Metal oxide precursors, methods for producing the same, and applications

Abstract

This application discloses a metal oxide precursor, a method for manufacturing the same, and its applications. The metal oxide precursor has a single crystal structure. In the cumulative particle size distribution curve function f(x) of the metal oxide precursor, f(x) represents the cumulative particle size distribution, where 0 < f(x) < 100%, x represents the particle size, 0.05 μm < x < 20 μm. When f(x1) = 25% and f(x2) = 75%, there are n particle size values between x1 and x2. The average value of the tangent slopes of the corresponding point values in the cumulative particle size distribution curves of x1, x2, and the n particle size values is K', and K' > 25. Here, n > 0, the tangent slope of the point value is K, and K is the derivative of the cumulative particle size distribution curve function f(x) of the metal oxide precursor. The metal oxide precursor of this application has a single crystal structure and excellent particle size distribution uniformity, with high sintering activity and excellent uniformity, which is beneficial to improving the discharge capacity and cycle performance of the cathode material.

Description

Technical Field

[0001] Cross-reference to Related Applications This application claims the priority of a Chinese patent application filed with the China National Intellectual Property Administration on December 29, 2023, with the application number 202311873876.2 and the title of the invention "Metal Oxide Precursor and Its Manufacturing Method and Application", and all of its content is incorporated herein by reference.

[0002] This application relates to the field of battery technology, and particularly to metal oxide precursors and their manufacturing methods and applications.

Background Art

[0003] Currently, the precursors produced by the mainstream coprecipitation method are usually secondary particle aggregates, and can only sinter polycrystalline cathodes. During the charge and discharge process of polycrystalline cathode materials, alkali metal ions enter and exit, expanding and contracting single crystals, generating stress at grain boundaries, causing grain boundary fracture, and leading to a decline in cycle performance.

[0004] The single crystal structure precursors produced by the conventional spray method usually have the characteristics that the particle size of primary particles is large, the particle size is uneven, and it has an octahedral structure. However, the single crystal structure precursors based on this characteristic have the following problems: (1) they are easily crushed during the compaction process, (2) the sintering activity is reduced, the sintering time is long, and the energy consumption is high, (3) due to the uneven particle size, the sintering is uneven, and the electrochemical performance of the cathode material is not good.

Summary of the Invention

[0005] One of the purposes of the embodiments of this application is to provide a metal oxide precursor and its manufacturing method and application in order to solve the problems that it is easily crushed during the compaction process of the single crystal structure precursor, the particle size is uneven, the sintering activity is reduced, and the sintering becomes uneven.

[0006] The technical solutions adopted in the embodiments of this application are as follows.

[0007] In a first aspect, a metal oxide precursor for manufacturing a cathode material is provided. The metal oxide precursor has a single crystal structure. In the cumulative particle size distribution curve function f(x) of the metal oxide precursor, f(x) is the cumulative particle size distribution, 0 < f(x) < 100%, x is the particle size, and 0.05 μm < x < 20 μm. When f(x1) = 25% and f(x2) = 75%, there are n particle size values between x1 and x2. n is the number of particle size values between x1 and x2, n > 0. The average value of the tangent slopes of the corresponding point values on the cumulative particle size distribution curve of x1, x2, and the n particle size values is K', and K' > 25. Here, the tangent slope of the point value is K, and K is the derivative of the cumulative particle size distribution curve function f(x) of the metal oxide precursor.

[0008] In some embodiments, in the cumulative particle size distribution curve diagram of the metal oxide precursor, the abscissa is the logarithmic scale of the particle size x of the metal oxide precursor, denoted as log ,

[0011] , , , ,

[0010] (x), and the ordinate is the cumulative volume occupancy rate of the corresponding metal oxide precursor under the particle size condition of the abscissa, denoted as f(x).

[0009] In some embodiments, the calculation method of the average value K' of the tangent slopes of the corresponding point values on the cumulative particle size distribution curve of x1, x2, and the n particle size values is

Equation

[0010] In some embodiments, the angle between the line with slope K' and the x-axis is θ1, and 87.7° ≤ θ1 ≤ 90°.

[0011] In some embodiments, the angle between the straight line with a slope of K’ and the y-axis is θ2, and θ2 / 90° < 0.024.

[0012] In some embodiments, the D 50 of the metal oxide precursor is 0.5 μm - 2.5 μm.

[0013] In some embodiments, the D min of the metal oxide precursor is 0.05 μm - 0.3 μm.

[0014] In some embodiments, the D max of the metal oxide precursor is 5 μm - 20 μm.

[0015] In some embodiments, the specific surface area of the metal oxide precursor is 8 m 2 / g - 15 m 2 / g.

[0016] In some embodiments, the primary particles of the metal oxide precursor include an octahedron-like structure and / or a spherical-like structure.

