Metal hydroxide precursor as well as preparation method and application thereof

Abstract

The invention relates to a metal hydroxide precursor and a preparation method and application thereof, the oxide precursor comprises secondary particles composed of a plurality of primary particles, the primary particles are lath-shaped, and the length-width ratio is greater than or equal to 3: 1; the degree of sphericity of the secondary particles is greater than or equal to 0.7. The metal hydroxide precursor disclosed by the invention is relatively good in uniformity and high in structural stability, and can be used for remarkably improving the cycle performance, reducing the capacity fading and prolonging the service life of a battery when being used for preparing a battery positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of battery cathode material precursor technology, and in particular to a metal hydroxide precursor, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries possess the characteristics required for large-scale energy storage systems: abundant sodium resources, low maintenance costs, safety, and high energy efficiency. Furthermore, sodium-ion batteries have a wider operating temperature range and higher energy efficiency, providing better protection during cycling under extreme conditions. Compared to lithium-ion batteries, although their energy density is lower, sodium-ion batteries have advantages in many aspects, including resource availability, cost, safety, rate performance, and low-temperature performance. Against this backdrop, developing sodium-ion batteries as an alternative to lithium-ion batteries has significant economic value and strategic importance.

[0003] The preparation of ternary precursors for sodium-ion batteries uses ammonia as a complexing agent and sodium hydroxide as a precipitant. Because the hydroxide crystal forms (hexagonal) of Ni, Fe, and Mn are similar and their Ksp differences are small, precursors with high tap density and good sphericity are easily prepared. However, with the development of sodium-ion batteries, increasingly higher requirements are being placed on their cycle and rate performance. Traditional metal hydroxide precursors used as cathode materials suffer from defects such as uneven chemical composition, irregular particle morphology and easy agglomeration, and low tap density. This leads to low consistency and yield between different batches of products, poor reliability, and an inability to achieve optimal electrochemical performance. Therefore, exploring suitable layered transition metal oxides and their application in sodium-ion batteries is of urgent significance. Summary of the Invention

[0004] Therefore, it is necessary to provide a metal hydroxide precursor, its preparation method, and its application to address the above problems. The metal hydroxide precursor has good uniformity and high structural stability, and its use in preparing battery cathode materials can significantly improve cycle performance, reduce capacity decay, and extend battery life.

[0005] A metal hydroxide precursor comprises secondary particles consisting of a plurality of primary particles, wherein:

[0006] The primary particles are in the shape of strips, with an aspect ratio greater than or equal to 3:1;

[0007] The sphericity of the secondary particles is greater than or equal to 0.7.

[0008] In one embodiment, the metal hydroxide precursor further satisfies at least one of the following conditions:

[0009] (1) The aspect ratio of the primary particles is 3:1 to 8:1;

[0010] (2) The thickness of the primary particles is 50 nm to 150 nm;

[0011] (3) The sphericity of the secondary particles is 0.7~0.9;

[0012] (4) The XRD diffraction peak intensity ratio of the (101) and (001) crystal planes in the metal hydroxide precursor is 2.0~2.4;

[0013] (5) The median particle size of the metal hydroxide precursor is 3 μm to 10 μm;

[0014] (6) The tap density of the metal hydroxide precursor is 1.2 g / cm³. 3 ~1.6g / cm 3 ;

[0015] (7) The specific surface area of ​​the metal hydroxide precursor is 10 m². 2 / g~30m 2 / g;

[0016] (8) The chemical formula of the metal hydroxide precursor is Ni x M y Mn 1-x-y (OH)2, wherein 0.01≤x≤0.8, 0.01≤y≤0.08, and M is selected from one or more of Cu, Co, Zn, Mg, Cr, and Zr.

[0017] The metal hydroxide precursor of the present invention consists of secondary particles with high sphericity formed by stacking primary particles with specific morphology and size. This structural design can ensure that the metal hydroxide precursor has excellent uniformity and structural stability. When used to prepare battery cathode materials, it can significantly improve cycle performance, reduce capacity decay, and extend battery life.

