Negative electrode for all solid-state battery and all solid-state battery including same

Abstract

The present invention relates to a negative electrode for an all solid-state battery and an all solid-state battery including same, wherein the negative electrode for an all solid-state battery comprises a negative electrode coating layer that comprises a mixture of metal particles and a carbon-based material and that has a first peak appearing at a binding energy of 160eV-162eV and a second peak appearing at a binding energy of 163eV-165eV, in the S2p spectrum, when measured using X-ray photoelectron spectroscopy (XPS), the ratio of the second peak to the first peak being 3-12.

Description

Anode for an all-solid-state battery and an all-solid-state battery comprising the same

[0001] The present invention relates to a cathode for an all-solid-state battery and an all-solid-state battery including the same.

[0002] Recently, rapid developments have been made in electronic devices that use batteries, such as cell phones, laptop computers, and electric vehicles.

[0003] Lithium-ion secondary batteries are primarily used for these types of batteries, and currently commercialized lithium-ion secondary batteries use graphite, silicon, or a combination of these as their anode active materials. However, despite the growing demand for higher energy densities, lithium secondary batteries using graphite, silicon, or a combination of these as anode active materials cannot meet this demand. Furthermore, safety issues are emerging regarding lithium secondary batteries.

[0004] Accordingly, the development of all-solid-state batteries using lithium metal as the cathode is underway. All-solid-state batteries are composed entirely of solid materials, specifically those using solid electrolytes. Because lithium metal has a large potential difference with the anode, it boasts a high average voltage and a theoretical capacity of approximately 3,860 mAh / g, enabling high energy density. Furthermore, solid electrolytes offer improved safety due to their reduced risk of fire.

[0005] One embodiment provides an anode for an all-solid-state battery exhibiting excellent lithium ion conductivity and improved rate and cycle life characteristics.

[0006] Another embodiment provides an all-solid-state battery comprising the above negative electrode.

[0007] One embodiment provides an anode for an all-solid-state battery, comprising a cathode coating layer comprising a mixture of metal particles and a carbon-based material, having a first peak appearing at a binding energy of 160 eV to 162 eV and a second peak appearing at a binding energy of 163 eV to 165 eV in an S2p spectrum when measured by X-ray photoelectron spectroscopy (XPS), wherein the ratio of the second peak to the first peak is 3 to 12.

[0008] Another embodiment provides an all-solid-state battery comprising the cathode; the anode; and a solid electrolyte layer positioned between the cathode and the anode.

[0009] The above-mentioned all-solid-state battery may further include a lithium-containing layer formed between the current collector and the negative electrode coating layer during initial charging.

[0010] An anode for an all-solid-state battery according to one embodiment has a strong bonding force between metal and carbon, the metal is uniformly dispersed in a carbon-based material, and can exhibit improved rate characteristics, life characteristics, and excellent lithium ion conductivity.

[0011] Figure 1 is a schematic drawing of an all-solid-state battery negative electrode according to one embodiment.

[0012] Figure 2 is a cross-sectional view schematically showing an all-solid-state battery according to one embodiment.

[0013] Figure 3 is a cross-sectional view schematically showing an all-solid-state battery according to another embodiment.

[0014] Figure 4 is a TEM-EDS photograph of the cathode coating composition manufactured in Example 1.

[0015] FIG. 5 is a graph showing XPS S2p spectra for cathode coating compositions manufactured according to Example 1 and Comparative Example 1.

[0016] Figure 6 is a schematic diagram of a symmetrical cell for evaluating ionic conductivity.

[0017] Figure 7 is a graph showing the thermogravimetric analysis measured before and after heat treatment of the cathode catalyst of Example 1.

[0018] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0019] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0020] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0021] It should be understood that terms such as "include," "comprise," or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0022] Throughout this specification, when it is said that a part "includes" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0023] In addition, the terms "about", "substantially", etc. used throughout this specification are used in the sense of numerical values ​​or near numerical values ​​when manufacturing and material tolerances inherent to the meanings stated are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute values ​​to aid understanding of this specification.

[0024] Throughout this specification, the description of “A and / or B” means “A or B or both.”

[0025] Unless otherwise specified herein, when a part such as a layer, film, region, plate, etc. is said to be “on” another part, this includes not only cases where it is “directly on” the other part, but also cases where there is another part in between.

[0026] In the present invention, "particle size" or "particle diameter" may be an average particle diameter. In addition, the average particle diameter may be defined as the average particle diameter (D50) based on 50% of the cumulative volume in a particle diameter distribution curve. The particle diameter may be measured by a method 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, a scanning electron microscope, or a field emission scanning electron microscope (FE-SEM). Alternatively, the average particle diameter (D50) may be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from this. Alternatively, the average particle diameter (D50) may be measured using a laser diffraction method. When measuring by laser diffraction, 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 approximately 28 kHz at an output of 60 W, and the average particle diameter (D50) based on 50% of the particle diameter distribution in the measuring device can be calculated.

[0027] "Thickness" may be measured, for example, from photographs taken with an optical microscope such as a scanning electron microscope.

[0028] One embodiment relates to an anode for an all-solid-state battery including a cathode coating layer. In one embodiment, the anode coating layer for an all-solid-state battery refers to a material that helps lithium ions released from a cathode active material during charge / discharge of an all-solid-state battery to move toward the cathode and be deposited on the surface of a current collector. The anode of an all-solid-state battery including such a cathode coating layer forms a lithium deposition layer due to the deposition of lithium ions between the current collector and the cathode coating layer, and this lithium deposition layer functions as an anode active material. Such a cathode is generally referred to as a deposition-type anode.

[0029] The cathode coating layer has a first peak appearing at a binding energy of 160 eV to 162 eV and a second peak appearing at a binding energy of 163 eV to 165 eV in an S2p spectrum when measured by X-ray photoelectron spectroscopy (XPS), and a ratio of the second peak to the first peak is 3 to 12, and includes a mixture of metal particles and a carbon-based material.

[0030] In one embodiment, the ratio of the second peak to the first peak may be 3 to 10, or may be 5 to 10.

