Metal oxide precursor and preparation method therefor and use thereof

Abstract

The present application discloses a metal oxide precursor and a preparation method therefor and a use thereof. The metal oxide precursor is of a single crystal structure. The particle size distribution curve function f(x) of the metal oxide precursor represents a corresponding volume fraction at particle size x, wherein 0.214 μm≤a≤0.260 μm, 1.78 μm≤b≤3.1 μm, 8.2 μm≤c≤31.2 μm, ε, μ1 and μ2 are all error coefficients, -1.5≤ε≤1.5, -0.35≤μ1≤0.35, and -3≤μ2≤10. The metal oxide precursor in embodiments of the present application has a high tap density of 1.2 g / cm3 to 3.5 g / cm3, so that the filling rate and compaction density of a positive electrode material can be improved, and the volumetric specific capacity of a battery can be further improved.

Description

Metal Oxide Precursor, Its Preparation Method and Application

[0001] This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on December 29, 2023, with the application number 2023118679548 and the invention title "Metal Oxide Precursor, Its Preparation Method and Application", the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and particularly to a metal oxide precursor, its preparation method and application. Background Art

[0003] The statements herein only provide background information related to this application and do not necessarily constitute prior art. The metal oxide precursor prepared by traditional spray pyrolysis has relatively uniform particle size and small size, but the agglomeration phenomenon is relatively serious, resulting in a low tapped density of the metal oxide precursor. When used to prepare the cathode material, the charging amount in the container is small, which not only causes problems such as high energy consumption, but also makes the volume specific capacity of the cathode material low. In addition, under different preparation conditions, the particle size distribution curves of metal oxide precursors with different elements and ratios are inconsistent and there is no obvious rule, resulting in difficulty in improving the tapped density of the metal oxide precursor.

[0004] Application Content

[0005] One of the purposes of the embodiments of this application is to provide a metal oxide precursor, its preparation method and application, aiming to solve the problem of the low tapped density of the metal oxide precursor.

[0006] The technical solution adopted in the embodiments of this application is as follows:

[0007] In the first aspect, a metal oxide precursor is provided. The metal oxide precursor has a single crystal structure. The particle size distribution curve function f(x) of the metal oxide precursor represents the volume fraction corresponding to the particle size x and satisfies the following conditions:

[0008] (1) When a ≤ x ≤ b,

[0009] (2) When b < x ≤ c,

[0010] (3) When x c, f(x) = 0;

[0011] Among them, 0.214μm≤a≤0.260μm, 1.78μm≤b≤3.1μm, 8.2μm≤c≤31.2μm, ε, μ1, and μ2 are all error coefficients, and -1.5≤ε≤1.5, -0.35≤μ1≤0.35, and -3≤μ2≤10.

[0012] In some embodiments, the particle size distribution curve function f(x) of the metal oxide precursor presents a unimodal normal particle size distribution curve.

[0013] In some embodiments, the peak value f(x) of the particle size distribution curve function f(x) of the metal oxide precursor is max 5 to 10.

[0014] In some embodiments, the half-peak width of the particle size distribution curve function f(x) of the metal oxide precursor is 3 μm to 5 μm.

[0015] In some embodiments, the cumulative particle size distribution curve function corresponding to the particle size distribution curve function f(x) of the metal oxide precursor is D n , n% = ∑f(x), when the cumulative particle size distribution curve function is D 25 When, 0.5μm≤x≤2.0μm.

[0016] In some embodiments, the cumulative particle size distribution curve function corresponding to the particle size distribution curve function f(x) of the metal oxide precursor is D n , n% = ∑f(x), when the cumulative particle size distribution curve function is D 50 When, 1.2μm≤x≤3.8μm.

[0017] In some embodiments, the cumulative particle size distribution curve function corresponding to the particle size distribution curve function f(x) of the metal oxide precursor is D n , n% = ∑f(x), when the cumulative particle size distribution curve function is D 75 When, 2μm≤x≤5μm.

[0018] In some embodiments, in the particle size distribution curve function f(x) of the metal oxide precursor, the particle size distribution span value is 1.0 to 2.5.

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

[0020] In some embodiments, the metal oxide precursor is a cubic crystal system.

[0021] In some embodiments, the tap density of the metal oxide precursor is 1.2 g / cm 3 Up to 3.5g / cm 3 .

[0022] In a second aspect, the present application provides a method for preparing the above-mentioned metal oxide precursor, wherein the preparation method is selected from the spray pyrolysis method.

[0023] In some embodiments, the pyrolysis temperature of the spray pyrolysis method is 550°C to 950°C.

[0024] In some embodiments, the atomization pressure of the spray pyrolysis method is 0.35 MPa to 0.7 MPa.

[0025] In some embodiments, the spray pyrolysis method has a liquid inlet flow rate of 0.3m 3 / h to 0.8m 3 / h.

[0026] In a third aspect, the present application provides a positive electrode material made from the above-mentioned metal oxide precursor or the metal oxide precursor prepared by the above-mentioned method.

[0027] In a fourth aspect, the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode material layer disposed on a surface of the positive electrode current collector, wherein the positive electrode material layer comprises the above-mentioned positive electrode material.

