Cathode active material for all-solid-state battery, including the same containing a ternary oxide coating, and method for manufacturing the same

Abstract

The present invention relates to a cathode active material for an all-solid-state battery, including a cathode active material containing a ternary oxide coating and a method for manufacturing the same. Specifically, the present invention relates to a cathode active material for an all-solid-state battery, including: active material particles; and a coating covering at least a part of the surface of the active material particles, wherein the coating contains lithium (Li), niobium (Nb), and at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof.

Description

Technical Field

[0001] The present disclosure relates to a cathode active material for an all-solid-state battery and a method for manufacturing the same. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not constitute prior art.

[0003] Since the commercialization of lithium secondary batteries in the early 1990s, many improvements have been made in materials for cathodes and anodes or battery designs to increase the energy density. Moreover, these batteries are applied in various fields, from small products such as mobile phones and laptop computers to medium to large products such as electric vehicles and energy storage systems.

[0004] Currently widely used lithium secondary batteries mainly use a liquid electrolyte composed of organic solvents, but if there is an internal short circuit or the temperature rises, the liquid electrolyte has a risk of explosion. To address this risk, all-solid-state batteries using solid electrolytes have been developed. All-solid-state batteries are very safe, and thus are considered to have advantages over other types of batteries from the perspectives of simplifying safety devices and productivity. Therefore, the development of solid electrolytes with high ionic conductivity is being actively carried out, and attempts have been made to improve the performance of all-solid-state batteries by focusing on the interfacial reaction between the solid electrolyte and the cathode active material.

[0005] Meanwhile, examples of cathode active materials currently being actively researched and developed may include LiNiO2, LiMn2O4, LiFePO4, Li(Ni x Co y Mn z )O2, etc.

[0006] However, LiNiO2 is difficult to synthesize and also has poor thermal stability, making it difficult to commercialize. LiMn2O4 is a low-cost product and has been commercialized in some cases, but due to the Jahn-Teller distortion caused by Mn 3+ , its service life is not ideal. LiFePO4 is inexpensive and has excellent safety, and thus many studies are currently being conducted with the aim of using it in hybrid electric vehicles (HEVs), but its practical application has been difficult due to its low conductivity.

[0007] In recent years, the most popular material is Li(Ni x Co y Mn z)O2. Compared with LiCoO2, this material is inexpensive and has a high capacity, and can also be used under high-pressure conditions. However, the rate performance and life characteristics at high temperatures are not good. In-depth research is being conducted on methods of coating the surface of the cathode active material with a metal having high electrical conductivity or doping its interior with materials such as Al, Mg, Ti, Zr, Sn, Ca, Ag, and Zn.

[0008] For example, Korean Patent No. 10-277796 discloses a technique for forming a metal oxide coating by coating the surface of a cathode active material with a metal such as Mg, Al, Co, K, Na, or Ca and performing heat treatment in an oxidizing atmosphere.

[0009] However, additional research is still needed to improve battery performance by reducing the resistance between the cathode active material and the solid electrolyte and increasing the electrical conductivity. Summary of the Invention

[0010] The present disclosure provides a cathode active material for an all-solid-state battery and a method for manufacturing the same. The cathode active material includes a coating containing a ternary oxide, which can reduce the battery resistance and thereby improve the battery performance.

[0011] The present disclosure is not limited to the foregoing, and can be clearly understood through the following description and implemented by the means described in the claims and their combinations.

[0012] One form of the present disclosure provides a cathode active material for an all-solid-state battery, including: active material particles; and a coating covering at least a part of the surface of the active material particles, wherein the coating contains lithium (Li), niobium (Nb), and at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof.

[0013] The active material particles may include a compound represented by the following Chemical Formula 1:

[0014] [Chemical Formula 1]

[0015] Li x A y Nb w Ni 1-a-b Co a M b O2.

[0016] In Chemical Formula 1, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, M is at least one element selected from manganese (Mn), aluminum (Al), magnesium (Mg), and combinations thereof, and x, y, w, a, and b are 0.98 ≤ x ≤ 1.02, 0 ≤ y ≤ 0.01, 0 ≤ w ≤ 0.8, 0 < a ≤ 0.1, and 0 ≤ b ≤ 0.1, respectively.

