Method for manufacturing an electrode for an all-solid-state battery and electrode manufactured by the same

Abstract

A method for manufacturing an electrode for an all-solid-state battery is provided, comprising the steps of: coating granules containing an active material on a current collector; aligning and fixing the coated granules; coating a solid electrolyte solution on the fixed granules; and moving the coated solid electrolyte solution into gaps between the granules. According to one embodiment of the present invention, the step of moving the solid electrolyte solution is performed under reduced pressure in a vacuum at 20° C. to 40° C. According to the manufacturing method, the solid electrolyte solution can be effectively and uniformly injected into gaps in a granule layer.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electrode for an all-solid-state battery and an electrode manufactured thereby. Specifically, the present invention relates to a method for manufacturing an electrode for an all-solid-state battery that can effectively inject a solid electrolyte solution into voids in a granular layer containing an active material, and an electrode manufactured thereby.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0185955 filed on December 23, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [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, and miniaturization.

[0004] Typically, research is being conducted on metal-air batteries, which have a much larger theoretical capacity than current 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-small.

[0005] Among these, all-solid-state batteries are batteries that replace the liquid electrolyte used in existing lithium secondary batteries with a solid, and because they do not use flammable solvents, they can significantly improve safety by eliminating the risk of fire or explosion caused by the decomposition reaction of conventional electrolytes.In addition, because they can use Li metal or Li alloy as the anode material, they have the advantage of dramatically improving the energy density relative to the mass and volume of the battery.

[0006] In particular, inorganic solid electrolytes for solid-state batteries can be divided into sulfide-based and oxide-based solid electrolytes. Currently, the solid electrolyte that has seen the most technological development is sulfide-based solid electrolytes, and materials have been developed that have ionic conductivity close to that of organic electrolytes.

[0007] Unlike existing lithium secondary batteries that use liquid electrolytes, all-solid-state batteries use a solid electrolyte, which can cause problems such as physical contact because the solid electrolyte cannot easily penetrate into the pores of the electrode. To address these issues, several methods have been studied, including mixing granules containing active material with a liquid solid electrolyte and then solidifying the mixture, and preparing granules containing active material, creating pores around the granules, and then injecting a liquid solid electrolyte into the pores and then solidifying the mixture. The first method makes it difficult for the granules containing active material to be effectively stacked on the current collector, resulting in reduced energy density. The second method also requires that the liquid solid electrolyte not be effectively injected into the pores, and the entire electrode, including the pores, must be immersed in the liquid solid electrolyte, resulting in problems such as granule detachment, which still need to be addressed.

[0008] Therefore, the present inventors have studied a method for more efficiently injecting a liquid phase solid electrolyte into the gaps between electrode granules in the production of electrodes for all-solid-state batteries, and have completed the present invention. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Publication No. 10-2013-0107352 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a method for manufacturing an electrode for an all-solid-state battery, which can improve the performance of the electrode by effectively and uniformly injecting a solid electrolyte solution into voids in a granular layer containing an active material. [Means for solving the problem]

[0011] According to a first aspect of the present invention, A method for manufacturing an electrode for an all-solid-state battery is provided, including the steps of: (1) applying granules containing an active material onto a current collector; (2) aligning and fixing the applied granules; (3) applying a solid electrolyte solution onto the fixed granules; and (4) moving the applied solid electrolyte solution into voids between the granules.

[0012] In one embodiment of the present invention, the step (4) is carried out at 20°C to 40°C under reduced pressure in vacuum.

[0013] In one embodiment of the invention, the granules are spherical particles having a diameter of 30 μm to 150 μm.

[0014] In one embodiment of the present invention, the granular layer formed of the granules fixed in step (2) has a porosity of 30% to 70%.

[0015] In one embodiment of the present invention, the granular layer formed of the granules fixed in step (2) has a thickness of 100 μm to 300 μm.

[0016] In one embodiment of the present invention, in the step (3), the solid electrolyte solution is applied in an amount of 20 to 40% by volume based on the volume of the granular layer.

[0017] In one embodiment of the present invention, in step (3), the solid electrolyte solution is applied in an amount of 40 to 70 volume % based on the void volume of the granular layer.

