Cathode active material and method for manufacturing the same

Abstract

The cathode active material includes a lithium composite metal oxide and a solid electrolyte layer coating the lithium composite metal oxide, the solid electrolyte layer including an oxygen-doped sulfide-based solid electrolyte.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0172700, filed with the Korean Intellectual Property Office on November 27, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a cathode active material and a method for manufacturing the same, and more specifically, to a cathode active material for use in all-solid-state batteries. Background Technology

[0004] Lithium-ion batteries have been developed as small power sources for smartphones and small electronic devices, and the demand for lithium-ion batteries is increasing with the development of electric vehicles.

[0005] Lithium-ion batteries consist of cathode and anode materials for exchanging lithium ions, and an electrolyte for transporting lithium ions. Conventional lithium-ion batteries use a liquid electrolyte obtained by dissolving lithium salts in an organic solvent, and a separator containing organic fibers to prevent physical contact between the positive and negative electrodes, thus preventing short circuits. Because flammable organic solvents are used as the electrolyte solvent, the likelihood of fire or explosion increases when a short circuit occurs due to physical damage; such accidents have occurred frequently.

[0006] All-solid-state batteries use inorganic solid electrolytes to replace flammable liquid electrolytes. Inorganic solid electrolytes mainly include oxide electrolytes and sulfide electrolytes. Among them, sulfide solid electrolytes have attracted much attention due to their high lithium-ion conductivity, which is close to that of liquid electrolytes.

[0007] However, sulfide-based solid electrolytes can trigger side reactions at the interface between the cathode material and the electrolyte, thereby reducing battery performance. Therefore, to prevent these side reactions, a stable solid electrolyte material is needed on the surface of the cathode material, ensuring lithium-ion mobility at the cathode-solid electrolyte interface. Furthermore, surface coating technology for the cathode active material should be employed to ensure a higher contact rate between the cathode active material and the solid electrolyte.

[0008] [Primary Technology]

[0009] [Patent Literature]

[0010] (Patent Document 1) US Patent Application No. US2023 / 0187620 A Summary of the Invention

[0011] The present invention aims to solve the above-mentioned problems existing in the prior art, while retaining the advantages achieved by the prior art.

[0012] One aspect of the present invention provides a cathode active material comprising a solid electrolyte layer and a method for manufacturing the same. The cathode active material helps to suppress side reactions occurring at the interface between the cathode material and the solid electrolyte, reduces the internal resistance of the electrode, and improves the high-temperature stability and performance of the cathode material.

[0013] The technical problems to be solved by the present invention are not limited to those described above. Those skilled in the art will clearly understand from the following description any other technical problems not mentioned herein.

[0014] (1) The present invention provides a cathode active material comprising: a core comprising a lithium composite metal oxide; and a solid electrolyte layer disposed on the core. The solid electrolyte layer comprises an oxygen-doped sulfide-based solid electrolyte.

[0015] (2) The present invention provides a cathode active material, wherein the weight of the solid electrolyte layer is about 0.01 wt% to about 6 wt% of the total weight of the lithium composite metal oxide in (1).

[0016] (3) The present invention provides a cathode active material, wherein in (1) or (2), when the solid electrolyte layer is analyzed by X-ray photoelectron spectroscopy (XPS), the solid electrolyte layer has an observable peak in the range of 532.5 eV to 533 eV.

[0017] (4) The present invention provides a cathode active material, wherein in any one of (1) to (3), the oxygen-doped sulfide solid electrolyte comprises thiophosphate (PS3O4). 3- ).

[0018] (5) The present invention provides a cathode active material, wherein in any one of (1) to (4), the sulfide solid electrolyte is represented by the following chemical formula 2.

[0019] [Chemical Formula 2]

[0020] Li 7-a PS 6-a X a ,

[0021] In chemical formula 2, 0 ≤ a ≤ 2, and X is any one of Cl, Br, or I.

[0022] (6) The present invention provides a cathode active material, wherein in any of (1) to (5), the core is obtained by coating LiNbO3 onto a lithium composite metal oxide.

[0023] (7) The present invention provides a cathode active material, wherein in any one of (1) to (6), the thickness of the solid electrolyte layer is at most 200 nm.

[0024] (8) The present invention provides a cathode comprising a cathode active material of any one of (1) to (7) and a sulfide solid electrolyte.

[0025] (9) The present invention provides a cathode in which the sulfide-based solid electrolyte in (8) is not oxygen-doped.

[0026] (10) The present invention provides a method for preparing cathode active materials, the method comprising the following steps: preparing lithium composite metal oxide and sulfide solid electrolyte powder (S1); and coating the sulfide solid electrolyte powder onto the lithium composite metal oxide under an oxygen (O2) atmosphere (S2).