[0018] A method for preparing the metal hydroxide precursor as described above includes the following steps:

[0019] Prepare mixed metal salt solutions, precipitant solutions, and complexing agent solutions;

[0020] Under a protective atmosphere, a mother liquor is prepared by passing a precipitant solution and a complexing agent solution through water;

[0021] A co-precipitation reaction was carried out by simultaneously introducing a mixed metal salt solution, a precipitant solution, and a complexing agent solution into the mother liquor to obtain a metal hydroxide precursor.

[0022] Among them, the mixed metal salt solution, precipitant solution, and complexing agent solution that flow in satisfy the flow coefficient K = Q3 / (Q1 + Q2), where Q1 is the flow rate of the mixed metal salt solution, Q2 is the flow rate of the precipitant solution, Q3 is the flow rate of the complexing agent solution, and K is 0.08 to 0.1.

[0023] In one embodiment, the flow coefficient K and the temperature of the coprecipitation reaction satisfy:

[0024] When 0.08 ≤ K ≤ 0.09, the temperature of the coprecipitation reaction is 50°C < T ≤ 60°C;

[0025] Or, when 0.09 < K ≤ 0.1, the temperature of the coprecipitation reaction is 60°C < T ≤ 70°C.

[0026] In one embodiment, the flow coefficient K and the pH of the coprecipitation reaction satisfy:

[0027] When 0.08 ≤ K ≤ 0.09, the pH is 10.5 to 11.0;

[0028] Or, when 0.09 < K ≤ 0.1, the pH is greater than or equal to 10.0 and less than 10.5.

[0029] In one embodiment, the steps of preparing the mixed metal salt solution, precipitant solution, and complexing agent solution satisfy at least one of the following conditions:

[0030] (1) The total metal ion concentration in the mixed metal salt solution is 0.1 mol / L to 3 mol / L;

[0031] (2) The concentration of the precipitant solution is 0.1 mol / L to 5 mol / L;

[0032] (3) The concentration of the complexing agent solution is 1 g / L to 5 g / L.

[0033] In one embodiment, the steps of preparing the mother liquor satisfy at least one of the following conditions:

[0034] (1) The pH of the mother liquor is 10 to 14;

[0035] (2) The temperature is 40°C to 70°C.

[0036] A positive electrode material prepared from the metal hydroxide precursor as described above.

[0037] A positive electrode sheet 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 as described above.

[0038] A secondary battery includes the positive electrode sheet as described above.

[0039] This invention optimizes the traditional co-precipitation process by synergistically controlling the flow rates of the mixed metal salt solution, precipitant solution, and complexing agent solution to meet a specific flow coefficient K. This effectively improves the problem of uneven element distribution during synthesis, thereby fundamentally stabilizing the structural morphology of the metal hydroxide precursor and achieving synergistic structural regulation. This is beneficial for further reducing the production cost of battery cathode material precursors and improving the cycle performance of the battery. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 The images shown are scanning electron microscope (SEM) images of the metal hydroxide precursor prepared in Example 1 at different magnifications, where A is a 5000x SEM image and B is a 10000x SEM image.

[0042] Figure 2 This is a cross-sectional electron microscope image of the metal hydroxide precursor prepared in Example 1;

[0043] Figure 3 The images shown are scanning electron microscope (SEM) images of the metal hydroxide precursor prepared in Example 2 at different magnifications. A is a scanning electron microscope image at 5000x magnification, and B is a scanning electron microscope image at 10000x magnification.

[0044] Figure 4 This is a cross-sectional electron microscope image of the metal hydroxide precursor prepared in Example 2;

[0045] Figure 5 The images are scanning electron microscope (SEM) images of the metal hydroxide precursor prepared in Comparative Example 1 at different magnifications. A is a scanning electron microscope image at 5000x magnification, and B is a scanning electron microscope image at 10000x magnification.

[0046] Figure 6 The images shown are scanning electron microscope (SEM) images of the metal hydroxide precursor prepared in Comparative Example 2 at different magnifications. A is a scanning electron microscope image at 5000x magnification, and B is a scanning electron microscope image at 10000x magnification.