[0017] In some embodiments, the particle size of the primary particles is 50 nm - 500 nm.

[0018] In some embodiments, the chemical formula of the metal oxide precursor is Mn a M 1-a O2, where 0.1 ≤ a ≤ 0.9, and M is at least one selected from Ni, Fe, Cu, and Zn.

[0019] In a second aspect, the present application provides a method for manufacturing the above metal oxide precursor selected from the spray pyrolysis method.

[0020] In some embodiments, the pyrolysis temperature of the spray pyrolysis method is 600°C to 900°C.

[0021] In some embodiments, the atomization pressure of the spray pyrolysis method is 0.4 MPa to 0.6 MPa.

[0022] In some embodiments, the air-fuel ratio for the spray pyrolysis method is 15-20.

[0023] In a third embodiment, the present application provides a metal oxide precursor manufactured by the above method or a cathode material manufactured from the above metal oxide precursor.

[0024] In a fourth embodiment, the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the positive electrode material described above.

[0025] In a fifth embodiment, the present application provides a secondary battery including the above-described positive electrode sheet.

[0026] On the one hand, the metal oxide precursor of the present invention has cumulative particle size distribution curve functions f(x1)=25% and f(x2)=75%, and the average value K'>25 of the tangent slopes of the corresponding point values ​​in the cumulative particle size distribution curve of n particle size values ​​between x1 and x2 means that the metal oxide precursor not only has a narrow normal particle size distribution but also high uniformity of particle size distribution, making it easier to insert alkali metal ions when sintering the cathode material, resulting in high sintering activity, good sintering uniformity, and making it easier to obtain a high discharge capacity in the cathode material. On the other hand, the metal oxide precursor does not have problems such as crystal grain boundaries and has a high pressure-reducing ability, which strengthens the stability of the cathode material structure produced from the metal oxide precursor, makes it less prone to fracture during the compaction process, and is advantageous for improving cycle performance. [Brief explanation of the drawing]

[0027] To more clearly explain the technical concepts in the embodiments of this application, the following drawings, which may be used to describe the embodiments or exemplary technologies, are briefly introduced below. Clearly, the drawings in the following description represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these without any creative effort. [Figure 1] Figure 1 shows the cumulative particle size distribution curve of a metal oxide precursor according to several embodiments of the present application. [Figure 2] Figure 2 is a scanning electron microscope image of the metal oxide precursor produced in Example 1 of the present invention. [Figure 3] Figure 3 shows the particle size distribution curve of the metal oxide precursor produced in Example 1 of the present invention, where A is the volume particle size distribution curve and B is the cumulative particle size distribution curve. [Figure 4] Figure 4 is a scanning electron microscope image of the cathode material manufactured in Example 1 of the present invention. [Figure 5] Figure 5 is a scanning electron microscope image of the metal oxide precursor produced in Comparative Example 1 of the present invention. [Figure 6] Figure 6 shows the particle size distribution curve of the metal oxide precursor produced in Comparative Example 1 of the present application, where A is the volume particle size distribution curve and B is the cumulative particle size distribution curve. [Figure 7] Figure 7 is a scanning electron microscope image of the cathode material manufactured in Comparative Example 1 of the present invention. [Figure 8] Figure 8 is a scanning electron microscope image of the metal oxide precursor produced in Comparative Example 3 of the present invention. [Figure 9] Figure 9 shows the particle size distribution curve of the metal oxide precursor produced in Comparative Example 3 of the present invention, where A is the volume particle size distribution curve and B is the cumulative particle size distribution curve. [Figure 10] Figure 10 is a scanning electron microscope image of the cathode material manufactured in Comparative Example 3 of the present invention. [Figure 11]Figure 11 shows the charge-discharge performance test curves of the positive electrode materials manufactured in Example 1 and Comparative Examples 1-3 of the present application, where A is the charge-discharge performance curve of the positive electrode material manufactured in Example 1, B is the charge-discharge performance curve of the positive electrode material manufactured in Comparative Example 1, C is the charge-discharge performance curve of the positive electrode material manufactured in Comparative Example 1, and D is the charge-discharge performance curve of the positive electrode material manufactured in Comparative Example 1. [Figure 12] Figure 12 shows cycle performance test diagrams of the cathode materials manufactured in Example 1 and Comparative Examples 1-3 of the present application, where A is the change in specific capacity of the cathode material manufactured in Example 1 at different cycle counts, B is the change in specific capacity of the cathode material manufactured in Comparative Example 1 at different cycle counts, C is the change in specific capacity of the cathode material manufactured in Comparative Example 1 at different cycle counts, and D is the change in specific capacity of the cathode material manufactured in Comparative Example 1 at different cycle counts. [Modes for carrying out the invention]

[0028] To further clarify the purpose, technical solutions, and advantages of this application, the application will be described in more detail below with reference to the drawings and embodiments. The specific embodiments described herein are for interpretation purposes only and do not limit the application.