[0017] The coating may include lithium oxide represented by Chemical Formula 2 below:

[0018] [Chemical Formula 2]

[0019] LiNb c A d O3.

[0020] In Chemical Formula 2, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, and c and d are 0 < c ≤ 0.8 and 0 < d ≤ 0.01, respectively.

[0021] The cathode active material may contain niobium (Nb) at a concentration of 11,000 ppm to 12,000 ppm.

[0022] The cathode active material may contain vanadium (V) at a concentration of 5,400 ppm to 8,600 ppm.

[0023] The cathode active material may contain zirconium (Zr) at a concentration of 5,400 ppm to 8,600 ppm.

[0024] Another form of the present disclosure provides a method for manufacturing a cathode active material for an all-solid-state battery, including: preparing a mixture including active material particle precursors, lithium (Li) precursors, niobium (Nb) precursors, and at least one material selected from vanadium (V) precursors, zirconium (Zr) precursors, and combinations thereof; stirring the mixture; and calcining the stirred product.

[0025] The mixture may be prepared by adding a solvent to the lithium (Li) precursors and at least one substance selected from vanadium (V) precursors, zirconium (Zr) precursors, and combinations thereof and mixing, adding the resulting mixture to the niobium (Nb) precursors and mixing, and adding the resulting mixture to the active material particle precursors.

[0026] The active material particle precursors, lithium (Li) precursors, and zirconium (Zr) precursors may be in the powder phase, and the niobium (Nb) precursors and vanadium (V) precursors may be in the liquid phase.

[0027] The method may further include drying after stirring the mixture.

[0028] In the method, the stirred product may be calcined in an oxygen atmosphere at 300°C to 800°C for 1 hour to 5 hours.

[0029] According to the present disclosure, the battery resistance can be reduced, and thus an all-solid-state battery having improved battery performance such as battery capacity, coulombic efficiency, etc. can be obtained.

[0030] The effects of the present disclosure are not limited to the foregoing, and it should be understood to include all effects that can be reasonably expected from the following description.

[0031] Based on the description provided herein, other applicable fields will become apparent. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to better understand the present disclosure, various forms thereof will now be described with reference to the accompanying drawings by way of examples, wherein:

[0033] Figure 1 shows a all-solid-state battery according to the present disclosure;

[0034] Figure 2 is Figure 1 an enlarged view of part A of the cathode shown;

[0035] Figure 3 shows a cathode active material according to the present disclosure;

[0036] Figure 4 is a flowchart showing a manufacturing process of a cathode active material according to the present disclosure;

[0037] Figure 5 shows the analysis results of the particle size distribution of various samples of Test Example 1;

[0038] Figure 6A 、 6B and 6C show the results of X-ray photoelectron spectroscopy (XPS) analysis of the coating of the cathode active material of Example 1, Figure 6A shows the XPS spectral results of O1s, Figure 6B shows the XPS spectral results of Nb 3d, and FIG. 6c shows the XPS spectral results of V 2p;

[0039] Figure 7 shows the results of scanning electron microscopy / energy dispersive X-ray spectroscopy (SEM-EDS) analysis on the surface of the cathode active material of Example 1;

[0040] Figure 8 shows the results of SEM-EDS analysis on the surface of the cathode active material of Example 2;

[0041] Figure 9 shows the results of SEM-EDS analysis on the surface of the cathode active material of Example 3;

[0042] Figure 10 shows the results of transmission electron microscopy (TEM) analysis on the surface and inside of the cathode active material of Example 1;

[0043] Figure 11 It is the TEM-EDS spectral result of the cathode active material of Example 1;

[0044] Figure 12 It shows the measurement results of the battery capacity of the all-solid-state batteries of Examples 1 to 3 and Comparative Examples 1 and 2;

[0045] Figure 13 It shows the SEM analysis result of the cross-section of the cathode layer of the all-solid-state battery of Example 1;

[0046] Figure 14 It shows the EDS analysis result of the cross-section of the cathode layer of the all-solid-state battery of Example 1; and

[0047] Figure 15 It shows the EDS spectral result of the cross-section of the cathode layer of the all-solid-state battery of Example 1.

[0048] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. Detailed Description

[0049] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals denote the same or corresponding components and features.

