Electrodes for all-solid-state batteries

Abstract

An electrode for an all-solid-state battery is provided, comprising granules including a core including an active material, a first conductive material, and a binder, and a coating layer including a solid electrolyte and a second conductive material, the coating layer being positioned in contact with the outside of the core. According to one embodiment of the present invention, the first conductive material and the second conductive material have different sizes or shapes. The first conductive material has an aspect ratio of 4000 to 6000 and a BET specific surface area of ​​100 m. 2 / g~300m 2 The second coating material has an aspect ratio of 100 to 300 and a BET specific surface area of ​​10 m 2 / g~30m 2 The granules form an excellent electrical network even in the interior of the granules under all-solid-state conditions, and when an electrode including the granules is applied to an all-solid-state battery, the battery performance is improved.

Description

[Technical Field]

[0001] The present application relates to an electrode for an all-solid-state battery. Specifically, the present invention relates to an electrode for an all-solid-state battery comprising granules, the granules comprising a core comprising an active material, a first conductive material, and a binder, and a coating layer comprising a solid electrolyte and a second conductive material.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0119465, filed on September 21, 2022, and incorporates all of the contents disclosed in the documents of that Korean patent application as part of this specification. [Background technology]

[0003] Currently, various batteries that can overcome the limitations of lithium secondary batteries are being researched from the viewpoints of battery capacity, safety, output, size increase, and miniaturization.

[0004] Research is currently being conducted in both academia and industry on a range of battery types, including metal-air batteries, which have a much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries, which are safe and do not pose a risk of explosion, supercapacitors, NaS batteries or RFBs (redox flow batteries), which are large-scale batteries, and thin film batteries, which are ultra-miniaturized batteries.

[0005] Among these, all-solid-state batteries are batteries in which the liquid electrolyte used in conventional lithium secondary batteries is replaced with a solid, and because they do not use flammable solvents inside the battery, there is absolutely no risk of fire or explosion due to the decomposition reaction of conventional electrolytes, which greatly improves safety.In addition, because lithium metal or lithium alloys can be used as the anode material, there is the advantage that the energy density relative to the mass and volume of the battery can be dramatically improved.

[0006] Sulfide-based solid electrolytes are among the most popular solid electrolytes.-3 ~10 -2 It has a high ionic conductivity of S / cm, is ductile, and has good contact with the interface, which is advantageous for improving resistance, but it is sensitive to moisture, e.g., it generates H2S gas when it comes into contact with water, so it is necessary to create an extremely dry environment during manufacturing. In addition, it is necessary to improve the cohesion of the active material and solid electrolyte, and high-density electrodes are required by reducing the porosity.

[0007] Therefore, in order to solve the problems faced in the technical field, the present inventors have continuously studied electrodes for all-solid-state batteries and completed the present invention. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2016-0146737 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to improve the performance of an electrode for an all-solid-state battery, an electrode for an all-solid-state battery is provided, which incorporates, as an electrode active material layer, granules including a core including an active material, a first conductive material, and a binder, and a coating layer including a solid electrolyte and a second conductive material. [Means for solving the problem]

[0010] According to a first aspect of the present invention, The battery includes granules each including a core containing an active material, a first conductive material, and a binder, and a coating layer located outside the core and in contact with the core, the coating layer including a solid electrolyte and a second conductive material.

[0011] According to one embodiment of the present invention, the first and second conductive materials have different sizes or shapes.

[0012] According to one embodiment of the present invention, the first conductive material has an average diameter of 10 nm to 30 nm.

[0013] According to one embodiment of the present invention, the first conductive material has an aspect ratio of 4000 to 6000 and a BET specific surface area of 100 m 2 / g to 300 m 2 / g.

[0014] According to one embodiment of the present invention, the second conductive material has an average diameter of 100 nm to 500 nm.

[0015] According to one embodiment of the present invention, the second conductive material has an aspect ratio of 100 to 300 and a BET specific surface area of 10 m 2 / g to 30 m 2 / g.

[0016] According to one embodiment of the present invention, the first conductive material includes carbon nanotubes.

[0017] According to one embodiment of the present invention, the second conductive material includes carbon nanofibers.

[0018] In one embodiment of the present invention, the active material is a positive electrode active material, and the positive electrode active material is LiCoO2, LiNiO2, LiMnO2, Li2MnO3, LiMn2O4, Li(Ni a Co b Mn c )O2 (0 < a < 1, 0 < b <​​​​​​​​​​​​​​​​​​​​​​​​​​

[0019] According to one embodiment of the present invention, the solid electrolyte includes a sulfide-based solid electrolyte.

