Metal oxide precursor, and preparation method therefor and use thereof

Abstract

A metal oxide precursor, and a preparation method therefor and the use thereof. The metal oxide precursor is of a single-crystal structure, the flow coefficient of the metal oxide precursor is 50-95%, and the volume proportion of particles with a particle size of 0.3 μm or less in the metal oxide precursor is smaller than or equal to 1%, wherein the flow coefficient is the percentage of the volume of the single-crystal particles of the metal oxide precursor to the volume of circumcircles of the single-crystal particles of the metal oxide precursor. The metal oxide precursor has a sphere-like structure and a low micropowder proportion, which not only improves the fluidity, but can also effectively ameliorate the problems of agglomeration and bridging, thereby improving the apparent density and facilitating the improvement of the electrical properties and safety of a battery.

Description

Metal oxide precursor, preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410719244.9, filed on June 04, 2024 in the China Patent Office and entitled "Metal oxide precursor, preparation method and application thereof", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of battery, in particular to a metal oxide precursor, a preparation method and application thereof. BACKGROUND

[0003] The statements herein are provided only to enhance understanding of the present application and are not necessarily intended to constitute the prior art.

[0004] The oxide precursor prepared by the traditional spray method usually has the particle morphology of spinel-like octahedral structure, and the characteristics of high amount of fine powder. However, the oxide precursor based on the characteristics has a low loose bulk density, which is not conducive to improving the electrode capacity and energy density, and will lead to low coating density and uneven coating, thereby affecting the charge-discharge performance and cycle stability of the battery. In addition, the thermal stability of the oxide precursor is poor, and the excessive amount of fine powder may cause overheating or thermal runaway under high temperature or large current, which has a safety hazard.

[0005] SUMMARY

[0006] The purpose of the embodiments of the present application is to provide a metal oxide precursor, a preparation method and application thereof. The metal oxide precursor has a spherical structure and a low fine powder rate, which not only improves the flowability, but also effectively improves the agglomeration and bridging problems, thereby improving the loose bulk density and being conducive to improving the electrical performance and safety of the battery.

[0007] The technical solution adopted by the embodiments of the present application is as follows:

[0008] In a first aspect, a metal oxide precursor is provided. The metal oxide precursor is a single crystal structure. The flow coefficient of the metal oxide precursor is 50%-95%, and the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is less than or equal to 1%. The flow coefficient is the percentage of the volume of the single crystal particles of the metal oxide precursor to the volume of the circumscribed circle of the single crystal particles of the metal oxide precursor.

[0009] In one of the embodiments, the flow coefficient of the metal oxide precursor is 60%-95%.

[0010] In one embodiment, the bridging rate η of the metal oxide precursor is ≤1.36%, wherein η=(1-ρ1 / ρ2)×100%, ρ1 is the actual loose bulk density of the metal oxide precursor, and ρ2 is the theoretical loose bulk density of the metal oxide precursor.

[0011] In one embodiment, the tap density of the metal oxide precursor is 1.0 g / cm 3 -3.0 g / cm 3 .

[0012] In one embodiment, the specific surface area of the metal oxide precursor is 3 m 2 / g-10 m 2 / g.

[0013] In one embodiment, the particle size distribution of the metal oxide precursor satisfies at least one of the following conditions:

[0014] (1) D min is 0.2 μm-0.4 μm;

[0015] (2) D3 is 0.2 μm-0.6 μm;

[0016] (3) D 50 is 1.5 μm-3.5 μm;

[0017] (4) D 90 is 5 μm-10 μm;

[0018] (5) K 90 is 1.5-4.

[0019] In one embodiment, the metal oxide precursor has a chemical formula of Mn a M 1-a O2, wherein 0.1≤a≤0.9, and M is selected from at least one of Ni, Fe, Co, Cu, and Zn.

[0020] In a second aspect, a preparation method of a metal oxide precursor is provided, and the preparation method is selected from a spray pyrolysis method, and the spray pyrolysis method has a pyrolysis temperature of 450-950°C.

