Positive electrode for all-solid-state battery, and all-solid-state battery comprising same

Abstract

The present invention relates to a positive electrode for an all-solid-state battery and a manufacturing method therefor, the positive electrode for an all-solid-state battery comprising: a positive electrode current collector; and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a solid electrolyte, and a surface-modified binder.

Description

Anode for all-solid-state batteries and all-solid-state batteries including the same

[0001] The present invention relates to a positive electrode for an all-solid-state battery and an all-solid-state battery including the same.

[0002] Recently, driven by industrial demands, the development of batteries with high energy density and stability is actively underway. For example, lithium-ion batteries are being commercialized not only in the fields of information and communication devices but also in the automotive sector. In the automotive sector, safety is considered particularly important because it is directly related to human life.

[0003] Recently, all-solid-state batteries in which liquid electrolytes are replaced with solid electrolytes have been proposed. By not using flammable organic solvents, all-solid-state batteries can significantly reduce the likelihood of fire or explosion in the event of a short circuit. Therefore, these all-solid-state batteries can ensure superior safety compared to lithium-ion batteries that use liquid electrolytes.

[0004] The problem that the present invention aims to solve is to provide a positive electrode for an all-solid-state battery with improved ion conductivity and lifespan characteristics.

[0005] Another problem to be solved by the present invention is to provide an all-solid-state battery with reduced cell resistance and improved lifespan and capacity characteristics.

[0006] A positive electrode for an all-solid-state battery according to one embodiment of the present invention comprises a positive electrode current collector; and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a solid electrolyte, and a surface-modified binder.

[0007] A method for manufacturing a positive electrode for an all-solid-state battery according to another embodiment of the present invention comprises the steps of: performing a surface treatment process on a binder to produce a surface-modified binder; mixing a positive electrode active material, the surface-modified binder, and a solid electrolyte to produce a positive electrode slurry; and applying the positive electrode slurry to one surface of a positive electrode current collector.

[0008] A solid-state battery according to another embodiment of the present invention comprises a positive electrode for the solid-state battery; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0009] A positive electrode for an all-solid-state battery according to one embodiment of the present invention includes a surface-modified binder, thereby improving the dispersibility among components within the positive electrode active material layer, so that excellent ion conductivity can be secured, and at the same time, lifespan characteristics and cycle stability can be improved.

[0010] In addition, the all-solid-state battery according to another embodiment of the present invention includes the positive electrode, thereby having excellent capacity characteristics, rate characteristics, and lifespan characteristics.

[0011] FIG. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0012] FIG. 2 is a schematic diagram illustrating the modification of the surface of a binder according to one embodiment of the present invention.

[0013] FIG. 3 is a schematic diagram illustrating the bonding between a surface-modified binder, a positive electrode active material, and a solid electrolyte according to one embodiment of the present invention.

[0014] Figure 4 is a schematic diagram illustrating the dispersibility within the positive electrode active material layer.

[0015] Figure 5 is a schematic cross-sectional view showing an enlarged view of area A of Figure 1.

[0016] Figure 6 is a schematic cross-sectional view showing an enlarged view of area B of Figure 5.

[0017] FIG. 7 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention.

[0018] FIG. 8 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention.

[0019] [Explanation of the symbol]

[0020] 1: All-solid-state battery

[0021] 100: Anode 110: Anode current collector

[0022] 120: Positive active material layer 121: Positive active material

[0023] 122: Solid electrolyte 123: Surface-modified binder

[0024] 121a: Sulfur series substances 121b: First metal halide salts

[0025] 121c: Secondary metal halide salts 121d: Carbonaceous substances

[0026] 200: Cathode 210: Cathode current collector

[0027] 220: Coating layer 230: Lithium metal layer

[0028] 300: Solid electrolyte layer

[0029] In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention are described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications can be made. The description of these embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0030] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the components are exaggerated for the effective description of the technical content. Throughout the specification, parts indicated by the same reference numeral represent the same components.

[0031] The embodiments described herein will be explained with reference to cross-sectional and / or plan views, which are exemplary illustrations of the invention. In the drawings, the thicknesses of the films and regions are exaggerated for effective explanation of the technical content. Accordingly, the regions illustrated in the drawings are schematic in nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific forms of regions of the device and are not intended to limit the scope of the invention.

[0032] In the various embodiments of this specification, terms such as first, second, primary, secondary, etc., have been used to describe various components, but these components should not be limited by such terms. These terms are used merely to distinguish one component from another. The embodiments described and illustrated herein also include their complementary embodiments.

[0033] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood as being modified by the term "about" in all cases unless otherwise specified.

[0034] The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, 'comprises' and / or 'comprising' do not exclude the presence or addition of one or more other components to the mentioned components.

[0035] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0036] Unless otherwise defined in this specification, the particle size may be the average particle size. Additionally, the particle size refers to the average particle size (D50), which means the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. The average particle size (D50) may be measured by methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the average particle size (D50) value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Alternatively, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then the average particle size (D50) at 50% of the particle size distribution in the measuring device can be calculated.

[0037] In this specification, “metal” includes both metals and metalloids such as silicon and germanium in an elemental or ionic state, and “alloy” means a mixture of two or more metals.

[0038] In this specification, “anode active material” refers to an anode material capable of undergoing lithiation and delithiation, and “anode active material” refers to an anode material capable of undergoing lithiation and delithiation.

[0039] In this specification, “lithiation” and “to lithiate” refer to the process of adding lithium to an electrode active material, and “delithiation” and “to delithiate” refer to the process of removing lithium from an electrode active material.

[0040] In this specification, “charge” and “to charge” refer to the process of providing electrochemical energy to a battery, and “discharge” and “to discharge” refer to the process of removing electrochemical energy from a battery.

[0041] In this specification, “positive electrode” refers to an electrode where electrochemical reduction and lithiation occur during the discharge process, and “negative electrode” refers to an electrode where electrochemical oxidation and delithiation occur during the discharge process.

[0042] In this specification, “ionic conductivity” refers to the ability of ions to move within a material, meaning the degree to which ions, such as lithium ions, can move smoothly between electrodes, and “electronic conductivity” refers to the ability of electrons to move within a material, meaning the degree to which electrons can move smoothly between electrodes.

[0043] Currently commercialized lithium-ion batteries utilize liquid electrolytes and polymer separators. However, liquid electrolytes pose risks such as fire and explosion due to continuous charging, discharging, or degradation, while polymer separators are prone to damage due to their weak mechanical properties and can cause short circuits by allowing physical contact between the anode and cathode. Consequently, there is growing interest in solid electrolytes that can replace liquid electrolytes and polymer separators while ensuring high energy density and stability.

[0044] Solid electrolytes include sulfide-based solid electrolytes, which possess high ionic conductivity and low interfacial resistance, and oxide-based electrolytes, which exhibit high thermal and chemical stability and excellent durability. However, solid electrolytes often struggle to provide ionic conductivity as sufficient as that of liquid electrolytes, and the increased contact resistance between the electrode and the solid electrolyte can lead to reduced battery efficiency.

[0045] Furthermore, all-solid-state batteries utilizing solid electrolytes can be manufactured using a dry process. Since this dry process does not use solvents, it has a minimal environmental impact. Additionally, because it eliminates the need for a separate solvent treatment process, it simplifies the process and offers cost-saving benefits. In particular, sulfide-based solid electrolytes, which possess high ionic conductivity equivalent to that of liquid electrolytes and facilitate easy contact with electrodes, are more suitable for the dry process due to their vulnerability to moisture.

[0046] However, although dry processes have a lower likelihood of contact with moisture compared to wet processes, it is impossible to completely avoid contact with moisture during the process. When solid electrolytes or cathode active materials come into contact with moisture, hydroxyl groups (-OH) can form on their surfaces. When hydroxyl groups form on the surface due to contact with moisture, they may bond and aggregate, which can further reduce the dispersibility of components within the cathode active material layer. Furthermore, these chemical changes on the surface can lead to increased interfacial resistance or decreased ionic conductivity, as well as reduced lifespan and capacity characteristics. Accordingly, a method of coating the surfaces of each component with a non-flammable material has been proposed; however, this additional process complicates the process and increases processing costs. Therefore, research is continuing to develop methods that can improve dispersibility while enhancing ionic conductivity, lifespan, and capacity characteristics in processes using solid electrolytes, particularly dry processes.

[0047] A positive electrode for an all-solid-state battery according to one embodiment of the present invention includes a surface-modified binder, thereby improving the dispersibility among components within the positive electrode active material layer, so that excellent ion conductivity can be secured, and at the same time, lifespan characteristics and cycle stability can be improved.

[0048] FIG. 1 is a cross-sectional view of an all-solid-state battery according to an embodiment of the present invention. Referring to FIG. 1, an all-solid-state battery (1) according to an embodiment of the present invention may include a positive electrode (100), a negative electrode (200), and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200). More specifically, an all-solid-state battery (1) according to an embodiment of the present invention may have a structure in which a negative electrode (200), a solid electrolyte layer (300), a positive active material layer (120), and a positive current collector (110) are stacked in order. However, not limited thereto, the all-solid-state battery (1) may further include an additional functional layer, such as an adhesion enhancing layer, between the positive electrode (100) and the solid electrolyte layer (300), or between the negative electrode (200) and the solid electrolyte layer (300).

[0049]

[0050] cathode for all-solid-state batteries

[0051] A positive electrode for an all-solid-state battery according to one embodiment of the present invention comprises a positive electrode current collector; and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer may comprise a positive electrode active material, a solid electrolyte, and a surface-modified binder.