[0028] In a fifth aspect, the present application provides a secondary battery comprising the above-mentioned positive electrode sheet.

[0029] The beneficial effects of the metal oxide precursor provided in the present application are: when the particle size distribution curve of the metal oxide precursor satisfies a specific functional relationship, it has a single-peak normal particle size distribution curve, and the particle size distribution is wide. On the one hand, the metal oxide precursor has a high tap density, which is beneficial to increase the filling amount and reduce energy consumption when used to prepare positive electrode materials. Moreover, the wide distribution particle size characteristics of the metal oxide precursor are easily inherited by the positive electrode material, so that the positive electrode material has a higher filling rate and compaction density, which is beneficial to improving the volumetric capacity of the battery; on the other hand, the metal oxide precursor that satisfies the specific particle size distribution curve functional relationship of the present application can be widely applied to different elements and proportions and preparation conditions, and can achieve a higher tap density effect.

[0030] The beneficial effects of the preparation method of the metal oxide precursor provided in the embodiment of the present application are: the above-mentioned metal oxide precursor can be prepared by spray pyrolysis, the prepared metal oxide precursor has a single crystal structure, and the particle size distribution of the single crystal structure in the precursor satisfies the above-mentioned particle size distribution curve function f(x), which is beneficial to improving the high tap density of the metal oxide precursor and can be widely applied to different elements and proportions and preparation conditions.

[0031] The beneficial effect of the positive electrode material provided in the embodiment of the present application is that when the metal oxide precursor of the embodiment of the present application is used to prepare the positive electrode material, the positive electrode material can inherit the wide distribution particle size characteristics of the metal oxide precursor, achieve a higher filling rate and compaction density, thereby improving the volumetric capacity of batteries such as sodium ion batteries.

[0032] The positive electrode sheet provided in the embodiment of the present application has the beneficial effect that the positive electrode material layer of the positive electrode sheet includes the above-mentioned positive electrode material with a high filling rate and compaction density, thereby improving the energy density, cycle stability and other electrochemical properties of the positive electrode sheet.

[0033] The beneficial effect of the secondary battery provided by the embodiment of the present application is that applying a positive electrode sheet having characteristics such as high energy density and cycle stability to the secondary battery can improve the electrochemical properties of the secondary battery, such as cycle stability and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] FIG1 is a particle size distribution curve of a metal oxide precursor in an embodiment of the present application;

[0036] FIG2 is a scanning electron microscope image of the metal oxide precursor prepared in Example 1;

[0037] FIG3 is a particle size distribution curve of the metal oxide precursor prepared in Example 1;

[0038] FIG4 is a scanning electron micrograph of the metal oxide precursor prepared in Example 2;

[0039] FIG5 is a particle size distribution curve of the metal oxide precursor prepared in Example 2;

[0040] FIG6 is a particle size distribution curve of the metal oxide precursor prepared in Example 3;

[0041] FIG7 is a scanning electron micrograph of the metal oxide precursor prepared in Comparative Example 1;

[0042] FIG8 is a particle size distribution curve of the metal oxide precursor prepared in Comparative Example 1;

[0043] FIG9 is a particle size distribution curve of the metal oxide precursor prepared in Comparative Example 2;

[0044] Figure 10 is a charge and discharge performance test graph of the positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 and 2, wherein A is the charge and discharge performance curve of the positive electrode material prepared in Example 1, B is the charge and discharge performance curve of the positive electrode material prepared in Example 2, C is the charge and discharge performance curve of the positive electrode material prepared in Example 3, D is the charge and discharge performance curve of the positive electrode material prepared in Comparative Example 1, and E is the charge and discharge performance curve of the positive electrode material prepared in Comparative Example 2. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit this application.

[0046] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The terms "upper", "lower", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of description and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[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 the embodiments of this application belong. The terms used in the description of the embodiments of this application herein are only for the purpose of describing specific embodiments or examples, and are not intended to limit the embodiments of this application. 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. The any and all combinations include any two related listed items, any more related listed items, or the combination of all related listed items.

[0048] To illustrate the technical solutions described in this application, the following provides a detailed description in conjunction with specific drawings and embodiments.

[0049] Some embodiments of this application provide a metal oxide precursor. The metal oxide precursor has a single crystal structure. The particle size distribution curve function f(x) of the metal oxide precursor represents the volume fraction corresponding to the particle size x and satisfies the following conditions:

[0050] (1) When a ≤ x ≤ b,

[0051] (2) When b < x ≤ c,

[0052] (3) When x c, f(x) = 0;

[0053] Where, 0.214μm ≤ a ≤ 0.260μm, 1.78μm ≤ b ≤ 3.1μm, 8.2μm ≤ c ≤ 31.2μm, ε, μ1, μ2 are all error coefficients, and -1.5 ≤ ε ≤ 1.5, -0.35 ≤ μ1 ≤ 0.35, -3 ≤ μ2 ≤ 10.

