Negative electrode coating composition for all-solid-state battery, method for preparing same, and all-solid-state battery including same

Abstract

The present invention relates to a negative electrode coating composition for an all-solid-state battery and an all-solid-state battery including the same, in which the negative electrode coating composition for an all-solid-state battery includes a metal and a carbon-based material, and the metal and the carbon-based material are chemically bonded by sulfur.

Description

Technical Field

[0001] The present disclosure relates to a negative electrode coating composition for an all-solid-state battery and an all-solid-state battery including the same. Background Art

[0002] Recently, with the rapid spread of electronic devices using batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for rechargeable batteries with relatively high capacity and light weight is increasing rapidly. In particular, rechargeable lithium batteries have attracted attention as a driving power source for portable devices due to their light weight and high energy density. Accordingly, research and development for improving the performance of rechargeable lithium batteries are actively underway.

[0003] An all-solid-state battery among rechargeable lithium batteries refers to a battery in which all materials are solid, particularly a battery using a solid electrolyte. One method of increasing the energy density of these all-solid-state batteries is to use lithium metal as the negative electrode. However, in this case, there are problems caused by lithium volume expansion and irreversible dendritic crystal growth during charging and discharging.

[0004] To solve these problems, a method of configuring a negative electrode by forming a layer in which lithium is deposited on a negative electrode current collector during charging and discharging without using lithium metal itself is being studied. However, this method is not suitable because it causes low power characteristics and an excessive occurrence of short-circuit phenomena. Summary of the Invention

[0005] Technical Problem

[0006] An embodiment provides a negative electrode coating composition for an all-solid-state battery, which has a strong binding force between metal and carbon.

[0007] Another embodiment provides an all-solid-state battery including the negative electrode coating composition.

[0008] Technical Solution

[0009] An embodiment provides a negative electrode coating composition for an all-solid-state battery including a metal and a carbonaceous material, wherein the metal and the carbonaceous material are chemically bonded through sulfur.

[0010] In a spectrum obtained by XPS analysis, the negative electrode coating composition may have a peak related to a metal-sulfur bond.

[0011] In an S2p spectrum obtained by XPS analysis, the negative electrode coating composition may have a peak appearing at a binding energy of 160 eV to 162 eV.

[0012] The carbonaceous material may be amorphous carbon, crystalline carbon, or a mixture thereof.

[0013] The metal can be Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd, or a combination thereof.

[0014] Based on the total amount of the metal and the carbonaceous material of 100 wt%, the amount of the metal can be 3 wt% to 40 wt%.

[0015] Another embodiment provides a method for preparing a negative electrode coating composition for a all-solid-state battery, which includes: mixing a carbonaceous material and a sulfur raw material to prepare a mixture; loading a metal on the mixture to prepare a loaded product; and performing a heat treatment on the loaded product.

[0016] The sulfur raw material can be a thiol compound, a sulfide compound, a thiophene compound, a sulfonic acid, a sulfone, a sulfoxide, or a combination thereof.

[0017] The heat treatment can be performed at 100 °C to 500 °C.

[0018] Another embodiment provides a all-solid-state battery, including: a negative electrode including a current collector and a negative electrode coating on one surface of the current collector; a positive electrode; and a solid electrolyte layer between the negative electrode and the positive electrode, wherein the negative electrode coating includes the negative electrode coating composition.

[0019] The solid electrolyte can be a sulfide-based solid electrolyte.

[0020] The all-solid-state battery can further include a lithium-containing layer formed between the current collector and the negative electrode coating during initial charging.

[0021] Advantageous Effects

[0022] The negative electrode coating composition for a all-solid-state battery according to the embodiment has a strong binding force between the metal and the carbon, and the metal is uniformly dispersed in the carbonaceous material, thereby preventing the aggregation of metal particles. Description of the Drawings

[0023] Figure 1 It is a schematic diagram schematically illustrating a all-solid-state battery according to the embodiment.

[0024] Figure 2 It is a schematic cross-sectional view showing the state of the all-solid-state battery according to the embodiment after charging.

[0025] Figure 3 It is a TEM photograph of the negative electrode coating composition manufactured in Example 1.

[0026] Figure 4 It is a TEM photograph of the negative electrode coating composition manufactured in Comparative Example 1.

[0027] Figure 5Graph showing the XPS S2p spectra of the negative electrode coating compositions prepared according to Example 1, Comparative Example 1, and Comparative Example 2.

[0028] Figure 6 Graph showing the weight change obtained by measuring the thermogravimetric analysis of the negative electrode coating compositions of Example 1 and Comparative Example 2.

[0029] Figure 7 Graph showing the DTG change obtained by measuring the thermogravimetric analysis of the negative electrode coating compositions of Example 1 and Comparative Example 2. Detailed Description

[0030] Hereinafter, embodiments of the present invention will be described in detail. However, these embodiments are merely examples, and the present invention is not limited thereto, and the present invention is defined by the scope of the claims.

[0031] As used herein, unless otherwise specifically defined, it will be understood that when an element (such as a layer, film, region, or substrate) is referred to as being "on" another element, it can be directly on the other element or there can also be intervening elements.