[0020] According to one embodiment of the present invention, the granules are spherical particles having a diameter of 30 μm to 150 μm.

[0021] According to one embodiment of the present invention, the weight ratio of the solid electrolyte in the coating layer is 15 wt % to 40 wt % based on the total weight of the granules.

[0022] According to one embodiment of the present invention, the weight ratio of the second conductive material in the coating layer is 0.01 wt % to 1 wt % based on the total weight of the granules.

[0023] According to one embodiment of the present invention, the core comprises 85 wt % to 99.8 wt % of active material, 0.1 wt % to 10 wt % of binder, and 0.1 wt % to 10 wt % of first conductive material, based on the total weight of the core.

[0024] According to one embodiment of the present invention, the weight ratio of the first conductive material to the second conductive material is 5:1 to 30:1.

[0025] According to one embodiment of the present invention, the coating layer is applied onto the core by mechanofusion. [Effects of the Invention]

[0026] An electrode for an all-solid-state battery according to one embodiment of the present invention includes granules including a core including an active material, a first conductive material, and a binder, and a coating layer including a solid electrolyte and a second conductive material, and in the granules, the first conductive material and the second conductive material are adjusted to have different specifications in consideration of the functionality of the core and the coating layer.

[0027] As a result, the granules described above form an excellent electrical network even inside the granules under all-solid-state conditions, and when used as electrodes in all-solid-state batteries, this contributes to improving battery performance. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 2 is a diagram showing a schematic diagram of the shape of a granule according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The embodiments provided according to the present invention can all be achieved by the following description, which should be understood as describing preferred embodiments of the present invention, and should not be construed as necessarily limiting the present invention.

[0030] Unless the measurement conditions and methods for the physical properties described herein are specifically described, the physical properties are measured according to the measurement conditions and methods commonly used by those of ordinary skill in the art.

[0031] In one embodiment of the present invention, a granule is provided, comprising a core containing an active material and a coating layer containing a solid electrolyte. The granule may be used in an electrode for an all-solid-state battery. To facilitate understanding of the structure of the granule, FIG. 1 provides a schematic diagram illustrating the shape of a granule according to one embodiment of the present specification. As shown in FIG. 1, the core (10) is spherical and located inside the granule, and the coating layer (20) is located so as to surround the core. The granule (100) comprising the core and coating layer is a spherical particle. Here, "spherical" does not strictly mean a perfect sphere, but is generally used as a comprehensive concept that includes round particles. The core contains an active material, a first conductive material, and a binder, and the coating layer contains a solid electrolyte and a second conductive material. The active material in powder form is bound together with the conductive material by a binder solution and grows into particles having a specific range of dimensions to form the core. A slurry containing the solid electrolyte and the second conductive material is applied to the core to form the coating layer. The coating layer may be a single layer that covers the entire surface of the core, or may be multiple layers that cover only a portion of the core.

[0032] According to one embodiment of the present invention, the conductive material contained in the core and the conductive material contained in the coating layer have different specifications. The specifications refer to standards suitable for use in the core or coating layer according to one embodiment of the present invention, and the specifications may relate to, for example, size or shape. Here, size or shape refers to the average diameter, aspect ratio, BET specific surface area, etc., as described below. In this specification, to distinguish between the conductive material contained in the core and the conductive material contained in the coating layer, the conductive material contained in the core will be referred to as a first conductive material, and the conductive material contained in the coating layer will be referred to as a second conductive material.

[0033] The first conductive material, together with the active material and binder, forms the center and serves as an electrical path for the active material located at the center of the sphere. The first conductive material may be uniformly dispersed so as to contact most of the active material, while reducing the amount of conductive material used, which is advantageous for improving the energy density of the electrode. To achieve this object, according to one embodiment of the present invention, the first conductive material may be a cylindrical conductive material. The cylindrical shape may be subject to deformation, such as bending, due to external pressure. According to one embodiment of the present invention, the first conductive material has an average diameter of 10 nm to 30 nm. The average diameter is the arithmetic mean value of the diameter of a circle in the cylindrical shape, and is measured through particles distinguished in a scanning electron microscope (SEM) image. Here, the term "circle" is not limited to a perfect circle and may be interpreted in a broad sense. Specifically, the average diameter of the first conductive material is 10 nm or more, 11 nm or more, 12 nm or more, 13 nm or more, 14 nm or more, 15 nm or more, and 30 nm or less, 29 nm or less, 28 nm or less, 27 nm or less, 26 nm or less, 25 nm or less, or may be 10 nm to 30 nm, 13 nm to 28 nm, or 15 nm to 25 nm. By using a relatively thin conductive material in the center, the volume of the conductive material in the granule can be reduced and the amount of active material can be increased.

