Positive electrode active material for all-solid-state battery and method for producing same

Abstract

The present invention relates to positive electrode active material for an all-solid-state battery and a method for producing same. More specifically, due to a coating layer, containing boron and lithium, formed on the positive electrode active material, side reactions between the positive electrode active material and solid electrolyte can be prevented and improve the output and lifespan of the all-solid-state battery.

Description

Cathode active material for all-solid-state batteries and method for producing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0116360, filed August 29, 2024, and Korean Patent Application No. 10-2025-0119913, filed August 27, 2025, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material for an all-solid-state battery and a method for producing the same.

[0005] Various batteries are being studied to overcome the limitations of current lithium secondary batteries in terms of battery capacity, safety, output, large-scale development, and miniaturization.

[0006] In terms of capacity, continuous research is being conducted in academia and industry on metal-air batteries, which have a much larger theoretical capacity than lithium secondary batteries; all-solid-state batteries, which have no risk of explosion in terms of safety; supercapacitors, which have a higher output; NaS batteries or RFBs (redox flow batteries), which have a larger capacity; and thin film batteries, which have a smaller size.

[0007] All-solid-state batteries are batteries that replace the liquid electrolytes used in conventional lithium secondary batteries with solid electrolytes. Because they do not use flammable solvents, they are completely free of ignition or explosion caused by decomposition reactions of conventional electrolytes, significantly improving safety. Furthermore, among all-solid-state batteries, technological development is ongoing for sulfide-based all-solid-state batteries, which boast high ionic conductivity of solid electrolytes and theoretically capable of achieving high energy densities of over 900 Wh / L. Here, the term "sulfide-based all-solid-state battery" refers to an all-solid-state battery that includes a sulfide-based solid electrolyte.

[0008] In all-solid-state battery systems, lithium ion conduction is not achieved by the liquid electrolyte contained in conventional lithium secondary batteries. Therefore, when manufacturing a cathode for a sulfide-based all-solid-state battery, small-diameter sulfide-based solid electrolyte particles must be added to the cathode to increase the contact interface between the cathode active material and the sulfide-based solid electrolyte particles, thereby enhancing lithium ion conductivity.

[0009] However, due to their potential difference, a chemical reaction occurs at the interface between the positive active material and the sulfide-based solid electrolyte particles simply by physically contacting them. This chemical reaction can form a resistive material. Due to this resistive material, the initial capacity and long-life characteristics of the all-solid-state battery may be reduced during operation.

[0010] In addition, an electrochemical reaction occurs at the interface between the positive electrode active material and the sulfide-based solid electrolyte particles during charging and discharging, which may not only consume active lithium but also increase resistance.

[0011] Therefore, there is a need for the development of a technology that can improve the output characteristics and lifespan characteristics of all-solid-state batteries by preventing side reactions at the interface between the positive electrode active material and the sulfide-based solid electrolyte particles.

[0012] [Prior Art Literature]

[0013] (Patent Document 1) Korean Patent Publication No. 10-2023-0031939

[0014] The inventors of the present invention have conducted various studies to solve the above problems and have confirmed that when a coating layer containing boron (B) and lithium (Li) is formed on the surface of a positive electrode active material, side reactions with solid electrolyte particles can be prevented.

[0015] Accordingly, the purpose of the present invention is to provide a positive electrode active material for an all-solid-state battery having a coating layer containing boron and lithium formed on the surface.

[0016] Another object of the present invention is to provide a method for manufacturing a positive electrode active material for an all-solid-state battery having a coating layer containing boron and lithium formed on the surface.

[0017] Another object of the present invention is to provide a positive electrode and an all-solid-state battery including a positive electrode active material having a coating layer including boron and lithium formed on the surface.

[0018] To achieve the above purpose, the present invention provides a positive electrode active material for an all-solid-state battery, comprising: a core particle; and a coating layer positioned on the surface of the core particle;

[0019] The above coating layer provides a positive electrode active material for an all-solid-state battery, which includes boron (B) and lithium (Li).

[0020] In one embodiment of the present invention, a positive electrode active material for an all-solid-state battery is provided, wherein the boron is included in the form of at least one selected from the group consisting of boron atoms and boron compounds.

[0021] In one embodiment of the present invention, a positive electrode active material for an all-solid-state battery is provided, wherein the boron compound includes at least one selected from the group consisting of boron oxide, lithium boron oxide, and lithium borate.

[0022] In one embodiment of the present invention, a positive electrode active material for an all-solid-state battery is provided, wherein the content of boron (X) is 150 ppm ≤ X ≤ 9000 ppm.

[0023] In one embodiment of the present invention, a cathode active material for an all-solid-state battery is provided, wherein the lithium is included in at least one form selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium boron oxide, and lithium borate.

[0024] In one embodiment of the present invention, a cathode active material for an all-solid-state battery is provided, wherein the lithium is included in the form of lithium carbonate and lithium hydroxide, and the content of the lithium carbonate is less than or equal to the content of the lithium hydroxide.

[0025] In one embodiment of the present invention, a positive electrode active material for an all-solid-state battery is provided, wherein the lithium content (Y) is 3000 ppm ≤ Y ≤ 25000 ppm.

[0026] In one embodiment of the present invention, a positive electrode active material for an all-solid-state battery is provided, wherein the thickness of the coating layer is 1 nm to 50 nm.

[0027] In one embodiment of the present invention, a positive electrode active material for an all-solid-state battery is provided, wherein the core particle comprises a lithium composite metal oxide.

[0028] In one embodiment of the present invention, the true density of the positive electrode active material is 4.4 g / cm 3 A positive electrode active material for an all-solid-state battery is provided.

[0029]

[0030] The present invention also provides a method for producing a positive electrode active material for an all-solid-state battery, comprising a step of forming a coating layer containing boron and lithium on the surface of a core particle, wherein the coating layer is formed by wet coating or dry coating.