[0032] In the present invention, "particle size" or "particle diameter" can be an average particle size. Additionally, the average particle diameter can be defined as the average particle diameter (D50) based on 50% of the cumulative volume in the cumulative size distribution curve. The particle diameter can be measured, for example, by electron microscopy using a scanning electron microscope (SEM) or a field emission scanning electron microscope (FE-SEM) or by a laser diffraction method. It can be measured by the following laser diffraction method. The particles to be measured are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 of Microtrac), ultrasonic waves of about 28 kHz are irradiated at an output of about 60 W, and the average particle diameter (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0033] An embodiment relates to a negative electrode coating composition for an all-solid-state battery. In the embodiment, the negative electrode coating for an all-solid-state battery refers to a material that helps lithium ions to be deintercalated from the positive electrode active material and move toward the negative electrode and precipitate on the surface of the current collector during charging and discharging of the all-solid-state battery. Such a negative electrode coating composition can be included in the negative electrode coating of the all-solid-state battery. Additionally, the negative electrode of the all-solid-state battery including such a negative electrode coating has a lithium deposition layer formed between the current collector and the negative electrode coating due to the precipitation of lithium ions, and this lithium deposition layer acts as the negative electrode active material, and such a negative electrode is generally referred to as a deposition-type negative electrode.

[0034] According to an embodiment, the negative electrode coating composition for an all-solid-state battery includes a metal and a carbonaceous material, wherein the metal and the carbonaceous material are chemically bonded through sulfur.

[0035] More specifically explained, the metal and the carbonaceous material are not simply physically mixed or aggregated, but are chemically bonded to each other. The chemical bond between the metal and the carbonaceous material can be a chemical bond formed through sulfur.

[0036] The chemical bonding of the metal and the carbonaceous material can be achieved by using a sulfur raw material in the preparation of the negative electrode coating composition. It will be described in detail in the preparation of the negative electrode coating composition.

[0037] Because the metal and the carbonaceous material are chemically bonded, the bonding strength is more excellent than physical bonding. Therefore, if the negative electrode is manufactured using this negative electrode coating composition, the problem of the metal and the carbonaceous material separating from each other during the mixing process can be effectively prevented. Generally, in the negative electrode coating composition, the metal exists in the form of a mixture of the metal and the carbonaceous material, and at this time, it is difficult for the metal to be uniformly dispersed in the carbonaceous material. However, in the negative electrode coating composition according to the embodiment, the metal can be uniformly dispersed through functional groups uniformly distributed in the carbonaceous material. Therefore, metal aggregation can be prevented, and thus the current distribution in the negative electrode can be made uniform.

[0038] According to an embodiment, the negative electrode coating composition is a composition in which a metal and a carbonaceous material are chemically bonded through sulfur, which can be confirmed by peaks related to metal-sulfur (M-S) bonding in the spectrum obtained by XPS analysis.

[0039] For example, if the metal is silver, the S2p spectrum obtained by XPS analysis may have peaks appearing at a binding energy of 160 eV to 162 eV.

[0040] If the metal and the carbonaceous material are simply mixed, that is, not chemically bonded through sulfur, then according to XPS analysis, these peaks will not appear. Additionally, even if a sulfur-containing compound is coated on the carbonaceous material but there is no chemical bonding, two peaks can be measured: one peak appears at a binding energy of 160 eV to 162 eV, and the other peak appears at a binding energy of 163 eV to 166 eV.

[0041] The carbonaceous material can be amorphous carbon, crystalline carbon, or a mixture thereof. The amorphous carbon can be, for example, carbon black, acetylene black, super conductive acetylene carbon black, Ketjen black, furnace black, activated carbon, or a combination thereof. An example of the above carbon black is Super P (Timcal). The crystalline carbon can be natural graphite, artificial graphite, carbon nanotubes, graphene, or a combination thereof. The crystalline carbon can have an amorphous shape, plate-like, flaky, spherical, or fibrous shape.

[0042] In an embodiment, the metal may be Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd, or a combination thereof. Since the negative electrode coating composition includes the metal, the conductivity of the negative electrode can be further improved.

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

[0044] In the negative electrode coating composition according to the embodiment, based on the total amount of the negative electrode coating composition of 100 wt%, the amount of the metal may be 3 wt% to 40 wt%, 3 wt% to 30 wt%, 4 wt% to 25 wt%, 5 wt% to 20 wt%, or 5 wt% to 15 wt%.

[0045] In addition, based on the total amount of the negative electrode coating composition of 100 wt%, a carbonaceous material may be included in an amount of 60 wt% to 97 wt%, 70 wt% to 97 wt%, 75 wt% to 96 wt%, 80 wt% to 95 wt%, or 85 wt% to 95 wt%.

[0046] Since the metal and the carbonaceous material are chemically bonded by sulfur in the negative electrode coating composition, sulfur may be present in the negative electrode coating composition. This does not mean that sulfur exists separately and independently because it is used to chemically bond the metal and the carbonaceous material. Here, the amount of sulfur is an amount that can bond the metal and the carbonaceous material, and since it is a trace amount, it does not need to be a quantitatively analyzable amount. Therefore, the amount of sulfur does not need to be limited.

[0047] If the amounts of the metal or the carbonaceous material are within the above ranges, the metal can be uniformly dispersed in the carbonaceous material. In addition, if the amounts of the metal and the carbonaceous material are within the above ranges, during charging, the lithium ions deintercalated from the positive electrode active material move toward the negative electrode, and a lithium deposition layer is substantially mostly formed between the current collector and the negative electrode coating. Therefore, if lithium precipitation occurs on the surface of the negative electrode coating, problems such as a short-circuit problem, a problem caused by a side reaction with the electrolyte, or a problem of cracks occurring on the negative electrode side can be effectively suppressed.

[0048] The amorphous carbon may be single particles or may be an aggregate having secondary particles in which primary particles are aggregated. If the amorphous carbon is single particles, it may be amorphous carbon particles having an average particle diameter of less than or equal to 100 nm (e.g., a nano size of 10 nm to 100 nm).