[0034] According to one embodiment of the present invention, the first conductive material has an aspect ratio of 4000 to 6000. The aspect ratio is calculated by the following equation 1, and the length of the major axis or minor axis used in equation 1 is measured through particles distinguished in an SEM image.

[0035] [Formula 1] Aspect ratio = major axis length / minor axis length

[0036] Here, the "major axis length" refers to the longest perpendicular distance between two parallel tangent lines of a particle, and the "minor axis length" refers to the shortest perpendicular distance between two parallel tangent lines of the particle. In a cylindrical shape, the major axis length may be the height, and the minor axis length may be the diameter. Since the major axis length is equal to or longer than the minor axis length, the aspect ratio has a value of 1 or greater. Specifically, the aspect ratio of the first conductive material is 4000 or greater, 4100 or greater, 4200 or greater, 4300 or greater, 4400 or greater, or 4500 or greater, and is 6000 or less, 5900 or less, 5800 or less, 5700 or less, 5600 or less, or 5500 or less, and may be 4000 to 6000, 4300 to 5800, or 4500 to 5500. A larger aspect ratio is more advantageous for the conductive material to form an electrical network within the granule.

[0037] According to one embodiment of the present invention, the first conductive material has a BET specific surface area of ​​100 m 2 / g~300m 2 / g. The BET specific surface area is a specific surface area measured by the BET method, and can be calculated from the mass gas adsorption amount at liquid nitrogen temperature (77K) using, for example, a BELSORP-mini II manufactured by BEL Japan. Specifically, the BET specific surface area of ​​the first conductive material is 100 m 2 / g or more, 110m 2 / g or more, 120m 2 / g or more, 130m 2 / g or more, 140m 2 / g or more, 150m 2 / g or more, and 300m 2 / g or less, 290m 2 / g or less, 280m 2 / g or less, 270m 2 / g or less, 260m 2 / g or less, 250m 2 / g or less, and 100m 2 / g~300m 2 / g, 130m 2 / g~280m 2 / g, 150m 2 / g~250m 2Within the above range of BET specific surface area, the first conductive material can increase the accessibility to the active material and the solid electrolyte.

[0038] According to one embodiment of the present invention, the granules are spherical particles having a diameter of 30 μm to 150 μm. Here, spherical particles do not mean perfectly spherical particles, and the diameter refers to the longest distance from any point on the particle surface to another point on the surface. Specifically, the diameter of the granules is 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, or 50 μm or more, and 150 μm or less, 145 μm or less, 140 μm or less, 135 μm or less, 130 μm or less, 125 μm or less, or 120 μm or less, and may be 30 μm to 150 μm, 40 μm to 135 μm, or 50 μm to 120 μm. Granule sizes within the above ranges form an appropriate level of voids within the granule layer, facilitating the introduction of additional sulfide-based solid electrolyte and the transformation and movement of materials due to electrochemical reactions. The granule may have a shape as shown in FIG. 1, including a core and a coating layer, and the core may occupy two-thirds or more of the diameter of the granule.

[0039] The electrode for an all-solid-state battery according to one embodiment of the present invention may be either a negative electrode or a positive electrode, and more specifically, the electrode for an all-solid-state battery may be a positive electrode.

[0040] When the electrode is a negative electrode, the electrode active material contained in the granules may be any material that can be used as a negative electrode active material for a lithium ion secondary battery. For example, the negative electrode active material may be carbon such as non-graphitizable carbon or graphite carbon; x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanium oxides, etc. One or more selected from the above may be used. According to one embodiment of the present invention, the negative electrode active material may contain a carbon-based material and / or Si.

[0041] When the electrode is a positive electrode, the electrode active material contained in the granules may be used without limitation as long as it can be used as a positive electrode active material of a lithium ion secondary battery. For example, the positive electrode active material may be a lithium transition metal oxide containing one or more transition metals. In one embodiment of the present invention, the positive electrode active material is LiCoO2, LiNiO2, LiMnO2, Li2MnO3, LiMn2O4, Li(Ni a Co b Mn c )O2(0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), LiNi 1-y Co y O2(0 < y < 1), LiCo 1-y Mn y O2(0 < y < 1), LiNi 1-y Mn y O(0 < y < 1), Li(Ni a Co b Mn c )O4(0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-z Ni z O4(0 < z < 2), LiMn 2-z Co z O4(0 < z < 2) and combinations thereof selected from the group consisting of.