[0018] In one embodiment of the present invention, the solid electrolyte solution contains 20 wt % to 40 wt % of a solid component based on the total weight of the solid electrolyte solution.

[0019] In one embodiment of the present invention, the step (4) alternates between vacuum application and rest periods at intervals of 5 to 15 seconds.

[0020] In one embodiment of the present invention, the step (4) is repeated 3 to 10 cycles, with one cycle consisting of an active period and a rest period.

[0021] In one embodiment of the present invention, the method further comprises the step of (5) drying under reduced pressure in a vacuum at 60 to 80°C. [Effects of the Invention]

[0022] A method for manufacturing an electrode for an all-solid-state battery according to an embodiment of the present invention can effectively and uniformly inject a solid electrolyte solution into voids in a granular layer containing an active material formed on a current collector, thereby improving the performance of the electrode manufactured by the method. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic view illustrating a state before depressurization by vacuum after applying a solid electrolyte solution according to an embodiment of the present invention; [Figure 2] 1 is a schematic view illustrating a state in which a solid electrolyte solution is injected into voids between granules after depressurization by vacuum according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The embodiments provided by the present invention can all be achieved by the following description. The following description should be understood as describing preferred embodiments of the present invention, and it should be understood that the present invention is not necessarily limited thereto.

[0025] 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 skilled in the art.

[0026] One aspect of the present invention is to provide a method for manufacturing an electrode for an all-solid-state battery by injecting a solid electrolyte into a granular layer containing an active material formed on a current collector. According to one embodiment of the present invention, the method for manufacturing an electrode for an all-solid-state battery includes the steps of: applying granules containing an active material onto a current collector; aligning and fixing the applied granules; applying a solid electrolyte solution onto the fixed granules; and allowing the applied solid electrolyte solution to migrate into voids between the granules.

[0027] The active material is applied to a current collector in the form of granules. Unlike existing lithium secondary batteries that use liquid electrolytes, all-solid-state batteries use a solid electrolyte, which makes it difficult for the solid electrolyte to penetrate. If a powder-type active material is used as is, the utilization of the active material may be significantly reduced. After preparing the active material in the form of granules to form a basic network for improving the utilization of the active material within the granules, the solid electrolyte is injected into the voids enlarged during granule formation to form a physical contact between the granules and the solid electrolyte, which may significantly improve the utilization of the active material.

[0028] According to one embodiment of the present invention, the granules are spherical particles containing an active material, a conductive material, and a binder. Here, the term "spherical" does not strictly mean a perfect sphere, but is used as a general concept that includes particles with a round shape. The active material in powder form is bound together with the conductive material by a binder solution to grow into particles with a specific range of specifications.

[0029] 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 largest 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, 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, 120 μm or less, or may be 30 μm to 150 μm, 40 μm to 135 μm, or 50 μm to 120 μm. If the diameter of the granules is less than the above range, the voids in the granule layer are small, and the amount of the liquid-phase solid electrolyte that penetrates between the granules and coats them is reduced, making it difficult for the active material and the solid electrolyte to be in physical contact with each other in an all-solid-state battery. On the other hand, if the diameter of the granules is greater than the above range, the distance between the surface in contact with the solid electrolyte and the center of the granule is large, and the active material contained in the granules may not be fully utilized.

[0030] The electrode for an all-solid-state battery according to an embodiment of the present invention may be either an anode or a cathode, and more specifically, the electrode for an all-solid-state battery is a cathode.

[0031] When the electrode is a negative electrode, the electrode active material contained in the granules is not particularly limited as long as it is a material that can be used as a negative electrode active material for a lithium ion secondary battery. For example, the negative electrode active material can be carbon such as non-graphitizable carbon or graphite carbon; Li 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), etc. 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 species selected from can be used. According to one specific example of the present invention, the negative electrode active material can contain a carbon-based material and / or Si.