[0052] A positive electrode for an all-solid-state battery according to one embodiment of the present invention comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode (100) may comprise a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on one or both surfaces of the positive electrode current collector (110) (see FIG. 1).

[0053] <Blocked Household>

[0054] The positive current collector (110) can provide a reference surface on which a positive active material layer is disposed. For example, the positive current collector (110) may include a plate or foil comprising indium (In), copper (Cu), magnesium (Mg), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. As a specific example, the positive current collector (110) may be an aluminum foil.

[0055] The thickness of the anode current collector (110) may be, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 35 μm, or 8 μm to 30 μm.

[0056] According to another embodiment of the present invention, the anode (100) may further include a carbon layer between the anode current collector (110) and the anode active material layer (120). For example, the carbon layer may include amorphous carbon, crystalline carbon, etc., and may have a thickness of 20 nm to 1 μm, 50 nm to 1 μm, or 1 μm to 4 μm. By including the carbon layer, the bonding strength between the anode current collector (110) and the anode active material layer (120) can be improved.

[0057] <Anode Active Material Layer>

[0058] FIG. 5 is a schematic cross-sectional view showing an enlarged view of area A of FIG. 1. Referring to FIG. 5, a positive active material layer according to one embodiment of the present invention may include a positive active material (121), a solid electrolyte (122), and a surface-modified binder (123).

[0059] The weight ratio of the positive active material (121) and the solid electrolyte (122) in the positive active material layer (120) may be 40:60 to 90:10, 50:50 to 85:15, or 60:40 to 80:20. By satisfying the above ranges for the weight ratio of the positive active material (121) and the solid electrolyte (122), the cycle characteristics of the battery can be maintained at a certain level or higher, while excellent capacity characteristics can be secured.

[0060] positive active material

[0061] A positive active material layer (120) according to one embodiment of the present invention includes a positive active material (121).

[0062] According to one embodiment of the present invention, the positive active material (121) may include a composite of a sulfur-based material (121a), a metal halide salt (121b and 121c), and a carbon-based material (121d). More specifically, the positive active material (121) according to one embodiment of the present invention may be a composite of a sulfur-based material (121a), a metal halide salt (121b and 121c), and a carbon-based material (121d).

[0063] FIG. 6 is a schematic cross-sectional view showing an enlarged view of region B of FIG. 5. FIG. 6 is a schematic cross-sectional view showing an enlarged view of the positive active material (121) within the positive active material layer (120). More specifically, FIG. 6 shows an enlarged view of the region corresponding to region B of FIG. 5 to explain in more detail the composite of a sulfur-based material (121a), a metal halide salt (121b and 121c), and a carbon-based material (121d) within the positive active material (121). As seen in FIG. 6, the positive active material (121) according to one embodiment of the present invention may include a composite of a sulfur-based material (121a), a first metal halide salt (121b), a second metal halide salt (121c), and a carbon-based material (121d).

[0064] The above positive active material may have a particle form. For example, the above positive active material (121) may be a composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d), and the composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d) may have a particle form.

[0065] For example, the particle size of the positive active material or the particle size of the composite may be 50 μm or less, 30 μm or less, or 10 μm or less, and may be 0.1 μm to 50 μm or 1 μm to 10 μm.

[0066] By satisfying the above range for the particle size of the positive electrode active material, more specifically the particle size of the composite, volume change during charging and discharging can be suppressed, thereby effectively preventing degradation and improving lifespan characteristics. If the particle size of the composite falls outside the above range, volume change of the composite during charging and discharging increases, which may accelerate degradation and consequently degrade the cycle characteristics and lifespan characteristics of the battery.

[0067] The above particle size may be the average particle size (D50) measured using laser diffraction, scanning electron microscopy, etc. For example, the particle size of the above composite may be the arithmetic mean of the particle sizes of a plurality of particles measured using software in a scanning electron microscopy image.

[0068] The above positive active material (121) may have excellent ionic conductivity by including a complex of a sulfur-based material, a metal halide salt, and a carbon-based material. For example, the ionic conductivity of the above positive active material is 3 × 10⁻⁶ at 25°C. -6 S / cm or greater, 3.5 × 10 -6 S / cm or more, 4 × 10 -6 S / cm or more, 5 × 10 -6 S / cm or more, 6 × 10-6 S / cm or greater or 6.75 × 10 -6 It may be greater than S / cm, and 1 × 10 -4 S / cm or less, 0.5 × 10 -4 S / cm or less or 1 × 10 -5 It may be less than S / cm. The above ionic conductivity may be measured using electrochemial impedance spectrometry or the DC polarization method.

[0069] The content of the positive active material (121) may be 50% to 90% by weight with respect to the total weight of the positive active material layer. For example, the content of the positive active material in the positive active material layer may be 55% to 90% by weight, 65% to 85% by weight, or 70% to 80% by weight with respect to the total weight of the positive active material layer. By satisfying the above ranges for the content of the positive active material, the capacity characteristics of the battery containing it can be improved.

[0070] According to one embodiment of the present invention, the sulfur-based material (121a) is S8 and Li2S n It may include at least one of (1 ≤ n ≤ 8, where n is an integer). Specifically, the positive active material (121) of the present invention may include elemental sulfur (S), and the elemental sulfur may exist in the form of a sulfur-based material including at least one of S8 and Li2Sn (1 ≤ n ≤ 8, where n is an integer). For example, the content of the elemental sulfur in the positive active material layer (120) may be 10% to 80% by weight, 10% to 65% by weight, or 15% to 60% by weight with respect to the total weight of the positive active material layer (120).

[0071] According to one embodiment of the present invention, the anode for the all-solid-state battery may be a cathode for a lithium-sulfur battery.

[0072] Lithium-sulfur batteries are batteries that use sulfur-based materials as the cathode active material. Sulfur is non-toxic and abundant, offering excellent price competitiveness. Furthermore, compared to lithium-ion batteries that use metallic materials such as nickel and cobalt as cathode materials, lithium-sulfur batteries utilize the lighter sulfur, resulting in a higher gravitational energy density. Consequently, it is easier to achieve characteristics that are both lightweight and high-capacity.

[0073] Unlike lithium-ion batteries, which generate electrical energy through the redox reaction of electrons separated from lithium ions, lithium-sulfur batteries generate energy through the stepwise conversion of sulfur. Specifically, sulfur, which has a structure consisting of eight atoms in a ring form, undergoes a continuous reduction reaction during discharge and is converted into lithium polysulfide, which has a linear structure, and finally converted into lithium sulfide, thereby generating electrical energy.

[0074] While these lithium-sulfur batteries offer the advantage of easily ensuring high capacity and stability, sulfur, the main component of the cathode active material, is an insulator and thus exhibits low ionic and electronic conductivity. Furthermore, there are issues such as volume changes in the cathode during charging and discharging, or the leaching of polysulfides—intermediates of the reduction reaction—which penetrate the separator through the electrolyte and migrate toward the anode. Consequently, research is ongoing to improve the performance and lifespan characteristics of lithium-sulfur batteries.

[0075] More specifically, sulfur is attracting attention as a next-generation cathode material because it has a high theoretical capacity (1,672 mAh / g), is abundant on Earth, and is relatively inexpensive. Since sulfur has relatively low ionic conductivity, the cathode active material may include a solid electrolyte, a binder, a conductive material, etc., so that a smooth ionic conduction path for lithium ions can be formed.

[0076] The above sulfur-based material may undergo a continuous oxidation / reduction reaction of sulfur and / or lithium sulfide. For example, the above sulfur-based material (121a) may be converted to S8->Li2S8->Li2S6->Li2S4->Li2S2->Li2S by a continuous reduction reaction of sulfur. In this process, lithium ions move between the anode and cathode, and at the same time, electrons may move through an external circuit to generate an electric current.

[0077] The content of the sulfur-based material (121a) may be 20% to 80% by weight with respect to the total weight of the composite. For example, the content of the sulfur-based material (121a) may be 30% to 80% by weight, 35% to 75% by weight, 20% to 55% by weight, or 45% to 73% by weight with respect to the total weight of the composite.

[0078] According to one embodiment of the present invention, the metal halide salt may include two different types of metal halide salts. Specifically, the metal halide salt may include a first metal halide salt (121b) containing an alkali metal and a second metal halide salt (121c) containing a boron group metal (see FIG. 6). Since the metal halide salt includes two different types of metal halide salts, a composite, more specifically a solid solution, can be formed, thereby improving ion conductivity while maintaining the overall shape, reducing interfacial resistance, and effectively suppressing the leaching of lithium polysulfide, which can improve the capacity and cycle characteristics of the battery.

[0079] The above solid solution is (1-xy)Li2S nIt may include -xAX-yBX3 or (1-xy)S8-xAX-yBX3. The x and the y are each 0.01 ≤ x ≤ 0.3 and 0.01 ≤ y ≤ 0.3, and the n is an integer 1 ≤ n ≤ 8, the A is an alkali metal, the B is a boron group metal, and the X is a halogen element.

[0080] The first metal halide salt (121b) may be a binary compound composed of an alkali metal and one element selected from Group 17 of the periodic table. Specifically, the first metal halide salt (121b) may be a lithium salt. For example, the first metal halide salt (121b) may include LiF, LiCl, LiBr, LiI, or a combination thereof.

