Method for manufacturing negative electrode for secondary battery, negative electrode manufactured using same, and all-solid-state battery comprising same

Abstract

The present invention relates to a negative electrode for a secondary battery, the negative electrode comprising: a negative electrode current collector; and a negative electrode coating layer disposed on the negative electrode current collector, wherein the negative electrode coating layer includes a carbon material and metal nanoparticles dispersed in the carbon material. The metal nanoparticles each include a core containing silver and an organic layer disposed on the core, wherein the organic layer has a thickness of 2-5 nm from the surface of the metal nanoparticle toward the center of the metal nanoparticle.

Description

Method for manufacturing a negative electrode for a secondary battery, a negative electrode manufactured using the same, and an all-solid-state battery including the same

[0001] The present invention relates to a method for manufacturing a negative electrode for a secondary battery, a negative electrode manufactured using the same, and an all-solid-state battery including the same.

[0002]

[0003] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being used not only in information and communication devices, but also in the automotive sector. Safety is particularly important in the automotive sector, as it is directly related to life.

[0004] Recently, all-solid-state batteries, which replace the electrolyte with a solid electrolyte, have been proposed. By eliminating the use of flammable organic dispersion media, all-solid-state batteries significantly reduce the risk of fire or explosion in the event of a short circuit. Therefore, these all-solid-state batteries can significantly improve safety compared to lithium-ion batteries that use electrolytes.

[0005]

[0006] The problem to be solved by the present invention is to provide a negative electrode having high charge / discharge capacity and improved stability, and a method for manufacturing the same, by uniformly distributing metal nanoparticles in a carbon material.

[0007] Another problem to be solved by the present invention is to provide an all-solid-state battery using the above-mentioned negative electrode.

[0008]

[0009] According to one embodiment, a negative electrode for a secondary battery includes: a negative electrode current collector; and a negative electrode coating layer disposed on the negative electrode current collector, wherein the negative electrode coating layer may include a carbon material and metal nanoparticles dispersed within the carbon material. The metal nanoparticles may include a core including silver; and an organic layer on the core. The organic layer may have a thickness of 2 nm to 5 nm from a surface of the metal nanoparticle toward the center of the metal nanoparticle.

[0010] According to another embodiment, a method for manufacturing a negative electrode for a secondary battery may include: mixing a silver nitrate (AgNO3) aqueous solution, a phenol-based reducing agent, and a reduction catalyst to prepare a dispersion including metal nanoparticles; adding a nonionic polymer and a carbon material to the dispersion to prepare a first mixture; adding an acid to the first mixture to prepare a second mixture having an adjusted pH; filtering, drying, and heat-treating the second mixture to obtain metal nanoparticles dispersed in the carbon material; mixing the metal nanoparticles, a solvent, and a binder to prepare a slurry; and applying the slurry onto a negative electrode current collector to form a negative electrode coating layer. The metal nanoparticles may include a core including silver; and an organic layer on the core. The organic layer may have a thickness of 2 nm to 5 nm from a surface of the metal nanoparticle toward the center of the metal nanoparticle. The organic layer may be derived from the phenol-based reducing agent.

[0011] According to another embodiment, an all-solid-state battery may include a positive electrode layer; a negative electrode layer facing the positive electrode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer. The negative electrode layer may include a negative electrode current collector; and a negative electrode coating layer disposed on the negative electrode current collector, wherein the negative electrode coating layer may include a carbon material and metal nanoparticles dispersed in the carbon material. The metal nanoparticles may include a core including silver; and an organic layer on the core, wherein the organic layer may include an aromatic compound. The metal nanoparticles may have a thickness of 2 nm to 5 nm from a surface thereof toward a center thereof.

[0012]

[0013] According to one embodiment, a secondary battery negative electrode can uniformly distribute metal nanoparticles in a carbon material. As a result, an all-solid-state battery using the negative electrode can have improved lifespan characteristics and stability.

[0014] A method for manufacturing a negative electrode for a secondary battery according to an embodiment can manufacture a negative electrode having the above-described effects.

[0015]

[0016] Figure 1 is a plan view of an all-solid-state battery according to one embodiment of the present invention.

[0017] Figure 2 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0018] Figure 3 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention.

[0019] Figure 4 is for explaining a negative electrode for a secondary battery according to one embodiment of the present invention.

[0020] Figure 5 is for explaining metal nanoparticles according to one embodiment of the present invention.

[0021] Figure 6 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention.

[0022] Figure 7 is a cross-sectional view of an all-solid-state battery during charging according to another embodiment of the present invention.

[0023] Figure 8 is a flowchart for explaining a method for manufacturing a cathode according to one embodiment of the present invention.

[0024] Figures 9a to 9c are photographs confirming the structure and components of metal nanoparticles according to Example 1.

[0025] Figure 10a is an SEM photograph of Ag particles according to Comparative Example 1.

[0026] Figures 10b and 10c are SEM photographs of Ag-C composite particles according to Comparative Example 1.

[0027] Figures 11a and 11b are SEM photographs of metal nanoparticles according to Example 1.

[0028] Figures 11c and 11d are SEM photographs of a carbon material in which metal nanoparticles are dispersed according to Example 1.

[0029] Figure 12 is an SEM photograph of the cathode coating layer according to Comparative Example 1.

[0030] Figure 13 is an SEM photograph of a cathode coating layer according to Example 1.

[0031]

[0032] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications. However, the description of these embodiments is provided solely to ensure a complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention.

[0033] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, the thicknesses of the components are exaggerated for the sake of clarity. Parts designated by the same reference numerals throughout the specification represent the same components.

[0034] Embodiments described herein will be described with reference to cross-sectional and / or plan views, which are ideal illustrations of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical contents. Accordingly, the regions illustrated in the drawings have a schematic nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific shapes of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, and third are used to describe various components in various embodiments of the present specification, these components should not be limited by such terms. These terms are used only to distinguish one component from another. The embodiments described and illustrated herein also include complementary embodiments thereof.

[0035] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0036] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0037] Unless otherwise defined in this specification, the particle size may be the average particle size. In addition, the particle size may be the average particle size (D), which means the diameter of particles with a cumulative volume of 50% by volume in the particle size distribution. 50 ) means the average particle diameter (D 50 ) can be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope photograph or a scanning electron microscope photograph. Alternatively, a measuring device using dynamic light-scattering is used for measurement, and data analysis is performed to count the number of particles for each particle size range, and then the average particle diameter (D) is calculated from this. 50 ) value can be obtained. Or, it can be measured using the laser diffraction method. When measuring by the laser diffraction method, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of about 28 kHz at an output of 60 W, and then the average particle diameter (D) based on 50% of the particle size distribution in the measuring device is measured. 50 ) can be produced.

[0038] Fig. 1 is a plan view of an all-solid-state battery according to embodiments of the present invention. Fig. 2 is a cross-sectional view taken along line A-A' of Fig. 1.