[0050] From the following preferred forms in conjunction with the drawings, the above and other objects, features, and advantages of the present disclosure will be more clearly understood. However, the present disclosure is not limited to the various forms disclosed herein and can be modified into different forms. These forms are provided to thoroughly explain the present disclosure and fully convey the spirit of the present disclosure to those skilled in the art.

[0051] Throughout the drawings, the same reference numerals will refer to the same or similar elements. For the clarity of the present disclosure, the dimensions of the structures are depicted as larger than their actual dimensions. It will be understood that although terms such as "first", "second", etc. may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present disclosure, the "first" element discussed below can be referred to as the "second" element. Similarly, the "second" element can also be referred to as the "first" element. As used herein, the singular form is intended to also include the plural form unless the context clearly indicates otherwise.

[0052] It is further understood that the terms "comprising", "including", "having" when used in this specification specify the presence of the stated features, integers, steps, operations, elements, components or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components or combinations thereof. Also, it will be understood that when an element such as a layer, film, region or sheet is referred to as being "on" another element, it can be directly on the other element or there can be intervening elements between them. Similarly, when an element such as a layer, film, region or sheet is referred to as being "under" another element, it can be directly under the other element or there can be intervening elements between them.

[0053] Unless otherwise specified, all numbers, values and / or representations indicating amounts of components, reaction conditions, polymer compositions and mixtures used herein are to be considered approximations that include various uncertainties affecting the measured values, which uncertainties inherently arise when obtaining these values, and thus should be understood to be modified in all instances by the term "about". In addition, when a numerical range is disclosed in this specification, unless otherwise specified, the range is continuous and includes all values from the minimum value of the range to its maximum value. In addition, when such a range pertains to integer values, unless otherwise specified, it includes all integers from the minimum value to the maximum value.

[0054] Figure 1 A solid-state battery according to the present disclosure is shown. Referring thereto, the solid-state battery 1 includes a cathode 10, an anode 20, and a solid electrolyte layer 30 interposed between the cathode 10 and the anode 20.

[0055] Figure 2 is Figure 1 An enlarged view of a portion A of the cathode 10 shown. Referring thereto, the cathode 10 may include a cathode active material 11 and a solid electrolyte 12 disposed around the cathode active material 11.

[0056] The present disclosure aims to increase the stability of the interface formed by the cathode active material 11 and the solid electrolyte 12 inside the cathode 10, thereby reducing the internal resistance of the battery.

[0057] The solid electrolyte 12 is not particularly limited and can be, for example, an oxide-based solid electrolyte or a sulfide-based solid electrolyte. However, it may be desirable to use a sulfide-based solid electrolyte having a high lithium ion conductivity.

[0058] Examples of sulfide-based solid electrolytes can include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is any one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In), Li 10 GeP2S 12 etc.

[0059] Figure 3 FIG. 11 shows a cathode active material 11 according to the present disclosure. Referring thereto, the cathode active material 11 may include active material particles 111 and a coating 113 covering at least a part of the surface of the active material particles 111.

[0060] In the present disclosure, in order to increase the stability of the interface between the cathode active material 11 and the solid electrolyte 12 and increase the ionic conductivity of lithium ions, niobium (Nb) and at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof may be added or doped to the active material particles 111 and / or the coating 113.

[0061] Specifically, the active material particles 111 may include a compound represented by the following Chemical Formula 1:

[0062] [Chemical Formula 1]

[0063] Li x A y Nb w Ni 1-a-b Co a M b O2.

[0064] In Chemical Formula 1, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, M is at least one element selected from manganese (Mn), aluminum (Al), magnesium (Mg), and combinations thereof, and x, y, w, a, and b are 0.98 ≤ x ≤ 1.02, 0 ≤ y ≤ 0.01, 0 ≤ w ≤ 0.8, 0 < a ≤ 0.1, and 0 ≤ b ≤ 0.1, respectively.

[0065] Here, when A contains both vanadium (V) and zirconium (Zr), the compound of Chemical Formula 1 can be represented as follows.

[0066] Li x (V 1-z Zr z ) y Nb w Ni 1-a-b Co a M b O2 (where z is a number less than 1 but greater than 0)

[0067] Moreover, the coating 113 may contain lithium oxide represented by the following Chemical Formula 2:

[0068] [Chemical Formula 2]

[0069] LiNb c A d O3.

