Positive electrode active material, method for manufacturing same, and all-solid-state battery comprising same

Abstract

The present invention relates to a positive electrode active material, a method of manufacturing same, and an all-solid-state battery comprising same. The positive electrode active material includes: a core particle including a lithium transition metal composite oxide; and a surface roughness (SR) coating layer positioned on the surface of the core particle, wherein a coating area of the SR coating layer is 40% to 100% with respect to a total surface area of the core particle, and the SR coating layer has a first surface roughness (Ra, roughness average) of 0.45 μm to 1.2 μm.

Description

Anode active material, method for manufacturing the same, and all-solid-state battery including the same

[0001] The present invention relates to a positive electrode active material, a method for manufacturing the same, and an all-solid-state battery comprising 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 even in the event of a short circuit.

[0004] The problem that the present invention aims to solve is to provide a positive electrode active material suitable for a dry process while ensuring appropriate interfacial bonding strength between the positive electrode active material layer and the solid electrolyte layer.

[0005] Another problem that the present invention aims to solve is to provide an all-solid-state battery with reduced internal resistance (Rion) and improved lifespan and capacity characteristics.

[0006] A positive electrode active material according to one embodiment of the present invention comprises a core particle comprising a lithium transition metal composite oxide; and a Surface Roughness (SR) coating layer located on the surface of the core particle, wherein the coating area of ​​the SR coating layer is 40% to 100% of the total surface area of ​​the core particle and has a first surface roughness (Ra, roughness average) of 0.45 μm to 1.2 μm.

[0007] A method for manufacturing a positive electrode active material according to another embodiment of the present invention comprises the steps of: preparing a core particle comprising a lithium transition metal composite oxide; and forming a Surface Roughness (SR) coating layer on the surface of the core particle, wherein the step of forming the SR coating layer comprises the steps of mixing the core particle with a metal oxide at 1,000 rpm to 15,000 rpm and pressing at 0.01 MPa to 100 MPa, and wherein the amount of the metal oxide added in the step of forming the SR coating layer is less than 3 parts by weight per 100 parts by weight of the core particle.

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

[0009] A positive electrode active material according to one embodiment of the present invention includes an SR coating layer on its surface, and by satisfying a specific range for the coating area of ​​the SR coating layer and a first surface roughness (Ra), the interfacial bonding strength between the positive electrode active material layer including the positive electrode active material and the solid electrolyte layer can be improved.

[0010] In addition, a method for manufacturing a positive electrode active material according to one embodiment of the present invention can provide a positive electrode active material suitable for a dry process by controlling the step of forming an SR coating layer on the surface of a core particle comprising a lithium transition metal composite oxide, thereby securing appropriate interfacial bonding strength between the positive electrode active material layer and the solid electrolyte layer.

[0011] In addition, an all-solid-state battery according to another embodiment of the present invention has excellent lifespan and capacity characteristics by including a positive electrode containing the positive electrode active material.

[0012] FIG. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0013] Figure 2 is a scanning electron microscope (SEM) image of a positive electrode active material without an SR coating layer formed.

[0014] FIG. 3 is an SEM image of a positive electrode active material according to one embodiment of the present invention.

[0015] Figures 4 and 5 illustrate a method for measuring the surface roughness of an anode active material according to one embodiment of the present invention.

[0016] Figure 6 shows an SEM image of the positive electrode active material of Example 1 and a grayscale obtained using it.

[0017] Figure 7 shows an SEM image of the positive electrode active material of Example 2 and a grayscale obtained using it.

[0018] FIGS. 8 and 9 are cross-sectional views of an all-solid-state battery according to another embodiment of the present invention.

[0019] <Explanation of Symbols>

[0020] 1: All-solid-state battery

[0021] 100: Positive electrode 110: Positive electrode current collector

[0022] 120: Positive electrode active material layer 200: Negative electrode

[0023] 210: Cathode current collector 220: Coating layer

[0024] 230: Lithium metal layer 300: Solid electrolyte layer

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In this specification, “one surface” and “another surface” are terms used to distinguish and describe different surfaces of an object, wherein “one surface” refers to a specific surface of an object, and “another surface” refers to a surface located on the opposite side or in a different direction relative to the one surface.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Unless otherwise defined in this specification, the particle diameter or size may be the average particle diameter. The average particle diameter refers to the average value of the diameter of the particles according to the cumulative volume in the particle size distribution. The particle size distribution 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 from images obtained by a transmission electron microscope (TEM) or a scanning electron microscope (SEM). Alternatively, the average particle diameter may be calculated by measuring using a measuring device utilizing dynamic lightscattering, performing data analysis to count the number of particles for each particle size range, and then calculating the average particle diameter.