[0042] The binder contained in the granules according to one embodiment of the present invention is mixed with the active material and conductive material, which are fine particles in powder form, to bind the components and promote particle growth. For example, sulfide-based solid electrolytes are sensitive to moisture, e.g., they generate H2S gas when in contact with moisture, so it is preferable to remove moisture as much as possible from the time of granule formation. According to one embodiment of the present invention, the binder is an organic binder. The organic binder refers to a binder that dissolves or disperses in an organic solvent, particularly N-methylpyrrolidone (NMP), and is distinguished from aqueous binders that use water as a solvent or dispersion medium. Specifically, the organic binder may be selected from the group consisting of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyimide, polyamide-imide, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butylene rubber, and fluororubber, but is not limited thereto.

[0043] According to one embodiment of the present invention, the active material in the center portion is 85 wt % to 99.8 wt %, specifically 90 wt % to 99.5 wt %, more specifically 95 wt % to 99.0 wt %, the binder is 0.1 wt % to 10 wt %, specifically 0.5 wt % to 7.5 wt %, more specifically 1 wt % to 5 wt %, and the first conductive material is 0.1 wt % to 10 wt %, specifically 0.2 wt % to 5 wt %, more specifically 0.3 wt % to 1 wt %. Adjusting the contents of the active material, binder, and first conductive material within the aforementioned ranges is advantageous for improving battery performance, which may be due to the effect of reducing the content of the first conductive material due to the physical properties of the first conductive material.

[0044] According to one embodiment of the present invention, the core has a porosity of 10% to 40%. The porosity of the core refers to the volume ratio of voids in the granule. The porosity can be measured, for example, using a mercury porosity analyzer (Micromeritics Autopore), but is not limited thereto. Specifically, the porosity of the granule may be 10% or more, 15% or more, 20% or more, or 25% or more, and 40% or less, 35% or less, or 30% or less, or may be 10% to 40%, 15% to 35%, or 25% to 30%. If the porosity of the core is below this range, the sulfide-based solid electrolyte introduced from the coating layer or additionally may not be in close contact with the components in the core, resulting in insignificant improvement in battery performance. On the other hand, if the porosity of the core exceeds this range, the amount of active material is reduced relative to the volume of the core, making it difficult to provide an electrode with a high active material loading, resulting in insignificant improvement in battery performance.

[0045] According to one embodiment of the present invention, the core is coated with a slurry containing a solid electrolyte and a second conductive material to form a coating layer. The coating layer covers at least a part or all of the surface of the core. In the coating layer, the solid electrolyte may be one or more selected from a polymer solid electrolyte and an inorganic solid electrolyte.

[0046] The polymer solid electrolyte may be a polymer solid electrolyte formed by adding a polymer resin to a solvated lithium salt, or may be an organic electrolyte solution containing an organic solvent and a lithium salt, an ionic liquid, a monomer or an oligomer, or a polymer gel electrolyte formed by adding the like to a polymer resin. According to one embodiment of the present invention, the lithium salt is an ionizable lithium salt, and Li + X - The anion of such a lithium salt is not particularly limited, but can be represented by F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4- , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - Examples include:

[0047] The solid polymer electrolyte may include, as a polymer resin, one or more materials selected from the group consisting of polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionically dissociable groups. The solid polymer electrolyte may also include, as a polymer resin, one or more materials selected from the group consisting of branched copolymers in which amorphous polymers such as PMMA, polycarbonate, polysiloxane (PDMS), and / or phosphazene are copolymerized with a PEO (polyethylene oxide) main chain using a comonomer, comb-like polymers, and cross-linked polymers.

[0048] The inorganic solid electrolyte may include a sulfide-based solid electrolyte, a halide-based solid electrolyte, an oxide-based solid electrolyte, or at least one of these.