[0047] Figure 7 The images shown are scanning electron microscope (SEM) images of the metal hydroxide precursor prepared in Comparative Example 3 at different magnifications. In the images shown, A is a 5000x SEM image and B is a 10000x SEM image. Detailed Implementation

[0048] To facilitate understanding of the present invention, it 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. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. In this invention, when referring to numerical ranges, unless otherwise specified, such ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Furthermore, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0050] The present invention provides a metal hydroxide precursor comprising secondary particles composed of a plurality of primary particles, wherein: the primary particles are lath-shaped with an aspect ratio greater than or equal to 3:1; and the secondary particles have a sphericity greater than or equal to 0.7.

[0051] The metal hydroxide precursor of the present invention consists of secondary particles with high sphericity formed by stacking primary particles with specific morphology and size. This structural design can ensure that the metal hydroxide precursor has excellent uniformity and structural stability. When used to prepare battery cathode materials, it can significantly improve cycle performance, reduce capacity decay, and extend battery life.

[0052] It should be noted that the term "strip-shaped" refers to a relatively long length, narrow width and thickness, and a flat shape. This means that the longitudinal section of the strip-shaped particle includes, but is not limited to, rectangular, trapezoidal, and other shapes. When the longitudinal section is trapezoidal, the strip-shaped particle has a wedge-shaped structure. The sphericity refers to the degree to which a particle approximates an ideal sphere; the closer a particle's morphology is to a sphere, the closer its sphericity is to 1.

[0053] In one embodiment of the present invention, the aspect ratio of the primary particles is preferably 3:1 to 8:1, including but not limited to any one of 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or any range between two of them.

[0054] In one embodiment of the present invention, the thickness of the primary particle is preferably 50nm to 150nm, including but not limited to any one of 50nm, 80nm, 100nm, 120nm, and 150nm or any range between two of them.

[0055] In one embodiment of the present invention, the sphericity of the secondary particles is preferably 0.7 to 0.9, including but not limited to any one of 0.7, 0.75, 0.8, 0.85, and 0.9 or any range between two of them.

[0056] In one embodiment of the present invention, the ratio of the XRD diffraction peak intensities of the (101) and (001) crystal planes in the metal hydroxide precursor is preferably 2.0 to 2.4, including but not limited to any one of 2.0, 2.1, 2.2, 2.3, 2.4 or any range between the two. Increasing the proportion of the (101) crystal plane is beneficial to improving the ionic conductivity of the cathode material.

[0057] In one embodiment of the present invention, the median particle size of the metal hydroxide precursor is preferably 3 μm to 10 μm, including but not limited to any one of 3 μm, 5 μm, 7 μm, 9 μm, and 10 μm or any range between the two.

[0058] In one embodiment of the present invention, the tap density of the metal hydroxide precursor is preferably 1.2 g / cm³. 3 ~1.6g / cm 3 Including but not limited to 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 Any point value in the range or any range between two values.

[0059] In one embodiment of the present invention, the specific surface area of ​​the metal hydroxide precursor is preferably 10 m². 2 / g~30m 2 / g, including but not limited to 10m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g、30m 2 Any point value in / g or any range of values ​​between the two.

[0060] In one embodiment of the present invention, the chemical formula of the metal hydroxide precursor is Ni. x M y Mn 1-x-y(OH)₂, where 0.01 ≤ x ≤ 0.8, for example, x can be a number within the following ranges or any combination of the following two numbers: 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.3 5, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, preferably 0.01≤x≤0.5, 0.01≤y≤0.08, M is selected from one or more of Cu, Co, Zn, Mg, Cr, Zr, preferably M is selected from Mg, or M is selected from one or more of Mg and Cu, Co, Zn, Cr, Zr. The metal hydroxide precursor is preferably a magnesium-doped, iron-free, manganese-rich nickel-based hydroxide precursor. Magnesium doping not only occupies some nickel ion positions, stabilizing the crystal structure and suppressing structural phase transitions, but also provides free electrons, generates holes, and improves electrical conductivity.