[0034] In addition, 'D10', 'D50', and 'D90' represent the particle size at the 10% point (D10), 50% point (D50), and 90% point (D90) of the volume cumulative distribution according to particle size, respectively. For example, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000, which irradiates ultrasound of approximately 28 kHz with an output of 60 W) to measure the difference in diffraction patterns according to particle size as the particles pass through the laser beam, thereby calculating the volume cumulative distribution according to particle size, and D10, D50, and D90 can be measured by calculating the particle diameter at the points that are 10%, 50%, and 90% of the volume cumulative distribution according to particle size in the measuring device.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Generally, currently commercialized lithium-ion batteries utilize liquid electrolytes and polymer separators. While the liquid electrolyte can penetrate the pores between the anode and cathode to function as a conduction pathway for lithium ions, it poses risks such as fire and explosion due to continuous charging, discharging, or degradation. Additionally, polymer separators are susceptible to damage due to their weak mechanical properties and can cause short circuits by allowing physical contact between the anode and cathode.

[0042] Consequently, there is growing interest in solid electrolytes that can replace liquid electrolytes and polymer separators while ensuring high stability and energy density. Solid electrolytes can be classified into sulfide-based, oxide-based, and polymer-based types. Sulfide-based solid electrolytes exhibit excellent ionic conductivity but suffer from low electrochemical stability; oxide-based solid electrolytes offer relatively good ionic conductivity and electrochemical stability but have high interfacial resistance; and polymer-based solid electrolytes have low interfacial resistance due to their excellent flexibility but very low ionic conductivity. Therefore, research is continuing on all-solid-state batteries that can ensure stability while maintaining excellent performance, such as ionic conductivity.

[0043] More specifically, interfacial resistance plays a crucial role in the performance and efficiency of all-solid-state batteries and refers to the electrical resistance occurring at the boundaries between the components of the battery. When using solid electrolytes, contact between solid components may be incomplete or uneven compared to liquid electrolytes, making the movement of ions or electrons at the interface susceptible to resistance. Consequently, high interfacial resistance can reduce the output and efficiency of the all-solid-state battery, increase energy loss leading to a decrease in charge / discharge rates, and shorten the battery's lifespan due to continuous damage or degradation of the interface. Therefore, research is ongoing on all-solid-state batteries capable of lowering interfacial resistance by improving the bonding strength between solid components.

[0044] A positive electrode active material according to one embodiment of the present invention includes an SR coating layer on its surface, and by satisfying a specific range for the coating area of ​​the SR coating layer and a first surface roughness (Ra), the interfacial bonding strength between the positive electrode active material layer and the solid electrolyte layer including the positive electrode active material can be improved.

[0045] In addition, when manufactured by a dry process, it may be difficult to control the surface roughness characteristics of the positive active material layer, but the method for manufacturing a positive active material according to one embodiment of the present invention can secure appropriate interfacial bonding between the positive active material layer and the solid electrolyte layer by controlling the step of forming an SR coating layer on the surface of a core particle containing a lithium transition metal composite oxide, and can provide a positive active material suitable for a dry process.

[0046] FIG. 2 is a scanning electron microscope (SEM) image of a positive electrode active material without an SR coating layer formed thereon, and FIG. 3 is an SEM image of a positive electrode active material according to an embodiment of the present invention. As can be seen in FIG. 2 and 3, it can be confirmed that an SR coating layer is formed on the surface of the positive electrode active material according to an embodiment of the present invention.

[0047] Specifically, according to one embodiment of the present invention, an SR coating layer can be formed on the surface of a core particle containing a lithium transition metal composite oxide through a step of mixing at 1,000 rpm to 15,000 rpm and a step of pressurizing at 0.01 MPa to 100 MPa. By controlling the process conditions and simultaneously controlling the content of the metal oxide introduced in the step of forming the SR coating layer, the coating area and surface roughness can be adjusted to a desirable range, thereby improving the interfacial bonding strength between the positive electrode active material layer containing the positive electrode active material and the solid electrolyte layer, while simultaneously ensuring excellent interfacial stability.

[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] positive active material

[0050] A positive electrode active material according to one embodiment of the present invention comprises a core particle comprising a lithium transition metal composite oxide; and an SR coating layer located on the surface of the core particle, wherein the coating area of ​​the SR coating layer is 40% to 100% of the total surface area of ​​the core particle and has a first surface roughness (Ra, roughness average) of 0.45 μm to 1.2 μm.

[0051] The above positive active material may include core particles comprising a lithium transition metal complex oxide.

[0052] The average particle size (D50) of the core particles may be 1 μm to 25 μm. For example, the average particle size (D50) of the core particles may be 1.5 μm to 23 μm, or 2 μm to 20 μm.

[0053] As the core particles, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. For example, the core particles may include one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof.

[0054] The above lithium transition metal composite oxide may include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, or a combination thereof.

[0055] In addition, the lithium transition metal complex oxide can be represented by the following chemical formula 1.