[0081] The first metal halide salt (121b) can improve the ion conductivity of the positive electrode active material by more easily forming a composite, more specifically a solid solution, with the sulfur-based material (121a).

[0082] The content of the first metal halide salt (121b) may be 2.5% to 15% by weight with respect to the total weight of the composite. For example, the content of the first metal halide salt (121b) may be 2.5% to 10% by weight, 3.3% to 6.6% by weight, 5% to 12.5% ​​by weight, or 7% to 10% by weight with respect to the total weight of the composite.

[0083] The weight ratio of the sulfur-based material (121a) and the first metal halide salt (121b) may be 30:1 to 1:1. For example, the weight ratio of the sulfur-based material (121a) and the first metal halide salt (121b) may be 20:1 to 2:1 or 10:1 to 2:1.

[0084] Additionally, the second metal halide salt (121c) may be a binary compound composed of a boron group metal and one element selected from Group 17 of the periodic table. For example, the second metal halide salt (121c) may include AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TiF3, TiCl3, TiBr3, TiI3, or a combination thereof.

[0085] The second metal halide salt (121c) can more easily form a composite, more specifically a solid solution, with the sulfur-based material (121a) and the first metal halide salt (121b), thereby suppressing the leaching of lithium polysulfide and improving the capacity and cycle characteristics of the battery.

[0086] Additionally, the second metal halide salt (121c) can lower interfacial resistance while maintaining the overall shape of the composite. Specifically, the sulfur-based material (121a) is subjected to oxidation / reduction to S8 and Li2S n Even if the shape is deformed between (1 ≤ n ≤ 8, where n is an integer), the shape deformation of the composite and / or the positive active material can be minimized by the second metal halide salt (121c), thereby easily maintaining the overall shape and thus improving cycle characteristics.

[0087] The content of the second metal halide salt (121c) may be 7.5% to 45% by weight with respect to the total weight of the composite. For example, the content of the second metal halide salt (121c) may be 7.5% to 40% by weight, 10% to 37.5% by weight, or 12% to 30% by weight with respect to the total weight of the composite.

[0088] The weight ratio of the sulfur-based material (121a) and the second metal halide salt (121c) may be 10:1 to 1:1. For example, the weight ratio of the sulfur-based material (121a) and the second metal halide salt (121c) may be 5:1 to 1:1 or 5:1 to 2:1.

[0089] Additionally, the weight ratio of the first metal halide salt (121b) and the second metal halide salt (121c) may be 1:1 to 1:20. For example, the weight ratio of the first metal halide salt (121b) and the second metal halide salt (121c) may be 3:1 to 1:15, 1:1 to 1:10, or 1:2 to 1:9. By satisfying the above ranges for the weight ratio of the first and second metal halide salts, the effect of improving ion conductivity and capacitance characteristics can be maximized.

[0090] The content of the metal halide salt may be 10% to 60% by weight with respect to the total weight of the composite. For example, the total content of the first metal halide salt (121a) and the second metal halide salt (121c) may be 10% to 40% by weight, 15% to 30% by weight, 20% to 50% by weight, or 25% to 45% by weight with respect to the total weight of the composite.

[0091] The carbon-based material (121d) may form a composite with the sulfur-based material (121a) and the metal halide salts (121b and 121c). The composite of the sulfur-based material (121a), the metal halide salts (121b and 121c), and the carbon-based material (121d) is distinguished from a simple mixture of the sulfur-based material (121a), the metal halide salts (121b and 121c), and the carbon-based material (121d). A simple mixture of the sulfur-based material (121a), the metal halide salts (121b and 121c), and the carbon-based material (121d) may have high interfacial resistance because it fails to maintain a dense interface between the sulfur-based material (121a), the metal halide salts (121b and 121c), and the carbon-based material (121d), which can degrade the lifespan characteristics of the battery.

[0092] The above carbon-based material (121d) is a material containing carbon atoms and is not particularly limited as long as it is used as a conductive material in the relevant technical field. In addition, the form of the above carbon-based material (121d) may be in the form of particles, sheets, flakes, etc., but is not limited thereto. For example, the carbon-based material (121d) may include crystalline carbon, amorphous carbon, or a combination thereof, and may include a calcined carbon precursor.

[0093] Additionally, the carbon-based material (121d) may be a carbon nanostructure and may include a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. For example, the carbon nanostructure may include carbon nanotubes (CNT), carbon nanofibers (CNF), carbon nanobelts, carbon nanorods, graphene, or a combination thereof.

[0094] Additionally, the carbon-based material (121d) may be a porous carbon-based material or a non-porous carbon-based material and may include periodic and regular two-dimensional or three-dimensional pores. For example, the carbon-based material (121d) may include carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black, graphite, activated carbon, or a combination thereof.

[0095] Additionally, the carbon-based material (121d) may include a fibrous carbon-based material. If the carbon-based material (121d) is a fibrous carbon-based material, electron conduction from the surface to the interior of the composite containing it can be performed more easily, thereby further improving electron conductivity. As a result, the internal resistance of the positive electrode active material containing the composite can be reduced, and the cycle characteristics of the battery containing it can be further improved.

[0096] The aspect ratio of the fibrous carbon-based material may be 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more, and may be 2 to 30, 2 to 20, 2 to 10, 2 to 8, 2 to 5, 2 to 4, 3 to 30, 4 to 30, 5 to 30, 10 to 30, or 20 to 30. By satisfying the above ranges for the aspect ratio of the fibrous carbon-based material, the effect of enhancing the electronic conductivity of the composite containing it can be maximized, while also mitigating the imbalance of local electronic conductivity within the composite.

[0097] The diameter of the fibrous carbon-based material may be 0.01 μm to 10 μm, 0.05 μm to 10 μm, or 0.1 μm to 5 μm, and the length may be 1 μm to 50 μm or 1 μm to 20 μm. The diameter and length of the fibrous carbon-based material may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images, or may be measured by laser diffraction.

[0098] Additionally, the fibrous carbon-based material may include carbon nanostructures. For example, the carbon nanostructures may include carbon nanofibers (CNF), carbon nanotubes (CNT), carbon nanobelts, carbon nanorods, or a combination thereof. The carbon nanostructures may form a primary carbon nanostructure composed of a single carbon nanostructure and a secondary carbon nanostructure formed by the aggregation of multiple carbon nanostructures.

[0099] For example, the primary carbon nanostructure may have a diameter of 1 nm to 200 nm, 1 nm to 150 nm, 1 nm to 100 nm, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 20 nm, and a length of 10 nm to 2 μm, 10 nm to 1.5 μm, 10 nm to 1 μm, 10 nm to 500 nm, 10 nm to 400 nm, 10 nm to 300 nm, 10 nm to 200 nm, or 10 nm to 100 nm.

[0100] Additionally, the secondary carbon nanostructure may be a structure formed by assembling primary carbon nanostructures to form a bundle or rope type, either wholly or partially. For example, the secondary carbon nanostructure may include a bundle-type carbon nanostructure, a rope-type carbon nanostructure, or a combination thereof.

[0101] For example, the secondary carbon nanostructure may have a diameter of 2 nm to 200 nm, 3 nm to 150 nm, 5 nm to 100 nm, 5 nm to 50 nm, 5 nm to 30 nm, or 5 nm to 20 nm, and a length of 20 nm to 2 μm, 30 nm to 1.5 μm, 50 nm to 1 μm, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 200 nm, or 50 nm to 100 nm.

[0102] The diameter and length of the above primary and secondary carbon nanostructures may be measured from scanning electron microscope (SEM) or transmission electron microscope (TEM) images, or may be measured by laser diffraction.

[0103] The content of the carbon-based material (121d) may be 1% to 30% by weight with respect to the total weight of the composite. For example, the content of the carbon-based material (121d) may be 1% to 20% by weight, 5% to 20% by weight, or 10% to 20% by weight with respect to the total weight of the composite. By satisfying the above range for the content of the carbon-based material (121d), the cycle characteristics of the battery containing it can be further improved. Specifically, if the content of the carbon-based material (121d) is less than the above range, the electronic conductivity of the composite containing it may be too low, and the internal resistance of the positive active material may increase, and if the content of the carbon-based material (121d) exceeds the above range, the energy density of the battery containing it may decrease.

[0104] Additionally, the composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d) may have ductility. Specifically, the composite may function as a buffer material within the positive active material layer (120), thereby preventing defects caused by volume changes in the positive active material layer (120).

[0105] The Mohs hardness of the composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d) may be less than 2. For example, the Mohs hardness of the composite may be smaller than the Mohs hardness of the lithium salt, and may be 1.5 or less or 0.7 or less.

[0106] The content of the composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d) may be 40% to 90% by weight with respect to the total weight of the positive active material layer (120). For example, the content of the composite of the sulfur-based material (121a), metal halide salts (121b and 121c) and carbon-based material (121d) within the positive active material layer (120) may be 50% to 85% by weight, 60% to 80% by weight, or 65% to 75% by weight with respect to the total weight of the positive active material layer (120). By satisfying the above ranges for the content of the composite of the sulfur-based material, metal halide salts, and carbon-based material, the capacity characteristics of the battery containing the same can be improved.

[0107] solid electrolyte

[0108] A positive active material layer (120) according to one embodiment of the present invention includes a solid electrolyte (122).

[0109] Specifically, the solid electrolyte (122) can provide an ion transfer path within the positive active material layer (120). Since the positive active material layer (120) according to one embodiment of the present invention may have a further reduced internal resistance by including the positive active material (121) and the solid electrolyte (122), the cycle characteristics of the battery including it can be further improved.