[0031] In one embodiment of the present invention, a method for producing a positive electrode active material for an all-solid-state battery is provided, wherein the wet coating is performed by the following steps (a1) to (a5):

[0032] (a1) A step of mixing a boron raw material into an alcohol-based solvent to obtain a first mixed solution for forming a coating layer;

[0033] (a2) A step of obtaining a second mixed solution for forming a positive electrode active material by mixing core particles into the first mixed solution for forming a coating layer obtained in the step (a1);

[0034] (a3) A step of filtering and pressing the second mixed solution for forming a positive electrode active material obtained in the step (a2);

[0035] (a4) a step of drying the filter press obtained in step (a3); and

[0036] (a5) A step of washing the dried product obtained in step (a4) after firing.

[0037] In one embodiment of the present invention, a method for producing a positive electrode active material for an all-solid-state battery is provided, wherein the alcohol-based solvent includes an alcohol compound having 1 to 4 carbon atoms.

[0038] In one embodiment of the present invention, a method for producing a positive electrode active material for an all-solid-state battery is provided, wherein the drying in step (a4) is performed at 80°C to 120°C.

[0039] In one embodiment of the present invention, a method for producing a positive electrode active material for an all-solid-state battery is provided, wherein the sintering in step (a5) is performed at 300°C to 750°C.

[0040] In one embodiment of the present invention, a method for producing a positive electrode active material for an all-solid-state battery is provided, wherein the dry coating is performed by the following steps (b1) to (b2):

[0041] (b1) a step of obtaining a mixture by mixing core particles and boron raw materials; and

[0042] (b2) A step of heat-treating the mixture obtained in step (b1) to form a coating layer on the surface of the core particle.

[0043]

[0044] The present invention also provides a positive electrode comprising a positive electrode active material, solid electrolyte particles, a binder, and a conductive material.

[0045] The present invention also provides an all-solid-state battery including a positive electrode.

[0046] According to the present invention, a side reaction at the interface with a solid electrolyte is prevented by a coating layer including boron and lithium formed on the surface of a positive electrode active material for an all-solid-state battery, thereby improving the output characteristics and life characteristics of the all-solid-state battery.

[0047] FIG. 1 is a schematic cross-sectional view showing the interface between a positive electrode active material and solid electrolyte particles according to one embodiment of the present invention.

[0048] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0049] The terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0050]

[0051] Cathode active material for all-solid-state batteries

[0052] The present invention relates to a positive electrode active material for an all-solid-state battery.

[0053] The positive electrode active material for an all-solid-state battery according to the present invention is an all-solid-state battery positive electrode active material comprising core particles; and a coating layer positioned on the surface of the core particles, wherein the coating layer includes boron (B) and lithium (Li).

[0054]

[0055] FIG. 1 is a schematic cross-sectional view showing the interface between a positive electrode active material and solid electrolyte particles according to one embodiment of the present invention.

[0056] Referring to Fig. 1, at the interface between the positive electrode active material (10) and the solid electrolyte particles (20), the solid electrolyte particles (20) come into contact with the coating layer (12) formed on the positive electrode active material (10). When the core particles (11) containing the active material of the positive electrode and the solid electrolyte particles (20) come into direct contact, a chemical reaction may occur due to the energy level difference. However, when the coating layer (12) containing boron and lithium and the solid electrolyte particles (20) come into direct contact, a side reaction between the core particles (11) containing the active material of the positive electrode and the solid electrolyte particles (20) is prevented, so that the output characteristics and life characteristics of the all-solid-state battery can be improved. Specifically, when the core particles (11) containing the active material of the positive electrode and the solid electrolyte particles (20) come into direct contact, interface degradation may occur due to chemical and electrochemical reactions between the active material of the positive electrode and the solid electrolyte particles (20), thereby deteriorating battery performance.

[0057]

[0058] In one embodiment of the present invention, the coating layer may include boron.

[0059] The boron may be included in the form of at least one selected from the group consisting of boron atoms and boron compounds. The boron compound may include at least one selected from the group consisting of boron oxide, lithium boron oxide, and lithium borate. Preferably, the boron may be included in the form of a boron atom.

[0060] In addition, the content (X) of boron in the coating layer may be 150 ppm ≤ X ≤ 9000 ppm. If the content (X) of boron is less than 150 ppm, the active material of the positive electrode included in the core particle may not be sufficiently protected, so that the effect of suppressing side reactions between the core particle and the solid electrolyte particle may be reduced, and if it exceeds 9000 ppm, lithium conduction may be suppressed, so that charge transfer resistance may increase. Specifically, the content (X) of the boron may be 150 ppm or more, 500 ppm or more, 1000 ppm or more, 1500 ppm or more, 2000 ppm or more, 2500 ppm or more, 3000 ppm or more, 3500 ppm or more, 4000 ppm or more, 4500 ppm or more, or 5000 ppm or more, and may be 9000 ppm or less, 8500 ppm or less, 8000 ppm or less, 7500 ppm or less, 7000 ppm or less, 6500 ppm or less, 6000 ppm or less, or 5500 ppm or less.

[0061] The content of boron (X) in the above coating layer can be controlled by adjusting the amount of boron raw material used in the manufacturing process.

[0062]

[0063] In one embodiment of the present invention, the coating layer may include lithium. The lithium may be derived from the active material of the positive electrode included in the core particle. The lithium present in the active material of the positive electrode included in the core particle may be converted into a lithium compound during the firing process of the positive electrode active material during the manufacturing process.

[0064] The lithium may be included in one or more forms selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium boron oxide, and lithium borate.

[0065] Alternatively, the lithium may be included in the form of lithium carbonate (Li2CO3) and lithium hydroxide (LiOH). The content of the lithium carbonate (Li2CO3) may be less than or equal to the content of lithium hydroxide (LiOH) (Li2CO3≤LiOH). If the content of the lithium carbonate (Li2CO3) is greater than the content of lithium hydroxide (LiOH) (Li2CO3>LiOH), the output characteristics may deteriorate. The contents of the Li2CO3 and LiOH can be adjusted by controlling the exposure of the positive electrode active material to the outside air during firing. For example, when LiOH meets CO2, it can become Li2CO3. Alternatively, the contents of the Li2CO3 and LiOH can be controlled depending on the content of the lithium source used in the core particle synthesis process. That is, as the content of the lithium source increases, the difference in the contents of the Li2CO3 and LiOH may become greater.