[0056] [Chemical Formula 1]

[0057] Li x M 1 y M 2 z M 3 1-y-z O 2-a X a

[0058] In the above chemical formula 1,

[0059] 0.5≤x≤1.8, 0 <y≤1, 0≤z≤1, 0≤a≤0.05, 및 0≤y+z≤1이고,

[0060] M 1 , M 2 and M 3Each is independently one or more elements selected from the group consisting of Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, and La, and

[0061] X is one or more elements selected from F, S, P and Cl.

[0062] Specifically, the lithium transition metal composite oxide may include a lithium cobalt-based oxide. For example, the lithium cobalt-based oxide may include lithium cobalt oxide, lithium nickel-cobalt-manganese oxide, lithium nickel-cobalt-manganese-aluminum oxide, lithium nickel-manganese-cobalt oxide, or a combination thereof. In this case, the content of the cobalt may be greater than 0 wt% to 30 wt% or less, 0.1 wt% to 30 wt%, 0.2 wt% to 25 wt%, 0.5 wt% to 20 wt%, or 1 wt% to 30 wt% with respect to the total weight of the positive electrode active material.

[0063] In addition, the positive active material may include an SR coating layer located on the surface of the core particle.

[0064] The coating area of ​​the SR coating layer may be 40% to 100% of the total surface area of ​​the core particle. For example, the coating area of ​​the SR coating layer may be 45% to 100%, 55% to 100%, 70% to 100%, or 80% to 100% of the total surface area of ​​the core particle. By satisfying the above range, the interfacial bonding strength between the positive active material layer containing the positive active material and the solid electrolyte layer can be improved, and excellent interfacial stability can be secured at the same time.

[0065] The above coating area may be calculated using an image obtained for the positive electrode active material. Specifically, the above coating area may be calculated through Elemental Dispersive X-ray Spectroscopy (EDX) analysis using an SEM image obtained for the positive electrode active material.

[0066] The above SR coating layer may include Zr, Li, Al, Mg, Ti, Si, Ce, Nb, or oxides thereof. For example, the above SR coating layer may include metal oxides including ZrO2, ZrO, Li3PO4, LiF, Li2O, Al2O3, MgO, TiO2, SiO2, CeO2, Nb2O5, or a combination thereof.

[0067] The average thickness of the SR coating layer may be 50 nm to 500 nm. For example, the average thickness of the SR coating layer may be 60 nm to 500 nm or 80 nm to 350 nm.

[0068] According to one embodiment of the present invention, the positive electrode active material may have a first surface roughness (Ra, roughness average) of 0.45 μm to 1.2 μm. For example, the first surface roughness (Ra) of the positive electrode active material having the SR coating layer formed on its surface may be 0.5 μm to 1.1 μm, 0.6 μm to 1.05 μm, or 0.75 μm to 1.0 μm.

[0069] The above positive active material may have a second surface roughness (Rq, root mean square roughness) of 0.07 μm to 2.0 μm. For example, the second surface roughness (Rq) of the positive active material having the SR coating layer formed on its surface may be 0.1 μm to 1.6 μm, 0.15 μm to 1.2 μm, or 0.2 μm to 0.95 μm.

[0070] The ratio (Ra / Rq) of the first surface roughness (Ra) and the second surface roughness (Rq) may be greater than 0.75. For example, the ratio (Ra / Rq) of the first surface roughness (Ra) and the second surface roughness (Rq) may be 0.8 or higher, 0.85 or higher, 0.95 or higher, or 1.1 or higher, and may be 1.5 or lower, 1.4 or lower, 1.35 or lower, or 1.3 or lower.

[0071] The above positive active material may have a third surface roughness (Rz, ten-point mean roughness) of 0.03 μm to 3.6 μm. For example, the third surface roughness (Rz) of the positive active material having the SR coating layer formed on its surface may be 0.1 μm to 3.6 μm, 0.5 μm to 3.55 μm, 1.1 μm to 3.55 μm, 1.5 μm to 3.5 μm, or 2.0 μm to 3.5 μm.

[0072] The ratio (Ra / Rq) of the first surface roughness (Ra) and the third surface roughness (Rz) may be 0.3 or less. For example, the ratio (Ra / Rq) of the first surface roughness (Ra) and the second surface roughness (Rq) may be 0.3 or less, 0.29 or less, or 0.28 or less, and may be 0.1 or more, 0.15 or more, or greater than 0.23.

[0073] By satisfying the above ranges for each of the first to third surface roughnesses, the interfacial bonding strength between the positive active material layer containing the positive active material and the solid electrolyte layer can be improved, and at the same time, excellent interfacial stability can be secured.

[0074] The first to third surface roughnesses may be measured according to JIS B 0601 (2013). Specifically, the first surface roughness (Ra) refers to the arithmetic mean roughness, the third surface roughness (Rz) refers to the ten-point mean roughness, and the second surface roughness (Rq) refers to a roughness value calculated using the root-mean-square (rms) method. For example, each of the first to third surface roughnesses may be calculated based on the grayscale obtained from the SEM image of the positive electrode active material.

[0075] Figures 4 and 5 illustrate a method for measuring the surface roughness of an anode active material according to one embodiment of the present invention.