[0110] As a specific example, the solid electrolyte may be a sulfide-based solid electrolyte, and the sulfide-based solid electrolyte (122) may have a particle form and may be dispersed among the positive active materials (121) (see FIG. 5).

[0111] The solid electrolyte (122) may include a complex of Li2S and a solid electrolyte, for example, an inorganic solid electrolyte. Additionally, the solid electrolyte (122) may include Li, S and / or P, and may optionally include a halogen element.

[0112] For example, the solid electrolyte (122) is Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m and n are positive, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive, respectively, M is one of P, Si, Ge, B, Al, Ga, or In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-xBr x (0≤x≤2), and Li 7-x PS 6-x I x It may include one or more selected from (0≤x≤2).

[0113] The above solid electrolyte (122) is Li 7-a-c M a PS 6-c X c It may include argyrodite-type compounds represented by (0≤a≤2, 0≤c≤2).

[0114] The above X may be F, Br, Cl, I, or a combination thereof, and the above M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), It may be antimony (Sb), bismuth (Bi), or a combination thereof.

[0115] The density of the above azirodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. By satisfying the above range for the density of the azirodite-type solid electrolyte, the internal resistance of the battery containing it can be reduced, and defects such as penetration or short-circuiting of the solid electrolyte film due to lithium dendrite formation can be prevented. In addition, the elastic modulus of the above azirodite-type solid electrolyte may be 15 GPa to 35 GPa or 15 GPa to 30 GPa.

[0116] In addition, the solid electrolyte (122) is 1 × 10 at room temperature -5 It can have an ionic conductivity of S / cm or greater. For example, the ionic conductivity of the solid electrolyte (122) is 1.5 × 10⁻⁶ at room temperature. -5 S / cm or more, 2 × 10 -5 S / cm or more, 4 × 10 -5 S / cm or more, 6 × 10 -5 S / cm or more, 8 × 10 -5 S / cm or more or 1 × 10 -4 It may be greater than S / cm.

[0117] According to another embodiment of the present invention, the positive active material layer (120) may further include a solid electrolyte in addition to the solid electrolyte (122). Specifically, the positive active material layer (120) may include a sulfide-based solid electrolyte and / or an oxide-based solid electrolyte different from the above-described sulfide-based solid electrolyte in addition to the above-described sulfide-based solid electrolyte.

[0118] For example, the positive active material layer (120) is Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In), Li 7-x PS 6-x Cl x , 0 ≤ x ≤ 2, Li 7-x PS 6-x Br x, 0 ≤ x ≤ 2, and Li 7-x PS 6-x I x It may include one or more solid electrolytes selected from , 0 ≤ x ≤ 2, and Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 < x <2, 0 ≤ y <3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M=Te, Nb, or Zr, 0≤x≤10), Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12(M-doped LLZO, M=Ga, W, Nb, Ta, or Al, 0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체 전해질을 더 포함할 수 있으나, 이에 한정되는 것은 아니다.

[0119] In addition, the solid electrolyte in the positive active material layer (120) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300).

[0120] The solid electrolyte in the positive active material layer (120) may have an average particle size (D50) smaller than that of the solid electrolyte in the solid electrolyte layer (300). For example, the average particle size (D50) of the solid electrolyte in the positive active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less compared to the average particle size (D50) of the solid electrolyte in the solid electrolyte layer (300).

[0121] The content of the solid electrolyte may be 10% to 30% by weight with respect to the total weight of the positive electrode active material layer. For example, the content of the solid electrolyte in the positive electrode active material layer may be 15% to 30% by weight or 20% to 30% by weight with respect to the total weight of the positive electrode active material layer. By satisfying the above range for the content of the solid electrolyte, the capacity characteristics of the battery containing it can be further improved.

[0122] Surface-modified binder

[0123] A positive active material layer according to one embodiment of the present invention includes a surface-modified binder (123). Specifically, the surface-modified binder (123) may include a functional group capable of forming a bond with a hydroxyl group on its surface.

[0124] FIG. 2 is a schematic diagram illustrating the surface modification of a binder according to an embodiment of the present invention. For example, a binder (BID) surface-modified through a surface-modification process may have functional groups (FNG) formed on its surface. That is, a binder surface-modified through a surface-modification process may include functional groups capable of forming bonds with hydroxyl groups on its surface. The surface-modification process is not particularly limited to any process capable of forming functional groups capable of forming bonds with hydroxyl groups, such as plasma treatment, oxidation treatment, etching treatment, UV treatment, or laser treatment.

[0125] FIG. 3 is a schematic diagram illustrating the bonding between a surface-modified binder, a positive electrode active material, and a solid electrolyte according to an embodiment of the present invention. When the positive electrode active material (CAC) and the solid electrolyte (SEP) come into contact with moisture, hydroxyl groups (-OH) may be formed on their surfaces. A first hydroxyl group (HDG1) may be formed on the surface of the positive electrode active material (CAC), and a second hydroxyl group (HDG2) may be formed on the surface of the solid electrolyte (SEP). The first hydroxyl group (HDG1) and the second hydroxyl group (HDG2) may bond with each other, causing the positive electrode active material (CAC) and the solid electrolyte (SEP) to aggregate.

[0126] FIG. 4 is a schematic diagram illustrating the dispersibility within the positive active material layer. Specifically, FIG. 4 is a schematic cross-sectional view showing an enlarged view of area A of FIG. 1, illustrating a case where the positive active material layer (120) of an all-solid-state battery according to one embodiment of the present invention does not contain a surface-modified binder (BID). Referring to FIG. 4, when the positive active material (CAC) and the solid electrolyte (SEP) within the positive active material layer come into contact with moisture, hydroxyl groups are formed on their respective surfaces and can bond with each other and aggregate. As a result, the dispersibility and uniformity of distribution of the positive active material (CAC) and the solid electrolyte (SEP) within the positive active material layer are reduced, which may cause voids (POR) within the positive active material layer. Consequently, lithium ion conductivity may be reduced, and the availability rate of the components may be lowered, which may also reduce the lifespan and cycle stability of the battery.

[0127] FIG. 5 is a schematic cross-sectional view illustrating an enlarged view of area A of FIG. 1. Specifically, FIG. 5 is a schematic cross-sectional view showing a positive active material layer (120) of an all-solid-state battery according to an embodiment of the present invention. Referring to FIG. 5, even if hydroxyl groups are formed on the surface of the positive active material (121) and the solid electrolyte (122) due to contact with moisture, the positive active material (CAC) and the solid electrolyte (SEP) can be evenly dispersed within the positive active material layer due to the surface-modified binder (BID). More specifically, the functional groups formed on the surface of the surface-modified binder (BID) according to an embodiment of the present invention can be combined with the hydroxyl groups on the surfaces of the positive active material (CAC) and the solid electrolyte (SEP), respectively, thereby preventing the positive active material (CSC) and the solid electrolyte (SEP) from aggregating with each other. Therefore, since dispersibility and uniformity of distribution can be improved, excellent ion conductivity can be secured, and at the same time, lifespan characteristics and cycle stability can be improved.

[0128] The surface-modified binder may include polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylate, polyethylene oxide, polypropylene oxide, polyacrylonitrile, or a combination thereof. Polytetrafluoroethylene may be preferred in terms of compatibility with the positive electrode active material (121) and the solid electrolyte (122) and dry process, but is not limited thereto. As a specific example, the surface-modified binder may be polytetrafluoroethylene (PTFE) having amino groups (-NH2) formed on its surface.

[0129] The surface-modified binder may include a functional group capable of forming a bond with a hydroxyl group on the surface, and the functional group may include an amino group, an amide group, a trifluoromethyl group, or a combination thereof.

[0130] The surface-modified binder may be one in which some functional groups of the binder are substituted with amino groups, amide groups, trifluoromethyl groups, or combinations thereof through the surface treatment. In this case, the substitution rate may be 5% to 30% or 5% to 25%.

[0131] The content of the functional group formed on the surface of the surface-modified binder is 1.0 × 10 -8 mol / cm 3 Up to 3.0 × 10 -6 mol / cm 3 It may be. For example, the content of the functional group formed on the surface of the surface-modified binder is 1.2 × 10 -8 mol / cm 3 Up to 1.5 × 10 -6 mol / cm 3 or 1.5 × 10⁻⁶ -8 mol / cm 3 Up to 1.5 × 10 -7 mol / cm 3 It could be.

[0132] By satisfying the content and substitution rate of the functional groups of the surface-modified binder, respectively, desirable dispersibility can be secured without degrading performance such as volume relaxation effects due to the binder.

[0133] The surface-modified binder may have a surface roughness of 8 nm to 20 nm. For example, the surface roughness of the surface-modified binder may be 10 nm to 20 nm, 8 nm to 15 nm, or 10 nm to 15 nm.

[0134] The above-mentioned surface-modified binder has a surface energy of 30 mJ / m² 2 Up to 60 mJ / m 2 It may be. For example, the surface energy of the surface-modified binder is 35 mJ / m² 2 Up to 60 mJ / m 2 , 45 mJ / m 2 Up to 60 mJ / m 2 or 35 mJ / m² 2 Up to 55 mJ / m 2 It could be.

[0135] The content of the surface-modified binder may be 0.5% to 5% by weight with respect to the total weight of the positive electrode active material layer. For example, the content of the surface-modified binder may be 0.5% to 3.5% by weight, 0.6% to 2.5% by weight, or 0.8% to 2.2% by weight with respect to the total weight of the positive electrode active material layer. By satisfying the above range for the content of the surface-modified binder, dispersibility can be improved, and at the same time, excellent capacity characteristics can be secured while maintaining the cycle characteristics of the battery at a certain level or higher.