[0021] In a third aspect, a positive electrode material is provided, and the positive electrode material is prepared from the metal oxide precursor as above.

[0022] In a fourth aspect, a positive electrode sheet is provided, and the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, and the positive electrode material layer includes the positive electrode material as above.

[0023] In a fifth aspect, a secondary battery is provided, and the secondary battery includes the positive electrode sheet as above.

[0024] The metal oxide precursor provided by the embodiments of the present application has the following beneficial effects:

[0025] The embodiments of the present application adopt the volume percentage of the metal oxide precursor single crystal particles to the volume of the circumscribed circle of the metal oxide precursor single crystal particles to define the flow coefficient of the metal oxide precursor, which is used to evaluate the flowability of the metal oxide precursor. When the flow coefficient of the metal oxide precursor is 50%-95%, the metal oxide precursor has a spherical structure, the flowability of the metal oxide precursor particles is better than that of the traditional spinel-like octahedral structure, and the metal oxide precursor also has a powder content of less than 1%, which effectively improves the problems of agglomeration and bridging, further promotes the flow and close arrangement of the metal oxide precursor particles, and is beneficial to reducing the voids and improving the loose bulk density of the metal oxide precursor particles.

[0026] Therefore, the metal oxide precursor provided by the embodiments of the present application is used to prepare the positive electrode material, which not only can realize high density distribution and uniformity of the prepared positive electrode material in the electrode coating process, but also is beneficial to increasing the electrochemical reaction area, thereby improving the capacity, charge-discharge performance and cycle stability of the battery, improving the electrical conductivity and reaction rate, and reducing the safety risk. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0028] FIG. 1 is a scanning electron microscope image of the metal oxide precursor prepared in Example 1 of the present application;

[0029] FIG. 2 is a particle size distribution curve of the metal oxide precursor prepared in Example 1 of the present application;

[0030] FIG. 3 is a scanning electron microscope image of the metal oxide precursor prepared in Example 2 of the present application;

[0031] FIG. 4 is a scanning electron microscope image of the metal oxide precursor prepared in Example 3 of the present application;

[0032] FIG. 5 is a high-magnification scanning electron microscope image of the single crystal particles in the metal oxide precursor prepared in Example 3 of the present application;

[0033] FIG. 6 is a scanning electron microscope image of the metal oxide precursor prepared in Comparative Example 1 of the present application;

[0034] Figure 7 is a scanning electron microscope image of the metal oxide precursor prepared in Comparative Example 2 of the present application. Embodiments of the present application

[0035] For the purposes of this application, the following description will be made in more detail. However, it should be understood that the present application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, the purpose of providing these embodiments or examples is to make the disclosure of the present application more thorough and comprehensive.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the present application. As used herein, the term "and / or" is an optional range that includes any one of two or more associated listed items, as well as any and all combinations of the associated listed items, including any two of the associated listed items, any more of the associated listed items, or all of the associated listed items.

[0037] The present application provides a metal oxide precursor, the metal oxide precursor is a single crystal structure, the flow coefficient of the metal oxide precursor is 50%-95%, and the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is less than or equal to 1%.

[0038] The flow coefficient is the percentage of the volume of the single crystal particle of the metal oxide precursor to the volume of the circumscribed circle of the single crystal particle of the metal oxide precursor. For example, when the volume of the single crystal particle of the metal oxide precursor is V1 and the volume of the circumscribed circle corresponding to the diameter of the single crystal particle of the metal oxide precursor is V2, the flow coefficient of the regular octahedral metal oxide precursor single crystal particle is (V1 / V2) x 100%. The volume V1 of the single crystal particle of the metal oxide precursor can be calculated from the crystal edge length measured by SEM characterization, and the crystal edge length measured by SEM characterization can also be converted into the radius of the circumscribed circle, so as to calculate the volume V2 of the circumscribed circle.

