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

Abstract

Disclosed are a negative electrode coating for an all-solid-state battery and an all-solid-state battery including the same, the negative electrode for an all-solid-state battery including a current collector and a negative electrode coating on the current collector, in which the negative electrode coating includes a first region adjacent to the current collector and a second region not adjacent to the current collector, the first and second regions contain a metal sulfide, and the metal sulfide content in the second region is greater than in the first region.

Description

Technical Field

[0001] A negative electrode for an all-solid-state battery and an all-solid-state battery including the same are disclosed. Background Technology

[0002] Recently, there has been rapid development in battery-powered electronic devices such as mobile phones, laptops, and electric vehicles.

[0003] These battery characteristics have recently led to a demand for higher energy density and superior safety.

[0004] Therefore, the development of all-solid-state batteries using lithium metal as the negative electrode is underway. All-solid-state batteries are batteries composed entirely of solid materials, particularly using solid electrolytes. Lithium metal exhibits a high average voltage due to its large potential difference with the positive electrode, and can achieve a high energy density with a theoretical capacity of approximately 3860 mAh / g. Furthermore, solid electrolytes ensure safety due to their low fire risk. Summary of the Invention

[0005] Technical issues

[0006] One embodiment provides a negative electrode for an all-solid-state battery that exhibits excellent lithium-ion conductivity, improved rate performance and cycle life characteristics, and reduced overvoltage, as well as improved efficiency and output characteristics.

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

[0008] Technical solution

[0009] One embodiment provides a negative electrode for an all-solid-state battery, comprising a current collector and a negative electrode coating on the current collector, wherein the negative electrode coating comprises a first region adjacent to the current collector and a second region not adjacent to the current collector, the first region and the second region comprising metal sulfides, and the amount of metal sulfides in the second region being greater than the amount of metal sulfides in the first region.

[0010] The first region may be an area corresponding to 80% to 20% of the total thickness of the negative electrode coating.

[0011] The second region may be an area corresponding to 80% to 20% of the total thickness of the negative electrode coating.

[0012] The amount of the metal sulfide included in the second region may be 99 to 1.5 times the amount of the metal sulfide included in the first region.

[0013] The amount of the metal sulfide may be from 1% to 50% by weight, based on 100% by weight of the total negative electrode coating.

[0014] Based on 100% by weight of the total first region, the amount of the metal sulfide included in the first region may be from 40% by weight to 1% by weight.

[0015] Based on 100% by weight of the total second region, the amount of the metal sulfide included in the second region may be from 99% by weight to 2% by weight.

[0016] The metal sulfide may be Li₂S, Ag₂S, Au₂S, Al₃S₂, ​​Na₂S, NiS, Ti₂S, SnS, ZnS, CdS, MoS₂, FeS, Cu₂S, CuFeS₂, or a combination thereof. In embodiments, the metal sulfide may include Li₂S, and may further include Ag₂S, Au₂S, Al₃S₂, ​​Na₂S, NiS, Ti₂S, SnS, ZnS, CdS, MoS₂, FeS, Cu₂S, CuFeS₂, or a combination thereof.

[0017] The end (terminal) portions of the first region and the second region may further include Ag2S, Au2S, Al3S2, Na2S, NiS, Ti2S, SnS, ZnS, CdS, MoS2, FeS, Cu2S, CuFeS2, or combinations thereof.

[0018] The end portion may correspond to 90% to 10% of the total length of the negative electrode coating in the longitudinal direction of the current collector.

[0019] The negative electrode coating may include carbon-based materials and metals.

[0020] The carbon-based material may be amorphous carbon, crystalline carbon, or a mixture thereof.

[0021] The metal may be Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd, or a combination thereof.

[0022] Another embodiment provides an all-solid-state battery, which includes: the negative electrode; the positive electrode; and a solid electrolyte layer between the negative electrode and the positive electrode.

[0023] The solid electrolyte may be a sulfide-based solid electrolyte (sulfide-based solid electrolyte, sulfide-based solid electrolyte).

[0024] The all-solid-state battery may further include a lithium-containing layer formed between the current collector and the negative electrode coating during initial charging.

[0025] The all-solid-state battery undergoes charging and discharging.

[0026] Beneficial effects

[0027] The negative electrode for all-solid-state batteries according to the embodiments exhibits excellent lithium-ion conductivity as well as improved rate performance and cycle life characteristics. Furthermore, the negative electrode for all-solid-state batteries according to the embodiments can reduce overvoltage and improve efficiency and output characteristics. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a negative electrode for an all-solid-state battery according to an embodiment.

[0029] Figure 2 This is a diagram illustrating the end portion of the negative electrode for an all-solid-state battery according to an embodiment.

[0030] Figure 3 This is a schematic cross-sectional view of an all-solid-state battery according to one embodiment.

[0031] Figure 4 This is a schematic cross-sectional view of an all-solid-state battery according to another embodiment. Detailed Implementation

[0032] Embodiments of the present invention will be described in detail below. However, these embodiments are merely examples, and the present invention is not limited thereto, and is defined by the scope of the claims.

[0033] The terminology used herein is for descriptive purposes only and is not intended to limit the invention. Unless the context clearly specifies otherwise, singular expressions include plural expressions.

[0034] "Combinations" refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0035] Here, the terms “comprising,” “including,” or “having” are intended to specify the presence of the performed feature, number, step, constituent element (component), or combination thereof, but it should be understood that the possibility of the presence or addition of one or more other features, numbers, steps, constituent elements (components), or combinations is not excluded in advance.

[0036] Throughout the specification, whenever it is said that a section “includes” a component, this does not exclude other components, but rather includes them, unless otherwise specifically stated.

[0037] Furthermore, the terms “about,” “substantially,” etc., used throughout this application are used in a meaning close to numerical when they are numerical or when presented with manufacturing and material tolerances inherent in the stated meaning, and are intended to prevent unethical infringers from unfairly using the precise or absolute values ​​mentioned herein to aid in understanding the disclosure of this application.

[0038] Throughout the instruction manual, references to "A and / or B" mean "A or B or both".

[0039] 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 may be directly on said other element or there may be an intermediate element present.