[0066]

[0067] In addition, the lithium content (Y) within the coating layer may be 3000 ppm ≤ Y ≤ 25000 ppm. If the lithium content (Y) is less than 3000 ppm, the overvoltage may increase during initial formation, and if it exceeds 25000 ppm, lithium conduction may slow down at the interface between the positive electrode active material and the solid electrolyte particles. Specifically, the content (Y) of the lithium may be 3000 ppm or more, 4000 ppm or more, 5000 ppm or more, 6000 ppm or more, 7000 ppm or more, 8000 ppm or more, 9000 ppm or more, 10000 ppm or more, 11000 ppm or more, 12000 ppm or more, 13000 ppm or more, 14000 ppm or more, or 15000 ppm or more, and may be 25000 ppm or less, 24000 ppm or less, 23000 ppm or less, 22000 ppm or less, 21000 ppm or less, 20000 ppm or less, 19000 ppm or less, 18000 ppm or less, 17000 ppm or less, or 16000 ppm or less.

[0068]

[0069] In one embodiment of the present invention, the thickness of the coating layer may be 1 nm to 50 nm. If the thickness of the coating layer is less than 1 nm, the effect of preventing side reactions between the core particles included in the positive electrode active material and the solid electrolyte particles may be reduced, and if it is more than 50 nm, the thickness of the coating layer may be excessively thick and act as a resistor. Specifically, the thickness of the coating layer may be 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 25 nm or more, and may be 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less.

[0070]

[0071] In one embodiment of the present invention, the coating layer may be included in an amount of 0.1 to 3 wt% based on the total weight of the positive electrode active material. If the content of the coating layer is less than 0.1 wt%, a side reaction between the positive electrode active material and the solid electrolyte may occur, and if it exceeds 3 wt%, the content of the coating layer may be too large and act as a resistor. Specifically, the content of the coating layer may be 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, or 0.5 wt% or more, and may be 3 wt% or less, 2.5 wt% or less, 2 wt% or less, 1.5 wt% or less, or 1 wt% or less.

[0072]

[0073] In one embodiment of the present invention, the core particle includes a lithium composite metal oxide capable of reversible intercalation and deintercalation of lithium as an active material of the positive electrode.

[0074] The above lithium composite metal oxide may include lithium, nickel, cobalt, and a metal element M (wherein M is at least one selected from the group consisting of Mn and Al).

[0075] In addition, in the lithium composite metal oxide, at least one of the metal elements other than lithium may be doped with one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. When the lithium composite metal oxide is additionally doped with the above-described element, the structural stability of the positive electrode active material is improved, and as a result, the output characteristics of the battery can be improved. At this time, the content of the doping element included in the lithium composite metal oxide can be appropriately controlled within a range that does not deteriorate the characteristics of the positive electrode active material, and specifically, it can be 0.05 atomic% or less based on the entire lithium composite metal oxide.

[0076] Specifically, the lithium composite metal oxide may be represented by the following chemical formula 1:

[0077] <Chemical Formula 1>

[0078] Li α Ni x Co y M z M' w O2

[0079] In the above chemical formula 1

[0080] M is at least one selected from the group consisting of Mn and Al,

[0081] M' contains one or more doping elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo,

[0082] α, x, y, z and w are the atomic fractions of independent elements, respectively, 0.95≤α≤1.05, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1, 0≤w≤0.05일 수 있으며, 보다 구체적으로는 0.95≤α≤1.05, 0.6≤x<1, 0<y≤0.4, 0<z≤0.4, x+y+z=1, 0≤w≤0.05이다. 이때 상기 α는 미충전시 값이며, 상기 화학식 1의 조성은 평균값이다.

[0083] More specifically, the core particle is LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 W 0.02 O2 or LiNi 0.85 Co 0.09 Mn 0.045 Al 0.015 It may be a lithium composite metal oxide containing a high nickel content, such as O2, and at least one or more of these may be used.

[0084] In addition, the core particles may have an average particle diameter (D50) of 1 to 50 ㎛, and specifically, the average particle diameter (D50) may be 1 ㎛ or more, 3 ㎛ or more, 5 ㎛ or more, 8 ㎛ or more, or 10 ㎛ or more, and 50 ㎛ or less, 45 ㎛ or less, 40 ㎛ or less, 35 ㎛ or less, or 30 ㎛ or less.

[0085] The average particle diameter (D50) of the above core particles can be defined as the particle diameter at 50% of the particle diameter distribution. The average particle diameter (D50) of the above core particles can be measured, for example, using a laser diffraction method. More specifically, after dispersing the core particles in a dispersion medium, the particles are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of 28 kHz at an output of 60 W, and the average particle diameter (D50) at 50% of the particle diameter distribution in the measuring device can be calculated.

[0086]

[0087] In one embodiment of the present invention, the core particles may be included in an amount of 97 to 99.9 wt% based on the total weight of the positive electrode active material. If the content of the core particles is less than 97 wt%, battery performance may deteriorate, and if it exceeds 99.9 wt%, the content of the coating layer may relatively decrease, causing a side reaction with the solid electrolyte. Specifically, the content of the core particles may be 97 wt% or more, 97.5 wt% or more, 98 wt% or more, 98.5 wt% or more, or 99 wt% or less, 99.9 wt% or less, 99.8 wt% or less, 99.7 wt% or less, 99.6 wt% or less, or 99.5 wt% or less.

[0088]

[0089] In one embodiment of the present invention, the true density of the positive electrode active material is 4.4 g / cm 3 It may be an ideal. The true density of the positive electrode active material refers to the mass relative to the actual volume occupied by the positive electrode active material.