[0029] Furthermore, when a component is referred to as being "fixed" or "attached" to another component, it may be attached to the other component directly or indirectly. When one component is referred to as being "connected" to another component, it may be connected to the other component directly or indirectly. The directions or positional relationships indicated by terms such as "up," "down," "left," and "right" are based on the directions or positional relationships shown in the drawings and are merely for the purpose of facilitating explanation. They do not indicate or imply that the specified device or element has a specific direction or must be configured and operated in a specific direction, and therefore cannot be understood as limiting this application. A person skilled in the art can understand the specific meaning of the above terms depending on the specific situation. The terms "first" and "second" are merely for the purpose of facilitating explanation and do not indicate or imply relative importance or implicitly indicate the number of technical features. "Multiple" means two or more unless otherwise specified.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art relating to the embodiments of this application. Terms used in the description of the embodiments of this application are solely for the purpose of describing specific embodiments or examples and are not intended to limit the embodiments of this application. The selectable range of the term "and / or" as used herein includes any one of two or more related column items, and any and all combinations of related column items, including any two or all combinations of any two related column items, any more related column items, or any combination of all related column items.

[0031] To illustrate the technical solution described in this application, a detailed explanation follows with reference to specific drawings and embodiments.

[0032] Some embodiments of the present application provide a metal oxide precursor, the metal oxide precursor has a single crystal structure, in the cumulative particle size distribution curve function f(x) of the metal oxide precursor, f(x) is the cumulative particle size distribution, 0 < f(x) < 100%, x is the particle size, and 0.05 μm < x < 20 μm.

[0033] Referring to the cumulative particle size distribution curve diagram of the metal oxide precursor in one embodiment shown in FIG. 1, taking FIG. 1 as an example, the abscissa in the cumulative particle size distribution curve function f(x) represents the size of the particle size. However, since the particle size distribution range is large, if the original particle size is directly used as the abscissa, the curve will be too concentrated. Therefore, a logarithmic scale (log 10 ) is used. If the particle size is d, in the logarithmic scale, the particle size is displayed as log 10 (d), the ordinate represents the cumulative volume occupancy corresponding to the particle size of the abscissa, and is denoted as f(x). In the normal linear coordinates, the distance of the particle size values on the abscissa is too far. In the logarithmic coordinates, the distances of these points are evenly distributed in the logarithmic coordinates, reducing the difference within the large numerical range and enabling better observation of the details within different order ranges. As can be seen from FIG. 1, the larger the abscissa log 10 (d) (that is, the larger the x particle size), the cumulative volume occupancy f(x) first shows a tendency to grow and then stabilize. This is because in the embodiments of the present application, the cumulative volume distribution reflects the total occupancy of all particles from the minimum size to the current size. When the particle size is small, the proportion of the total volume of small particles is small, so the growth of the cumulative distribution is slow. When the particle size increases, the presence of large particles increases the cumulative volume distribution. In particular, in the "middle stage" of the particle distribution, since there are many of these particles, the growth of the cumulative volume distribution is fast. After reaching a certain particle size value, the growth slows down because at this time, the volume ratio including large particle size particles is already high, and the proportion of these large particle size particles in the material does not increase significantly, resulting in a slowdown in growth.

[0034] When f(x1)=25% and f(x2)=75%, there are n particle size values ​​between x1 and x2, where n>0. The tangent slope of the corresponding point values ​​in the cumulative particle size distribution curve for x1, x2, and the n particle size values ​​is K, where K is the derivative of the cumulative particle size distribution curve function f(x) of the metal oxide precursor. That is, the tangent slopes of the corresponding point values ​​in the cumulative particle size distribution curve for x1 and x2 are K1 and K2, respectively, and the tangent slopes of the corresponding point values ​​in the cumulative particle size distribution curve for the n particle size values ​​are K n And K1, K2, K n The particle sizes are x1, x2, and x in that order. n The cumulative particle size distribution curve functions f(x1), f(x2), f(x) of the metal oxide precursor are as follows: n This is the derivative of ). Therefore, the mean value

number

[0035] The metal oxide precursor of the present invention has a cumulative particle size distribution curve function f(x1)=25% and f(x2)=75%. The average value K'>25 of the tangent slopes of the corresponding point values ​​in the cumulative particle size distribution curve for n particle size values ​​between x1 and x2 indicates that the metal oxide precursor not only has a narrow normal particle size distribution but also high uniformity of particle size distribution, making it easier to insert alkali metal ions when sintering the cathode material, resulting in high sintering activity, good sintering uniformity, and easier acquisition of a high discharge capacity in the cathode material. The cumulative particle size distribution curve function of the embodiment of the present invention ranges from f(x1)=25% to f(x2)=75%, meaning that the particle size is D 25 ~D 75 Corresponding to the interval, D in the sample 50 Including particles with a median diameter, and excluding the influence of abnormally large or abnormally small extreme particles, the interval where f(x) is between 25% and 75% reflects both the central tendency and the degree of variance in the distribution, thus exhibiting good representativeness.

