Metal oxide precursor and preparation method and application thereof

Abstract

The invention relates to a metal oxide precursor and a preparation method and application thereof. The metal oxide precursor is of a single-crystal structure and has N groups of three-level ratio particle distribution, any group of three-level ratio sequentially comprises first-level particles, second-level particles and third-level particles according to particle size decreasing arrangement, and the volume accumulation rate of the metal oxide precursor is eta gt; x1i, X2i and X3i are the particle sizes of the first-stage particles, the second-stage particles and the third-stage particles respectively, and the unit of the X1i, the unit of the X2i and the unit of the X3i are all microns; h is the side length of the stacking volume, and the unit is [mu] m; n is the number of particles contained in a single side of the accumulation volume, and ni = h / X1i; a is equal to 0.56812, b is equal to-1.777, c is equal to 31.029, and d is equal to-0.0289; epsilon is an error coefficient, and 0.99 < = epsilon < = 1.01. The metal oxide precursor provided by the invention has multi-stage proportion particle distribution, meets a specific volume accumulation rate, and can reach a high tap density of 1.3 g / cm < 3 > to 3.4 g / cm < 3 >.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a metal oxide precursor, a preparation method thereof, and an application thereof. Background Art

[0002] Spray pyrolysis is a rapid multiphase reaction process. During the pyrolysis process, the rapid evaporation of the solvent and the crystallization and thermal cracking of the solute occur simultaneously, resulting in a relatively loose structure of the generated product and a low tap density.

[0003] The particle size distribution of the precursor products traditionally used for preparing cathode materials is usually a relatively narrow unimodal distribution with uniform particle size, or a bimodal distribution with a two-stage particle size ratio. Although the volume packing ratio of the particles with a two-stage ratio is improved to a certain extent compared with the particles with a uniform particle size, there are still large voids during the packing process, resulting in a tap density that is still difficult to meet the higher requirements. Summary of the Invention

[0004] Based on this, in view of the above problems, it is necessary to provide a metal oxide precursor, a preparation method thereof, and an application thereof; the metal oxide precursor not only has a multi-stage ratio particle distribution, but also meets a specific volume packing ratio, enabling it to reach a high tap density of 1.3 g / cm 3 to 3.4 g / cm 3 . When used for preparing the cathode material of a battery, it can achieve excellent initial discharge specific capacity and cycle stability, and reduce the production cost.

[0005] A metal oxide precursor, the metal oxide precursor has a single crystal structure, the metal oxide precursor has N groups of three-stage ratio particle distributions, and in any group of three-stage ratios, the particles are arranged in decreasing order of particle size and include primary particles, secondary particles, and tertiary particles in sequence. The volume packing ratio η of the metal oxide precursor is:

[0006]

[0007] wherein, in any group of three-stage ratios, X 1i , X 2i , X 3i are the particle sizes of the primary particles, secondary particles, and tertiary particles respectively, and the units of X 1i , X 2i , X 3i are all μm;

[0008] h is the side length of the packing volume, and the unit is μm;

[0009] n is the number of particles accommodated on one side of the packing volume, and n i = h / X 1i ;

[0010] a = 0.56812, b = -1.777, c = 31.029, d = -0.0289;

[0011] ε is the error coefficient, and 0.99 ≤ ε ≤ 1.01;

[0012] N is an integer and N ≥ 1;

[0013] η > 54%.

[0014] In one embodiment, 1.2μm ≤ X 1i ≤ 24.2μm;

[0015] and / or, X 2i = 0.414X 1i ;

[0016] and / or, X 3i = 0.156X 1i .

[0017] In one embodiment, 0.5μm ≤ X 2i ≤ 10μm;

[0018] and / or, 0.19μm ≤ X 3i ≤ 3.7μm.

[0019] In one embodiment, 54.80% ≤ η ≤ 57.17%.

[0020] In one embodiment, the primary particles, secondary particles, and tertiary particles in the metal oxide precursor are each independently selected from single crystal primary particles or secondary particles formed by aggregation of multiple single crystal primary particles.