[0039] The volume percentage of the volume of the metal oxide precursor single crystal particles to the volume of the circumscribed circle of the metal oxide precursor single crystal particles is used to define the flow coefficient of the metal oxide precursor, which is used to evaluate the flowability of the metal oxide precursor. When the flow coefficient of the metal oxide precursor is 50%-95%, the metal oxide precursor has a quasi-spherical structure, the flowability of the metal oxide precursor particles is better than that of the traditional spinel-like octahedral structure, and the metal oxide precursor also has a fines content of 1% or less, which effectively improves the agglomeration and bridging problems, further promotes the flow and close arrangement of the metal oxide precursor particles, and is beneficial to reducing the voids and improving the bulk density of the metal oxide precursor particles.

[0040] It can be understood that the volume of the circumscribed circle of the metal oxide precursor single crystal particles is the spherical volume corresponding to the diameter of the metal oxide precursor single crystal particles. When the metal oxide precursor single crystal particles are closer to a spherical shape, the ratio of the volume of the metal oxide precursor single crystal particles to the volume of the circumscribed circle of the metal oxide precursor single crystal particles is closer to 1.

[0041] Based on this, the tendency of mutual sliding between powder particles is defined as the flow coefficient, and the flow coefficient of the metal oxide precursor includes but is not limited to any one value or a range value between any two values of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, preferably 60%-95%, and more preferably 80%-95%.

[0042] The particles with a particle size of 0.3 μm or less are defined as fines, and the volume percentage of all particles with a size of 0.3 μm or less in the metal oxide precursor represents the fines content. The higher the fines content, the more ultrafine particles in the metal oxide precursor, and the smaller the overall particles, which are prone to agglomeration and bridging, which is not conducive to the flow and close arrangement of the particles, resulting in an increase in voids in the metal oxide precursor.

[0043] It is considered that when the particle is too small, the powder has a large surface energy, in order to reduce the system energy, the small particles will tend to adhere to the surface of other particles, form large agglomeration to reduce the surface energy, thereby causing the bridging phenomenon, and due to the bridging, a certain blockage rate is generated, which hinders the particle flow, causes a large number of voids in the process of particle falling and stacking, and then reduces the bulk density. The self-defined formula η=(1-ρ1 / ρ2)×100% is used to evaluate the bridging degree of the metal oxide precursor, wherein ρ1 is the actual bulk density of the metal oxide precursor, and ρ2 is the theoretical bulk density of the metal oxide precursor. When the bridging rate η of the metal oxide precursor is less than or equal to 1.36%, the ratio ρ1 / ρ2 of the actual bulk density of the metal oxide precursor to the theoretical bulk density of the metal oxide precursor is close to 1, that is, the actual bulk density of the metal oxide precursor is closer to the theoretical bulk density of the metal oxide precursor, which indicates that the degree of bridging between the fine powder particles in the metal oxide precursor is low.

[0044] It should be noted that the theoretical bulk density ρ2 of the metal oxide precursor is 0.61 g / cm 3 -2.03 g / cm 3 , the actual bulk density of the metal oxide precursor is greater than or equal to 0.6 g / cm 3 , including but not limited to any one value or a range value between any two of 0.5 g / cm 3 , 0.6 g / cm 3 , 0.7 g / cm 3 , 0.8 g / cm 3 , 0.9 g / cm 3 , 1.0 g / cm 3 , 1.2 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.8 g / cm 3 , 2.0 g / cm 3 , preferably 1.0 g / cm 3 -1.8 g / cm 3 .

[0045] In an embodiment, the tap density of the metal oxide precursor is 1.0 g / cm 3 -3.0 g / cm 3 , including but not limited to any one value or a range value between any two of 1.0 g / cm 3 , 1.2 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.8 g / cm 3 , 2.0 g / cm3 2.2 g / cm 3 2.4 g / cm 3 2.5 g / cm 3 2.6 g / cm 3 2.8 g / cm 3 3.0 g / cm 3 , preferably 1.5 g / cm 3 2.8 g / cm 3 , which is conducive to further improving the capacity and energy density of the electrode.

