Electrode assembly and all-solid-state battery including same

Abstract

The present invention relates to an electrode assembly and an all-solid-state battery comprising the same, and more particularly, to an electrode assembly having an optimized concave-convex structure, an all-solid-state battery comprising the same, a method for manufacturing the electrode assembly, and a method for manufacturing the all-solid-state battery. The electrode assembly of the present invention is manufactured by a wet-wet coating method, has an appropriate uneven structure, thereby being able to minimize exposure of a solid electrolyte contained in an electrode active material layer with respect to moisture, and since a binder migrates to the solid electrolyte layer, the binder in the electrode active material layer is uniformly distributed, thereby improving the reliability of the electrode assembly. Therefore, the durability and the electrochemical performance of the electrode assembly are excellent.

Description

Technical Field

[0001] The present invention relates to an electrode assembly and an all-solid-state battery including the electrode assembly, wherein the electrode assembly is manufactured using a wet-wet coating method, thereby achieving uniform distribution of an adhesive, low interfacial resistance, and preventing degradation of the electrode surface due to exposure to moisture. Background Art

[0002] Currently, various batteries are being developed to overcome the limitations of existing lithium-ion secondary batteries from the perspectives of capacity, stability, output, large-scale, and ultra-miniaturization. Among them, all-solid-state batteries use solid electrolytes instead of the electrolytes used in existing lithium-ion secondary batteries. Because these batteries do not use flammable solvents, they avoid the fires and explosions caused by electrolyte decomposition reactions in conventional batteries, significantly improving stability.

[0003] An all-solid-state battery is a stacked structure comprising a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode. The basic properties required of the solid electrolyte layer include electrical insulation to prevent short circuits between the positive and negative electrodes and ionic conductivity to allow lithium to move smoothly during charge and discharge. To this end, it is necessary to minimize the resistance at the interface between the solid electrolyte layer and the positive and negative electrodes. The main causes of resistance at the interface are: uneven interface contact, increased resistance in the upper layer of the electrode caused by migration of the binder contained in the active material layer of the electrode, and generation of an impedance in the surface layer of the electrode caused by moisture. Summary of the Invention

[0004] The object of the present invention is to provide an electrode assembly, an all-solid-state battery including the electrode assembly, and methods for manufacturing the same that can solve the above-mentioned technical problems.

[0005] More specifically, the present invention provides an electrode assembly, an all-solid-state battery including the electrode assembly, and a method for manufacturing the same that can solve the above-mentioned technical problems. The electrode assembly is manufactured using a wet-wet coating method to minimize adhesive migration and minimize the exposure of the solid electrolyte to moisture, thereby reducing the interface resistance between the electrode active material layer and the solid electrolyte layer, thereby achieving excellent durability and performance.

[0006] In order to solve the above problems, the present invention provides a novel electrode assembly, an all-solid-state battery, a method for manufacturing the above-mentioned electrode assembly, and a method for manufacturing the above-mentioned all-solid-state battery.

[0007] Specifically, (1) the present invention provides an electrode assembly comprising: an electrode, the electrode comprising an electrode collector and an electrode active material layer deposited on the electrode collector; and a solid electrolyte layer, the solid electrolyte layer deposited on the electrode active material layer, wherein the interface between the electrode active material layer and the solid electrolyte layer comprises at least two or more concave-convex structures having a height difference relative to the interface in the thickness direction of the electrode active material layer, the ten-point average roughness (Rz) of the concave-convex structure is greater than 3 μm and less than 15 μm, and when the electrode is a positive electrode, the average spacing (Sm) between the concave-convex structures is greater than 15 μm and less than 30 μm, and when the electrode is a negative electrode, the average spacing (Sm) between the concave-convex structures is greater than 22 μm and less than 30 μm.

[0008] (2) The present invention provides an electrode assembly as described in (1) above, wherein the electrode is a positive electrode, and the ten-point average roughness (Rz) of the concave-convex structure is greater than or equal to 3 μm and less than or equal to 6 μm.

[0009] (3) The electrode assembly described in (1) or (2) above provided by the present invention, wherein the electrode is a positive electrode, and the maximum roughness (Rt) of the concave-convex structure is greater than or equal to 0.5 μm and less than or equal to 15 μm.

[0010] (4) The electrode assembly described in any one of (1) to (3) above provided by the present invention, wherein the electrode is a negative electrode, and the ten-point average roughness (Rz) of the concave-convex structure is greater than 7 μm and less than 15 μm.

[0011] (5) The electrode assembly described in any one of (1) to (4) above provided by the present invention, wherein the electrode is a negative electrode, and the maximum roughness (Rt) of the concave-convex structure is greater than or equal to 5 μm and less than or equal to 20 μm.

[0012] (6) The electrode assembly described in any one of (1) to (5) above provided by the present invention is characterized in that it satisfies the following formula 1.

[0013] [Formula 1]

[0014] 0.85≤C(0) / C(L)≤1.00

[0015] C(0) represents the binder concentration value at the interface between the current collector and the electrode active material layer obtained from a binder concentration map obtained by EDS analysis of a cross section in the thickness direction of the electrode assembly.

[0016] The C(L) represents a binder concentration value at the interface between the electrode active material layer and the solid electrolyte layer, obtained from a binder concentration map obtained by EDS analysis of a cross section in the thickness direction of the electrode assembly.

[0017] (7) The electrode assembly described in any one of the above (1) to (6) provided by the present invention is characterized in that it satisfies the following formula 2.

[0018] [Formula 2]

[0019] 0.10≤Minimum value of C(x) / Maximum value of C(x)≤1.00

[0020] C(x) represents the binder concentration value at point x obtained from a binder concentration map obtained by performing EDS analysis on a cross section in the thickness direction of the electrode assembly.

[0021] (8) The electrode assembly according to any one of (1) to (7) above, wherein the electrode active material layer comprises a sulfide-based solid electrolyte.

[0022] (9) The electrode assembly described in any one of the above (1) to (8) provided by the present invention, wherein the electrode active material layer contains a solid electrolyte, and the particle size a of the solid electrolyte contained in the electrode active material layer and the particle size b of the solid electrolyte contained in the solid electrolyte layer satisfy the following formula 3.