[0036] On the other hand, metal oxide precursors that satisfy the above conditions are single-crystal particles, with consistent grain orientation, no grain boundaries within them, fewer defects during the growth process, less likelihood of cracks and micro-defects occurring under pressure, and improved overall strength and compressive resistance of the material. In polycrystalline materials, different grain orientations result in non-uniform responses in the direction of force application, avoiding the problem of stress concentration at grain boundaries and cracking. In the embodiments of this application, since the metal oxide precursor does not have problems such as grain boundaries and has high compressive resistance, the stability of the cathode material structure produced from the metal oxide precursor can be made stronger, making it less prone to fracture during the consolidation process and advantageous for improving cycle performance. Furthermore, the metal oxide precursor has good structural integrity and facilitates the production of cathode materials with a single-crystal structure.

[0037] For example, the value of x may be any typical and non-limiting point value or an interval value between any two points, such as 0.05 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.

[0038] In some embodiments, as shown in Figure 1, the angle between the line with slope K' and the x-axis is θ1, where 87.7° ≤ θ1 ≤ 90°, K' and θ1 are positively correlated, and the larger the value of θ1, the steeper the line with slope K', i.e., the larger K', the higher the uniformity of the particle size distribution of the metal oxide precursor. Exemplarily, the angle θ1 between the line with slope K' and the x-axis may be any typical but non-limiting point value or an interval value between any two points, such as 87.7°, 88°, 88.5°, 89°, 89.5°, or 90°.

[0039] In some embodiments, the angle between the line with slope K' and the y-axis is θ2, where θ2 / 90° < 0.024, θ1 + θ2 = 90°, and θ2 / 90° = (90° - θ1) / 90°. Therefore, (90° - θ1) / 90° represents the particle uniformity μ of the metal oxide precursor, i.e., μ < 0.024. The closer the μ value is to 0, the more uniform the particle size of the metal oxide precursor. Exemplarily, the angle between the line with slope K' and the y-axis is θ2, and θ2 / 90° may be any typical but non-limiting point value or an interval value between any two point values, such as 0.023 μm, 0.022 μm, 0.02 μm, 0.018 μm, 0.015 μm, 0.012 μm, 0.01 μm, 0.005 μm, etc.

[0040] In some embodiments, the metal oxide precursor D 50 The range is 0.5 μm - 2.5 μm, and may, for example, be any typical but non-restrictive point value or an interval value between any two point values, such as 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, etc. D 50 This is also called the middle diameter.

[0041] In some embodiments, the metal oxide precursor D min This ranges from 0.05 μm to 0.3 μm, and may, for example, be any typical but non-restrictive point value or an interval value between any two point values, such as 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, etc. D min This indicates the minimum particle diameter in the particle ensemble.

[0042] In some embodiments, the metal oxide precursor D max The range is 5 μm-20 μm, and may, for example, be any typical but non-restrictive point value or an interval value between any two point values, such as 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc. D max This represents the largest particle diameter in the particle ensemble.

[0043] In some embodiments, the specific surface area of ​​the metal oxide precursor is 8 m². 2 / g-15m2 / g, and exemplarily, 8m 2 / g, 9m 2 / g, 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 This may be a typical but non-restrictive arbitrary point value such as / g, or an interval value between any two points.

[0044] The above embodiment of the present application is D 50 , D min , D max By limiting the specific surface area, the metal oxide precursor satisfies a specific narrow normal particle size distribution and high uniformity of particle size distribution, while also having a small particle size and high specific surface area, which is advantageous for improving sintering activity, significantly shortening manufacturing time, and reducing energy consumption for manufacturing cathode materials.

[0045] In some embodiments, the primary particles of the metal oxide precursor include a suboctahedral structure and / or a subglobular structure. In some embodiments, the particle size of the primary particles is 50 nm–500 nm, and may, exemplary, be any typical but non-limiting point value or an interval value between any two point values, such as 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, and 500 nm. Compared to conventional fully grown spinel structures, the metal oxide precursors of the present invention require less energy for the production of the cathode material, are lower in cost, and the small particles with high uniformity of distribution are advantageous for improving sintering activity as sodium ions are more easily inserted during sintering.

[0046] In some embodiments, the general chemical formula of the metal oxide precursor is Mn a M 1-aRepresented as O2, where 0.1 ≤ a ≤ 0.9, and M is at least one selected from Ni, Fe, Cu, and Zn. The metal oxide precursor of this application may be a binary, ternary, or quaternary metal oxide, and it should be understood that this application is not limited to these. Exemplarily, a may be any typical but non-limiting point value or an interval value between any two point values, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9.