[0032] When the electrode is a positive electrode, the electrode active material contained in the granules is not particularly limited as long as it can be used as a positive electrode active material of a lithium ion secondary battery. For example, a lithium transition metal oxide containing one or more transition metals can be used as the positive electrode active material. According to one specific example 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(O < y < 1), LiCo 1‐y Mn y O2, LiNi 1‐y Mn y O2(O < 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 is selected from the group consisting of this combination.

[0033] The conductive material contained in the granules is not particularly limited as long as it is located within the granules and can provide conductivity between the active material and the electrolyte. For example, the conductive material may be nickel powder, cobalt oxide, titanium oxide, carbon, etc., and the carbon may be any one or more selected from the group consisting of ketjen black, acetylene black, furnace black, graphite, carbon fiber, and fullerene.

[0034] 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. Among solid electrolytes, sulfide-based solid electrolytes are sensitive to moisture, e.g., they generate H2S gas when in contact with moisture. Therefore, it is preferable to remove moisture as much as possible from the time of forming the granules. According to one embodiment of the present invention, the binder is an organic binder. The organic binder refers to a binder that is dissolved or dispersed in an organic solvent, particularly N-methylpyrrolidone (NMP), and is different 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), polyvinylidene 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.

[0035] According to one embodiment of the present invention, the granules contain 85 to 99.8 wt % of active material, specifically 88 to 99.5 wt %, more specifically 90 to 99.3 wt %, 0.1 to 10 wt %, specifically 0.2 to 8 wt %, more specifically 0.3 to 7 wt %, and 0.1 to 10 wt %, specifically 0.2 to 8 wt %, more specifically 0.3 to 7 wt %, of the binder, and 0.1 to 10 wt %, specifically 0.2 to 8 wt %, more specifically 0.3 to 7 wt %, of the conductive material. When the contents of the active material, binder, and conductive material are adjusted within the above ranges, improved battery performance is advantageous.

[0036] According to one embodiment of the present invention, the granules have a porosity of 10% to 40%. The porosity of the granules refers to the volume ratio of voids in the granules, and the porosity can be measured by, for example, but not limited to, BET (Brunauer-Emmett-Teller) measurement or mercury penetration (Hg) porosimetry. Alternatively, the porosity can be calculated using other parameters such as size, thickness, and density. Specifically, the porosity of the granules 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 granules is below this range, the solid electrolyte may not be in close contact with the granules, and a clear improvement in battery performance may not be observed. On the other hand, if the porosity of the granules exceeds this range, the amount of active material is reduced compared to the volume of the granules, and it may be difficult to provide an electrode with a high active material loading, and a clear improvement in battery performance may not be observed.

[0037] The granules may be manufactured by a method commonly used in the relevant technical field, and are not particularly limited. During the granule manufacturing process, a binder solution is added along with powder-like particulate active material and conductive material to grow the particle size of the granules to a specific level. As the solvent dries from the formed granules, the relatively light binder and conductive material may be positioned outside the granules, resulting in increased density outside the granules.

[0038] According to one embodiment of the present invention, to prepare an electrode for an all-solid-state battery, granules containing an active material are first coated on a current collector, and then the coated granules are aligned and fixed. The coating method may be a method commonly used in the relevant technical field and is not particularly limited. The composition of the granules may be as described above, and the amount of granules to be coated may be determined taking into account the battery performance and specific application. The coated granules may be in an irregular shape, resulting in an irregular surface and voids in the coating layer. By aligning the irregularly coated granules, the irregularities in the surface and voids of the coating layer can be reduced. Reducing the irregularities in the surface and voids makes it more advantageous to subsequently impregnate and coat the solid electrolyte solution, thereby achieving more stable battery performance. The aligned granules are then fixed to improve the durability of the electrode. If only the alignment process is performed without the granule fixation process, the granules introduced onto the current collector may easily detach during additional battery manufacturing processes or during the battery's operation. The granule fixation process is required to prevent this granule detachment phenomenon. The methods for aligning and fixing the granules may be methods commonly used in the relevant technical field and are not particularly limited. Generally, a roll may be used in the alignment and fixing process, and in the fixing process, the granules may be heated and cooled, and then fixed by a binder or the like inside the granules.