[0049] The sulfide-based solid electrolyte is an electrolyte component containing sulfur atoms, and is not limited to a specific component, and may include one or more of a crystalline solid electrolyte, an amorphous solid electrolyte (glassy solid electrolyte), and a glass ceramic solid electrolyte. Specific examples of the sulfide-based solid electrolyte include an LPS-type sulfide containing sulfur and phosphorus, Li 4-x Ge 1-x P x S4 (x is 0.1 to 2, specifically x is 3 / 4, 2 / 3), Li 10±1 MP2X 12 (M=Ge,Si,Sn,Al,X=S,Se), Li 3.833 Sn 0.833 As 0.166 S4, Li4SnS4, Li 3.25 Ge 0.25 P 0.75 S4, Li2S-P2S5, B2S3-Li2S, xLi2S-(100-x)P2S5 (x is 70 to 80), Li2S-SiS2-Li3N, Li2S-P2S5-LiI, Li2S-SiS2-LiI, Li2S-B2S3-LiI, etc., but are not necessarily limited to these.

[0050] The halide-based solid electrolyte may include at least one of Li3YCl6 and Li3YBr6, but is not necessarily limited thereto.

[0051] The oxide-based solid electrolyte may be, for example, Li 3x La 2 / 3-x LLT system with perovskite structure such as TiO3, Li 14 LISICON such as Zn(GeO4)4, Li 1.3 Al 0.3 Ti 1.7 LATP systems such as (PO4)3, (Li 1+x Ge 2-x Al xThe phosphate-based compounds such as LAGP-based compounds (PO4)3) and phosphate-based compounds such as LiPON may be appropriately selected and used, but are not necessarily limited to these.

[0052] According to one embodiment of the present invention, the solid electrolyte includes a sulfide-based solid electrolyte.

[0053] The second conductive material forms a coating layer together with the solid electrolyte, electrically connecting the solid electrolyte within the coating layer. The spherical center serves as a pathway for electrical connection with other granules, other electrodes, and the solid electrolyte layer between electrodes. While the solid electrolyte within the coating layer may cause electrical short circuits between active materials, the presence of the second conductive material can eliminate such short circuits. The second conductive material is preferably distributed thinly and uniformly within the coating layer to provide the aforementioned functionality. To achieve this objective, according to one embodiment of the present invention, the second conductive material may be cylindrical. The cylindrical shape may be subject to deformation, such as bending, due to external pressure. According to one embodiment of the present invention, the second conductive material has an average diameter of 100 nm to 500 nm. The average diameter is measured using the same method as for the first conductive material. Specifically, the average diameter of the second conductive material is 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, and 500 nm or less, 480 nm or less, 460 nm or less, 440 nm or less, 420 nm or less, 400 nm or less, or may be 100 nm to 500 nm, 130 nm to 460 nm, or 150 nm to 400 nm. By using a relatively thick conductive material in the coating layer, it is possible to impart only the necessary functionality for conductivity without causing side reactions in relation to the solid electrolyte.

[0054] According to one embodiment of the present invention, the second conductive material has an aspect ratio of 100 to 300. The aspect ratio is measured using the same method as for the first conductive material. Specifically, the aspect ratio of the second conductive material is 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, or 150 or more, and is 300 or less, 290 or less, 280 or less, 270 or less, 260 or less, or 250 or less, and may be 100 to 300, 130 to 280, or 150 to 250. If the aspect ratio is too large, problems such as aggregation between conductive materials may occur. Therefore, in order to uniformly disperse the second conductive material within the coating layer, it is preferable to adjust the aspect ratio to an appropriate level.

[0055] According to one embodiment of the present invention, the second conductive material has a BET specific surface area of ​​10 m 2 / g~30m 2 / g. The BET specific surface area is measured in the same manner as that of the first conductive material. Specifically, the BET specific surface area of ​​the second conductive material is 2 / g or more, 11m 2 / g or more, 12m 2 / g or more, 13m 2 / g or more, 14m 2 / g or more, 15m 2 / g or more, and 30m 2 / g or less, 29m 2 / g or less, 28m 2 / g or less, 27m 2 / g or less, 26m 2 / g or less, 25m 2 / g or less, and 10m 2 / g~30m 2 / g, 13m 2 / g~28m 2 / g, 15m 2 / g~25m 2 If the specific surface area is too large, problems such as side reactions with the solid electrolyte may occur, and therefore, in order to achieve only the desired functionality of conductivity in the coating layer, it is preferable to adjust the specific surface area to an appropriate level.

[0056] The first and second conductive materials may be any conductive materials commonly used in the art, as long as they satisfy the above-mentioned specifications. According to one embodiment of the present invention, the first conductive material includes carbon nanotubes. According to another embodiment of the present invention, the second conductive material includes carbon nanofibers.

