (110) may include the polymer electrolyte and the lithium salt. For example, at least a portion of the polymer electrolyte included in the composite electrolyte layer (130) may be impregnated into the negative electrode (110).

[0103] Accordingly, the interfacial resistance between the cathode (110) and the composite electrolyte layer (130) can be further reduced. In addition, as the cathode (110) includes a polymer electrolyte, the ionic conductivity and energy density within the cathode (110) can be further increased.

[0104] FIG. 2 is a schematic cross-sectional view of an electrode structure for a secondary battery according to exemplary embodiments.

[0105] Referring to FIG. 2, the electrode structure (90) may include a cathode (110) and an anode (120) facing the cathode (110), and the anode (120) may be disposed on a composite electrolyte layer (130). For example, the anode (120) may cover the upper surface of the composite electrolyte layer (130) and may be in direct contact with the composite electrolyte layer (130).

[0106] For example, the positive electrode (120) may include a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material capable of absorbing and releasing lithium ions, and may further include a conductive material, a binder, or a solid electrolyte.

[0107] In one embodiment, the positive electrode (120) may be a lithium electrode formed of lithium metal or a lithium alloy.

[0108] The positive electrode current collector may comprise, for example, stainless steel, nickel, aluminum, titanium, copper or an alloy thereof, and may comprise, for example, aluminum or an aluminum alloy.

[0109] The positive electrode active material layer may include a positive electrode active material. As an example of the positive electrode active material, it may include one or more compounds selected from lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, or lithium composite oxide. For example, the positive electrode active material may include a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or lithium manganese oxide such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); LiV3O8, LiFe3O4, V2O 5　 And it may include vanadium oxide such as Cu2VO7, lithium iron phosphate oxide, etc.

[0110] In some embodiments, the positive electrode active material may include a compound having a structure represented by the following chemical formula 1.

[0111] [Chemical Formula 1]

[0112] Li 1+a Ni 1-(x+y) Co x M y O2

[0113] In the above chemical formula 1, -0.05≤α≤0.15, 0.01≤x≤0.3, 0.01≤y≤0.3, and M may include at least one element selected from the group consisting of Mn, Mg, Sr, Ba, B, Al, Si, Ti, Zr, and W.

[0114] In one embodiment, the positive electrode active material includes nickel (Ni) and may further include at least one of cobalt (Co) and manganese (Mn). For example, a nickel-cobalt-manganese (NCM) lithium oxide may be used as the positive electrode active material.

[0115] For example, nickel (Ni) can be provided as a metal associated with the capacity of lithium secondary batteries. While a higher nickel content can improve the capacity and output of a lithium secondary battery, excessive nickel content can shorten its lifespan and compromise mechanical and electrical stability.

[0116] In one embodiment, the conductivity or resistance of a lithium secondary battery can be improved by cobalt (Co), and the mechanical and electrical stability of a lithium secondary battery can be improved by manganese (Mn).

[0117] The chemical structure represented by the above chemical formula 1 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.

[0118] In one embodiment, the positive electrode active material may be mixed and stirred with a binder, a conductive agent, and / or a dispersing agent in a solvent to produce a slurry. After coating the slurry on a positive electrode current collector, the slurry may be compressed and dried to produce a positive electrode active material layer.

[0119] Materials substantially identical or similar to those used in the manufacture of the negative electrode active material layer as the above binder and conductive material may be used.

[0120] For example, since the composite electrolyte layer (130) mediates the movement of ions and electrons between the cathode (110) and the anode (120), the ionic conductivity of the electrode structure (90) can be increased even if the electrode structure (90) is not impregnated with a liquid electrolyte. Accordingly, the output and capacity characteristics of the secondary battery can be improved.

[0121] In addition, leakage, ignition, and vaporization due to liquid electrolyte can be prevented, and the flame retardancy, heat resistance, and structural stability of the electrode structure (90) can be improved.

[0122] In some embodiments, the electrode structure (90) may not include a separator. Since the free-standing composite electrolyte layer (130) blocks contact between the negative electrode (110) and the positive electrode (120), a short circuit between the negative electrode (110) and the positive electrode (120) can be prevented even without a separator.