[0076] FIG. 4 is an SEM image of a particle comprising a core particle containing polyvinylpyrrolidone (PVP) and polystyrene (PS) and an SR coating layer containing silica, wherein SEM 1 is for a particle having a molecular weight of 10 kDa and SEM 2 is for a particle having a molecular weight of 360 kDa. FIG. 5 is a profile obtained using a detection device such as an InLens SE1 detector for the SEM images of SEM 1 and SEM 2, which can be used to obtain a grayscale. In this way, multiple grayscale values ​​for circles of different radii can be obtained and normalized to calculate surface roughness.

[0077] Method for manufacturing positive electrode active material

[0078] A method for manufacturing a positive electrode active material according to another embodiment of the present invention comprises the steps of: preparing a core particle comprising a lithium transition metal composite oxide; and forming a Surface Roughness (SR) coating layer on the surface of the core particle, wherein the step of forming the SR coating layer comprises the steps of mixing the core particle with a metal oxide at 1,000 rpm to 15,000 rpm and pressing at 0.01 MPa to 100 MPa, and wherein the amount of the metal oxide added in the step of forming the SR coating layer is less than 3 parts by weight per 100 parts by weight of the core particle.

[0079] The description of the lithium transition metal composite oxide and the core particles containing it is as described above.

[0080] The step of forming the above SR coating layer can be performed by mixing the core particles with a metal oxide and applying pressure. The description of the above SR coating layer is as previously described.

[0081] The step of forming the SR coating layer can be performed at 25°C to 350°C. For example, the step of forming the SR coating layer can be performed at 25°C to 300°C or at 25°C to 250°C.

[0082] Specifically, the mixing step may be performed at 25°C to 150°C at 1,000 rpm to 15,000 rpm. For example, the mixing step may be performed at 25°C to 150°C, 25°C to 120°C, or 25°C to 100°C at 2,000 rpm to 15,000 rpm, 3,500 rpm to 14,000 rpm, or 5,000 rpm to 12,000 rpm.

[0083] The above pressurizing step may be performed at 180°C to 350°C at 0.01 MPa to 100 MPa. For example, the above pressurizing step may be performed at 180°C to 320°C, 180°C to 300°C, or 180°C to 250°C at 0.05 MPa to 60 MPa, 0.1 MPa to 35 MPa, or 1 MPa to 10 MPa.

[0084] Each of the above mixing step and the above pressurizing step may be performed using a Nobilta mixer, Henschel mixer, High intensity mixer, Jet mill, Fitz mill, Twin screw extruder, or single screw extruder, but is not limited thereto.

[0085] In addition, the metal oxide may include ZrO2, ZrO, Li3PO4, LiF, Li2O, Al2O3, MgO, TiO2, SiO2, CeO2, Nb2O5, or a combination thereof.

[0086] In the step of forming the SR coating layer, the amount of the metal oxide added may be less than 3 parts by weight per 100 parts by weight of the core particles. For example, in the step of forming the SR coating layer, the amount of the metal oxide mixed with the core particles may be less than 3 parts by weight or 2.5 parts by weight or less per 100 parts by weight of the core particles, or 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more.

[0087] By controlling the process conditions of the step of forming the SR coating layer as described above, the coating area and surface roughness can be adjusted to a desirable range, thereby improving the interfacial bonding strength between the positive active material layer containing the positive active material and the solid electrolyte layer, while simultaneously ensuring excellent interfacial stability.

[0088] All-solid-state battery

[0089] A solid-state battery according to another embodiment of the present invention comprises a positive electrode including the positive active material; a negative electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0090] FIG. 9 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 9, an all-solid-state battery (1) according to one embodiment of the present invention may include a positive electrode (100) composed of a positive electrode current collector (110) and a positive electrode active material layer (120), a negative electrode (200) composed of a negative electrode current collector (210) and a coating layer (220), 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.

[0091] anode

[0092] A solid-state battery (1) according to another embodiment of the present invention comprises a positive electrode (100) comprising the positive electrode active material. More specifically, the positive electrode (100) may comprise a positive electrode active material layer (120) comprising the positive electrode active material. The description of the positive electrode active material is as described above.

[0093] The DC-IR (Direct Current Internal Resistance) value between the positive active material layer and the solid electrolyte layer, measured by Electrochemical Impedance Spectroscopy (EIS), may be 5 Ω to 50 Ω. For example, the DC-IR value between the positive active material layer (120) and the solid electrolyte layer (300), measured by EIS, may be 5 Ω to 40 Ω, 5 Ω to 35 Ω, or 5 Ω to 20 Ω.

[0094] The anode (100) may include an anode current collector (110). The anode (100) may include an anode current collector (110) and an anode active material layer (120) disposed on at least one surface of the anode current collector (110). More specifically, the anode may include an anode current collector (110) and an anode active material layer (120) on one or both surfaces of the anode current collector (110). The anode (100) may include an anode active material layer (120) comprising an anode current collector (110) and the anode active material disposed on at least one surface thereof.