[0070] In Chemical Formula 2, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, and c and d are 0 < c ≤ 0.8 and 0 < d ≤ 0.01, respectively.

[0071] When A contains both vanadium (V) and zirconium (Zr), the compound of Chemical Formula 2 can be represented as follows.

[0072] LiNb c (V 1-z Zr z ) d O3 (where z is a number less than 1 but greater than 0)

[0073] In the present disclosure, in order to add or dope the active material particles 111 and / or the coating 113 containing niobium (Nb) and at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, the cathode active material 11 is manufactured by the sol-gel method.

[0074] Figure 4It is a flowchart showing the manufacturing process of the cathode active material according to the present disclosure. Referring to this, the method includes preparing a mixture that contains a precursor of active material particles, a lithium (Li) precursor, a niobium (Nb) precursor, and at least one substance selected from a vanadium (V) precursor, a zirconium (Zr) precursor, and their combination (S1), stirring the mixture (S2), and calcining the stirred product (S3).

[0075] The mixture can be prepared by adding a solvent, a lithium (Li) precursor, and at least one substance selected from a vanadium (V) precursor, a zirconium (Zr) precursor, and their combination, mixing them, adding the niobium (Nb) precursor to the resulting mixture and mixing, and adding the precursor of active material particles to the resulting mixture.

[0076] The lithium (Li) precursor is not particularly limited, but can be, for example, lithium ethoxide and can be used in the powder phase.

[0077] The vanadium (V) precursor is not particularly limited, but can be, for example, vanadium ethoxide and can be used in the liquid phase.

[0078] The zirconium (Zr) precursor is not particularly limited, but can be, for example, zirconium ethoxide and can be used in the powder phase.

[0079] The niobium (Nb) precursor is not particularly limited, but can be, for example, niobium ethoxide and can be used in the liquid phase.

[0080] As used herein, the "precursor of active material particles" does not refer to a raw material for adding or doping specific elements such as the lithium (Li) precursor, etc., but refers to the original state of the above-mentioned active material particles before being doped with niobium (Nb), vanadium (V), zirconium (Zr), etc. Specifically, the precursor of active material particles can be a compound represented by Li(Ni x Co y Mn z )O2.

[0081] The precursor of active material particles used can be in the powder phase.

[0082] The solvent can be used without limitation as long as it can disperse and / or dissolve the precursors, and can include, for example, absolute ethanol.

[0083] Each mixing condition for preparing the mixture is not particularly limited. For example, mixing can be carried out at a temperature of 25 °C to 50 °C at a rate of 300 rpm to 500 rpm for 1 minute to 3 hours.

[0084] Thereafter, the mixture is stirred to provide a stirred product, wherein lithium (Li), vanadium (V), zirconium (Zr), etc. are attached to the surface of the active material particle precursor (S2) in the form of elements, compounds or oxides. Then, the resultant obtained thereby can be dried to provide a powder.

[0085] Finally, the stirred product is calcined in an oxygen atmosphere to obtain the above-mentioned cathode active material (S3). The calcination conditions are not particularly limited. For example, the calcination can be carried out in an oxygen atmosphere at a temperature of 300 °C to 800 °C for 1 hour to 5 hours.

[0086] A better understanding of the present disclosure can be obtained through the following examples. These examples are only presented to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure.

[0087] Examples 1 to 3 and Comparative Examples 1 and 2

[0088] Corresponding mixtures are prepared using the amounts of components shown in Table 1 below.

[0089] [Table 1]

[0090]

[0091] [Example 1]

[0092] In the composition of Example 1 according to Table 1, lithium ethoxide (powder) and vanadium ethoxide (liquid) are added to absolute ethanol and stirred at about 350 rpm and 35 °C for about 15 minutes. The stirred product is added with niobium ethoxide (liquid) and stirred under the same conditions. Thereafter, the active material particle precursor is added thereto to prepare a mixture.

[0093] The mixture is stirred at about 350 rpm and 45 °C for about 1 hour to 1 hour 30 minutes, and then dried to obtain a powdery product.

[0094] The product obtained thereby is calcined at about 400 °C for about 3 hours to provide a cathode active material.

[0095] The cathode active material, a sulfide-based solid electrolyte, a conductor (Super-P), a binder, and a dispersant are mixed in a ratio of 76.8:18.5:1.4:2.3:1 to prepare a slurry, which is then applied to a substrate and dried to form a cathode layer.