[0123] For example, when the electrode structure (90) includes a separator, a non-capacitive region may be formed by the separator, which may lower the energy density of the electrode structure (90) and reduce ionic conductivity.

[0124] In some embodiments, the electrode structure (90) may not include a separator, so that the capacity and output characteristics of the lithium secondary battery may be further improved.

[0125] In some embodiments, the thickness of the composite electrolyte layer (130) may be 5 μm to 25 μm.

[0126] For example, the thickness of the composite electrolyte layer (130) may be 1 µm to 50 µm, 10 µm to 40 µm, 15 µm to 30 µm, or 20 µm to 25 µm. Within the above range, an electrode structure (90) with improved structural stability and ionic conductivity can be easily manufactured.

[0127] FIG. 3 is a schematic process flow diagram illustrating a method for manufacturing an electrode structure according to exemplary embodiments. Hereinafter, the method for manufacturing an electrode structure will be described with reference to FIG. 3.

[0128] Referring to FIG. 3, an oxide-based electrolyte composition can be applied onto a cathode (110). The applied oxide-based electrolyte composition can be sintered to form a preliminary composite electrolyte layer (e.g., step S10).

[0129] For example, in the step of forming the preliminary composite electrolyte layer, the sintering may be thermal sintering or optical sintering.

[0130] In some embodiments, the step of forming the preliminary composite electrolyte layer may include photosintering the applied oxide-based electrolyte composition at a temperature in the range of 400°C to 900°C.

[0131] For example, sintering can be performed by applying light having a wavelength ranging from 100 nm to 700 nm to the oxide-based electrolyte composition for 1 to 10 seconds. Accordingly, lithium contained in the oxide-based electrolyte can be prevented from volatilizing, and high ionic and electrical conductivity of the oxide-based electrolyte can be maintained.

[0132] The above oxide-based electrolyte composition can be photosintered at a temperature of, for example, 450°C to 850°C, 500°C to 800°C, 550°C to 750°C, 500°C to 700°C, 600°C to 800°C, or 600°C to 700°C.

[0133] Within the above temperature range, lithium deficiency and impurity generation in the oxide electrolyte can be suppressed, thereby improving the output characteristics and capacity characteristics of the secondary battery.

[0134] In some embodiments, the oxide-based electrolyte composition may include an oxide-based electrolyte, a binder, and a sintering aid.

[0135] In some embodiments, the oxide-based electrolyte composition may further include an organic solvent, a dispersant, and a plasticizer.

[0136] For example, the content of the oxide-based electrolyte may be 40 wt% to 60 wt%, 45 wt% to 60 wt%, 40 wt% to 55 wt%, 40 wt% to 50 wt%, 45 wt% to 55 wt%, or 45 wt% to 50 wt% of the total weight of the oxide-based electrolyte composition. Within the above range, the structural stability and ionic conductivity of the electrode structure (90) may be improved.

[0137] For example, the binder may include polyvinyl butyrate (PVB), polyvinylidene fluoride (PVDF), etc., the organic solvent may include N-methylpyrrolidone (NMP), toluene, etc., the dispersant may include Hypermer KD, etc., the plasticizer may include dibutyl phthalate (DBP), diethylhexyl phthalate (DEHP), etc., and the sintering aid may include lithium nitride (Li3N), etc.

[0138] For example, in the S20 process, a polymer electrolyte composition can be applied onto the preliminary composite electrolyte layer to form a composite electrolyte layer (130).

[0139] In some embodiments, the step of forming the composite electrolyte layer may include thermally curing the applied polymer electrolyte composition.

[0140] For example, when the polymer electrolyte composition is applied to the preliminary composite electrolyte layer, the liquid polymer electrolyte composition can impregnate the oxide-based electrolyte included in the preliminary composite electrolyte layer. When the polymer electrolyte composition is subsequently hardened by heat treatment, the polymer electrolyte can be inserted into the pores of the oxide-based electrolyte.