[0061] It should be noted that this invention includes, but is not limited to, magnesium doping. For example, zinc ions have a large radius, which can increase the interlayer spacing and improve the insertion / extraction rate of sodium ions. Adding copper can change the electronic structure of the material, stabilize the redox reaction of oxygen ions, suppress the damage caused by structural phase transitions, reduce the capacity decay of sodium-ion batteries, and extend cycle life.

[0062] This invention provides a method for preparing the metal hydroxide precursor as described above, comprising the following steps:

[0063] S1, prepare a mixed metal salt solution, a precipitant solution, and a complexing agent solution;

[0064] S2, under a protective atmosphere, a precipitant solution and a complexing agent solution are passed through water to prepare a mother liquor;

[0065] S3, a mixed metal salt solution, a precipitant solution and a complexing agent solution are introduced concurrently into the mother liquor to carry out a co-precipitation reaction, thereby obtaining a metal hydroxide precursor.

[0066] Among them, the mixed metal salt solution, precipitant solution and complexing agent solution flowing in in parallel satisfy the flow coefficient K=Q3 / (Q1+Q2), where Q1 is the flow rate of the mixed metal salt solution, Q2 is the flow rate of the precipitant solution, Q3 is the flow rate of the complexing agent solution, and K is 0.08~0.1.

[0067] In step S1, it is understood that the mixed metal salt solution is prepared by mixing a soluble metal salt with a solvent, and the soluble metal salt includes, but is not limited to, nitrates, hydrochlorides, and sulfates.

[0068] In one embodiment of the present invention, the total metal ion concentration in the mixed metal salt solution is preferably 0.1 mol / L to 3 mol / L, including but not limited to any one of 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, and 3 mol / L or any range between two of them. Specifically, the metal ions in the mixed metal salt solution include, but are not limited to, nickel ions, magnesium ions, and manganese ions.

[0069] In one embodiment of the present invention, the concentration of the precipitant solution is preferably 0.1 mol / L to 5 mol / L, including but not limited to any one of 0.1 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, and 5 mol / L or any range between two of them. Specifically, the precipitant includes but is not limited to sodium hydroxide.

[0070] In one embodiment of the present invention, the concentration of the complexing agent solution is preferably 1 g / L to 5 g / L, including but not limited to any one of 1 g / L, 2 g / L, 3 g / L, 4 g / L, and 5 g / L or any range between two. Specifically, the complexing agent includes but is not limited to at least one of ammonia, ammonium sulfate, ethylenediaminetetraacetic acid (EDTA), triethanolamine, ammonium citrate, glycine, sodium citrate, tartaric acid, citric acid, disodium ethylenediaminetetraacetate, ethanolamine, acetic acid, stearic acid, and hydrogen peroxide.

[0071] In step S2, different preparation methods can be used depending on the different devices. For example, pure water is added to the reaction device under stirring conditions, the stirring speed is controlled at 500 rpm to 1500 rpm, the temperature is raised to 40℃ to 70℃, and a precipitant solution and a complexing agent solution are introduced to prepare the mother liquor.

[0072] In one embodiment of the present invention, the pH of the mother liquor is preferably 10 to 14, including but not limited to any one of 10, 11, 12, 13, and 14 or any range between two of them.

[0073] In one embodiment of the present invention, the protective atmosphere is preferably an inert gas.

[0074] In step S3, the present invention optimizes the traditional co - precipitation process. By coordinately controlling the feeding flow rates of the mixed metal salt solution, the precipitant solution, and the complexing agent solution to satisfy a specific flow coefficient K, it effectively improves the problem of uneven element distribution during the synthesis process, thereby fundamentally stabilizing the structural morphology of the metal hydroxide precursor, achieving structural coordinated regulation, being beneficial to further reducing the production cost of the battery cathode material precursor, and simultaneously improving the cycle performance of the battery.