[0096] The anode active material, a solid electrolyte, a binder, and a dispersant are mixed in a ratio of 75.8:19.0:2.2:2.9 to prepare a slurry, which is then applied to a substrate and dried to form an anode layer.

[0097] Adjust the load level depending on the weight and area of the cathode layer to approximately 20.0 mg / cm 2 and adjust the load level depending on the weight and area of the anode layer to approximately 11.0 mg / cm 2 .

[0098] Form a solid electrolyte layer with a sulfide-based solid electrolyte, then place the cathode layer and the anode layer on its opposite sides, and press at a pressure of 32 MPa for approximately 5 minutes to complete the all-solid-state battery.

[0099] [Example 2]

[0100] Manufacture the cathode active material and the all-solid-state battery in the same manner as in Example 1, except that a mixture is prepared using the composition of Example 2 in Table 1.

[0101] [Example 3]

[0102] In the composition of Example 1 in Table 3, lithium ethoxide (powder) and zirconium ethoxide (powder) are added to absolute ethanol and stirred at approximately 350 rpm and 35 °C for approximately 15 minutes. The stirred product is added with niobium ethoxide (liquid) and stirred under the same conditions. Thereafter, the active material particle precursor is added thereto to prepare a mixture.

[0103] The mixture is stirred at approximately 350 rpm and 45 °C for approximately 1 hour to 1 hour 30 minutes, and then dried to obtain a powdery product.

[0104] The product thus obtained is calcined at approximately 700 °C for approximately 5 hours to provide the cathode active material.

[0105] Subsequent steps are carried out in the same manner as in Example 1 to manufacture the all-solid-state battery.

[0106] [Comparative Example 1]

[0107] As shown in Table 1 above, the cathode active material used is a separate active material particle precursor without a separate coating formed thereon. Other than this, the all-solid-state battery is manufactured in the same manner as in Example 1.

[0108] [Comparative Example 2]

[0109] Manufacture the cathode active material and the all-solid-state battery in the same manner as in Example 1, except that a mixture is prepared using the composition of Comparative Example 2 in Table 1.

[0110] Test Example 1 - Particle Size Distribution Analysis

[0111] The particle size distributions of the cathode active materials of Examples 1 to 3 and Comparative Examples 1 and 2 were analyzed using Cilas 1090 and Scinco. The results are shown in Table 2 below and Figure 5 in.

[0112] [Table 2]

[0113]

[0114] From Table 2 and Figure 5 it can be clearly seen that there are almost no differences in the particle sizes of the cathode active materials of Examples 1 to 3 and Comparative Examples 1 and 2. Therefore, it can be concluded that there is no phenomenon of aggregation of the cathode active material.

[0115] Test Example 2 - XPS (X-ray Photoelectron Spectroscopy) Analysis

[0116] XPS analysis was performed on the coating of the cathode active material of Example 1. The results are shown in Figures 6A to 6C in.

[0117] Figure 6A shows the XPS spectral results of O1s, Figure 6B shows the XPS spectral results of Nb 3d, and Figure 6C shows the XPS spectral results of V2p.

[0118] From Figure 6A it can be seen that the coating has Nb2O5 and V2O5 bonds. Additionally, from Figure 6B it can be seen that NbO2 and Nb2O5 are coated on the surface of the active material particles. Additionally, from Figure 6C it can be seen that a peak of V2O5 appears. Therefore, it can be concluded that in the cathode active material of Example 1, NbO2, Nb2O5, and V2O5 play a role in improving the performance of all-solid-state batteries.

[0119] Test Example 3 - SEM-EDS Analysis on the Surface of the Cathode Active Material

[0120] SEM-EDS (Scanning Electron Microscope / Energy Dispersive X-ray Spectroscopy) analysis was performed on the surfaces of the cathode active materials of Examples 1 to 3. The results are shown in Figures 7 to 9 in.

[0121] Figure 7 shows the results of the SEM-EDS analysis on the surface of the cathode active material of Example 1, Figure 8 shows the results of the SEM-EDS analysis on the surface of the cathode active material of Example 2, and Figure 9 shows the results of the SEM-EDS analysis on the surface of the cathode active material of Example 3.