[0039] Referring to FIGS. 1 and 2, the all-solid-state battery (10) according to the present invention may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, the present invention is not limited thereto, and the all-solid-state battery (10) may further include an additional functional layer, such as an adhesion enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0040] A positive electrode layer (100) according to one embodiment of the present invention may include a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on the positive electrode current collector (110). The positive electrode active material layer (120) may include a positive electrode active material, a solid electrolyte, a conductive material, and a binder.

[0041] The positive electrode current collector (110) can provide a reference surface on which the positive electrode active material layer (120) is arranged. The positive electrode current collector (110) can include a plate or foil including, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0042] Meanwhile, unlike that illustrated in FIG. 2, in one embodiment of the present invention, the positive electrode current collector (110) may be omitted. Although not illustrated, a carbon layer having a thickness of 0.1 μm to 4 μm may be additionally disposed between the positive electrode current collector (110) and the positive electrode active material layer (120) to increase the bonding strength between the positive electrode current collector (110) and the positive electrode active material layer (120).

[0043] The positive electrode active material of the positive electrode active material layer (120) may include a material that can reversibly absorb and desorb lithium ions. The positive electrode active material may include a plurality of particles. The positive electrode active material may include, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not necessarily limited thereto. The positive electrode active materials may be each alone or may be a mixture of two or more types.

[0044] Lithium transition metal oxides include, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-cMn b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Nor 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Nor b Co c Mn d GeO2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG b O2(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-fA compound represented by any one of Fe2(PO4)3(0≤f≤2), LiFePO4. In these compounds, the capital letter “A” is Ni, Co, Mn, or a combination thereof, the capital letter “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, the capital letter “D” is O, F, S, P, or a combination thereof, the capital letter “E” is Co, Mn, or a combination thereof, the capital letter “F” is F, S, P, or a combination thereof, the capital letter “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, the capital letter “Q” is Ti, Mo, Mn, or a combination thereof, the capital letter “I” is Cr, V, Fe, Sc, Y, or a combination thereof, and the capital letter “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0045] The cathode active material may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen atomic layers and metal atomic layers are alternately and regularly arranged in a direction, and thereby each atomic layer forms a two-dimensional plane. The "cubic rock salt structure" refers to the sodium chloride type (NaCl type) structure, which is a type of crystal structure, and specifically refers to a structure in which the face-centered cubic lattice (fcc) formed by each cation and anion is arranged with a displacement of half of the ridge of the unit lattice. Lithium transition metal oxides having this layered rock salt structure include, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0046] The above-described compound included in the positive electrode active material may be covered by a coating layer (not shown). The positive electrode active material may also be a mixture of the above-described compound and a compound to which a coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of the coating elements below. The compound forming the coating layer is amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material. The method for forming the coating layer includes, for example, spray coating, dipping, etc.

[0047] When the positive electrode active material includes nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the all-solid-state battery (10) can be increased, thereby reducing metal dissolution of the positive electrode active material in a charged state. As a result, the cycle characteristics of the all-solid-state battery (10) in a charged state are improved. Meanwhile, the "cycle characteristics" are characteristics indicating the degree to which the all-solid-state battery (10) is deteriorated by charge / discharge of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics may have a small degree of deterioration of the all-solid-state battery (10) due to charge / discharge, and an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration of the all-solid-state battery (10) due to charge / discharge.

[0048] The positive electrode active material may have a particle shape such as a sphere or an ellipsoid, for example. The particle size and content of the positive electrode active material are not particularly limited.

[0049] The solid electrolyte of the positive electrode active material layer (120) may have a particle shape. The solid electrolyte may be dispersed between the positive electrode active materials. The solid electrolyte may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers, capital letter “Z” represents Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, capital letter “M” is one of P, Si, Ge, B, Al, Ga In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include at least one selected from (0≤x≤2).

[0050] Sulfide-based solid electrolytes include, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-xPS 6-x I x It may be an argyrodite-type compound including at least one selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li3PS4Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0051] Alternatively, the sulfide-based solid electrolyte is Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, (0≤c≤2)), where X may be F, Br, Cl, or a combination thereof. M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof. Can be.

[0052] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery is reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0053] The solid electrolyte in the positive electrode active material layer (120) may have a smaller average particle diameter than the first and second solid electrolytes in the solid electrolyte layer (300) described later. For example, the average particle diameter of the solid electrolyte in the positive electrode active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle diameter of the solid electrolyte in the solid electrolyte layer (300). Meanwhile, the average particle diameter may be a median diameter measured using a laser particle size distribution meter.

[0054] The positive electrode active material layer (120) may include a conductive material. The conductive material may have conductivity without causing a chemical change in the all-solid-state battery (10), thereby increasing the conductivity of the positive electrode active material and the solid electrolyte. The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0055] The positive electrode active material layer (120) may further include a binder. The binder may bind the positive electrode active material, the solid electrolyte, and the conductive material within the positive electrode active material layer (120) to each other. The binder may include a material for improving the bonding strength between the positive electrode active material layer (120) and the positive electrode current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0056] Based on 100 parts by weight of the total of the positive electrode active material, the solid electrolyte, the conductive material, and the binder, the positive electrode active material layer (120) may include 85 parts by weight or more and 92 parts by weight or less of the positive electrode active material. Based on 100 parts by weight of the total of the positive electrode active material, the solid electrolyte, the conductive material, and the binder, the positive electrode active material layer (120) may include 0.5 parts by weight or more and 1.5 parts by weight or less of the binder.

[0057] Based on 100 parts by weight of the solid electrolyte, the positive electrode active material layer (120) may include 1 part by weight or more and 50 parts by weight or less of a conductive material. If the conductive material is included in the positive electrode active material layer (120) in an amount of less than 1 part by weight based on 100 parts by weight of the solid electrolyte, the proportion of the conductive material may decrease, thereby lowering the electrical conductivity of the positive electrode active material layer (120). If the conductive material is included in the positive electrode active material layer (120) in an amount of more than 50 parts by weight based on 100 parts by weight of the solid electrolyte, the proportion of the conductive material may be excessively high, so that a covering layer covering the surface of the solid electrolyte may not be properly formed.

[0058] The positive electrode active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material, solid electrolyte, conductive agent, and binder.

[0059] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is disposed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0060] The negative electrode current collector (210) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (210) may have, for example, a plate shape or a foil shape. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0061] The negative electrode coating layer (220) can allow lithium metal to grow between it and the negative electrode current collector (210) when the all-solid-state battery (10) is charged. The negative electrode coating layer (220) can act as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0062] The cathode coating layer (220) may include a metal and carbon. For example, the cathode coating layer (220) may include at least one metal selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The cathode coating layer (220) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene. In one embodiment, the cathode coating layer (220) may include a mixture of carbon black and silver (Ag).

[0063] The cathode coating layer (220) may further include additives other than metal and carbon. The cathode coating layer (220) may further include, for example, at least one additive selected from the group consisting of a binder, a filler, a coating agent, a dispersant, and an ion conductive additive.