[0023] [Formula 3]

[0024] 0.1<b / (a+b)<1.0

[0025] (10) The present invention provides an all-solid-state battery comprising an electrode assembly according to any one of (1) to (9) above.

[0026] (11) The present invention provides a method for manufacturing an electrode assembly, comprising the following steps: coating an electrode slurry on an electrode collector; coating a solid electrolyte slurry on the coated electrode slurry; and drying the electrode slurry and the solid electrolyte slurry at the same time; the ratio of the solid content of the solid electrolyte slurry to the solid content of the electrode slurry (solid content of the solid electrolyte slurry / solid content of the electrode slurry) is greater than 0.60 and less than 0.90.

[0027] (12) The present invention provides a method for manufacturing an electrode assembly as described in (11) above, wherein the viscosity ratio of the electrode slurry to the solid electrolyte slurry (electrode slurry viscosity / solid electrolyte slurry viscosity) is 2 to 4.

[0028] (13) The present invention provides a method for manufacturing an electrode assembly as described in (11) or (12) above, wherein the electrode slurry is a positive electrode slurry, and the solid content of the positive electrode slurry is 60% to 80% by weight.

[0029] (14) The present invention provides a method for manufacturing an electrode assembly as described in any one of (11) to (13) above, wherein the electrode slurry is a negative electrode slurry, and the solid content of the negative electrode slurry is 50% by weight to 70% by weight.

[0030] (15) The present invention provides a method for manufacturing an electrode assembly as described in any one of (11) to (14) above, wherein the solid content of the solid electrolyte slurry is 40 wt% to 60 wt%.

[0031] (16) The present invention provides a method for manufacturing an all-solid-state battery, comprising the following steps: coating a positive electrode slurry on a positive electrode current collector, coating a first solid electrolyte slurry on the coated slurry, and drying the positive electrode slurry and the first solid electrolyte slurry simultaneously to manufacture a positive electrode-first solid electrolyte stack; coating a negative electrode slurry on a negative electrode current collector, and coating a second solid electrolyte slurry on the coated slurry, and drying the negative electrode slurry and the second solid electrolyte slurry simultaneously to manufacture a negative electrode-second solid electrolyte stack; and The body and the negative electrode-second solid electrolyte stack are stacked in a manner that the first solid electrolyte layer and the second solid electrolyte layer are opposite to each other and rolled, wherein at least one of the ratio of the solid content of the first solid electrolyte slurry to the solid content of the positive electrode slurry (solid content of the first solid electrolyte slurry / solid content of the positive electrode slurry) and the ratio of the solid content of the second solid electrolyte slurry to the solid content of the negative electrode slurry (solid content of the second solid electrolyte slurry / solid content of the negative electrode slurry) is greater than 0.70 and less than 0.80.

[0032] Since the interface between the electrode active material layer and the solid electrolyte layer of the electrode assembly of the present invention has a concave-convex structure that meets certain conditions, the resistance of the interface between the electrode active material layer and the solid electrolyte layer is low, and the distribution of the adhesive is uniform, thereby enabling the output and durability characteristics of the all-solid-state battery including the above-mentioned electrode assembly to be excellent.

[0033] In addition, the manufacturing method of the electrode assembly of the present invention can form the electrode active material layer and the solid electrolyte layer at one time through a wet-wet coating method, thereby minimizing the migration of the adhesive and minimizing the exposure of the solid electrolyte to moisture. By optimizing the solid content ratio of the slurry used to form the above two layers, an electrode assembly with reduced interface resistance between the electrode active material layer and the fixed electrolyte layer can be manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram showing a simplified structure of the electrode assembly of the present invention.

[0035] Figure 2 A flow chart showing a method for manufacturing an electrode assembly according to the present invention.

[0036] Figure 3 A flow chart showing the method for manufacturing an all-solid-state battery according to the present invention.

[0037] Figure 4 This is a graph showing the binder concentration in the cross section of the positive electrode active material layer obtained for the all-solid-state battery of Comparative Example 3-1 of the present invention.

[0038] Figure 5 This is a graph showing the binder concentration in the cross section of the positive electrode active material layer obtained for the all-solid-state battery of Example 3-2 of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be described in more detail below.

[0040] The terms and words used in this specification and claims should not be limited to their ordinary meanings or dictionary meanings, but should be interpreted according to the term concepts defined by the inventor in order to most appropriately describe his invention, that is, they must be interpreted in a meaning and concept that is consistent with the technical idea of ​​the present invention.

[0041] On the other hand, in the present invention, the ten-point average roughness of the concavo-convex structure observed at the interface between the solid electrolyte layer and the electrode active material layer, the average interval between the concavo-convex structures, and the maximum roughness of the concavo-convex structure can be measured or calculated from an image of the interface cross section observed by a field emission scanning electron microscope (FE-SEM). More specifically, the values ​​of Rz, Sm, and Rt can be measured and calculated by the following method based on 220 μm in the longitudinal direction of the above cross section. Figure 1 The length of the portion shown in .

[0042] 1) Ten-point average roughness (Rz): calculated by adding the average height of the five highest peaks and the average depth of the five deepest valleys in the spectrum within a reference length.

[0043] 2) Average spacing between concave and convex structures (Sm): calculated as the average value of the unit concave and convex structure length (waveform element) within the reference length.

[0044] 3) Maximum roughness of the concavo-convex structure (Rt): calculated by adding the maximum peak height value and the maximum valley depth value in the spectrum within the reference length.

[0045] On the other hand, as an example of the above-mentioned field emission scanning electron microscope apparatus, SU7000 by HITACHI Corporation can be used.

[0046] Electrode assembly

[0047] The present invention provides an electrode assembly, comprising: an electrode, the electrode comprising an electrode current collector and an electrode active material layer deposited on the electrode current collector; and a solid electrolyte layer deposited on the electrode active material layer. The interface between the electrode active material layer and the solid electrolyte layer observed by a scanning electron microscope image of a cross section in the thickness direction of the electrode assembly comprises at least two or more concave-convex structures having a height difference relative to the interface in the thickness direction of the electrode active material layer, the ten-point average roughness (Rz) of the concave-convex structures being greater than or equal to 3μm and less than or equal to 15μm, and when the electrode is a positive electrode, the average spacing (Sm) between the concave-convex structures being greater than or equal to 15μm and less than or equal to 30μm, and when the electrode is a negative electrode, the average spacing (Sm) between the concave-convex structures being greater than or equal to 22μm and less than or equal to 30μm.