[0095] 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.

[0096] 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 25 μm, or 10 μm to 20 μm.

[0097] 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 0.1 μm to 4 μm. By including the carbon layer, the bonding strength between the anode current collector and the anode active material layer can be further improved.

[0098] The content of the positive active material in the positive active material layer may be 90% to 99.5% by weight, 92% to 99.5% by weight, or 95% to 99% by weight with respect to 100% by weight of the positive active material layer.

[0099] In addition, the positive electrode active material layer (120) may include a solid electrolyte in addition to the positive electrode active material. As a specific example, the solid electrolyte may be a sulfide-based solid electrolyte.

[0100] The above sulfide-based solid electrolyte can provide an ion transfer pathway within the anode active material layer. Since the anode active material layer according to one embodiment of the present invention may have a further reduced internal resistance by including the aforementioned anode active material and the sulfide-based solid electrolyte, the cycle characteristics of the battery including the same can be further improved.

[0101] The above sulfide-based solid electrolyte may include a complex of Li2S and a solid electrolyte, and may be, for example, an inorganic solid electrolyte. Additionally, the above sulfide-based solid electrolyte may include Li, S and / or P, and may optionally include halogen elements.

[0102] For example, the above sulfide-based solid electrolyte 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-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include one or more selected from (0≤x≤2).

[0103] The above sulfide-based solid electrolyte 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).

[0104] 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.

[0105] 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.

[0106] In addition, the above sulfide-based solid electrolyte is 1 × 10⁻⁶ at room temperature -5 It can have an ionic conductivity of S / cm or greater. For example, the ionic conductivity of the sulfide-based solid electrolyte 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.

[0107] According to another embodiment of the present invention, the positive electrode active material layer may further include a solid electrolyte in addition to the sulfide-based solid electrolyte. Specifically, the positive electrode active material layer may include, in addition to the aforementioned sulfide-based solid electrolyte, a sulfide-based solid electrolyte and / or an oxide-based solid electrolyte different therefrom.

[0108] For example, the above positive active material layer 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 mS 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 sulfide-based 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 Lay 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. 구체적인 일례로, 상기 고체 전해질은 Li6PS5Cl을 포함할 수 있다.

[0109] In addition, the solid electrolyte in the positive electrode active material layer (120) may be the same as or different from the solid electrolyte in the solid electrolyte layer (300).

[0110] 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).

[0111] The content of the sulfide-based solid electrolyte may be 10% to 40% by weight with respect to the total weight of the positive electrode active material layer. For example, the content of the sulfide-based solid electrolyte in the positive electrode active material layer may be 15% to 40% by weight, 20% to 40% by weight, or 20% to 35% 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 sulfide-based solid electrolyte, the capacity characteristics of the battery containing it can be further improved.

[0112] The weight ratio of the positive active material and the sulfide-based solid electrolyte in the positive active material layer 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 and the sulfide-based solid electrolyte, the cycle characteristics of the battery can be maintained at a certain level or higher while securing excellent capacity characteristics.

[0113] According to another embodiment of the present invention, the positive active material layer may further include a binder, a conductive material, etc.

[0114] The above positive active material layer may include a binder comprising one or more selected from styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), carboxylated nitrile-butadiene rubber (XNBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, and polyethylene. By further including such a binder, the positive active material layer can more effectively repair the contact detachment and weakened network between the components resulting from repeated charging and discharging. In other words, since the bonding strength between solid particles within the positive active material layer can be maintained more easily, the effect of improving the battery life can be maximized.

[0115] The content of the binder 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 based on the total weight of the positive electrode active material layer.

[0116] The conductive material described above is conductive without causing chemical changes and can improve the electrical conductivity of the anode active material and the sulfide-based 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.

[0117] 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 based on the total weight of the positive electrode active material layer.

[0118] According to another embodiment of the present invention, the positive active material layer may further include additives such as a filler, 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 filler, coating agent, dispersant, ion conductivity aid, etc., and are not particularly limited.

[0119] For example, the filler may include organic fillers and / or inorganic fillers, and the filler may have an elastic modulus of 1 MPa to 2,000 MPa, 1 MPa to 500 MPa, or 5 MPa to 100 MPa, and an average particle size of 0.01 μm to 10 μm, 0.05 μm to 5 μm, or 0.1 μm to 5 μm. The elastic modulus of the filler may be measured using a tensile testing machine on a sample obtained by molding the organic filler at 150°C to 200°C for 10 minutes using a vacuum pressure press. The average particle size of the filler may be measured using a laser scattering particle size distribution analyzer.

[0120] cathode

[0121] A solid-state battery (1) according to another embodiment of the present invention includes a negative electrode (200).

[0122] Additionally, the cathode (200) may include a cathode current collector (210) and a coating layer (220). The cathode current collector may provide a reference surface on which the coating layer is placed.