[0064] The binder included in the above cathode coating layer (220) may include at least one of styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0065] The binder may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the cathode coating layer (220). For example, the binder may be included in an amount of 5 to 15 parts by weight based on 100 parts by weight of the cathode coating layer (220).

[0066] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0067] A solid electrolyte layer (300) may be provided between the positive electrode layer (100) and the negative electrode layer (200). The solid electrolyte layer (300) may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. The solid electrolyte in the solid electrolyte layer (300) may be the same as or different from any one of the materials included in the solid electrolyte in the positive electrode active material layer (120) described above.

[0068] The solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the positive electrode layer (100), and the second solid electrolyte layer (320) may be adjacent to the negative electrode layer (200).

[0069] Referring to FIG. 2, the first solid electrolyte layer (310) may include a first solid electrolyte. The first solid electrolyte may have a particle shape such as a sphere or an ellipsoid. The first solid electrolyte may include a sulfide-based solid electrolyte. The first solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may include, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material including Li2S-P2S5. When using a sulfide-based solid electrolyte material including Li2S-P2S5 to form the solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0070] In one embodiment, the first solid electrolyte is Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I xThe first solid electrolyte may include an argyrodite-type compound including at least one selected from (0≤x≤2). The first solid electrolyte may include an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0071] In another embodiment, the first solid electrolyte is Li 7-a M a PS 6-c X c Argyrodite-type compounds may include, wherein X may be Cl, Br, or a combination thereof. M may be Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, or a combination thereof. Each of a and c may be a real number between 0 and 2.

[0072] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. When the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery is reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the first solid electrolyte is, for example, 15 GPa to 35 GPa.

[0073] The first solid electrolyte layer (310) may further include a binder. The binder included in the solid electrolyte layer (300) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto. The binder of the first solid electrolyte layer (310) may be the same as or different from the binder included in the positive electrode active material layer (120) or the binder included in the negative electrode coating layer (220).

[0074] The second solid electrolyte layer (320) may include a second solid electrolyte. The second solid electrolyte may have a particle shape such as a sphere or ellipsoid.

[0075] The second solid electrolyte may include a sulfide-based solid electrolyte. The description of the second solid electrolyte may be the same as or similar to that described above for the first solid electrolyte. In one embodiment, the second solid electrolyte may have substantially the same composition as the first solid electrolyte. In another embodiment, the second solid electrolyte may have a similar composition to the first solid electrolyte.

[0076] The second solid electrolyte can be in direct contact with the negative electrode coating layer (220). As a result, the second solid electrolyte can suppress lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210). The second solid electrolyte can effectively suppress negative electrode side reactions. As a result, the cell performance of the all-solid-state battery (10) according to the present invention can be improved.

[0077] The first solid electrolyte layer (310) may have a first thickness (TK1), and the second solid electrolyte layer (320) may have a second thickness (TK2). The first thickness (TK1) and the second thickness (TK2) may be the same or different. In one embodiment, the first thickness (TK1) may be greater than the second thickness (TK2). For example, the first thickness (TK1) may be 1.1 to 5 times the second thickness (TK2).

[0078] Referring back to FIGS. 1 and 2, the positive electrode layer (100) and the first solid electrolyte layer (310) may form a positive electrode composite layer (CSH). The negative electrode layer (200) and the second solid electrolyte layer (320) may form a negative electrode composite layer (ASH). The positive electrode composite layer (CSH) may be laminated on the negative electrode composite layer (ASH).

[0079] The area of ​​the cathode composite layer (ASH) and the area of ​​the cathode composite layer (CSH) may be different. Specifically, the area of ​​the cathode composite layer (ASH) may be larger than that of the cathode composite layer (CSH). The cathode composite layer (CSH) may be completely overlapped within the cathode composite layer (ASH).

[0080] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the positive electrode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the negative electrode layer (200).

[0081] Specifically, the positive electrode composite layer (CSH) may have a first width (WI1) in a first direction (D1). The negative electrode composite layer (ASH) may have a second width (WI2) in the first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The positive electrode composite layer (CSH) may have a third width (WI3) in the second direction (D2). The negative electrode composite layer (ASH) may have a fourth width (WI4) in the second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0082] The all-solid-state battery (10) according to the present embodiment can be manufactured by forming a negative electrode composite layer (ASH) on a first carrier film, forming a positive electrode composite layer (CSH) on a second carrier film, and then laminating the negative electrode composite layer (ASH) and the positive electrode composite layer (CSH).

[0083] FIG. 3 is a cross-sectional view taken along line A-A' of FIG. 1, illustrating an all-solid-state battery according to another embodiment of the present invention. In the embodiments described below, detailed descriptions of technical features overlapping with those previously described with reference to FIGS. 1 and 2 will be omitted, and differences will be described in detail.

[0084] Referring to FIG. 3, the all-solid-state battery (10) according to the present invention may further include a gasket (GSK). The gasket (GSK) may be provided to surround the cathode composite layer (CSH). The gasket (GSK) may fill the step on the side of the all-solid-state battery (10) caused by the difference in area between the anode composite layer (ASH) and the cathode composite layer (CSH). The gasket (GSK) may surround the four side surfaces of the cathode composite layer (CSH). For example, the thickness of the gasket (GSK) may be substantially the same as the thickness of the cathode composite layer (CSH).

[0085] The upper surface of the second solid electrolyte layer (320) may include a first region in contact with the first solid electrolyte layer (310) and a second region in contact with the gasket (GSK). The second region may be a peripheral region of the upper surface of the second solid electrolyte layer (320). The second region may surround the first region.

[0086]

[0087] Cathode for secondary batteries

[0088] Hereinafter, a negative electrode for a secondary battery according to an embodiment will be described in detail with reference to FIGS. 4 and 5.

[0089] Fig. 4 is a cross-sectional view of a negative electrode for a secondary battery according to one embodiment of the present invention. Fig. 5 is a cross-sectional view of a metal nanoparticle according to one embodiment of the present invention.

[0090] Referring to FIGS. 4 and 5, a negative electrode for a secondary battery according to one embodiment may include a negative electrode layer (200). The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) disposed on the negative electrode current collector (210).

[0091] The cathode coating layer (220) may include metal nanoparticles (222) and carbon material (221). Specifically, the cathode coating layer (220) may include carbon material (221) and metal nanoparticles (222) dispersed within the carbon material (221).

[0092] The negative electrode current collector (210) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or compound with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0093] The negative electrode current collector (210) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (210) may have, for example, a plate shape or a foil shape. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0094] The BET specific surface area of ​​the above cathode coating layer (220) is 30 to 70 m 2 / g. For example, the BET specific surface area of ​​the cathode coating layer (220) may be 40 to 60 m 2 / g can be 45 to 50 m 2 / g may be.

[0095] The thickness of the cathode coating layer (220) may be, for example, 1 μm to 50 μm, 3 μm to 40 μm, 5 μm to 30 μm, or 5 μm to 20 μm. In one embodiment, the thickness of the cathode coating layer (220) may be 6 μm to 15 μm.