[0049] Alternatively, if the amorphous carbon is an aggregate, the particle size of the primary particles can be 20 nm to 100 nm, and the particle size of the secondary particles can be 1 μm to 20 μm.

[0050] In an embodiment, the particle size of the primary particles can be greater than or equal to 20 nm, greater than or equal to 30 nm, greater than or equal to 40 nm, greater than or equal to 50 nm, greater than or equal to 60 nm, greater than or equal to 70 nm, greater than or equal to 80 nm, or greater than or equal to 90 nm, and less than or equal to 100 nm, less than or equal to 90 nm, less than or equal to 80 nm, less than or equal to 70 nm, less than or equal to 60 nm, less than or equal to 50 nm, less than or equal to 40 nm, or less than or equal to 30 nm.

[0051] In an embodiment, the particle size of the secondary particles can be greater than or equal to 1 μm, greater than or equal to 3 μm, greater than or equal to 5 μm, greater than or equal to 7 μm, greater than or equal to 10 μm, or greater than or equal to 15 μm, and less than or equal to 20 μm, less than or equal to 15 μm, less than or equal to 10 μm, less than or equal to 7 μm, less than or equal to 5 μm, or less than or equal to 3 μm.

[0052] The shape of the primary particles can be spherical, ellipsoidal, plate-like, and combinations thereof, and in an embodiment, the shape of the primary particles can be spherical, ellipsoidal, and combinations thereof.

[0053] The negative electrode coating composition according to an embodiment can be prepared by the following preparation process.

[0054] Mix a carbonaceous material with a sulfur raw material. This mixing process can be carried out by a dry method or a wet method. If the mixing process is carried out by a dry method, it can use a sulfur raw material that is a solid phase at room temperature, and if it is carried out by a wet method, it can use a sulfur raw material that is a liquid phase at room temperature.

[0055] The carbonaceous material can be the amorphous carbon or crystalline carbon as described above.

[0056] The sulfur raw material can be a thiol compound, a sulfide compound, a thiophene compound, a sulfonic acid, a sulfone, a sulfoxide, or a combination thereof. In an embodiment, the sulfur-containing compound can be a thiol compound.

[0057] The thiol compound can be mercaptoacetic 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, and the sulfide compound can be polyphenylene sulfide, carbon disulfide, metal sulfide, or a combination thereof. Among the metal sulfides, the metal can be Ag, Na, Zn, Fe, or a combination thereof. Additionally, the thiophene compound can be thiophene (C4H4S), 2-methylthiophene, benzothiophene, 4,6-dimethyldibenzothiophene, or a combination thereof. The sulfonic acid can be p-toluenesulfonic acid, sodium dodecylbenzenesulfonate, taurine, or a combination thereof, the sulfone can be dimethyl sulfone, 4,4'-dichlorodiphenyl sulfone, or a combination thereof, and the sulfoxide can be dimethyl sulfoxide, methyl phenyl sulfoxide, or a combination thereof.

[0058] Regardless of whether the mixing process is carried out in a wet or dry manner, the carbonaceous material and the sulfur raw material can be mixed at a weight ratio of 4:1 to 999:1. The mixing ratio can be a weight ratio of 4:1 to 900:1, 5:1 to 100:1, or 5:1 to 20:1.

[0059] Next, the obtained mixture is subjected to heat treatment, and depending on the mixing process and the heat treatment process, the surface of the carbonaceous material can be coated with the sulfur raw material. The heat treatment process can be carried out at 70 °C to 110 °C.

[0060] A metal is loaded onto the obtained heat-treated product to produce a loaded product. The loading process can be carried out by adding a metal compound and a reducing agent to the mixture. This addition process can be carried out in a solvent, and the solvent can be water, ethanol, glycerol, benzene, xylene, or a combination thereof. Additionally, NaBH4, ascorbic acid, trisodium citrate, ethylene glycol, or a combination thereof can be used as the reducing agent.

[0061] In the process of loading the metal, based on the total weight of the carbonaceous material and the metal in the loaded product being 100 wt%, the amount of the metal compound used can be adjusted to 3 wt% to 40 wt%, 4 wt% to 25 wt%, 5 wt% to 20 wt%, or 5 wt% to 15 wt%. Additionally, the reducing agent can be used in an amount suitable for the reduction reaction of the metal compound to occur, and there is no particular limitation. For example, based on 100 wt% of the metal compound, the amount of the reducing agent used can be 10 wt% to 300 wt%.

[0062] The metal compound can be a metal nitride, a metal sulfate, a metal perchlorate, or a combination thereof. For example, if the metal is Ag, it can be AgNO3, Ag2SO4, AgClO4, or a combination thereof.

[0063] The obtained supported product is heat-treated. The heat treatment process can be carried out at a temperature at which the sulfur raw material can be decomposed and removed. For example, it can be carried out at 100 °C to 500 °C, 150 °C to 500 °C, 200 °C to 450 °C, or 200 °C to 400 °C. Specifically, if a thiol compound is used as the sulfur raw material, the heat treatment can be carried out at 100 °C to 400 °C.

[0064] In addition, the heat treatment can be carried out under a nitrogen atmosphere, an argon atmosphere, or a combination thereof. In addition, the heat treatment can be carried out for 2 hours to 20 hours.