[0027] (11) The present invention provides a method for preparing cathode active materials, wherein step “S2” is carried out by a hybridizer process. Attached Figure Description

[0028] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings:

[0029] Figure 1 This is a schematic diagram of a cathode containing a cathode active material according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of a method for preparing a cathode active material according to an embodiment of the present invention;

[0031] Figure 3 This is a graph showing the EDS analysis results of the cathode active material in Example 1;

[0032] Figure 4 The image shows the EDS analysis results of the cathode active material in Comparative Example 2.

[0033] Figure 5 XPS analysis results of the various cathode active materials prepared in Example 2 and Comparative Example 1;

[0034] Figure 6 The graph shows the XRD analysis results of each cathode active material prepared in Example 2, Reference Example 1, and Reference Example 2.

[0035] Figure 7 A graph showing the charge-discharge capacity of each all-solid-state battery manufactured using the cathode active materials prepared in Example 1 and Comparative Example 1;

[0036] Figure 8 The charge-discharge capacity diagram for each cycle of an all-solid-state battery manufactured using the cathode active material prepared in Example 1, at 60°C, during the first cycle at 0.1C / 0.1C and the second cycle at 0.5C / 0.5C.

[0037] Figure 9 The charge-discharge capacity diagram for each cycle of an all-solid-state battery manufactured using the cathode active material prepared in Comparative Example 1, at 60°C, is shown when the battery undergoes its first cycle at 0.1C / 0.1C and its second cycle at 0.5C / 0.5C.

[0038] Figure 10 The graph shows the change in capacity as a function of the number of cycles when the all-solid-state battery manufactured using the cathode active materials prepared in Example 1 and Comparative Example 1 is subjected to 50 cycles of 0.5C / 0.5C at 60°C.

[0039] Figure 11 The diagram shows the charge and discharge capacity of an all-solid-state battery manufactured using the cathode active material prepared in Example 1, which was charged at gradually varying rates of 1C, 2C, 5C, and 10C and discharged at a rate of 0.5C.

[0040] Figure 12 The diagram shows the charge-discharge capacity of an all-solid-state battery fabricated using the cathode active material prepared in Comparative Example 1, obtained by charging at progressively varying rates of 1C, 2C, 5C, and 10C, and discharging at a rate of 0.5C; and

[0041] Figure 13 The diagram shows the charge-discharge capacity of an all-solid-state battery manufactured using the cathode active material prepared in Comparative Example 2, which was charged at gradually varying rates of 1C, 2C, 5C, and 10C and discharged at a rate of 0.5C. Detailed Implementation

[0042] To facilitate understanding of the invention, it will be described in more detail below. In this context, the terms and words used in this specification and claims should not be interpreted in their usual dictionary sense, but rather should be interpreted based on the inventor's ability to properly define the concepts of the terms to best explain the invention and to relate to the technical scope of the invention.

[0043] The terminology used in this invention is for illustrative purposes only, and the invention is not limited thereto. Unless the context clearly indicates otherwise, the singular form is intended to include the plural form.

[0044] <Cathode Active Materials>

[0045] This invention provides a cathode active material.

[0046] According to one embodiment of the present invention, the cathode active material comprises a core CAM containing at least a lithium composite metal oxide and a solid electrolyte layer 100 covering the core CAM, wherein the solid electrolyte layer 100 comprises an oxygen-doped sulfide solid electrolyte.

[0047] Figure 1 A cathode comprising a cathode active material according to an embodiment of the present invention is schematically shown.

[0048] like Figure 1 As shown, according to one embodiment of the present invention, the cathode active material may include a solid electrolyte layer 100 disposed on the core CAM. Furthermore, according to one embodiment of the present invention, the cathode may include a cathode active material and a sulfide-based solid electrolyte (LPSCI) disposed around the cathode active material. When the sulfide-based solid electrolyte (LPSCI) present in the cathode is in direct contact with the core CAM, side reactions may occur at the interface between the sulfide-based solid electrolyte (LPSCI) and the core CAM, thereby reducing the performance of the all-solid-state battery (cell).

[0049] The inventors of this invention discovered that when a cathode active material is manufactured by coating a core CAM with a solid electrolyte layer 100 containing an oxygen-doped solid electrolyte, the contact area between the sulfide-based solid electrolyte (LPSCI) and the cathode active material increases, thereby reducing the internal resistance of the electrode and suppressing side reactions between the cathode active material and the sulfide-based solid electrolyte (LPSCI), thus completing this invention.

[0050] The following will describe in detail a cathode active material according to an embodiment of the present invention, as well as the components constituting a cathode comprising the cathode active material.

[0051] 1. Kernel

[0052] According to one embodiment of the present invention, the core CAM of the cathode active material may contain lithium composite metal oxide.