[0136] In addition, the weight ratio of the surface-modified binder and the solid electrolyte may be 1:5 to 1:40. For example, the weight ratio of the surface-modified binder and the solid electrolyte may be 1:8 to 1:40, 1:10 to 1:35, or 1:15 to 1:30.

[0137] By satisfying the above range for the weight ratio of the solid electrolyte and the surface-modified binder, ion conductivity and interfacial stability can be further improved, and excellent capacity characteristics can be secured while maintaining the cycle characteristics of the battery above a certain level. More specifically, since dispersibility can be improved even by adding only a small amount of the surface-modified binder having such characteristics, sufficient capacity characteristics can be secured even when using less solid electrolyte.

[0138] According to another embodiment of the present invention, the positive active material layer may further include a binder, a conductive material, etc. Specifically, the positive active material layer may further include a binder, a conductive material, etc. other than the surface-modified binder.

[0139] The conductive material described above is conductive without causing chemical changes and can improve the electrical conductivity of the anode active material and the solid electrolyte. The conductive material may include a carbon-based material. For example, the conductive material may include one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0140] The content of the conductive material may be 0.5% to 5% by weight, 0.5% to 4% by weight, 0.5% to 3.5% by weight, or 0.5% to 2% by weight with respect to the total weight of the positive active material layer (120).

[0141] The binder may include a material capable of improving the bonding strength between the positive active material, solid electrolyte, conductive material, etc., within the positive active material layer. For example, the binder may include polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0142] The content of the binder may be 0.5% to 10% by weight, 0.5% to 5% by weight, or 0.5% to 2% by weight with respect to the total weight of the positive active material layer (120).

[0143] According to another embodiment of the present invention, the positive active material layer may further include additives such as a coating agent, a dispersant, and an ion conductivity aid. Known materials generally used in electrodes of all-solid-state batteries may be used as the coating agent, dispersant, ion conductivity aid, etc., and are not particularly limited.

[0144]

[0145] Method for manufacturing a positive electrode for an all-solid-state battery

[0146] A method for manufacturing a positive electrode for an all-solid-state battery according to another embodiment of the present invention may include the step of manufacturing a surface-modified binder by performing a surface treatment process on a binder; the step of manufacturing a positive electrode slurry by mixing a positive electrode active material, the surface-modified binder, and a solid electrolyte; and the step of applying the positive electrode slurry to one surface of a positive electrode current collector.

[0147] First, a surface-modified binder can be manufactured by performing a surface treatment process on the binder. The description of the binder is as previously stated.

[0148] The binder may include polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylate, polyethylene oxide, polypropylene oxide, polyacrylonitrile, or a combination thereof.

[0149] The above surface treatment process is not particularly limited as long as it is a process capable of forming functional groups capable of forming bonds with hydroxyl groups on the surface of the binder, and can be performed, for example, by plasma treatment, oxidation treatment, etching treatment, UV treatment, laser treatment, or a combination thereof. Specifically, functional groups capable of forming bonds with hydroxyl groups can be formed on the surface of the binder through the above surface treatment process. The description of the functional groups is as previously described.

[0150] For example, plasma treatment involves applying various types of energy and particles to a surface to increase roughness through physical impact, sever polymer chains, or form new chemical bonds. There are two methods for plasma treatment: the low-pressure plasma method, which generates plasma by discharging at low pressure, and the atmospheric pressure plasma method, which generates plasma by discharging at atmospheric pressure; however, the atmospheric pressure plasma method is primarily used due to its advantages in productivity and economic efficiency. By generating plasma at atmospheric pressure by controlling voltage, frequency, and current conditions, oxygen, nitrogen, and other elements are excited by the discharge, thereby enabling the formation of functional groups such as -NH and -C=O on the surface of the support.

[0151] Subsequently, an anode slurry is prepared by mixing the anode active material, the surface-modified binder, and the solid electrolyte. The description of the anode active material and the solid electrolyte is as described above.

[0152] The step of preparing the anode slurry can be performed as a first-step mixing process in which the anode active material, the surface-modified binder, and the solid electrolyte are all mixed. Additionally, the step of preparing the anode slurry can be performed as a total of two-step mixing process in which the anode active material and the solid electrolyte are mixed, and then the surface-modified binder is added and mixed. Furthermore, the step of preparing the anode slurry can be performed as a three-step mixing process in which the anode active material and the surface-modified binder are mixed to prepare a first mixture, the solid electrolyte and the surface-modified binder are mixed to prepare a second mixture, and then the first and second mixtures are mixed.

[0153] For example, a positive electrode active material, the surface-modified binder prepared above, and a solid electrolyte are all mixed to prepare a positive electrode slurry, and then the positive electrode slurry is applied to at least one surface of a positive electrode current collector, dried, and then pressed to form a positive electrode active material layer (mixing in step 1).

[0154] When an anode slurry is prepared through a total of three mixing steps by mixing a primary mixture of an anode active material and a surface-modified binder, and a secondary mixture of a solid electrolyte and a surface-modified binder, dispersibility and uniformity of distribution can be maximized. More specifically, the above three mixing steps can further improve the bonding between the anode active material and the surface-modified binder, and the bonding between the solid electrolyte and the surface-modified binder, compared to the first mixing step or the second mixing step, thereby maximizing dispersibility and uniformity of distribution.

[0155] The above drying can be performed at 85°C to 130°C or 90°C to 115°C, and the description of the anode current collector is as described above.

[0156]

[0157] *139 The above-mentioned positive active material may be manufactured through a dry method, a wet method, or a combination thereof, but is not limited thereto. For example, the method of manufacturing the above-mentioned positive active material may be performed by milling, heat treatment, deposition, etc.

[0158] Specifically, the step of manufacturing the positive electrode active material may include a step of first milling a mixture of a sulfur-based material and a metal halide salt; and a step of secondarily milling a mixture of the first milling product and a carbon-based material.

[0159] The description of the sulfur-based material, the metal halide salt, and the carbon-based material is as described above. The metal halide salt includes a first metal halide salt containing an alkali metal and a second metal halide salt containing a boron group metal.

[0160] The above first and second milling may refer to a grinding process as mechanical milling. For example, the above first and second milling may each be performed by a ball mill or a bead mill. Additionally, the above first and second milling may each be performed at 25°C and may be performed for 1 hour to 15 hours, 2 hours to 12 hours, or 5 hours to 10 hours at 100 rpm to 1,500 rpm, 150 rpm to 1,000 rpm, or 250 rpm to 800 rpm. At this time, the energy of the first and second milling may be 10 G to 60 G, 10 G to 45 G, or 15 G to 40 G.

[0161] Subsequently, the primary milling product, that is, the composite of the sulfur-based material-first metal halide salt-second metal halide salt obtained by the primary milling, can be mixed with the carbon-based material in a weight ratio of 3:1 to 15:1. For example, the mixing weight ratio of the primary milling product and the carbon-based material may be 3:1 to 12:1, 5:1 to 10:1, or 5:1 to 8:1.

[0162]

[0163] All-solid-state battery

[0164] A solid-state battery according to another embodiment of the present invention comprises a positive electrode for the solid-state battery; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0165] anode

[0166] The description of the anode for the all-solid-state battery above is as previously stated.

[0167] FIG. 7 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 7, an all-solid-state battery (1) according to one embodiment of the present invention may include a positive electrode (100), a negative electrode (200), and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200). More specifically, an all-solid-state battery (1) according to one embodiment of the present invention may have a structure in which a negative electrode current collector (210), a coating layer (220), a solid electrolyte layer (300), a positive electrode active material layer (120), and a positive electrode current collector (110) are stacked in order.

[0168] cathode

[0169] The above cathode (200) may include a cathode current collector (210) and a coating layer (220). The cathode current collector (210) may provide a reference surface on which the coating layer is placed.

[0170] The above-mentioned negative electrode current collector (210) may include a material that does not react with lithium, that is, does not form an alloy or compound with lithium. For example, the above-mentioned negative electrode current collector may include at least one metal selected from the group consisting of copper (Cu), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The above-mentioned negative electrode current collector may be composed of one of the metals described above, or may include an alloy or coating material of two or more metals.

[0171] Additionally, the negative current collector (210) may be in the form of a plate or a foil, and the thickness of the negative current collector may be 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0172] According to another embodiment of the present invention, the all-solid-state battery (1) may not include a negative electrode current collector (210). That is, the negative electrode current collector (210) may be omitted.

[0173] The coating layer (220) can be configured to allow lithium metal to grow between the solid electrolyte layer (300) and the negative current collector (210). The coating layer (220) can serve as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0174] The coating layer (220) may be a single-layer structure or a multi-layer structure including multiple layers. For example, the coating layer (220) may be a single layer or a structure of two, three, or four layers.

[0175] The coating layer (220) may include a metal-carbon composite. More specifically, the coating layer (220) may include a composite of metal particles and a carbon-based material.

[0176] The metal-carbon composite may have a particle form, and the average particle size of the metal-carbon composite may be 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less, or 10 nm to 4 μm, 10 nm to 3 μm, 10 nm to 2 μm, 10 nm to 1 μm, or 10 nm to 900 nm. By satisfying the above ranges for the average particle size of the metal-carbon composite, reversible absorption and / or desorption of lithium during charging and discharging may be more facilitated.