[0031] In one embodiment, the ratio of the peaks may be a ratio of the heights of the peaks.

[0032] The first peak above may be a peak corresponding to Ag2S, and the second peak may be a peak corresponding to thiol.

[0033] The presence of these first and second peaks in the cathode coating layer indicates that sulfur is present in the cathode coating layer. Furthermore, this indicates that bonds between C and S (CS) and bonds between S and Ag (S-Ag) exist in the cathode coating layer.

[0034] In one embodiment, the ratio of the second peak to the first peak being within the above range means that the height of the second peak is higher than the height of the first peak, which means that bonds between C and S are present in greater numbers than bonds between S and Ag.

[0035] If the ratio of the second peak to the first peak is greater than the above range, it indicates that the metal, for example, Ag, and sulfur bonding are small, which means that the metals are in an aggregated state or that the metals are not chemically bonded with the carbon black, and the metal content may be reduced due to desorption during a post-process. If it is less than the above range, it means that the thiol compound used in the manufacturing process is almost removed, so that no sulfur remains on the carbon surface, which may mean that the carbon black surface not coated with sulfur reduces the affinity with the solid electrolyte in the electrode plate, thereby increasing the resistance.

[0036] The carbonaceous material may be amorphous carbon, crystalline carbon, or a mixture thereof. The amorphous carbon may be, for example, carbon black, acetylene black, Denka black, Ketjen black, furnace black, activated carbon, or a combination thereof. An example of the carbon black may be Super P (Timcal). The crystalline carbon may be natural graphite, artificial graphite, carbon nanotubes, graphene, or a combination thereof. The crystalline carbon may be in the form of amorphous, plate-like, flake-like, spherical, or fiber-like particles.

[0037] In one embodiment, the carbonaceous material may be a single particle, or may be an assembly having a secondary particle form in which primary particles are assembled. When the carbonaceous material is a single particle, the size of the carbonaceous material may be a nano-size with an average particle diameter of 100 nm or less, for example, 10 nm to 100 nm.

[0038] Additionally, when the carbon-based material is an assembly, the particle size of the primary particles may be 20 nm to 100 nm, and the particle size of the secondary particles may be 1 μm to 20 μm.

[0039] In one embodiment, the particle size of the primary particles may be 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, or 90 nm or more, and may be 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less.

[0040] In one embodiment, the particle size of the secondary particles may be 1 µm or more, 3 µm or more, 5 µm or more, 7 µm or more, 10 µm or more, or 15 µm or more, and may be 20 µm or less, 15 µm or less, 10 µm or less, 7 µm or less, 5 µm or less, or 3 µm or less.

[0041] The shape of the primary particles may be spherical, elliptical, plate-shaped, or a combination thereof, and in one embodiment, the shape of the primary particles may be spherical, elliptical, or a combination thereof.

[0042] The above metal may be Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd or a combination thereof. As the cathode coating layer includes the above metal, the electrical conductivity of the cathode can be further improved.

[0043] The metal may be a nanoparticle, and the size of the metal nanoparticle may be, for example, an average size of 5 nm to 80 nm, but a nanometer size may be suitably used. By using the metal nanoparticle having such a nano size, the battery characteristics (e.g., life characteristics) of the all-solid-state battery can be improved. If the metal particle size increases to the micrometer level, the uniformity of the metal particles in the negative electrode coating layer decreases, so that the current density in a specific region increases and the cycle life characteristics may deteriorate, which is not suitable.

[0044] In one embodiment, the content of the metal particles may be 3 wt% to 30 wt%, 4 wt% to 25 wt%, 5 wt% to 20 wt%, or 5 wt% to 15 wt%, based on 100 wt% of the mixture of the metal particles and the carbonaceous material.

[0045] The carbonaceous material may be present in an amount of 70 wt% to 97 wt%, 75 wt% to 96 wt%, 80 wt% to 95 wt%, or 85 wt% to 95 wt%, based on 100 wt% of the mixture of the metal particles and the carbonaceous material.

[0046] According to one embodiment, a cathode coating layer includes a metal and a carbon-based material, and a sulfur-containing compound is coated on the surface of the carbon-based material, and since the sulfur is bonded to the metal, the bonding strength between the carbon-based material and the metal can be high. Accordingly, the phenomenon of metal particles agglomerating into large metal particles within the cathode coating layer can be prevented, and as a result, the rate characteristics and life characteristics can be improved.

[0047] The compound containing the sulfur may be a thiol compound, for example, mercapto acetic acid, 1-dodecanethiol, 6-mercapto-1-hexanol, 11-mercapto-1-undecanol, 2-naphthalenethiol, 1,4-benzenedimethanethiol, 4-mercaptobenzoic acid, 1,3-benzenedithiol, or a combination thereof.

[0048] For example, the carbon-based material is coated with a thiol compound, and thus the thiol compound is present in the cathode coating layer. The content of the thiol compound may be 3 wt% to 15 wt%, or 5 wt% to 10 wt%, based on 100 wt% of the total of the metal particles, the carbon-based material, and the thiol compound. When the content of the thiol compound is within the above range, the sulfur in the thiol may completely coat the surface of the carbon-based material, for example, carbon black, and thus, there may be an advantage of anchoring the metal particles, for example, Ag, when they are supported on the carbon-based material.

[0049] In one embodiment, a mixture of metal particles and a carbonaceous material and a thiol compound, for example, a mixture of a carbonaceous material coated with a thiol compound and metal particles, may be referred to as a catalyst.

[0050] In one embodiment, the negative electrode coating layer may further include a fine-grained solid electrolyte, for example, a solid electrolyte having an average particle size of 1 μm to 6 μm. Since the solid electrolyte included in the negative electrode coating layer is a fine-grained solid electrolyte with such a small size, the fine-grained solid electrolyte can be well filled in the pores that may be naturally formed in the negative electrode coating layer. Accordingly, lithium ion conductivity can be further improved, so that lithium ions released from the positive electrode active material and moved toward the negative electrode during charging can well move toward the current collector. In addition, the pores within the negative electrode coating layer can be minimized. Accordingly, the reaction between electrons and lithium ions can mainly occur near the current collector, so that lithium can be more effectively deposited on the current collector.