[0039] The layer formed by aligning and fixing the coated granules as described above is referred to herein as a granule layer or an electrode active material layer. According to one embodiment of the present invention, the granule layer has a thickness of 100 μm to 300 μm. Here, the "thickness" refers to the vertical distance between the current collector and the surface of the granule farthest from the current collector. Because the granules are aligned and fixed, the granules located on the surface of the granule layer are generally located at approximately the same distance from the current collector. Specifically, the thickness of the electrode active material layer may be 100 μm or more, 110 μm or more, 120 μm or more, 130 μm or more, 140 μm or more, 150 μm or more, and 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 be reduced and the improvement in battery performance may not be apparent. If the thickness of the electrode active material layer is more than the above range, the electrode may be too thick and the utilization of the active material in the electrode may be reduced.

[0040] According to one embodiment of the present invention, the granular layer has a porosity of 30% to 70%. The porosity of the granular layer refers to the volume ratio of voids in the granular layer, and may be measured by, for example, but not limited to, BET (Brunauer-Emmett-Teller) measurement or mercury penetration (Hg) porosimetry. Alternatively, the porosity may be calculated using other parameters, such as size, thickness, and density. Specifically, the porosity of the granular layer may be 30% or more, 33% or more, 36% or more, 39% or more, 42% or more, or 45% or more, and 70% or less, 67% or less, 64% or less, 61% or less, 58% or less, or 55% or less, or may be 30% to 70%, 36% to 61%, or 45% to 55%. If the porosity of the granular layer is less than the above range, it is difficult to introduce the solid electrolyte solution, and if the porosity of the granular layer is more than the above range, the electrode may become too thick, which is undesirable.

[0041] A solid electrolyte solution is applied to a granular layer formed by fixing the granules. Even if voids exist in the granular layer, the gas in the voids does not easily escape to the outside, so the solid electrolyte solution applied to the granular layer does not actively permeate the voids of the granular layer. The solid electrolyte may be a polymer solid electrolyte formed by adding a polymer resin to a solvated lithium salt, or a polymer gel electrolyte formed by adding an organic electrolyte containing an organic solvent and a lithium salt, an ionic liquid, a monomer or oligomer, or the like to a polymer resin. The solid electrolyte may be one or more selected from a polymer-based solid electrolyte, a sulfide-based solid electrolyte, and an oxide-based solid electrolyte. According to one embodiment of the present invention, the solid electrolyte is a sulfide-based solid electrolyte.

[0042] The solid electrolyte solution may be prepared by mixing the solid electrolyte with water or an organic solvent to impart fluidity to the solid electrolyte, and then drying to remove the water or organic solvent partially or completely. According to one embodiment of the present invention, the solid electrolyte solution contains 20 wt% to 40 wt% of solid components, based on the total weight of the solid electrolyte solution. Here, the solid components refer to the components remaining after complete drying to remove components such as water or an organic solvent. The content of the solid components may affect operating conditions, such as vacuum, as described below. Specifically, the content of the solid components may be 20 wt% or more, 21 wt% or more, 22 wt% or more, 23 wt% or more, 24 wt% or more, 25 wt% or more, and 40 wt% or less, 39 wt% or less, 38 wt% or less, 37 wt% or less, 36 wt% or less, 35 wt% or less, or 20 wt% to 40 wt%, 22 wt% to 37 wt%, 25 wt% to 35 wt%. If the content of the solid component is less than the above range, the content of the functional solid electrolyte may be too low, and if the content of the solid component is more than the above range, the fluidity of the solid electrolyte solution may be significantly reduced.

[0043] According to one embodiment of the present invention, the lithium salt is Li as an ionizable lithium salt. + X ‐ The anion of such a lithium salt is not particularly limited, but may be 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 ‐ In one embodiment of the present invention, the sulfide-based solid electrolyte contains sulfur (S) and can include Li-P-S-based glass or Li-P-S-based glass ceramics as an ion-conducting material for a metal belonging to Group 1 or 2 of the periodic table. Non-limiting examples of such sulfide-based solid electrolytes include Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-LiCl-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, and the like, and one or more of these may be included.