[0096] If the thickness of the negative electrode coating layer (220) is thinner than the range described above, lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210) may cause the negative electrode coating layer (220) to collapse, thereby deteriorating the cycle characteristics of the battery. On the other hand, if the thickness of the negative electrode coating layer (220) is thicker than the range described above, the energy density of the all-solid-state battery may decrease and the internal resistance of the all-solid-state battery due to the negative electrode coating layer (220) may increase, thereby deteriorating the cycle characteristics of the all-solid-state battery.

[0097] The above cathode coating layer (220) may further include a binder and a dispersant. The binder may be, for example, one or more selected from the group consisting of styrene butadiene rubber (SBR), polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0098] The dispersant is not particularly limited, but may be one or more selected from the group consisting of, for example, a soluble polyamine, a soluble amine compound, a fatty acid, a fatty alcohol, a cellulose ion exchanger, and a sorbitan fatty acid ester, as long as it improves the dispersibility of the carbon material and does not significantly reduce the adhesiveness. For example, carboxymethyl cellulose (CMC) can be used as the dispersant.

[0099] For example, the negative electrode coating layer (220) can be manufactured by coating a slurry containing metal nanoparticles, a binder, a dispersant, and a solvent dispersed in the carbon material described above on the negative electrode current collector (210). For example, the negative electrode coating layer (220) can be manufactured by bar coating a slurry containing a carbon material in which the metal nanoparticles described above are dispersed, a binder, and a solvent on the negative electrode current collector (210).

[0100] The carbon material (221) forms the body of the cathode coating layer (220). The carbon material (221) may include metal nanoparticles (222) therein. For example, the carbon material (221) may surround each metal nanoparticle (222).

[0101] The carbon material (221) can be in direct contact with the negative electrode current collector (210). The carbon material (221) can be in direct contact with the solid electrolyte layer (300).

[0102] The weight ratio of the metal nanoparticles (222) and the carbon material (221) may be 1:5 to 1:10. For example, the weight ratio of the metal nanoparticles (222) and the carbon material (221) may be 1:5 to 1:8. When the above range is satisfied, the formation of the cathode coating layer (220) in which the metal nanoparticles (222) are dispersed within the carbon material (221) may be facilitated.

[0103] The content of the metal nanoparticles (222) may be 10 wt% to 40 wt% with respect to the total weight of the cathode coating layer (220). For example, the content of the metal nanoparticles (222) may be 10 wt% to 35 wt%, 15 wt% to 30 wt%, or 15 wt% to 25 wt% with respect to the total weight of the cathode coating layer (220). In one embodiment, the content of the metal nanoparticles (222) may be 15 wt% to 25 wt%.

[0104] When the above range is satisfied, if the content of the metal nanoparticles (222) satisfies the above-described range, a negative electrode having excellent charge / discharge capacity and maintaining a structure can be provided.

[0105] The carbon material (221) may include amorphous carbon. The amorphous carbon may include a material selected from soft carbon, hard carbon, pitch carbide, mesophase pitch carbide, calcined coke, polymer carbide, and combinations thereof. The amorphous carbon may be formed by carbonizing a carbon precursor, such as coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, organic synthetic pitch, or a polymer resin such as a phenol resin, a furan resin, or a polyimide resin, through a heat treatment process. The heat treatment temperature during carbonization can be controlled within a range of 500°C.

[0106] The carbon material (221) may have a single particle form. The single particle may be in a form that is separated alone. Alternatively, the single particle may be in a form in which 2 to 100 single particles are attached to each other. The carbon material (221) may have an average particle diameter (D 50 ) may be in the form of aggregates of single particles of 40 nm to 50 nm. That is, the average particle diameter (D) of the carbon material (221) 50 ) may be 300 nm to 500 nm. For example, the particle size may refer to a diameter measured by randomly selecting about 30 carbon materials (221) from an electron microscope photograph of a cathode coating layer. When the above range is satisfied, the metal nanoparticles (222) can be uniformly distributed within the carbon material (221).

[0107] The amorphous carbon included in the carbon material (221) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, and ketjen black. Compared to crystalline carbon, the amorphous carbon has relatively low hardness and toughness and can effectively suppress the volume expansion of metal nanoparticles (222) dispersed within the carbon material (221), thereby improving the cycle life characteristics.

[0108] The BET surface area of ​​carbon material (221) is 50 to 70 m 2 / g. For example, the BET specific surface area of ​​the carbon material (221) is 55 to 60 m 2 / g. When the above range is satisfied, the carbon material (221) may have appropriate ionic conductivity, making it easy to transfer lithium ions to the surface or interior of the metal nanoparticles (222).

[0109] Referring to FIG. 5, the metal nanoparticle (222) may include a core (11) containing silver; and an organic layer (12) on the core (11).

[0110] Metal nanoparticles (222) have a structure in which a core (11) containing silver and an organic layer (12) is arranged on the surface of the core layer (11), thereby forming an alloy with lithium and allowing lithium to be uniformly deposited between the negative electrode coating layer and the negative electrode current collector.

[0111] The average particle diameter (D) of metal nanoparticles (222) 50) may be 10 nm to 50 nm. That is, the particle size of the metal nanoparticles (222) may be nano-sized. For example, the particle size may mean a diameter measured by randomly selecting about 30 porous metal nanoparticles (222) in an electron microscope photograph of a cathode coating layer. The particle size of the metal nanoparticles (222) may be uniform within the range described above. For example, the average particle diameter (D of the metal nanoparticles (222) 50 ) may be 20 nm to 30 nm. When the above range is satisfied, the metal nanoparticles (222) can be uniformly distributed within the carbon material (221).

[0112] The organic layer (12) may have a thickness (T1) from the surface of the metal nanoparticle (222) toward the center of the metal nanoparticle (222).

[0113] The above thickness (T1) refers to the distance from the surface of the metal nanoparticle (222) in the direction toward the center of the core (11). For example, when the distance from the surface of the metal nanoparticle (222) to the center of the metal nanoparticle (222) is referred to as the thickness (T1) of the organic layer, the organic layer (12) may have a thickness of 10 nm or less, 8 nm or less, 6 nm or less, or 5 nm or less. For example, the thickness (T1) of the organic layer (12) may be 2 nm to 5 nm or 2 nm to 3 nm. When the thickness is in the above range, the effect of improving battery performance due to the structural stabilization of the metal nanoparticle (222) is significant.

[0114] The organic layer (12) may contain carbon atoms. The content of the carbon atoms may be comprised between 0.1 at% and 3 at% of the total weight of the metal nanoparticles (222). When the content of the carbon atoms satisfies the above range, metal nanoparticles (222) having excellent capacity can be provided.

[0115] The above organic layer (12) may be derived from a phenol-based reducing agent used in the method for manufacturing a negative electrode for a secondary battery described below.

[0116]

[0117] All-solid-state batteries

[0118] Figure 6 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention.