[0048] Electrode current collector

[0049] The electrode current collector is required to be a material having electrical conductivity and a certain level of durability. More specifically, it may include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel, or materials surface-treated with carbon, nickel, titanium, silver, or the like, and / or an aluminum-cadmium alloy. Furthermore, the electrode current collector may be in the form of a film, sheet, foil, mesh, porous body, foam, non-woven fabric, or the like, so that a layer of electrode active material is uniformly formed on its surface.

[0050] The thickness of the current collector may be 10 μm to 20 μm, preferably 10 μm to 15 μm. When the thickness of the current collector is within the above range, the durability and performance of the electrode can be more balanced and excellent.

[0051] Electrode active material layer

[0052] The electrode active material layer is formed on the electrode current collector. The specific active material used may vary depending on the type of the electrode.

[0053] More specifically, in the case where the electrode is a positive electrode, the positive electrode active material may be an oxide active material or a sulfide active material.

[0054] The above oxide active materials can be LiCoO2, LiMnO2, LiNiO2, LiVO2, Li 1+x Ni 1 / 3 Co1 / 3 Mn 1 / 3 O2 and other rock salt layer active materials; LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4 and other spinel active materials; LiNiVO4, LiCoVO4 and other inverse spinel active materials; LiFePO4, LiMnPO4, LiCoPO4, LiNiPO4 and other olivine active materials; Li2FeSiO4, Li2MnSiO4 and other silicon-containing active materials; LiNi 0.8 Co( 0.2-x )Al x O2 (0<x<0.2) and other rock salt layer type active materials in which a part of the transition metal is replaced by different metals; Li 1+x Mn 2-x-y M y Spinel-type active materials in which a portion of transition metals such as O4 (M is at least one of Al, Mg, Co, Fe, Ni, and Zn, 0<x+y<2) are replaced by different metals; Li4Ti5O 12 The above-mentioned sulfide active material can be Chevrel phase copper, iron sulfide, cobalt sulfide, nickel sulfide, etc.

[0055] On the other hand, when the above-mentioned electrode is a negative electrode, the negative electrode active material may be a carbon active material or a metal active material.

[0056] The carbon active material may be graphite such as mesocarbon microbeads (MCMB) and highly oriented pyrolytic graphite (HOPG), or amorphous carbon such as hard carbon and soft carbon. The metal active material may be In, Al, Si, Sn, or alloys containing at least one of these elements.

[0057] The electrode active material layer may contain a binder along with the active material. The binder is a component that can bind the components contained in the electrode active material layer to each other. The electrode active material layer of the electrode assembly of the present invention is characterized in that the binder migrates to the solid electrolyte layer described later during the wet-wet coating manufacturing process, so the binder is evenly distributed within the electrode active material layer. As the type of the binder, BR (Butadiene rubber), NBR (Nitrile butadiene rubber), HNBR (Hydrogenated nitrile butadiene rubber), PVDF (polyvinylidene difluoride), PTFE (polytetrafluoroethylene), CMC (carboxymethylcellulose), etc. can be used.

[0058] The electrode active material layer may include a conductive material to ensure the conductivity of the electrode active material layer, and the conductive material may include carbon black, conductive graphite, ethylene black, graphene, etc.

[0059] The electrode active material layer may include a solid electrolyte. More specifically, the solid electrolyte may be an oxide-based solid electrolyte or a sulfide-based solid electrolyte, preferably a sulfide-based solid electrolyte. The lithium ion conductivity of the solid electrolyte may be 0.3 mS / cm or more. Sulfide-based solid electrolytes have the advantage of high lithium ion conductivity, but have the disadvantage of being easily affected by moisture. However, in the case of using a wet-wet coating method in the electrode assembly manufacturing method of the present invention, it is possible to minimize the exposure of the solid electrolyte contained in the electrode active material layer to moisture.

[0060] The above-mentioned sulfide-based solid electrolyte is not particularly limited and may include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (wherein m and n are positive integers and Z is one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive integers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li 10 GeP2S 12 wait.

[0061] The content of the active material in the electrode active material layer may be 75% to 85% by weight, preferably 80% to 83% by weight. Furthermore, the content of the binder may be 1% to 3% by weight, preferably 1.5% to 2% by weight. Furthermore, the content of the conductive material may be 1% to 3% by weight, preferably 1.5% to 2% by weight. Furthermore, the content of the solid electrolyte may be 15% to 25% by weight, preferably 17% to 20% by weight.

[0062] The thickness of the electrode active material layer may be 70 μm to 90 μm, and preferably 75 μm to 80 μm.

[0063] Solid electrolyte layer

[0064] The electrode assembly of the present invention includes a solid electrolyte layer deposited on the electrode active material layer described above. The solid electrolyte layer may include the same binder and solid electrolyte as described above. More preferably, the solid electrolyte layer may include a sulfide-based solid electrolyte.

[0065] The thickness of the solid electrolyte layer may be 20 μm to 60 μm, and preferably 30 μm to 40 μm.

[0066] Interface between electrode active material layer and solid electrolyte layer

[0067] In the electrode assembly provided by the present invention, the interface between the electrode active material layer and the solid electrolyte layer includes at least two or more concave-convex structures having a height difference relative to the above-mentioned interface in the thickness direction of the above-mentioned electrode active material layer, and the ten-point average roughness (Rz) of the above-mentioned concave-convex structures is greater than 3 μm and less than 15 μm. When the above-mentioned electrode is a positive electrode, the average spacing (Sm) between the above-mentioned concave-convex structures is greater than 15 μm and less than 30 μm. When the above-mentioned electrode is a negative electrode, the average spacing (Sm) between the above-mentioned concave-convex structures is greater than 22 μm and less than 30 μm.