[0046] In an embodiment, the specific surface area of the metal oxide precursor is 3 m 2 / g-10 m 2 / g, including but not limited to 3 m 2 / g, 3.5 m 2 / g, 4 m 2 / g, 4.5 m 2 / g, 5 m 2 / g, 5.5 m 2 / g, 6 m 2 / g, 6.5 m 2 / g, 7 m 2 / g, 7.5 m 2 / g, 8 m 2 / g, 8.5 m 2 / g, 9 m 2 / g, 9.5 m 2 / g, 10 m 2 / g, preferably 5.5 m 2 / g-8.0 m 2 / g, which is conducive to providing sufficient reactive sites, promoting the rapid diffusion of ions, and at the same time helping to reduce side reactions occurring during the charging and discharging of the battery, thereby improving the cycle stability of the battery.

[0047] In an embodiment, the particle size distribution of the metal oxide precursor satisfies at least one of the following conditions:

[0048] (1) D min is 0.2 μm-0.4 μm;

[0049] (2) D3 is 0.2 μm-0.6 μm;

[0050] (3) D 50 is 1.5 μm-3.5 μm;

[0051] (4) D 90 is 5 μm-10 μm;

[0052] (5) K 90 is 1.5-4.

[0053] Preferably, the metal oxide precursor satisfies D min is 0.2 μm-0.4 μm, D3 is 0.2 μm-0.6 μm, D 50 is 1.5 μm-3.5 μm, D 90 is 5 μm-10 μm, K 90 is 1.5-4, the metal oxide precursor finishing particle size is small and the particle size distribution is wide, which not only avoids the problem of high porosity caused by large particle accumulation, but also is beneficial to further reduce the bridging degree.

[0054] It should be noted that D min represents the minimum particle size, D3 represents the particle size corresponding to the cumulative particle size distribution percentage of 3%, D 50 represents the particle size corresponding to the cumulative particle size distribution percentage of 50%, D 90 represents the particle size corresponding to the cumulative particle size distribution percentage of 90%, K 90 represents the width of the particle size distribution, K 90 =(D 90 -D 10 ) / D 50 .

[0055] In an embodiment, the chemical formula of the metal oxide precursor is represented as Mn a M 1-a O2, wherein 0.1≤a≤0.9, and M is selected from at least one of Ni, Fe, Co, Cu and Zn. It can be understood that the metal oxide precursor of the present application can be a binary metal oxide, a ternary metal oxide or a quaternary metal oxide, which is not limited in the present application.

[0056] The present application provides a preparation method of the above metal oxide precursor, and the preparation method is selected from a spray pyrolysis method, and the pyrolysis temperature in the spray pyrolysis method is 450-950°C.

[0057] It should be noted that the specific operation of the spray pyrolysis method can refer to the existing method, which will not be repeated here.

[0058] In one embodiment, the pyrolysis temperature in the spray pyrolysis method includes, but is not limited to, any one value of 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or a range value between any two of them. By adjusting the temperature of the spray pyrolysis, the morphology of the metal oxide precursor can be further regulated, which is beneficial to the formation of a spherical structure of the metal oxide precursor, thereby improving the flowability of the metal oxide precursor and effectively improving the problems of agglomeration and bridging.

[0059] It should be noted that the pyrolysis temperature is the working temperature of the pyrolysis device.

[0060] The application provides a positive electrode material prepared from the metal oxide precursor as described above.

[0061] The use of the metal oxide precursor of the application in the preparation of the positive electrode material not only enables the prepared positive electrode material to achieve a higher density distribution and uniformity in the electrode coating process, but also is beneficial to increasing the electrochemical reaction area, thereby improving the capacity, charge-discharge performance and cycle stability of the battery, improving the electrical conductivity and reaction rate, and reducing the safety risk.

[0062] It should be noted that the preparation method of the positive electrode material refers to the existing method, and the application will not be described here.

[0063] The application also provides a positive electrode sheet and a secondary battery, preferably a sodium ion battery, comprising the positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, and the positive electrode material layer comprises the positive electrode material as described above.

[0064] In one embodiment, the positive electrode current collector can be a metal foil or a composite current collector. For example, an aluminum foil is used as the metal foil. The composite current collector can be formed by forming a metal material on a polymer material substrate, wherein the metal material includes, but is not limited to, at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, and 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).