[0119] Referring to FIG. 6, an all-solid-state battery (10) according to another embodiment may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). The negative electrode layer (200) may include a negative electrode current collector (210), and a negative electrode coating layer (220) disposed on the negative electrode current collector.

[0120] Detailed descriptions of technical features that overlap with those described with reference to FIGS. 1 to 5 above will be omitted, and differences will be described in detail. The all-solid-state battery (10) of FIG. 5 may have the same configuration as the negative electrode layer (200) described with reference to FIG. 4.

[0121] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) disposed on the negative electrode current collector (210). The negative electrode coating layer (220) may include metal nanoparticles (222) and carbon material (221). Specifically, the negative electrode coating layer (220) may include carbon material (221) and metal nanoparticles (222) dispersed within the carbon material (221).

[0122] The metal nanoparticle (222) may include a core containing silver; and an organic layer on the core. The organic layer may include an aromatic compound. The aromatic compound may be derived from a phenol-based reducing agent used in the method for manufacturing a negative electrode for a secondary battery described below.

[0123] Figure 7 is a cross-sectional view of an all-solid-state battery during charging according to another embodiment of the present invention.

[0124] Detailed descriptions of technical features that overlap with those described with reference to FIGS. 1 to 6 above will be omitted, and differences will be described in detail. The all-solid-state battery (10) of FIG. 7 may have the same configuration as the positive electrode layer (100), negative electrode layer (200), and solid electrolyte layer (300) described with reference to FIG. 6.

[0125] Referring to FIG. 7, the negative electrode layer (200) of the all-solid-state battery (10) may further include a lithium metal layer (230) between the negative electrode current collector (210) and the negative electrode coating layer (220).

[0126] The cathode coating layer (220) can allow lithium metal to grow between it and the cathode current collector (210) when the all-solid-state battery (10) is charged.

[0127] The lithium metal layer (230) may further increase in thickness when the all-solid-state battery (10) is charged. The negative electrode coating layer (220) serves as a protective layer for the lithium metal layer (230), and at the same time, can suppress the growth of lithium dendrites from the lithium metal layer (230).

[0128] The lithium metal layer (230) may be a metal thin film containing lithium or a lithium alloy. The lithium alloy may include, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy may be used. The lithium metal layer (230) may include one of these alloys or lithium. Alternatively, the lithium metal layer (230) may include various types of alloys.

[0129]

[0130] Method for manufacturing cathode

[0131] Figure 8 is a flowchart illustrating a method for manufacturing a cathode according to one embodiment of the present invention. Referring to Figure 8, the method for manufacturing a cathode according to one embodiment of the present invention will be described in more detail.

[0132] According to one embodiment of the present invention, a method for manufacturing a negative electrode may include: preparing a dispersion containing metal nanoparticles by mixing a silver nitrate (AgNO3) aqueous solution, a phenol-based reducing agent, and a reduction catalyst (S100); adding a nonionic polymer and a carbon material to the dispersion to prepare a first mixture (S200); adding an acid to the first mixture to prepare a second mixture having an adjusted pH (S300); filtering, drying, and heat-treating the second mixture to obtain metal nanoparticles dispersed in the carbon material (S400); mixing the metal nanoparticles, a solvent, and a binder to prepare a slurry (S500); and applying the slurry onto a negative electrode current collector to form a negative electrode coating layer (S600).

[0133] First, preparing a dispersion (S100) may include a process of mixing a silver nitrate (AgNO3) aqueous solution, a phenol-based reducing agent, and a reduction catalyst.

[0134] The above phenolic reducing agent may include a compound having an aromatic ring.

[0135] The above phenol-based reducing agent may include at least one selected from the group consisting of a phenol-based compound, a benzenediol-based (dihydroxybenzene) compound, a benzenetriol-based (trihydroxybenzene) compound, and a benzoic acid-based compound.

[0136] The above phenol compound may be a compound such as maltol or curcumin. The above benzenediol compound may be a compound with or without a substituent such as phenol, catechol, resorcinol, or hydroquinone. The above benzenetriol compound may be a compound with or without a substituent such as pyrogallol, hydroxyquinol, or phloroglucinol. The above benzoic acid compound may be a compound with a carboxylic substituent such as gallic acid or tannic acid.

[0137] In one embodiment, the phenolic reducing agent may be phloroglucinol.

[0138] The above reduction catalyst may use an amine catalyst. For example, the amine catalyst may include at least one selected from the group consisting of 2-aminoethanol, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 3-aminopropanol, 3-(methylamino)propanol, 4-aminobutanol, 4-(methylamino)butanol, bis(2-hydroxyethyl)amine, tris(2-hydroxyethyl)amine, ethylenediamine, and diethylenetriamine.

[0139] The above mixing may include a process of adding a phenol-based reducing agent and a reduction catalyst to a silver nitrate (AgNO3) aqueous solution and then stirring.

[0140] In one embodiment, the mixing may be performed by stirring at 20°C to 40°C for 20 minutes to 3 hours. The mixing may be performed using a mixing method commonly known in the art, for example, using a stirrer, a high-shear mixer, etc.

[0141] The dispersion prepared through the above mixing process may include metal nanoparticles. The average particle diameter (D) of the metal nanoparticles included in the dispersion 50 ) can be 20 nm to 30 nm.

[0142] In the above step S100, 0.1 to 2 parts by weight of the phenol-based reducing agent may be added to 100 parts by weight of the silver nitrate (AgNO3) aqueous solution, and then stirring may be performed. In the above step S100, 0.1 to 2 parts by weight of the reduction catalyst may be added to 100 parts by weight of the silver nitrate (AgNO3) aqueous solution, and then stirring may be performed.

[0143] The process of preparing the first mixture (S200) may include a process of mixing a nonionic polymer and a carbon material into the dispersion. The mixing may be performed using a mixing method commonly known in the art, such as a stirrer or high-shear mixer.

[0144] Carbon materials may be in the form of single particles. The single particles may be in the form of individual particles. Alternatively, the single particles may be in the form of two to one hundred single particles attached to each other. Carbon materials may have an average particle diameter (D 50 ) may be in the form of aggregates of single particles of 40 nm to 50 nm. That is, the average particle diameter (D) of the carbon material 50 ) can be 300 nm to 500 nm.

[0145] The above carbon material may include at least one selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene.

[0146] The above reduction catalyst may use an amine catalyst. For example, the amine catalyst may include at least one selected from the group consisting of 2-aminoethanol, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 3-aminopropanol, 3-(methylamino)propanol, 4-aminobutanol, 4-(methylamino)butanol, bis(2-hydroxyethyl)amine, tris(2-hydroxyethyl)amine, ethylenediamine, and diethylenetriamine.

[0147] In the above S200 step, the carbon material may be added in an amount of 5 to 20 parts by weight per 100 parts by weight of the dispersion, and then stirring may be performed.

[0148] In the above S200 step, in order to improve the dispersibility of the carbon material, a nonionic polymer may be dissolved in the first mixed solution and then the carbon material may be added.