[0053] According to one embodiment of the present invention, the lithium composite metal oxide may include rock salt-type active materials, such as LiCoO2, LiMnO2, LiNiO2, LiVO2, Li 1+x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, spinel-type active materials, such as LiMn2O4, Li(Ni) 0.5 Mn 1.5O4, anti-spinel type active materials, such as LiNiVO4 or LiCoVO4; olivine type active materials, such as LiFePO4, LiMnPO4, LiCoPO4, or LiNiPO4; silicon-containing active materials, such as Li2FeSiO4 and Li2MnSiO4; rock salt type active materials obtained by replacing part of the transition metal with a heterometallic metal, such as LiNi 0.8 Co (0.2-x) Al x O2 (0 < x < 0.2), by using heterometals or lithium titanate (e.g., Li4Ti5O) 12 Spinel-type active materials obtained by replacing part of the transition metal, such as Li 1+x Mn 2-x-y M y O4 (M is at least one of Al, Mg, Co, Fe, Ni and Zn; 0 <x+y<2)。

[0054] According to one embodiment of the present invention, the lithium composite metal oxide may comprise a compound represented by the following chemical formula 1.

[0055] [Chemical Formula 1]

[0056] LiNi 1-x-y Co x Mn y O2(0 <x,0<y,0<x+y<1)

[0057] According to one embodiment of the present invention, the core CAM can be obtained by additionally coating a lithium composite metal oxide with at least one selected from LiNbO3, LiV3O8, Li2ZrO3, and combinations thereof. Therefore, side reactions at the interface can be reduced, thereby further improving structural stability.

[0058] 2. Solid electrolyte layer

[0059] According to one embodiment of the present invention, the cathode active material may include a solid electrolyte layer 100 disposed on the core CAM. The solid electrolyte layer 100 is disposed on the core CAM to prevent side reactions between the sulfide solid electrolyte (LPSCI) and the core CAM, while increasing the contact area between the sulfide solid electrolyte (LPSCI) and the cathode active material, thereby reducing the internal resistance of the electrode.

[0060] According to one embodiment of the present invention, the undoped sulfide solid electrolyte (LPSCI) may include Li2S-P2S5, Li6PS5Cl 0.5 Br 0.5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, 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 (Where m and n are positive numbers, and Z is one of Ge, Zn, and Ga) or Li 10 GeP2S 12 .

[0061] According to one embodiment of the present invention, the undoped sulfide solid electrolyte (LPSCI) can specifically be a compound represented by the following chemical formula 2.

[0062] [Chemical Formula 2]

[0063] Li 7-a PS 6-a X a

[0064] In chemical formula 2, 0 ≤ a ≤ 2, and X is any one of Cl, Br, or I.

[0065] According to one embodiment of the present invention, the solid electrolyte layer 100 may comprise an oxygen-doped sulfide-based solid electrolyte. An oxygen-doped sulfide-based solid electrolyte (LPSCI) refers to an LPSCI whose composition differs from that of a typical LPSCI because, in the manufacturing method described below, the LPSCI is coated onto the core CAM under an "oxygen atmosphere." Specifically, in the oxygen-doped sulfide-based solid electrolyte, relative to the sulfide-based composition (PS4)... 3- In this process, sulfur (S) atoms are replaced by oxygen (O) atoms to form thiophosphate (PS3O). 3- Therefore, side reactions between the core CAM and the sulfide-based solid electrolyte (LPSCI) can be suppressed without reducing the ionic conductivity of the cathode active material.

[0066] According to one embodiment of the present invention, since the solid electrolyte layer 100 contains an oxygen-doped sulfide-based solid electrolyte, the solid electrolyte layer 100 can have an observable peak in the range of 532.5 eV to 533 eV during X-ray photoelectron spectroscopy (XPS) analysis. The peak in the 532.5 eV to 533 eV range observed in XPS analysis is due to the presence of phosphoric acid, which proves oxygen doping in the sulfide-based solid electrolyte (LPSCI).

[0067] According to one embodiment of the present invention, the thickness of the solid electrolyte layer 100 can be in the range of about 50 nm to about 200 nm. Specifically, the thickness of the solid electrolyte layer 100 can be at least about 55 nm, at least about 60 nm, at least about 65 nm, at least about 70 nm, at least about 75 nm, or at least about 80 nm, and its thickness can be at most about 195 nm, at most about 190 nm, at most about 185 nm, at most about 180 nm, at most about 175 nm, or at most about 170 nm. Therefore, when this range is met, side reactions between the core CAM and the sulfide-based solid electrolyte (LPSCI) can be suppressed without reducing the ionic conductivity of the cathode active material.