[0068] The above-mentioned concavo-convex structure can be formed using a wet-on-wet coating method described later. The electrode assembly provided by the present invention has such a concavo-convex structure, resulting in low resistance at the interface and excellent durability. More specifically, the average roughness of the concavo-convex structure and the average spacing between the concavo-convex structures of the electrode assembly of the present invention meet specific conditions, thereby achieving excellent bonding between the electrode active material layer and the solid electrolyte layer and reducing interface resistance.

[0069] On the other hand, the preferred form of the above-mentioned concave-convex structure may be different depending on the type of electrode. Specifically, the average spacing between the concave-convex structures may be different when the above-mentioned electrode is a positive electrode and when it is a negative electrode. When the above-mentioned electrode is a positive electrode, the average spacing (Sm) between the concave-convex structures may be greater than 15 μm and less than 30 μm, more specifically, greater than 15 μm, greater than 16 μm, greater than 17 μm or greater than 18 μm, and less than 30 μm, less than 27 μm, less than 25 μm, less than 23 μm or less than 21 μm. When the above-mentioned electrode is a negative electrode, the average spacing (Sm) between the concave-convex structures is greater than 22 μm, greater than 22.5 μm or greater than 23 μm, and less than 30 μm, less than 28 μm, less than 27 μm or less than 26 μm.

[0070] In addition, the ten-point average roughness (Rz) of the above-mentioned concave-convex structure may also be different in part of the preferred range depending on the type of electrode. Specifically, when the above-mentioned electrode is a positive electrode, the ten-point average roughness (Rz) of the concave-convex structure may be greater than 3 μm, greater than 4 μm or greater than 5 μm, and less than 6 μm. On the other hand, when the above-mentioned electrode is a negative electrode, the ten-point average roughness (Rz) of the concave-convex structure may be greater than 7 μm, greater than 8 μm, greater than 9 μm or greater than 10 μm, and less than 15 μm, less than 14 μm or less than 13 μm.

[0071] The maximum roughness (Rt) of the concave-convex structure may also vary depending on the type of electrode. When the electrode is a positive electrode, the maximum roughness (Rt) of the concave-convex structure may be greater than 0.5 μm and less than 15 μm. More preferably, the maximum roughness (Rt) of the concave-convex structure may be greater than 0.5 μm, greater than 1 μm, greater than 2 μm, greater than 3 μm, greater than 4 μm, greater than 5 μm or greater than 6 μm, and less than 15 μm, less than 14 μm, less than 13 μm, less than 12 μm or less than 11 μm. On the other hand, when the electrode is a negative electrode, the maximum roughness (Rt) of the concave-convex structure may be greater than 5 μm, greater than 7 μm, greater than 9 μm, greater than 10 μm, greater than 12 μm, greater than 14 μm or greater than 15 μm, and less than 20 μm, less than 19 μm or less than 18.5 μm.

[0072] The reason why the specific structure of the concave-convex structure described above is different depending on the type of electrode is that the size of the active material particles contained in the electrode active material layer is different depending on whether the electrode is a positive electrode or a negative electrode, and the content of the solid electrolyte used in the electrode active material layer is different depending on whether the electrode is a positive electrode or a negative electrode. More specifically, the negative electrode active material generally has a larger particle size than the positive electrode active material, and the electrolyte content in the positive electrode is less than the electrolyte content in the negative electrode, so the concave-convex structure of the interface in the positive electrode and the interface in the negative electrode may be slightly different. On the other hand, the scanning electron microscope used to observe the above-mentioned concave-convex structure can use conventional equipment, for example, the SU7000 type equipment of HITACHI Corporation can be used.

[0073] On the other hand, the electrode assembly provided by the present invention may be characterized by satisfying the following formula 1.

[0074] [Formula 1]

[0075] 0.85≤C(0) / C(L)≤1.00

[0076] The above C(0) represents the binder concentration value at the interface between the collector and the electrode active material layer obtained from the binder concentration diagram obtained by EDS analysis of the cross section in the thickness direction of the electrode assembly, and the above C(L) represents the binder concentration value at the interface between the electrode active material layer and the solid electrolyte layer obtained from the binder concentration diagram obtained by EDS analysis of the cross section in the thickness direction of the electrode assembly.

[0077] The above formula 1 indicates that the ratio of the binder concentration value at the interface between the current collector and the electrode active material layer to the binder concentration value at the interface between the electrode active material layer and the solid electrolyte layer is greater than 0.85 and less than 1.00, that is, the concentration of the binder is uniform throughout the electrode active material layer. If the electrode active material layer and the solid electrolyte layer are formed by the existing double-layer coating or transfer method, the binder will migrate, resulting in a significant increase in the binder concentration value at the above interface. In this case, the C(0) / C(L) value may be less than 0.85. In the electrode assembly of the present invention, the above C(0) / C(L) value can be greater than 0.85, greater than 0.87, greater than 0.88, greater than 0.89 or greater than 0.90, and less than 1.00, less than 0.97, less than 0.95 or less than 0.93.

[0078] In addition, the electrode assembly provided by the present invention may be characterized by satisfying the following formula 2.

[0079] [Formula 2]

[0080] 0.10≤Minimum value of C(x) / Maximum value of C(x)≤1.00

[0081] The above C(x) represents the binder concentration value at point x obtained from a binder concentration map obtained by EDS analysis of a cross section in the thickness direction of the electrode assembly.

[0082] The above formula 2, like the above formula 1, indicates that the electrode active material layer contained in the electrode assembly of the present invention has a uniform binder concentration. Since the binder migrates to the solid electrolyte layer during the wet-wet coating process in the electrode assembly of the present invention, the ratio of the minimum to the maximum binder concentration of the electrode active material layer is low. However, for the electrode assembly manufactured using the existing method, as the binder migrates, the binder concentration in the electrode active material layer changes significantly, so the minimum value of C(x) / the maximum value of C(x) does not reach 0.10.

[0083] Alternatively, the binder concentration graph C(x) may be a graph obtained by measuring the distribution of a specific element contained in the binder using EDS analysis, using an image of a cross section of the electrode active material layer obtained using field emission scanning electron microscopy (FE-SEM). The distribution is then expressed based on values ​​along the length of the cross section. For example, when the binder is polyvinylidene fluoride (PVDF), the specific element may be fluorine (F).