[0021] In one embodiment, the particle size of the single crystal primary particles is from 0.1μm to 1.5μm.

[0022] In one embodiment, the particle size distribution curve of the metal oxide precursor is a unimodal normal distribution, and K 90 is from 2 to 5.

[0023] In one embodiment, the tap density of the metal oxide precursor is from 1.3 g / cm 3 to 3.4 g / cm 3 .

[0024] In one embodiment, the D 50 of the metal oxide precursor is from 0.5μm to 10μm;

[0025] and / or, the D minis from 0.18 μm to 3.8 μm;

[0026] and / or, the D of the metal oxide precursor max is from 1.2 μm to 24.2 μm.

[0027] In one embodiment, the chemical general formula of the metal oxide precursor is Mn a M 1-a O2, where M is at least one of Ni, Fe, Cu, Zn, and 0.1 ≤ a ≤ 0.9.

[0028] A preparation method of the metal oxide precursor as described above, the preparation method is selected from spray pyrolysis.

[0029] In one embodiment, the pyrolysis temperature is from 410 °C to 990 °C;

[0030] and / or, the atomization pressure is from 0.4 MPa to 0.6 MPa;

[0031] and / or, the particle size of the atomized droplets is from 100 μm to 1000 μm.

[0032] A positive electrode material prepared from the metal oxide precursor as described above.

[0033] 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, the positive electrode material layer includes the positive electrode material as described above.

[0034] A secondary battery, including the positive electrode sheet as described above.

[0035] The metal oxide precursor of the present invention not only has a particle distribution with a variety of ternary ratio combinations, making the particle size distribution curve show a wide single-peak normal distribution, but also can achieve a close-packed effect during stacking, meeting a specific volume packing ratio, enabling it to reach a high tap density of 1.3 g / cm 3 to 3.4 g / cm 3 . Therefore, when the metal oxide precursor is used to prepare a positive electrode material, a large loading amount in the crucible can be achieved. On the one hand, the energy density of the sintered positive electrode material can be increased, thereby improving the electrochemical performance; on the other hand, the energy consumption can be reduced, thereby reducing the production cost.

[0036] Therefore, using the positive electrode material prepared from the metal oxide precursor of the present invention in a battery significantly improves the initial discharge specific capacity and cycle stability, and has great market application potential. Brief Description of the Drawings

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 Particle size distribution curve of the metal oxide precursor prepared in Example 1;

[0039] Figure 2 Scanning electron micrograph of the metal oxide precursor prepared in Example 1 under 30K magnification;

[0040] Figure 3 Particle size distribution curve of the metal oxide precursor prepared in Comparative Example 1;

[0041] Figure 4 Scanning electron micrograph of the metal oxide precursor prepared in Comparative Example 1 under 30K magnification;

[0042] Figure 5 Scanning electron micrograph of the positive electrode material prepared in Example 1 under 30K magnification;

[0043] Figure 6 Scanning electron micrograph of the positive electrode material prepared in Comparative Example 1 under 30K magnification;

[0044] Figure 7 Charge-discharge performance test chart of the positive electrode materials prepared in Example 1 to Example 7 and Comparative Example 1. Among them, a to g are the charge-discharge performance curves of the positive electrode materials prepared in Example 1 to Example 7 in sequence, and h is the charge-discharge performance curve of the positive electrode material prepared in Comparative Example 1;

[0045] Figure 8 Cycle performance test chart of the positive electrode materials prepared in Example 1 and Comparative Example 1. Among them, a is the cycle performance curve of the positive electrode material prepared in Example 1, and b is the cycle performance curve of the positive electrode material prepared in Comparative Example 1. Detailed implementation manners

[0046] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments or examples only, and are not intended to limit the present invention. The optional range of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, and the any and all combinations include combinations of any two related listed items, any more related listed items, or all related listed items.