[0123] 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 (210) 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 (210) may be composed of one of the metals described above, or may include an alloy or coating material of two or more metals.

[0124] 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.

[0125] According to another embodiment of the present invention, the all-solid-state battery may not include a negative electrode current collector. That is, the negative electrode current collector may be omitted.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] The average particle size of the above metal-carbon composite is the median diameter (D50) measured using a laser particle size distribution meter.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] FIG. 9 is a cross-sectional view of an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 9, an all-solid-state battery (1) according to one embodiment of the present invention may include a positive electrode (100) composed of a positive electrode current collector (110) and a positive electrode active material layer (120), a negative electrode (200) composed of a negative electrode current collector (210), a coating layer (220), and a lithium metal layer (230) disposed between the negative electrode current collector (210) and the coating layer (220), 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] According to another embodiment of the present invention, the lithium metal layer may be provided between the negative electrode current collector and the coating layer before assembly of the battery. As a specific example, the lithium metal layer (230) may be disposed as a lithium foil between the negative electrode current collector (210) and the coating layer (220) before assembly of the battery.

[0141] 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).

[0142] Since the above 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 (230) can be used as a negative electrode active material.

[0143] 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.

[0144] 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.

[0145] According to another embodiment of the present invention, the cathode 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 and may form an alloy with lithium.

[0146] 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.

[0147] 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.

[0148] 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, and the amount of lithium precipitated at the negative electrode may decrease, so the energy density and cycle characteristics of the battery may be degraded.

[0149] The above thin film may be formed by vacuum deposition, sputtering, plating, etc., but is not limited thereto.

[0150] According to another embodiment of the present invention, the cathode may further include a carbon layer between the cathode current collector and the solid electrolyte layer. The description of the carbon layer is as described above.

[0151] According to another embodiment of the present invention, the cathode may include a cathode active material layer corresponding to the coating layer (220).

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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 above 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 above Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0156] 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.

[0157] 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.

[0158] The above Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0159] 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.

[0160] As a specific example, the above-mentioned negative electrode active material may include at least one of graphite and Si composites.

[0161] 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.

[0162] 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.

[0163] The above crystalline carbon may include, for example, graphite, and more specifically, may include natural graphite, artificial graphite, or a mixture thereof.

[0164] The above-mentioned cathode may include a binder. The cathode binder can effectively bond the cathode active material particles to each other 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] The above-mentioned cathode may include a conductive material. The description of the conductive material is as previously stated.

[0171] solid electrolyte layer

[0172] A solid-state battery (1) according to another embodiment of the present invention includes a solid electrolyte layer (300) disposed between the positive electrode (100) and the negative electrode (200).

[0173] The above solid electrolyte layer (300) may include a solid electrolyte.

[0174] The above solid electrolyte may include a sulfide-based solid electrolyte, an oxide-based 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).

[0175] The description of the above solid electrolyte is as previously stated.

[0176] 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.

[0177]

[0178] [Example]

[0179] Manufacturing of all-solid-state batteries

[0180] Example 1

[0181] (1) Preparation of positive electrode active material

[0182] LiNi 0.944 Co 0.04 Mn 0.004 Al 0.012 A lithium transition metal composite oxide having the composition of O2 was prepared as a core particle. At this time, the average particle size (D50) of the core particle was 14 μm.

[0183] Zirconia (ZrO2) was prepared as a metal oxide. The core particles and the metal oxide were fed into a blade mixer in a weight ratio of 99:1 and mixed at 5,000 rpm at 25°C for 5 minutes, and then pressurized at 5 MPa at 25°C for 10 minutes using an extruder to produce an anode active material having a coating area of ​​95% on the surface of the core particles.

[0184] (2) Preparation of the anode

[0185] Li6PS5Cl (D50 = 1.0 μm, crystalline), which is an argyrodite-type crystal, was prepared as a sulfide-based solid electrolyte. The positive electrode active material prepared in step (1), the sulfide-based solid electrolyte, carbon nanotube (CNT) conductive material, and PTFE binder were mixed in a weight ratio of 70:25:2:3 to prepare a positive electrode composite.

[0186] 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.

[0187] (3) Preparation of the cathode

[0188] 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 30 nm and silver (Ag) particles with an average particle diameter of 60 nm were prepared.

[0189] 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 cathode slurry was prepared by stirring while adding NMP little by little to the prepared mixed solution. The prepared cathode 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 prepared laminate was flattened by cold rolling press to produce a cathode having a coating layer / cathode current collector 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.

[0190] (4) Preparation of a solid electrolyte layer

[0191] 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.

[0192] (5) Manufacturing of all-solid-state batteries

[0193] A laminate was prepared by placing a solid electrolyte layer prepared in step (4) on the coating layer of the cathode prepared in step (3), and placing a positive electrode such that the positive active material layer of the positive electrode prepared in step (2) contacts the solid electrolyte layer (see FIG. 9). 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.