[0084] In the electrode assembly provided by the present invention, the electrode active material layer contains a solid electrolyte, and the particle size a of the solid electrolyte contained in the electrode active material layer and the particle size b of the solid electrolyte contained in the solid electrolyte layer can satisfy the following formula 3.

[0085] [Formula 3]

[0086] 0.1<b / (a+b)<1.0

[0087] When the particle size of the solid electrolyte contained in the electrode active material layer and the particle size of the solid electrolyte contained in the solid electrolyte layer satisfy the above formula 3, there is a technical advantage of being able to suppress electrode degradation due to moisture. The above b / (a+b) value can be greater than 0.1 or 0.12 or more, and less than 1.0, 0.9 or less, 0.8 or less, 0.7 or less, or 0.65 or less.

[0088] The electrode assembly provided by the present invention can be a positive electrode assembly or a negative electrode assembly.

[0089] All-solid-state batteries

[0090] The present invention provides an all-solid-state battery comprising the electrode assembly described above.

[0091] More specifically, the all-solid-state battery may include a positive electrode assembly and a negative electrode assembly according to the present invention. In this case, the all-solid-state battery may have a structure in which the positive electrode assembly and the negative electrode assembly are stacked in such a manner that the solid electrolyte layer of the positive electrode assembly faces the solid electrolyte layer of the negative electrode assembly.

[0092] On the other hand, the all-solid-state battery may also include only one of the positive electrode assembly and the negative electrode assembly according to the present invention. In this case, the opposite electrode of the electrode assembly can be manufactured using conventional methods.

[0093] More specifically, when the all-solid-state battery of the present invention includes the cathode assembly based on the present invention, the anode can be manufactured by conventional methods, and the anode may or may not include a solid electrolyte layer on the anode active material layer.

[0094] In contrast, when the all-solid-state battery of the present invention includes the negative electrode assembly according to the present invention, the positive electrode can be manufactured by conventional methods, and the positive electrode may or may not include a solid electrolyte layer on the positive electrode active material layer.

[0095] Method for manufacturing electrode assembly

[0096] The present invention provides a method for manufacturing the electrode assembly described above. The wet-wet coating method used in the manufacture of the electrode assembly of the present invention is as follows: after applying the slurry composition for forming the active material layer on the substrate, the electrolyte slurry composition for forming the solid electrolyte layer is applied thereon again without drying, and then dried together, thereby forming the active material layer and the solid electrolyte layer at one time. In the wet-wet coating method, interlayer stirring will occur at the interface between the active material layer and the solid electrolyte layer, and the adhesive will migrate to the solid electrolyte layer, so the adhesive concentration in the electrode surface layer is reduced compared to the existing coating method, thereby obtaining an electrode assembly with a uniform adhesive distribution in the active material layer. In addition, since the process is carried out in a state where the electrode active material layer is covered by the solid electrolyte layer, the exposure of the electrode active material layer to moisture can be minimized, thereby suppressing the degradation of the electrode active material layer caused by moisture.

[0097] More specifically, the present invention provides a method for manufacturing an electrode assembly, such as Figure 2 As shown, the method comprises the following steps: applying an electrode slurry on an electrode current collector; applying a solid electrolyte slurry on the applied slurry; and simultaneously drying the electrode slurry and the solid electrolyte slurry. The ratio of the solid content of the solid electrolyte slurry to the solid content of the electrode slurry (solid electrolyte slurry solid content / electrode slurry solid content) is 0.60 or more and 0.90 or less.

[0098] In the electrode assembly manufacturing method of the present invention, it was confirmed that the concave-convex structure formed when the solid content ratio of the electrode slurry to the solid electrolyte slurry is within a certain range is more ideal. In particular, the ratio of the solid content of the solid electrolyte slurry to the solid content of the electrode slurry (solid electrolyte slurry solid content / electrode slurry solid content) can be 0.60 or more, 0.65 or more, or 0.70 or more, and 0.90 or less, 0.85 or less, or 0.80 or less. Electrode assemblies manufactured with too low or too high a solid content ratio of the slurry may experience problems such as increased interface resistance or decreased durability.

[0099] In the electrode assembly manufacturing method of the present invention, the ratio of the viscosity of the electrode slurry to the viscosity of the solid electrolyte slurry (electrode slurry viscosity / solid electrolyte slurry viscosity) can be 2 to 4, preferably 2 or more or 2.5 or more, and 4 or less or 3.5 or less. If the viscosity ratio of the two slurries is not appropriate, the following problems may occur during the application of the solid electrolyte slurry after the electrode slurry: the lower electrode slurry is squeezed and displaced, or the two slurries are mixed, causing the active material layer to separate from the lower layer.

[0100] On the other hand, the solid content of the above-mentioned electrode slurry may vary depending on the type of electrode. More specifically, when the above-mentioned electrode slurry is a positive electrode slurry, its solid content may be 60 wt % to 80 wt %, more preferably 60 wt % or more or 65 wt % or less, and 80 wt % or less or 75 wt % or less.

[0101] When the electrode slurry is a negative electrode slurry, its solid content may be 50 wt % to 70 wt %, preferably 50 wt % or 55 wt % or more and 70 wt % or 65 wt % or less.

[0102] In order to increase the energy density, the thickness of the positive electrode needs to be increased. In order to increase the thickness of the positive electrode, the solid content of the slurry needs to be increased to minimize the formation of cracks when the electrode is dried. Therefore, the solid content of the positive electrode slurry is preferably higher than that of the negative electrode slurry.

[0103] In addition, the solid content of the solid electrolyte slurry can be 40% to 60% by weight, preferably 40% or 45% or more by weight, and 60% or 55% or less by weight. When the solid content of the solid electrolyte slurry is within the above range, the solid electrolyte layer can be formed more easily.

[0104] Meanwhile, the coating and drying in this step can be performed using conventional methods. The drying temperature may vary depending on the slurry solvent, but is typically performed at 80°C to 100°C. The coating method is not limited to a specific method, as long as uniform coating of the slurry is achieved. For example, the coating can be performed using a doctor blade.

[0105] Manufacturing method of all-solid-state battery

[0106] The present invention provides a method for manufacturing an all-solid-state battery, comprising a process of manufacturing a positive electrode assembly and a negative electrode assembly using the above-mentioned method for manufacturing an electrode assembly.