[0141] In some embodiments, the thermal curing of the polymer electrolyte composition may be performed at a temperature of 50°C to 80°C.

[0142] For example, the temperature conditions of the thermal curing may be 55°C to 80°C, 60°C to 80°C, 50°C to 75°C, 50°C to 70°C, or 50°C to 60°C. Within the above range, the polymer electrolyte can be evenly distributed in the oxide-based electrolyte.

[0143] In one embodiment, the thermal curing may be performed for 30 minutes to 2 hours, 30 minutes to 1 hour, or 1 hour to 2 hours.

[0144] In some embodiments, the polymer electrolyte composition may include a polymer electrolyte, a lithium salt, and a thermal initiator.

[0145] In some embodiments, the polymer electrolyte composition may further comprise an organic solvent.

[0146] For example, the content of the polymer electrolyte may be 1 wt% to 10 wt%, 3 wt% to 10 wt%, 5 wt% to 10 wt%, 1 wt% to 8 wt%, 3 wt% to 8 wt%, or 1 wt% to 5 wt% of the total weight of the polymer electrolyte composition. Within the above range, the electrochemical stability of the electrode structure (90) can be further improved while preventing a decrease in ionic conductivity within the electrode structure (90).

[0147] Examples of the lithium salt and the organic solvent include compounds of the types described above.

[0148] The above thermal initiator may include at least one selected from the group consisting of t-amyl peroxide, benzoyl peroxide, lauroyl peroxide, t-butylperoxypivalate, 1,1'-bis-(bis-t-butylperoxy)cyclohexane, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile), 2-cyano-2-propylazoformamide, 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(2-methylbutyronitrile).

[0149] In some embodiments, a portion of the polymer electrolyte composition applied on the preliminary composite electrolyte layer may be impregnated into the interior of the negative electrode (110).

[0150] For example, when the polymer electrolyte composition is applied to the preliminary composite electrolyte layer, the polymer electrolyte composition can penetrate the oxide electrolyte and reach the negative electrode current collector. Accordingly, the negative electrode (110) can have improved ionic conductivity and energy density by including the polymer electrolyte and the lithium salt.

[0151] In one embodiment, methods for applying the oxide-based electrolyte composition and polymer electrolyte composition may include, for example, gravure coating, die coating, multi-die coating, dip coating, and comma coating.

[0152] For example, in the S30 process, the positive electrode (120) can be placed on the composite electrolyte layer (130). For example, the S30 process can be performed by pressing the negative electrode (110) and the positive electrode (120) with a roll press while the composite electrolyte layer (130) and the positive electrode (120) are attached.

[0153] Accordingly, the electrode structure for the secondary battery described above can be manufactured.

[0154] FIG. 4 is a schematic cross-sectional view showing a portion of an electrode structure according to exemplary embodiments.

[0155] Referring to FIG. 4, the negative electrode (110) may include a negative electrode current collector (100) and a negative electrode active material layer (105) formed on the negative electrode current collector (100). The negative electrode active material layer (105) may be formed on both surfaces (e.g., the upper surface and the lower surface) of the negative electrode current collector (100).

[0156] The composite electrolyte layer (130) can be formed on the negative electrode active material layer (105). For example, an oxide-based electrolyte composition can be applied to the upper surface of the negative electrode active material layer (105) and then cured to form a preliminary composite electrolyte layer, and a polymer electrolyte composition can be applied to the preliminary composite electrolyte layer and then cured to form a composite electrolyte layer (130).

[0157] In Fig. 4, only the cathode and the composite electrolyte layer are shown for convenience of explanation, but the electrode structure may further include the anode by placing the anode on the composite electrolyte layer.

[0158] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may be formed on both surfaces (e.g., the upper surface and the lower surface) of the positive electrode current collector.

[0159] For example, electrode tabs (positive electrode tab and negative electrode tab) may protrude from the positive electrode current collector and the negative electrode current collector, respectively, and extend to one side of the case of the secondary battery. The electrode tabs may be fused together with the one side of the case to form electrode leads (positive electrode lead and negative electrode lead) that extend or are exposed to the outside of the case.