[0068] According to one embodiment of the invention, the solid electrolyte layer 100 may be included in the cathode active material, the content of which ranges from about 0.01 wt% to about 6 wt% of the core CAM weight. Specifically, the solid electrolyte layer 100 may be included in the cathode active material in a content of at least about 0.02 wt%, at least about 0.04 wt%, at least about 0.06 wt%, at least about 0.08 wt%, at least about 0.1 wt%, at least about 0.12 wt%, at least about 0.14 wt%, at least about 0.16 wt%, at least about 0.18 wt%, or at least about 0.2 wt% of the core CAM weight, and at most about 5.8 wt%, at most about 5.6 wt%, at most about 5.4 wt%, at most about 5.2 wt%, at most about 5 wt%, at most about 4.8 wt%, at most about 4.6 wt%, at most about 4.4 wt%, at most about 4.2 wt%, or at most about 4 wt%. Therefore, when this range is met, side reactions between the core CAM and the sulfide-based solid electrolyte (LPSCI) can be suppressed without reducing the ionic conductivity of the cathode active material.

[0069] <Manufacturing Methods of Cathode Active Materials>

[0070] This invention provides a method for manufacturing a cathode active material.

[0071] A method for manufacturing a cathode active material according to one embodiment of the present invention includes: preparing lithium composite metal oxide and sulfide solid electrolyte powder (S1); and coating the sulfide solid electrolyte powder onto the lithium composite metal oxide under an oxygen (O2) atmosphere (S2).

[0072] Figure 2 This is a schematic diagram of a method for preparing a cathode active material according to an embodiment of the present invention. In the following text, reference will be made to... Figure 2 The various steps of a method for manufacturing a cathode active material according to an embodiment of the present invention will be described.

[0073] 1. "S1"

[0074] According to one embodiment of the present invention, a method for manufacturing a cathode active material includes preparing lithium composite metal oxide and sulfide-based solid electrolyte powder (S1).

[0075] According to one embodiment of the present invention, lithium composite metal oxides for forming the core CAM of the cathode active material can be prepared by known methods (e.g., co-precipitation reaction).

[0076] According to one embodiment of the present invention, the sulfide-based solid electrolyte powder used to form the solid electrolyte layer 100 of the cathode active material may be free of oxygen doping.

[0077] According to one embodiment of the present invention, sulfide-based solid electrolyte powder can be represented as a compound of chemical formula 2 as follows.

[0078] [Chemical Formula 2]

[0079] Li 7-a PS 6-a X a

[0080] In chemical formula 2, 0 ≤ a ≤ 2, and X is any one of Cl, Br, or I.

[0081] 2. "S2"

[0082] According to one embodiment of the present invention, a method for manufacturing a cathode active material includes coating a sulfide-based solid electrolyte powder onto a lithium composite metal oxide under an oxygen (O2) atmosphere (S2).

[0083] According to one embodiment of the present invention, when sulfide-based solid electrolyte powder is coated onto lithium composite metal oxide in an oxygen (O2) atmosphere, oxygen is doped into the sulfide-based solid electrolyte powder.

[0084] According to one embodiment of the present invention, the oxygen (O2) atmosphere may refer to an air atmosphere with an oxygen content of about 10% to about 30% and a dew point of about -50°C.

[0085] According to one embodiment of the present invention, "S2" can be performed in a hybrid (impact milling) process.

[0086] According to one embodiment of the invention, the hybridization process is a mechanochemical fusion process in which stronger mechanical forces are applied to multiple particles to induce a mechanochemical reaction, thereby forming multiple particles. The hybridization process can be carried out by: preparing a hybridizer comprising a chamber disposed therein, the chamber having a high-speed rotator with multiple blades; supplying at least two types of particles, such as lithium composite metal oxide and sulfide solid electrolyte powder, into the chamber of the hybridizer under an oxygen atmosphere; rotating the chamber at a speed of about 5000 rpm to about 16000 rpm to disperse the lithium composite metal oxide and sulfide solid electrolyte powder; and applying kinetic and thermal energy (e.g., compression, friction, and shear stress) to the lithium composite metal oxide and sulfide solid electrolyte powder for a short period of time, from 1 minute to 10 minutes, preferably from 1 minute to 5 minutes.

[0087] According to one embodiment of the present invention, oxygen-doped sulfide-based solid electrolyte powder can be coated onto lithium composite metal oxide using a hybridization process. Furthermore, due to the difference in physical properties between the high-strength lithium composite metal oxide and the relatively soft sulfide-based solid electrolyte powder, the sulfide-based solid electrolyte may deform. Therefore, the sulfide-based solid electrolyte powder (i.e., oxygen-doped sulfide-based solid electrolyte powder) can be coated onto the lithium composite metal oxide in an amorphous form.