[0047] This application provides a method for producing the above-mentioned metal oxide precursor selected from a spray pyrolysis method.

[0048] The specific procedures for the spray pyrolysis method can be found in conventional methods, and therefore, a detailed explanation is omitted in this application.

[0049] In some embodiments, the pyrolysis temperature of the spray pyrolysis method is 600°C–900°C, and may, exemplary, be any typical but non-limiting point value or an interval value between any two points, such as 600°C, 700°C, 800°C, and 900°C.

[0050] In some embodiments, the atomization pressure of the spray pyrolysis method is 0.4 MPa–0.6 MPa, and may, exemplary, be any typical but non-limiting point value or an interval value between any two point values, such as 0.4 MPa, 0.5 MPa, or 0.6 MPa.

[0051] In some embodiments, the air-fuel ratio in the spray pyrolysis method is 15 to 20, and may, exemplary, be any typical but non-limiting point value or an interval value between any two point values, such as 15, 16, 17, 18, 19, and 20. Here, the air-fuel ratio is the mass ratio of air to fuel in the gas mixture.

[0052] By adjusting conditions such as the temperature, atomization pressure, and air-fuel ratio of the spray pyrolysis, it is advantageous to improve the particle size distribution effect of the manufactured metal oxide precursor, resulting in a metal oxide precursor that possesses characteristics such as a single crystal structure, excellent particle size distribution uniformity, and good structural integrity.

[0053] This application further provides a cathode material manufactured from the above-mentioned metal oxide precursor.

[0054] By using the metal oxide precursor of this invention in the manufacture of cathode materials, single-crystal cathode materials with excellent uniformity can be obtained more easily, which is advantageous for improving the discharge capacity and cycle performance of cathode materials.

[0055] Regarding the manufacturing method of the positive electrode material, conventional methods can be referred to, and a detailed explanation is omitted in this application.

[0056] The present invention further provides a secondary battery comprising a positive electrode sheet and a positive electrode material, which may specifically be a sodium-ion battery, wherein the positive electrode material comprises a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, and the positive electrode material layer comprises the above-mentioned positive electrode material.

[0057] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil, and the composite current collector may be formed by forming a metal material on a polymer material substrate. The metal material includes, but is not limited to, at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate includes, but is not limited to, at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0058] The positive electrode material layer further comprises a binder and a conductive agent, where the binder may be any commercially available binder used for positive electrode sheets, and includes, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternpolymer, vinylidene fluoride-fluoropropylene-tetrafluoroethylene ternpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic acid ester resin, and may include at least one of these, or a binder manufactured by any known method, and in the embodiments of this application, this is not limited thereto. The conductive agent may be any commercially available conductive agent used in sodium-ion batteries, such as carbon black or graphite.

[0059] The metal oxide precursors, their manufacturing methods, and applications will be further explained below with reference to specific examples. However, as will be understandable to those skilled in the art, the following examples are merely illustrative and not intended to limit the scope of the present invention. Unless otherwise specified in the examples, the methods were carried out under normal conditions or conditions suggested by the manufacturer. Unless otherwise specified, the reagents or equipment used are all commonly available products.

[0060] Example 1 Nickel salt, iron salt, and manganese salt are mixed into a metal salt solution with a metal atom molar ratio of 4:4:2. Next, the mixed metal salt solution is placed in a firing furnace in the form of atomized droplets under an atomization pressure of 0.4 MPa. Under conditions of an air combustion ratio of 15 in the firing furnace and a thermal decomposition temperature of 600°C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The general formula of the manufactured metal oxide precursor product is represented as NFM442.

[0061] The surface morphology of the metal oxide precursor produced in this embodiment is shown in Figure 2. The metal oxide precursor has a single-crystal structure, and its morphology is an octahedral structure with several small, approximately spherical structures. Detection revealed that the D of the metal oxide precursormin It is approximately 0.07 μm, D 50 It is approximately 0.54 μm, D max The thickness is approximately 6.7 μm, and the specific surface area is approximately 13.7 m². 2 The density was / g, and the primary particle size was approximately 50nm-300nm.

[0062] As shown in Figure 3, the volume particle size distribution curve and cumulative particle size distribution curve of the metal oxide precursor produced in this embodiment indicate that the metal oxide precursor has an extremely narrow particle size distribution, and the slope of the cumulative distribution curve is steep, indicating that the particle size of the product is uniform. Calculations show that the K' of the metal oxide precursor is 26.1, θ1 is 87.8°, and μ is 0.024, indicating that the particle size distribution of the metal oxide precursor is sufficiently uniform.