[0160] A lithium secondary battery according to exemplary embodiments may include the electrode structure described above. For example, the lithium secondary battery may be provided as an all-solid-state battery.

[0161] According to exemplary embodiments, an electrode cell is defined by the electrode structure described above, and a plurality of the electrode cells can be stacked to form an electrode assembly.

[0162] In one embodiment, a separator is not interposed between the cathode and anode, and thus an electrode assembly can be formed by laminating multiple electrode structures. Accordingly, space for winding and folding the separator is not required, and the internal space efficiency of the electrode assembly is improved, thereby increasing capacity.

[0163] The above electrode assembly may be housed within a case to define a lithium secondary battery. The lithium secondary battery may be manufactured in a cylindrical, square, pouch, or coin shape using, for example, a can.

[0164]

[0165] Hereinafter, preferred embodiments are presented to help understand the present disclosure, but these embodiments are only illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0166]

[0167] Manufacturing example

[0168] (1) Preparation of oxide-based electrolyte composition

[0169] After adding 0.1 g of BH-S (polyvinyl butyrate (PVB) system) as a binder, 0.1 g of Hypermer KD-6 (manufactured by Croda) as a dispersant, and 0.1 g of dibutyl phthalate (DBP) as a plasticizer to a solvent containing 0.51 g of NMP and 0.79 g of toluene, stirring was repeated twice at 3000 rpm for 5 minutes using a thinky mixer to obtain a stirred solution.

[0170] LLZO(Li) was added to the obtained stirred solution 6.4 La3Zr 1.4 Ta 0.6 O 12 ) 1.5 g of powder and 0.015 g of lithium nitride (Li3N), a sintering agent, were added, and stirred at 3000 rpm for 5 minutes to prepare an oxide-based electrolyte composition.

[0171] (2) Preparation of polymer electrolyte composition

[0172] A polymer electrolyte composition was prepared by adding 5 wt% of trimethylolpropane ethoxylate triacrylate (TMPETA), 1 wt% of t-butylperoxypivalate (t-BPP), 16.9 wt% of LiTFSI, 2.1 wt% of LiDFOB, and 60.6 wt% of LiPF to a solvent containing 50.7 wt% of EMC and 23.7 wt% of FEC.

[0173] (3) Manufacturing of cathode

[0174] An anode slurry was prepared by mixing artificial graphite as an active material, carbon nanotubes (CNTs) as a conductive material, and SBR as a binder in a weight ratio of 92:5:3. The anode slurry was applied onto a 15 μm thick Cu foil, followed by drying and rolling to prepare an anode.

[0175] (4) Manufacturing of anode

[0176] Li[Ni as an active material 0.6 Co 0.2 Mn 0.2 ]O 2, A cathode slurry was prepared by mixing carbon black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 92:5:3. The cathode slurry was uniformly applied to a 15 μm thick aluminum foil and vacuum-dried at 130°C. The dried slurry was rolled to prepare a cathode.

[0177]

[0178] Example 1

[0179] The oxide-based electrolyte composition was applied onto the cathode, and sintered by heat treatment at a temperature of 600°C by irradiating ultraviolet and visible light for 5 seconds using a photo-sintering device (manufactured by PulseForge, model name Invent, operating voltage 300 V, pulse duration 3000 μs, pulse count 10 times, duty cycle 62%, 20 Hz, 100 repetitions). Thereafter, the composition was dried at 85°C for 2 hours to form a preliminary composite electrolyte layer including the oxide-based electrolyte.

[0180] Afterwards, 30 μL of the polymer electrolyte composition was applied onto the preliminary composite electrolyte layer, and left at a temperature of 60°C for 1 hour to form a composite electrolyte layer.

[0181] An electrode structure manufactured so that the composite electrolyte layer and the anode face each other was assembled into a cell outer shell.