[0122] Based on the above results, it can be found that niobium (Nb) and vanadium (V) or zirconium (Zr) are uniformly distributed on the surface of the active material particles of the cathode active material according to the present disclosure.

[0123] Test Example 4 - TEM (transmission electron microscopy) analysis on the surface and inside of the cathode active material

[0124] TEM analysis was performed on the surface and inside of the cathode active material of Example 1. Specifically, analysis was performed using JEM-ARM300F (JEOL) at an acceleration voltage of 160 kV. The results are shown in Figure 10 In addition, Figure 11 shows the TEM-EDS spectral results of the cathode active material of Example 1.

[0125] From this, it can be found that niobium (Nb) and vanadium (V) are distributed on the surface and inside of the cathode active material, indicating that niobium (Nb) and vanadium (V) contribute to the movement of lithium ions.

[0126] Test Example 5 - Inductively coupled plasma (ICP) analysis

[0127] ICP analysis was performed on the cathode active materials of Examples 1 to 3 and Comparative Examples 1 and 2. The results are shown in Table 3 below.

[0128] [Table 3]

[0129] ICP Results Comparative Example 1 Example 1 Example 2 Comparative Example 2 Example 3 Nb [ppm] - 12,000 11,230 11,120 8,900 V [ppm] - 5,400 8,600 11,200 - Zr [ppm] - - - - 5,700

[0130] As can be seen from Table 3, it was found that the cathode active materials of Examples 1 to 3 contain niobium (Nb) at a concentration of 11,000 ppm to 12,000 ppm.

[0131] In addition, it was found that the cathode active materials of Examples 1 and 2 contain niobium (Nb) at a concentration of 11,000 ppm to 12,000 ppm and vanadium (V) at a concentration of 5,400 ppm to 8,600 ppm.

[0132] In addition, it was found that the cathode active material of Example 3 contains niobium (Nb) at a concentration of 11,000 ppm to 12,000 ppm and zirconium (Zr) at a concentration of 5,400 ppm to 8,600 ppm.

[0133] Test Example 6 - Battery capacity and coulombic efficiency analysis

[0134] Measure the battery capacity and Coulombic efficiency of the all-solid-state batteries of Examples 1 to 3 and Comparative Examples 1 and 2. Specifically, for evaluating the initial formation, the all-solid-state battery was paused for 4 hours, charged at a constant current (CC) mode at 0.05C up to 4.3V, and then charged at a constant voltage (CV) mode up to a current corresponding to 0.025C. Then, it was discharged at a CC mode at 0.05C down to 2.5V. The results are shown in Figure 12 and Table 4 below.

[0135] [Table 4]

[0136] Classification Initial Formation Capacity [mAh / g] Initial Coulombic Efficiency [%] Comparative Example 1 171 75.8 Example 1 182 80.9 Example 2 178 79.4 Comparative Example 2 169 74.5 Example 3 182 80.7

[0137] Referring to this, compared with Comparative Example 1 and Comparative Example 2, Examples 1 and 2 showed high capacity and initial Coulombic efficiency. In the case of Comparative Example 2, a large amount of vanadium (V) was used and served as a resistance in the battery, thus reducing the battery capacity and initial Coulombic efficiency.

[0138] Meanwhile, from the results of Example 3, it can be found that when zirconium (Zr) is added in an appropriate amount, an all-solid-state battery with high capacity and initial Coulombic efficiency can be obtained.

[0139] Based on the above results, it can be confirmed that when niobium (Nb) and vanadium (V) or zirconium (Zr) are present in an appropriate amount on the surface and inside of the active material particles, the performance of the all-solid-state battery is increased by reducing the battery resistance and improving the lithium-ion conductivity.

[0140] Test Example 7 - SEM Analysis of the Cross-Section of the Cathode Layer

[0141] SEM analysis was performed on the cross-section of the cathode layer of the all-solid-state battery of Example 1. The results are shown in Figure 13 . Additionally, EDS analysis was performed on the cross-section of the cathode layer. The results are shown in Figure 14 . As shown in Figure 13 and 14 , the active material particles are surrounded by niobium (Nb) and vanadium (V).

[0142] Additionally, Figure 15 shows the EDS spectral results of the cross-section of the cathode layer. From this, it can be confirmed that niobium (Nb) and vanadium (V) are present inside the electrode layer.