[0057] According to one embodiment of the present invention, the weight ratio of the solid electrolyte in the coating layer is 15 wt% to 40 wt% based on the total weight of the granules. Specifically, the weight ratio of the solid electrolyte is 15 wt% or more, 16 wt% or more, 17 wt% or more, 18 wt% or more, 19 wt% or more, or 20 wt% or more, and 40 wt% or less, 39 wt% or less, 38 wt% or less, 37 wt% or less, 36 wt% or less, or 35 wt% or less, or may be 15 wt% to 40 wt%, 18 wt% to 38 wt%, or 20 wt% to 35 wt%. When the solid electrolyte is introduced into the coating layer within this range, connectivity with the solid electrolyte outside the granules can be further improved.

[0058] According to one embodiment of the present invention, the weight ratio of the second conductive material in the coating layer is 0.01 wt% to 1 wt% based on the total weight of the granules. Specifically, the weight ratio of the second conductive material is 0.01 wt% or more, 0.02 wt% or more, or 0.03 wt% or more, and is 1 wt% or less, 0.9 wt% or less, 0.8 wt% or less, 0.7 wt% or less, 0.6 wt% or less, or 0.5 wt% or less, and may be 0.01 wt% to 1 wt%, 0.02 wt% to 0.8 wt%, or 0.03 wt% to 0.5 wt%. When the second conductive material is introduced into the coating layer within this range, the connectivity between the active materials can be further improved.

[0059] The first conductive material, which is directly mixed with the active material within the granules, may generally be contained in a larger amount than the second conductive material. According to one embodiment of the present invention, the weight ratio of the first conductive material to the second conductive material is 5:1 to 30:1. Specifically, the weight ratio of the first conductive material to the second conductive material is 5:1 or more, 5.5:1 or more, or 6:1 or more, and is 30:1 or less, 25:1 or less, or 20:1 or less, and may be 5:1 to 30:1, 5.5:1 to 25:1, or 6:1 to 20:1. Within this range, the effect of separately introducing the conductive material into the core and the coating layer may be further enhanced.

[0060] The coating layer is formed by applying a coating material containing a solid electrolyte and a second conductive material to the core, and various methods used in the art may be used as the application method. According to one embodiment of the present invention, the coating layer is applied to the core using a mechanofusion method. The mechanofusion method can apply high shear force to the coating layer, thereby forming a thin and uniform coating layer. In addition, the high shear force of the mechanofusion method is advantageous for easily penetrating the voids in the core, such as a sulfide-based solid electrolyte, which has a relatively smaller particle size than the second conductive material, and forming an electrical network within the granules.

[0061] An electrode for an all-solid-state battery according to one embodiment of the present invention is fabricated by loading granules onto a current collector to form a sheet-like granule layer. The current collector is electrically conductive, such as a metal plate, and electrodes known in the art may be used appropriately depending on the polarity of the battery. Because the granules constituting the granule layer each include a coating layer containing a solid electrolyte and a second conductive material, a sufficient electrical network can be formed between the granules constituting the granule layer. Furthermore, the electrical network can be supplemented by impregnating the voids between the granule layers with a solid electrolyte and drying the impregnated voids. Furthermore, using a sulfide-based solid electrolyte as the supplementary solid electrolyte, like the coating layer, can reduce resistance within the battery and contribute to improved battery performance.

[0062] According to one embodiment of the present invention, in the all-solid-state battery electrode, the electrode active material layer has a thickness of 100 μm to 300 μm. Here, the electrode active material layer refers to a sheet-like layer applied to the current collector, excluding the current collector when a current collector is used in the manufacture of the electrode, and the electrode active material layer contains the granules described above, with a solid electrolyte optionally being filled into the gaps between the granules. Specifically, the thickness of the electrode active material layer is 100 μm or more, 110 μm or more, 120 μm or more, 130 μm or more, 140 μm or more, or 150 μm or more, and may be 300 μm or less, 290 μm or less, 280 μm or less, 270 μm or less, 260 μm or less, or 250 μm or less, or may be 100 μm to 300 μm, 120 μm to 270 μm, or 150 μm to 250 μm. If the thickness of the electrode active material layer is less than the above range, the loading amount of the active material may decrease, and the improvement in battery performance may not be significant. If the thickness of the electrode active material layer is more than the above range, the durability of the electrode may decrease, and the improvement in battery performance may not be significant.