[0044] To facilitate understanding of the present invention, FIG. 1 schematically illustrates a state after a solid electrolyte solution has been applied and before the pressure has been reduced by vacuum according to one embodiment of the present invention. As in FIG. 1, a granular layer consisting of granules 20 is formed on a current collector 10, and a solid electrolyte solution 30 is applied onto the granular layer. Because the solid electrolyte solution 30 contains a fluid liquid phase, some of it may permeate the voids between the granular layer. However, in FIG. 1, the granular layer and the solid electrolyte solution 30 are shown as separate layers to clearly distinguish them. The amount of the solid electrolyte solution 30 can be adjusted taking into account the volume of the granular layer and the volume of the voids within the granular layer.

[0045] According to one embodiment of the present invention, the solid electrolyte solution is applied in an amount of 20 to 40% by volume based on the volume of the granular layer. Here, the volume of the granular layer is the surface area of the current collector on which the granules are applied multiplied by the thickness of the granular layer, and the volume of the solid electrolyte solution is measured before application. The amount of the solid electrolyte solution applied is 20 to 40% by volume, 21 to 22% by volume, 23 to 24% by volume, 25 to 35% by volume, or 40 to 39% by volume, 38 to 37% by volume, 36 to 35% by volume. If the amount of solid electrolyte solution applied is less than the above range, the amount of solid electrolyte solution may be insufficient and it may be difficult to uniformly disperse the solid electrolyte solution in the voids. If the amount of solid electrolyte solution applied is more than the above range, the efficiency of injection of the solid electrolyte solution into the voids may decrease even though the amount of solid electrolyte solution applied is sufficient to fill the voids.

[0046] According to one embodiment of the present invention, the solid electrolyte solution is applied in an amount of 40 to 70% by volume based on the pore volume of the granular layer. Here, the pore volume of the granular layer is calculated taking into account the volume and porosity of the granular layer. It is preferable that the solid electrolyte solution is applied in an appropriate amount so that it is uniformly distributed within the pores after being injected into the pores of the granular layer. The amount of the solid electrolyte solution applied is 40 to 70% by volume, 41 to 42% by volume, 43 to 44% by volume, 45 to 45% by volume, and 70 to 68% by volume, 66 to 64% by volume, 62 to 60% by volume, or 40 to 70% by volume, 42 to 64% by volume, or 45 to 60% by volume. If the amount of solid electrolyte solution applied is less than the above range, the amount of solid electrolyte solution may be insufficient and it may be difficult to uniformly distribute the solid electrolyte solution within the pores, whereas if the amount of solid electrolyte solution applied is more than the above range, the efficiency of injection of the solid electrolyte solution into the pores may decrease. Even if the solid electrolyte solution does not fill the pores of the granule layer, the solid electrolyte solution is positioned in contact with the granules due to the attractive force between the granules and the solid electrolyte, thereby improving physical contact between the granules and the solid electrolyte.

[0047] The solid electrolyte solution applied to the granular layer is evacuated to move into the gaps between the granules, i.e., into the gaps within the granular layer. As shown in FIG. 1, when the solid electrolyte solution is applied to the granular layer, gas in the gaps escapes from the gaps in direction A, and the solid electrolyte solution is injected into the gaps in direction B due to gravity. To facilitate understanding of the present invention, FIG. 2 schematically illustrates the state in which the solid electrolyte solution is injected into the gaps between the granules after evacuating according to one embodiment of the present invention. As shown in FIG. 2, even when the solid electrolyte solution is injected so that it contacts the current collector, the solid electrolyte solution may be partially exposed to the surface of the granular layer.

[0048] According to one embodiment of the present invention, the vacuum depressurization is performed at a temperature of 20°C to 40°C. The temperature during vacuum depressurization can be adjusted to a level that allows the solid electrolyte solution to have fluidity while preventing the solid electrolyte solution from drying out excessively. Specifically, the temperature is 20°C or higher, 21°C or higher, 22°C or higher, 23°C or higher, 24°C or higher, or 25°C or higher, and 40°C or lower, 39°C or lower, 38°C or lower, 37°C or lower, 36°C or lower, or 35°C or lower, and may be 20°C to 40°C, 22°C to 37°C, or 25°C to 35°C. If the temperature during vacuum depressurization is below this range, the fluidity of the solid electrolyte solution decreases, making it difficult to inject the solid electrolyte solution into the voids. If the temperature exceeds this range, the amount of solid electrolyte solution that dries out may be undesirably large.