[0063] In this embodiment, the metal oxide precursor produced and sodium carbonate were mixed in a molar ratio of 1:1, then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min under an air atmosphere. After constant temperature sintering for 15 hours, the mixture was allowed to cool naturally, then pulverized and sieved to obtain the cathode material, whose chemical formula is Na(Ni 0.4 Fe 0.4 Mn 0.2 )O2. As shown in Figure 4, the surface morphology of the positive electrode material manufactured in this embodiment indicates that the positive electrode material has a uniform hexagonal prism structure, a smooth surface, and no residual alkali on the surface.

[0064] Example 2 Nickel salt, copper salt, iron salt, and manganese salt are prepared as a mixed metal salt solution with a metal atom molar ratio of 24:5:36:35. Next, the mixed metal salt solution is placed in a firing furnace in the form of atomized droplets under an atomization pressure of 0.5 MPa. Under conditions of an air combustion ratio of 18 in the firing furnace and a thermal decomposition temperature of 800°C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The general formula of the manufactured metal oxide precursor product is represented as NCFM24 / 5 / 36 / 35.

[0065] Detection revealed the D of the metal oxide precursor. min It is approximately 0.2 μm, D 50It is approximately 1.53 μm, D max The thickness is approximately 17.4 μm, and the specific surface area is approximately 9.48 m². 2 The density was / g, and the primary particle size was approximately 60nm-400nm.

[0066] Calculations show that the K' of the metal oxide precursor is 30, θ1 is 88.1°, and μ is 0.021, indicating that the particle size distribution of the metal oxide precursor is sufficiently uniform.

[0067] In this example, the metal oxide precursor produced and sodium carbonate were mixed in a 1:1 molar ratio, then placed in a muffle furnace, heated to 900°C at a heating rate of 5°C / min under an air atmosphere, and sintered at constant temperature for 15 hours. After natural cooling, the material was pulverized and sieved to obtain the cathode material, whose chemical formula is Na(Ni 0.24 Cu 0.05 Fe 0.36 Mn 0.35 It is O2.

[0068] Example 3 A mixed metal salt solution is prepared by combining copper salt, iron salt, and manganese salt in a metal atom molar ratio of 2:3:5. Next, the mixed metal salt solution is placed in a firing furnace in the form of atomized droplets under an atomization pressure of 0.6 MPa. Under conditions of an air combustion ratio of 20 in the firing furnace and a thermal decomposition temperature of 900°C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The general formula of the produced metal oxide precursor product is represented as CFM235.

[0069] Detection revealed the D of the metal oxide precursor. min It is approximately 0.27 μm, D 50 It is approximately 2.39 μm, D max The thickness is approximately 19.6 μm, and the specific surface area is approximately 8.9 m². 2 The density was / g, and the primary particle size was approximately 65nm-450nm.

[0070] Calculations show that the K' of the metal oxide precursor is 52, θ1 is 88.9°, and μ is 0.012, indicating that the particle size distribution of the metal oxide precursor is sufficiently uniform.

[0071] In this example, the metal oxide precursor produced and sodium carbonate were mixed in a 1:1 molar ratio, then placed in a muffle furnace, heated to 900°C at a heating rate of 5°C / min under an air atmosphere, and sintered at constant temperature for 15 hours. After natural cooling, the material was pulverized and sieved to obtain the cathode material, whose chemical formula is Na(Cu 0.2 Fe 0.3 Mn 0.5 It is O2.

[0072] Comparative Example 1 Nickel salt, iron salt, and manganese salt are mixed into a metal salt solution with a metal atom molar ratio of 4:4:2. The mixed metal salt solution is then placed in a firing furnace in the form of atomized droplets under an atomization pressure of 0.7 MPa. Under conditions of an air combustion ratio of 23 in the firing furnace and a thermal decomposition temperature of 950°C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The general formula of the produced metal oxide precursor product is represented as NFM442.

[0073] The surface morphology of the metal oxide precursor produced in this comparative example is shown in Figure 5. The metal oxide precursor still has a single-crystal structure, and its morphology is approximately octahedral, but it can be seen that the particle size is sufficiently non-uniform. Detection revealed that the D of the metal oxide precursor min It is approximately 0.32 μm, D 50 It is approximately 5.1 μm, D max The surface area is approximately 30.58 μm and the specific surface area is approximately 5.32 m². 2 The density was / g, and the primary particle size was approximately 600nm-1200nm.

[0074] As shown in Figure 6, the volume particle size distribution curve and cumulative particle size distribution curve of the metal oxide precursor produced in this comparative example show that the volume particle size distribution curve of the metal oxide precursor exhibits a bimodal distribution, the particle size distribution curve is broad, and the slope of the cumulative distribution curve is small, indicating poor particle size uniformity. By calculation, the K' of the metal oxide precursor is 13.7, θ1 is 85.8°, and μ is 0.046.