[0054] It should be noted that the unit of the particle size x in the particle size distribution curve function f(x) of the metal oxide precursor in the embodiments of this application is defaulted to μm. When calculating f(x), only the numerical value of x needs to be substituted, and the unit of μm does not need to be substituted; the unit of the corresponding volume fraction f(x) calculated at any particle size x is %. In addition, the particle size of the metal oxide precursor refers to the macroscopic morphology. When performing conventional particle size distribution detection, the particle size distribution in the dispersion cell includes the agglomerated state; the single crystal precursor has structural inheritance and is easy to be fired into a single crystal cathode. The single crystal structure has fewer grain boundaries, which is beneficial to improving the electron and ion conductivity, and thus improving the battery rate performance; in addition, there are fewer defects caused by fewer grain boundaries, higher strength and stability, and the occurrence of side reactions at the grain boundaries can also be reduced, improving the cycle life of the battery. The chemical composition and structure inside the single crystal structure are more uniform, which helps the uniform progress of the electrochemical reaction.

[0055] In the embodiments of the present application, the particle size distribution in the metal oxide precursor satisfies the above particle size distribution curve function f(x). The correlation between f(x) and the tap density of the precursor: the particle size corresponding to the peak position represents the most common particle size. A wider particle size distribution indicates the diversity of particle sizes, which is more conducive to filling voids under vibration conditions and increasing the tap density. For a ≤ x ≤ b, f(x) represents the particle size distribution smaller than the median diameter; for b < x ≤ c, f(x) represents the particle size distribution larger than the median diameter; for x c, it represents the particle size outside the f(x) distribution. This function can reflect the particle size distribution characteristics of the products of the present application. The three peak values of x, namely X = a and X = c, respectively represent the minimum and maximum particle sizes in the sample, and X = b is the highest point of the particle size distribution curve, indicating that the particles of this particle size account for the largest proportion in the sample. For a symmetric distribution: the peak value corresponds to the value of D50. In an asymmetric distribution, the D50 value may be slightly different. When x = b and b has a larger value, the median diameter particles are larger, there are more packing voids, and the tap density may be lower; when the peak particle size is smaller, the particles are finer, the packing is tighter, and the tap density may be higher. When X = a and X = c, the greater the difference between the maximum and minimum particle sizes, the higher the particle diversity. Larger particles help support the packing structure and prevent over-compaction, while smaller particles help fill voids, thereby increasing the tap density. Among them, a represents the minimum particle size. If the small particle size value is too small, it may lead to an increase in the adhesion between particles, affecting fluidity and processing performance; an appropriately small minimum particle size helps fill voids and increase the tap density. b represents the maximum particle size. A larger maximum particle size may lead to an increase in packing voids, reducing the tap density and also affecting the uniformity of the reaction. However, appropriately large particles can help support the packing structure and prevent over-compaction. c represents the peak particle size. If the median diameter value is too large, the tap density decreases, affecting the energy density of the battery and reducing the conductivity; if the median diameter value is too small, it is easy to agglomerate during the processing, affecting the uniformity of the slurry and the coating process. An appropriate median diameter value can balance the tap density, conductivity, and cycle stability, so this range is preferably selected.

[0056] In some embodiments, the particle size distribution curve function f(x) of the metal oxide precursor is a unimodal normal particle size distribution curve. When the particle size distribution curve of the metal oxide precursor in the embodiments of the present application satisfies a specific functional relationship, it has a unimodal normal particle size distribution curve and a wide particle size distribution. On the one hand, it is conducive to increasing the high tap density of the metal oxide precursor. When used to prepare the positive electrode material, it is conducive to increasing the loading amount in the crucible and reducing energy consumption. Moreover, the wide-distribution particle size characteristics of the metal oxide precursor are easily inherited by the positive electrode material, making the positive electrode material have a high filling rate and compaction density, which is conducive to improving the volumetric specific capacity of the battery. On the other hand, the metal oxide precursor that satisfies the specific particle size distribution curve function relationship in the embodiments of the present application can be widely applied to different elements, ratios, and preparation conditions, and can achieve a high tap density effect.

[0057] In some embodiments, the tap density of the metal oxide precursor is 1.2 g / cm 3 Up to 3.5g / cm 3 In this case, the metal oxide precursor has a density of 1.2 g / cm 3 Up to 3.5g / cm 3 The high tap density of the metal oxide precursor is beneficial for increasing the filling volume and reducing energy consumption when used to prepare the positive electrode material. In addition, the wide distribution particle size characteristics of the metal oxide precursor are easily inherited by the positive electrode material, so that the positive electrode material has a high filling rate and compaction density, which is beneficial to improving the volume specific capacity of the battery. For example, the high tap density of the metal oxide precursor can be 1.2g / cm 3 , 1.5g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 , 2.5g / cm 3 , 3g / cm 3 , 3.5g / cm 3 Typical but non-restrictive values ​​include any point value or any interval between any two point values.

[0058] 1 is a graph showing the particle size distribution curve of a metal oxide precursor in one embodiment. The highest point of the particle size distribution curve function f(x) of the metal oxide precursor is the peak value f(x). max , f(x) max is 5 to 10. Exemplarily, the peak value f(x) of the particle size distribution curve function f(x) of the metal oxide precursor is max It can be any typical but non-restrictive point value such as 5, 6, 7, 8, 9, 10, or an interval between any two point values. If the peak value is too large, the stacking process will cause a large number of voids, affecting the tap density and thus reducing the energy density; if the peak value is too small, it will aggravate the agglomeration of particles, which is not conducive to uniform slurrying and coating. max A value of 5 to 10 helps to optimize the tap density and the filling effect between particles, thereby improving energy density and structural stability.