[0049] The vacuum depressurization can be performed by placing an electrode having a granular layer coated with a solid electrolyte solution in a vacuum device. The vacuum device can be any commonly used device in the relevant technical field. According to one embodiment of the present invention, the vacuum depressurization is performed by repeating vacuum activation and depressurization periods at intervals of 5 to 15 seconds. As described above, the solid electrolyte solution is not a single component but contains solid components, a solvent, etc., so if the vacuum depressurization is performed all at once, imbalance in the solid electrolyte solution may occur, and the continuous injection of a large amount of solution may result in detachment of granules from the granular layer. However, if the depressurization period is too long, the flowability of the solution penetrating into the interior may decrease, resulting in a decrease in the final amount of solution permeated. Therefore, having a depressurization period of appropriate duration not only resolves issues such as imbalance in the solid electrolyte solution and detachment of granules, but also improves the overall efficiency of the vacuum depressurization. Specifically, the interval may be 5 to 15 seconds, 6 to 14 seconds, or 7 to 13 seconds, and may be 5 to 15 seconds, 6 to 14 seconds, or 7 to 13 seconds. If the interval is less than the above range, the time for each evacuation is too short to effectively inject the solid electrolyte solution into the voids, and if the interval is more than the above range, the effect of separating the operating and resting periods is negligible. According to one embodiment of the present invention, the evacuation is performed 3 to 10 cycles, 3 to 9 cycles, or 3 to 8 cycles, with one cycle consisting of the operating period and the resting period. Within the above cycle range, the solid electrolyte solution can be completely injected into the voids of the granular layer.

[0050] As shown in FIG. 2, the solid electrolyte solution can be completely injected into the voids of the granular layer and then dried under vacuum at elevated temperature. The drying process is a process of partially or completely removing liquid components, such as solvents, from the solid electrolyte solution. Because the solid electrolyte solution remains injected into the voids, it may not be completely dried even after high-temperature vacuum drying. However, if the drying process is performed, the liquid does not seep out of the electrode at room temperature after drying, and in this sense, such a battery can be considered an all-solid-state battery. According to one embodiment of the present invention, the drying process is performed under reduced pressure in a vacuum at 60°C to 80°C. Unlike injecting the solid electrolyte solution into the voids of the granular layer, the drying process can be performed throughout the entire operating period, rather than separately during the operating and resting periods. Specifically, the temperature is 60° C. or higher, 61° C. or higher, 62° C. or higher, 63° C. or higher, 64° C. or higher, 65° C. or higher, and 80° C. or lower, 79° C. or lower, 78° C. or lower, 77° C. or lower, 76° C. or lower, 75° C. or lower, and may be 60° C. to 80° C., 62° C. to 77° C., or 65° C. to 75° C. If the temperature during drying is below the above range, drying is not easy, and if it exceeds the above range, not only is the additional drying effect slight, but the structure of the granular layer may be deformed, which is undesirable.

[0051] According to one embodiment of the present invention, the electrode active material layer containing a solid electrolyte in the all-solid-state battery electrode after drying contains 20 wt% to 40 wt% of the solid electrolyte based on the content of the granules. Specifically, the content of the solid electrolyte is 20 wt% or more, 21 wt% or more, 22 wt% or more, 23 wt% or more, 24 wt% or more, 25 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 20 wt% to 40 wt%, 22 wt% to 37 wt%, or 25 wt% to 35 wt%. If the content of the solid electrolyte is less than this range, electron transfer between the electrolyte and the active material in the all-solid-state battery may be difficult, and significant improvement in battery performance may not be achieved. On the other hand, if the content of the solid electrolyte is greater than this range, the loading amount of the active material may be relatively reduced, and significant improvement in battery performance may not be achieved.