[0149] The above nonionic polymer is polyvinylpyrrolidone (PVP), alkyl polyglycoside, cetostearyl alcohol, cetyl alcohol, cocamide DEA, cocamide MEA, decyl glucoside, decyl polyglucose, glycerol monostearate, IGEPAL CA-630, isoceteth-20, lauryl glucoside, maltoside, monolaurin, mycosubtilin, narrow-range ethoxylate, octylphenoxypolyethoxyethanol. Nonidet P-40, Nonoxynol-9, Nonoxynols, Nonyl phenoxypolyethoxyethanol (NP-40), Octaethylene glycol monododecyl ether, N-Octyl β-thioglucopyranoside, Octyl glucoside, Oleyl alcohol, Pentaethylene glycol monododecyl ether, Polidocanol, Poloxamer, Poloxamer 407, Polyethoxylated tallow amine, Polyethylene glycol cetyl ether, Polyglycerol Polyglycerol polyricinoleate, polysorbate,It may include at least one selected from the group consisting of polysorbate 20, polysorbate 80, sorbitan, sorbitan monolaurate, sorbitan monostearate, sorbitan tristearate, stearyl alcohol, surfactin, Triton X-100, and polysorbate 80 (Tween 80).

[0150] In one embodiment, the nonionic polymer may be polyvinylpyrrolidone (PVP).

[0151] Preparing the second mixed solution (S300) may include a process of adjusting the pH of the first mixed solution.

[0152] In the above S300 step, metal nanoparticles can be evenly adsorbed into the carbon material by controlling the pH.

[0153] The pH can be adjusted to a pH of 1 to 3 by adding acid to the first mixed solution. For example, the pH can be adjusted to a pH of 1.5 to 2.

[0154] The acid may include at least one selected from the group consisting of nitric acid, hydrochloric acid, acetic acid, formic acid, succinic acid, citric acid, malic acid, maleic acid, oxalic acid and mixtures thereof.

[0155] Obtaining metal nanoparticles dispersed in the above carbon material (S400) may include a process of separating the second mixed solution into a liquid and a solid.

[0156] In the above step S400, the second mixed solution can be filtered to separate the solid from the solvent.

[0157] The solid separated from the solvent can be dried through heat treatment. The drying can be performed at a temperature of 40°C to 60°C. The drying time can range from 2 to 24 hours, but is not limited thereto.

[0158] The dried product can be subjected to a firing process to remove impurities. The firing can be performed at temperatures ranging from 500°C to 1000°C. The firing time can range from 1 hour to 5 hours. In one embodiment, the firing equipment can be a variety of furnaces. For example, it can be a box-type furnace, or, considering productivity, a rotary kiln capable of continuous processing.

[0159] The calcined result can be subjected to a crushing and classification process to obtain metal nanoparticles dispersed in carbon material. The classification process can obtain an average particle diameter (D) of 10 nm to 50 nm in the calcined result. 50 ) can be selected to obtain a final metal nanoparticle powder.

[0160] For example, the above classification process may use dry classification or sieve classification.

[0161] The process of preparing a slurry (S500) may include a process of mixing the obtained metal nanoparticles, a solvent, a dispersant, and a binder. The binder and dispersant refer to the cathode portion described above.

[0162] Forming a cathode coating layer (S600) may include a process of applying the slurry onto a cathode current collector. The cathode current collector refers to the cathode portion described above.

[0163] For example, the negative electrode coating layer can be manufactured by bar coating a slurry containing a carbon material with metal nanoparticles dispersed therein, a binder, and a solvent on the negative electrode current collector (210).

[0164] The slurry formed on the negative electrode current collector can be dried through a heat treatment process. In one embodiment, the negative electrode having a negative electrode coating layer formed thereon can be manufactured by drying the slurry-coated negative electrode current collector in a vacuum oven.

[0165] The thickness of the cathode coating layer may be, for example, 1 μm to 50 μm, 3 μm to 40 μm, 5 μm to 30 μm, or 5 μm to 20 μm. In one embodiment, the thickness of the cathode coating layer (220) may be 6 μm to 15 μm.

[0166] In the cathode manufactured by the above-described method, the cathode coating layer may include a carbon material and metal nanoparticles dispersed within the carbon material. The metal nanoparticles may include a core including silver; and an organic layer on the core. The organic layer may have a structure having a thickness of 2 nm to 5 nm from the surface of the metal nanoparticles toward the center of the metal nanoparticles.

[0167] The above method for manufacturing the negative electrode can form an organic layer having a fine nano-thickness on metal nanoparticles. An all-solid-state battery including the negative electrode manufactured by this method can provide improved cycle characteristics.

[0168] Specifically, the organic layer may be formed by mixing silver nitrate (AgNO3), a phenol-based reducing agent, and an amine-based catalyst and heat-treating the mixture. Accordingly, the organic layer may include an aromatic compound derived from the phenol-based reducing agent.

[0169] The organic layer can easily form a connection structure between the metal nanoparticles and the carbon material by directly contacting the carbon material, thereby enabling a more uniform and stable formation of a conductive network between the metal nanoparticles and the carbon material present in the cathode coating layer.

[0170] Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0171]

[0172] Example 1

[0173] (1) Manufacturing of carbon powder

[0174] 0.6 g of phloroglucinol and 0.4 g of an amine catalyst were added to 100 ml of an aqueous solution containing 2 g of silver nitrate (AgNO3), and the mixture was stirred to prepare a colloidal dispersion containing silver nanoparticles at room temperature. After dissolving a nonionic polymer (polyvinylpyrrolidone) in the dispersion, 10.0 g of carbon material was added to 100 g of the dispersion to prepare a first mixture.

[0175] A second mixture with adjusted pH was prepared by adding nitric acid until the pH of the first mixture became about pH 1.5 to pH 2.

[0176] The second mixture was filtered to separate the liquid and solid, and the separated solid was dried at 60°C for 10 hours. Thereafter, the dried resultant was calcined at 400°C for 5 hours to remove impurities.

[0177] The resultant product, from which impurities were removed, was pulverized and classified to obtain carbon powder with metal nanoparticles dispersed therein.

[0178]

[0179] (2) Manufacturing of solid electrolyte layer

[0180] A mixture was prepared by adding argyrodite-type solid electrolyte Li6PS5Cl to an isobutylyl isobutylate binder solution containing butyl acrylate polymer (the mixing ratio of the solid electrolyte and the binder was 98.7:1.3 by weight, and the viscosity value of the mixture at 25℃ was 2700cP). After placing a polyester nonwoven fabric (porosity: 70%, thickness: 10㎛) on a polytetrafluoroethylene film, the mixture having a viscosity of 2700cP was applied to the nonwoven fabric, followed by vacuum drying at 80℃ for 2 hours, and removing the polytetrafluoroethylene film. Through this process, a solid electrolyte layer was prepared in which the nonwoven fabric was positioned at a distance of 2㎛ from the interface where it contacts the positive electrode and had a total thickness of 30㎛.