[0090] The true density of the above positive electrode active material is 4.4 g / cm 3If it is less than 4.4 g / cm, it means that there are closed pores in the positive electrode active material, and the life characteristics of the all-solid-state battery may deteriorate. Specifically, the true density of the positive electrode active material is 4.4 g / cm. 3 Above, 4.5 g / cm 3 Above, 4.6 g / cm 3 Above, 4.7 g / cm 3 Above, 4.8 g / cm 3 Above, 4.9 g / cm 3 Above, 5.0 g / cm 3 Above, 5.1 g / cm 3 Above, 5.2 g / cm 3 Above, 5.3 g / cm 3 Above, 5.4 g / cm 3 Above, 5.5 g / cm 3 Above, 5.6 g / cm 3 Above, 5.7 g / cm 3 Above, 5.8 g / cm 3 Above, 5.9 g / cm 3 or more than 6.0 g / cm 3 It may be ideal. The upper limit of the true density of the above positive electrode active material is not particularly limited, but is 10 g / cm 3 Below 9 g / cm 3 Below 8 g / cm 3 Less than or equal to 7 g / cm 3 It can be as follows. The above true density can be controlled by adjusting the firing temperature during the manufacturing process, and the higher the firing temperature, the higher the true density can be.

[0091] Additionally, the true density of the positive electrode active material can be measured by a true density measuring device (Gas pycnometer).

[0092]

[0093] Method for manufacturing positive electrode active material for all-solid-state batteries

[0094] The present invention also relates to a method for producing a positive electrode active material for an all-solid-state battery.

[0095] The method for manufacturing a positive electrode active material for an all-solid-state battery according to the present invention may include a step of forming a coating layer containing boron and lithium on the surface of a core particle. The coating layer may be formed by wet coating using a solvent or dry coating without using a solvent.

[0096]

[0097] In one embodiment of the present invention, the positive electrode active material for the all-solid-state battery can be manufactured by forming a coating layer by wet coating.

[0098] The method for manufacturing a positive electrode active material for an all-solid-state battery forming a coating layer by the above wet coating may include the following steps (a1) to (a5):

[0099] (a1) A step of mixing a boron raw material into an alcohol-based solvent to obtain a first mixed solution for forming a coating layer;

[0100] (a2) A step of obtaining a second mixed solution for forming a positive electrode active material by mixing core particles into the first mixed solution for forming a coating layer obtained in the step (a1);

[0101] (a3) A step of filtering and pressing the second mixed solution for forming a positive electrode active material obtained in the step (a2);

[0102] (a4) a step of drying the filter press obtained in step (a3); and

[0103] (a5) A step of firing the dried product obtained in step (a4) above.

[0104]

[0105] Hereinafter, a method for manufacturing a positive electrode active material for an all-solid-state battery using wet coating according to the present invention will be described in more detail step by step.

[0106]

[0107] In one embodiment of the present invention, in the step (a1), a boron raw material may be mixed with an alcohol-based solvent to obtain a first mixed solution for forming a coating layer.

[0108] The above boron raw material may refer to a material that can exist as a boron atom within a coating layer after the coating layer is formed, as a source material of boron, or may refer to a material that can exist in the form of a boron compound by reacting with lithium contained within the core particle.

[0109] The above boron raw material may include at least one selected from the group consisting of oxides, hydroxides, chlorides, fluorides, carbides, and alkoxides of boron. For example, the above boron raw material may include B2O3, H3BO3, and C 13 H 19 It may include one or more selected from the group consisting of B03.

[0110]

[0111] The alcohol-based solvent may include at least one alcohol compound having 1 to 4 carbon atoms. Specifically, the alcohol-based solvent may include at least one selected from the group consisting of acetone, methanol, ethanol, isopropyl alcohol, butyl alcohol, octyl alcohol, and allyl alcohol. Considering the processability in the positive electrode active material manufacturing process and the formability of a coating layer in the final positive electrode active material manufactured, the alcohol-based solvent may be ethanol.

[0112]

[0113] In one embodiment of the present invention, in step (a2), a second mixed solution for forming a positive electrode active material may be obtained by mixing core particles into the first mixed solution for forming a coating layer obtained in step (a1). The core particles are not particularly limited as long as they can be used as an active material for a positive electrode for an all-solid-state battery. For example, the core particles may include a lithium composite metal oxide.

[0114] The type and content of the core particles are as described above.

[0115]

[0116] In one embodiment of the present invention, in the step (a3), the second mixed solution for forming a positive electrode active material obtained in the step (a2) can be filtered and pressed.

[0117] The above filtration pressing can remove the alcohol-based solvent by pressurizing at 0.3 to 1 MPa. For example, the pressurization can be performed by air blowing, and the alcohol-based solvent can be removed by pressurizing by air blowing for 5 to 15 minutes. In addition, the filtration pressing can remove the alcohol-based solvent from the mixture containing the coating raw material and the positive electrode active material using a pressurized filtration device. The pressurized filtration device is generally used in the relevant technical field, and is not particularly limited as long as it can effectively remove the alcohol-based solvent.

[0118] By the above filtration pressing, the alcohol-based solvent can be removed from the second mixed solution in a short period of time, thereby minimizing the time that the core particles are exposed to the liquid.

[0119] The filter press obtained after the above filtration and pressing is in a form in which the boron raw material is adsorbed between core particles, and the filter press may contain a trace amount of an alcohol-based solvent. The filter press can be said to have a form of a positive electrode active material in which a coating layer is formed on the surface of the core particles.

[0120]

[0121] Additionally, the removed alcohol-based solvent can be recycled by recovering it and adding it to the second mixed solution for forming the positive electrode active material. Since the alcohol-based solvent removed with the second mixed solution also contains residues of the boron raw material and / or core particles, the yield can be improved during recycling.

[0122] Additionally, the process of recovering the removed alcohol-based solvent into the second mixed solution for forming the positive electrode active material may be performed two or more times, and the uniformity of the coating layer may be improved as the number of times increases. The upper limit of the number of times is not particularly limited, but considering the processability, it may be performed 5 times or less, 4 times or less, or 3 times or less.

[0123]

[0124] In one embodiment of the present invention, in step (a4), the filter press obtained in step (a3) ​​can be dried.