[0065] According to this heat treatment process, the sulfur raw material is decomposed, so that no sulfur raw material remains in the final negative electrode coating. Since sulfur exists by combining with the metal and carbonaceous materials in the negative electrode coating, the metal and carbonaceous materials can be included in the negative electrode coating in a state of being chemically bonded through sulfur.

[0066] Another embodiment provides a all-solid-state battery including a negative electrode coating composition.

[0067] The all-solid-state battery includes: a negative electrode including a current collector and a negative electrode coating on one surface of the current collector; a positive electrode; and a solid electrolyte layer between the negative electrode and the positive electrode, wherein the negative electrode coating includes the negative electrode coating composition according to the embodiment.

[0068] Based on 100 wt% of the total negative electrode coating, the amount of the negative electrode coating composition can be 60 wt% to 99 wt% or 85 wt% to 99 wt%.

[0069] The binder can include a water-insoluble binder, a water-soluble binder, or a combination thereof.

[0070] The water-insoluble binder can include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene-propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, polyacrylate, or a combination thereof.

[0071] The water-soluble binder can include a rubber-based binder or a polymer resin binder. The rubber binder can be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and a combination thereof. The polymer resin binder can be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and a combination thereof.

[0072] If a water-soluble binder is used as the negative electrode binder above, a thickener capable of imparting viscosity may be used together, and the thickener may include, for example, a cellulose compound. The cellulose compound may include carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, an alkali metal salt thereof, or a combination thereof. The alkali metal may be Na, K, or Li. Based on 100 parts by weight of the negative electrode coating composition, the amount of these thickeners used may be 0.1 part by weight to 10 parts by weight. The cellulose compound may also act as a binder.

[0073] The binder is not limited thereto, and any binder used in the related art field may be used, and the amount of the binder may also be appropriately adjusted.

[0074] Based on 100 wt% of the total negative electrode coating, the binder may be included in an amount of 1 wt% to 15 wt%. For example, based on 100 wt% of the total negative electrode coating, the amount of the binder present may be 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.

[0075] If the binder is included in the negative electrode coating of the all-solid-state battery within the above content range, the resistance and adhesion strength can be improved, thereby improving the characteristics (battery capacity and output characteristics) of the all-solid-state battery.

[0076] The negative electrode coating may further include additives (such as fillers and dispersants). In addition, known materials commonly used in all-solid-state batteries may be used as fillers, dispersants, etc. that may be included in the negative electrode coating.

[0077] According to an embodiment, the negative electrode may further include a lithium-containing layer formed between the current collector and the negative electrode coating during the initial charging after battery preparation. 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. If the thickness of the lithium-containing layer is within the above range, it can appropriately play the role of a lithium storage layer and can further improve its cycle life.

[0078] If, after manufacturing the battery, during charging, lithium ions are deintercalated from the positive electrode active material, pass through the solid electrolyte, and move toward the negative electrode, resulting in lithium precipitation and deposition on the negative electrode current collector, a lithium-containing layer can be formed.

[0079] The charging process can be a formation process carried out 1 to 3 times at 0.05C to 1C at about 25°C to 50°C. If lithium precipitates and deposits to form a lithium-containing layer, then during discharge, the lithium included in the lithium-containing layer is ionized and moves toward the positive electrode, so this lithium can be used as the negative electrode active material.

[0080] In an embodiment, since the lithium-containing layer is located between the current collector and the negative electrode coating, the negative electrode coating can act as a protective layer for the lithium-containing layer, thereby suppressing the precipitation and growth of lithium dendrites. As a result, short circuits and capacity reduction of the all-solid-state battery can be suppressed, and thus the cycle life of the all-solid-state battery can be improved.

[0081] The current collector can 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 can be in the form of a foil or sheet. The thickness of the negative electrode current collector can be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0082] The current collector can include a metal substrate and can further include a thin film formed on the substrate. The thin film can include elements that can form an alloy with lithium, and can be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, or a combination thereof, but is not limited thereto, and in the art, any element that can form an alloy with lithium can be used. If the current collector further includes a thin film and a lithium-containing layer is formed by precipitation during charging, a flatter lithium-containing layer can be formed, thereby further improving the cycle life of the all-solid-state battery.

[0083] The thickness of the thin film can be 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thin film thickness is within the above range, the cycle life characteristics can be further improved.

[0084] The solid electrolyte included in the solid electrolyte layer can 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).

[0085] Sulfide solid electrolytes can be Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element, such as 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 (where m and n are integers of 0 or more and 12 or less, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are each 0 or more and 12 or less and M is one of P, Si, Ge, B, Al, Ga, or In) or Li a M b P c S d A e (where a, b, c, d, and e are each 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). For example, it can be 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 PS 6-x Br x (0 ≤ x ≤ 2) or Li 7-x PS 6-x I x (0 ≤ x ≤ 2). Additionally, specifically, it can be Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Cl, Li6PS5I, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 or Li 6.2 PS 5.2 Br 0.8 .

[0086] For example, the sulfide solid electrolyte can be a thiogermanate-type sulfide solid electrolyte. The sulfide solid electrolyte can be, for example, Li a Mb P c S d A e (where 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), 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 and so on.

[0087] The sulfide-based solid electrolyte can be amorphous, crystalline, or a mixture thereof. The sulfide-based solid electrolyte can be obtained, for example, 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 with excellent ionic conductivity can be prepared. The ionic conductivity can be further improved by adding SiS2, GeS2, B2S3, etc. as other components. Mechanical milling or a solution method can be used as the mixing method. Mechanical milling is carried out by putting the starting materials into a reactor and vigorously stirring them with a ball mill to make the starting materials into fine particles. The solution method can be carried out by mixing the starting materials in a solvent to obtain the solid electrolyte in the form of a precipitate. Additionally, an additional firing can be carried out after mixing. If an additional firing is carried out, the crystals of the solid electrolyte can become stronger.