[0075] It can be understood that the present invention does not limit the specific flow rates of the mixed metal salt solution, the precipitant solution, and the complexing agent solution. As long as the three satisfy the flow coefficient K = Q3 / (Q1 + Q2), where the flow coefficient K includes but is not limited to any value of 0.08, 0.09, 0.1 or the range value between any two of them.

[0076] In an embodiment of the present invention, when 0.08 ≤ K ≤ 0.09, the temperature of the co - precipitation reaction is 50°C < T ≤ 60°C, or when 0.09 < K ≤ 0.1, the temperature of the co - precipitation reaction is 60°C < T ≤ 70°C. On the basis of satisfying the specific flow coefficient K, by coordinately regulating the temperature of the co - precipitation reaction, it is beneficial to further control the balance between complexation and precipitation, thereby achieving the optimized regulation of the element distribution and morphology modification of the metal hydroxide precursor.

[0077] In an embodiment of the present invention, when 0.08 ≤ K ≤ 0.09, the pH is 10.5 - 11.0, or when 0.09 < K ≤ 0.1, the pH is greater than or equal to 10.0 and less than 10.5. On the basis of satisfying the specific flow coefficient K, by coordinately regulating the pH of the co - precipitation reaction, it is beneficial to further control the balance between complexation and precipitation, thereby achieving the optimized regulation of the element distribution and morphology modification of the metal hydroxide precursor.

[0078] In an embodiment of the present invention, when it is monitored that the particle size of the reaction particles reaches 2.5μm - 4.5μm, the feeding can be stopped and the reaction can be ended, which is beneficial to controlling the size of the metal hydroxide precursor obtained.

[0079] It can be understood that after the reaction ends, the reaction product can be subjected to alkali washing, water washing, centrifugation, then drying, pulverization, and sieving according to conventional techniques, and the present invention will not elaborate on this.

[0080] The present invention provides a cathode material obtained from the metal hydroxide precursor as described above.

[0081] Using the metal hydroxide precursor of the present invention to prepare the cathode material can not only effectively improve the element distribution uniformity and structural stability of the cathode material, enhance the cycle performance and rate performance, but also be beneficial to improving the production efficiency and reducing the production cost of the cathode material.

[0082] It should be noted that the preparation method of the cathode material is based on existing methods, and will not be described in detail in this invention.

[0083] The present invention also provides a positive electrode sheet and a secondary battery including the positive electrode sheet.

[0084] The positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on the surface of the positive current collector, wherein the positive electrode material layer includes the positive electrode material as described above.

[0085] It is understood that the positive electrode material layer also includes conductive agents and binders, and this invention does not limit this. The secondary battery includes, but is not limited to, lithium-ion batteries and sodium-ion batteries, and the secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.

[0086] The following specific examples will further illustrate the metal hydroxide precursor, its preparation method, and its applications. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0087] Example 1

[0088] Nickel sulfate, magnesium sulfate, and manganese sulfate were mixed to prepare a mixed metal salt solution with a total metal ion concentration of 1.9 mol / L. The molar ratio of nickel ions, magnesium ions, and manganese ions in this mixed metal salt solution was 0.20:0.05:0.75. Ammonia water was used to prepare a complexing agent solution with a concentration of 4 g / L, and sodium hydroxide was used to prepare a precipitant solution with a concentration of 5 mol / L.

[0089] Inject 80% of the effective volume of pure water into the reactor as the base liquid, and purge nitrogen gas to ensure an inert environment inside the reactor. Turn on the reactor agitator and raise the temperature to 60°C. Introduce complexing agent solution and precipitant solution to form mother liquor, and adjust the pH of the mother liquor to 12.0.

[0090] The complexing agent solution, precipitant solution, and mixed metal salt solution were added in parallel to the reaction vessel containing the mother liquor at a flow coefficient of K=0.088. The co-precipitation reaction was carried out under a nitrogen atmosphere and a temperature of 60°C. During the co-precipitation reaction, the pH was maintained at 10.7±0.1, the stirring speed was maintained at 500 rpm, and the material was continuously fed, purged, and concentrated. After the particle size reached 3.5 μm, the feeding was stopped and the material was produced.