[0125] The alcohol solvent can be completely removed by the above drying.

[0126] The drying temperature is not particularly limited as long as it is a temperature capable of removing the alcohol-based solvent. For example, the drying may be performed at 80°C to 120°C. If the drying temperature is lower than 80°C, the alcohol-based solvent may not be completely removed, and if it exceeds 120°C, the raw material properties may be denatured, resulting in a deterioration in the performance of the manufactured positive electrode active material. Specifically, the drying temperature may be 80°C or higher, 85°C or higher, or 90°C or higher, and may be 120°C or lower, 115°C or lower, or 110°C or lower.

[0127] The dried product obtained after the above drying may be in a state in which boron raw material is adsorbed on the surface of the core particles.

[0128]

[0129] In one embodiment of the present invention, in the step (a5), the dried product obtained in the step (a4) may be washed after firing.

[0130] During firing, the boron raw material may be fired at a temperature higher than the melting point of the boron raw material to melt the boron raw material, and then a coating layer may be formed by a reaction between lithium present in the core particle and boron contained in the boron raw material.

[0131] The above-mentioned sintering temperature can be controlled depending on the type of the boron raw material, and is, for example, 300°C to 750°C. If the above-mentioned sintering temperature is lower than 300°C, the boron raw material may not melt and may remain in a solid state, so that the coating layer may be formed unevenly, and if it is higher than 750°C, lithium within the structure may be desorbed due to the high sintering temperature, and there may be a problem of deterioration in structural stability. Specifically, the above-mentioned sintering temperature may be 300°C or higher, 350°C or higher, or 400°C or higher, and may be 750°C or lower, 700°C or lower, 650°C or lower, or 600°C or lower.

[0132] Additionally, by controlling the degree of removal of lithium compounds through the above-described cleaning process, the content of lithium contained in the final coating layer can be adjusted. For example, if the above-described cleaning process continues for a long period of time, the content of LiOH can increase, and if the cleaning process continues for a relatively short period of time, the content of LiOH can decrease.

[0133] Additionally, within the above-mentioned firing temperature range, the higher the temperature, the higher the density of the positive electrode active material.

[0134]

[0135] In one embodiment of the present invention, the positive electrode active material for the all-solid-state battery can be manufactured by forming a coating layer by dry coating.

[0136] Hereinafter, a method for manufacturing a positive electrode active material for an all-solid-state battery using dry coating according to the present invention will be described in more detail step by step.

[0137]

[0138] The method for manufacturing a positive electrode active material for an all-solid-state battery by forming a coating layer by the above dry coating may include the following steps (b1) to (b2):

[0139] (b1) a step of obtaining a mixture by mixing core particles and boron raw materials; and

[0140] (b2) A step of heat-treating the mixture obtained in step (b1) to form a coating layer on the surface of the core particle.

[0141]

[0142] Hereinafter, a method for manufacturing a positive electrode active material for an all-solid-state battery using dry coating according to the present invention will be described in more detail step by step.

[0143]

[0144] In one embodiment of the present invention, in step (b1), a mixture may be obtained by mixing core particles and a boron raw material. The types and characteristics of the core particles and boron raw material are as described above.

[0145]

[0146] In one embodiment of the present invention, in step (b2), the mixture obtained in step (b1) may be heat-treated to form a coating layer on the surface of the core particle.

[0147] The heat treatment temperature may be 200°C to 400°C. If the heat treatment temperature is less than 200°C, the coating layer shape may not be formed, and if it exceeds 400°C, the coating layer may be denatured, thereby reducing the functionality of preventing side reactions between the core particles and the solid electrolyte. Specifically, the heat treatment temperature may be 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, 250°C or higher, 260°C or higher, 270°C or higher, 280°C or higher, or 290°C or higher, and may be 400°C or lower, 390°C or lower, 380°C or lower, 370°C or lower, 360°C or lower, 350°C or lower, 340°C or lower, 330°C or lower, 320°C or lower, or 310°C or lower.

[0148]

[0149] Cathode for all-solid-state batteries

[0150] The present invention also relates to a positive electrode for an all-solid-state battery.

[0151] The positive electrode for an all-solid-state battery according to the present invention comprises a positive electrode current collector; and a positive electrode active material layer formed on one surface of the positive electrode current collector. The positive electrode active material layer comprises the positive electrode active material, a solid electrolyte, a binder, and a conductive material as described above. The solid electrolyte may be a sulfide-based solid electrolyte.

[0152]

[0153] The positive electrode active material according to one embodiment of the present invention is as described above.

[0154] In addition, the positive electrode active material may be included in an amount of 50 to 90 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 50 wt%, 55 wt% or more, or 60 wt% or more, and may be 90 wt% or less, 85 wt% or less, 80 wt% or less, 75 wt% or less, or 70 wt% or less. If the content of the positive electrode active material is less than 50 wt%, battery performance may deteriorate, and if it exceeds 90 wt%, mass transfer resistance may increase.

[0155]

[0156] In one embodiment of the present invention, the sulfide-based solid electrolyte is a solid electrolyte containing sulfur among solid electrolytes and can improve ionic conductivity.

[0157] The above sulfide-based solid electrolyte may include at least one selected from the group consisting of LiPSX (X = Cl, Br or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited to these, and a wide range of sulfide-based solid electrolytes commonly used in the art can be used.

[0158] In addition, the particle size (D50) of the sulfide-based solid electrolyte may be in the form of particles having a size of 0.1 ㎛ to 1.5 ㎛. Specifically, the particle size (D50) of the sulfide-based solid electrolyte may be 0.1 ㎛ or more, 0.3 ㎛ or more, or 0.5 ㎛ or more, and may be 1.5 ㎛ or less, 1.2 ㎛ or less, 1.0 ㎛ or less, or 0.9 ㎛ or less. If the particle size (D50) of the sulfide-based solid electrolyte is less than 0.1 ㎛, the ultrafine sulfide-based solid electrolyte particles may not be sufficiently dispersed within the positive electrode active material layer and may aggregate, and if it exceeds 1.5 ㎛, dispersion may be somewhat easy, but the contact surface with the positive electrode active material particles may decrease and the positive electrode porosity may increase.