[0048] The present invention provides a metal oxide precursor, the metal oxide precursor is a single crystal structure, the metal oxide precursor has a particle distribution with N sets of three - level ratios, and in any set of three - level ratios, in order of decreasing particle size, it includes primary particles, secondary particles, and tertiary particles. The volume packing ratio η of the metal oxide precursor is:

[0049]

[0050] wherein, in any set of three - level ratios, X 1i 、X 2i 、X 3i are the particle diameters of the primary particles, secondary particles, and tertiary particles respectively, and the units of X 1i 、X 2i 、X 3i are all μm;

[0051] h is the side length of the packing volume, and the unit is μm;

[0052] n is the number of particles accommodated in one side of the packing volume, and n i = h / X 1i ;

[0053] a = 0.56812, b = - 1.777, c = 31.029, d = - 0.0289;

[0054] ε is the error coefficient, and 0.99 ≤ ε ≤ 1.01;

[0055] N is an integer and N ≥ 1;

[0056] η > 54%.

[0057] It should be noted that the packing volume model adopted in the present invention is a cube, h is the side length of the cube volume formed by the metal oxide precursor, and n is the number of particles accommodated in one side of the cube volume formed by the metal oxide precursor.

[0058] The metal oxide precursor described in the present invention not only has a particle size distribution with a variety of ternary ratio combinations, making the particle size distribution curve exhibit a wide single-peak normal distribution, but also can achieve a close-packed effect during stacking, meeting a specific volume packing rate, so that it can reach a high tap density of 1.3 g / cm 3 to 3.4 g / cm 3 of the high tap density.

[0059] It can be understood that the particle sizes corresponding to D 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D max in the metal oxide precursor can all be used as the particle sizes of the primary particles in the ternary ratio, and the present invention does not limit this. Among them, D 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 refer to the particle sizes corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor particles reaches 30%, 40%, 50%, 60%, 70%, 80%, 90% respectively, and D max refers to the maximum particle size of the metal oxide precursor particles.

[0060] In one embodiment, 1.2 μm ≤ X 1i ≤ 24.2 μm.

[0061] In another embodiment, the primary particles and the secondary particles preferably satisfy a specific proportional relationship: X 2i = 0.414X 1i , and further, based on 1.2 μm ≤ X 1i ≤ 24.2 μm, preferably 0.5 μm ≤ X 2i ≤ 10 μm.

[0062] In another embodiment, the primary particles and the tertiary particles preferably satisfy a specific proportional relationship: X 3i = 0.156X 1i , and further, based on 1.2 μm ≤ X 1i ≤ 24.2 μm, preferably 0.19 μm ≤ X 3i ≤ 3.7 μm.

[0063] In one embodiment, based on the above X 1i 、X 2i 、X 3iThe preferred particle size range, the volume packing ratio of the metal oxide precursor is preferably 54.80% ≤ η ≤ 57.17%, more preferably 55% ≤ η ≤ 57.17%, which is more conducive to achieving the effect of high tap density.

[0064] In one embodiment, the primary particles, secondary particles, and tertiary particles in the metal oxide precursor are each independently selected from single crystal primary particles or secondary particles formed by aggregation of a plurality of single crystal primary particles.

[0065] Among them, the particle size of the single crystal primary particles is preferably 0.1 μm to 1.5 μm.

[0066] In one embodiment, the particle size distribution curve of the metal oxide precursor is a single-peak normal distribution, and K 90 is 2 to 5. A metal oxide precursor that satisfies a wide single-peak normal distribution is more conducive to achieving the effect of high tap density.

[0067] In one embodiment, the tap density of the metal oxide precursor is 1.3 g / cm 3 to 3.4 g / cm 3 .

[0068] In one embodiment, the D 50 of the metal oxide precursor is 0.5 μm to 10 μm;

[0069] And / or, the D min of the metal oxide precursor is 0.18 μm to 3.8 μm;

[0070] And / or, the D max of the metal oxide precursor is 1.2 μm to 24.2 μm.

[0071] It should be noted that D 50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor particles reaches 50%, and can be used to represent the average particle size; D min refers to the minimum particle size of the metal oxide precursor particles; D max refers to the maximum particle size of the metal oxide precursor particles. D max can include both the particle size of the single crystal primary particles and the particle size of the secondary particles formed by aggregation of a plurality of single crystal primary particles. The present invention does not make any limitations in this regard.