[0040] In this specification, "particle size" or "particle diameter" may refer to the average particle diameter. Alternatively, the average particle diameter may be defined as the average particle diameter (D50) based on 50% of the cumulative volume in a cumulative size distribution curve. Particle diameter can be measured using methods widely known to those skilled in the art, for example, by using a particle size analyzer, transmission electron microscope, scanning electron microscope, or field emission scanning electron microscope (FE-SEM). Alternatively, the average particle diameter (D50) can be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles in each particle size range, and thus calculating, or by measuring using a laser diffraction method. It can be measured by laser diffraction as follows: 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., the MT3000 from Microtrac) to irradiate with ultrasound at an output of 60W at approximately 28 kHz, and the average particle diameter (D50) of the particle size distribution referenced in the measuring device can be calculated.

[0041] "Thickness" can be measured, for example, from photographs taken with an optical microscope such as a scanning electron microscope.

[0042] The embodiments involve a negative electrode for an all-solid-state battery, including a negative electrode coating.

[0043] In this embodiment, the negative electrode coating refers to a layer that facilitates the movement of lithium ions, which are extracted from the positive electrode active material, to the negative electrode and deposit on the surface of the current collector during charging and discharging of the all-solid-state battery. That is, a lithium deposit layer is formed between the current collector and the negative electrode coating due to the deposition of lithium ions, and this lithium deposit layer acts as the negative electrode active material; such a negative electrode is generally referred to as a deposited negative electrode. Metals and amorphous carbon included in the negative electrode coating do not act as negative electrode active materials directly involved in the charging and discharging reactions. This deposited negative electrode means a negative electrode that does not include negative electrode active material during battery assembly, but in which the lithium deposit layer acts as the negative electrode active material.

[0044] The negative electrode includes a current collector and a negative electrode coating on one surface of the current collector. In one embodiment, the negative electrode coating includes a first region adjacent to the current collector and a second region not adjacent to the current collector, defined in the thickness direction.

[0045] Reference Figure 1 The negative electrode 1 includes a current collector 3 and a negative electrode coating 5, and includes a first region 5a adjacent to the current collector 3 and a second region 5b not adjacent to the current collector 3.

[0046] In this embodiment, the first region may correspond to 80% to 20% of the total thickness of the negative electrode coating, or it may correspond to 75% to 25% or 60% to 40%. Similarly, the second region may correspond to 80% to 20% of the total thickness of the negative electrode coating, or it may correspond to 25% to 75% or 40% to 60%. That is, in this embodiment, the negative electrode coating is composed of a first region and a second region, and if the total thickness of the negative electrode coating is 100%, then when the first region is 20%, the second region corresponds to 80%.

[0047] Reference Figure 1 , corresponding to Figure 1 The first region 'a' shown corresponds to 80% to 20% of the total thickness (h) of the negative electrode coating.

[0048] In this embodiment, both the first region and the second region may include metal sulfides, and specifically, the amount of metal sulfides in the second region may be greater than the amount of metal sulfides in the first region. Specifically, the amount of metal sulfides included in the second region may be 99 to 1.5 times, or 50 to 3 times, the amount of metal sulfides included in the first region. For example, if the amount of metal sulfides included in the first region is 1% by weight based on 100% of the total negative electrode coating, and the amount of metal sulfides included in the second region is 5% by weight based on 100% of the total negative electrode coating, then the amount of metal sulfides included in the second region is five times the amount included in the first region.

[0049] Thus, when both the first and second regions of the negative electrode coating contain metal sulfides, and the amount of metal sulfides in the second region (in contact with the electrolyte) is greater than in the first region (in contact with the current collector), lithium ions released from the positive electrode active material and moving to the negative electrode coating can more easily embed into the negative electrode coating. This enhanced lithium-ion embedding effect is because metal sulfides are lithiophilic materials that react with lithium ions to form Li₂S, which lowers the energy barrier for lithium ions and has high lithium-ion conductivity. Furthermore, lithium ions can easily move to the negative electrode current collector, enabling more stable lithium-ion movement and allowing for more uniform accumulation and growth of lithium ions between the current collector and the negative electrode coating.

[0050] In embodiments, the metal sulfide may be Li2S, Ag2S, Au2S, Al3S2, Na2S, NiS, Ti2S, SnS, ZnS, CdS, MoS2, FeS, Cu2S, CuFeS2, or a combination thereof.

[0051] Metal sulfides (such as Li2S) can also act as an artificial SEI layer (protective layer), and when included in excess in the second region in contact with the electrolyte, they exhibit excellent affinity in the region in contact with the electrolyte (e.g., sulfur in sulfide electrolytes), thereby improving cycle life.

[0052] Thus, the appropriate effect of including metal sulfides in the negative electrode coating can be obtained by controlling the amount of metal sulfides depending on the location of the negative electrode coating.

[0053] If the metal sulfide is present in excess in the first region (i.e., in a larger amount than in the second region), the lithium-ion energy barrier in the second region, where lithium ions first intercalate and come into contact with the electrolyte, is not sufficiently reduced, and therefore the desired effect cannot be obtained. Furthermore, when the metal sulfide is uniformly distributed in both the first and second regions, the effect obtained when the metal sulfide is present in the second region can be relatively reduced, making it impossible to obtain a sufficient effect.

[0054] In this embodiment, the amount of metal sulfide included in the first region, based on 100% by weight of the total first region, can be 80% to 20% by weight, or 60% to 40% by weight. Additionally, the amount of metal sulfide included in the second region, based on 100% by weight of the total second region, can be 80% to 20% by weight, or 60% to 40% by weight. When the amount of metal sulfide included in the first and second regions is within the above ranges, and the amount of metal sulfide included in the second region is greater than the amount of metal sulfide included in the first region, the affinity can be further improved at the boundary with the sulfide-based electrolyte, thereby further increasing the effect of lowering the lithium-ion energy barrier.

[0055] The metal sulfides included in the first and second regions may be present in powder form.

[0056] In an embodiment, the amount of metal sulfide may be from 1% to 50% by weight, based on 100% by weight of the total negative electrode coating.