[0075] In this comparative example, the metal oxide precursor produced was mixed with sodium carbonate in a 1:1 molar ratio, then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min under an air atmosphere. After constant temperature sintering for 15 hours, it was allowed to cool naturally, then pulverized and sieved to obtain the cathode material, whose chemical formula is Na(Ni 0.4 Fe 0.4 Mn 0.2 )O2. The surface morphology of the positive electrode material manufactured in this comparative example is shown in Figure 7. The positive electrode material exhibits a hexagonal prism structure, and the surface roughness of the particles indicates a large amount of residual alkali on the surface, which destabilizes the surface of the positive electrode material and adversely affects the battery's cycle life and safety.

[0076] Comparative Example 2 Nickel salt, iron salt, and manganese salt are mixed into a metal salt solution with a metal atom molar ratio of 4:4:2. The mixed metal salt solution is then placed in a firing furnace in the form of atomized droplets under an atomization pressure of 0.3 MPa. Under conditions of an air combustion ratio of 13 in the firing furnace and a thermal decomposition temperature of 550°C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The general formula of the produced metal oxide precursor product is represented as NFM442.

[0077] Detection revealed that the metal oxide precursor still has a single-crystal structure, but the particles are smaller, the growth is incomplete, it is partially octahedral, partially amorphous particles undergo severe aggregation, and the size is sufficiently non-uniform, and the D of the metal oxide precursor min It is approximately 0.03 μm, D 50 It is approximately 0.49 μm, D max The surface area is approximately 4.65 μm and the specific surface area is approximately 18.93 m². 2 The result was found to be / g, and the primary particle size was determined to be approximately 20nm-200nm.

[0078] Calculations show that the K' of the metal oxide precursor is 12, θ1 is 85.2°, and μ is 0.053.

[0079] In this comparative example, the metal oxide precursor produced was mixed with sodium carbonate in a 1:1 molar ratio, then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min under an air atmosphere. After constant temperature sintering for 15 hours, it was allowed to cool naturally, then pulverized and sieved to obtain the cathode material, whose chemical formula is Na(Ni 0.4 Fe 0.4 Mn 0.2 It is O2.

[0080] Comparative Example 3 Nickel salt, iron salt, and manganese salt were prepared as metal salt solutions with a total molar concentration of 2 mol / L in a metal atom molar ratio of 4:4:2. Sodium hydroxide solution and aqueous ammonia solution were added to the reaction vessel as a precipitating agent and complexing agent, respectively. Nitrogen gas was introduced as a protective gas, and the coprecipitation reaction was carried out for 15 hours at a constant temperature of 55°C, with the pH value controlled to 11 and the stirring speed set to 500 r / min. After centrifugal washing and drying, a metal hydroxide precursor was obtained.

[0081] The surface morphology of the metal hydroxide precursor produced in this comparative example is shown in Figure 8. The metal hydroxide precursor has a polycrystalline structure, and the secondary particles formed by the aggregation of primary particles have a substantially spherical structure, and the particle size is sufficiently non-uniform. Detection revealed that the D of the metal hydroxide precursor min It is approximately 0.51 μm, D 50 It is approximately 5.3 μm, D max The thickness is approximately 11.94 μm, and the specific surface area is approximately 6.5 m². 2 It was / g.

[0082] Figure 9 shows the volume particle size distribution curve and cumulative particle size distribution curve of the metal hydroxide precursor produced in this comparative example. Calculations show that the K' of the metal hydroxide precursor is 16.4, θ1 is 86.5°, and μ is 0.038.

[0083] In this comparative example, the metal hydroxide precursor and sodium carbonate were mixed in a 1:1 molar ratio, then placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min under an air atmosphere. After constant temperature sintering for 15 hours, the mixture was allowed to cool naturally, then pulverized and sieved to obtain the cathode material, whose chemical formula is Na(Ni 0.4 Fe0.4 Mn 0.2 )O2. The surface morphology of the positive electrode material obtained in this comparative example is shown in Figure 10.

[0084] The positive electrode materials produced in Examples 1-3 and Comparative Examples 1-3 were used to manufacture sodium-ion coin batteries. The initial discharge ratio capacity and capacity retention rate after 50 cycles were measured under voltage conditions of 2V-4.15V, and the measurement results are shown in Figures 11, 12, and Table 1. [Table 1]

[0085] As can be seen from Figures 11 and 12 and Table 1, the cathode materials manufactured in Examples 1-3 had high initial discharge ratio capacity under voltage conditions of 2V-4.15V, reaching a maximum of approximately 172.3mAh / g, and the capacity retention rate after 50 cycles was maintained at 90% or higher in all cases, reaching a maximum of approximately 95.6%. In Comparative Examples 1-3, both the initial discharge ratio capacity and the capacity retention rate after 50 cycles were clearly lower compared to Example 1.