[0088] According to one embodiment of the present invention, coatings of amorphous sulfide-based solid electrolyte powders can be identified by X-ray diffraction (XRD). Specifically, when the sulfide-based solid electrolyte powder is coated in a crystalline state (i.e., the sulfide-based solid electrolyte powder is only adjacent to the lithium composite metal oxide without physical / chemical bonding), a peak can be observed in the range of 25 to 26, 29 to 31, and 31 to 32 degrees at the 2θ angle in XRD analysis. However, when the sulfide-based solid electrolyte powder is coated in an amorphous state (i.e., the sulfide-based solid electrolyte powder is physically / chemically bonded to the lithium composite metal oxide), no peak may be observed in the range of 25 to 26, 29 to 31, and 31 to 32 degrees at the 2θ angle in XRD analysis.

[0089] <Cathode>

[0090] The present invention provides a cathode comprising a cathode active material.

[0091] Furthermore, according to one embodiment of the present invention, the cathode may comprise a cathode active material and a sulfide solid electrolyte (LPSCI).

[0092] According to one embodiment of the present invention, the cathode can be prepared by coating a substrate with a slurry obtained by adding a cathode active material, a sulfide-based solid electrolyte (LPSCI), a binder, and a conductive material to a solvent, and then drying the substrate. Details of the binder and conductive material will be described later.

[0093] According to one embodiment of the present invention, the undoped sulfide solid electrolyte (LPSCI) can specifically be represented as a compound of chemical formula 2 as follows.

[0094] [Chemical Formula 2]

[0095] Li 7-a PS 6-a X a

[0096] In chemical formula 2, 0 ≤ a ≤ 2, and X is any one of Cl, Br, or I.

[0097] All-solid-state batteries

[0098] This invention provides an all-solid-state battery comprising a solid electrolyte self-supporting membrane.

[0099] According to one embodiment of the present invention, an all-solid-state battery may have the following structure: an anode comprising an anode current collector and an anode active material layer, a solid electrolyte self-supporting membrane, and a cathode comprising a cathode active material layer and a cathode current collector are stacked on top of each other.

[0100] According to one embodiment of the present invention, the anode current collector may be a plate-shaped substrate with conductivity. Specifically, the anode current collector may be in the form of a sheet, a film, or a foil.

[0101] According to one embodiment of the present invention, the anode current collector may contain a material that does not react with lithium. Specifically, the anode current collector may contain at least one selected from nickel, copper, stainless steel (SUS), and combinations thereof.

[0102] According to one embodiment of the present invention, the anodic active material layer may comprise an anodic active material, a solid electrolyte, a conductive material, and a binder.

[0103] According to one embodiment of the present invention, the anode active material is not specifically limited. For example, the anode active material may include carbon active materials and metal active materials.

[0104] According to one embodiment of the present invention, the carbon active material may be mesophase carbon microspheres (MCMB), graphite (e.g., highly oriented graphite (HOPG)), or amorphous carbon (e.g., hard carbon and soft carbon).

[0105] According to one embodiment of the present invention, the metal active material may be In, Al, Si and Sn, or an alloy containing at least one of In, Al, Si and Sn.

[0106] According to one embodiment of the present invention, the solid electrolyte can be an oxide-based solid electrolyte or a sulfide-based solid electrolyte, and is preferably a sulfide-based solid electrolyte. A detailed description of the sulfide-based solid electrolyte has already been described above, therefore, its detailed description will be omitted below.

[0107] According to one embodiment of the present invention, the conductive material is a component that forms an electron transport path within the electrode. This conductive material can be sp 2 Carbon materials, such as carbon black, conductive graphite, ethylene black, carbon nanotubes, or graphene.

[0108] According to one embodiment of the present invention, the adhesive may comprise butadiene rubber (BR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or carboxymethyl cellulose (CMC).

[0109] According to one embodiment of the present invention, the cathode active material layer may comprise a cathode active material, a solid electrolyte, a conductive material, and a binder.

[0110] According to one embodiment of the present invention, the cathode active material has been described above, and its detailed description will be omitted below.

[0111] According to one embodiment of the present invention, the solid electrolyte may be an oxide-based solid electrolyte or a sulfide-based solid electrolyte. Preferably, the solid electrolyte may include a sulfide-based solid electrolyte having higher lithium-ion conductivity.

[0112] According to one embodiment of the present invention, the conductive material and adhesive have been described above, and their detailed description will be omitted below.

[0113] According to one embodiment of the present invention, the cathode current collector may be a plate-shaped substrate with conductivity. Specifically, the cathode current collector may be in sheet or film form.

[0114] According to one embodiment of the present invention, the cathode current collector may contain at least one or a combination thereof selected from indium, copper, magnesium, aluminum, stainless steel, and iron.

[0115] According to one embodiment of the present invention, a solid electrolyte self-supporting membrane is located between the anode active material layer and the cathode active material layer for transporting lithium ions.

[0116] One embodiment of the present invention will be described in detail below to enable those skilled in the art to easily reproduce the embodiment. However, the present invention can be implemented in many forms and is not limited to the embodiment described herein.