[0177] The average particle size of the above metal-carbon composite is the median diameter (D50) measured using a laser particle size distribution meter.

[0178] The metal particles in the metal-carbon composite may comprise at least one metal or metalloid selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Additionally, the carbon-based material in the metal-carbon composite may comprise at least one selected from the group consisting of carbon black, acetylene black, furnace black, Kettjen black, and graphene. As a specific example, the carbon-based material in the metal-carbon composite may be amorphous carbon. The amorphous carbon may be carbon that does not have crystallinity or has very low crystallinity.

[0179] The weight ratio of the metal particles and the carbon-based material in the coating layer (220) may be 10:1 to 1:2. For example, the mixing ratio of the metal particles and the carbon-based material may be 5:1 to 1:1 or 4:1 to 2:1.

[0180] In addition, the content of the metal particles may be 8% to 60% by weight, 10% to 50% by weight, 15% to 40% by weight, or 20% to 30% by weight with respect to the total weight of the metal-carbon composite. By satisfying the above ranges for the content of the metal particles, the cycle characteristics of the battery can be further improved.

[0181] According to another embodiment of the present invention, the coating layer (220) may further include other additives in addition to the metal-carbon composite. For example, the coating layer (220) may further include at least one additive selected from the group consisting of binders, fillers, coating agents, dispersants, and ion-conducting aids.

[0182] Additionally, the thickness of the coating layer (220) may be smaller than the thickness of the positive active material layer. For example, the thickness of the coating layer (220) may be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive active material layer, and may be 1 μm to 20 μm, 2 μm to 10 μm, or 3 μm to 7 μm. By satisfying the above range, the cycle characteristics of the battery can be further improved. If the thickness of the coating layer (220) exceeds the above range, the energy density of the battery containing it may decrease, and the internal resistance may increase, thereby degrading the cycle characteristics.

[0183] FIG. 8 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 8, an all-solid-state battery (1) according to one embodiment of the present invention may include a positive electrode (100), a negative electrode (200), and a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200). More specifically, an all-solid-state battery (1) according to one embodiment of the present invention may have a structure in which a negative electrode current collector (210), a lithium metal layer (230), a coating layer (220), a solid electrolyte layer (300), a positive electrode active material layer (120), and a positive electrode current collector (110) are stacked in order.

[0184] The lithium metal layer (230) may include lithium or a lithium alloy. The lithium metal layer is a metal layer containing lithium and can function as a lithium reservoir. For example, the lithium alloy may be a Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited thereto. The lithium alloy may be composed of one of the metals described above or may include an alloy of two or more metals.

[0185] Additionally, the lithium metal layer (230) may be a plated layer formed by precipitation between the coating layer (220) and the negative current collector (210) during the charging process.

[0186] For example, the thickness of the lithium metal layer (230) may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. By satisfying the above range, the cycle characteristics of the battery containing the lithium metal layer (230) can be improved without degrading the performance of the battery. If the thickness of the lithium metal layer (230) is less than the above range, it cannot sufficiently perform the role of a lithium reservoir, and if it exceeds the above range, the mass and volume of the battery may increase, which may degrade performance and also degrade cycle characteristics.

[0187] According to another embodiment of the present invention, the lithium metal layer (230) may be provided between the negative electrode current collector (210) and the coating layer (220) before assembly of the battery. As a specific example, the lithium metal layer (230) may be placed as a lithium foil between the negative electrode current collector (210) and the coating layer (220) before assembly of the battery.

[0188] According to another embodiment of the present invention, the lithium metal layer (230) may be formed by precipitation through charging after the assembly of the battery. In this case, since the lithium metal layer (230) is not included during the assembly of the battery, the energy density of the battery may be increased, and charging may be performed beyond the charging capacity of the coating layer (220). That is, the coating layer (220) may be overcharged. Specifically, lithium may be absorbed in the coating layer (220) at the beginning of charging, but when charged beyond the capacity of the coating layer (220), lithium may be precipitated between the coating layer (220) and the negative electrode current collector (210) to form the lithium metal layer (230).

[0189] Since the lithium metal layer (230) can be composed mainly of lithium, the lithium in the lithium metal layer (230) can be ionized and move to the positive electrode during discharge. That is, the lithium in the lithium metal layer can be used as a negative electrode active material.

[0190] In addition, since the coating layer (220) can be disposed on the lithium metal layer (230), the coating layer (220) can cover and protect the lithium metal layer (230) and suppress the precipitation growth of lithium dendrites. Therefore, short circuits and capacity degradation of the battery can be suppressed, and the cycle characteristics of the battery can be improved.

[0191] When a lithium metal layer (230) is formed by charging after assembly of the battery, the negative electrode current collector (210), the coating layer (220), and the region between them may be a Li-free region that does not contain lithium (Li) in the initial state or after complete discharge of the battery.

[0192] According to another embodiment of the present invention, the cathode (200) may further include a thin film between the cathode current collector (210) and the coating layer (220). The thin film may be disposed on one surface of the cathode current collector (210) and may form an alloy with lithium.

[0193] The thin film may include elements capable of forming an alloy with lithium. For example, the thin film may include gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., capable of forming an alloy with lithium, but is not limited thereto; any element capable of forming an alloy with lithium in the relevant technical field is possible. The thin film may be composed of one of these metals, or may be composed of an alloy of various types of metals.

[0194] By including the above thin film, the deposition pattern of the lithium metal layer deposited between the thin film and the coating layer (220) can be further flattened, and the cycle characteristics of the battery can be further improved.

[0195] For example, the thickness of the thin film may be 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film is less than the above range, it may be difficult to perform the function of the thin film, and if it exceeds the above range, the thin film may absorb lithium, which may reduce the amount of lithium precipitated at the negative electrode, thereby degrading the energy density and cycle characteristics of the battery.

[0196] The above thin film may be formed by vacuum deposition, sputtering, plating, etc., but is not limited thereto.

[0197] According to another embodiment of the present invention, the cathode (200) may further include a carbon layer between the cathode current collector (210) and the solid electrolyte layer (300). The description of the carbon layer is as described above.

[0198] According to another embodiment of the present invention, the cathode (200) may include a cathode active material layer corresponding to the coating layer (220).

[0199] The negative electrode active material in the above negative electrode active material layer may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0200] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0201] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0202] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x ≤ 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0203] The silicon-carbon composite may be a composite of silicon and amorphous carbon. As a specific example, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include a secondary particle (core) assembled from silicon primary particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particle. The amorphous carbon may also be located between the silicon primary particles, for example, the silicon primary particles may be coated with the amorphous carbon. Additionally, the secondary particles may be dispersed within an amorphous carbon matrix.

[0204] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0205] The above Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0206] In addition, the content of the cathode active material in the cathode active material layer may be 90% to 99% by weight with respect to the total weight of the cathode active material layer. For example, the content of the cathode active material may be 93% to 99% by weight or 96% to 98.5% by weight with respect to the total weight of the cathode active material layer.

[0207] As a specific example, the above-mentioned negative electrode active material may include at least one of graphite and Si composites.

[0208] When the above-mentioned cathode active material includes a Si composite and graphite together, the Si composite and graphite may be included in the form of a mixture, in which case the weight ratio of the Si composite and graphite may be 1:99 to 50:50. For example, the weight ratio of the Si composite and graphite may be 3:97 to 20:80 or 5:95 to 20:80.

[0209] The above Si composite may include a core containing Si-based particles and an amorphous carbon coating layer, for example, the Si-based particles may be a Si-C composite, SiO x It may include one or more of (0 < x ≤ 2) and Si alloys. For example, the Si-C composite may include a core containing Si particles and crystalline carbon and an amorphous carbon coating layer located on the surface of the core.

[0210] The above crystalline carbon may include, for example, graphite, and more specifically, may include natural graphite, artificial graphite, or a mixture thereof.

[0211] The above-mentioned cathode (200) may include a binder. The cathode binder can effectively bond the cathode active material particles together and can serve to effectively bond the cathode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0212] The above-mentioned non-aqueous binder may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, or a combination thereof.

[0213] The above-mentioned water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0214] When a water-based binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As the cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. The alkali metal salt may include Na, K, or Li.

[0215] The above dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0216] In addition, the content of the binder may be 0.5% to 5% by weight with respect to the total weight of the cathode. For example, the content of the cathode binder may be 0.5% to 3.5% by weight or 0.5% to 2% by weight based on the total weight of the cathode.

[0217] The above-mentioned cathode (200) may include a conductive material. The description of the conductive material is as previously described.

[0218] solid electrolyte layer

[0219] A solid-state battery according to another embodiment of the present invention may include a solid electrolyte layer (300).

[0220] A solid electrolyte layer (300) may be disposed between the positive electrode (100) and the negative electrode (200). The solid electrolyte layer (300) may include an upper surface adjacent to the positive electrode (100) and a lower surface adjacent to the negative electrode (200). The positive active material layer (120) of the positive electrode (100) may be adjacent to the upper surface of the solid electrolyte layer (300). The coating layer (220) of the negative electrode (200) may be adjacent to the lower surface of the solid electrolyte layer (300). The solid electrolyte layer (300) may be a medium for transferring lithium ions between the positive electrode (100) and the negative electrode (200).