[0065] It can be understood that the positive electrode material layer also includes a binder and a conductive agent. The binder can be any commercially available binder for a positive electrode sheet, including but not limited to at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-fluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin, or any prior art binder, and the present application does not make any limitation. The conductive agent can be any commercially available conductive agent for a sodium ion battery, such as carbon black, graphite, etc.

[0066] Hereinafter, the metal oxide precursor, the preparation method and the application thereof will be further described through the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained by purchase.

[0067] Example 1

[0068] The nickel salt, the iron salt, and the manganese salt are prepared into a mixed metal salt solution in a proportion of 4:2:4 of the metal atom molar ratio. The mixed metal salt solution is first atomized, and then pyrolyzed at 500°C for 30 min to obtain a metal oxide precursor. The metal oxide precursor product is represented by the simple formula NFM424.

[0069] The surface morphology of the metal oxide precursor prepared in this example is shown in FIG. 1. It can be seen that the metal oxide precursor is a single crystal structure in a spherical shape. The particle size distribution of the metal oxide precursor is shown in FIG. 2, and the related test parameters are shown in Tables 1 and 2. It can be seen that the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is 0.9%, the flow coefficient is 35%, and the bridging rate η is 0.9%. It is indicated that the metal oxide precursor can basically avoid the bridging phenomenon and basically has no impact on the bulk density of the product.

[0070] Example 2

[0071] The nickel salt, the copper salt, the iron salt, and the manganese salt are prepared into a mixed metal salt solution in a proportion of 2:1:3:3 of the metal atom molar ratio. The mixed metal salt solution is first atomized, and then pyrolyzed at 900°C for 45 min to obtain a metal oxide precursor. The metal oxide precursor product is represented by the simple formula NCFM2133.

[0072] The surface morphology of the metal oxide precursor prepared in this example is shown in Figure 3. It can be seen that the metal oxide precursor is a single crystal structure in the form of a sphere. The relevant test parameters of the metal oxide precursor are shown in Tables 1 and 2. It can be seen that the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is 0.72%, the flow coefficient is 90%, and the bridging rate η is 0.06%. This indicates that the metal oxide precursor can basically avoid the bridging phenomenon and basically has no impact on the bulk density of the product.

[0073] Example 3

[0074] A mixed metal salt solution was prepared by mixing copper salt, iron salt and manganese salt in a metal atom molar ratio of 2:4:4. The mixed metal salt solution was first atomized, and then pyrolyzed at 700°C for 50 min to obtain a metal oxide precursor. The metal oxide precursor product is represented by the simple formula CFM244.

[0075] The surface morphology of the metal oxide precursor prepared in this example is shown in Figure 4. It can be seen that the metal oxide precursor is a single crystal structure in the form of a sphere. As an example, the electron microscope image of the product was imported into the particle size distribution calculation software to measure the edge length a of the single crystal particles. The volume corresponding to the single crystal particles can be calculated from the edge length, and the size of the single crystal particles, i.e. the diameter 2r of the circumscribed sphere, can be calculated from the edge length a. Thus, the volume of the circumscribed sphere can be calculated.

[0076] The relevant test parameters of the metal oxide precursor are shown in Tables 1 and 2. It can be seen that the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is 0.38%, the flow coefficient is 65%, and the bridging rate η is 0.2%. This indicates that the metal oxide precursor can basically avoid the bridging phenomenon and basically has no impact on the bulk density of the product.

[0077] Example 4

[0078] A mixed metal salt solution was prepared by mixing iron salt and manganese salt in a metal atom molar ratio of 30:70. The mixed metal salt solution was first atomized, and then pyrolyzed at 800°C for 35 min to obtain a metal oxide precursor. The metal oxide precursor product is represented by the simple formula FM37.

[0079] The metal oxide precursor was tested to be a single crystal structure in the form of a sphere. The relevant test parameters of the metal oxide precursor are shown in Tables 1 and 2. It can be seen that the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is 0.57%, the flow coefficient is 81%, and the bridging rate η is 0.64%. This indicates that the metal oxide precursor can basically avoid the bridging phenomenon and basically has no impact on the bulk density of the product.