[0107] More specifically, if Figure 3As shown, the manufacturing method of the all-solid-state battery of the present invention includes the following steps: coating a positive electrode slurry on a positive electrode collector, and coating a first solid electrolyte slurry on the coated slurry, and then drying the above-mentioned positive electrode slurry and the first solid electrolyte slurry at the same time to manufacture a positive electrode-first solid electrolyte stack; coating a negative electrode slurry on a negative electrode collector, and coating a second solid electrolyte slurry on the coated slurry, and then drying the above-mentioned negative electrode slurry and the second solid electrolyte slurry at the same time to manufacture a negative electrode-second solid electrolyte stack; and stacking the above-mentioned positive electrode-first solid electrolyte stack and the negative electrode-second solid electrolyte stack in a manner that the first solid electrolyte layer and the second solid electrolyte layer are opposite to each other, and rolling. At least one of the ratio of the solid content of the first solid electrolyte slurry to the solid content of the positive electrode slurry (solid content of the first solid electrolyte slurry / solid content of the positive electrode slurry) and the ratio of the solid content of the second solid electrolyte slurry to the solid content of the negative electrode slurry (solid content of the second solid electrolyte slurry / solid content of the negative electrode slurry) is greater than 0.70 and less than 0.80.

[0108] As described above, when the positive electrode assembly and the negative electrode assembly of the present invention are stacked with the solid electrolyte layers facing each other, an all-solid-state battery can be manufactured. The contents applicable to the manufacturing method of the electrode assembly provided by the present invention are also applicable to the manufacturing method of the all-solid-state battery described above.

[0109] The present invention will be further described in detail below by way of examples. However, the following examples are only for illustrating the present invention and are not intended to limit the scope of the present invention to these examples.

[0110] <Electrode Assembly Manufacturing>

[0111] Example 1-1. Manufacturing of negative electrode assembly

[0112] Azirodite sulfide solid electrolyte was used as the solid electrolyte, hexylbutylate was used as the solvent, and carbon black was used as the conductive material. The solid electrolyte, solvent, conductive material, and dispersant were mixed and mixed for the first time using a PD mixer. Then, a binder solution (PVDF) was added and mixed for the second time using a PD mixer. Finally, a carbon-based active material was added as the negative electrode active material and the final mixing was performed to produce the negative electrode slurry. It was confirmed that the solid content of the produced negative electrode slurry was 62% by weight and the viscosity was 5,780 cP (temperature: 23°C).

[0113] Separately, the same solid electrolyte, solvent, binder solution, and dispersant as above were mixed and mixed using a PD mixer to produce a solid electrolyte slurry. The solid content of the produced solid electrolyte slurry was confirmed to be 49% by weight, and the viscosity was 2,720 cP (temperature: 23°C). The ratio of the solid content of the produced solid electrolyte slurry to the solid content of the negative electrode slurry was approximately 0.790.

[0114] The negative electrode slurry prepared previously was applied to the nickel negative electrode current collector using a doctor blade, and the solid electrolyte slurry was applied again using a doctor blade. The slurry was then dried at 90°C for 15 minutes and vacuum-dried at 100°C for 4 hours to produce the negative electrode assembly.

[0115] Comparative Example 1-1. Production of negative electrode assembly

[0116] The negative electrode assembly was manufactured in the same manner as in Example 1-1, except that the solid content of the solid electrolyte slurry was changed so that the solid content of the solid electrolyte slurry / the solid content of the negative electrode slurry was 1.0.

[0117] Comparative Example 1-2. Preparation of negative electrode assembly

[0118] The negative electrode slurry used in Example 1-1 was applied to nickel as a negative electrode current collector using a doctor blade, and then dried at 90° C. for 15 minutes and vacuum-dried at 100° C. for 4 hours to produce a negative electrode assembly.

[0119] Example 2-1. Manufacturing of positive electrode assembly

[0120] A sulfide-based solid electrolyte of the argyrodite type was used as the solid electrolyte, hexyl butyrate was used as the solvent, and carbon black was used as the conductive material. The solid electrolyte, solvent, conductive material, and dispersant were mixed and mixed for the first time using a PD mixer. Then, a binder solution (PVDF) was added and mixed for the second time using a PD mixer. Finally, an NCM-based positive electrode active material was added and mixed for the final time to produce a positive electrode slurry. It was confirmed that the solid content of the produced positive electrode slurry was 70.5% by weight and the viscosity was 5,000 cP (temperature: 23°C).

[0121] In addition, another type of argyrodite-type sulfide solid electrolyte was mixed with the same solvent, binder solution, and dispersant as above and mixed using a PD mixer to produce a solid electrolyte slurry. The b / (a+b) value calculated from the particle size a of the solid electrolyte contained in the above-mentioned positive electrode slurry and the particle size b of the solid electrolyte contained in the above-mentioned solid electrolyte slurry was confirmed to be 0.6. The solid content of the produced solid electrolyte slurry was 49% by weight and the viscosity was 2,720 cP (temperature: 23°C). The value of the solid content content of the produced solid electrolyte slurry / the solid content content of the positive electrode slurry was approximately 0.695.

[0122] The positive electrode slurry prepared above was applied to aluminum as a positive electrode current collector using a doctor blade, and the solid electrolyte slurry was applied again on top using a doctor blade. The mixture was then dried at 90°C for 15 minutes and vacuum-dried at 100°C for 4 hours to produce a positive electrode assembly.

[0123] Example 2-2. Manufacturing of positive electrode assembly

[0124] A sulfide-based solid electrolyte of the argyrodite type was used as the solid electrolyte, hexyl butyrate was used as the solvent, and carbon black was used as the conductive material. The solid electrolyte, solvent, conductive material, and dispersant were mixed and mixed for the first time using a PD mixer. Then, a binder solution (PVDF) was added and mixed for the second time using a PD mixer. Finally, an NCM-based positive electrode active material was added and mixed for the final time to produce a positive electrode slurry. It was confirmed that the solid content of the produced positive electrode slurry was 70.5% by weight and the viscosity was 6,000 cP (temperature: 23°C).