[0057] In one embodiment, the negative electrode coating comprises Li₂S and may further comprise Ag₂S, Au₂S, Al₃S₂, ​​Na₂S, NiS, Ti₂S, SnS, ZnS, CdS, MoS₂, FeS, Cu₂S, CuFeS₂, or combinations thereof. When the negative electrode coating, together with Li₂S, further comprises Ag₂S, Au₂S, Al₃S₂, ​​Na₂S, NiS, Ti₂S, SnS, ZnS, CdS, MoS₂, FeS, Cu₂S, CuFeS₂, or combinations thereof, the sulfur contained in these compounds can react with lithium ions to form Li₂S. Therefore, the affinity for sulfide electrolytes due to the inclusion of Li₂S can be further improved, thereby further improving battery performance.

[0058] In another embodiment, Ag₂S, Au₂S, Al₃S₂, ​​Na₂S, NiS, Ti₂S, SnS, ZnS, CdS, MoS₂, FeS, Cu₂S, CuFeS₂, or combinations thereof may be included in specific regions of the negative electrode coating, for example, at the end portions of the first and second regions. The end portion means the end in the longitudinal direction of the current collector, and this end portion means... Figure 2 The C region is shown in the diagram. Additionally, the end portion can be an end in the longitudinal direction.

[0059] For example, the end portion may correspond to 90% to 10% of the total length of the negative electrode coating in the longitudinal direction of the current collector, or it may correspond to 80% to 20% of it.

[0060] The negative electrode coating may include carbon-based materials and metals. Carbon-based materials and metals can act as catalysts. In the negative electrode coating, for example, metals may be supported on carbon-based materials, or a mixture of metals and carbon-based materials may exist.

[0061] Carbon-based materials can be amorphous carbon, crystalline carbon, or mixtures thereof. Amorphous carbon can be, for example, carbon black, acetylene black, acetylene carbon black (Denca black), Ketjen black, furnace black, activated carbon, or combinations thereof. An example of carbon black is Super P (Timcal). Amorphous carbon is not limited to this, and of course any material classified as amorphous carbon in the relevant field can be used. Crystalline carbon can be natural graphite, artificial graphite, carbon nanotubes, mesophase carbon microspheres, graphene, or combinations thereof. Crystalline carbon can be amorphous, plate-like, flake-like, spherical, or fibrous.

[0062] In embodiments, the carbon-based material may be a single particle or an aggregate of secondary particles having primary particles aggregated therein. When the carbon-based material is a single particle, the size of the carbon-based material may be nanoscale, having an average particle size of less than or equal to 100 nm, for example, 10 nm to 100 nm.

[0063] In addition, when the carbon-based material is a granular material, the primary particles can have a particle size of 20 nm to 100 nm, and the secondary particles can have a particle size of 1 μm to 20 μm.

[0064] In an embodiment, the particle size of a primary particle may 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.

[0065] In the embodiments, the particle size of the secondary particles may 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.

[0066] The shape of the primary particles can be spherical, elliptical, plate-shaped, or a combination thereof, and in the embodiments, the shape of the primary particles can be spherical, elliptical, or a combination thereof.

[0067] The metal can be Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd, or combinations thereof. Because the negative electrode coating includes the aforementioned metal, the conductivity of the negative electrode can be further improved.

[0068] The metal can be in the form of nanoparticles, and the average size of the metal nanoparticles can be, for example, from 5 nm to 80 nm, but nano-sized particles can be used appropriately. By using metal nanoparticles with such nano-sized particles, the battery characteristics (e.g., cycle life characteristics) of all-solid-state batteries can be improved. As the metal particle size increases in micrometers, the uniformity of the metal particles in the negative electrode coating can decrease, the current density in a particular region can increase, and the cycle life characteristics can deteriorate.

[0069] In the negative electrode coating, carbon-based materials and metals may be included in both the first and second regions. The carbon-based materials and metals may be the same or different in the first and second regions.

[0070] Based on 100% by weight of the total negative electrode coating, the amount of metal can be from 1% to 50% by weight, 2% to 30% by weight, 2% to 25% by weight, 2% to 20% by weight, or 2% to 15% by weight. The amount of metal is the total amount of metal included in the first and second regions of the negative electrode coating, and the amount of metal in each of the first and second regions is not limited. For example, the metal can be present in the same amount in the first region and the second region, or it can be present in different amounts.

[0071] Additionally, based on 100% by weight of the total negative electrode coating, the carbon-based material may be present in amounts ranging from 1% to 99% by weight, 70% to 97% by weight, 75% to 96% by weight, 80% to 95% by weight, or 85% to 95% by weight. The amount of carbon-based material is the amount of the total metal included in the first and second regions of the negative electrode coating, and the amount of carbon-based material in each of the first and second regions is not limited. For example, the carbon-based material may be present in the same amount, or it may be present in different amounts in the first and second regions.

[0072] The negative electrode coating may further include an adhesive. In the negative electrode coating, the adhesive may be present in both the first and second regions. The adhesive may be the same or different in the first and second regions.

[0073] The adhesive may be a water-insoluble adhesive.

[0074] Water-insoluble adhesives may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinylidene fluoride, polymers containing ethylene oxide (ethylene oxide), ethylene propylene copolymers, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, polyacrylate, or combinations thereof.

[0075] Based on 100% by weight of the total negative electrode coating, the adhesive may be included in an amount from 1% to 15% by weight. For example, based on 100% by weight of the total negative electrode coating, the adhesive may be included in an amount greater than or equal to 1% by weight, greater than or equal to 2% by weight, greater than or equal to 3% by weight, greater than or equal to 4% by weight, greater than or equal to 5% by weight, greater than or equal to 6% by weight, greater than or equal to 7% by weight, greater than or equal to 8% by weight, greater than or equal to 9% by weight, greater than or equal to 10% by weight, greater than or equal to 11% by weight, greater than or equal to 12% by weight, greater than or equal to 13% by weight, or greater than or equal to 14% by weight, and less than or equal to 15% by weight, less than or equal to 14% by weight, less than or equal to 13% by weight, less than or equal to 12% by weight, less than or equal to 11% by weight, less than or equal to 10% by weight, less than or equal to 9% by weight, less than or equal to 8% by weight, less than or equal to 7% by weight, less than or equal to 6% by weight, less than or equal to 5% by weight, less than or equal to 4% by weight, less than or equal to 3% by weight, or less than or equal to 2% by weight.