[0086] The technical features of the above embodiments can be combined in any way, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as these combinations of technical features are inconsistent, they should be considered to fall within the scope described herein.

[0087] The foregoing are merely selectable embodiments of the present invention and do not limit it. To those skilled in the art, the present invention is subject to various modifications and changes. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims.

Claims

1. A metal oxide precursor for manufacturing a positive electrode material, wherein the metal oxide precursor has a single crystal structure, and in the cumulative particle size distribution curve function f(x) of the metal oxide precursor, f(x) is the cumulative particle size distribution, 0 < f(x) < 100%, x is the particle size, and 0.05 μm < x < 20 μm, f(x 1 ) = 25%, f(x 2 If ) = 75%, then x 1 from x 2 There are n granularity values ​​between these points, where n is x 1 from x 2 This is the number of granularity values ​​up to x, where n > 0, and x 1 , x 2 The average of the tangent slopes of the corresponding point values ​​in the cumulative particle size distribution curve of n particle size values ​​is K', where K' > 25, where the tangent slope of the point value is K, and K is the derivative of the cumulative particle size distribution curve function f(x) of the metal oxide precursor. A metal oxide precursor characterized by the above.

2. In the cumulative particle size distribution curve diagram of the metal oxide precursor, the horizontal axis is a logarithmic scale of the particle size x of the metal oxide precursor, denoted as log 10 (x), and the vertical axis is the cumulative volume occupancy rate of the corresponding metal oxide precursor under the particle size condition of the horizontal axis, denoted as f(x). The metal oxide precursor according to claim 1, characterized in that.

3. The aforementioned x 1 , x 2 The method for calculating the average value K' of the tangent slopes of corresponding point values ​​in the cumulative particle size distribution curve of n particle size values ​​is: [Math 1] And here, K 1 , K 2 , K n The granularity is x in order. 1 , x n and x 2 The cumulative particle size distribution curve function f(x) of the metal oxide precursor is such that 1 ), f(x 2 ), f(x n The derivative of the given particle size x n The particle size x 1 and the particle size x 2 The metal oxide precursor according to claim 1, characterized in that the particle size value is between [a certain value].

4. The angle between the line with slope K' and the x-axis is θ. 1 Therefore, 87.7°≦θ 1 The metal oxide precursor according to claim 1, characterized in that it is ≤90°.

5. The angle between a line with slope K' and the y-axis is θ. 2 And θ 2 A metal oxide precursor according to claim 1 or 2, characterized in that / 90° < 0.

024.

6. D of the metal oxide precursor 50 The metal oxide precursor according to claim 1, characterized in that the particle size is 0.5 μm to 2.5 μm.

7. D of the metal oxide precursor min The metal oxide precursor according to claim 1, characterized in that the particle size is 0.05 μm to 0.3 μm.

8. D of the metal oxide precursor max The metal oxide precursor according to claim 1, characterized in that its size is 5 μm to 20 μm.

9. The specific surface area of ​​the metal oxide precursor is 8 m². 2 / g-15m 2 The metal oxide precursor according to claim 1, characterized in that it is / g.

10. The metal oxide precursor according to claim 1, wherein the primary particles of the metal oxide precursor include an octahedron-like structure and / or a spherical-like structure.

11. The metal oxide precursor according to claim 10, wherein the particle size of the primary particles is 50 nm - 500 nm.

12. The chemical formula of the aforementioned metal oxide precursor is Mn a M 1-a O 2 The metal oxide precursor according to claim 1 is characterized in that it is expressed as follows, where 0.1 ≤ a ≤ 0.9 and M is at least one selected from Ni, Fe, Cu, and Zn.

13. A method for manufacturing the metal oxide precursor according to any one of claims 1 - 12, selected from the spray pyrolysis method.

14. The method for manufacturing the metal oxide precursor according to claim 13, wherein the thermal decomposition temperature of the spray pyrolysis method is 600 °C - 900 °C.

15. The method for manufacturing the metal oxide precursor according to claim 13, wherein the atomization pressure of the spray pyrolysis method is 0.4 MPa - 0.6 MPa.

16. The method for manufacturing the metal oxide precursor according to claim 13, wherein the air-fuel ratio of the spray pyrolysis method is 15 - 20.

17. A positive electrode material, wherein the positive electrode material is manufactured from the metal oxide precursor manufactured by the method according to any one of claims 1 - 12 or the metal oxide precursor according to any one of claims 13 - 16 A positive electrode material characterized by the above.

18. A positive electrode sheet including a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, wherein the positive electrode material layer includes the positive electrode material according to claim 17 A positive electrode sheet characterized by the above.

19. A secondary battery characterized by including the positive electrode sheet according to claim 18.

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