[0221] During the charging process of the all-solid-state battery, lithium ions can move from the positive electrode (100) through the solid electrolyte layer (300) toward the negative electrode (200). The lithium ions that have moved toward the negative electrode (200) can be plated as lithium metal between the negative electrode current collector (210) and the coating layer (220). The lithium ions that have moved toward the negative electrode (200) can be intercalated or plated within the coating layer (220).

[0222] During the discharge process of the all-solid-state battery, lithium ions can move from the negative electrode (200) through the solid electrolyte layer (300) toward the positive electrode (100). During the discharge process of the all-solid-state battery, lithium metal precipitated between the negative electrode current collector (210) and the coating layer (220) is dissolved, allowing lithium ions to move through the solid electrolyte layer (300) toward the positive electrode (100). During the discharge process of the all-solid-state battery, lithium adsorbed or plated inside the coating layer (220) is deintercalated or dissolved, allowing lithium ions to move through the solid electrolyte layer (300) toward the positive electrode (100).

[0223] The solid electrolyte layer (300) may include a solid electrolyte. For example, the solid electrolyte may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymeric solid electrolyte, or a combination thereof. As a specific example, the solid electrolyte included in the solid electrolyte layer (300) may be the same as or different from the solid electrolyte included in the positive electrode active material layer (110).

[0224] Sulfide-based solid electrolytes are, for example, Li3PO4-Li2SO4, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (In the above formula, m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (In the above formula, p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), Li + 12-n-x A n+ X 2- 6-x Y - x (In the above formula, A is one of P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is one of S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1≤n≤5, 0≤x≤2) Li 7-m M m PS 6-n X n(In the above formula, M is one of Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, Sc, Y, Ti, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Mn, Tc, Re, Bh, Ru, Os, Hs, Co, Rh, Ir, Mt, Ni, Pd, Pt, Ds, Au, Rg, Cd, Hg, or Cn, X is one of F, Cl, Br, or I, 0 <n≤2, 0<x≤2), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x It may include (0≤x≤2) or a combination thereof.

[0225] Sulfide-based solid electrolytes can be manufactured by processing starting materials, such as Li2S or P2S5, using methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. Sulfide-based solid electrolytes may be amorphous, crystalline, or a mixture thereof. Sulfide-based solid electrolytes may, for example, contain at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. Sulfide-based solid electrolytes may, for example, contain Li2S-P2S5. When using a material containing Li2S-P2S5 as a sulfide-based solid electrolyte, the mixed molar ratio of Li2S and P2S5 is, for example, in the range of Li2S : P2S5 = 20 : 80 to 90 : 10, 25 : 75 to 90 : 10, 30 : 70 to 70 : 30, and 40 : 60 to 60 : 40.

[0226] Sulfide-based solid electrolytes can be, for example, argyrodite-type solid electrolytes, and Li 7-a-c M a PS6-c X c It can be expressed as (0≤a≤2, 0≤c≤2).

[0227] The above X may be F, Br, Cl, I, or a combination thereof, and the above M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), It may be antimony (Sb), bismuth (Bi), or a combination thereof.

[0228] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state battery is reduced, and penetration of the solid electrolyte separator by lithium can be suppressed more effectively.

[0229] Oxide-based solid electrolytes are, for example, Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3)O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. Oxide-based solid electrolytes can be produced, for example, by sintering.

[0230] Oxide-based solid electrolytes are, for example, Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M-doped LLZO, M=Ga, W, Nb, Ta, or Al(0 <a<2, 0≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체 전해질이다.

[0231] The polymer solid electrolyte may, for example, comprise a mixture of a lithium salt and a polymer, or comprise a polymer having ion-conducting functional groups. The polymer solid electrolyte may, for example, be a polymer electrolyte that is in a solid state at 25°C and 1 atm. The polymer solid electrolyte may, for example, not contain a liquid.

[0232] For example, polymeric solid electrolytes include polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), poly(styrene-b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene oxide-styrene) block copolymer, polystyrene sulfonate (PSS), polyvinyl fluoride (PVF), poly(methylmethacrylate) (PMMA), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethylene (PTFE), polyethylenedioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, Polyacetylene, Nafion, Aquivion, Flemion, Gore, Aciplex, Morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(arylether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)] (SPBIBI), polystyrene sulfonate (PSS), lithium 9,10-Diphenylanthracene-2-sulfonate (lithium 9,10-diphenylanthracene-2-sulfonate, DPASLi +) or a combination thereof may be included as a polymer, and said polymer is not limited to these, and any polymer used in polymer electrolytes in the relevant technical field is possible.

[0233] The polymer included in the polymer solid electrolyte may be, for example, a compound containing 10 or more, 20 or more, 50 or more, or 100 or more repeating units. The weight-average molecular weight of the polymer included in the polymer solid electrolyte may be, for example, 1,000 Dalton or more, 10,000 Dalton or more, 100,000 Dalton or more, or 1,000,000 Dalton or more.

[0234] The solid electrolyte layer (300) may include, for example, a binder. The binder included in the solid electrolyte layer (300) may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any binder used in the relevant technical field is possible. The binder of the solid electrolyte layer (300) may be the same as or different from the binder included in the positive active material layer (120) and the coating layer (220). The binder may be omitted.

[0235] The content of the binder may be 0.1% to 10% by weight, 1% to 5% by weight, 1% to 3% by weight, or 1% to 2% by weight based on the total weight of the solid electrolyte layer.

[0236] Examples and comparative examples of the present invention are described below. However, the following examples are merely one example of the present invention, and the present invention is not limited to the following examples.

[0237]

[0238] [Example]

[0239] Manufacturing of all-solid-state batteries

[0240] Example 1

[0241] (1) Preparation of surface-modified binder

[0242] A surface-modified binder (PTFE) was prepared by plasma treatment of polytetrafluoroethylene (PTFE) through discharge at atmospheric pressure under conditions of 10 kV, 1.5 Hz, and 150 A. At this time, it was confirmed using FT-IR that -NH2 functional groups were formed on the surface of the binder surface-modified through the plasma treatment. Additionally, X-ray photoelectron spectroscopy (XPS) was performed to calculate the content of -NH2 formed on the surface of the binder as an atomic percentage (atomic %). The surface-modified binder was 3.6 × 10⁻⁶ -8 mol / cm 3 The content of the above -NH2 functional groups, a surface roughness of 12 nm, and 35 mJ / m² 2 It was confirmed that it has surface energy.

[0243] (2) Preparation of positive electrode active material

[0244] Li2S, LiI, and AlI3 were mixed in a weight ratio of 50:5:15. The mixture was mechanically milled using a ball mill to produce a Li2S-LiI-AlI3 composite. At this time, the first milling was performed at 25°C and 450 rpm for 10 hours, and the milling energy applied to the sample during the first milling was 20 G.

[0245] Subsequently, the prepared Li2S-LiI-AlI3 composite and carbon nanofiber (CNF) were mixed in a weight ratio of 70:10. The mixture was mechanically milled a second time using a ball mill to prepare the Li2S-LiI-AlI3-CNF composite. At this time, the second milling was performed at 25°C and 450 rpm for 10 hours, and the milling energy applied to the sample during the second milling was 20 G.

[0246] (3) Preparation of the anode

[0247] As the positive active material, the Li2S-LiI-AlI3-CNF composite prepared in step (2) was prepared, and as the solid electrolyte, Li6PS5Cl (D50 = 1 μm, crystalline), which is an argyrodite-type crystal, was prepared. The positive active material, the solid electrolyte, and the surface-modified PTFE binder were physically mixed in a mortar and pestle in a weight ratio of 80:20:1.2 to prepare a positive composite.

[0248] Subsequently, the anode composite was placed on one side of an anode current collector made of aluminum foil coated with carbon on one side, thereby manufacturing a laminate having a structure of an anode current collector (Al foil) / anode active material layer (anode composite). The anode was manufactured by plate pressing the laminate at a pressure of 200 MPa for 10 minutes. At this time, the thickness of the anode active material layer was approximately 100 μm, and the thickness of the anode current collector was approximately 20 μm.

[0249] (4) Preparation of the cathode

[0250] A stainless steel (SUS) foil with a thickness of 10 μm was prepared as a cathode current collector. As a metal-carbon composite, carbon black (CB) with a primary particle size of about 30 nm and silver (Ag) particles with an average particle diameter of about 60 nm were prepared.

[0251] 4 g of a mixed powder, prepared by mixing the carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1, was placed in a container, and 4 g of a methylpyrrolidone (NMP) solution containing 7 wt% of a polyvinylidene fluoride (PVDF) binder (Kureha # 9300) was added to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the prepared mixed solution. The prepared slurry was applied to the SUS foil using a bar coater, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 10 hours to produce a laminate. The surface of the manufactured laminate was flattened by cold roll pressing to produce a cathode having a coating layer / cathode current collector (SUS foil) structure. At this time, the thickness of the coating layer was approximately 15 μm, and the surface area of ​​the coating layer and the cathode current collector were the same.

[0252] (5) Preparation of a solid electrolyte layer

[0253] 98.5 parts by weight of Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal, and 1.5 parts by weight of an acrylic binder were mixed. Octyl acetate was added to the mixture while stirring to prepare a solid electrolyte slurry. The prepared solid electrolyte slurry was applied using a bar coater onto a 15 μm thick nonwoven fabric placed on a 75 μm thick PET substrate, dried at 80°C in air for 10 minutes, and then vacuum dried at 40°C for 2 hours to prepare a solid electrolyte layer.