[0063] In one aspect of the present invention, an all-solid-state battery is provided that includes the above-described all-solid-state battery electrode as a positive electrode and / or a negative electrode. In constructing the all-solid-state battery, in addition to the solid electrolyte contained in the electrode, a separate solid electrolyte layer may be introduced between the positive electrode and the negative electrode. This solid electrolyte layer may also function as a separator in a typical lithium secondary battery. The above-described electrode may also be used with a liquid electrolyte to form a semi-solid-state battery, in which case a separate polymer separator may be required.

[0064] The polymer separator is interposed between the negative electrode and the positive electrode, and serves to electrically insulate the negative electrode from the positive electrode while allowing lithium ions to pass through. The polymer separator may be any polymer separator membrane commonly used in the field of all-solid-state batteries, and is not particularly limited.

[0065] In one aspect of the present invention, there are provided a battery module including the all-solid-state battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source.

[0066] Specific examples of the device include, but are not limited to, power tools powered by electric motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0067] Preferred examples are shown below to aid in understanding the present invention. However, the following examples are provided to make the present invention easier to understand, and the present invention is not limited thereto.

[0068] Manufacturing example: Manufacturing granules containing active materials Manufacturing Example 1 LiNi as the active material 0.6 Co 0.2 Mn 0.2 O2 (NCM 622), carbon nanotubes (average particle size: approximately 15 nm, aspect ratio: approximately 5000, BET specific surface area: approximately 150 m) as the first conductive material. 2 / g) and polyvinylidene fluoride (PVDF) as a binder were mixed in N-methylpyrrolidone solvent at a weight ratio of 96.7:0.3:3 (active material: conductive material: binder) to prepare a slurry, which was then spray-dried to prepare a core portion with a diameter of approximately 60 μm (porosity: approximately 30%).

[0069] The sulfide-based solid electrolyte was Li2S-P2S5, and the second conductive material was carbon nanofiber (diameter: approximately 250 nm, aspect ratio: approximately 200, BET specific surface area: approximately 20 m). 2The mixture (0.15 wt. / g) was then placed in a mechanofusion device (manufacturer: Hosokawa Micron, product: Nobilta NOB-130) at 3,000 rpm for 10 minutes to produce granules with a diameter of approximately 70 μm and coated with a coating layer. The solid electrolyte content in the granules was approximately 25 wt. % and the second conductive material content was approximately 0.03 wt. %.

[0070] Comparative Manufacturing Example 1 The core was manufactured in the same manner as in Manufacturing Example 1, except that only the sulfide-based solid electrolyte was used without the second conductive material when forming the coating layer. Comparative Manufacturing Example 2 Granules were prepared in the same manner as in Preparation Example 1, except that the second conductive material was the same as the first conductive material when forming the coating layer (core: first conductive material, coating layer: first conductive material).

[0071] Comparative Manufacturing Example 3 Granules were produced in the same manner as in Production Example 1, except that the first conductive material was the same as the second conductive material when producing the core (core: second conductive material, coating layer: second conductive material).

[0072] Example: Manufacture of electrodes and batteries containing the produced granules Example 1 The granules prepared in Preparation Example 1 were applied to one side of an aluminum current collector, rolled, and dried to prepare a cathode with a thickness of approximately 130 μm (the sulfide-based electrolyte was approximately 20 wt% of the granules). Li2S-LiCl-P2S5 was mixed with a polyvinylidene fluoride (PVDF) solution (a solution in which PVDF and toluene were mixed in a weight ratio of 8:92) to prepare a slurry, which was then applied to a thickness of approximately 100 μm on a lithium foil with a thickness of approximately 50 μm to prepare a solid electrolyte and an anode. The cathode and anode were stacked and pressed to prepare an electrode assembly, which was then placed inside a battery case to prepare an all-solid-state battery.

[0073] Comparative Example 1 An all-solid-state battery was manufactured in the same manner as in Example 1, except that the granules manufactured in Comparative Preparation Example 1 were used instead of Preparation Example 1 when manufacturing the positive electrode.

[0074] Comparative Example 2 An all-solid-state battery was manufactured in the same manner as in Example 1, except that the granules manufactured in Comparative Preparation Example 2 were used instead of Preparation Example 1 when manufacturing the positive electrode.

[0075] Comparative Example 3 An all-solid-state battery was manufactured in the same manner as in Example 1, except that the granules manufactured in Comparative Preparation Example 3 were used instead of Preparation Example 1 when manufacturing the positive electrode.