[0051] When the average particle size of the solid electrolyte is within the above range, it can better fill the pores of the negative electrode coating layer and exhibit more appropriate lithium ion conductivity and energy density.

[0052] In addition, the negative electrode coating layer according to one embodiment has a ratio of the second peak to the first peak of 3 to 12, which means that there are many CS bonds, so that when a solid electrolyte is used, the affinity with the solid electrolyte can be improved, and thus the effect of improving lithium ion conductivity due to the use of the solid electrolyte can be greatly obtained.

[0053] In one embodiment, the content of the solid electrolyte may be 5 wt% to 25 wt%, or 10 wt% to 15 wt%, based on 100 wt% of the total negative electrode coating layer.

[0054] The above solid electrolyte may be a sulfide-based solid electrolyte. According to one embodiment, the cathode coating layer contains a combination of metal and sulfur, and also contains a thiol compound. Therefore, using a sulfide-based solid electrolyte as the solid electrolyte included in the cathode coating layer allows for the manufacture of a cathode with higher ionic conductivity and in various forms, compared to an oxide-based solid electrolyte, a halide-based solid electrolyte, or a solid polymer electrolyte.

[0055] In one embodiment, the sulfide-based solid electrolyte is Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element, for example, I or Cl), 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 and n are integers greater than or equal to 0 and less than or equal to 12, respectively, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are integers greater than or equal to 0 and less than or equal to 12, respectively; M is one of P, Si, Ge, B, Al, Ga In), Li a M b P c S d A e (a, b, c, d and e are each integers greater than or equal to 0 and less than or equal to 12, M is Ge, Sn, Si or a combination thereof, and A is one of F, Cl, Br, or I). The sulfide-based solid electrolyte may be, for example, Li 7-x PS 6-x F x (0≤x≤2), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS6-x Br x (0≤x≤2) or Li 7-x PS 6-x I x (0≤x≤2) can be. Also, specifically, Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 It could be the back.

[0056] In one embodiment, the sulfide-based solid electrolyte may be an argyrodite-type sulfide-based solid electrolyte. The argyrodite-type sulfide-based solid electrolyte may be, for example, Li a M b P c S d A e (a, b, c, d and e are all 0 or more and 12 or less, M is Ge, Sn, Si or a combination thereof, and A is one of F, Cl, Br, or I), and specifically Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 It could be the back.

[0057] The sulfide-based solid electrolyte may be amorphous, crystalline, or a mixture thereof. For example, the sulfide-based solid electrolyte may be obtained by mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or 50:50 to 80:20. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be manufactured. The ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3. Mechanical milling or a solution method can be applied as a mixing method. Mechanical milling is a method in which starting materials are placed in a reactor and vigorously stirred with a ball mill, etc. to pulverize the starting materials and mix them. When the solution method is used, the starting materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. In addition, additional calcination can be performed after mixing. If additional calcination is performed, the crystals of the solid electrolyte can become more solid.

[0058] Of course, a commercially available solid electrolyte can be used as the sulfide-based solid electrolyte.

[0059] The above cathode coating layer may further include a binder. The binder may be an insoluble binder.

[0060] The above-described non-aqueous binder may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer comprising ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, polyacrylate, or a combination thereof.

[0061] The binder may be present in an amount of 1 to 15 wt% relative to 100 wt% of the total weight of the cathode coating layer, for example, the binder may be present in an amount of 1 wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 6 wt% or more, 7 wt% or more, 8 wt% or more, 9 wt% or more, 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, or 14 wt% or more, and 15 wt% or less, 14 wt% or less, 13 wt% or less, 12 wt% or less, 11 wt% or less, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less relative to 100 wt% of the total weight of the cathode coating layer.

[0062] When the above binder is included in the negative electrode coating layer of the all-solid-state battery in the above content range, the electrical resistance and adhesive strength can be improved, thereby improving the characteristics (battery capacity and output characteristics) of the all-solid-state battery.

[0063] The above-described cathode coating layer may further include additives such as fillers and dispersants. In addition, known materials generally used in all-solid-state batteries may be used as fillers, dispersants, etc. that can be included in the cathode coating layer.

[0064] The thickness of the cathode coating layer may be 1 µm to 20 µm. For example, the thickness of the cathode coating layer may be 1 µm or more, 3 µm or more, 5 µm or more, and 20 µm or less, 18 µm or less, 16 µm or less, 14 µm or less, or 12 µm or less.

[0065] The current collector may be, 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, and may be in the form of a foil or sheet. The thickness of the negative electrode current collector may be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0066] The current collector may be formed of the metal as a substrate and may further include a thin film formed on the substrate. The thin film may include an element capable of forming an alloy with lithium, and may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, or a combination thereof, but is not limited thereto, and any element capable of forming an alloy with lithium in the art may be used. When the current collector further includes a thin film, when the lithium-containing layer is formed by precipitation during charging, a more planarized lithium-containing layer may be formed, thereby further improving the cycle life of the all-solid-state battery.

[0067] The thickness of the above thin film may be 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. When the thin film thickness is within the above range, the cycle life characteristics can be further improved.

[0068] FIG. 1 schematically illustrates an all-solid-state battery negative electrode (400) according to one embodiment of the present invention, wherein a negative electrode coating layer (403) including a metal (5) and a carbon-based material (7) is positioned on a current collector (401), and a small-particle solid electrolyte (9) is filled within the negative electrode coating layer.

[0069] A cathode according to an embodiment can be manufactured by the following manufacturing process.

[0070] A carbon-based material is mixed with a thiol compound in a solvent.

[0071] The above carbon-based material may be amorphous carbon or crystalline carbon as described above.

[0072] The above thiol compound is as described above.

[0073] The solvent may be water, for example, distilled water, N-methyl pyrrolidone, or a combination thereof.

[0074] The mixing ratio of the carbon-based material and the thiol compound may be a weight ratio of 4:1 to 999:1, a weight ratio of 4:1 to 900:1, a weight ratio of 5:1 to 100:1, or a weight ratio of 5:1 to 20:1.