[0194] Subsequently, the pressurized laminate was placed in a pouch and vacuum-sealed to manufacture an all-solid-state battery. Parts of the positive and negative current collectors were extended outside the sealed battery to serve as the positive and negative terminals.

[0195]

[0196] Example 2

[0197] In step (1) above, the core particles and the metal oxide were introduced into a blade mixer in a weight ratio of 99:1 and mixed at 10,000 rpm at 25°C for 3 minutes, and then pressurized at 5 MPa at 200°C for 10 minutes using an extruder to form an SR coating layer having a coating area of ​​89% on the surface of the core particles, except that an all-solid-state battery was manufactured in the same manner as in Example 1.

[0198]

[0199] Example 3

[0200] In step (1) above, the core particles and the metal oxide were introduced into a blade mixer in a weight ratio of 99:1 and mixed at 25°C at 12,000 rpm for 1 minute, and then pressurized at 180°C at 5 MPa for 10 minutes using an extruder to form an SR coating layer having a coating area of ​​82% on the surface of the core particles, except that an all-solid-state battery was manufactured in the same manner as in Example 1.

[0201]

[0202] Example 4

[0203] In step (1) above, the core particles and the metal oxide were introduced into a blade mixer in a weight ratio of 98:2 and mixed at 5,000 rpm at 25°C for 5 minutes, and then pressurized at 5 MPa at 25°C for 10 minutes using an extruder to form an SR coating layer having a coating area of ​​98% on the surface of the core particles, except that an SR coating layer having a coating area of ​​98% was formed on the surface of the core particles.

[0204]

[0205] Comparative Example 1

[0206] LiNi without a coating layer as a positive active material 0.944 Co 0.04 Mn 0.004 Al 0.012 An all-solid-state battery was manufactured in the same manner as in Example 1, except that a lithium transition metal composite oxide having the composition of O2 was used.

[0207]

[0208] Comparative Example 2

[0209] In step (1) above, the core particles and the metal oxide were introduced into a blade mixer in a weight ratio of 97:3 and mixed at 5,000 rpm at 25°C for 5 minutes, and then pressurized at 5 MPa at 25°C for 10 minutes using an extruder to form an SR coating layer having a coating area of ​​99% on the surface of the core particles, except that an all-solid-state battery was manufactured in the same manner as in Example 1.

[0210]

[0211] Evaluation Example 1: Surface roughness

[0212] For the cathode active materials prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2, SEM images were obtained and grayscale was obtained using a detector (InLens SE1 detector). At this time, multiple grayscale values ​​for circles of different radii were obtained and normalized to calculate the first to third surface roughness, respectively.

[0213]

[0214] Evaluation Example 2: Coating Area

[0215] For the cathode active materials prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2, the coating area was calculated through EDX analysis using SEM images. At this time, the coating area was calculated based on the total surface area of ​​the core particles.

[0216]

[0217] Evaluation Example 3: Binding strength

[0218] For the cathode active materials prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2, the granular bond number (Bo g The binding strength was evaluated by calculating the particle binding coefficient. A higher particle binding coefficient indicates superior binding strength.

[0219] Specifically, according to the following formulas 1 to 3, the particle binding coefficient (Bo g ) was calculated. Equation 1 below is based on the Rumpf model.

[0220] [Equation 1]

[0221]

[0222] [Equation 2]

[0223]

[0224] [Equation 3]

[0225]

[0226] In the above formulas 1 to 3,

[0227] A is the Hamaker constant, and d p is the particle diameter, and d asp is the asperity diameter according to the surface roughness of the particles, and Z0 is the equilibrium separation distance or bond length.

[0228]

[0229] Evaluation Example 4: Internal Resistance (Rion)

[0230] For the all-solid-state batteries prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2, the internal resistance was measured by electrochemical impedance spectroscopy (EIS) analysis at a cell open-circuit voltage of 20 mV and a frequency range of 100 kHz to 1 Hz using a potentiometer (Potentiostat, Product name: ZIVE BP2A, Manufacturer: Won-ATech Co., Ltd., Korea).

[0231]

[0232] Classification Ra(μm) Rq(μm) Rz(μm) Coating Area (%) Bo gRion(Ω) Example 10.5 10.3 92.0 6958331.1 Example 20.7 90.6 32.8 6899228.7 Example 30.9 20.7 73.3 48211 725.8 Example 40.8 70.7 43.1 29810 828.7 Comparative Example 10.4 40.3 31.9 4955840.5 Comparative Example 21.2 11.0 73.9 49914032.2

[0233]

[0234] As shown in Table 1 above, the positive electrode active materials prepared in Examples 1 to 4 satisfied both the surface roughness and the coating area within the desirable range, thereby having a more desirable bonding strength compared to Comparative Examples 1 and 2. Accordingly, the all-solid-state battery containing the positive electrode active materials of Examples 1 to 4 had appropriate interfacial bonding strength between the positive electrode active material layer and the solid electrolyte layer, low internal resistance, and excellent lifespan characteristics. On the other hand, Comparative Example 1 had too low bonding strength and high internal resistance, while Comparative Example 2 had relatively low internal resistance but too high bonding strength, which was undesirable in terms of interfacial uniformity.