[0088] Of course, commercially available solid electrolytes can be used as the sulfide-based solid electrolyte.

[0089] The oxide-based solid electrolyte can be, 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 and 0 ≤ y ≤ 1), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2 and 0 < y < 3), Li2O, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2 - type ceramics, garnet - type ceramics Li 3+x La3M2O 12 (M = Te, Nb or Zr, and x is an integer from 1 to 10) or a mixture thereof.

[0090] Solid polymer electrolytes can include, for example, one or more selected from the following: polyethylene oxide, poly(diallyldimethylammonium) trifluoromethanesulfonylimide (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 - silicate, Li 0.3 La 0.5 TiO3、Na5MSi4O 12 (where M is a rare earth element such as Nd, Gd, Dy, etc.), Li5ZrP3O 12 、Li5TiP3O12 , 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, and Q is Al or Ga), Li6BaLa2Ta2O 12 , Li7La3Zr2O 12 , Li5La3Nb2O 12 , Li5La3M2O 12 (M is Nb or Ta) and Li 7+x A x La 3-x Zr2O 12 (0 < x < 3, A is Zn).

[0091] Halide solid electrolytes may include Li element, M element (M is a metal other than Li), and X element (X is a halogen). Examples of X may include F, Cl, Br, and I. In particular, in halide solid electrolytes, at least one of Br and Cl is suitable as X above. Additionally, examples of M may include metal elements (such as Sc, Y, B, Al, Ga, and In).

[0092] The composition of halide solid electrolytes is not particularly limited, but may be represented by Li 6-3a M a Br b Cl c (where M is a metal other than Li, 0 < a < 2, 0 ≤ b ≤ 6, 0 ≤ c ≤ 6, b + c = 6). Herein, a may be 0.75 or more, 1 or more, and a may be 1.5 or less. b may be 1 or more, and may be 2 or more. Additionally, c may be 3 or more, and may be 4 or more. Specific examples of halide solid electrolytes may be Li3YBr6, Li3YCl6, or Li3YBr2Cl4.

[0093] The solid electrolyte may be in the form of particles, and the average particle diameter (D50) may be less than or equal to 5.0 μm, for example, 0.1 μm to 5.0 μm, 0.5 μm to 5.0 μm, 0.5 μm to 4.0 μm, 0.5 μm to 3.0 μm, 0.5 μm to 2.0 μm, or 0.5 μm to 1.0 μm.

[0094] The solid electrolyte layer may further include a binder. Herein, the binder may be styrene-butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, but is not limited thereto, and any substance used as a binder in the art may be used. The acrylate polymer may be butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0095] The solid electrolyte layer may be formed by adding the solid electrolyte to a binder solution, coating it on a substrate film, and drying the resultant. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. The formation process of the solid electrolyte layer is well-known in the art, and thus its detailed description will be omitted.

[0096] The positive electrode includes a positive electrode current collector and a positive electrode active material layer on one surface of the positive electrode current collector.

[0097] The 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 intercalating and deintercalating lithium ions, and for example, the positive electrode active material may be at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and a combination thereof. Examples of the positive electrode active material may 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 B1 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 a Ni 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); Li a Ni 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); Li a Ni 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); Li a Ni b E c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c L 1 d G eO2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1); Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QS2; LiQS2; V2O5; LiV2O5; LiI 1 O2; LiNiVO4; Li (3-f) J2(PO4) 3( 0 ≤ f ≤ 2); Li (3-f) Fe2(PO4) 3( 0 ≤ f ≤ 2); or LiFePO4.

[0098] In the above chemical formulas, A is Ni, Co, Mn, or a combination thereof; B 1 is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, 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; and L 1 is Mn, Al, or a combination thereof.

[0099] According to an embodiment, the positive electrode active material may be a ternary lithium transition metal (such as LiNi x Co y Al z O2 (NCA), LiNi x Co y Mn z O2 (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1)).

[0100] Furthermore, the compound may have a coating on its surface or may be mixed with another compound having a coating. The coating may include at least one coating element compound selected from oxides of coating elements, hydroxides of coating elements, hydroxyoxides of coating elements, carbonate oxides of coating elements, and hydroxycarbonates of coating elements. The compound used for the coating may be amorphous or crystalline. The coating elements included in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. By using these elements in the compound, the coating can be provided in a manner that does not adversely affect the positive electrode active material. For example, the method may include any coating method (such as spraying, dipping, etc.), but since it is well known in the relevant art, it is not explained in more detail.

[0101] In addition, as the coating, any known coating for the positive electrode active material of all-solid-state batteries can be applied, and examples thereof include Li2O-ZrO2 (LZO).

[0102] In addition, if the positive electrode active material is a ternary compound including nickel, cobalt, and manganese or nickel, cobalt, and aluminum, the capacity density of the all-solid-state battery can be further improved, and the metal eluted from the positive electrode active material in the charged state can be further reduced. Therefore, the long-term reliability and cycle characteristics of the all-solid-state battery in the charged state can be further improved.

[0103] Here, examples of the shape of the positive electrode active material include particulate shapes (such as spheres and ellipsoids). In addition, the average particle size of the positive electrode active material is not particularly limited and may be within the range applicable to the positive electrode active material of existing all-solid-state rechargeable batteries. In addition, the amount of the positive electrode active material in the positive electrode active material layer is not particularly limited and may be within the range applicable to the positive electrode layer of existing all-solid-state rechargeable batteries.