[0076] The amount of adhesive is the amount of total metal included in the first and second regions of the negative electrode coating, and there is no need to limit the amount of adhesive in each of the first and second regions. For example, the amount of adhesive in the first and second regions may be the same or different.

[0077] When an adhesive is included in the negative electrode coating of an all-solid-state battery within the above-mentioned range, the resistance and adhesive strength can be improved, thereby improving the characteristics of the all-solid-state battery (battery capacity and output characteristics).

[0078] In one embodiment, the negative electrode coating may further include a solid electrolyte. The solid electrolyte may be present in both the first and second regions of the negative electrode coating. The solid electrolyte may be the same or different in the first and second regions.

[0079] In this embodiment, based on 100% by weight of the total negative electrode coating, the amount of solid electrolyte can be greater than 0% by weight and less than or equal to 30% by weight, and can be from 10% by weight to 20% by weight. The amount of solid electrolyte is the amount of total metal included in the first and second regions of the negative electrode coating, and the amount of solid electrolyte in each of the first and second regions is not limited. For example, the solid electrolyte can be present in the first and second regions in the same amount or in different amounts.

[0080] The solid electrolyte can be a sulfide-based solid electrolyte. Because the negative electrode coating according to the embodiment contains a metal sulfide, using a sulfide-based solid electrolyte as the solid electrolyte included in the solid electrolyte layer has the following advantages compared to oxide-based solid electrolytes, halide-based solid electrolytes, or solid polymer electrolytes: a rapid lithium-ion migration effect due to the high affinity between sulfur included in the metal sulfide and sulfur included in the sulfide-based solid electrolyte.

[0081] In embodiments, the sulfide-based solid electrolyte may be, for example, 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, or Li2S-P2S5-Z. m S n (m and n are integers 0 or greater 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 an integer greater than 0 and less than 12, 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 an integer of 0 or greater and 12 or less, M is Ge, Sn, Si, or a combination thereof, and A is one of F, Cl, Br, or I). Sulfide solid electrolytes can 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 PS 6-x Br x (0≤x≤2), or Li 7-x PS 6-x I x (0≤x≤2). Additionally, it can specifically be Li3PS4 or 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 wait.

[0082] In this embodiment, the sulfide solid electrolyte can be a sulfide solid electrolyte of the argyrocerium sulfide type. The sulfide solid electrolyte of the argyrocerium sulfide type can be, for example, Li... a M b P c S d A e (where a, b, c, d, and e are all 0 or greater and 12 or less, M is Ge, Sn, Si, or a combination thereof, and A is F, Cl, Br, or I), and in particular, 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 wait.

[0083] Sulfide solid electrolytes can be amorphous, crystalline, or a mixture thereof. Sulfide solid electrolytes 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 these mixing ratio ranges, sulfide solid electrolytes with excellent ionic conductivity can be prepared. Ionic conductivity can be further improved by adding SiS₂, GeS₂, B₂S₃, etc., as other components. Mechanical milling or solution methods can be used as mixing methods. Mechanical milling involves placing the starting material, ball mill, etc., into a reactor and vigorously stirring them to form particles from the starting material. Solution methods can be carried out by mixing the starting material in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, additional calcination can be performed after mixing. If additional calcination is performed, the crystals of the solid electrolyte can become more robust.

[0084] Of course, commercially available solid electrolytes can be used as sulfide-based solid electrolytes.

[0085] The negative electrode coating may further include additives such as fillers and dispersants. Additionally, known materials commonly used in all-solid-state batteries can be used as fillers, dispersants, etc., that may be included in the negative electrode coating.

[0086] The thickness of the negative electrode coating can range from 1 μm to 20 μm. For example, the thickness of the negative electrode coating can be greater than or equal to 1 μm, greater than or equal to 3 μm, or greater than or equal to 5 μm, and less than or equal to 20 μm, less than or equal to 18 μm, less than or equal to 16 μm, less than or equal to 14 μm, less than or equal to 12 μm, or less than or equal to 10 μm.

[0087] The 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 alloys thereof, and may be in the form of 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.

[0088] The current collector may include a metal substrate and may further include a thin film formed on the substrate. The thin film may include elements that can form an alloy with lithium, and may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, or combinations thereof, but is not limited thereto, and may use any element in the art that can form an alloy with lithium. When the current collector further includes a thin film and a lithium-containing layer is formed by deposition during charging, a flatter lithium-containing layer can be formed, thereby further improving the cycle life of the all-solid-state battery.

[0089] The thickness of the film can be 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. When the film thickness is within the above range, the cycle life characteristics can be further improved.

[0090] According to an embodiment, the negative electrode can be obtained through a preparation process in which the coating process for forming the negative electrode coating is performed two or more times. For example, a negative electrode coating composition to which a metal sulfide precursor is added can be used to form the negative electrode coating.

[0091] An example of performing the coating process twice is shown below.

[0092] The first regional composition is prepared by mixing carbonaceous material, metal, metal sulfide precursor and binder in a solvent. Here, the mixing ratio of carbonaceous material, metal, precursor and binder can be from 98:1:1 to 30:60:10.

[0093] Alternatively, a second regional composition is prepared by mixing a carbon-based material, a metal, a metal sulfide precursor, and a binder in a solvent. Here, the mixing ratio of the carbon-based material, the metal, the precursor, and the binder can be from 98:1:1 to 45:45:10.

[0094] Here, in both the first and second region compositions, the amount of precursor included in the second region composition can be adjusted to be greater than the amount of precursor included in the first region composition. For example, the amount of precursor included in the second region composition can be adjusted to be 1.5 to 99 times the amount of precursor included in the first region composition. When the amounts of precursor included in the first and second region compositions are within the above range, the amount of metal sulfide included in the second region of the manufactured final negative electrode can be 1.5 to 99 times the amount of metal sulfide included in the first region.

[0095] The carbon-based material can be amorphous carbon or crystalline carbon as described above. The metal can be any of the aforementioned metals.