[0072] In one embodiment, the chemical general formula of the metal oxide precursor is Mn a M 1-aO2, where M is at least one of Ni, Fe, Cu, and Zn, and 0.1 ≤ a ≤ 0.9. It is understandable that the metal oxide precursor described in the present invention can be a binary metal oxide, a ternary metal oxide, or a quaternary metal oxide, and the present invention does not limit this.

[0073] Compared with the co-precipitation precursor product, in the metal oxide precursor described in the present invention, the metal content is higher (≥71%), while the metal content of the co-precipitation precursor product is only about 62%. Moreover, the metal oxide precursor described in the present invention has good air stability, is easy to store and transport, and does not require heating for dehydration during the processing, which is beneficial to reducing the processing cost.

[0074] The present invention provides a method for preparing the metal oxide precursor as described above, and the preparation method is selected from spray pyrolysis.

[0075] It should be noted that the specific operation of spray pyrolysis can refer to the existing methods, and the present invention will not elaborate on this.

[0076] In one embodiment, the pyrolysis temperature is 410°C to 990°C;

[0077] and / or, the atomization pressure is 0.4 MPa to 0.6 MPa;

[0078] and / or, the particle size of the atomized droplets is 100 μm to 1000 μm.

[0079] By adjusting the temperature, atomization pressure, and particle size of the atomized droplets of spray pyrolysis, it is beneficial to control the crystal grain size distribution of the metal oxide precursor, so that the metal oxide precursor has a more excellent combination of particle distributions with multiple tertiary ratios, and further meets a specific volume packing ratio, which is more conducive to achieving the effect of high tap density.

[0080] It should be noted that the pyrolysis temperature is the working temperature of the spray pyrolysis furnace. The preparation method preferably satisfies the above conditions such as pyrolysis temperature, atomization pressure, and particle size of the atomized droplets. It is understandable that other preparation methods that do not meet the above conditions of pyrolysis temperature, atomization pressure, and particle size of the atomized droplets can also make the metal oxide precursor meet the specific volume packing ratio in the present invention under certain conditions, and the present invention does not limit this.

[0081] The present invention provides a cathode material prepared from the metal oxide precursor as described above.

[0082] Using the metal oxide precursor described in the present invention to prepare the cathode material can achieve a larger loading amount in the crucible. On the one hand, it can improve the energy density of the sintered cathode material, and then improve the electrochemical performance, especially the initial discharge specific capacity and cycle stability; on the other hand, it can reduce energy consumption, and then reduce the production cost.

[0083] It should be noted that the preparation method of the positive electrode material refers to the existing method, and the present invention will not elaborate on this.

[0084] The present invention also provides a positive electrode sheet and a secondary battery including the positive electrode sheet, preferably a sodium ion battery. The positive electrode material includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector. The positive electrode material layer includes the positive electrode material as described above.

[0085] It can be understood that the positive electrode material layer further includes a binder and a conductive agent; the sodium ion battery further includes a negative electrode sheet, a separator, and an electrolyte. Among them, the negative electrode sheet, the separator, and the electrolyte can adopt any conventional commercially available negative electrode sheet (or negative electrode material), separator, and electrolyte, and the present invention does not limit this.

[0086] Hereinafter, the metal oxide precursor, its preparation method, and application 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 invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0087] Example 1

[0088] A mixed metal salt solution was prepared by mixing nickel salt, copper salt, iron salt, and manganese salt in a molar ratio of metal atoms of 2:1:3:3. Under the atomization pressure condition of 0.5 MPa, the mixed metal salt solution was atomized to form atomized droplets with a size of about 500 μm and entered a roasting furnace. Under the pyrolysis temperature condition of 850 °C, the atomized droplets underwent processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The prepared metal oxide precursor product is simply represented as NCFM2133.