[0104] The positive electrode active material layer may further include a solid electrolyte. The solid electrolyte included in the positive electrode active material layer may be the aforementioned solid electrolyte, and in this case, it may be the same as or different from the solid electrolyte included in the solid electrolyte layer. Based on the total weight of the positive electrode active material layer, the solid electrolyte may be included in an amount of 10 wt% to 30 wt%.

[0105] The 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 a sheet.

[0106] The positive electrode active material layer may further include a binder and / or a conductive material.

[0107] The binder may include, but is not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0108] Based on the total weight of the components of the positive electrode for the all-solid-state battery, or based on the total weight of the positive electrode active material layer, the binder may be included in an amount of 0.1 wt% to 5 wt% or 0.1 wt% to 3 wt%. Within the above content range, the binder can fully exhibit its binding ability without deteriorating the battery performance.

[0109] The conductive material is used to impart conductivity to the electrode, and any material that does not cause chemical changes and conducts electrons in the battery can be used. Examples thereof may include carbon materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.), metal materials including copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber, conductive polymers (such as polyphenylene derivatives), or mixtures thereof.

[0110] Based on the total weight of the components of the positive electrode for the all-solid-state battery, or based on the total weight of the positive electrode active material layer, the conductive material may be included in an amount of 0.1 wt% to 5 wt% or 0.1 wt% to 3 wt%. Within the above content range, the conductive material can improve the conductivity without deteriorating the battery performance.

[0111] 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 greater than or equal to 90 μm, greater than or equal to 100 μm, greater than or equal to 110 μm, greater than or equal to 120 μm, greater than or equal to 130 μm, greater than or equal to 140 μm, greater than or equal to 150 μm, greater than or equal to 160 μm, greater than or equal to 170 μm, greater than or equal to 180 μm or greater than or equal to 190 μm, and less than or equal to 200 μm, less than or equal to 190 μm, less than or equal to 180 μm, less than or equal to 170 μm, less than or equal to 160 μm, less than or equal to 150 μm, less than or equal to 140 μm, less than or equal to 130 μm, less than or equal to 120 μm or less than or equal to 110 μm.

[0112] As described above, since the thickness of the positive electrode active material layer is thicker than that of the negative electrode coating, the capacity of the positive electrode is greater than that of the negative electrode.

[0113] The positive electrode can be manufactured by forming a positive electrode active material layer on a positive electrode current collector using dry coating or wet coating.

[0114] In an embodiment, the all-solid-state battery may further include a buffer material to buffer the thickness change that occurs during charging and discharging. The buffer material may be present between the negative electrode and the housing, and in the case of a battery in which one or more electrode assemblies are stacked, it may be present between different electrode assemblies.

[0115] The buffer material may include a material having an elastic recovery rate of 50% or more and may have an insulating function, and specifically includes silicone rubber, acrylic rubber, fluorine rubber, nylon, synthetic rubber, or a combination thereof. The buffer material may be present in the form of a polymer sheet.

[0116] Figure 1 is a cross-sectional view of an all-solid-state battery according to an embodiment. Refer to Figure 1 , the all-solid-state battery 100 may have a structure in which an electrode assembly is accommodated in a housing (such as a pouch), and in this electrode assembly, a negative electrode 400 including a negative electrode current collector 401 and a negative electrode coating 403, a solid electrolyte layer 300, and a positive electrode 200 including a positive electrode active material layer 203 and a positive electrode current collector 201 are stacked. The all-solid-state battery 100 may further include an elastic layer 500 on the outer surface of at least one of the positive electrode 200 and the negative electrode 400. Figure 1 An electrode assembly including a negative electrode 400, a solid electrolyte layer 300, and a positive electrode 200 is illustrated, but the all-solid-state battery can be manufactured by stacking two or more electrode assemblies.

[0117] Figure 2 Schematically illustrates the structure of the all-solid-state battery in a charged state. The all-solid-state battery 100 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 and a negative electrode coating 403, and a solid electrolyte 300 between the positive electrode 200 and the negative electrode 400, and includes a battery housing 500 that houses these.

[0118] If this all-solid-state battery 100 is charged, then as shown in Figure 2 , lithium ions are deintercalated from the positive electrode active material and deposited on the negative electrode current collector 401', and as a result, a lithium deposition layer 405' is formed between the current collector 401' and the negative electrode coating 403".

[0119] The all-solid-state battery according to an embodiment can be manufactured by: placing a negative electrode, a positive electrode, and a solid electrolyte layer between the negative electrode and the positive electrode to prepare a stack, and pressing the stack.

[0120] The pressing process can be carried out in the range of 25°C to 90°C. Additionally, the pressing process can be carried out under a pressure less than or equal to 550 MPa, such as less than or equal to 500 MPa, for example, 1 MPa to 500 MPa. The pressing time can vary according to the temperature and pressure and can be, for example, less than 30 minutes. The pressing process can be, for example, isostatic pressing, roll pressing, plate pressing, or warm isostatic pressing.

[0121] Embodiments of the invention

[0122] Hereinafter, examples and comparative examples of the present invention will be described. However, these examples are not construed as limiting the scope of the present invention in any sense.