[0182]

[0183] Comparative Example 1

[0184] A preliminary composite electrolyte layer including an oxide-based electrolyte, a composite electrolyte layer, and an electrode structure were manufactured in the same manner as in Example 1, except that the process of sintering the oxide-based electrolyte composition applied on the cathode by irradiating it with ultraviolet and visible light was not performed.

[0185] The above-mentioned manufactured electrode structure was assembled into a cell outer shell.

[0186]

[0187] Comparative Example 2

[0188] A preliminary composite electrolyte layer including an oxide-based electrolyte, a composite electrolyte layer having a polymer electrolyte volume ratio greater than that of the oxide-based electrolyte, and an electrode structure were manufactured in the same manner as in Example 1, except that 300 μL of the polymer electrolyte composition was applied on the preliminary composite electrolyte layer instead of 30 μL.

[0189] The above-mentioned manufactured electrode structure was assembled into a cell outer shell.

[0190] Figure 13 is a photograph of the electrode structure of Comparative Example 2.

[0191] As can be seen in Fig. 13, Comparative Example 2, which had a higher volume ratio of polymer electrolyte, did not maintain the shape of the electrode structure and was therefore not subjected to further evaluation.

[0192]

[0193] Experimental example

[0194] 1. SEM image analysis of the electrode cross-section

[0195] A scanning electron microscope (SEM) image was taken of the cross-section of the electrode structure manufactured above using a scanning electron microscope (SU-8010, HITACHI).

[0196] FIGS. 5A and 5B are SEM images of cross-sections of the cathode and composite electrolyte layer of the electrode structure according to Example 1.

[0197] FIG. 6a and FIG. 6b are SEM (scanning electron microscope) images of cross-sections of the cathode and composite electrolyte layer of the electrode structure according to Comparative Example 1.

[0198] Referring to FIGS. 5a, 5b, 6a, and 6b, the composite electrolyte layer (thickness 23.32 μm) of Example 1 had a porous structure, and the composite electrolyte layer (thickness 28.28 μm) of Comparative Example 1 had a dense structure.

[0199] Accordingly, it can be seen that in the composite electrolyte layer of Example 1, the polymer electrolyte can sufficiently penetrate through the pores of the oxide-based electrolyte.

[0200]

[0201] 2. Analysis of EDS element mapping images of the electrode cross-section

[0202] In the cross-section of the electrode structure manufactured above, the element distribution (carbon (C), sulfur (S), zirconium (Zr), oxygen (O)) was confirmed according to energy dispersive spectroscopy (EDS).

[0203] Figure 7 shows the EDS analysis results of C, S, Zr, and O for the cross-section of the cathode and composite electrolyte layer of the electrode structure according to Example 1.

[0204] Figure 8 is an EDS analysis result of C for a cross-section of the cathode and composite electrolyte layer of the electrode structure according to Comparative Example 1.

[0205] Referring to Fig. 7, since no carbon element is detected in the composite electrolyte layer of Example 1, it can be seen that carbon volatilization occurred during sintering by visible light irradiation. In addition, since sulfur element is detected in the pores of the oxide-based electrolyte, it can be seen that the polymer electrolyte is evenly distributed in the oxide-based electrolyte.

[0206] Referring to Fig. 8, since carbon elements are detected in the composite electrolyte layer of Comparative Example 1, it can be seen that carbon volatilization did not occur and the binder component remained.

[0207] Therefore, the stability and lithium ion conductivity of the composite electrolyte layer of Example 1 are improved, and a more stable electrode-electrolyte interface can be formed.

[0208]

[0209] 3. Porosity evaluation

[0210] A pore analysis was performed on the composite electrolyte layer included in the electrode structure of Example 1 using Image J software. From the SEM images taken of the cross-section of the composite electrolyte layer, the porosity was measured by calculating the pore area as a percentage of the composite electrolyte layer area.

[0211] Figure 9 is an SEM image of a cross-section of a composite electrolyte layer of an electrode structure according to Example 1.