[0089] In the metal oxide precursor D 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D maxThe corresponding particle sizes are respectively used as the particle sizes of the primary particles in 8 groups of tertiary ratios. Moreover, the particle sizes of the secondary particles in these 8 groups of tertiary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume stacking rate calculation formula proposed by the present invention, and η = 56.83%.

[0090] The particle size distribution curve of the metal oxide precursor prepared in this example is as Figure 1 shown, and it can be seen that this particle size distribution curve shows a wide normal distribution.

[0091] The surface morphology of the metal oxide precursor prepared in this example is as Figure 2 shown, and it can be seen that this metal oxide precursor is a single crystal structure, showing an octahedron-like shape, and the particle distribution is relatively uniform.

[0092] Example 2

[0093] A mixed metal salt solution is prepared by mixing nickel salt, copper salt, iron salt, and manganese salt in a molar ratio of metal atoms of 5:20:10:65. Under the atomization pressure condition of 0.4 MPa, the mixed metal salt solution is atomized to form atomized droplets with a size of about 600 μm and enters a roasting furnace. Under the pyrolysis temperature condition of 920 °C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The prepared metal oxide precursor product is simply represented as NCFM5 / 20 / 10 / 65.

[0094] Regarding the D 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D max The corresponding particle sizes are respectively used as the particle sizes of the primary particles in 8 groups of tertiary ratios. Moreover, the particle sizes of the secondary particles in these 8 groups of tertiary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume stacking rate calculation formula proposed by the present invention, and η = 56.69%.

[0095] Example 3

[0096] A mixed metal salt solution is prepared by mixing nickel salt, iron salt, and manganese salt in a molar ratio of metal atoms of 4:2:4. Under the atomization pressure condition of 0.5 MPa, the mixed metal salt solution is atomized to form atomized droplets with a size of about 700 μm and enters a roasting furnace. Under the pyrolysis temperature condition of 800 °C, the atomized droplets form a metal oxide precursor through processes such as evaporation, drying, thermal decomposition, and sintering molding. The prepared metal oxide precursor product is simply represented as NFM424.

[0097] The D in this metal oxide precursor 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D max The corresponding particle sizes are respectively used as the particle sizes of the primary particles in 8 groups of tertiary ratios. And the particle sizes of the secondary particles in these 8 groups of tertiary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume packing ratio calculation formula proposed by the present invention, and η = 56.12%.

[0098] Example 4

[0099] A mixed metal salt solution is prepared by mixing nickel salt, iron salt, and manganese salt in a molar ratio of metal atoms of 33:33:33. Under the atomization pressure condition of 0.6 MPa, the mixed metal salt solution is atomized to form atomized droplets with a size of about 100 μm and enters a roasting furnace. Under the pyrolysis temperature condition of 750 °C, the atomized droplets form a metal oxide precursor through processes such as evaporation, drying, thermal decomposition, and sintering molding. The prepared metal oxide precursor product is simply represented as NFM111.

[0100] The D in this metal oxide precursor 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D maxThe corresponding particle sizes are respectively used as the particle sizes of the primary particles in 8 groups of tertiary ratios. Moreover, the particle sizes of the secondary particles in these 8 groups of tertiary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume packing ratio calculation formula proposed by the present invention, and η = 55.82%.

[0101] Example 5

[0102] A mixed metal salt solution is prepared by mixing iron salt and manganese salt in a molar ratio of metal atoms of 35:65. Under the atomization pressure condition of 0.6 MPa, the mixed metal salt solution is atomized to form atomized droplets with a size of about 400 μm and enters a roasting furnace. Under the pyrolysis temperature condition of 650 °C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The prepared metal oxide precursor product is simply represented as FM3565.

[0103] Regarding the D in this metal oxide precursor 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D max The corresponding particle sizes are respectively used as the particle sizes of the primary particles in 8 groups of tertiary ratios. Moreover, the particle sizes of the secondary particles in these 8 groups of tertiary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume packing ratio calculation formula proposed by the present invention, and η = 55.12%.