[0117] Example 1

[0118] <Preparation of Lithium Composite Metal Oxides>

[0119] Preparation of lithium composite metal oxide LiNi 0.8 Co 0.1 Mn 0.1 O2. LiOH and niobium ethanol were dissolved in an alcohol solvent at a molar ratio of 1:1. Then, the alcohol solvent was reacted with lithium composite metal oxide LiNi. 0.8 Co 0.1 Mn 0.1 O2 was mixed. The mixture was then dried and heat-treated at 300°C to 500°C for 1 hour to produce an average particle size (D). 50 LiNi, a lithium composite metal oxide with a diameter of approximately 3 μm to 5 μm and coated with LiNbO3. 0.8 Co 0.1 Mn 0.1 O2.

[0120] <Preparation of cathode active materials>

[0121] 100 parts by weight of the prepared lithium composite metal oxide and 0.2 parts by weight of Li6PS5Cl solid electrolyte powder were added to the reactor. Then, a mixing and coating process was carried out in air at a speed of about 5000 rpm to about 15000 rpm for 1 minute to prepare the cathode active material.

[0122] Example 2

[0123] The cathode active material was prepared using the same method as in Example 1, except that 100 parts by weight of the prepared lithium composite metal oxide and 4 parts by weight of Li6PS5Cl solid electrolyte powder were added to the reactor and mixed and coated.

[0124] Comparative Example 1

[0125] Preparation of LiNi 0.8 Co 0.1 Mn 0.1 O2 lithium composite metal oxide, LiOH and niobium ethanol are dissolved in an alcohol solvent at a molar ratio of 1:1, and then the alcohol solvent is reacted with LiNi0.8 Co 0.1 Mn 0.1 O2 lithium composite metal oxide is mixed. The mixture is then dried and heat-treated at 300°C to 500°C for 1 hour to produce the cathode active material, which has the composition LiNi. 0.8 Co 0.1 Mn 0.1 O2, average particle size (D) 50 The size is 3μm to 5μm, and it is coated with LiNbO3.

[0126] Comparative Example 2

[0127] The preparation method of the cathode active material is the same as that in Example 1, except that the hybrid coating process is carried out in an inert gas (Ar) atmosphere.

[0128] Reference example 1

[0129] 100 parts by weight of the cathode active material prepared in Comparative Example 1 were mixed with 4 parts by weight of the material with an average particle size (D). 50 The mixture consists of 1μm Li6PS5Cl solid electrolyte powder.

[0130] Reference example 2

[0131] 100 parts by weight of the cathode active material prepared in Comparative Example 1 and 7 parts by weight of the material with an average particle size (D) 50 The mixture consists of 1μm Li6PS5Cl solid electrolyte powder.

[0132] Experimental Example 1 - EDS Analysis

[0133] EDS analysis was performed on the cathode active materials prepared in Example 1 and Comparative Example 2 (accelerating voltage 5 kV; measuring equipment: JSM-7200F, Nippon Electronics Corporation). The results are as follows: Figure 3 and Figure 4 As shown.

[0134] Figure 3 This is a graph showing the EDS analysis results of the cathode active material in Example 1. Figure 4 The image shows the EDS analysis results of the cathode active material in Comparative Example 2. Figure 3 and Figure 4 As shown, in Example 1, which uses a hybrid coating process under an oxygen atmosphere, oxygen was detected based on EDS analysis results; while in Comparative Example 2, which uses a hybrid coating process under an inert gas (Ar) atmosphere, oxygen was not detected in other parts of the lithium composite metal oxide coated with the solid electrolyte, except for the oxygen present in the lithium composite metal oxide, based on EDS analysis results.

[0135] Experimental Example 2 - XPS Analysis

[0136] In a drying chamber, XPS analysis (VGMultilab ESCA system; 220i) was performed on the cathode active materials prepared in Example 2 and Comparative Example 1. The results are as follows: Figure 5 As shown.

[0137] Figure 5 The above are XPS analysis results of the cathode active materials prepared in Example 2 and Comparative Example 1.

[0138] like Figure 5 As shown, in Comparative Example 1, which does not have an oxygen-doped solid electrolyte, peaks of oxygen bound to Li (around 529 eV) and peaks caused by LiNbO3 (around 531 eV) can be observed. Meanwhile, in Example 2, which has an oxygen-doped solid electrolyte, peaks caused by thiophosphate (PS3O3) can be observed. 3- The peak caused by Li (around 532 eV) was observed, but the peaks caused by oxygen bound to Li (around 529 eV) and by LiNbO3 (around 531 eV) were not observed.

[0139] Experimental Example 3 - XRD Analysis

[0140] For the cathode active materials prepared in Example 2, as well as Reference Examples 1 and 2, XRD spectra were measured using an Empyrean diffractometer (Malvern Panalytical Ltd) under the conditions of CuKα, 2θ (Bragg angle) = 25°-35°, and scan rate = 5° / 1min. The results are as follows: Figure 6 As shown.