[0059] In some embodiments, the half-peak width of the particle size distribution curve function f(x) of the metal oxide precursor is the half-peak value f(x) max / 2, the difference between the corresponding particle size x1 and the particle size x2 in the particle size distribution curve function f(x), wherein the particle size x1 and the particle size x2 are independently selected from any value between 0.6μm-6μm.

[0060] In some embodiments, the half-width of the particle size distribution curve function f(x) of the metal oxide precursor is 3 μm to 5 μm. Exemplarily, the half-width of the particle size distribution curve function f(x) of the metal oxide precursor can be any typical but non-limiting point value such as 3 μm, 4 μm, 5 μm, or an interval value between any two point values. The half-width indicates the consistency of the particle size. A small half-width indicates uniform particle size, and a large half-width indicates diversity in particle size. Within the half-width of 3-5 μm, the particle size has a certain diversity, and small particles fill the gaps to achieve a higher tap density, thereby improving the battery capacity and energy density.

[0061] In some embodiments, the cumulative particle size distribution function corresponding to the particle size distribution function f(x) of the metal oxide precursor is D n , n% = ∑f(x), where f(x): when the particle size is x μm, the volume percentage of the particle size; D n : When the cumulative volume fraction is n%, the particle size corresponding to the maximum value of x in the cumulative process. n%: When the volume percentage is from f(x min ) is the total volume fraction when it is accumulated to f(x). When the cumulative particle size distribution curve function is D 25 When 0.5μm≤x≤2.0μm. It should be noted that particle size distribution refers to the volume percentage of particles of different sizes in a powder sample measured by a specific instrument and method. n Where n is the percentage. 25 It is the particle size corresponding to when the cumulative particle size distribution number of the metal oxide precursor reaches 25%. D25: Indicates that 25% of the particle volume is smaller than this particle size, that is, the content of smaller particles. If D25 is too large, it means that the proportion of smaller particles is low, which may lead to a decrease in the reaction surface area and the initial discharge capacity of the battery. If D25 is too small, it means that the proportion of smaller particles is high, which can increase the reaction surface area and improve the initial capacity, but will increase side reactions and affect the cycle life. If D25 is within the range of 0.5μm≤x≤2.0μm, it can reduce side reactions and improve the cycle life while increasing the initial capacity.

[0062] In some embodiments, the cumulative particle size distribution function corresponding to the particle size distribution function f(x) of the metal oxide precursor is D n , n% = ∑f(x), when the cumulative particle size distribution curve function is D 50 When , 1.2μm≤x≤3.8μm. It should be noted that D 50 It is the particle size corresponding to the cumulative particle size distribution of the metal oxide precursor reaching 50%. 50 (Median particle size): D 50Too large may lead to insufficient specific surface area, poor conductivity, low electrode density and structural stability problems, reducing the overall performance and life of the battery. 50 Although too small a particle size can increase the reaction activity and specific surface area, it will also lead to problems such as increased side reactions, particle agglomeration, and decreased mechanical strength. 50 Within the range of 1.2μm≤x≤3.8μm, it is possible to ensure the specific surface area and reaction activity while avoiding excessive side reactions. At the same time, it can improve the tap density and conductivity, and enhance the energy density and rate performance of the battery.

[0063] In some embodiments, the cumulative particle size distribution function corresponding to the particle size distribution function f(x) of the metal oxide precursor is D n , n% = ∑f(x), when the cumulative particle size distribution curve function is D 75 When , 2μm≤x≤5μm. It should be noted that D 75 It is the particle size corresponding to when the cumulative particle size distribution of the metal oxide precursor reaches 75%. D75 (content of larger particles): If D75 is too large, the proportion of larger particles is higher, and the voids are large when stacked, resulting in low tap density and affecting energy density. If D75 is too small, the proportion of larger particles is lower, which increases the tap density and energy density. However, smaller particles are more prone to deformation and stress concentration during volume changes, causing structural deformation or damage to the material, thereby affecting structural stability. When D75 is within the range of 2μm≤x≤5μm, it is possible to maintain structural stability while increasing energy density.

[0064] In some embodiments, in the particle size distribution curve function f(x) of the metal oxide precursor, the particle size distribution span value is 1.0 to 2.5. For example, in the particle size distribution curve function f(x) of the metal oxide precursor, the particle size distribution span value can be any typical but non-limiting point value such as 1.0, 1.5, 2.0, 2.5, or an interval value between any two point values. It should be noted that the particle size distribution span value is K 90 =(D 90 -D 10 ) / D 50 , where D 10 D is the particle size corresponding to the cumulative particle size distribution of the metal oxide precursor reaching 10%, 90It is the particle size corresponding to when the cumulative particle size distribution number of the metal oxide precursor reaches 90%. If D10 is too large, it means that the proportion of very small particles is low, which will reduce the surface area and thus affect the initial discharge capacity. If D10 is too small, it means that the proportion of very small particles is high, which will cause agglomeration and increase side reactions, which will reduce the cycle life. If the D90 value is too large, it will lead to uneven particle distribution, insufficient specific surface area, low compaction density, poor mechanical properties, large volume changes and other problems, affecting the electrochemical performance and cycle stability of the battery. Although a D90 value that is too small can increase the specific surface area and initial capacity, it will also lead to an increase in side reactions, resulting in problems such as capacity attenuation and decreased cycle stability.