[0052] In one aspect of the present invention, an all-solid-state battery is provided that includes the above-described all-solid-state battery electrode in the cathode and / or anode. In constructing the all-solid-state battery, a separate solid electrolyte layer can be introduced between the cathode and anode in addition to the solid electrolyte contained in the electrodes. This solid electrolyte layer can also function as a separator in a typical lithium secondary battery. The above-described electrodes can optionally be used together with a liquid electrolyte to form a semi-solid-state battery, in which case a separate polymer separator is required.

[0053] The polymer separator is interposed between the anode and the cathode and serves to electrically insulate the anode and the cathode while allowing lithium ions to pass through. The polymer separator may be any polymer separator commonly used in the field of all-solid-state batteries, and is not particularly limited.

[0054] 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.

[0055] 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 energy storage systems.

[0056] Preferred examples are presented below to aid in understanding the present invention. However, the following examples are provided merely to facilitate understanding of the present invention, and the present invention is not limited thereto.

[0057] Example Example 1 LiNi as the active material 0.6 Co 0.2 Mn 0.2 O2 (NCM 622), carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in N-methylpyrrolidone solvent at a weight ratio of 94:3:3 (active material: conductive material: binder) to prepare a slurry, which was then spray-dried to produce granules with a diameter of approximately 60 μm (porosity: approximately 30%).

[0058] Meanwhile, the above-mentioned granules prepared in advance were applied to an approximately 100 μm aluminum current collector. An upper roll was placed on top of the granule layer, and a lower roll was placed below the current collector, and the center distance between the upper and lower rolls was adjusted to approximately 300 μm. At this time, the upper and lower rolls were at room temperature without any special heat applied, and the upper and lower rolls were moved slowly and uniformly left and right to align the granules. Thereafter, the upper and lower rolls were heated to approximately 40°C, and then moved slowly left and right in the same way to fix the granules. The energy density of the fixed granule layer was approximately 4 mAh / cm. 2 The porosity was approximately 55%. Here, the porosity of the granular layer was calculated by measuring the thickness of the granular layer using a material thickness measuring device (TESA, u-hite) and then using the true density of the granular layer measured using a material true density measuring device (Microtrac, BELPycno).

[0059] The granule layer prepared as described above was coated with a solid electrolyte solution at a volume of approximately 60% (based on the volume of the granules: approximately 27% based on the granule layer, approximately 49% based on the voids in the granule layer) and then placed in a vacuum decompression device (manufacturer: AIRZERO, product name: AZC-050) and the solid electrolyte solution was injected into the voids in the granule layer by repeating five cycles of operation and rest at approximately 10 second intervals at room temperature.Then, the inside of the vacuum decompression device was heated to approximately 70°C and dried for approximately 10 minutes to prepare a cathode for an all-solid-state battery.

[0060] Li2S-LiCl-P2S5 was then mixed with a polyvinylidene fluoride (PVDF) solution (a solution of PVDF and toluene mixed at a weight ratio of 8:92) to prepare a slurry, which was then coated on a lithium foil (Li foil) with a thickness of approximately 150 μm to prepare a solid electrolyte and a negative electrode. The positive and negative electrodes were stacked and compressed to prepare an electrode assembly, which was then placed inside a battery case to prepare an all-solid-state battery.

[0061] Comparative Example 1 An all-solid-state battery was fabricated in the same manner as in Example 1, except that the solid electrolyte solution was added to the prepared granule layer at a concentration of about 30% by volume (based on the granule layer: about 13.5%, based on the voids in the granule layer: about 24.6%) based on the volume of the granules.

[0062] Comparative Example 2 An all-solid-state battery was fabricated in the same manner as in Example 1, except that the solid electrolyte solution was added to the prepared granule layer at a concentration of about 90% by volume (based on the granule layer: about 40.5%, based on the voids in the granule layer: about 73.8%) based on the volume of the granules.

[0063] Comparative Example 3 An all-solid-state battery was manufactured in the same manner as in Example 1, except that the solid electrolyte solution was injected into the voids of the granular layer by operating the vacuum decompression device for 50 seconds without a rest period.