[0141] Figure 6 The images show the XRD analysis results of the cathode active materials prepared in Example 2, as well as Reference Example 1 and Reference Example 2.

[0142] like Figure 6 As shown, in Reference Example 1 and Reference Example 2, the lithium composite metal oxide and the solid electrolyte were only mixed, without any mixing and coating process, and peaks formed by the solid electrolyte with crystalline morphology could be observed.

[0143] Meanwhile, in Example 2, the solid electrolyte was coated onto the lithium composite metal oxide using a hybrid coating process that involved gas-driven particle collisions. In this case, due to the difference in physical properties between the high-strength lithium composite metal oxide and the softer sulfide-based solid electrolyte powder, the solid electrolyte may deform. Therefore, the solid electrolyte powder can be coated onto the surface of the lithium composite metal oxide in an amorphous form. This is because no peaks formed by the crystalline solid electrolyte were observed in the cathode active material of Example 2. Figure 6 As shown, this indicates that the solid electrolyte is coated on the surface of the lithium composite metal oxide in an amorphous form.

[0144] Experiment Example 4 - Battery Evaluation

[0145] For each cathode active material prepared in Example 1 and Comparative Example 1, a cathode was made by additionally mixing 85 parts by weight of cathode active material (excluding the solid electrolyte layer), 14 parts by weight of Li6PS5Cl sulfide solid electrolyte (solid electrolyte layer and / or solid electrolyte powder), 1 part by weight of conductive material (carbon black) and 1 part by weight of binder (PTFE).

[0146] 0.15 g of Li6PS5Cl sulfide-based solid electrolyte powder was placed into a 13 mm diameter polyetheretherketone (PEEK) mold and pressed for 1 minute under a pressure of 1 ton. Subsequently, the prepared cathode was placed into the mold and pressed for 1 minute under a pressure of 7 tons. Furthermore, Li... 0.5 After replacing the anode with an In film, the film is bonded together under a pressure of 60 MPa to produce various all-solid-state batteries.

[0147] For each fabricated all-solid-state battery, at a temperature of 60°C, it was first charged at a constant current of 0.1C to the upper limit voltage of 3.7V, and then discharged at a constant current of 0.1C to the discharge termination voltage of 1.9V. The charge-discharge capacity curve is shown below. Figure 7 As shown in the figure. In addition, the 0.1C charging capacity, 0.1C discharging capacity, and charge / discharge efficiency (i.e., the ratio of discharging capacity to charging capacity) are shown in Table 1 below.

[0148] [Table 1]

[0149]

[0150] Figure 7 The charge / discharge capacity diagram shows the charge / discharge capacity of each all-solid-state battery manufactured using the cathode active materials prepared in Example 1 and Comparative Example 1.

[0151] like Figure 7 As shown in Table 1, it can be seen that the solid electrolyte layer containing oxygen-doped solid electrolyte slightly improves the charge and discharge efficiency, without reducing the initial capacity and efficiency.

[0152] Experimental Example 5 - High Temperature Stability Assessment

[0153] For the all-solid-state battery fabricated in Example 4, at a temperature of 60°C, it was first charged at a constant current of 0.1C to the upper limit voltage of 3.7V, and then discharged at a constant current of 0.1C to the discharge termination voltage of 1.9V, for the first cycle. From the second cycle onwards, a constant current of 0.5C was applied. Its charge-discharge capacity diagram is shown below. Figure 8 and Figure 9 As shown. Furthermore, 50 cycles were performed with a constant current of 0.5C. Figure 10 The graph shows the change in capacity with the number of cycles.

[0154] Figure 8 The graph shows the charge-discharge capacity of an all-solid-state battery manufactured using the cathode active material prepared in Example 1 at 60°C, with the first cycle at 0.1C / 0.1C and the second cycle at 0.5C / 0.5C. Figure 9 The graph shows the charge-discharge capacity of an all-solid-state battery made using the cathode active material prepared in Comparative Example 1 at 60°C for the first cycle at 0.1C / 0.1C and the second cycle at 0.5C / 0.5C. Figure 10 The graph shows the capacity of an all-solid-state battery manufactured using the cathode active materials prepared in Example 1 and Comparative Example 1 as a function of the number of cycles after 50 cycles at 60°C under 0.5C / 0.5C conditions.

[0155] like Figures 8 to 10 As shown, it can be seen that, compared with Comparative Example 1 without a solid electrolyte layer, Example 1 with a solid electrolyte layer containing an oxygen-doped sulfide-based solid electrolyte maintains higher capacity and lower resistance at a higher temperature of 60°C, and the cycling characteristics are improved, thereby further improving high-temperature stability.