[0143] Although the specific forms of the present disclosure have been described with reference to the accompanying drawings, those skilled in the art will understand that the present disclosure can be embodied in other specific forms without changing its technical spirit or basic characteristics. Therefore, the above various forms should be understood as being non-limiting and illustrative in various ways.

Claims

1. A cathode active material for a all-solid-state battery, the cathode active material comprising: Active material particles; and A coating that covers at least a portion of the surface of the active material particles and contains lithium (Li), niobium (Nb), and at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, Wherein the active material particles contain a compound represented by the following Chemical Formula 1: [Chemical Formula 1] Li x A y Nb w Ni 1-a-b Co a M b O2, Among them, In Chemical Formula 1, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, M is at least one element selected from manganese (Mn), aluminum (Al), magnesium (Mg), and combinations thereof, and x, y, w, a, and b are 0.98 ≤ x ≤ 1.02, 0 ≤ y ≤ 0.01, 0 ≤ w ≤ 0.8, 0 < a ≤ 0.1, and 0 ≤ b ≤ 0.1, respectively, Wherein the coating contains lithium oxide represented by the following Chemical Formula 2: [Chemical Formula 2] LiNb c A d O 3， Wherein in Chemical Formula 2, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, and c and d are 0 < c ≤ 0.8 and 0 < d ≤ 0.01, respectively, and Wherein the vanadium (V) is contained at a concentration of 5,400 ppm to 8,600 ppm.

2. The cathode active material according to claim 1, wherein the niobium (Nb) is contained at a concentration of 11,000 ppm to 12,000 ppm.

3. The cathode active material according to claim 1, wherein the zirconium (Zr) is contained at a concentration of 5,400 ppm to 8,600 ppm.

4. A method for manufacturing a cathode active material for a all-solid-state battery, the method comprising: Preparing a mixture comprising a precursor of active material particles, a lithium (Li) precursor, a niobium (Nb) precursor, and at least one element selected from a vanadium (V) precursor, a zirconium (Zr) precursor, and combinations thereof; Stirring the mixture; and Calcining the mixture after stirring, Wherein the cathode active material comprises active material particles and a coating that covers at least a portion of the surface of the active material particles and contains lithium (Li), niobium (Nb), and at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, Wherein the active material particles contain a compound represented by the following Chemical Formula 1: [Chemical Formula 1] Li x A y Nb w Ni 1-a-b Co a M b O2, Wherein, in Chemical Formula 1, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, M is at least one element selected from manganese (Mn), aluminum (Al), magnesium (Mg), and combinations thereof, and x, y, w, a, and b are 0.98 ≤ x ≤ 1.02, 0 ≤ y ≤ 0.01, 0 ≤ w ≤ 0.8, 0 < a ≤ 0.1, and 0 ≤ b ≤ 0.1, respectively, Wherein the coating contains lithium oxide represented by the following Chemical Formula 2: [Chemical Formula 2] LiNb c A d O 3， Wherein in Chemical Formula 2, A is at least one element selected from vanadium (V), zirconium (Zr), and combinations thereof, and c and d are 0 < c ≤ 0.8 and 0 < d ≤ 0.01, respectively, and Wherein the vanadium (V) is contained at a concentration of 5,400 ppm to 8,600 ppm.

5. The method according to claim 4, wherein preparing the mixture comprises: adding a solvent to a lithium (Li) precursor and at least one substance selected from a vanadium (V) precursor, a zirconium (Zr) precursor, and combinations thereof and mixing; adding the resultant mixture to a niobium (Nb) precursor and mixing; and adding the resultant mixture to an active material particle precursor.

6. The method according to claim 4, wherein the active material particle precursor, the lithium (Li) precursor, and the zirconium (Zr) precursor are in a powder phase, and the niobium (Nb) precursor and the vanadium (V) precursor are in a liquid phase.

7. The method according to claim 4, further comprising drying after stirring the mixture.

8. The method according to claim 4, wherein the stirred mixture is calcined in an oxygen atmosphere at a temperature of 300 °C to 800 °C for 1 hour to 5 hours.

9. The method according to claim 4, wherein the niobium (Nb) is included at a concentration of 11,000 ppm to 12,000 ppm.

10. The method according to claim 4, wherein the zirconium (Zr) is included at a concentration of 5,400 ppm to 8,600 ppm.

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