[0091] After washing, drying and sieving, a product with the structural formula Ni was obtained. 0.20 Mg 0.05 Mn0.75 (OH)2 precursor materials. For example... Figure 1 and Figure 2 As shown, the primary particles of the precursor material have a slender wedge-shaped structure, and the secondary particles obtained by stacking the primary particles are spherical or near-spherical, with a radial pattern inside the crystal.

[0092] Example 2

[0093] Nickel sulfate, magnesium sulfate, and manganese sulfate were mixed to prepare a mixed metal salt solution with a total metal ion concentration of 1.9 mol / L. The molar ratio of nickel ions, magnesium ions, and manganese ions in this mixed metal salt solution was 0.28:0.05:0.67. Ammonia water was used to prepare a complexing agent solution with a concentration of 4 g / L, and sodium hydroxide was used to prepare a precipitant solution with a concentration of 5 mol / L.

[0094] Inject 80% of the effective volume of pure water into the reactor as the base liquid, and purge nitrogen gas to ensure an inert environment inside the reactor. Turn on the reactor agitator and raise the temperature to 55°C. Introduce complexing agent solution and precipitant solution to form mother liquor, and adjust the pH of the mother liquor to 12.0.

[0095] The complexing agent solution, precipitant solution, and mixed metal salt solution were added in parallel to the reaction vessel containing the mother liquor at a flow coefficient of K=0.10. The co-precipitation reaction was carried out under a nitrogen atmosphere and a temperature of 70°C. During the co-precipitation reaction, the pH was maintained at 10.3±0.1, and the stirring speed was maintained at 600 rpm. Feeding was continuously carried out to clear and concentrate the material. After the particle size reached 3.5μm, feeding was stopped and the material was produced.

[0096] After washing, drying and sieving, a product with the structural formula Ni was obtained. 0.28 Mg 0.05 Mn 0.67 (OH)2 precursor materials. For example... Figure 3 and Figure 4 As shown, the primary particles of the precursor material are lath-shaped, and the secondary particles obtained by stacking the primary particles are spherical or near-spherical, with a radial pattern inside the crystal.

[0097] Example 3

[0098] Nickel sulfate, magnesium sulfate, and manganese sulfate were mixed to prepare a mixed metal salt solution with a total metal ion concentration of 1.6 mol / L. The molar ratio of nickel ions, magnesium ions, and manganese ions in this mixed metal salt solution was 0.24:0.04:0.72. Ammonium sulfate was used to prepare a complexing agent solution with a concentration of 5 g / L, and sodium hydroxide was used to prepare a precipitant solution with a concentration of 4.8 mol / L.

[0099] Inject 80% of the effective volume of pure water into the reactor as the base liquid, and purge nitrogen gas to ensure an inert environment inside the reactor. Turn on the reactor agitator and raise the temperature to 40°C. Introduce complexing agent solution and precipitant solution to form mother liquor, and adjust the pH of the mother liquor to 11.5.

[0100] The complexing agent solution, precipitant solution, and mixed metal salt solution were added in parallel to the reaction vessel containing the mother liquor at a flow coefficient of K=0.092. The co-precipitation reaction was carried out under a nitrogen atmosphere and a temperature of 65°C. During the co-precipitation reaction, the pH was maintained at 10.5±0.1, the stirring speed was maintained at 600 rpm, and the material was continuously fed, purged, and concentrated. After the particle size reached 3.5μm, the feeding was stopped and the material was produced.

[0101] After washing, drying and sieving, a product with the structural formula Ni was obtained. 0.24 Mg 0.04 Mn 0.72 (OH)2 precursor material.

[0102] Example 4

[0103] Nickel sulfate, magnesium sulfate, and manganese sulfate were mixed to prepare a mixed metal salt solution with a total metal ion concentration of 2.1 mol / L. The molar ratio of nickel ions, magnesium ions, and manganese ions in this mixed metal salt solution was 0.3:0.06:0.64. Citric acid was used to prepare a complexing agent solution with a concentration of 4 g / L, and sodium hydroxide was used to prepare a precipitant solution with a concentration of 4.9 mol / L.