[0065] In some embodiments, the metal oxide precursor has the general chemical formula Mn y M 1-y O2, wherein 0.1≤y≤0.9, and M is selected from at least one of Ni, Fe, Cu, Zn, Co, Ti, Mg, and Al. It is understood that the metal oxide precursor in the embodiment 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 embodiment of the present application.

[0066] In some embodiments, the metal oxide precursor is a cubic crystal system, that is, the single crystal structure of the metal oxide precursor is a cubic crystal system.

[0067] The embodiment of the present application provides a method for preparing the above metal oxide precursor, and the preparation method is selected from the spray pyrolysis method.

[0068] The above-mentioned metal oxide precursor in the embodiment of the present application can be prepared by spray pyrolysis, and the obtained metal oxide precursor has a single crystal structure, and the particle size distribution of the single crystal structure in the precursor satisfies the above-mentioned particle size distribution curve function f(x), which is beneficial to improving the high tap density of the metal oxide precursor and can be widely applied to different elements, proportions and preparation conditions.

[0069] It should be noted that the specific operation of the spray pyrolysis method can refer to the existing method, and the embodiments of the present application will not be described in detail.

[0070] In some embodiments, the spray pyrolysis method uses a pyrolysis temperature of 550°C to 950°C. Under these pyrolysis temperature conditions, lower pyrolysis temperatures may result in larger, unevenly distributed particles with lower crystallinity. Higher pyrolysis temperatures accelerate droplet decomposition, reduce particle size, and achieve a more uniform particle size distribution. Excessively high pyrolysis temperatures may lead to sintering and agglomeration of particles, resulting in larger particle size and a wider particle size distribution.

[0071] It should be noted that the pyrolysis temperature is the operating temperature of the pyrolysis device.

[0072] In some embodiments, the atomization pressure of the spray pyrolysis method is 0.35 MPa to 0.7 MPa; under this pyrolysis temperature condition, the atomization pressure is high, the atomized droplets are small, and uniform small particles are more easily formed during the pyrolysis process. However, if the atomization pressure is too high, some droplets may also quickly aggregate during the spraying process, forming a secondary agglomeration phenomenon. If the atomization pressure is low, the atomized droplets are larger, the generated particles are large in size, and the particle size distribution is wide. Within the atomization pressure range of the present application, the particle size is moderate, the particle size distribution has a wide single peak, which is conducive to improving the tap density, and the agglomeration phenomenon is not obvious.

[0073] In some embodiments, the liquid flow rate of the spray pyrolysis method is 0.3m 3 / h to 0.8m 3 / h. Under the pyrolysis temperature condition, the liquid inlet flow rate is too large. Due to the limited atomization capacity of the nozzle, a large amount of liquid cannot be fully dispersed into small droplets, resulting in some droplets not being completely dried, forming larger particles or agglomeration, which may lead to a too wide particle size distribution. At a low liquid inlet flow rate, the droplets have enough time to dry and decompose, forming smaller and uniform particles. Within the liquid inlet flow rate range of the present application, the particle size is moderate, the particle size distribution has a wide single peak, which is conducive to improving the tap density, and the agglomeration phenomenon is not obvious.

[0074] For example, the pyrolysis temperature of the spray pyrolysis method can be 550°C, 600°C, 650°C, 700°C, 800°C, 900°C, 950°C, etc., which are typical but non-limiting values, or an interval between any two values; the atomization pressure can be 0.35MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, etc., which are typical but non-limiting values, or an interval between any two values; the feed flow rate can be 0.3m 3 / h、0.4m 3 / h、0.5m 3 / h、0.6m 3 / h、0.7m 3 / h、0.8m 3 Typical but non-restrictive arbitrary point values ​​or interval values ​​between any two point values, such as / h.

[0075] By adjusting conditions such as the pyrolysis temperature, atomization pressure, and liquid inlet flow rate, it is beneficial to precisely control the metal oxide precursors prepared using different elements and proportions so that they can all meet the specific particle size distribution curve function of the embodiment of the present application, thereby achieving a higher tap density effect.

[0076] The preparation method satisfies the above-mentioned conditions such as pyrolysis temperature, atomization pressure and liquid inlet flow rate. It is understandable that other preparation methods that do not meet the above-mentioned conditions such as pyrolysis temperature, atomization pressure and liquid inlet flow rate can also make the metal oxide precursor have a specific particle size distribution curve under certain conditions. The embodiments of the present application do not limit this.

[0077] The embodiments of the present application also provide a positive electrode material prepared from the above metal oxide precursor.