[0080] Comparative Example 1

[0081] The nickel salt, the iron salt and the manganese salt were prepared into a mixed metal salt solution in a proportion of 4:2:4 of metal atom molar ratio, the mixed metal salt solution was atomized first, and then pyrolyzed at 380°C for 30 min to obtain a metal oxide precursor, and the prepared metal oxide precursor product was expressed in a simple formula as NFM424.

[0082] The surface morphology of the metal oxide precursor prepared in the present comparative example is shown in FIG. 6, and it can be seen that the metal oxide precursor is still a single crystal structure, but the particle size of the metal oxide precursor is obviously smaller compared with that of Example 1, resulting in a higher amount of fine powder. The related test parameters of the metal oxide precursor are shown in Tables 1 and 2, and it can be known that the volume fraction of the particles with a particle size of 0.3 μm or less in the metal oxide precursor is as high as 9.4%, the flow coefficient is 34%, and the bridging rate η is as high as 3.2%, indicating that the bridging phenomenon of the metal oxide precursor is more obvious compared with that of Example 1, which hinders the flow and close arrangement of the particles, resulting in an increase in voids, thereby causing a certain influence on the bulk density of the product.

[0083] Comparative Example 2

[0084] The nickel salt, the iron salt and the manganese salt were prepared into a mixed metal salt solution in a proportion of 4:2:4 of metal atom molar ratio, the mixed metal salt solution was atomized first, and then pyrolyzed at 1000°C for 30 min to obtain a metal oxide precursor, and the prepared metal oxide precursor product was expressed in a simple formula as NFM424.

[0085] The surface morphology of the metal oxide precursor prepared in the present comparative example is shown in FIG. 7, and it can be seen that the metal oxide precursor is still a single crystal structure and has a large particle size, but the morphology of the metal oxide precursor is similar to a regular octahedral structure, and the particle edges and corners are more distinct compared with those of Example 1. The related test parameters of the metal oxide precursor are shown in Tables 1 and 2, and it can be known that the volume fraction of the particles with a particle size of 0.3 μm or less in the metal oxide precursor is 3.7%, the flow coefficient is 25%, and the bridging rate η is 1.7%, thereby causing a certain influence on the bulk density of the product.

[0086] Table 1

[0087] Product model Micron powder rate (%) Flow coefficient (%) p1 / p2 p1 (g / cm3) Tap density (g / cm3) Specific surface area (m2 / g) Example 1 NFM424 0.90 500 0.99 100 0.68 1.2 3.9 Example 2 NCFM2133 0.72 900 0.99 941.6 2.6 8.8 Example 3 CFM244 0.38 650 0.99 800 0.94 2.0 7.9 Example 4 FM370 0.57 810 0.99 360 0.82 1.9 16.5 Comparative Example 1 NFM424 9.43 40 0.96 800 0.44 0.98 14.7 Comparative Example 2 NFM424 3.72 50 0.98 300 0.46 0.99 2.6

[0088] Table 2

[0089] Product model Dmin (pm) D3 (pm) D50 (pm) D90 (pm) K90 Example 1 NFM424 0.27 80 0.39 12 196 5.64 91.62 Example 2 NCFM2133 0.32 50 0.51 23 236 7.9 1.57 Example 3 CFM244 0.31 50 0.44 52 3 6.8 2.03 Example 4 FM370 0.32 50 0.32 12 978 0.1 85 Comparative Example 1 NFM424 0.15 0.17 41.3 24 2.4 Comparative Example 2 NFM424 0.43 0.81 64 11 92.3

[0090] Application Example

[0091] The metal oxide precursor prepared in Examples 1-4 and Comparative Examples 1-2 was mixed with sodium carbonate at a molar ratio of 1:1, and then placed in a muffle furnace, heated to 900°C at a temperature increase rate of 5°C / min under an air atmosphere, sintered for 15 h, and then naturally cooled, crushed and sieved to obtain a positive electrode material.