[0104] Example 6

[0105] A mixed metal salt solution is prepared by mixing copper salt, iron salt, and manganese salt in a molar ratio of metal atoms of 2:3:5. Under the atomization pressure condition of 0.5 MPa, the mixed metal salt solution is atomized to form atomized droplets with a size of about 800 μm and enters a roasting furnace. Under the pyrolysis temperature condition of 410 °C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The prepared metal oxide precursor product is simply represented as CFM235.

[0106] Regarding the D in this metal oxide precursor 40 、D 60 、D 80 、D maxThe corresponding particle sizes are respectively used as the particle sizes of the primary particles in 4 groups of ternary ratios. Moreover, the particle sizes of the secondary particles in these 4 groups of ternary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume stacking rate calculation formula proposed by the present invention, and η = 56.49%.

[0107] Example 7

[0108] A mixed metal salt solution is prepared by mixing nickel salt, zinc salt, iron salt, and manganese salt in a molar ratio of metal atoms of 2:1:3:3. Under the atomization pressure condition of 0.6 MPa, the mixed metal salt solution is atomized to form atomized droplets with a size of about 1000 μm and enters a roasting furnace. Under the pyrolysis temperature condition of 990 °C, the atomized droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The prepared metal oxide precursor product is simply represented as NZFM2133.

[0109] Regarding the D in this metal oxide precursor max The corresponding particle sizes are respectively used as the particle sizes of the primary particles in 1 group of ternary ratios. Moreover, the particle sizes of the secondary particles in this 1 group of ternary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this example satisfies the volume stacking rate calculation formula proposed by the present invention, and η = 56.34%.

[0110] Comparative Example 1

[0111] The difference between Comparative Example 1 and Example 1 is that the spray pyrolysis temperature is 700 °C, the atomization pressure is 0.3 MPa, and the size of the atomized droplets is about 300 μm.

[0112] Regarding the D in this metal oxide precursor 30 、D 40 、D 50 、D 60 、D 70 、D 80 、D 90 、D maxThe corresponding particle sizes are respectively used as the particle sizes of the primary particles in 8 groups of ternary ratios. Moreover, the particle sizes of the secondary particles in these 8 groups of ternary ratios are all 0.414 times the particle sizes of the corresponding primary particles, and the particle sizes of the tertiary particles are all 0.156 times the particle sizes of the corresponding primary particles. When the stacking volume is a cube with a side length h = 100 μm, through simulation calculation, it can be known that the metal oxide precursor prepared in this comparative example satisfies the volume packing rate calculation formula proposed by the present invention, and η = 53.9%.

[0113] The particle size distribution curve of the metal oxide precursor prepared in this comparative example is as Figure 3 shown. It can be seen that the particle size distribution shows a multi-peak structure and the particle size is very uneven.

[0114] The surface morphology of the metal oxide precursor prepared in this comparative example is as Figure 4 shown. It can be seen that the particle size of the metal oxide precursor is generally small as a whole, but there are also extremely large structures, resulting in uneven overall distribution and serious agglomeration phenomena. Such an uneven agglomerated structure will lead to uneven sintering of the cathode material, making the composition and structure of the cathode material non-uniform.

[0115] The particle sizes, tapped densities, specific surface areas and other parameters of the metal hydroxide precursors prepared in Test Examples 1 to 7 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] Application Example

[0120] The metal hydroxide precursors prepared in Examples 1 to 7 and Comparative Example 1 were mixed with sodium carbonate at a molar ratio of 1:1, and then placed in a muffle furnace. Under an air atmosphere, the temperature was raised to 900 °C at a heating rate of 5 °C / min, and after holding for 15 h, it was naturally cooled, crushed and sieved to obtain the cathode material.

[0121] The surface morphology of the cathode material prepared in Example 1 is as Figure 5 shown. It can be seen that the cathode material is a hexagonal prism structure with uniform size and smooth surface, indicating no surface residual alkali.