[0075] Next, the obtained mixture is subjected to a primary heat treatment, and the surface of the carbon material can be coated with a thiol compound according to this mixing and primary heat treatment process. The primary heat treatment process can be performed at 70°C to 110°C.

[0076] A metal is supported on the obtained primary heat-treated product to produce a supported product. The supporting process can be performed by adding a metal compound and a reducing agent to the mixture. This addition process can be performed in a solvent, and the solvent can be water, ethanol, glycerol, benzene, xylene, N-methyl pyrrolidone, or a combination thereof. In addition, the reducing agent can be NaBH4, ascorbic acid, trisodium citrate, ethylene glycol, or a combination thereof.

[0077] In the process of supporting the metal, the amount of the metal compound used can be adjusted so that the content of the metal to be reduced is 3 wt% to 40 wt%, 4 wt% to 25 wt%, 5 wt% to 20 wt%, or 5 wt% to 15 wt% based on 100 wt% of the total weight of the supported product. In addition, the reducing agent may be used in an amount appropriate for causing a reduction reaction of the metal compound, and there is no need for a special limitation. For example, the amount of the reducing agent used can be used so that the molar equivalent ratio with the metal compound, that is, the metal compound: molar equivalent ratio, is 1:2 to 1:4.

[0078] The metal compound may be a metal nitride, a metal sulfate, a metal perchlorate, or a combination thereof, and for example, when the metal is Ag, it may be AgNO3, Ag2SO4, AgClO4, or a combination thereof.

[0079] The obtained support product can be subjected to secondary heat treatment.

[0080] The above secondary heat treatment process can be carried out at a temperature that can remove the solvent, the thiol compound is not decomposed, and the thiol compound and the metal can be bonded. For example, it can be carried out at 100°C to 290°C, and can also be carried out at 150°C to 250°C, or 200°C to 230°C. If the above secondary heat treatment process is carried out at a temperature exceeding 290°C, the thiol compound is decomposed and removed, so no thiol compound remains in the final cathode coating layer, and thus the ratio of the second peak to the first peak is outside of 3 to 12, which is not suitable.

[0081] Additionally, the secondary heat treatment may be performed under a nitrogen atmosphere, an argon atmosphere, or a combination thereof. Additionally, the secondary heat treatment may be performed for 2 to 4 hours.

[0082] According to the above secondary heat treatment process, the sulfur and metal of the thiol compound are combined, but since the thiol compound is not completely decomposed, the thiol compound may remain in the final cathode coating layer.

[0083] Another embodiment provides an all-solid-state battery comprising the cathode and also comprising a cathode, and a solid electrolyte layer positioned between the cathode and the anode.

[0084] According to one embodiment, the negative electrode may further include a lithium-containing layer formed during initial charging after battery manufacturing, between the current collector and the negative electrode coating layer. The thickness of the lithium-containing layer may be 1 µm to 1000 µm, 1 µm to 500 µm, 1 µm to 200 µm, 1 µm to 150 µm, 1 µm to 100 µm, or 1 µm to 50 µm. When the thickness of the lithium-containing layer is within the above range, the lithium storage function may be appropriately performed, and there may be an advantage of further improving the lifespan.

[0085] The lithium-containing layer can be formed when lithium ions are released from the positive electrode active material during charging after the battery is manufactured, pass through the solid electrolyte, and move toward the negative electrode, resulting in lithium being precipitated and deposited on the negative electrode current collector.

[0086] The above charging process may be a chemical reaction process performed once to three times at 0.05C to 1C at about 25°C to 50°C. When lithium is precipitated and deposited to form a lithium-containing layer, the lithium contained in the lithium-containing layer is ionized and moves toward the positive electrode during discharge, so that the lithium can be used as an anode active material.

[0087] In one embodiment, since the lithium-containing layer is positioned between the current collector and the negative electrode coating layer, the negative electrode coating layer can serve as a protective layer for the lithium-containing layer, thereby inhibiting the precipitation and growth of lithium dendrites. This can suppress short-circuiting and capacity degradation of the all-solid-state battery, and consequently improve the cycle life of the all-solid-state battery.

[0088] The above solid electrolyte layer includes a solid electrolyte. The solid electrolyte may be an inorganic solid electrolyte such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a solid polymer electrolyte.

[0089] In one embodiment, the sulfide-based solid electrolyte is as described above.

[0090] The above oxide-based solid electrolyte is, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), Pb(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12(0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr, x is an integer from 1 to 10), or a mixture thereof.

[0091] The above solid polymer electrolytes include, for example, polyethylene oxide, poly(diallyldimethylammonium)trifluoromethanesulfonyl imide (poly(diallyldimethylammonium)TFSI), Cu3N, Li3N, LiPON, Li3PO4·Li2S·SiS2, Li2S·GeS2·Ga2S3, Li2O.11Al2O3, Na2O.11Al2O3, (Na,Li) 1+x Ti 2-x Al x (PO4)3(0.1≤x≤0.9), Li 1+x Hf 2-x Al x (PO4)3(0.1≤x≤0.9), Na3Zr2Si2PO 12 , Li3Zr2Si2PO 12 , Na5ZrP3O 12 , Na5TiP3O 12 , Na3Fe2P3O 12 , Na4NbP3O 12 , Na-Silicates, Li 0.3 La 0.5 TiO3, Na5MSi4O 12 (M is a rare earth element such as Nd, Gd, Dy), Li5ZrP3O 12 , Li5TiP3O 12 , Li3Fe2P3O 12 , Li4NbP3O 12 , Li 1+x (M,Al,Ga) x (Ge 1-y Ti y ) 2-x(PO4)3(x≤0.8, 0≤y≤1.0, M is Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), Li 1+x+y Q x Ti 2-x Si y P 3-y O 12 (0 <x≤0.4, 0<y≤0.6, Q 는 Al 또는Ga), Li6BaLa2Ta2O 12 , Li7La3Zr2O 12 , Li5La3Nb2O 12 , Li5La3M2O 12 (M is Nb, Ta) and Li 7+x A x La 3-x Zr2O 12 (0 <x<3, A는 Zn) 중에서 선택된 하나 이상을 포함할 수 있다.