[0181]

[0182] (3) Manufacturing of cathode

[0183] The carbon material powder in which the metal nanoparticles were dispersed, styrene butadiene rubber (SBR) binder, and carboxymethyl cellulose (CMC) dispersant were mixed in a mass ratio of 9:0.5:0.5, and then dispersed in water and mixed to prepare a cathode coating layer slurry.

[0184] After coating the above slurry on a stainless steel foil current collector and drying it, a negative electrode including a 12 μm thick negative electrode coating layer and a 10 μm thick current collector was manufactured.

[0185]

[0186] (4) Manufacturing of anode

[0187] LiNi 0.8 Co 0.15 Mn 0.05A positive electrode composition was prepared by mixing 85 wt% of an O2 positive electrode active material, 13.5 wt% of a lithium argyrodite-type solid electrolyte Li6PS5Cl, 1.0 wt% of a polyvinylidene fluoride binder, and 0.5 wt% of a carbon nanotube conductive material in an N-methyl pyrrolidone solvent. The positive electrode composition was coated on an aluminum positive electrode current collector, dried, and rolled to prepare a positive electrode. The prepared positive electrode included a 12 μm thick positive electrode active material layer and a 10 μm thick current collector.

[0188]

[0189] (5) Manufacturing of all-solid-state full cells

[0190] The manufactured negative electrode, solid electrolyte layer, and positive electrode were sequentially laminated, and a pressure of 8 MPa was applied to manufacture an all-solid-state battery (full cell).

[0191]

[0192] Example 2

[0193] A full cell was manufactured in the same manner as Example 1, except that 5.0 g of carbon material was used when preparing the first mixture, and a charge / discharge test was performed.

[0194]

[0195] Example 3

[0196] A full cell was manufactured in the same manner as Example 1, except that 20.0 g of carbon material was used when preparing the first mixture, and a charge / discharge test was performed.

[0197]

[0198] Comparative Example 1

[0199] A full cell was manufactured and subjected to a charge / discharge test in the same manner as in Example 1, except that the cathode coating layer slurry was manufactured using conventional Ag-C composite particles.

[0200] Specifically, 10.0 g of carbon material was added to 100 ml of an aqueous solution containing a polymer (polyvinylpyrrolidone), and stirred to prepare a first mixture. 2 g of silver nitrate (AgNO3) and 3 g of ascorbic acid were sequentially added to the first mixture to prepare a second mixture.

[0201] The second mixture was filtered to separate the liquid and solid, and the separated solid was dried at 60°C for 10 hours. Thereafter, the dried resultant was calcined at 700°C for 5 hours to remove impurities.

[0202] The resultant product from which impurities were removed was pulverized and classified to obtain carbon material powder (Ag-C composite particles) with metal nanoparticles dispersed therein.

[0203]

[0204] Comparative Example 2

[0205] A full cell was manufactured in the same manner as Example 1, except that 1.0 g of carbon material was used when preparing the first mixture, and a charge / discharge test was performed.

[0206]

[0207] Comparative Example 3

[0208] A full cell was manufactured in the same manner as Example 1, except that 30.0 g of carbon material was used when preparing the first mixture, and a charge / discharge test was performed.

[0209]

[0210] Evaluation Example 1: Structural and Elemental Analysis of Metal Nanoparticles (SEM-EDS)

[0211] After photographing the metal nanoparticles manufactured in Example 1 and Comparative Example 1 using a scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) was performed.

[0212] Figures 9a and 9b are EDS images of metal nanoparticles according to Example 1. Figure 9c is the result of gas chromatography analysis of metal nanoparticles according to Example 1.

[0213] Referring to FIGS. 9a and 9b, it was confirmed that the obtained metal nanoparticles had a core containing silver and a carbon organic layer on the surface of the core.

[0214] Additionally, it was confirmed that the organic layer contained carbon atoms, and the content of the carbon atoms was 0.5 at% to 1 at% of the total weight of the metal nanoparticles.

[0215] Referring to FIGS. 9a to 9c, it was found that the organic layer exists with a thickness of 2 nm to 4 nm from the surface of the metal nanoparticle toward the center of the metal nanoparticle.

[0216] Fig. 10a is an SEM photograph of Ag particles according to Comparative Example 1. Fig. 10b is an SEM photograph of Ag-C composite particles according to Comparative Example 1. Fig. 10c is an enlarged view of Fig. 10b.

[0217] Referring to FIGS. 10A to 10C, the Ag particles according to Comparative Example 1 were confirmed to have a shape in which multiple particles were clumped together. It can be confirmed that the Ag particles exist in a particle size of 1 µm to 3 µm. In addition, it can be confirmed that the Ag-C composite particles according to Comparative Example 1 have metal (Ag) particles unevenly dispersed within the carbon material.

[0218] Fig. 11a is an SEM photograph of metal nanoparticles according to Example 1. Fig. 11b is an enlarged view of Fig. 11a. Fig. 11c is an SEM photograph of a carbon material having metal nanoparticles dispersed therein according to Example 1. Fig. 11d is an enlarged view of Fig. 11c.

[0219] Referring to FIGS. 11a to 11d, the metal nanoparticles according to Example 1 have an average particle diameter (D) of 10 nm to 50 nm.50 ) can be confirmed to exist as uniform particles. In addition, it can be confirmed that the metal nanoparticles according to Example 1 have metal (Ag) particles uniformly dispersed within the carbon material.

[0220]

[0221] Evaluation Example 2: Dispersion Characteristic Evaluation

[0222] The all-solid-state batteries manufactured according to Example 1 and Comparative Example were charged and discharged 10 times at 0.33 C. After completion of the charge and discharge, the batteries according to Example 1 and Comparative Example 1 were disassembled. The cross-sections of the negative electrode coating layers of the disassembled batteries were photographed using a scanning electron microscope (SEM) to confirm the dispersibility of the metal nanoparticles.

[0223] Fig. 12 is an SEM photograph of a cathode coating layer according to Comparative Example 1. Fig. 13 is an SEM photograph of a cathode coating layer according to Example 1.

[0224] Referring to part A of Fig. 12, it can be confirmed that pores are formed on the surface of the cathode coating layer due to the agglomeration of metal (Ag) particles. In addition, referring to part B of Fig. 12, it can be confirmed that the metal (Ag) particles are unevenly distributed within the carbon material, as the metal (Ag) particles are densely packed in one area.

[0225] On the other hand, referring to Figure 13, it can be confirmed that metal (Ag) particles are uniformly dispersed within the carbon material within the cathode coating layer.

[0226]

[0227] Evaluation Example 3: Evaluation of All-Solid-State Battery Life Characteristics

[0228] All-solid-state batteries manufactured according to the examples and comparative examples were subjected to 100 charge-discharge cycles at 0.33 C, and the life efficiency after 100 charge-discharge cycles was measured. The results are shown in Table 1 below.

[0229] In Table 1, the life efficiency is expressed by the following mathematical formula 1.