[0078] Using the metal oxide precursor of the embodiment of the present application to prepare the positive electrode material can enable the positive electrode material to inherit the wide distribution particle size characteristics of the metal oxide precursor, achieve a higher filling rate and compaction density, and thus improve the volumetric capacity of batteries such as sodium ion batteries.

[0079] It should be noted that the preparation method of the positive electrode material refers to the existing method, and the embodiments of this application will not be repeated here.

[0080] An embodiment of the present application further provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer disposed on a surface of the positive electrode current collector, wherein the positive electrode material layer comprises the above-mentioned positive electrode material.

[0081] The positive electrode material layer of the positive electrode sheet of the embodiment of the present application includes the above-mentioned positive electrode material with a high filling rate and compaction density, thereby improving the energy density, cycle stability and other electrochemical properties of the positive electrode sheet.

[0082] An embodiment of the present application further provides a secondary battery, comprising the above-mentioned positive electrode sheet.

[0083] The embodiments of the present application apply a positive electrode sheet having characteristics such as high energy density and cycle stability to a secondary battery, which can improve the electrochemical properties of the secondary battery, such as cycle stability and cycle life.

[0084] Exemplarily, the secondary battery may be a sodium ion battery.

[0085] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector, for example, aluminum foil is used as the metal foil; the composite current collector may 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).

[0086] It is understandable that the positive electrode material layer further includes a binder and a conductive agent. Among them, the binder can be any commercially available binder for positive electrode sheets, including but not limited to at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-fluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin, or a binder prepared by any known method. There is no limitation in the comparison of the embodiments of the present application; the conductive agent can be any commercially available conductive agent for sodium-ion batteries, such as carbon black, graphite, etc.

[0087] 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 embodiments of the present application and should not be regarded as limiting the scope of the embodiments of the present application. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0088] Example 1

[0089] A mixed metal salt solution was prepared by mixing nickel salt, iron salt, and manganese salt in a molar ratio of metal atoms of 1:1:1, and then under the conditions of a liquid inlet flow rate of 0.38 m 3 / h and an atomization pressure of 0.35 MPa, the mixed metal salt solution was introduced into the roasting furnace in the form of droplets, and at a pyrolysis temperature of 550 °C, the droplets were subjected to 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 NFM111.

[0090] The surface morphology of the metal oxide precursor prepared in this example is shown in Figure 2. It can be seen that the metal oxide precursor is a single crystal structure, and the particle size distribution is relatively wide, and the agglomeration phenomenon is significantly improved.

[0091] The particle size distribution curve of the metal oxide precursor prepared in this example is shown in Figure 3. It can be seen that the particle size distribution curve of the metal oxide precursor is a normal curve with a single-peak wide distribution, and the particle size distribution curve function f(x) satisfies: when 0.243 ≤ x ≤ 2.421, when 2.421 < x ≤ 18.664, when x < 18.664 or x > 0.243, f(x) = 0.

[0092] Example 2

[0093] 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, and then under the conditions of a liquid inlet flow rate of 0.55 m3 Under the conditions of a liquid inlet flow rate of / h and an atomization pressure of 0.7 MPa, the mixed metal salt solution enters the roasting furnace in the form of droplets, and at a pyrolysis temperature of 950 °C, the droplets form a metal oxide precursor through processes such as evaporation, drying, thermal decomposition, and sintering. The metal oxide precursor product obtained is simply represented as NCFM2133.

[0094] The surface morphology of the metal oxide precursor obtained in this embodiment is shown in Figure 4. It can be seen that the metal oxide precursor is a single crystal structure, and the particle size distribution is relatively wide, with the agglomeration phenomenon significantly improved.

[0095] The particle size distribution curve of the metal oxide precursor obtained in this embodiment is shown in Figure 5. It can be seen that the particle size distribution curve of the metal oxide precursor is a normal curve with a single-peak wide distribution, and the particle size distribution curve function f(x) satisfies: when 0.214 ≤ x ≤ 1.73, when 1.73 < x ≤ 8.3, when x < 8.3 or x > 0.214, f(x) = 0.

[0096] Example 3

[0097] A mixed metal salt solution is prepared by mixing iron salt and manganese salt in a molar ratio of metal atoms of 65:35, and then at a liquid inlet flow rate of 0.80 m 3 / h and an atomization pressure of 0.5 MPa, the mixed metal salt solution enters the roasting furnace in the form of droplets, and at a pyrolysis temperature of 720 °C, the droplets form a metal oxide precursor through processes such as evaporation, drying, thermal decomposition, and sintering. The metal oxide precursor product obtained is simply represented as FM6535.

[0098] The particle size distribution curve of the metal oxide precursor obtained in this embodiment is shown in Figure 6. It can be seen that the particle size distribution curve of the metal oxide precursor is a normal curve with a single-peak wide distribution, and the particle size distribution curve function f(x) satisfies: when 0.255 ≤ x ≤ 3.08, when 3.08 < x ≤ 31.1, when x < 31.1 or x > 0.255, f(x) = 0.