[0092] The above halide-based solid electrolyte may include a Li element, an M element (M is a metal other than Li), and an X element (X is a halogen). As X, for example, F, Cl, Br, and I may be mentioned. In particular, in the halide-based solid electrolyte, at least one of Br and Cl is suitable as X. In addition, as the M, for example, a metal element such as Sc, Y, B, Al, Ga, or In may be mentioned.

[0093] The composition of the above halide-based solid electrolyte is not particularly limited, but Li 6-3a M a Br b Cl c(In the formula, M is a metal other than Li, and 0 <a<2, 0≤b≤6, 0≤c≤6, b+c=6)로 표현될 수 있다. 이때, 상기 a는 0.75 이상일 수 있고, 1 이상일 수 있고, a는, 1.5 이하일 수 있다. 상기 b는 1 이상일 수 있고, 2 이상일 수 있다. 또한, 상기 c는, 3 이상일 수 있고, 4 이상일 수도 있다. 상기 할라이드계 고체 전해질의 구체적인 예로는 Li3YBr6, Li3YCl6또는 Li3YBr2Cl4를 들 수 있다.

[0094] The above solid electrolyte is in the form of particles, and the average particle diameter (D50) may be 5.0 ㎛ or less, for example, 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.5 ㎛ to 1.0 ㎛.

[0095] The above solid electrolyte layer may further include a binder. At this time, the binder may be, but is not limited to, styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, and any binder used in the relevant technical field may be used. The acrylate polymer may be butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0096] The above solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the same on a base film, and drying the same. The solvent for the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. Since the solid electrolyte layer formation process is widely known in the art, a detailed description thereof will be omitted herein.

[0097] The above positive electrode includes a positive electrode current collector and a positive electrode active material layer positioned on one surface of the positive electrode current collector.

[0098] The above-mentioned positive electrode active material layer may include a positive electrode active material. The positive electrode active material may be a positive electrode active material capable of reversibly absorbing and releasing lithium ions. For example, the positive electrode active material may use at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof. Specific examples of the positive electrode active material include Li a A 1-b B 1 b D 1 2(0.90≤a≤1.8, 0≤b≤0.5); Li a E 1-b B 1 b O 2-c D 1 c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5); Li a E 2-b B 1 b O 4-c D 1 c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤05); Li a Ni 1-b-c Co b B 1 c D 1 α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Co b B 1 c O 2-α F 1 α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Co b B 1 c O 2-α F 1 2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li aNor 1-b-c Mn b B 1 c D 1 α (0.90 ≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); The a Nor 1-b-c Mn b B 1 c O 2-α F 1 α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); The a Nor 1-b-c Mn b B 1 c O 2-α F 1 2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); The a Nor b E c G d O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d ≤0.1); The a Nor b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); The a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); The a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); The a MnG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); The a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI 1 O2; LiNiVO4; The (3-f) J2(PO4)3(0≤f≤2); The(3-f) Fe2(PO4)3(0≤f≤2); or LiFePO4.

[0099] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; B 1 is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D 1 is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F 1 is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I 1 is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0100] According to one implementation example, LiNi is used as the positive electrode active material. x Co y Al z O2(NCA), LiNi x Co y Mn z O2(NCM)(but, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1) 등의 삼성분계 리튬 전이 금속 산화물을 들 수 있다.

[0101] Of course, it is also possible to use a compound having a coating layer on the surface of the compound, or it is also possible to use a mixture of the compound and a compound having a coating layer. The coating layer may include at least one coating element compound selected from the group consisting of an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds forming these coating layers may be 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 forming process may use any coating method as long as it can coat the compound with these elements in a method that does not adversely affect the properties of the positive electrode active material (for example, spray coating, dipping, etc.), and since this is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0102] In addition, as the above coating layer, any known coating layer of the positive electrode active material of an all-solid-state battery can be applied, and examples thereof include Li2O-ZrO2 (LZO).

[0103] Furthermore, when the cathode active material is a ternary compound containing nickel, cobalt, and manganese, or nickel, cobalt, and aluminum, the capacity density of the all-solid-state battery can be further improved and metal dissolution from the cathode active material can be further reduced in a charged state. Consequently, the all-solid-state battery can exhibit improved long-term reliability and cycle performance in a charged state.

[0104] Here, examples of the shape of the positive electrode active material include spherical, elliptical, and other particle shapes. Furthermore, the average particle diameter of the positive electrode active material is not particularly limited, and may be within the range applicable to positive electrode active materials for existing all-solid-state secondary batteries. Furthermore, the content of the positive electrode active material in the positive electrode active material layer is also not particularly limited, and may be within the range applicable to positive electrode layers for existing all-solid-state secondary batteries.

[0105] The positive electrode active material layer may additionally include a solid electrolyte. The solid electrolyte included in the positive electrode active material layer may be the same as or different from the solid electrolyte included in the solid electrolyte layer. The solid electrolyte may be included in an amount of 10 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0106] The above positive electrode current collector may include, 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, and may be in the form of a foil or sheet.

[0107] The above positive electrode active material layer may further include a binder and / or a conductive material.

[0108] The above binder may include, but is not limited to, polymers including polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0109] The above binder may be included in an amount of 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt%, based on the total weight of the positive electrode active material layer for the all-solid-state battery. Within the above content range, the binder can sufficiently exhibit adhesive ability without deteriorating battery performance.

[0110] The above conductive material is used to provide conductivity to the electrode, and in the battery to be constructed, any material that does not cause a chemical change and is electronically conductive can be used. Examples thereof include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nano fiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, and silver in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or a conductive material including a mixture thereof.

[0111] The conductive material may be included in an amount of 0.1 wt% to 5 wt%, or 0.1 wt% to 3 wt%, based on the total weight of the positive electrode active material layer for the all-solid-state battery. Within the above content range, the conductive material may improve electrical conductivity without degrading battery performance.