[0122] The surface morphology of the cathode material prepared in Comparative Example 1 is as Figure 6 shown. It can be seen that the morphology and size of the cathode material are very uneven, the hexagonal prism structure is not obvious, and there is a large amount of surface residual alkali on the particle surface, which will make the surface of the material unstable, thus affecting the cycle performance and safety of the battery.

[0123] The cathode materials prepared in Examples 1 to 7 and Comparative Example 1 were made into sodium-ion button batteries, and the initial discharge specific capacity and the capacity retention rate after 25 cycles were tested under the voltage condition of 2V - 4.15V. The test results are as Figure 7 , Figure 8 and shown in Table 2.

[0124] Table 2

[0125]

[0126] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0127] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it cannot be understood as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A metal oxide precursor, characterized in that, The metal oxide precursor is in a single crystal structure, and the metal oxide precursor has a particle distribution with N sets of ternary ratios. In any one of the ternary ratios, the particles are arranged in decreasing order of particle size and include primary particles, secondary particles, and tertiary particles in sequence. The volume packing ratio η of the metal oxide precursor is: Among them, in any set of tertiary ratios, X 1i , X 2i , X 3i are the particle sizes of the primary particles, secondary particles, and tertiary particles respectively, and the units of X 1i , X 2i , X 3i are all μm; h is the side length of the packing volume, with the unit of μm; n is the number of particles accommodated on one side of the stacking volume, and n i = h / X 1i ; a = 0.56812, b = -1.777, c = 31.029, d = -0.0289; ε is the error coefficient, and 0.99 ≤ ε ≤ 1.01; N is an integer and N ≥ 1; η > 54%.

2. The metal oxide precursor according to claim 1, characterized in that, 1.2μm ≤ X 1i ≤ 24.2μm; and / or, X 2i = 0.414X 1i ; and / or, X 3i = 0.156X 1i .

3. The metal oxide precursor according to claim 2, wherein, 0.5μm ≤ X 2i ≤ 10μm; and / or, 0.19μm ≤ X 3i ≤ 3.7μm.

4. The metal oxide precursor according to any one of claims 1 to 3, characterized in that, 54.80% ≤ η ≤ 57.17%.

5. The metal oxide precursor according to claim 1, characterized in that, The primary particles, secondary particles, and tertiary particles in the metal oxide precursor are independently selected from single crystal primary particles or secondary particles formed by aggregation of multiple single crystal primary particles.

6. The metal oxide precursor according to claim 5, characterized in that, The particle size of the single crystal primary particles is from 0.1 μm to 1.5 μm.

7. The metal oxide precursor according to claim 1, wherein The particle size distribution curve of the metal oxide precursor is a single-peak normal distribution, and K 90 is from 2 to 5.

8. The metal oxide precursor according to claim 1, wherein The tapped density of the metal oxide precursor is 1.3 g / cm 3 to 3.4 g / cm 3 .

9. The metal oxide precursor according to claim 1, wherein The D of the metal oxide precursor 50 is from 0.5 μm to 10 μm; And / or, D of the metal oxide precursor min is from 0.18 μm to 3.8 μm; and / or, D of the metal oxide precursor max is from 1.2 μm to 24.2 μm.

10. The metal oxide precursor according to claim 1, characterized in that, The chemical general formula of the metal oxide precursor is Mn a M 1-a O2, where M is at least one of Ni, Fe, Cu, and Zn, and 0.1 ≤ a ≤ 0.

9.

11. A method for preparing a metal oxide precursor as described in any one of claims 1 to 10, characterized in that, The preparation method is selected from spray pyrolysis.

12. The method for preparing a metal oxide precursor according to claim 11, wherein The pyrolysis temperature is from 410 °C to 990 °C; and / or, the atomization pressure is from 0.4 MPa to 0.6 MPa; and / or, the particle size of the atomized droplets is from 100 μm to 1000 μm.

13. A positive electrode material prepared from the metal oxide precursor according to any one of claims 1 to 10.

14. A positive electrode sheet, characterized in that, It includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector. The positive electrode material layer includes the positive electrode material according to claim 13.

15. A secondary battery, characterized in that, It includes the positive electrode sheet according to claim 14.

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