[0099] Example 4

[0100] A mixed metal salt solution is prepared by mixing nickel salt, cobalt salt, and manganese salt in a molar ratio of metal atoms of 80:10:10, and then at a liquid inlet flow rate of 0.35 m 3Under the conditions of a liquid inlet flow rate of 0.5 m / h and an atomization pressure of 0.8 MPa, the mixed metal salt solution enters the roasting furnace in the form of droplets, and at a pyrolysis temperature of 650 °C, the droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The metal oxide precursor product obtained is simply represented as NCM811.

[0101] The particle size distribution of the metal oxide precursor obtained in this example is a normal curve with a single-peak wide distribution, and the particle size distribution curve function f(x) satisfies: when 0.257 ≤ x ≤ 1.89, when 1.89 < x ≤ 9.36, when x < 8.97 or x > 0.257, f(x) = 0.

[0102] Example 5

[0103] A mixed metal salt solution is prepared by mixing nickel salt, cobalt salt, manganese salt, and titanium salt in a molar ratio of metal atoms of 60:10:20:10, and then at a liquid inlet flow rate of 0.5 m 3 / h and an atomization pressure of 0.6 MPa, the mixed metal salt solution enters the roasting furnace in the form of droplets, and at a pyrolysis temperature of 800 °C, the droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The metal oxide precursor product obtained is simply represented as NCMT6121.

[0104] The particle size distribution of the metal oxide precursor obtained in this example is a normal curve with a single-peak wide distribution, and the particle size distribution curve function f(x) satisfies: when 0.216 ≤ x ≤ 3.03, when 3.03 < x ≤ 28.95, when x < 28.95 or x > 0.216, f(x) = 0.

[0105] Comparative Example 1

[0106] A mixed metal salt solution is prepared by mixing nickel salt, iron salt, and manganese salt in a molar ratio of metal atoms of 1:1:1, and then at a liquid inlet flow rate of 0.25 m 3 / h and an atomization pressure of 0.35 MPa, the mixed metal salt solution enters the roasting furnace in the form of droplets, and at a pyrolysis temperature of 500 °C, the droplets undergo processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The metal oxide precursor product obtained is simply represented as NFM111.

[0107] The surface morphology of the metal oxide precursor obtained in this comparative example is shown in Figure 7, and it can be seen that the agglomeration phenomenon of this metal oxide precursor is extremely serious.

[0108] The particle size distribution curve of the metal oxide precursor obtained in this comparative example is shown in Figure 8 of the attached drawings. It can be seen that the particle size distribution of this metal oxide precursor is wide and presents a bimodal distribution, which does not satisfy the particle size distribution curve function f(x) provided in the embodiments of this application.

[0109] Comparative Example 2

[0110] 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. Then, under the conditions of a liquid inlet flow rate of 0.85 m 3 / h and an atomization pressure of 0.7 MPa, the mixed metal salt solution was made to enter the roasting furnace in the form of droplets, and under the pyrolysis temperature condition of 1000 °C, the droplets underwent processes such as evaporation, drying, thermal decomposition, and sintering molding to form a metal oxide precursor. The metal oxide precursor product obtained was simply denoted as NCFM2133.

[0111] The particle size distribution curve of the metal oxide precursor obtained in this comparative example is shown in Figure 9 of the attached drawings. It can be seen that the particle size distribution of this metal oxide precursor is wide and presents a bimodal distribution, which does not satisfy the particle size distribution curve function f(x) provided in the embodiments of this application.

[0112] Comparative Example 3

[0113] A mixed metal salt solution was prepared by mixing nickel salt, cobalt salt, and manganese salt in a molar ratio of metal atoms of 8:1:1. Then, under the conditions of a liquid inlet flow rate of 0.3 m 3 / h and an atomization pressure of 0.2 MPa, the mixed metal salt solution was made to enter the roasting furnace in the form of droplets, and under the pyrolysis temperature condition of 1000 °C, the droplets underwent processes such as evaporation, drying, thermal decomposition, and sintering molding to form a metal oxide precursor. The metal oxide precursor product obtained was simply denoted as NCM811.

[0114] The particle size of the metal oxide precursor obtained in this comparative example is large, and its irregular agglomeration phenomenon is extremely serious.

[0115] The particle size distribution curve of the metal oxide precursor obtained in this comparative example presents an extremely narrow unimodal distribution, and its particle size distribution curve function f(x) is satisfied but not within the preferred range of this application: when 0.315 ≤ x ≤ 1.54, when 1.54 < x ≤ 6.82, when x < 6.82 or x > 0.315, f(x) = 0.

[0116] According to the particle size distribution curves of the metal oxide precursors obtained in Examples 1 to 5 and Comparative Examples 1 and 3, the measured particle size distribution parameters are shown in Table 1 below.

[0117] Table 1

[0118] From the above test results, it can be seen that when the particle size distribution of the single crystal particles in the metal oxide precursor of the embodiment of the present application satisfies the particle size distribution curve function f(x) of the present application, the tap density of the prepared metal oxide precursor is 1.2 g / cm 3 Up to 3.5g / cm 3 . It has a high tap density, which is beneficial to improving the filling rate and compaction density of the positive electrode material, thereby increasing the volumetric capacity of the battery.