[0156] Experimental Example 6 - Charge / Discharge Rate Evaluation

[0157] For each cathode active material prepared in Example 1, Comparative Example 1 and Comparative Example 2, a cathode was prepared by additionally mixing 85 parts by weight of cathode active material, 14 parts by weight of Li6PS5Cl sulfide solid electrolyte, 1 part by weight of conductive material (carbon black) and 1 part by weight of binder (PTFE).

[0158] 0.15 g of Li6PS5Cl sulfide-based solid electrolyte powder was placed into a 13 mm diameter polyetheretherketone (PEEK) mold and pressed for 1 minute under a pressure of 1 ton. Subsequently, the prepared cathode was placed into the mold and pressed for 1 minute under a pressure of 7 tons. Furthermore, Li... 0.5 After replacing the anode with an In film, the film is bonded together under a pressure of 60 MPa to produce various all-solid-state batteries.

[0159] For each manufactured all-solid-state battery, the formation process involves first charging at a constant current of 0.1C to the upper limit voltage of 3.7V at a temperature of 60°C, followed by discharging at a constant current of 0.1C to the discharge termination voltage of 1.9V. Furthermore, the battery is charged at progressively higher rates of 1C, 2C, 5C, and 10C, and then discharged at a rate of 0.5C. Figures 11 to 13 A graph of the charge / discharge capacity is shown, and Table 2 shows the available capacity.

[0160] [Table 2]

[0161]

[0162] Figure 11 The graph shows the charge and discharge capacity of an all-solid-state battery manufactured using the cathode active material prepared in Example 1, when charged at gradually varying rates of 1C, 2C, 5C, and 10C and discharged at a rate of 0.5C. Figure 12 The graph shows the charge-discharge capacity of an all-solid-state battery manufactured using the cathode active material prepared in Comparative Example 1, which was charged at gradually varying rates of 1C, 2C, 5C, and 10C and discharged at a rate of 0.5C.

[0163] Figure 13 The graph shows the charge-discharge capacity of an all-solid-state battery manufactured using the cathode active material prepared in Comparative Example 2, which was charged at gradually varying rates of 1C, 2C, 5C, and 10C and discharged at a rate of 0.5C.

[0164] like Figures 11 to 13 As shown, it can be seen that when charging by gradually changing the charging rate to 1C, 2C, 5C and 10C, the reversible capacity measured in Example 1 is greater than that in Comparative Example 1 and Comparative Example 2.

[0165] According to one embodiment of the present invention, the cathode active material helps to suppress side reactions at the interface between the cathode material and the solid electrolyte, reduce the internal resistance of the electrode, and improve the high-temperature stability and performance of the cathode material.

[0166] According to one embodiment of the present invention, the method for preparing cathode active materials can help suppress side reactions occurring at the interface between the cathode material and the solid electrolyte, reduce the internal resistance of the electrode, and improve the high-temperature stability and performance of the cathode material.

[0167] Although the invention has been described above in conjunction with exemplary embodiments and accompanying drawings, the invention is not limited thereto. Those skilled in the art can make various modifications and changes to it without departing from the spirit and scope of the appended claims.

Claims

1. A cathode active material comprising: A core containing lithium-ion composite metal oxides; and A solid electrolyte layer is disposed on the core. in, The solid electrolyte layer contains an oxygen-doped sulfide solid electrolyte.

2. The cathode active material according to claim 1, wherein the weight of the solid electrolyte layer is 0.01 wt% to 6 wt% of the total weight of the lithium composite metal oxide.

3. The cathode active material according to claim 1, wherein the solid electrolyte layer has a peak in the range of 532.5 eV to 533 eV when analyzed by X-ray photoelectron spectroscopy (XPS).

4. The cathode active material according to claim 1, wherein the oxygen-doped sulfide solid electrolyte comprises thiophosphate PS3O. 3- .

5. The cathode active material according to claim 1, wherein the core is obtained by coating the lithium composite metal oxide with LiNbO3.

6. The cathode active material according to claim 1, wherein the thickness of the solid electrolyte layer is less than or equal to 200 nm.

7. A cathode comprising a cathode active material according to any one of claims 1-6 and a sulfide-based solid electrolyte.

8. The cathode according to claim 7, wherein the sulfide-based solid electrolyte is undoped with oxygen.

9. The cathode according to claim 7, wherein the sulfide-based solid electrolyte is represented by the following chemical formula 2: [Chemical Formula 2] Li 7-a PS 6-a X a , Where 0 ≤ a ≤ 2, and "X" is one of Cl, Br or I.

10. A method for manufacturing a cathode active material, comprising the following steps: S1: Preparation of lithium composite metal oxide and sulfide solid electrolyte powders; and S2: The sulfide-based solid electrolyte powder is coated onto the lithium composite metal oxide under an oxygen (O2) atmosphere.

11. The method of claim 10, wherein step S2 is performed in a hybridization process.

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