[0096] The metal sulfide precursor may be Ag₂S, Au₂S, Al₃S₂, ​​Na₂S, NiS, Ti₂S, SnS, ZnS, CdS, MoS₂, FeS, Cu₂S, CuFeS₂, or a combination thereof. The binder may be one of the above-mentioned binders. The solvent may be N-methylpyrrolidone (NMP), benzene, hexane, tetrahydrofuran (THF), ethanol, isopropanol (IPA), DMSO, DMF, AN, or a combination thereof.

[0097] The first region composition is coated onto the current collector and dried to form the first region. Next, the second region composition is coated onto the first region and dried to form the second region.

[0098] When the coating process is performed three or more times, three or more compositions, such as three to six compositions, with different amounts of metal sulfide precursors can be prepared and executed. Here, the coating process can be carried out by: preparing a first composition, which includes the metal sulfide precursor in an amount of 1% to 45% by weight based on 100% by weight of the total composition, and then gradually increasing the amount of metal sulfide precursor in the second, third, ... nth compositions by 5% to 60% by weight. For example, the coating process can be carried out by applying a first composition with a minimum amount of metal sulfide precursor, and then applying compositions with correspondingly larger amounts of metal sulfide precursor.

[0099] Regardless of the number of coating processes, the drying process can be carried out using vacuum drying. This drying process can be performed at temperatures ranging from 20°C to 100°C.

[0100] If an all-solid-state battery including such a negative electrode is charged and discharged, the metal sulfide, such as Li2S, is retained in the negative electrode coating because the metal sulfide included in the negative electrode coating reacts with lithium moving from the positive electrode active material to form a metal sulfide, such as Li2S. Furthermore, because the second coating composition forming the second region includes a metal sulfide precursor in a larger amount than the first coating composition, after charging and discharging, the metal sulfide, such as Li2S, can be retained in the second region of the negative electrode coating more than in its first region. Even if the coating process is performed three or more times, because the coating process is performed by increasing the amount of the metal sulfide precursor, the metal sulfide, such as Li2S, can be retained in the second region more than in the first region.

[0101] The charging and discharging process can be carried out once to three times at 0.05 C to 0.1 C at 25°C to 60°C.

[0102] In addition, since the reaction can mainly occur in the central part of the positive electrode coating, the metal sulfide precursor (unreacted material) can be retained in the end part of the positive electrode coating, such as the two end parts.

[0103] Another embodiment provides an all-solid-state battery, which includes the negative electrode, the positive electrode, and a solid electrolyte layer between the negative electrode and the positive electrode.

[0104] The negative electrode according to the embodiment may further include a lithium-containing layer formed between the current collector and the negative electrode coating during initial charging after battery manufacturing. 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 suitably function as a lithium reservoir and can further improve its cycle life.

[0105] The lithium-containing layer can be formed after the battery is manufactured. During charging, lithium ions are released from the positive electrode active material, pass through the solid electrolyte and move to the negative electrode, and as a result, lithium precipitates and deposits on the negative electrode current collector.

[0106] The charging process can be a formation process performed 1 to 3 times at 0.05 C to 1 C at 25°C to 50°C. If lithium is precipitated and deposited to form a lithium-containing layer, the lithium included in the lithium-containing layer is ionized and migrates to the positive electrode during discharge, so that the lithium can be used as the active material of the negative electrode.

[0107] In this implementation, because the lithium-containing layer exists between the current collector and the negative electrode coating, the negative electrode coating can serve 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 in the all-solid-state battery can be suppressed, and consequently, the cycle life of the all-solid-state battery can be improved.

[0108] The solid electrolyte layer includes a solid electrolyte. This solid electrolyte can be an inorganic solid electrolyte, such as a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, or a solid polymer electrolyte.

[0109] In this embodiment, the sulfide-based solid electrolyte is as described above.

[0110] Oxide-based solid electrolytes 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, 0≤y≤1), lithium lanthanum titanate (Li x La yTiO3, where 0 < x < 2 and 0 < y < 3), Li2O, LiAlO2, ceramics of the Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2 type (ceramics based on Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2), garnet - type ceramics (ceramics based on garnet) Li 3+x La3M2O 12 (M = Te, Nb, or Zr, and x is an integer from 1 to 10), or a mixture thereof.

[0111] Solid polymer electrolytes can include, for example, those selected from 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 、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 P3-y O 12 (0 < x ≤ 0.4, 0 < y ≤ 0.6, Q is Al or Ga), 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, A is Zn) or more than one kind.

[0112] 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 the above X. In addition, examples of M may include metal elements such as Sc, Y, B, Al, Ga, and In.

[0113] The composition of the halide solid electrolyte is not particularly limited, and it can 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). Here, a can be 0.75 or more, 1 or more, and a can be 1.5 or less. b can be 1 or more, and can be 2 or more. In addition, c can be 3 or more, and can be 4 or more. Specific examples of the halide solid electrolyte can be Li3YBr6, Li3YCl6, or Li3YBr2Cl4.

[0114] The solid electrolyte can be in the form of particles, and the average particle size (D50) can be less than or equal to 5.0 μm, such as 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.

[0115] The solid electrolyte layer may further include an adhesive. Here, the adhesive can be styrene-butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, acrylate polymer (acrylate-based polymer), or a combination thereof, but is not limited thereto, and any substance used as an adhesive in the art can be used. The acrylate polymer can be butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0116] A solid electrolyte layer can be formed by adding a solid electrolyte to an adhesive solution, coating it onto a base film, and drying the result. The solvent in the adhesive solution can be isobutyl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. The process for forming the solid electrolyte layer is well known in the art, and therefore its detailed description will be omitted.

[0117] The positive electrode includes a positive electrode current collector and a layer of positive electrode active material on at least one surface of the positive electrode current collector.

[0118] 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 inserting 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 combinations thereof. Examples of positive electrode active materials 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 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 B1 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 Mr 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 Mr 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 Mr 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 HAVE BEEN 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 e O2 (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 bO4 (0.90≤a≤1.8, 0.001≤b≤0.1); QO2; 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.