[0125] In addition, another type of argyrodite-type sulfide solid electrolyte was mixed with the same solvent, binder solution, and dispersant as above and mixed using a PD mixer to produce a solid electrolyte slurry. The b / (a+b) value calculated from the particle size a of the solid electrolyte contained in the above-mentioned positive electrode slurry and the particle size b of the solid electrolyte contained in the above-mentioned solid electrolyte slurry was confirmed to be 0.125. The solid content of the produced solid electrolyte slurry was 49% by weight and the viscosity was 2,720 cP (temperature: 23°C). The value of the solid content content of the produced solid electrolyte slurry / the solid content content of the positive electrode slurry was approximately 0.695.

[0126] The positive electrode slurry prepared above was applied to aluminum as a positive electrode collector using a doctor blade, and the above solid electrolyte slurry was applied again thereon using a doctor blade, followed by drying at 90° C. for 15 minutes and vacuum drying at 100° C. for 4 hours to prepare a positive electrode assembly.

[0127] Comparative Example 2-1. Production of positive electrode assembly

[0128] The positive electrode slurry used in Example 2-1 was coated on aluminum as a positive electrode current collector using a doctor blade, and then dried at 90° C. for 15 minutes and vacuum-dried at 100° C. for 4 hours to produce a positive electrode assembly.

[0129] Comparative Example 2-2. Production of positive electrode assembly

[0130] The positive electrode slurry used in Example 2-2 was coated on aluminum as a positive electrode current collector using a doctor blade, and then dried at 90° C. for 15 minutes and vacuum-dried at 100° C. for 4 hours to produce a positive electrode assembly.

[0131] Manufacturing of all-solid-state batteries

[0132] The solid electrolyte layers of the positive and negative electrode assemblies prepared in the above-mentioned examples and comparative examples were stacked and rolled relative to each other to produce an all-solid-state battery. The electrode assemblies used in each example or comparative example are summarized in Table 1 below.

[0133]

Table 1

[0134]

[0135]

[0136] Experimental Example 1. Confirmation of the characteristics of the interface concave-convex structure

[0137] The thickness-direction cross-sections of the positive and negative electrode assemblies produced in the above-described embodiments and comparative examples were observed using a scanning electron microscope. The ten-point average roughness (Rz) of the concavo-convex structure, the average spacing between the concavo-convex structures (Sm), and the maximum roughness (Rt) of the concavo-convex structure were determined from the observed images. The results for the negative electrode assembly are summarized in Table 2, and the results for the positive electrode assembly are summarized in Table 3.

[0138]

Table 2

[0139] Rz(μm) Rt(μm) Sm(μm) Example 1-1 11.04 16.54 23.56 Comparative Example 1-1 16.01 23.2 33.34 Comparative Example 1-2 7.83 6.2 21.32

[0140]

Table 3

[0141] Rz(μm) Rt(μm) Sm (μm) Example 2-1 5.56 6.42 19.12 Example 2-2 5.3 10.5 18.1 Comparative Example 2-1 2.99 0.49 31.92 Comparative Example 2-2 2.99 0.49 31.92

[0142] As shown in Tables 2 and 3 above, for the negative electrode assembly of Comparative Example 1-1, which is not manufactured by the manufacturing method of the present invention and in which the ratio of the solid content of the solid electrolyte slurry to the solid content of the electrode slurry is too large during the wet-wet coating process, it is confirmed that the ten-point average roughness, maximum roughness and average spacing of its concave-convex structure are higher than those of the electrode assembly of the present invention; for the negative electrode assembly of Comparative Example 1-2 or the positive electrode assembly of Comparative Example 2-1, which are manufactured by conventional methods without using wet-wet coating, it is confirmed that the ten-point average roughness, maximum roughness and average spacing of the concave-convex structure are lower than those of the electrode assembly of the present invention compared with the negative electrode assembly and positive electrode assembly of the embodiment of the present invention.

[0143] It can be seen from this that in order to form the optimal concave-convex structure required by the present invention, it is not enough to simply use the wet-wet coating method. The solid content of the electrode slurry and solid electrolyte slurry coated by the wet-wet coating method must be controlled within an appropriate range. As described later, the electrode assembly that meets the concave-convex structure required by the present invention can exhibit excellent electrochemical properties.

[0144] Experimental Example 2. Electrochemical Performance Evaluation of All-Solid-State Batteries

[0145] The electrochemical performance of the all-solid-state batteries of Examples 3-1 to 3-4 and Comparative Examples 3-1 and 3-2 was evaluated.

[0146] Specifically, the all-solid-state battery was charged and discharged for the first two cycles at a voltage of 2.0 to 4.25 V, a current of 0.2 C (8.6 mA), and a temperature of 30°C. It was then charged and discharged at 0.33 C (14.2 mA) for rate evaluation. Thereafter, it was charged and discharged at a rate of 0.2 C, and the capacity retention rate was measured for durability evaluation. In the all-solid-state battery of Comparative Example 3-1, a hard short circuit occurred, making it impossible to perform charge and discharge operations. The results are summarized in Tables 4 and 5 below.

[0147]

Table 4

[0148]

[0149]

Table 5

[0150]

[0151] It can be confirmed from Tables 4 and 5 above that the all-solid-state batteries of Examples 3-1 to 3-4 using the electrode assembly of the present invention exhibit lower resistance and better durability than the all-solid-state battery of Comparative Example 3-2 using the electrode assembly of the Comparative Example.

[0152] Experimental Example 3. Confirmation of Adhesive Concentration Distribution

[0153] In the all-solid-state batteries of Comparative Example 3-1 and Example 3-2, the binder concentration diagrams at the positive electrode active material layer and the interface between the positive electrode active material layer and the solid electrolyte are obtained, respectively. Figure 4 and Figure 5 More specifically, the binder concentration graph C(x) is a graph showing the distribution of fluorine contained in the PVDF binder along the length of the cross-section, obtained by field emission scanning electron microscopy (FE-SEM). The graph shows the distribution of fluorine in the cross-section of the electrode active material layer using EDS analysis. Furthermore, the binder concentration values ​​in the cross-section of the positive electrode active material layer for Comparative Example 3-1 and Example 3-2 were calculated as relative values ​​and summarized in Table 6 below.