[0112] The thickness of the positive electrode active material layer may be 90 μm to 200 μm. For example, the thickness of the positive electrode active material layer may be 90 μm or more, 100 μm or more, 110 μm or more, 120 μm or more, 130 μm or more, 140 μm or more, 150 μm or more, 160 μm or more, 170 μm or more, 180 μm or more, or 190 μm or more, and may be 200 μm or less, 190 μm or less, 180 μm or less, 170 μm or less, 160 μm or less, 150 μm or less, 140 μm or less, 130 μm or less, 120 μm or less, or 110 μm or less.

[0113] In one embodiment, the all-solid-state battery may further include a buffer material to cushion changes in thickness that occur during charging and discharging. The buffer material may be positioned between the negative electrode and the case, and in the case of a battery in which one or more electrode assemblies are stacked, the buffer material may be positioned between different electrode assemblies.

[0114] The above-mentioned cushioning material may be a material having an elastic recovery rate of 50% or more and an insulating function, and specifically, may be silicone rubber, acrylic rubber, fluorine rubber, nylon, synthetic rubber, or a combination thereof. The above-mentioned cushioning material may be in the form of a polymer sheet.

[0115] FIG. 2 is a cross-sectional view of an all-solid-state battery according to one embodiment. Referring to FIG. 1, the all-solid-state battery (100) may have a structure in which an electrode assembly in which a negative electrode (400) including a negative electrode collector (401) and a negative electrode coating layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a case (500) such as a pouch. The all-solid-state battery (100) may further include an elastic layer on the outer side of at least one of the positive electrode (200) and the negative electrode (400). Although FIG. 2 illustrates one electrode assembly including the negative electrode (400), the solid electrolyte layer (300), and the positive electrode (200), an all-solid-state battery may be manufactured by laminating two or more electrode assemblies.

[0116] Fig. 3 schematically illustrates an all-solid-state battery according to another embodiment. The all-solid-state battery (100) illustrated in Fig. 3 includes a positive electrode (200) including a positive electrode current collector (201) and a positive electrode active material layer (203), a negative electrode (400) including a negative electrode current collector (401'), a negative electrode coating layer (403'), and a solid electrolyte (300) positioned between the positive electrode (200) and the negative electrode (400), and includes a battery case (500) in which these are housed, and further includes a lithium precipitation layer (405') between the negative electrode current collector (401') and the negative electrode coating layer (403'). When the all-solid-state battery is charged, the lithium precipitation layer can be formed by lithium ions being released from the positive electrode active material and deposited on the negative electrode current collector (401').

[0117] An all-solid-state battery according to one embodiment can be manufactured by a step of preparing a laminate by positioning a cathode, an anode, and a solid electrolyte layer between the cathode and the anode, and pressing the laminate.

[0118] The pressurizing process can be performed at a temperature ranging from 25°C to 90°C. In addition, the pressurizing process can be performed by pressurizing at a pressure of 550 MPa or less, for example, 500 MPa or less, for example, 1 MPa to 500 MPa. The pressurizing time can vary depending on the temperature and pressure, and can be, for example, less than 30 minutes. The pressurizing process can be, for example, isostatic pressing, roll pressing, plate pressing, or warm isostatic pressing.

[0119] 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.

[0120] (Example 1)

[0121] (1) Manufacturing of cathode

[0122] Carbon black and 2-naphthalene thiol powder were mixed in a weight ratio of 10:1. This mixture was heat-treated at 80°C. The heat-treated product was prepared by adding AgNO3 and NaBH4 reducing agents in a water solvent. At this time, AgNO3 was used so that the reduced Ag was 15 wt% based on 100 wt% of the total weight of the supported product. In addition, the amount of NaBH4 reducing agent was used so that the molar equivalent ratio with AgNO3 was 1:2.

[0123] The obtained mixture was heat-treated at 200°C for 2 hours under a nitrogen atmosphere to prepare a cathode catalyst. In the prepared cathode catalyst, the content of silver was 15 wt%, the content of carbon black was 77.3 wt%, the content of 2-naphthalene thiol was 7.7 wt%, and the carbon black was coated with 2-naphthalene thiol.

[0124] The above cathode catalyst, argyrodite-type solid electrolyte (Li6PS5Cl, average particle size (D50): about 1 μm), and polyvinylidene fluoride were mixed in a weight ratio of 81:11:8 in an N-methyl pyrrolidone solvent to prepare a cathode coating layer slurry.

[0125] The manufactured slurry was coated on a stainless steel foil current collector, and then vacuum-dried at 80°C to manufacture a negative electrode including a 12 μm thick negative electrode coating layer and a 10 μm thick current collector.

[0126] (2) Preparation of solid electrolyte layer

[0127] An isobutyl isobutylate binder solution (solid content: 50 wt%) containing butyl acrylate, an acrylate polymer, was added to an argyrodite-type solid electrolyte Li6PS5Cl and mixed. At this time, the mixing ratio of the solid electrolyte and the binder was set to a weight ratio of 98.7:1.3.

[0128] The above mixing process was performed using a sinky mixer. 2 mm zirconia balls were added to the resulting mixture and stirred again using the sinky mixer to produce a slurry. The slurry was cast onto a polytetrafluoroethylene film and dried at room temperature to produce a solid electrolyte with a solid electrolyte layer thickness of 100 μm.

[0129] (3) Manufacturing of anode

[0130] LZO (Li-doped zinc oxide) coated cathode active material (LiNi 0.9 Mn 0.05 Co 0.05 A mixture was prepared by mixing O2), argyrodite-type solid electrolyte Li6PS5Cl, conductive carbon nanofibers, and binder polytetrafluoroethylene in a weight ratio of 85:15:3:1.5.

[0131] The prepared mixture was coated on an aluminum foil current collector and then vacuum-dried at 45°C to prepare a negative electrode including a 160 μm thick positive active material layer and a 10 μm thick current collector.

[0132] (4) Manufacturing of all-solid-state full cells

[0133] The manufactured negative electrode, solid electrolyte, and positive electrode were sequentially stacked, and a pressure of 2 MPa was applied to manufacture an all-solid-state battery.