[0076] Experimental Example: Evaluation of Manufacturing Examples and Working Examples Experimental example 1: Battery performance evaluation The batteries of Example 1 and Comparative Examples 1 to 3 were discharged at 0.1 C and 1.0 C, respectively, and the initial coulombic efficiency (0.1 C charge / discharge) and discharge capacity ratio (1.0 C discharge capacity / 0.1 C discharge capacity × 100, %) were measured. The results are shown in Table 1 below.

[0077] [Table 1]

[0078] According to Table 1, the battery of Example 1 (first conductive material (core)-second conductive material (coating layer)) did not show any significant decrease in battery performance even under higher C-rate conditions, whereas the battery performance of Comparative Example 1 (first conductive material (core)), Comparative Example 2 (first conductive material (core)-first conductive material (coating layer)), and Comparative Example 3 (second conductive material (core)-second conductive material (coating layer)) showed a significant decrease in battery performance under higher C-rate conditions.

[0079] All mere variations and modifications of the present invention belong to the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims. [Explanation of symbols]

[0080] 10: Center 20: Coating layer 100: Granules

Claims

1. a core including an active material, a first conductive material, and a binder; the coating layer is located outside the center and includes a granule having a solid electrolyte and a second conductive material; the first conductive material and the second conductive material have different sizes or shapes; the first conductive material has an aspect ratio of 4000 to 6000; The second conductive material has an aspect ratio of 100 to 300.

2. the first conductive material is a cylindrical conductive material having an average diameter of 10 nm to 30 nm; The electrode for an all-solid-state battery according to claim 1 , wherein the average diameter is an arithmetic mean value of diameters of circles in a cylindrical shape, and is measured by SEM.

3. The first conductive material has a BET specific surface area of ​​100 m ２ / g to 300m ２ The electrode for an all-solid-state battery according to claim 1 , wherein the SiO 2 content is 1 / g.

4. the second conductive material is a cylindrical conductive material having an average diameter of 100 nm to 500 nm, The electrode for an all-solid-state battery according to claim 1 , wherein the average diameter is an arithmetic mean value of diameters of circles in a cylindrical shape, and is measured by SEM.

5. The second conductive material has a BET specific surface area of ​​10 m ２ / g to 30m ２ The electrode for an all-solid-state battery according to claim 1 , wherein the SiO 2 content is 1 / g.

6. The electrode for an all-solid-state battery according to claim 1 , wherein the first conductive material comprises carbon nanotubes.

7. The electrode for an all-solid-state battery according to claim 1 , wherein the second conductive material includes carbon nanofibers.

8. the active material is a positive electrode active material, The positive electrode active material is LiCoO ２ , LiNiO ２ , LiMnO ２ , Li ２ MnO ３ , LiMn ２ O ４ , Li(Ni ａ Co ｂ Mn ｃ ) O ２ (0<a<1, 0<b<1, 0<c<1, a+b+c=1), LiNi １－ｙ Co ｙ O ２ (0<y<1), LiCo １－ｙ Mn ｙ O ２ (0<y<1), LiNi １－ｙ Mn ｙ O ２ (0<y<1), Li(Ni ａ Co ｂ Mn ｃ ) O ４ (0<a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn ２－ｚ Ni ｚ O ４ (0<z<2), LiMn ２－ｚ Co ｚ O ４ 2. The electrode for an all-solid-state battery according to claim 1, wherein z is selected from the group consisting of (0<z<2) and combinations thereof.

9. The electrode for an all-solid-state battery according to claim 1 , wherein the solid electrolyte includes a sulfide-based solid electrolyte.

10. The electrode for an all-solid-state battery according to claim 1, wherein the granules are spherical particles having a diameter of 30 μm to 150 μm.

11. 2. The electrode for an all-solid-state battery according to claim 1, wherein a weight ratio of the solid electrolyte in the coating layer is 15 wt % to 40 wt % based on the total weight of the granules.

12. 2. The electrode for an all-solid-state battery according to claim 1, wherein a weight ratio of the second conductive material in the coating layer is 0.01 wt % to 1 wt % based on the total weight of the granules.

13. 2. The electrode for an all-solid-state battery according to claim 1, wherein the core comprises 85 wt % to 99.8 wt % of an active material, 0.1 wt % to 10 wt % of a binder, and 0.1 wt % to 10 wt % of a first conductive material, based on a total weight of the core.

14. 2. The electrode for an all-solid-state battery according to claim 1, wherein a weight ratio of the first conductive material to the second conductive material is 5:1 to 30:

1.

15. An electrode for an all-solid-state battery as described in claim 1, characterized in that an electrical network is formed within the granules.

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