[0230] <Mathematical Formula 1>

[0231] Life efficiency [%] = [100 discharge capacity / initial discharge capacity] × 100

[0232] Life Efficiency (%) Example 197.5 Example 292.5 Example 394.5 Comparative Example 181.5 Comparative Example 284.9 Comparative Example 388.9

[0233]

[0234] Referring to Table 1, it was found that the all-solid-state battery according to the example had significantly improved life characteristics compared to the comparative example.

[0235] The present invention uses a carbon material having metal nanoparticles dispersed therein, including an organic layer on the outermost surface, as a negative electrode coating layer, so that when charging, the metal nanoparticles form an alloy with lithium, thereby uniformly depositing lithium between the negative electrode coating layer and the negative electrode current collector.

[0236] The present invention can improve the structural stability of a cathode layer by homogeneously distributing metal nanoparticles of uniform size within a carbon material.

[0237]

[0238] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. Cathode current collector; and A cathode coating layer disposed on the above-mentioned cathode current collector, comprising: The above cathode coating layer comprises a carbon material and metal nanoparticles dispersed within the carbon material, and The above metal nanoparticles are: A core containing silver; and It includes an organic layer on the above core, and The organic layer has a thickness of 2 nm to 5 nm from the surface of the metal nanoparticle toward the center of the metal nanoparticle, Negative electrode for secondary batteries.

2. In paragraph 1, The above organic layer contains carbon atoms, The content of carbon atoms in the metal nanoparticles is 0.1 at% to 3 at%, Negative electrode for secondary batteries.

3. In paragraph 1, Average particle size (D of the above metal nanoparticles) 50 ) is 10 nm to 50 nm, and The average particle diameter (D) of the above carbon material 50 ) is 300 nm to 500 nm, Negative electrode for secondary batteries.

4. In paragraph 1, The above carbon material comprises at least one selected from the group consisting of carbon black, acetylene black, furnace black, Kettjen black, and graphene. Negative electrode for secondary batteries.

5. In paragraph 1, The cathode coating layer has a weight ratio of the metal nanoparticles to the carbon material of 1:5 to 1:10, Negative electrode for secondary batteries.

6. In Paragraph 1, The above cathode coating layer further comprises a binder and a dispersant, Negative electrode for secondary batteries.

7. Preparing a dispersion containing metal nanoparticles by mixing an aqueous silver nitrate (AgNO3) solution, a phenolic reducing agent, and a reduction catalyst; Preparing a first mixture by adding a nonionic polymer and a carbon material to the above dispersion; Preparing a second mixture with adjusted pH by adding acid to the first mixture; Filtering, drying, and heat-treating the second mixture to obtain metal nanoparticles dispersed within the carbon material; Preparing a slurry by mixing the above metal nanoparticles, solvent, and binder; and The method includes applying the slurry onto a cathode current collector to form a cathode coating layer, wherein The above metal nanoparticles are: A core containing silver; and It includes an organic layer on the above core, and The organic layer has a thickness of 2 nm to 5 nm from the surface of the metal nanoparticle toward the center of the metal nanoparticle, Method for manufacturing a negative electrode for a secondary battery.

8. In paragraph 7, The above organic layer is derived from the above phenolic reducing agent, Method for manufacturing a negative electrode for a secondary battery.

9. In Paragraph 7, The above phenolic reducing agent comprises at least one selected from the group consisting of phenolic compounds, benzenediol (dihydroxybenzene) compounds, benzenetriol (trihydroxybenzene) compounds, and benzoic acid compounds. Method for manufacturing a negative electrode for a secondary battery.

10. In paragraph 7, Average particle size (D of the above metal nanoparticles) 50 ) is 10 nm to 50 nm, and The average particle diameter (D) of the above carbon material 50 ) is 300 nm to 500 nm, Method for manufacturing a negative electrode for a secondary battery.

11. In paragraph 7, The above reduction catalyst uses an amine-based catalyst, Method for manufacturing a negative electrode for an all-solid-state battery.

12. In Paragraph 7, The above nonionic polymer is polyvinylpyrrolidone (PVP), alkyl polyglycoside, cetostearyl alcohol, cetyl alcohol, cocamide DEA, cocamide MEA, decyl glucoside, decyl polyglucose, glycerol monostearate, IGEPAL CA-630, isoceteth-20, lauryl glucoside, maltoside, monolaurin, mycosubtilin, narrow-range ethoxylate, octylphenoxypolyethoxyethanol. Nonidet P-40, Nonoxynol-9, Nonoxynols, Nonyl phenoxypolyethoxyethanol (NP-40), Octaethylene glycol monododecyl ether, N-Octyl β-thioglucopyranoside, Octyl glucoside, Oleyl alcohol, Pentaethylene glycol monododecyl ether, Polidocanol, Poloxamer, Poloxamer 407, Polyethoxylated tallow amine, Polyethylene glycol cetyl ether, Polyglycerol Polyglycerol polyricinoleate, Polysorbate,Containing at least one selected from the group consisting of Polysorbate 20, Polysorbate 80, Sorbitan, Sorbitan Monolaurate, Sorbitan monostearate, Sorbitan tristearate, Stearyl alcohol, Surfactin, Triton X-100, and Tween 80. Method for manufacturing a negative electrode for a secondary battery.

13. In Paragraph 7, The above carbon material comprises at least one selected from the group consisting of carbon black, acetylene black, furnace black, Kettjen black, and graphene. Method for manufacturing a negative electrode for a secondary battery.

14. In Paragraph 7, Preparing the above-mentioned first mixture is, With respect to 100 parts by weight of the above dispersion, The above carbon material is added in an amount of 5 to 20 parts by weight, Method for manufacturing a negative electrode for a secondary battery.

15. In Paragraph 7, Preparing the above dispersion is, including stirring at 20℃ to 40℃ for 20 minutes to 3 hours, Method for manufacturing a negative electrode for a secondary battery.

16. In Paragraph 7, The above acid comprises at least one selected from the group consisting of nitric acid, hydrochloric acid, acetic acid, formic acid, succinic acid, citric acid, malic acid, maleic acid, oxalic acid, and mixtures thereof. Method for manufacturing a negative electrode for a secondary battery.

17. In Paragraph 7, Preparing the second mixture above involves adjusting the pH to 1 to 3. Method for manufacturing a negative electrode for a secondary battery.

18. In Paragraph 7, The above heat treatment includes calcining at 500°C to 1000°C for 1 to 5 hours. Method for manufacturing a negative electrode for a secondary battery.

19. Bipolar layer; A cathode layer facing the anode layer; and Including a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; The above cathode layer is: cathode current collector; and A cathode coating layer disposed on the above-mentioned cathode current collector, comprising: The cathode coating layer comprises carbon material and metal nanoparticles dispersed within the carbon material, The above metal nanoparticles are: A core containing silver; and It includes an organic layer on the above core, and The above organic layer comprises aromatic compounds, All-solid-state battery.

20. In Paragraph 19, Having a thickness of 2 nm to 5 nm from the surface of the metal nanoparticle toward the center of the metal nanoparticle, All-solid-state battery.

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