[0134] (Example 2)

[0135] (1) Manufacturing of cathode

[0136] Carbon black and 2-naphthalene thiol powder were mixed in a weight ratio of 10:2. This mixture was heat-treated at 80°C. The heat-treated product was prepared by adding AgNO3 and NaBH4 reducing agents in a water solvent. At this time, AgNO3 was used so that the reduced Ag was 15 wt% based on 100 wt% of the total weight of the supported product. In addition, the amount of NaBH4 reducing agent was used so that the molar equivalent ratio with AgNO3 was 1:2.

[0137] The obtained mixture was heat-treated at 200°C for 2 hours under a nitrogen atmosphere to prepare a cathode catalyst. In the prepared cathode catalyst, the content of silver was 15 wt%, the content of carbon black was 69.5 wt%, the content of 2-naphthalene thiol was 15.5 wt%, and the carbon black was coated with 2-naphthalene thiol.

[0138] A negative electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the above-mentioned negative electrode catalyst was used.

[0139] (Comparative Example 1)

[0140] A cathode catalyst was prepared by mechanically mixing carbon black and silver (Ag) in a weight ratio of 75:25 using mortar. In the prepared cathode catalyst, the content of silver was 25 wt% and the content of carbon black was 75 wt%.

[0141] A negative electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the negative electrode catalyst was used.

[0142] (Comparative Example 2)

[0143] Carbon black and 2-naphthalene thiol powder were mixed in a weight ratio of 10:1. This mixture was heat-treated at 80°C. The heat-treated product was prepared by adding AgNO3 and NaBH4 reducing agents in a water solvent. At this time, AgNO3 was used so that the reduced Ag was 15 wt% based on 100 wt% of the total weight of the supported product. In addition, the amount of NaBH4 reducing agent was used so that the molar equivalent ratio with AgNO3 was 1:2.

[0144] The obtained mixture was heat-treated at 400°C for 8 hours under a nitrogen atmosphere to produce a cathode catalyst from which residual thiol compounds were removed. In the produced cathode catalyst, the content of silver was 15 wt%, the content of carbon black was 77.3 wt%, and the content of 2-naphthalene thiol was 7.7 wt%.

[0145] A negative electrode and an all-solid-state battery were manufactured in the same manner as in Example 1, except that the negative electrode catalyst was used.

[0146] (Comparative Example 3)

[0147] Carbon black and 2-naphthalene thiol powder were mixed in a weight ratio of 10:1. This mixture was heat-treated at 80°C. The heat-treated product was prepared by adding AgNO3 and NaBH4 reducing agents in a water solvent. At this time, AgNO3 was used so that the reduced Ag was 15 wt% based on 100 wt% of the total weight of the supported product. In addition, the amount of NaBH4 reducing agent was used so that the molar equivalent ratio with AgNO3 was 1:2.

[0148] The obtained mixture was heat-treated at 400°C for 8 hours under a nitrogen atmosphere to produce a cathode catalyst from which residual thiol compounds were removed. In the produced cathode catalyst, the content of silver was 15 wt%, the content of carbon black was 77.3 wt%, and the content of 2-naphthalene thiol was 7 wt%.

[0149] The above cathode coating composition and polyvinylidene fluoride were mixed in a 92:8 weight ratio in a distilled water solvent to prepare a cathode coating slurry.

[0150] The manufactured slurry was coated on a stainless steel foil current collector, and then vacuum-dried at 80°C to manufacture a negative electrode including a 12 μm thick negative electrode coating layer and a 10 μm thick current collector.

[0151] (Comparative Example 4)

[0152] Carbon black and 2-naphthalene thiol powder were mixed in a weight ratio of 10:4. This mixture was heat-treated at 80°C. The heat-treated product was prepared by adding AgNO3 and NaBH4 reducing agents in a water solvent. At this time, AgNO3 was used so that the reduced Ag was 15 wt% based on 100 wt% of the total weight of the supported product. In addition, the amount of NaBH4 reducing agent was used so that the molar equivalent ratio with AgNO3 was 1:2.

[0153] The obtained mixture was heat-treated at 200°C for 2 hours under a nitrogen atmosphere to prepare a cathode catalyst from which residual thiol compounds were removed. In the prepared cathode catalyst, the content of silver was 11 wt%, the content of carbon black was 63.6 wt%, and the content of 2-naphthalene thiol was 25.4 wt%. At this time, it can be seen that the thiol compound was used in excess, resulting in the agglomeration of silver and thiol, and the presence of desorbed Ag, resulting in an Ag content of 11 wt% instead of the intended 15 wt%.

[0154] The above cathode coating composition and polyvinylidene fluoride were mixed in a 92:8 weight ratio in a distilled water solvent to prepare a cathode coating slurry.

[0155] The manufactured slurry was coated on a stainless steel foil current collector, and then vacuum-dried at 80°C to manufacture a negative electrode including a 12 μm thick negative electrode coating layer and a 10 μm thick current collector.

[0156]

[0157] Experimental Example 1) TEM-EDS (Energy dispersive X-ray spectroscopy) photo

[0158] TEM-EDS images for confirming the composition of the cathode surface manufactured in Example 1 are shown in FIG. 4. FIG. 4 (a) is a high-angle annular dark-field TEM image that can show the entire composition of the cathode surface, FIG. 4 (b) is a TEM-EDS image showing the presence of carbon, FIG. 4 (c) is a TEM-EDS image showing the presence of sulfur, and FIG. 4 (d) is a TEM-EDS image showing the presence of silver. As shown in FIGS. 4 (a) to (d), it can be seen that sulfur exists on the carbon surface, and silver is distributed at the location where the sulfur exists.

[0159] Experimental Example 2) Evaluation by X-ray Photoelectron Spectroscopy (XPS)

[0160] XPS S2p spectra were measured for the cathodes manufactured according to Examples 1 to 2 and Comparative Examples 1 to 4. The results are shown in Table 1 below.

[0161] Additionally, the results of Example 1 and Comparative Example 2 are shown in Fig. 5.