[0123] (Example 1)

[0124] (1) Fabrication of the negative electrode

[0125] Carbon black and 2-naphthalenethiol powder were mixed at a weight ratio of 10:1. The mixture was heat-treated at 90°C. AgNO3 and NaBH4 reducing agents were added to the heat-treated product in an aqueous solvent to prepare a loaded product. At this time, AgNO3 was used in an amount of 11 wt% based on the total weight of Ag and carbon black in the loaded product of 100 wt%. Additionally, the amount of NaBH4 reducing agent used was 22 wt% based on 100 wt% of AgNO3.

[0126] The obtained mixture was heat-treated in a nitrogen atmosphere at 400°C for 4 hours to prepare a negative electrode coating composition. In the prepared negative electrode coating composition, the amount of silver was 5 wt%, the amount of carbon black was 88 wt%, and the amount of sulfur was 1.1 wt%.

[0127] The negative electrode coating composition, styrene-butadiene rubber, and sodium carboxymethyl cellulose were mixed in an aqueous solvent at a weight ratio of 100:6:3 to prepare a negative electrode coating slurry.

[0128] The prepared slurry was coated on a stainless steel foil current collector and then vacuum-dried at 80°C to fabricate a negative electrode including a 12-μm-thick negative electrode coating and a 10-μm-thick current collector. The thickness of the negative electrode coating was 12 μm.

[0129] (2) Fabrication of the solid electrolyte layer

[0130] The Li6PS5Cl thiargyrite-type solid electrolyte was added to an isobutylyl isobutylate binder solution (solid content: 50 wt%) of an acrylate polymer to which butyl acrylate was added, and then mixed. Here, the solid electrolyte and the binder were mixed at a weight ratio of 98.7:1.3.

[0131] The mixing process is carried out using a Thinky mixer. Subsequently, 2 mm zirconia balls are added to the obtained mixture, and then the mixture is stirred again using the Thinky mixer to prepare a slurry. The slurry is cast on a polytetrafluoroethylene release film and then dried at room temperature to fabricate a 100 μm thick solid electrolyte layer.

[0132] (3) Fabrication of the positive electrode

[0133] The positive electrode active material (LiNi 0.9 Mn 0.05 Co 0.05 O2) coated with LZO (Li-doped zinc oxide), argyrodite type solid electrolyte Li6PS5Cl, conductive carbon nanofibers, and a polytetrafluoroethylene binder are mixed at a weight ratio of 85:15:3:1.5 to prepare a mixture.

[0134] The prepared mixture is coated on an aluminum foil current collector and then vacuum dried at 45 °C to prepare a positive electrode including a 160 μm thick positive electrode active material layer and a 10 μm thick current collector. The thickness of the positive electrode active material layer is 12 μm.

[0135] (4) Fabrication of the all-solid-state full cell single body

[0136] The fabricated negative electrode, solid electrolyte, and counter electrode are sequentially stacked in the form of the positive electrode and the counter electrode, and a pressure of 8 MPa is applied to fabricate the all-solid-state cell single body.

[0137] (Comparative Example 1)

[0138] Carbon black and Ag are mechanically mixed at a weight ratio of 75:25 using a mortar to prepare a negative electrode coating composition. In the prepared negative electrode coating composition, the amount of silver is 25 wt% and the amount of carbon black is 75 wt%.

[0139] Except for using this negative electrode coating composition, the negative electrode and the all-solid-state cell single body are fabricated in the same manner as in Example 1.

[0140] (Comparative Example 2)

[0141] Carbon black and 2-naphthalenethiol powder are mixed at a weight ratio of 10:1. The mixture is heat-treated at 90 °C. AgNO3 and NaBH4 reducing agents are added to the heat-treated product in an aqueous solvent to prepare a loaded product. Here, based on the total weight of Ag and carbon black in the loaded product of 100 wt%, AgNO3 is used in an amount of 11 wt%. Additionally, based on 100 wt% of AgNO3, the amount of the NaBH4 reducing agent used is 22 wt%.

[0142] In addition to using the obtained product as a negative electrode coating composition, a negative electrode and an all-solid-state battery cell were fabricated in the same manner as in Example 1.

[0143] (Comparative Example 3)

[0144] 50 mL of glycerol (99.9%, Aldrich) and 0.5 mm of polyvinylpyrrolidone (weight-average molecular weight (Mw): 55,000, Aldrich) were added to a 100 mL reaction vessel and heated to 80 °C. The resulting materials were mixed until a transparent solution was formed and then cooled to 30 °C. Next, 5 g of carbon black was added to the reaction mixture and mixed for 10 minutes, and then 50 mM of AgNO3 (99.9%, Aldrich) was added and mixed for 5 minutes. The temperature of the mixture was raised to 100 °C and reacted for 12 hours.

[0145] Next, 50 mL of deionized water (DI water) was added to the reaction product, and sonication was performed for 2 minutes. Next, glycerol and polyvinylpyrrolidone were separated from the carbon black using a glass filter, and the silver-loaded carbon black was rinsed with ethanol and deionized water (DI water) to remove any residual components.

[0146] The rinsed product was placed in a vacuum oven and dried at 90 °C for more than 8 hours to prepare a negative electrode coating composition. In the negative electrode coating composition, the silver content was 5 wt% and the carbon content was 95 wt%.

[0147] In addition to using this negative electrode coating composition, a negative electrode and an all-solid-state battery cell were fabricated in the same manner as in Example 1.

[0148] (Comparative Example 4)

[0149] In addition to using only carbon black as the negative electrode coating composition, a negative electrode and an all-solid-state battery cell were fabricated in the same manner as in Example 1.

[0150] Experimental Example 1) SEM Photograph

[0151] The SEM images of the negative electrode coating compositions prepared in Example 1 and Comparative Example 1 are shown in Figure 3 and Figure 4 respectively.