[0212] In Fig. 9, the pores of the oxide-based electrolyte are indexed in red, and the measured porosity is 18%. Accordingly, it can be seen that the mixing volume ratio of the oxide-based electrolyte and the polymer electrolyte included in the composite electrolyte layer of Example 1 is 80:20.

[0213]

[0214] 3. Evaluation of the initial Martian process characteristics

[0215] To activate and impart electrical characteristics to the manufactured cells, a chemical reaction process (initial charge-discharge process) was performed. The chemical reaction process was performed by repeating charging (CC-CV 0.1C, 4.3 V cut-off) and discharging (CC 0.1C, 2.7 V cut-off) twice at room temperature based on the current density of the first electrode.

[0216] In the first charge / discharge cycle during the above Mars process, the charge curve is shown in Fig. 10a and the discharge curve is shown in Fig. 10b.

[0217] Referring to Fig. 10a, the charging curve in the lithium secondary battery cell according to Example 1 increased more stably than in the lithium secondary battery cell according to Comparative Example 1.

[0218] Referring to FIG. 10b, a discharge capacity close to the theoretical capacity (180 mAh / g) of the positive electrode was observed in the lithium secondary battery cell according to Example 1, and the discharge capacity was further reduced in the lithium secondary battery cell according to Comparative Example 1.

[0219]

[0220] 4. Life Characteristics Evaluation

[0221] A constant current charge-discharge evaluation was performed on the cells after the Mars process. Based on the current density of the first electrode, charge (CC-CV 0.5C, 4.3 V cut-off) and discharge (CC 0.5C, 2.7 V cut-off) were performed at room temperature as one cycle, and the discharge capacity and charge capacity were measured for each cycle.

[0222] The life characteristics were evaluated as a percentage of the discharge capacity measured in 100 cycles divided by the discharge capacity measured in 1 cycle.

[0223] The measurement results are shown in Figure 11 and Table 1 below.

[0224]

[0225] 5. Initial Efficiency Evaluation

[0226] For the cells that completed the Mars process, charging (CC-CV 0.5C, 4.3 V cut-off) and discharging (CC 0.5C, 2.7 V cut-off) were performed at room temperature. Afterwards, the same charging and discharging was performed 100 times at room temperature, and the initial efficiency was evaluated as the percentage of the first discharge capacity to the first charge capacity.

[0227] The measurement results are shown in Figure 12 and Table 1 below.

[0228] Initial discharge capacity (mAh / g) 100 cycle discharge capacity (mAh / g) Capacity retention rate (100 cycles, %) Initial coulombic efficiency (%) Example 1180.55 167.18 92.59 90.81 Comparative example 1149.24 139.60 93.54 24.43

[0229] Referring to Table 1 above, the lithium secondary battery cell according to Example 1 had higher discharge capacity and initial coulombic efficiency, and lower capacity retention rate than the lithium secondary battery cell according to Comparative Example 1.

[0230] In the composite electrolyte layer according to Example 1, the polymer electrolyte was inserted into the pores of the oxide-based electrolyte, thereby improving the electrode / electrolyte interface bonding and lithium ion conductivity, and improving the output characteristics and capacity characteristics of the lithium secondary battery cell.

[0231] In addition, charging and discharging were continuously performed on the lithium secondary battery cells according to Example 1 and Comparative Example 1, which were subjected to constant current application charge and discharge evaluation up to 100 cycles according to “4. Life Characteristics Evaluation.”

[0232] As a result, even when driven for 400 to 500 cycles, the discharge capacity of the lithium secondary battery cell according to Example 1 was higher than the discharge capacity of the lithium secondary battery cell according to Comparative Example 1.

Claims

1. Cathode; and A composite electrolyte layer formed on the cathode and including an oxide-based electrolyte and a polymer electrolyte, The above oxide electrolyte comprises a sintered body, An electrode structure for a secondary battery, wherein the volume of the oxide-based electrolyte included in the composite electrolyte layer is greater than the volume of the polymer electrolyte included in the composite electrolyte layer.

2. An electrode structure for a secondary battery, wherein the oxide electrolyte and the polymer electrolyte are included in a volume ratio of 55:45 to 90:10 in claim 1.