[0235] 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

1. Core particles comprising a lithium transition metal complex oxide; and It includes an SR (Surface Roughness) coating layer located on the surface of the core particle, and The coating area of ​​the above SR coating layer is 40% to 100% of the total surface area of ​​the core particle, and A positive electrode active material having a first surface roughness (Ra, roughness average) of 0.5 μm to 1.2 μm.

2. In Paragraph 1, A positive active material having a second surface roughness (Rq, root mean square roughness) of 0.07 μm to 2.0 μm.

3. In Paragraph 2, A positive active material in which the ratio (Ra / Rq) of the first surface roughness (Ra) and the second surface roughness (Rq) is greater than 0.

75.

4. In Paragraph 1, A positive electrode active material having a third surface roughness (Rz, ten-point mean roughness) of 0.03 μm to 3.6 μm.

5. In Paragraph 4, A positive active material in which the ratio (Ra / Rq) of the first surface roughness (Ra) and the third surface roughness (Rz) is 0.3 or less.

6. In Paragraph 1, The above SR coating layer is a positive active material comprising Zr, Li, Al, Mg, Ti, Si, Ce, Nb, or oxides thereof.

7. In Paragraph 1, A positive electrode active material having an average thickness of 50 nm to 500 nm of the SR coating layer.

8. In Paragraph 1, The above lithium transition metal composite oxide is a positive electrode active material comprising a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, or a combination thereof.

9. In Paragraph 1, The above lithium transition metal composite oxide is a positive active material represented by the following chemical formula 1: [Chemical Formula 1] Li x M 1 y M 2 z M 3 1-y-z O 2-a X a In the above chemical formula 1, 0.5≤x≤1.8, 0 <y≤1, 0≤z≤1, 0≤a≤0.05, 및 0≤y+z≤1이고, M 1 , M 2 and M 3 Each is independently one or more elements selected from the group consisting of Ni, Co, Mn, Al, B, Ba, Ca, Ce, Cr, Fe, Mo, Nb, Si, Sr, Mg, Ti, V, W, Zr, and La, and X is one or more elements selected from F, S, P and Cl.

10. In Paragraph 1, The above lithium transition metal composite oxide includes a lithium cobalt-based oxide, and A positive electrode active material having a cobalt content of more than 0 weight% to 30 weight% with respect to the total weight of the positive electrode active material.

11. In Paragraph 8, The above lithium cobalt-based oxide comprises a lithium cobalt oxide, a lithium nickel-cobalt-manganese oxide, a lithium nickel-cobalt-manganese-aluminum oxide, a lithium nickel-manganese-cobalt oxide, or a combination thereof, forming a positive electrode active material.

12. In Paragraph 1, A positive active material having an average particle size (D50) of the core particles of the above-mentioned core particles of 1 μm to 25 μm.

13. A step of preparing core particles comprising a lithium transition metal complex oxide; and The method includes the step of forming an SR (Surface Roughness) coating layer on the surface of the core particles, The step of forming the SR coating layer comprises the step of mixing the core particles with a metal oxide at 1,000 rpm to 15,000 rpm and the step of applying pressure at 0.01 MPa to 100 MPa, and A method for manufacturing an anode active material, wherein the amount of the metal oxide added in the step of forming the SR coating layer is less than 3 parts by weight per 100 parts by weight of the core particle.

14. In Paragraph 13, A method for manufacturing an anode active material, wherein the step of forming the above SR coating layer is performed at 25°C to 350°C.

15. In Paragraph 14, A method for manufacturing an anode active material, wherein the mixing step is performed at 25°C to 150°C and the pressurizing step is performed at 180°C to 350°C.

16. In Paragraph 13, A method for manufacturing a positive electrode active material, wherein the metal oxide comprises ZrO2, ZrO, Li3PO4, LiF, Li2O, Al2O3, MgO, TiO2, SiO2, CeO2, Nb2O5, or a combination thereof.

17. A positive electrode comprising a positive electrode active material according to paragraph 1; cathode; and A solid-state battery comprising a solid electrolyte layer disposed between the anode and the cathode.

18. In Paragraph 17, The above positive electrode comprises a positive current collector and a positive active material layer comprising the positive active material disposed on at least one surface thereof, and An all-solid-state battery having a DC-IR (Direct Current Internal Resistance) value between the positive active material layer and the solid electrolyte layer measured by Electrochemical Impedance Spectroscopy (EIS) of 5 Ω to 50 Ω.

19. In Paragraph 17, The above-mentioned negative electrode comprises a negative current collector and a coating layer, in an all-solid-state battery.

20. In Paragraph 17, The above solid electrolyte layer comprises a sulfide-based solid electrolyte, in an all-solid-state battery.

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