[0104] Inject 80% of the effective volume of pure water into the reactor as the base liquid, and purge nitrogen gas to ensure an inert environment inside the reactor. Turn on the reactor agitator and raise the temperature to 70°C. Introduce complexing agent solution and precipitant solution to form mother liquor, and adjust the pH of the mother liquor to 12.8.

[0105] The complexing agent solution, precipitant solution, and mixed metal salt solution were added in parallel to the reaction vessel containing the mother liquor at a flow coefficient of K=0.085. The co-precipitation reaction was carried out under a nitrogen atmosphere and a temperature of 55°C. During the co-precipitation reaction, the pH was maintained at 11±0.1 and the stirring speed was maintained at 600 rpm. Feeding was continuously carried out to clear and concentrate the material. After the particle size reached 3.5 μm, feeding was stopped and the material was produced.

[0106] After washing, drying and sieving, a product with the structural formula Ni was obtained. 0.3 Mg 0.06 Mn 0.64 (OH)2 precursor material.

[0107] Comparative Example 1

[0108] The difference between Comparative Example 1 and Example 2 is that when the complexing agent solution, precipitant solution and mixed metal salt solution are added in parallel to the reaction vessel containing the mother liquor, the flow coefficient K = 0.064.

[0109] The morphology of the metal hydroxide precursor prepared in this comparative example is as follows: Figure 5 As shown.

[0110] Comparative Example 2

[0111] The difference between Comparative Example 2 and Example 2 is that when the complexing agent solution, precipitant solution and mixed metal salt solution are added in parallel to the reaction vessel containing the mother liquor, the flow coefficient K = 0.076.

[0112] The morphology of the metal hydroxide precursor prepared in this comparative example is as follows: Figure 6 As shown.

[0113] Comparative Example 3

[0114] The difference between Comparative Example 3 and Example 2 is that when the complexing agent solution, precipitant solution and mixed metal salt solution are added in parallel to the reaction vessel containing the mother liquor, the flow coefficient K = 0.12.

[0115] The morphology of the metal hydroxide precursor prepared in this comparative example is as follows: Figure 7 As shown.

[0116] The metal hydroxide precursors prepared in all examples and comparative examples were characterized and tested, and the results are shown in Tables 1 and 2.

[0117] Table 1

[0118]

[0119] Table 2

[0120]

[0121] Based on the preparation method and Tables 1 and 2, it can be seen that Comparative Example 1 has a large deviation in element ratio due to the flow coefficient being lower than 0.08. Although the aspect ratio and sphericity of the primary particles seem to meet the requirements, the insufficient degree of complexation prevents the elements from being completely complexed and precipitated, resulting in a large difference between the actual element ratio and the target element ratio. The thickness of the primary particles is also significantly thinner. Therefore, the precursor product prepared in Comparative Example 1 is still unqualified.

[0122] Application examples

[0123] All the precursor materials prepared in the examples and comparative examples were mixed with anhydrous sodium carbonate at a mass ratio of 3:1 and sintered at 900°C for 16 hours to obtain sodium-ion battery cathode materials.

[0124] Battery Assembly and Performance Testing: Sodium-ion cathode material, conductive carbon black, and PVDF binder were weighed at a mass ratio of 8:1:1 and uniformly dispersed in N-methylpyrrolidone (NMP) to prepare a conductive slurry. This slurry was then coated onto aluminum foil, dried at 70°C, cut, and weighed to prepare coin cell cathode sheets. Finally, these sheets were assembled with sodium foil to form coin cell sodium-ion batteries. Charge-discharge cycle tests were conducted at 0.1C rate, and the results are shown in Table 3.

[0125] Table 3

[0126]

[0127] As shown in Table 3, the cathode material obtained by using the precursor provided by this invention can improve the cycle performance of sodium-ion batteries, reduce capacity decay, and extend battery life.