3. In claim 1, the oxide-based electrolyte is an LLZO-based compound, an LLTO-based compound, or Li6La2CaTa2O 12 , Li6La2ANb2O 12 (A is Ca or Sr), Li2Nd3TeSbO 12 , Li3BO 2.5 N 0.5 , Li9SiAlO8, LAGP compounds, LATP compounds, Li 1+x Ti 2-x Al x Si y (PO4) 3-y (0≤x≤1, 0≤y≤1), LiAl x Zr 2-x (PO4)3(0≤x≤1, 0≤y≤1), LiTi x Zr 2-x An electrode structure for a secondary battery, comprising at least one sintered body selected from the group consisting of (PO4)3(0≤x≤1, 0≤y≤1), LISICON-based compounds, LIPON-based compounds, perovskite-based compounds, and NASICON-based compounds.

4. In claim 1, the polymer electrolyte is a polymerized electrode structure for a secondary battery including a monomer containing a (meth)acrylate group.

5. In claim 1, the polymer electrolyte is a polymerized electrode structure for a secondary battery, comprising at least one monomer selected from the group consisting of trimethylolpropane triacrylate, di-trimethylolpropane tetraacrylate, trimethylolpropane ethoxylate triacrylate, butane diol diacrylate, tripropylene glycol diacrylate, and trimethylolpropane trimethacrylate.

6. An electrode structure for a secondary battery according to claim 1, wherein the porosity of the composite electrolyte layer is 10% to 50% by volume.

7. An electrode structure for a secondary battery according to claim 1, wherein the composite electrolyte layer does not contain carbon and contains at least one selected from the group consisting of phosphorus, sulfur, and fluorine.

8. An electrode structure for a secondary battery according to claim 1, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.

9. An electrode structure for a secondary battery according to claim 8, wherein the negative active material layer comprises at least one selected from the group consisting of a carbon-based active material and a silicon-based active material.

10. An electrode structure for a secondary battery according to claim 9, wherein the carbon-based active material comprises at least one selected from the group consisting of crystalline carbon and amorphous carbon.

11. In claim 9, the silicon-based active material is a carbon-silicon composite active material, silicon oxide (SiO x , 0 <x<2) 및 퓨어 실리콘으로 이루어진 군에서 선택되는 적어도 하나를 포함하는, 이차전지용 전극 구조체.

12. A step of applying an oxide-based electrolyte composition onto a cathode; A step of forming a preliminary composite electrolyte layer by sintering the applied oxide-based electrolyte composition; and A method for manufacturing an electrode structure for a secondary battery, comprising a step of forming a composite electrolyte layer by applying a polymer electrolyte composition on the preliminary composite electrolyte layer.

13. A method for manufacturing an electrode structure for a secondary battery, wherein the step of forming the preliminary composite electrolyte layer according to claim 12 comprises photo-sintering the applied oxide-based electrolyte composition at a temperature in the range of 400°C to 900°C.

14. A method for manufacturing an electrode structure for a secondary battery, wherein the step of forming the composite electrolyte layer according to claim 12 includes thermally curing the applied polymer electrolyte composition.

15. A method for manufacturing an electrode structure for a secondary battery, wherein the thermal curing of the polymer electrolyte composition according to claim 14 is performed at 50°C to 80°C.

16. A method for manufacturing an electrode structure for a secondary battery, wherein a part of the polymer electrolyte composition applied on the preliminary composite electrolyte layer is impregnated into the inside of the negative electrode according to claim 12.

17. A method for manufacturing an electrode structure for a secondary battery, wherein the oxide-based electrolyte composition according to claim 12 comprises an oxide-based electrolyte, a binder, and a sintering agent.

18. A method for manufacturing an electrode structure for a secondary battery, wherein the polymer electrolyte composition according to claim 12 comprises a polymer electrolyte, a lithium salt, and a thermal initiator.

19. A method for manufacturing an electrode structure for a secondary battery, further comprising the step of arranging an anode on the composite electrolyte layer according to claim 12.

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