[0119] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; B 1 It is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof; D 1 It is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F 1 It 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 J 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 It is Mn, Al, or a combination thereof.

[0120] According to the embodiments, the positive electrode active material can be a ternary lithium transition metal oxide, 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)。

[0121] Furthermore, the compound may have a coating layer on its surface, or may be mixed with another compound having a coating layer. The coating layer may include at least one coating element compound selected from oxides, hydroxides, hydroxyoxides, oxycarbonates, and hydroxycarbonates of the coating element. The compound used for the coating layer may be amorphous or crystalline. The coating element 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 can be formed by using these elements in the compound in a manner that does not adversely affect the properties of the positive electrode active material, and 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 described in more detail here.

[0122] In addition, any known coating layer can be applied to the positive electrode active material of all-solid-state batteries, examples of which include Li2O-ZrO2 (LZO).

[0123] Furthermore, when 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 metal elution from the positive electrode active material during charging can be further reduced. Therefore, the long-term reliability and cycle characteristics of the all-solid-state battery can be further improved during charging.

[0124] Examples of the shape of the positive electrode active material include particle shapes such as spheres and ellipsoids. Furthermore, the average particle size of the positive electrode active material is not particularly limited and can be within the range applicable to existing all-solid-state rechargeable batteries. Additionally, the amount of positive electrode active material in the positive electrode active material layer is not particularly limited and can be within the range applicable to existing all-solid-state rechargeable battery positive electrode layers.

[0125] 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 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% to 30% by weight.

[0126] 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 alloys thereof, and may be in the form of foil or sheet.

[0127] The positive electrode active material layer may further include an adhesive and / or a conductive material.

[0128] Adhesives may include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-oxygen-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0129] Based on the total weight of the positive electrode active material layer, the binder may be included in an amount from 0.1 wt% to 5 wt%, or from 0.1 wt% to 3 wt%. Within the above range, the binder can sufficiently exhibit adhesive ability without degrading battery performance.

[0130] Conductive materials are used to impart conductivity to electrodes and can be any material that conducts electrons without causing chemical changes in a battery. Examples of conductive materials may include carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, and Ketjen black; carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials (including copper, nickel, aluminum, silver, etc., and in the form of metal powders or metal fibers); conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0131] Based on the total weight of the positive electrode active material layer, conductive material may be included in an amount from 0.1 wt% to 5 wt%, or from 0.1 wt% to 3 wt%. Within the above range, conductive material can improve conductivity without degrading battery performance.

[0132] The thickness of the positive electrode active material layer can be from 90 μm to 200 μm. For example, the thickness of the positive electrode active material layer can 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 can be 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.

[0133] In implementations, a buffer material may be additionally included to cushion thickness changes that occur during charging and discharging of the all-solid-state battery. The buffer material may be present between the negative electrode and the casing, and in the case of a battery in which one or more electrode assemblies are stacked, it may be present between different electrode assemblies.

[0134] Cushioning materials may include materials with an elastic recovery rate of 50% or greater and insulating properties, and particularly include silicone rubber, acrylic rubber, fluororubber, nylon, synthetic rubber, or combinations thereof. Cushioning materials may exist in the form of polymer sheets.

[0135] Figure 3 This is a cross-sectional view of an all-solid-state battery according to one embodiment. (Refer to...) Figure 3The all-solid-state battery 100 includes an electrode assembly and a housing, such as a bag, containing the electrode assembly. Stacked within the electrode assembly is a negative electrode 400 comprising a negative electrode current collector 401 and a negative electrode coating 403, a solid electrolyte layer 300, and a positive electrode 200 comprising a positive electrode active material layer 203 and a positive electrode current collector 201. The all-solid-state battery 100 may further include an elastic layer 500 on the exterior of at least one of the positive electrode 200 and the negative electrode 400. Although... Figure 3 The image shows an electrode assembly including a negative electrode 400, a solid electrolyte layer 300, and a positive electrode 200, but an all-solid-state battery can also be fabricated by stacking two or more electrode assemblies.

[0136] Figure 4 An all-solid-state battery according to another embodiment is shown schematically. Figure 4 The all-solid-state battery 100 shown includes: a positive electrode 200 comprising a positive electrode current collector 201 and a positive electrode active material layer 203; a negative electrode 400 comprising a negative electrode current collector 401 and a negative electrode coating 403; a solid electrolyte 300 between the positive electrode 200 and the negative electrode 400; a battery casing 500 containing the electrolyte; and a lithium deposit layer 405' between the negative electrode current collector 401 and the negative electrode coating 403. This lithium deposit layer can be formed during charging of the all-solid-state battery, where lithium ions are released from the positive electrode active material and deposited on the negative electrode current collector 401'.

[0137] According to the embodiments, the all-solid-state battery can be manufactured by placing a negative electrode, a positive electrode, and a solid electrolyte layer between the negative electrode and the positive electrode, preparing a stack, and pressing the stack.

[0138] The pressing process can be carried out in the range of 25°C to 90°C. Alternatively, the pressing process can be performed at a pressure of less than or equal to 550 MPa, for example, less than or equal to 500 MPa, or for example, from 1 MPa to 500 MPa. The pressing time can vary depending on the temperature and pressure, and can be, for example, less than 30 minutes. The pressing process can be, for example, isostatic pressing, roller pressing, plate pressing, or warm isostatic pressing (WIP).

[0139] Modes for implementing inventions

[0140] The following describes embodiments and comparative examples of the present invention. However, these embodiments are not to be construed as limiting the scope of the invention in any way.

[0141] Example 1

[0142] (1) Preparation of negative electrode

[0143] The first region composition was prepared by mixing carbon black (average particle size: 35 nm), Ag (average particle size: 60 nm), Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 90:2.5:0.5:7.

[0144] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 85:5.5:2.5:7.

[0145] After coating and drying a first region composition on a stainless steel foil serving as a current collector, a second region composition is coated thereon, and then vacuum dried at 80°C to prepare a negative electrode comprising a 12 μm thick negative electrode coating and a 10 μm thick current collector. Here, the first region has a thickness of 9 μm, and the second region has a thickness of 3 μm. Furthermore, the prepared negative electrode has 3.25 wt% Ag content based on 100 wt% of the total negative electrode coating, 88.75 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 7 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the amount of AgS is 1 wt% based on 100 wt% of the total negative electrode coating.