[0159] In addition, the sulfide-based solid electrolyte may be included in an amount of 5 to 30 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the sulfide-based solid electrolyte may be 5 wt% or more, 8 wt% or more, 10 wt% or more, 13 wt% or more, 15 wt% or more, or 18 wt% or more, and may be 30 wt% or less, 28 wt% or less, 25 wt% or less, or 22 wt% or less. If the content of the sulfide-based solid electrolyte is less than 5 wt%, ionic conductivity may be reduced, and if it exceeds 30 wt%, the content of the positive electrode active material and the conductive agent may be relatively reduced, resulting in reduced battery performance.

[0160]

[0161] In one embodiment of the present invention, the binder may be included to assist bonding between materials included in the positive electrode active material layer and bonding between the positive electrode active material layer and the positive electrode current collector.

[0162] The above binder is polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, It may include at least one selected from the group consisting of polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0163] In addition, the binder may be included in an amount of 0.1 to 3 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the binder may be 0.1 wt% or more, 0.5 wt% or more, or 0.8 wt% or more, and may be 3 wt% or less, 2 wt% or less, or 1.5 wt% or less. If the content of the binder is less than 0.1 wt%, the effect of improving the bonding strength between materials included in the positive electrode active material layer is insignificant, so the positive electrode active material layer may not be properly formed, and if it exceeds 3 wt%, ionic conductivity or electrical conductivity may be reduced.

[0164]

[0165] In one embodiment of the present invention, the conductive material can form a path that can conduct electrons, thereby improving electronic conductivity.

[0166] The above conductive material may be a linear conductive material, and the linear conductive material may be at least one selected from the group consisting of carbon nanotubes (CNTs) and carbon nanofibers (CNFs). The linear conductive material may improve electrical conductivity due to its morphological characteristics. For example, the aspect ratio (length / diameter) of the linear conductive material may be 2 or more, and specifically, the aspect ratio may be 2 or more, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, 50 or more, or 100 or more. If the aspect ratio is less than 2, it may be difficult to form an electron conduction path, and thus the electron conductivity may be reduced. In addition, the upper limit of the aspect ratio is not particularly limited, but may be 700 or less, 600 or less, 500 or less, 400 or less, or 300 or less in consideration of the ease of forming an electron conduction path.

[0167] In addition, the conductive material may be included in an amount of 1 to 10 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 1 wt% or more, 2 wt% or more, or 3 wt% or more, and may be 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, or 6 wt% or less. If the content of the conductive material is less than 1 wt%, the electrical conductivity of the positive electrode may be reduced, and if it exceeds 10 wt%, the content of the positive electrode active material and the sulfide-based solid electrolyte may be relatively reduced, resulting in deterioration of battery performance.

[0168]

[0169] In one embodiment of the present invention, the thickness of the positive electrode active material layer may be 100 ㎛ to 300 ㎛, specifically, may be 100 ㎛ or more, 110 ㎛ or more, or 120 ㎛ or more, and may be 300 ㎛ or less, 250 ㎛ or less, or 200 ㎛ or less. However, the thickness of the positive electrode active material layer is not limited thereto, and the thickness may be adjusted to have a positive electrode loading such that the ratio of ionic conductivity to electronic conductivity becomes 0.8 to 1.2 depending on the composition of the positive electrode active material layer.

[0170]

[0171] In one embodiment of the present invention, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external conductor and the positive electrode active material layer.

[0172] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the all-solid-state battery. For example, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, stainless steel surface-treated with carbon, nickel, silver, etc., aluminum-cadmium alloy, etc. can be used as the positive electrode current collector.

[0173] The positive electrode current collector may have a finely irregular structure on its surface or may employ a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer. Accordingly, the positive electrode current collector may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or non-woven fabric.

[0174]

[0175] All-solid-state batteries

[0176] The present invention also relates to an all-solid-state battery including the positive electrode.

[0177] The all-solid-state battery according to the present invention comprises the positive electrode, the negative electrode, and a sulfide-based solid electrolyte membrane interposed therebetween. The positive electrode is as described above.

[0178]

[0179] In one embodiment of the present invention, the negative electrode includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector. The negative electrode active material layer may include a negative electrode active material and a conductive material.

[0180] The above negative active material is lithium (Li + ) can be reversibly intercalated or deintercalated, a material that can react with lithium ions to form a reversibly lithium-containing compound, or a lithium metal or a lithium alloy.

[0181] The above lithium ion (Li + ) can be reversibly inserted or de-inserted, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The lithium ion (Li + ) can be, for example, tin oxide, titanium nitrate or silicon. The lithium alloy can be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al) and tin (Sn).

[0182] Preferably, the negative electrode active material may be lithium metal or a lithium-indium alloy (Li-In), and specifically, may be in the form of a lithium metal or lithium and a thin film or a lithium-indium alloy thin film or powder.

[0183] The negative electrode active material may be included in an amount of 40 to 80 wt% based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt% or more or 50 wt% or more, and 80 wt% or less or 70 wt% or less. If the content of the negative electrode active material is less than 40 wt%, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80 wt%, the mass transfer resistance may increase.

[0184]

[0185] In addition, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples thereof include graphite or conductive carbon, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; metal powder such as aluminum powder and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in combination of two or more thereof, but are not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0186] The conductive material may typically be included in an amount of 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer, and specifically, the content of the conductive material may be 1 wt% or more, 1.5 wt% or more, or 2 wt% or more, and 5 wt% or less, 4.5 wt% or less, or 4 wt% or less. If the content of the conductive material is too low, such as less than 1 wt%, it may be difficult to expect an effect of improving electrical conductivity or the electrochemical characteristics of the battery may deteriorate, and if it exceeds 5 wt%, too much, the amount of the negative electrode active material may be relatively small, which may lower the capacity and energy density. The method of including the conductive material in the negative electrode is not particularly limited, and conventional methods known in the art, such as mixing with the negative electrode active material or coating, may be used.