[0162] As shown in Fig. 5, Example 1 can be seen to have a first peak corresponding to Ag2S appearing at a binding energy of 160 eV to 162 eV and a second peak corresponding to thiol appearing at a binding energy of 163 eV to 165 eV. In addition, it can be seen that the height ratio of the second peak to the height of the first peak is approximately 7.

[0163] On the other hand, in the case of Comparative Example 2, it can be seen that practically only the first peak exists.

[0164] Experimental Example 3) Evaluation of ionic conductivity

[0165] Using the negative electrode coating layer slurries of Examples 1 to 3 and Comparative Examples 1 to 4, symmetric cells were manufactured and ionic conductivity was measured. The symmetric cells were manufactured with the structure shown in Fig. 6. In Fig. 6, SUS is a stainless steel foil current collector, the solid electrolyte was the solid electrolyte layer of Example 1, and the negative electrode coating layer was formed using the negative electrode coating layer slurries manufactured in Examples 1 to 4 and Comparative Examples 1 to 4.

[0166] The ionic conductivity of the manufactured battery was measured. The results are shown in Table 1 below. The ionic conductivity was measured at room temperature (25°C) using an electric impedance spectroscopy (VSP model, Bio-Logic SAS) after sampling the separator at 36 Φ (36 mm in diameter). At this time, a frequency of 10,000 MHz to 1 Hz was scanned using an amplitude of 1,000 mV at an open circuit potential.

[0167] Height ratio of the second peak / first peak Ionic conductivity (S / ㎠) Example 174.7 X 10 -5 Example 2104.9 X 10 -5 Comparative example 1X1.3 X 10 -6 Comparative example 203.7 X 10 -6 Comparative example 302.0 X 10 -7 Comparative example 4248.9 X 10 -6

[0168]

[0169] As shown in Table 1 above, Comparative Example 1, in which carbon black and silver are simply mixed, has a much lower ionic conductivity than Example 1, Block 2. In addition, when manufacturing the cathode catalyst, 2-naphthalene thiol powder was used, and a bond between sulfur and silver was formed, but the thiol was removed by high-temperature heat treatment, so Comparative Example 2, in which the height ratio of the second peak / first peak was 0, showed an ionic conductivity somewhat similar to that of Comparative Example 1. In other words, it can be seen that the bond between sulfur and silver is not significant when an argyrodite-type solid electrolyte is included.

[0170] In addition, the all-solid-state battery of Comparative Example 2 showed improved ionic conductivity compared to Comparative Example 3, but lower ionic conductivity than Examples 1 and 2. From these results, it can be seen that the effect of improving ionic conductivity by including a solid electrolyte is somewhat low when no thiol compound remains in the negative electrode coating layer. In addition, Comparative Example 3 showed very low ionic conductivity, and from these results, it can be predicted that it will show deteriorated rate characteristics.

[0171] In addition, it can be seen that the all-solid-state battery of Comparative Example 4 used an excessive amount of thiol compound, so that the thiol was aggregated in the post-process and the bonding of Ag and sulfur was reduced, so that the actual remaining Ag content was reduced compared to the target Ag content in the final cathode catalyst, and the Ag content was reduced compared to the system, and as a result, the ionic conductivity was reduced.

[0172] On the other hand, Example 1, where the second peak / first peak height ratio was 7, and Example 2, where the height ratio was 10, exhibited very excellent ionic conductivity.

[0173] Experimental Example 4) Thermogravimetric Analysis (TGA)

[0174] In the cathode catalyst manufacturing process of Example 1 above, thermogravimetric analysis (TGA) was measured for the product before heat treatment and the cathode catalyst after heat treatment. Among the results, the weight % change result (solid line in FIG. 7) and the DTG (derivative thermo gravimetry, % / min) value (dotted line in FIG. 7) are shown in FIG. 7. The thermogravimetric analysis measurement method was performed in an argon atmosphere, and the measurement was performed at a heating rate of 10°C / min (Ramp 10°C / min to 900°C) from room temperature (25°C) to 900°C under a N2 atmosphere.

[0175] As shown in Fig. 7, the product before heat treatment showed a weight loss of 8.9 wt%, whereas the cathode catalyst after heat treatment showed no weight loss. This weight loss is thought to be a result of the thiol compound, indicating that virtually no thiol compound present before heat treatment remains after heat treatment.

[0176] 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 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. When measured by X-ray photoelectron spectroscopy (XPS), in the S2p spectrum, it has a first peak appearing at a binding energy of 160 eV to 162 eV and a second peak appearing at a binding energy of 163 eV to 165 eV, and the ratio of the second peak to the first peak is 3 to 12, A cathode coating layer comprising a mixture of metal particles and carbon-based materials A cathode for an all-solid-state battery comprising:

2. In paragraph 1, An all-solid-state battery negative electrode, wherein the negative electrode coating layer further contains sulfur.

3. In paragraph 1, An all-solid-state battery negative electrode, wherein the first peak corresponds to Ag2S and the second peak corresponds to thiol.

4. In paragraph 1, An all-solid-state battery negative electrode having a ratio of the second peak to the first peak of 3 to 10.

5. In paragraph 1, The above ratio is the height ratio of the peaks for an all-solid-state battery negative electrode.

6. In paragraph 1, An all-solid-state battery negative electrode, wherein the negative electrode coating layer further includes a solid electrolyte having an average particle diameter of 1 ㎛ to 6 ㎛.

7. In paragraph 1, The above carbon-based material is an anode for an all-solid-state battery, which is amorphous carbon, crystalline carbon or a mixture thereof.

8. In paragraph 1, The above metal is Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd or a combination thereof.

9. In paragraph 6, An all-solid-state battery negative electrode having a content of the solid electrolyte of 5 to 25 wt% based on 100 wt% of the total negative electrode coating layer.

10. In paragraph 1, The above solid electrolyte is a sulfide-based solid electrolyte, and is an all-solid-state battery negative electrode.

11. The cathode of any one of clauses 1 to 10; Bipolar; and A solid electrolyte layer positioned between the cathode and the anode An all-solid-state battery comprising:

12. In paragraph 11, The above all-solid-state battery further includes a lithium-containing layer formed between the current collector and the negative electrode coating layer during initial charging.

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