[0146] (2) Preparation of solid electrolyte layer

[0147] An isobutyl isobutyrate binder solution (solid content: 50 wt%) was added to a Li6PS5Cl silver-germanium sulfide-type solid electrolyte, and then mixed. The isobutyl isobutyrate binder solution was prepared by adding acrylate polymers containing butyl acrylate. Here, the solid electrolyte and binder were mixed at a weight ratio of 98.7:1.3.

[0148] The mixing process was carried out using a thinky mixer. Subsequently, 2 mm zirconia balls were added to the resulting mixture, and then the mixture was stirred again using the thinky mixer to prepare a slurry. The slurry was cast onto a polytetrafluoroethylene release film and then dried at room temperature to create a 100 μm thick solid electrolyte layer.

[0149] (3) Manufacturing of all-solid-state half-cells

[0150] The negative electrode, solid electrolyte, and lithium metal counter electrode are stacked sequentially and then pressed with a pressure of 8 MPa to manufacture an all-solid-state battery.

[0151] Example 2

[0152] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 87:2:4:7.

[0153] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 79:2:12:7.

[0154] A negative electrode for an all-solid-state battery is prepared by using the first region composition and the second region composition, in addition to the other two methods. Here, the formed negative electrode coating has a thickness of 12 μm, the first region has a thickness of 3 μm, and the second region has a thickness of 9 μm. Furthermore, the prepared negative electrode has 2 wt% Ag based on 100 wt% of the total negative electrode coating, 81 wt% carbon black based on 100 wt% of the total negative electrode coating, and 7 wt% binder based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 10 wt% based on 100 wt% of the total negative electrode coating.

[0155] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0156] Example 3

[0157] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 88:5:10:7.

[0158] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 58:5:30:7.

[0159] A negative electrode for an all-solid-state battery is prepared by using the first region composition and the second region composition, in addition to the other two methods. Here, the prepared negative electrode coating has a thickness of 12 μm, the first region has a thickness of 6 μm, and the second region has a thickness of 6 μm. Furthermore, the prepared negative electrode has 5 wt% Ag content based on 100 wt% of the total negative electrode coating, 73 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 7 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 15 wt% based on 100 wt% of the total negative electrode coating.

[0160] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0161] Example 4

[0162] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 82:2:9:7.

[0163] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 23:2:72:3.

[0164] A negative electrode for an all-solid-state battery is prepared, in addition to using the first region composition and the second region composition. Here, the prepared negative electrode coating has a thickness of 9 μm, the first region has a thickness of 6 μm, and the second region has a thickness of 3 μm. Furthermore, the prepared negative electrode has 2 wt% Ag content based on 100 wt% of the total negative electrode coating, 62.3 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 5.7 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 30 wt% based on 100 wt% of the total negative electrode coating.

[0165] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0166] Example 5

[0167] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 65:5:23:7.

[0168] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 2:1:95:2.

[0169] A negative electrode for an all-solid-state battery is prepared by using the first region composition and the second region composition, in addition to the other two methods. Here, the prepared negative electrode coating has a thickness of 8 μm, the first region has a thickness of 6 μm, and the second region has a thickness of 2 μm. Furthermore, the prepared negative electrode has 49.25 wt% Ag content based on 100 wt% of the total negative electrode coating, 4 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 5.75 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 49 wt% based on 100 wt% of the total negative electrode coating.

[0170] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0171] Example 6

[0172] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 62:5:30:3.

[0173] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 2:7:70:3.

[0174] A negative electrode for an all-solid-state battery is prepared by using the first region composition and the second region composition, in addition to the other two methods. Here, the prepared negative electrode coating has a thickness of 8 μm, the first region has a thickness of 4 μm, and the second region has a thickness of 4 μm. Furthermore, the prepared negative electrode has 6 wt% Ag content based on 100 wt% of the total negative electrode coating, 32 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 3 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 59 wt% based on 100 wt% of the total negative electrode coating.

[0175] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0176] (Comparative Example 1)

[0177] A negative electrode coating composition was prepared by mechanically mixing carbon black and Ag in a weight ratio of 75:25 using a mortar. The prepared negative electrode coating composition contained 25 wt% silver and 75 wt% carbon black.

[0178] The negative electrode for the all-solid-state battery was prepared in the same manner as in Example 1, except that the negative electrode coating composition was coated onto a stainless steel foil current collector. The resulting negative electrode coating had a thickness of 10 μm.

[0179] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0180] (Comparative Example 2)

[0181] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 60:5:30:5.

[0182] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 10:3:85:2.

[0183] A negative electrode for an all-solid-state battery is prepared by using the first region composition and the second region composition, in addition to the other two methods. Here, the prepared negative electrode coating has a thickness of 10 μm, the first region has a thickness of 6 μm, and the second region has a thickness of 4 μm. Furthermore, the prepared negative electrode has 4.2 wt% Ag content based on 100 wt% of the total negative electrode coating, 40 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 3.8 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 52 wt% based on 100 wt% of the total negative electrode coating.

[0184] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0185] (Comparative Example 3)

[0186] The first region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 40:10:44:6.

[0187] The second-region composition was prepared by mixing carbon black, Ag, Ag2S, and polyvinylidene fluoride binder in an N-methylpyrrolidone (NMP) solvent at a weight ratio of 2:1:96:1.

[0188] A negative electrode for an all-solid-state battery is prepared, in addition to using the first region composition and the second region composition. Here, the prepared negative electrode coating has a thickness of 6 μm, the first region has a thickness of 3 μm, and the second region has a thickness of 3 μm. Furthermore, the prepared negative electrode has 5.5 wt% Ag content based on 100 wt% of the total negative electrode coating, 22 wt% carbon black content based on 100 wt% of the total negative electrode coating, and 3.5 wt% binder content based on 100 wt% of the total negative electrode coating. Additionally, the AgS content is 69 wt% based on 100 wt% of the total negative electrode coating.

[0189] Using the negative electrode, the solid electrolyte of Example 1, and the counter electrode, an all-solid-state half-cell was manufactured in the same manner as in Example 1.