[0187] In addition, the negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. In addition, the negative electrode current collector, like the positive electrode current collector, may be made of various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. having fine irregularities formed on the surface.

[0188] The method for manufacturing the above negative electrode is not particularly limited, and can be manufactured by forming a negative electrode active material layer on the negative electrode current collector using a method for forming a layer or film commonly used in the art. For example, methods such as compression, coating, and deposition can be used. In addition, a case in which a battery is assembled on the negative electrode current collector without a lithium thin film and then a metallic lithium thin film is formed on the metal plate through initial charging is also included in the negative electrode of the present invention.

[0189]

[0190] In one embodiment of the present invention, the sulfide-based solid electrolyte included in the sulfide-based solid electrolyte membrane may include at least one selected from the group consisting of LiPSX (X = Cl, Br or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited to these, and a sulfide-based solid electrolyte commonly used in the art can be widely used.

[0191]

[0192] battery module

[0193] The present invention also relates to a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source.

[0194] Hereinafter, specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system. Hereinafter, preferred embodiments are presented to help understand the present invention, but the following embodiments are only illustrative of the present invention and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it will be apparent that such changes and modifications also fall within the scope of the appended patent claims.

[0195]

[0196] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0197]

[0198] Example 1

[0199] A first mixed solution for forming a coating layer was obtained by mixing B2O3 as a boron raw material with ethanol, an alcoholic solvent. At this time, the boron raw material was used so that the boron content in the final coating layer was 750 ppm.

[0200] A second mixed solution for forming a positive electrode active material was obtained by mixing a lithium composite metal oxide (NMC811) as a core particle into the first mixed solution. In addition, the solid content of the second mixed solution was set to 50 wt%, and the solid content here refers to the weight of the boron raw material and the lithium composite metal oxide excluding the alcohol-based solvent. At this time, the lithium composite metal oxide was used so that the lithium content in the final coating layer was 6200 ppm.

[0201] By filtering and pressing the second mixed solution to remove the alcohol-based solvent, a powder for forming a positive electrode active material was obtained. At this time, a filter press was used.

[0202] The powder for forming the above positive electrode active material was dried in a vacuum oven at 100°C for 12 hours.

[0203] Thereafter, the dried positive electrode active material forming powder was calcined at 400°C for 9 hours to produce a positive electrode active material having a coating layer formed on the surface of the core particles. Thereafter, the positive electrode active material was washed.

[0204]

[0205] Example 2

[0206] A positive electrode active material was manufactured in the same manner as in Example 1, except that the amount of the boron raw material used was adjusted so that the boron content in the final manufactured coating layer was 1600 ppm, and the lithium composite metal oxide was used so that the lithium content in the final manufactured coating layer was 9100 ppm.

[0207]

[0208] Example 3

[0209] A positive electrode active material was manufactured in the same manner as in Example 1, except that the amount of the boron raw material was adjusted so that the boron content in the final manufactured coating layer was 2300 ppm, and the lithium composite metal oxide was used so that the lithium content in the final manufactured coating layer was 10000 ppm.

[0210]

[0211] Example 4

[0212] The lithium composite metal oxide was used so that the lithium content in the final coating layer was 6354 ppm, and the positive electrode active material was manufactured in the same manner as in Example 1, except that the washing was performed for a relatively short time.

[0213]

[0214] Example 5

[0215] The lithium composite metal oxide was used so that the lithium content in the final coating layer was 6000 ppm, and a cathode active material was manufactured in the same manner as in Example 1, except that the sintering temperature was relatively low.

[0216]

[0217] Example 6

[0218] The lithium composite metal oxide was used so that the lithium content in the final coating layer was 6000 ppm, and a positive electrode active material was manufactured in the same manner as in Example 1, except that the washing was performed for a relatively short time.

[0219]

[0220] Comparative Example 1

[0221] A positive electrode active material was manufactured in the same manner as in Example 1, except that the boron raw material was not used and the lithium composite metal oxide was used so that the lithium content in the final manufactured coating layer was 11,400 ppm.

[0222]

[0223] Experimental Example 1: Analysis of the components of the coating layer

[0224] As a result of examining the positive electrode active material manufactured in the example using SEM EDS (JEOL, JSM-IT800), it was confirmed that B, Li2CO3, and LiOH were present in the coating layer. Accordingly, the contents of boron and lithium contained in the coating layer formed on the positive electrode active material were measured using the following method.

[0225] The boron content in the coating layer formed on the above positive electrode active material was measured using inductively coupled plasma mass spectrometry (ICP-MS) (manufacturer: PerkinElmer).

[0226] Additionally, the content of lithium contained in the coating layer formed on the positive electrode active material was measured using a potentiometric titrator (Metrohm, OMNIS titrator).

[0227]

[0228] In addition, the true density of the positive electrode active material was measured using a true density measuring device (BELPycno, Microtrac).

[0229]

[0230] Table 1 below shows the results of component analysis included in the coating layer of the positive electrode active material manufactured in the example.

[0231]

[0232] Lithium content B (ppm) Cathode density (g / cm) 3 )Li2CO3(ppm)LiOH(ppm)TTL(Total Li, ppm)Example 11200500062007504.62Example 232005900910016004.61Example 3300070001000023004.62Example 4579256263547504.58Example 51200480060007504.32Example 660005000110007504.62Comparative Example 1470067001140004.61

[0233]

[0234] As shown in Table 1 above, after the coating layer is formed, it can be seen that lithium exists in the form of lithium compounds such as Li2CO3, LiOH, etc. inside the coating layer. In addition, TTL (Total Li) is the total lithium content within the coating layer, and it can be confirmed that the TTL content varies depending on the cleaning time after the coating layer of the positive electrode active material is formed.