[0128] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0129] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A metal hydroxide precursor, characterized in that, The metal hydroxide precursor includes secondary particles composed of a plurality of primary particles, where: The primary particles are plate-like, and the aspect ratio of length to width is greater than or equal to 3:1; The sphericity of the secondary particles is greater than or equal to 0.

7.

2. The metal hydroxide precursor according to claim 1, characterized in that, The metal hydroxide precursor also satisfies at least one of the following conditions: (1) The aspect ratio of length to width of the primary particles is 3:1 to 8:1; (2) The thickness of the primary particles is 50 nm to 150 nm; (3) The sphericity of the secondary particles is 0.7 to 0.9; (4) The ratio of the XRD diffraction peak intensities of the (101) and (001) crystal planes in the metal hydroxide precursor is 2.0 to 2.4; (5) The median particle size of the metal hydroxide precursor is 3 μm to 10 μm; (6) The tap density of the metal hydroxide precursor is 1.2 g / cm³. 3 ~1.6g / cm 3 ; (7) The specific surface area of ​​the metal hydroxide precursor is 10 m². 2 / g~30m 2 / g; (8) The chemical formula of the metal hydroxide precursor is Ni x M y Mn 1-x-y (OH)2, wherein 0.01≤x≤0.8, 0.01≤y≤0.08, and M is selected from one or more of Cu, Co, Zn, Mg, Cr, and Zr.

3. A method for preparing a metal hydroxide precursor as described in claim 1 or 2, characterized in that, It includes the following steps: Prepare a mixed metal salt solution, a precipitant solution, and a complexing agent solution; Under a protective atmosphere, introduce the precipitant solution and the complexing agent solution into water to form a mother liquor; Introduce the mixed metal salt solution, the precipitant solution, and the complexing agent solution into the mother liquor in parallel flow to carry out a coprecipitation reaction to obtain the metal hydroxide precursor; Among them, the mixed metal salt solution, the precipitant solution, and the complexing agent solution introduced in parallel flow satisfy the flow coefficient K = Q3 / (Q1 + Q2), where Q1 is the flow rate of the mixed metal salt solution, Q2 is the flow rate of the precipitant solution, Q3 is the flow rate of the complexing agent solution, and K is 0.08 to 0.

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4. The method for preparing the metal hydroxide precursor according to claim 3, characterized in that, The flow coefficient K and the temperature of the coprecipitation reaction satisfy: When 0.08 ≤ K ≤ 0.09, the temperature of the coprecipitation reaction is 50°C < T ≤ 60°C; Or, when 0.09 < K ≤ 0.1, the temperature of the coprecipitation reaction is 60°C < T ≤ 70°C.

5. The method for preparing the metal hydroxide precursor according to claim 3, characterized in that, The flow coefficient K and the pH of the coprecipitation reaction satisfy: When 0.08 ≤ K ≤ 0.09, the pH is 10.5 to 11.0; Or, when 0.09 < K ≤ 0.1, the pH is greater than or equal to 10.0 and less than 10.

5.

6. The method for preparing the metal hydroxide precursor according to any one of claims 3 to 5, characterized in that, The step of preparing the mixed metal salt solution, the precipitant solution, and the complexing agent solution satisfies at least one of the following conditions: (1) The total metal ion concentration in the mixed metal salt solution is 0.1 mol / L to 3 mol / L; (2) The concentration of the precipitant solution is 0.1 mol / L to 5 mol / L; (3) The concentration of the complexing agent solution is 1 g / L to 5 g / L.

7. The method for preparing the metal hydroxide precursor according to any one of claims 3 to 5, characterized in that, The step of preparing the mother liquor satisfies at least one of the following conditions: (1) The pH of the mother liquor is 10 to 14; (2) The temperature is 40°C to 70°C. A positive electrode material obtained from the metal hydroxide precursor according to claim 1 or 2.

9. A positive electrode plate, 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 8.

10. A secondary battery, characterized in that, It includes the positive electrode sheet according to claim 9.

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