[0064] Experimental example: Performance evaluation of manufactured batteries The batteries prepared in Example 1 and Comparative Examples 1 to 3 were charged / discharged, and the discharge capacity (mAh / g) and coulombic efficiency (%) in the first cycle were measured and are shown in Table 1. Meanwhile, when evaluating the battery performance, charge / discharge was performed at a temperature of 60°C under the following conditions, and the discharge capacity (mAh / g) and coulombic efficiency (%) were measured.

[0065] Charging conditions: 0.05C, 4.25V CC / CV, 0.01C cut-off Discharge conditions: 0.05C, 3V

[0066] The results are shown in Table 1 below.

[0067] [Table 1]

[0068] According to Table 1, the all-solid-state battery of Example 1 exhibits superior initial coulombic efficiency and discharge capacity compared to the all-solid-state batteries of Comparative Examples 1 and 2. This indicates that, even though the solid electrolyte solution was injected using a vacuum method, the degree to which the solid electrolyte solution was injected into the voids can vary depending on the amount of solid electrolyte solution initially applied. In Comparative Example 1, it is believed that the amount of solid electrolyte solution injected into the voids was small, resulting in lower coulombic efficiency and discharge capacity. Meanwhile, in Comparative Example 2, despite injecting a sufficient amount of solid electrolyte solution compared to Example 1, the coulombic efficiency and discharge capacity were lower than in Example 1, indicating that a large amount of solid electrolyte solution is not necessarily required to achieve high coulombic efficiency and discharge capacity. In Comparative Example 2, it is believed that, despite the amount of solid electrolyte solution being sufficiently large, it was not uniformly impregnated into the voids, resulting in reduced initial battery performance.

[0069] Meanwhile, when introducing the solid electrolyte solution by vacuum, a comparison of Example 1 and Comparative Example 3 reveals that the rest period is important. Specifically, in Comparative Example 3, the vacuum was introduced without a rest period, and a large amount of solid electrolyte solution was continuously injected into the pores all at once, without allowing time for the solid electrolyte solution to naturally rearrange within the pores. This caused the structure of the granular layer to collapse, resulting in electrode detachment.

[0070] Any simple modifications or variations of the present invention belong to the scope of the present invention, and the specific scope of protection of the present invention will be defined by the appended claims. [Explanation of symbols]

[0071] 10: Current collector 20: Granules containing active material 30: Solid electrolyte solution A: Gas flow in a gap due to vacuum B: Flow of solid electrolyte solution by vacuum

Claims

1. (1) applying granules onto a current collector; (2) aligning and fixing the applied granules; (3) applying a solid electrolyte solution onto the fixed granules; and (4) allowing the applied solid electrolyte solution to migrate into the voids between the granules; the granules are spherical particles containing an active material, a conductive material, and a binder; the granules have a diameter of 30 μm to 150 μm; The method for manufacturing an electrode for an all-solid-state battery, wherein the step (4) is performed at 20 to 40° C. under reduced pressure in vacuum.

2. 2. The method of claim 1, wherein the granular layer made of the granules fixed in step (2) has a porosity of 30% to 70%.

3. 2. The method of claim 1, wherein the granular layer made of the granules fixed in step (2) has a thickness of 100 μm to 300 μm.

4. 4. The method of claim 3, wherein in step (3), the solid electrolyte solution is applied in an amount of 20 to 40 volume % based on the volume of the granular layer.

5. 4. The method of claim 3, wherein in step (3), the solid electrolyte solution is applied in an amount of 40 to 70 volume % based on the pore volume of the granular layer.

6. 2. The method of claim 1, wherein the solid electrolyte solution contains 20 to 40 wt% of a solid component based on the total weight of the solid electrolyte solution.

7. 2. The method of claim 1, wherein the step (4) repeats a vacuum application period and a rest period at intervals of 5 to 15 seconds.

8. 8. The method for manufacturing an electrode for an all-solid-state battery according to claim 7, wherein step (4) is repeated 3 to 10 cycles, with one cycle consisting of an operating period and a resting period.

9. The method for manufacturing an electrode for an all-solid-state battery according to any one of claims 1 to 8, further comprising (5) drying the electrode under reduced pressure in a vacuum at 60 to 80°C.

Images