[0235]

[0236] Experimental Example 2: Performance Evaluation

[0237] To evaluate the performance of an all-solid-state battery using a cathode active material, charge-discharge experiments were conducted in a pressed cell. A pressed cell is composed of a cathode, an electrolyte, and an anode laminated within a mold. The cell was manufactured by mixing the cathode active material, Super-P (manufactured by Imerys) as a conductive material, and a sulfide-based electrolyte of Li2S-P2S5 in a weight ratio of 70:25:5 to manufacture a cathode composite. Li-In was used as the counter electrode (cathode). The all-solid-state battery cell was manufactured as follows. The solid electrolyte was placed in the mold and pressed to form a solid electrolyte layer. Next, the cathode active material composite was applied to one side of the solid electrolyte layer, and the anode was laminated on the other side, followed by additional pressing to manufacture an electrode assembly. The manufactured electrode assembly was placed inside a battery case to manufacture an all-solid-state battery. The manufactured all-solid-state battery was charged and discharged at 0.1C for two cycles in a charger / discharger, and the discharge capacity, Coulombic efficiency, and 0.1C / 0.1C (%) were measured, and the initial efficiency (initial discharge / initial charge X 100) was calculated through this. In addition, the cycle performance (cycle retention at 200 cycles) was calculated by charging and discharging at 0.2C. Measurements and calculations were performed using a measuring device (Toscat-3100, Shin Corporation).

[0238]

[0239] Table 2 below describes the results of the above experiment.

[0240]

[0241] Discharge capacity (mAh / g) CE (mAh / g, Coulombic efficiency) 0.1C / 0.1C (%) Cycle retention (%) @ 200 cycles Example 1 21694.29393 Example 2 21494.39495 Example 3 21194.69495 Example 4 21492.99188 Example 5 21494.08790 Example 6 21291.28890 Comparative example 121391.18885

[0242]

[0243] Referring to Table 2 above, it can be seen that Examples 1 to 3 contain boron and lithium in appropriate amounts in the coating layer of the positive electrode active material, and the content of Li2CO3 among the lithium compounds is smaller than the content of LiOH, so that the discharge capacity, coulombic efficiency, and lifespan characteristics are all excellent.

[0244] On the other hand, Examples 4 and 6 contained boron and lithium in appropriate amounts in the coating layer of the positive electrode active material, but the content of Li2CO3 among the lithium compounds was greater than the content of LiOH, resulting in a decrease in the life characteristics.

[0245] In addition, Example 5 showed that the life characteristics were also reduced due to the small density of the cathode material.

[0246] Additionally, Comparative Example 1 was found to have poor overall performance because the coating layer did not contain boron.

[0247]

[0248] [Explanation of symbols]

[0249] 10: Cathode active material

[0250] 11: Core particle

[0251] 12: Coating layer

[0252] 20: Solid electrolyte particles

Claims

1. A positive electrode active material for an all-solid-state battery comprising a core particle and a coating layer positioned on the surface of the core particle, The above coating layer is a positive electrode active material for an all-solid-state battery, which contains boron (B) and lithium (Li).

2. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the boron is included in at least one form selected from the group consisting of boron atoms and boron compounds.

3. In paragraph 2, A positive electrode active material for an all-solid-state battery, wherein the boron compound comprises at least one selected from the group consisting of boron oxide, lithium boron oxide, and lithium borate.

4. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the content of boron (X) is 150 ppm ≤ X ≤ 9000 ppm.

5. In paragraph 1, A cathode active material for an all-solid-state battery, wherein the lithium is included in at least one form selected from the group consisting of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium boron oxide, and lithium borate.

6. In paragraph 1, The above lithium is included in the form of lithium carbonate and lithium hydroxide, A positive electrode active material for an all-solid-state battery, wherein the content of the lithium carbonate is less than or equal to the content of lithium hydroxide.

7. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the lithium content (Y) is 3000 ppm ≤ Y ≤ 25000 ppm.

8. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the thickness of the coating layer is 1 nm to 50 nm.

9. In paragraph 1, A positive electrode active material for an all-solid-state battery, wherein the core particles include a lithium composite metal oxide.

10. In paragraph 1, The true density of the above positive electrode active material is 4.4 g / cm 3 A positive electrode active material for an all-solid-state battery.

11. A step of forming a coating layer containing boron and lithium on the surface of the core particle, A method for manufacturing a positive electrode active material for an all-solid-state battery, wherein the above coating layer is formed by wet coating or dry coating.

12. In paragraph 11, A method for manufacturing a positive electrode active material for an all-solid-state battery, wherein the above wet coating is performed by the following steps (a1) to (a5): (a1) A step of mixing a boron raw material into an alcohol-based solvent to obtain a first mixed solution for forming a coating layer; (a2) A step of obtaining a second mixed solution for forming a positive electrode active material by mixing core particles into the first mixed solution for forming a coating layer obtained in the step (a1); (a3) A step of filtering and pressing the second mixed solution for forming a positive electrode active material obtained in the step (a2); (a4) a step of drying the filter press obtained in step (a3); and (a5) A method for producing a positive electrode active material for an all-solid-state battery, comprising a step of washing the dried product obtained in step (a4) after calcining it.

13. In paragraph 12, A method for producing a positive electrode active material for an all-solid-state battery, wherein the alcohol-based solvent comprises an alcohol compound having 1 to 4 carbon atoms.

14. In paragraph 12, A method for producing a positive electrode active material for an all-solid-state battery, wherein the drying in step (a4) is performed at 80°C to 120°C.

15. In paragraph 12, A method for producing a positive electrode active material for an all-solid-state battery, wherein the sintering in step (a5) is performed at 300°C to 750°C.

16. In paragraph 11, A method for manufacturing a positive electrode active material for an all-solid-state battery, wherein the above dry coating is performed by the following steps (b1) to (b2): (b1) a step of obtaining a mixture by mixing core particles and boron raw materials; and (b2) A method for producing a positive electrode active material for an all-solid-state battery, comprising a step of heat-treating the mixture obtained in step (b1) to form a coating layer on the surface of the core particle.

17. A positive electrode for an all-solid-state battery comprising a positive electrode active material, solid electrolyte particles, a binder, and a conductive material according to any one of claims 1 to 10.

18. An all-solid-state battery comprising the positive electrode of clause 17.

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