[0190] Experimental Example 1) Overvoltage Evaluation

[0191] The all-solid-state half-cells of Examples 1 to 6 and Comparative Examples 1 to 3, charged at 0.05C, began to show a voltage drop at OCV (open-circuit voltage, approximately 2.5 V). Subsequently, the cell voltage was measured at the point where an inflection point appeared near 0 mV. This result is provided as an initial overvoltage in Table 1 below.

[0192] Experiment Example 2) Evaluation of Initial Efficiency

[0193] All-solid-state half-cells according to Examples 1 to 6 and Comparative Examples 1 to 3 were charged and discharged once at 0.05 C to obtain the percentage of discharge capacity to charge capacity. The results are shown in Table 1 as initial efficiency.

[0194] Example 3) Evaluation of Output Efficiency

[0195] The all-solid-state half-cells according to Examples 1 to 6 and Comparative Examples 1 to 3 were charged at 0.05 C and discharged at 0.1 C. The percentage of discharge capacity to charge capacity was calculated, and the results are shown in Table 1 as output efficiency.

[0196] (Table 1)

[0197]

[0198] As shown in Table 1, the all-solid-state batteries of Examples 1 to 5, in which the second region has 99 to 1.5 times more metal sulfides than the first region, exhibited low overvoltage and excellent initial efficiency and output efficiency. On the other hand, Comparative Example 1, which did not contain metal sulfides, exhibited high overvoltage and slightly lower initial efficiency and output efficiency.

[0199] Furthermore, Comparative Examples 2 and 3, which have an excessive amount of metal sulfide based on the total amount of the negative electrode coating, exhibited excessively high overvoltages and significantly degraded initial and output efficiencies. In particular, in Comparative Example 3, no output efficiency results could be obtained due to a short circuit.

[0200] Experiment Example 4) SEM Photos and EDAX

[0201] The cross-section of the negative electrode in Example 2 was polished and planarized. Figure 5 SEM images of the surface of the negative electrode are shown. Additionally, Figure 6 show Figure 5 The EDAX measurement results for the negative electrode. For example... Figure 5 and 6 As shown, the negative electrode of Example 2 has different sulfur (S) amounts in selected region 2 and selected region 1, where the S amount is measured by EDAX component analysis of a portion of the region. This is performed to check the S amount in regions larger than the first and second regions. Therefore, the S amount in the second region is greater than the S amount in the first region.

[0202] While this disclosure has been described in conjunction with exemplary embodiments now considered practical, it will be understood that the invention is not limited to the disclosed embodiments, but rather is intended to cover a variety of modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A negative electrode for all-solid-state batteries, comprising: current collector; and The negative electrode coating on the current collector, The negative electrode coating comprises a first region adjacent to the current collector and a second region not adjacent to the current collector. The first region and the second region include metal sulfides, and the amount of metal sulfides in the second region is greater than the amount of metal sulfides in the first region.

2. The negative electrode for an all-solid-state battery according to claim 1, wherein the first region is a region corresponding to 80% to 20% of the total thickness of the negative electrode coating.

3. The negative electrode for an all-solid-state battery according to claim 1, wherein the second region is a region corresponding to 80% to 20% of the total thickness of the negative electrode coating.

4. The negative electrode for an all-solid-state battery according to claim 1, wherein the amount of the metal sulfide included in the second region is 99 to 1.5 times the amount of the metal sulfide included in the first region.

5. The negative electrode for an all-solid-state battery according to claim 1, wherein the amount of the metal sulfide is from 1% to 50% by weight based on 100% by weight of the total negative electrode coating.

6. The negative electrode for an all-solid-state battery according to claim 1, wherein the amount of the metal sulfide included in the first region is from 1% to 40% by weight, based on 100% by weight of the total first region.

7. The negative electrode for an all-solid-state battery according to claim 1, wherein the amount of the metal sulfide included in the second region is from 2% to 99% by weight, based on 100% by weight of the total second region.

8. The negative electrode for an all-solid-state battery according to claim 1, wherein the metal sulfide is Li2S, Ag2S, Au2S, Al3S2, Na2S, NiS, Ti2S, SnS, ZnS, CdS, MoS2, FeS, Cu2S, CuFeS2, or a combination thereof.

9. The negative electrode for an all-solid-state battery according to claim 1, wherein the metal sulfide comprises Li2S, and further comprises Ag2S, Au2S, Al3S2, Na2S, NiS, Ti2S, SnS, ZnS, CdS, MoS2, FeS, Cu2S, CuFeS2, or combinations thereof.

10. The negative electrode for an all-solid-state battery according to claim 1, wherein the end portions of the first region and the second region further comprise Ag2S, Ag2S, Au2S, Al3S2, Na2S, NiS, Ti2S, SnS, ZnS, CdS, MoS2, FeS, Cu2S, CuFeS2, or combinations thereof.

11. The negative electrode for an all-solid-state battery according to claim 10, wherein the end portion corresponds to 90% to 10% of the total length of the negative electrode coating in the length direction of the current collector.

12. The negative electrode for an all-solid-state battery according to claim 1, wherein the negative electrode coating comprises a carbon-based material and a metal.

13. The negative electrode for an all-solid-state battery according to claim 12, wherein the carbon-based material comprises amorphous carbon, crystalline carbon, or a mixture thereof.

14. The negative electrode for an all-solid-state battery according to claim 12, wherein the metal is Ag, Au, Sn, Zn, Al, Mg, Ge, Cu, In, Ni, Bi, Pt, Pd, or a combination thereof.

15. All-solid-state batteries, including: The negative electrode according to any one of claims 1 to 14, Positive electrode, and A solid electrolyte layer between the negative electrode and the positive electrode.

16. The all-solid-state battery according to claim 15, wherein the solid electrolyte is a sulfide-based solid electrolyte.

17. The all-solid-state battery of claim 15, wherein the all-solid-state battery further comprises a lithium-containing layer formed between the current collector and the negative electrode coating during initial charging.

18. The all-solid-state battery of claim 15, wherein the all-solid-state battery undergoes charging and discharging.

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