[0152] As shown in Figure 3 , it can be seen that the negative electrode coating composition prepared according to Example 1 has silver uniformly dispersed in carbon black. On the other hand, as shown in Figure 4 , the negative electrode coating composition prepared according to Comparative Example 1 shows silver agglomeration in some regions on the surface.

[0153] Experimental Example 2) Evaluation of X-ray Photoelectron Spectroscopy (XPS)

[0154] XPS S2p spectra of the negative electrode coating compositions prepared according to Example 1, Comparative Example 1, and Comparative Example 2 were measured. The results are shown in Figure 5 . As shown in Figure 5 , in the case of Comparative Example 1 where carbon black and Ag were simply mixed, no Ag-S bond and C-S bond were present, while in the case of Example 1 where carbon black and Ag were chemically bonded through S, an Ag-S bond was present. In addition, in the case of Comparative Example 2 where heat treatment at 400 °C was not performed, it was found that C-S bonds, S-S bonds, and Ag-S bonds were all present.

[0155] Experimental Example 3) Evaluation of Resistivity Density

[0156] The resistances of the all-solid-state battery cells of Example 1 and Comparative Examples 1 to 3 were measured using a powder conductivity measurement method. The measurement results are shown in Table 1.

[0157] (Table 1)

[0158]

[0159]

[0160] As shown in Table 1, the resistance value of Comparative Example 3 in which silver and oxygen are bonded is much higher than that of Example 1. In particular, the resistance value of Comparative Example 3 is higher than that of Comparative Example 2 in which no bond is formed between sulfur and metal due to heat treatment.

[0161] Even in the case of Comparative Example 2 where no bond is formed between sulfur and metal, a high resistance value is shown, indicating deteriorated rate performance.

[0162] In addition, in Example 1 in which a bond between silver and sulfur is formed by heat treatment, carbon black is uniformly distributed, and the current is uniformly distributed in the negative electrode, and the resistance value after heat treatment is very low.

[0163] In addition, the resistance value after heat treatment of Example 1 is smaller than that of Comparative Example 1 in which carbon black and Ag are simply mixed.

[0164] Experimental Example 4) Thermogravimetric Analysis (TGA)

[0165] In the process for preparing the negative electrode coating composition of Example 1, thermogravimetric analysis (TGA) measurements were performed on the product before heat treatment and the negative electrode coating composition after heat treatment. In the results, the weight % change results are shown in Figure 6 , and the DTG (derivative thermogravimetry, % / min) values are shown in Figure 7It is shown in. The thermogravimetric analysis measurement method is carried out under an argon atmosphere and measured from room temperature (25 °C) to 900 °C (heating up to 900 °C at a rate of 10 °C per minute) under a N2 atmosphere at a heating rate of 10 °C per minute.

[0166] As shown in Figure 6 and Figure 7 As shown in, the product before heat treatment has a weight loss of 8.9 wt%, while the negative electrode coating composition after heat treatment has no weight loss. This weight loss is considered to be caused by the thiol compound, so the thiol compound present before heat treatment hardly remains after heat treatment.

[0167] Although the present disclosure has been described in connection with exemplary embodiments that are presently considered to be practical, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims.

Claims

1. A negative electrode coating composition for an all-solid-state battery, comprising a metal and a carbonaceous material, wherein the metal and the carbonaceous material are chemically bonded by sulfur.

2. The negative electrode coating composition for an all-solid-state battery according to claim 1, wherein in the spectrum obtained by XPS analysis, the negative electrode coating composition has a peak related to a metal-sulfur bond.

3. The negative electrode coating composition for an all-solid-state battery according to claim 1, wherein in the S2p spectrum obtained by XPS analysis, the negative electrode coating composition has a peak appearing at a binding energy of 160 eV to 162 eV.

4. The negative electrode coating composition for an all-solid-state battery according to claim 1, wherein the carbonaceous material is amorphous carbon, crystalline carbon, or a mixture thereof.

5. The negative electrode coating composition for an all-solid-state battery according to claim 1, wherein the metal is Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd, or a combination thereof.

6. The negative electrode coating composition for an all-solid-state battery according to claim 1, wherein based on the total amount of 100 wt% of the metal and the carbonaceous material, the amount of the metal is 3 wt% to 40 wt%.

7. A method for preparing a negative electrode coating composition for an all-solid-state battery, comprising mixing a carbonaceous material and a sulfur raw material to prepare a mixture; loading a metal onto the mixture to prepare a loaded product; and performing heat treatment on the loaded product.

8. The method for preparing a negative electrode coating composition for an all-solid-state battery according to claim 7, wherein the sulfur raw material is a thiol compound, a sulfide compound, a thiophene compound, a sulfonic acid, a sulfone, a sulfoxide, or a combination thereof.

9. The method for preparing a negative electrode coating composition for an all-solid-state battery according to claim 7, wherein the heat treatment is performed at 100 °C to 500 °C.

10. An all-solid-state battery, comprising a negative electrode, comprising a current collector and a negative electrode coating on one surface of the current collector; a positive electrode; and a solid electrolyte layer between the negative electrode and the positive electrode, wherein the negative electrode coating comprises the negative electrode coating composition according to any one of claims 1 to 6.

11. The all-solid-state battery according to claim 10, wherein the solid electrolyte is a sulfide-based solid electrolyte.

12. The all-solid-state battery according to claim 10, wherein the all-solid-state battery comprises a lithium-containing layer formed between the current collector and the negative electrode coating during initial charging.

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