[0254] (6) Manufacturing of lithium-sulfur all-solid-state batteries

[0255] A laminate was prepared by placing a solid electrolyte layer prepared in step (5) on the coating layer of the cathode prepared in step (4), and placing a positive electrode such that the positive active material layer of the positive electrode prepared in step (3) contacts the solid electrolyte layer (see FIG. 7). The laminate was subjected to plate press treatment at 85°C for 30 minutes at a pressure of 500 MPa. By this press treatment, the solid electrolyte layer is sintered, which can improve battery characteristics, and the thickness of the sintered solid electrolyte layer was approximately 45 μm. In addition, the density of the Li6PS5Cl solid electrolyte, which is an argyrodite-type crystal contained in the sintered solid electrolyte layer, was 1.6 g / cc, and the area of ​​the solid electrolyte layer was the same as the area of ​​the cathode layer.

[0256] Subsequently, a lithium-sulfur all-solid-state battery was manufactured by placing the pressurized laminate into a pouch and vacuum sealing it. Parts of the positive and negative current collectors were extended outside the sealed battery to serve as the positive and negative terminals.

[0257]

[0258] Example 2

[0259] In step (3), a primary mixture was prepared by mixing the positive active material and the surface-modified PTFE binder in a weight ratio of 80:0.6, and a secondary mixture was prepared by mixing the solid electrolyte and the PTFE binder in a weight ratio of 20:0.6, and then the positive composite was prepared by mixing the primary mixture and the secondary mixture in a weight ratio of 1:1, except that a lithium-sulfur all-solid-state battery was prepared in the same manner as in Example 1.

[0260]

[0261] Example 3

[0262] In step (3) above, a lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 1, except that the positive active material, the solid electrolyte, and the surface-modified PTFE binder were mixed in a weight ratio of 80:20:2.

[0263]

[0264] Comparative Example 1

[0265] A lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) that has not undergone a surface modification process was used instead of the surface-modified PTFE binder manufactured in step (1).

[0266]

[0267] Comparative Example 2

[0268] A lithium-sulfur all-solid-state battery was manufactured in the same manner as in Example 2, except that polytetrafluoroethylene (PTFE) that has not undergone a surface modification treatment process was used instead of the surface modification binder (PTFE) manufactured in step (1).

[0269]

[0270] Evaluation Example: Battery Performance Evaluation

[0271] For the lithium-sulfur all-solid-state batteries prepared in Examples 1 to 3 and Comparative Example 1 and Comparative Example 2 above, battery performance such as capacity, lifespan, and rate characteristics was evaluated as follows.

[0272] (1) Electrode capacity

[0273] The all-solid-state battery was charged at 45°C with a constant current of 0.1 C to an upper voltage limit of 2.8 V, and then discharged to a lower voltage limit of 1.0 V with a constant current of 0.1 C. At this time, the measured discharge capacity was evaluated as the electrode capacity.

[0274] (2) Rate characteristics

[0275] The all-solid-state battery was charged at 45°C with a constant current of 0.05 C to an upper voltage limit of 2.8 V, and then discharged with a constant current of 0.05 C to a lower voltage limit of 1.0 V. After performing 5 charge-discharge cycles under the above conditions, 5 charge-discharge cycles were performed for each while changing the C-rate sequentially to 0.1C, 0.2C, 0.33C, 0.5C, 1.0C, 2.0C, and 0.05C. At this time, the ratio of the discharge capacity at the last 0.05C to the 1C expressed capacity was evaluated as the rate capability. Rate capability is an indicator that can evaluate how well the battery maintains performance under high-speed charge-discharge conditions; a higher rate capability value indicates that the internal resistance of the electrode is low and the interface is maintained stably.

[0276] (3) Lifespan

[0277] The all-solid-state battery was charged at 45°C with a constant current of 0.05 C to an upper voltage limit of 2.8 V, and then discharged to a lower voltage limit of 1.0 V with a constant current of 0.05 C. The number of cycles until the state-of-health (SOH) decreased to 80% was measured under the above conditions. SOH (state-of-health) represents the current performance relative to the initial performance of the cell, and a higher SOH value indicates that the battery has long-life characteristics.

[0278]

[0279] Separator Electrode Capacity (mAh / g) Rate Characteristic (%) SOH (Number of Cycles) Example 1 19559120 Example 2 31081180 Example 3 19559160 Comparative Example 1 1955960 Comparative Example 2 2156385

[0280]

[0281] Referring to Table 1 above, the all-solid-state batteries of Examples 1 to 3 exhibited superior battery performance characteristics, such as capacity, lifespan, and rate characteristics, compared to Comparative Examples 1 and 2. More specifically, it was confirmed that the all-solid-state batteries of Examples 1 to 3, by including a surface-modified binder together with a specific positive electrode active material and a solid electrolyte, possess superior capacity, lifespan, and rate characteristics compared to Comparative Examples 1 and 2, which used a binder that did not undergo a surface modification process.

[0282] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

positive current collector; and It includes a positive active material layer disposed on at least one surface of the positive current collector, and The above positive active material layer comprises a positive active material, a solid electrolyte, and a surface-modified binder, for a positive electrode for an all-solid-state battery. In Article 1, The surface-modified binder comprises a functional group capable of forming a bond with a hydroxyl group on its surface, and A positive electrode for an all-solid-state battery, wherein the functional group comprises an amino group, an amide group, a trifluoromethyl group, or a combination thereof. In Article 2, The content of the functional group formed on the surface of the surface-modified binder is 1.0 × 10 -8 mol / cm 3 Up to 3.0 × 10 -6 mol / cm 3 Phosphorus, cathode for all-solid-state batteries. In Article 1, The above-mentioned surface-modified binder comprises polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyacrylate, polyethylene oxide, polypropylene oxide, polyacrylonitrile, or a combination thereof, for a positive electrode for an all-solid-state battery. In Article 1, The surface-modified binder has a surface roughness of 8 nm to 20 nm and a surface energy of 30 mJ / m² 2 Up to 60 mJ / m 2 Phosphorus, cathode for all-solid-state batteries. In Article 1, A positive electrode for an all-solid-state battery, wherein the content of the surface-modified binder is 0.5% to 5% by weight based on the total weight of the positive electrode active material layer. In Article 1, A positive electrode for an all-solid-state battery, wherein the weight ratio of the surface-modified binder and the solid electrolyte is 1:5 to 1:

40. In Article 1, The above-mentioned positive active material comprises a complex of a sulfur-based material, a metal halide salt, and a carbon-based material, and The above sulfur-based materials are S8 and Li2S n A positive electrode for an all-solid-state battery comprising at least one of (1 ≤ n ≤ 8, where n is an integer). In Article 8, A positive electrode for an all-solid-state battery, wherein the metal halide salt comprises a first metal halide salt comprising an alkali metal and a second metal halide salt comprising a boron group metal. In Article 9, The first metal halide salt comprises LiF, LiCl, LiBr, LiI, or a combination thereof, and The above second metal halide salt comprises AlF3, AlCl3, AlBr3, AlI3, GaF3, GaCl3, GaBr3, GaI3, InF3, InCl3, lnBr3, lnI3, TiF3, TiCl3, TiBr3, TiI3, or a combination thereof, for an anode for an all-solid-state battery. In Article 9, A positive electrode for an all-solid-state battery, wherein the content of the first metal halide salt is 2.5% to 15% by weight based on the total weight of the composite, and the content of the second metal halide salt is 7.5% to 45% by weight based on the total weight of the composite. In Article 8, The above carbon-based material comprises a carbon nanofiber (CNF), a carbon nanotube (CNT), a carbon nanobelt, a carbon nanorod, or a combination thereof, for a cathode for an all-solid-state battery. In Article 8, The above composite of the sulfur-based material, metal halide salt, and carbon-based material comprises 20% to 80% by weight of the sulfur-based material, 10% to 60% by weight of the metal halide salt, and 1% to 30% by weight of the carbon-based material, for a positive electrode for an all-solid-state battery. In Article 1, A positive electrode for an all-solid-state battery, wherein the content of the positive electrode active material is 50% to 90% by weight based on the total weight of the positive electrode active material layer. In Article 1, The above solid electrolyte is Li 7-a-c M a PS 6-c X c It includes an argyrodite-type compound represented by (0≤a≤2, 0≤c≤2), and The above X is F, Br, Cl, I, or a combination thereof, and The above M is candium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof, Cathode for all-solid-state batteries. In Article 1, A positive electrode for an all-solid-state battery, wherein the content of the solid electrolyte is 10% to 30% by weight based on the total weight of the positive electrode active material layer. A step of manufacturing a surface-modified binder by performing a surface treatment process on the binder; A step of preparing an anode slurry by mixing an anode active material, the surface-modified binder, and a solid electrolyte; and A method for manufacturing a positive electrode for an all-solid-state battery, comprising the step of applying the above positive electrode slurry to one surface of a positive electrode current collector. In Article 17, A method for manufacturing a positive electrode for an all-solid-state battery, wherein the above surface treatment process is performed by plasma treatment, oxidation treatment, etching treatment, UV treatment, laser treatment, or a combination thereof. In Article 17, The step of manufacturing the anode slurry above is, A step of preparing a primary mixture by mixing the above positive active material and the above surface modification binder; A step of preparing a secondary mixture by mixing the solid electrolyte and the surface-modified binder; and A method for manufacturing a positive electrode for an all-solid-state battery, comprising the step of mixing the first mixture and the second mixture. Anode for an all-solid-state battery according to paragraph 1; cathode; and A solid-state battery comprising a solid electrolyte layer disposed between the anode and the cathode.

Images