[0092] The positive electrode material prepared in Examples 1-4 and Comparative Examples 1-2 was made into a sodium ion button cell, and the discharge specific capacity was tested under a voltage condition of 2V-4.15V; the capacity retention rate of the sodium ion button cell after 50 cycles under a condition of 0.2C, the higher the capacity retention rate, the better the cycle stability of the sodium ion button cell, and the test results are shown in Table 3.

[0093] Table 3

[0094] Discharge specific capacity (mAh / g) Capacity retention rate (%) after 50 cycles Example 1 165.0 90.3% Example 2 175.3 93.6% Example 3 168.4 90.5% Example 4 170.5 91.9% Comparative Example 1 140.2 87.2% Comparative Example 2 138.7 83.3%

[0095] According to Table 3, the metal oxide precursor prepared in Examples 1-4 has a high discharge specific capacity under the voltage condition of 2V-4.15V as a positive electrode material of a sodium ion battery, and has a capacity retention rate as high as 93.6% after 50 cycles of cycle test, and has excellent cycle stability.

[0096] The phenomenon of bridging caused by agglomeration is more serious due to the high content of fine powder in Comparative Examples 1-2, resulting in low bulk density, and further affecting the tap density and the loading amount, and reducing the battery capacity; the excessively high specific surface area causes side reactions in the charging and discharging process, and reduces the cycle stability.

[0097] The technical features of the above examples can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above examples are not described, however, as long as the combinations of the technical features do not contradict, they should be considered as the scope of the description.

[0098] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A metal oxide precursor, characterized by, The metal oxide precursor is a single crystal structure, the flow coefficient of the metal oxide precursor is 50%-95%, and the volume fraction of particles with a particle size of 0.3 μm or less in the metal oxide precursor is less than or equal to 1%, wherein the flow coefficient is the percentage of the volume of the single crystal particles of the metal oxide precursor to the volume of the circumscribed circle of the single crystal particles of the metal oxide precursor.

2. The metal oxide precursor according to claim 1, characterized in that The flow coefficient of the metal oxide precursor is 60%-95%.

3. Metal oxide precursor according to claim 1 or 2, characterized in that The bridging rate η of the metal oxide precursor is ≤1.36%, wherein η=(1-ρ1 / ρ2)×100%, ρ1 is the actual loose bulk density of the metal oxide precursor, and ρ2 is the theoretical loose bulk density of the metal oxide precursor.

4. The metal oxide precursor according to claim 1 or 2, characterized in that, The tap density of the metal oxide precursor is 1.0 g / cm 3 - 3.0 g / cm 3 .

5. The metal oxide precursor according to claim 1 or 2, characterized in that, The specific surface area of the metal oxide precursor is 3 m 2 / g-10 m 2 / g.

6. The metal oxide precursor according to claim 1 or 2, characterized in that, The particle size distribution of the metal oxide precursor satisfies at least one of the following conditions: (1) D min is 0.2 μm - 0.4 μm; (2) D3 is 0.2 μm-0.6 μm; (3) D 50 is 1.5 pm - 3.5 pm; (4) D 90 is 5 μm - 10 μm; (5) K 90 is 1.5-4.

7. The metal oxide precursor according to claim 1 or 2, characterized in that, The chemical formula of the metal oxide precursor is represented as Mn a M 1-a O2, wherein 0.1≤a≤0.9, and M is selected from at least one of Ni, Fe, Co, Cu, and Zn.

8. A method for producing a metal oxide precursor according to any one of claims 1 to 7, characterized by, The preparation method is selected from a spray pyrolysis method, and the pyrolysis temperature in the spray pyrolysis method is 450°C-950°C.

9. A positive electrode material prepared from the metal oxide precursor according to any one of claims 1-7.

10. A positive electrode sheet characterized by comprising: The positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, and the positive electrode material layer comprises the positive electrode material according to claim 9.

11. A secondary battery characterized by comprising: The positive electrode sheet comprises the positive electrode sheet according to claim 10.

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