[0154]

Table 6

[0155]

[0156] Depend on Figure 4 and Figure 5 Comparison of the results and Table 6 above confirms that the all-solid-state battery based on the embodiment of the present invention exhibits a uniform binder distribution in the positive electrode active material layer region. In contrast, the all-solid-state battery based on the comparative example shows a result in which the binder concentration increases with distance from the current collector. In other words, in the all-solid-state battery of the comparative example, binder migration occurs within the positive electrode active material layer, resulting in a significant increase in the binder concentration in the outermost positive electrode active material layer. In contrast, in the all-solid-state battery of the embodiment, the binder in the positive electrode active material layer migrates to the solid electrolyte layer, resulting in a uniform binder distribution within the positive electrode active material layer.

[0157] This confirmed that the all-solid-state battery of the present invention has a uniform binder distribution within the active material layer, and thus has excellent electrochemical characteristics.

Claims

1. An electrode assembly comprising: electrode, The electrode comprises an electrode current collector and an electrode active material layer deposited on the electrode current collector; and a solid electrolyte layer deposited on the electrode active material layer, wherein The interface between the electrode active material layer and the solid electrolyte layer includes at least two or more concave-convex structures having a height difference relative to the interface in the thickness direction of the electrode active material layer. The ten-point average roughness of the concavo-convex structure is 3 μm or more and 15 μm or less. When the electrode is a positive electrode, the average interval between the concavo-convex structures is 15 μm or more and 30 μm or less. When the electrode is a negative electrode, an average interval between the concavo-convex structures is 22 μm or more and 30 μm or less.

2. The electrode assembly according to claim 1, wherein The electrode is a positive electrode, and the ten-point average roughness of the concavo-convex structure is greater than or equal to 3 μm and less than or equal to 6 μm.

3. The electrode assembly according to claim 1, wherein The electrode is a positive electrode, and the maximum roughness of the concavo-convex structure is greater than or equal to 0.5 μm and less than or equal to 15 μm.

4. The electrode assembly according to claim 1, wherein The electrode is a negative electrode, and the ten-point average roughness of the concavo-convex structure is greater than or equal to 7 μm and less than or equal to 15 μm.

5. The electrode assembly according to claim 1, wherein The electrode is a negative electrode, and the maximum roughness of the concavo-convex structure is greater than or equal to 5 μm and less than or equal to 20 μm.

6. The electrode assembly according to claim 1, wherein: Satisfies the following formula 1: [Formula 1] 0.85≤C(0) / C(L)≤1.00 Wherein, C(0) represents the binder concentration value at the interface between the current collector and the electrode active material layer obtained from a binder concentration map obtained by EDS analysis of a cross section in the thickness direction of the electrode assembly, The C(L) represents a binder concentration value at the interface between the electrode active material layer and the solid electrolyte layer, obtained from a binder concentration map obtained by EDS analysis of a cross section in the thickness direction of the electrode assembly.

7. The electrode assembly according to claim 1, wherein: Satisfies the following formula 2: [Formula 2] 0.10≤Minimum value of C(x) / Maximum value of C(x)≤1.00 Here, C(x) represents the binder concentration value at point x obtained from a binder concentration map obtained by performing EDS analysis on a cross section in the thickness direction of the electrode assembly.

8. The electrode assembly according to claim 1, wherein The electrode active material layer includes a sulfide-based solid electrolyte.

9. The electrode assembly according to claim 1, wherein The electrode active material layer comprises a solid electrolyte, The particle size a of the solid electrolyte contained in the electrode active material layer and the particle size b of the solid electrolyte contained in the solid electrolyte layer satisfy the following formula 3: [Formula 3] 0.1<b / (a+b)<1.

0. 10 . An all-solid-state battery comprising the electrode assembly according to claim 1 .

11. A method for manufacturing an electrode assembly, comprising the following steps: coating the electrode slurry on the electrode collector; coating a solid electrolyte slurry on the coated electrode slurry; and drying the electrode slurry and the solid electrolyte slurry simultaneously, The ratio of the solid content of the solid electrolyte slurry to the solid content of the electrode slurry, that is, solid electrolyte slurry solid content / electrode slurry solid content, is 0.60 or more and 0.90 or less.

12. The method for manufacturing an electrode assembly according to claim 11, wherein: The ratio of the viscosity of the electrode slurry to the viscosity of the solid electrolyte slurry, ie, electrode slurry viscosity / solid electrolyte slurry viscosity, is 2 to 4.

13. The method for manufacturing an electrode assembly according to claim 11, wherein: The electrode slurry is a positive electrode slurry, The solid content of the positive electrode slurry is 60 wt % to 80 wt %.

14. The method for manufacturing an electrode assembly according to claim 11, wherein: The electrode slurry is a negative electrode slurry, The solid content of the negative electrode slurry is 50 wt % to 70 wt %.

15. The method for manufacturing an electrode assembly according to claim 11, wherein: The solid electrolyte slurry has a solid content of 40 wt % to 60 wt %.

16. A method for manufacturing an all-solid-state battery, comprising the following steps: Applying a positive electrode slurry on a positive electrode current collector, applying a first solid electrolyte slurry on the applied slurry, and then drying the positive electrode slurry and the first solid electrolyte slurry simultaneously to produce a positive electrode-first solid electrolyte stack; coating a negative electrode slurry on a negative electrode current collector, and coating a second solid electrolyte slurry on the coated slurry, and then drying the negative electrode slurry and the second solid electrolyte slurry simultaneously to produce a negative electrode-second solid electrolyte stack; and The positive electrode-first solid electrolyte stack and the negative electrode-second solid electrolyte stack are stacked in a manner such that the first solid electrolyte layer and the second solid electrolyte layer face each other, and rolled. Among them, at least one of the ratio of the solid content of the first solid electrolyte slurry to the solid content of the positive electrode slurry, that is, the solid content of the first solid electrolyte slurry / the solid content of the positive electrode slurry, and the ratio of the solid content of the second solid electrolyte slurry to the solid content of the negative electrode slurry, that is, the solid content of the second solid electrolyte slurry / the solid content of the negative electrode slurry is greater than 0.70 and less than 0.80.

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