[0119] Application Examples

[0120] The metal hydroxide precursors prepared in Examples 1 to 5 and Comparative Examples 1 and 3 were mixed with sodium carbonate in a molar ratio of 1:1, and then placed in a muffle furnace. In an air atmosphere, the temperature was increased to 900°C at a heating rate of 5°C / min. After constant temperature sintering for 15 hours, the mixture was naturally cooled, crushed, and sieved to obtain a positive electrode material.

[0121] The prepared positive electrode material was made into a sodium ion button battery, and the charge and discharge performance was tested under voltage conditions of 2V-4.15V. The test results are shown in Figure 10 and Table 2 below.

[0122] Table 2

[0123] According to Figure 10 and Table 2, the cathode materials prepared in Examples 1 to 5 have a high first discharge capacity under the voltage condition of 2V-4.15V, with the highest reaching about 167.8mAh / g. However, compared with Example 1, the first discharge capacity of Comparative Example 1 is significantly lower; and compared with Example 2, the first discharge capacity of Comparative Example 2 is significantly worse. Therefore, the metal oxide precursors of the embodiments of the present application can meet the specific unimodal normal particle size distribution curve, not only having a 1.2g / cm 3 Up to 3.5g / cm 3 It has a high tap density and can be widely applied to different elements, proportions and preparation conditions, which is beneficial to improving the filling rate and compaction density of the positive electrode material, thereby improving the volumetric capacity of the sodium ion battery.

[0124] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0125] The above are merely optional embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A metal oxide precursor, characterized in that, The metal oxide precursor has a single crystal structure. The particle size distribution curve function f(x) of the metal oxide precursor represents the volume fraction corresponding to the particle size x and satisfies the following conditions: (1) When a ≤ x ≤ b, (2) When b < x ≤ c, (3) When x c, f(x) = 0; where 0.214 μm ≤ a ≤ 0.260 μm, 1.78 μm ≤ b ≤ 3.1 μm, 8.2 μm ≤ c ≤ 31.2 μm, and ε, μ1, and μ2 are all error coefficients, and -1.5 ≤ ε ≤ 1.5, -0.35 ≤ μ1 ≤ 0.35, -3 ≤ μ2 ≤ 10.

2. The metal oxide precursor according to claim 1, wherein The particle size distribution curve function f(x) of the metal oxide precursor is a single-peak normal particle size distribution curve.

3. The metal oxide precursor according to claim 1, wherein, The peak f(x) of the particle size distribution curve function f(x) of the metal oxide precursor max is from 5 to 10.

4. The metal oxide precursor according to claim 1, wherein The full width at half maximum of the particle size distribution curve function f(x) of the metal oxide precursor is 3 μm to 5 μm.

5. The metal oxide precursor according to claim 1, characterized in that, The cumulative particle size distribution curve function corresponding to the particle size distribution curve function f(x) of the metal oxide precursor is D n , n% = ∑f(x). When the cumulative particle size distribution curve function is D 25 , 0.5 μm ≤ x ≤ 2.0 μm.

6. The metal oxide precursor according to claim 1, wherein The cumulative particle size distribution curve function corresponding to the particle size distribution curve function f(x) of the metal oxide precursor is D n , n% = ∑f(x). When the cumulative particle size distribution curve function is D 50 , 1.2 μm ≤ x ≤ 3.8 μm.

7. The metal oxide precursor according to claim 1, wherein The cumulative particle size distribution curve function corresponding to the particle size distribution curve function f(x) of the metal oxide precursor is D n , n% = ∑f(x). When the cumulative particle size distribution curve function is D 75 , 2 μm ≤ x ≤ 5 μm.

8. The metal oxide precursor according to claim 1, wherein In the particle size distribution curve function f(x) of the metal oxide precursor, the span value of the particle size distribution is 1.0 to 2.

5.

9. The metal oxide precursor according to claim 1, wherein The chemical general formula of the metal oxide precursor is expressed as Mn y M 1-y O2, where 0.1 ≤ y ≤ 0.9, and M is selected from at least one of Ni, Fe, Cu, Zn, Co, Ti, Mg, and Al.

10. The metal oxide precursor according to claim 1, characterized in that, The metal oxide precursor is a cubic crystal system.

11. The metal oxide precursor according to any one of claims 1 to 10, characterized in that, The tapped density of the metal oxide precursor is 1.2 g / cm 3 to 3.5 g / cm 3 .

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

13. The method for preparing the metal oxide precursor according to claim 12, wherein, The pyrolysis temperature of the spray pyrolysis is 550 °C to 950 °C.

14. The method for preparing a metal oxide precursor according to claim 12, wherein, The atomization pressure of the spray pyrolysis is 0.35 MPa to 0.7 MPa.

15. The method for preparing a metal oxide precursor according to claim 12, wherein, The feed flow rate obtained by the spray pyrolysis method is 0.3 m 3 / h to 0.8 m 3 / h.

16. A positive electrode material prepared from the metal oxide precursor according to any one of claims 1 to 11 or the metal oxide precursor prepared by the method according to any one of claims 12 to 15.

17. 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, and the positive electrode material layer includes the positive electrode material according to claim 16.

18. A secondary battery, characterized in that, It includes the positive electrode sheet according to claim 17.

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