Positive electrode material precursor and preparation method and application thereof

Abstract

The invention relates to the technical field of battery materials, and provides a positive electrode material precursor and a preparation method and application thereof. The preparation method comprises the following steps: adding a metal mixed salt solution, a second zinc salt solution, a complexing agent solution and a precipitant solution into a base solution, and carrying out a first coprecipitation reaction; and adjusting the pH value, switching to a first zinc salt solution, adding the first zinc salt solution into the first nucleation slurry, carrying out a second co-precipitation reaction, and carrying out solid-liquid separation to obtain a first positive electrode material precursor. The relatively low zinc salt solution is used for nucleation, and the relatively high zinc salt solution is used for rapid growth of crystal nuclei, so that zinc ions are not easy to separate out in the coprecipitation process, and the first positive electrode material precursor with uniformly distributed zinc ions is obtained.

Description

Technical Field

[0001] The present application belongs to the technical field of battery materials, and in particular relates to a positive electrode material precursor and a preparation method and application thereof. Background Art

[0002] As a new type of green power source, sodium-ion batteries have been widely used in 3C digital electronic products, power tools, electric vehicles, energy storage and other fields. In recent years, with the development of new energy vehicles, higher and higher requirements have been placed on the capacity, cycle and high-rate discharge performance of sodium-ion batteries. Positive electrode materials are one of the factors that affect the performance of sodium-ion batteries, so more types of positive electrode materials have been widely developed. Among them, layered oxide positive electrode materials have shown better specific capacity and voltage advantages, and have inherent cost advantages. On the one hand, this is because such materials can draw on the highly mature solid-phase method or co-precipitation method in lithium-ion batteries to achieve low-cost large-scale production; on the other hand, it is because they have a wealth of active elements to choose from.

[0003] However, the improvement of the high specific capacity performance of cathode materials is still lagging behind. At present, researchers have conducted many modification explorations around layered oxide cathode materials. The commonly seen doping modification method is generally to modify the cathode material end, but there are certain limitations, such as poor doping uniformity, high energy consumption and numerous processes, which makes it difficult to improve the overall specific capacity of the cathode material. Summary of the invention

[0004] The purpose of the present application is to provide a positive electrode material precursor and a preparation method and application thereof, aiming to solve the problem of poor uniformity of element distribution in the positive electrode material precursor.

[0005] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In a first aspect, the present application provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0007] Prepare a metal mixed salt solution, a zinc salt solution, a complexing agent solution and a precipitant solution, wherein the metal mixed salt solution contains nickel, iron and manganese, and the zinc salt solution includes a first zinc salt solution and a second zinc salt solution, wherein the concentration of the first zinc salt solution is greater than that of the second zinc salt solution;

[0008] Adding the metal mixed salt solution, the second zinc salt solution, the complexing agent solution and the precipitant solution into the bottom liquid to carry out a first coprecipitation reaction to obtain a first nucleation slurry;

[0009] The pH value of the first nucleation slurry is adjusted to a first preset pH value, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first nucleation slurry to perform a second coprecipitation reaction to obtain a first growth slurry;

[0010] The first growth slurry is separated into solid and liquid to obtain a first positive electrode material precursor.

[0011] In a second aspect, the present application provides a positive electrode material precursor, wherein the positive electrode material precursor is a secondary particle formed by stacking needle-shaped primary particles, and the chemical formula of the positive electrode material precursor is Ni a Fe b Mn c Zn d (OH)2, where: 0.2≤a≤0.3, 0.3≤b≤0.4, 0.35≤c≤0.45, 0.02≤d≤0.15.

[0012] In a third aspect, the present application provides a positive electrode material, which is prepared by mixing the positive electrode material precursor provided by the preparation method of the positive electrode material precursor provided by the first aspect and / or the positive electrode material precursor provided by the second aspect with a sodium salt.

[0013] In a fourth aspect, the present application provides a secondary battery, and the secondary battery includes the positive electrode material of the present application.

[0014] The preparation method of the positive electrode material precursor provided in the first aspect of the present application, adopts a relatively low concentration of zinc salt solution and a metal mixed salt solution, a complexing agent solution, and a precipitant solution to be added to the bottom liquid for coprecipitation reaction, and the mixed metal salt containing nickel, iron and manganese is converted into a hydroxide with a zinc salt to form a crystal nucleus, and at this time, a relatively low concentration of zinc salt solution is used to make it difficult for zinc ions to precipitate in advance, and it can be synchronized with other metal ions, which is conducive to the uniform distribution of zinc ions in the crystal nucleus; Then a relatively high concentration of zinc salt solution is used for coprecipitation, so that zinc ions can be quickly precipitated with other metal ions, and while achieving rapid growth of the crystal nucleus, it is also conducive to the accumulation of precipitate particles in a relatively dense manner, thereby effectively improving the tap density of the first positive electrode material precursor. Therefore, the present application adopts a relatively low concentration of zinc salt solution for nucleation, and adopts a relatively high concentration of zinc salt solution for growth, so that zinc ions are not easy to precipitate during the coprecipitation process, thereby obtaining a first positive electrode material precursor with uniform distribution of zinc ions.

[0015] The positive electrode material precursor provided in the second aspect of the present application is nickel-zinc-iron-manganese hydroxide, which has the characteristics of good sphericity and uniform distribution of zinc ions, which is beneficial to improving the electrochemical performance of the prepared positive electrode material.

[0016] The third aspect of the present application provides a cathode precursor material obtained by sintering a sodium source and the above-mentioned cathode precursor material. The cathode precursor material is nickel-zinc-iron-manganese hydroxide, which has the characteristics of good sphericity and uniform distribution of zinc ions. Therefore, the cathode material obtained by sintering it with a sodium source has higher specific capacity, cycle stability, structural stability and other characteristics.

[0017] The secondary battery provided in the fourth aspect of the present application includes the above-mentioned positive electrode material, which has high gram capacity, cycle stability, structural stability and other characteristics, thereby improving the energy density, cycle stability, and safety performance of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying any creative work.

[0019] Figure 1 is a SEM photograph of the cathode material precursor provided in Example 1 of the present application;

[0020] Figure 2 is a SEM photograph of the cathode material precursor provided in Example 2 of the present application;

[0021] Figure 3 This is a SEM photograph of the positive electrode material precursor provided in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0024] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0025] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0026] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0027] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0028] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0029] It should be noted that:

[0030] Tap density refers to the mass per unit volume of powder in a container measured after being tapped under specified conditions. Tap density is defined as the mass of the sample divided by its volume, which includes the sample itself and the sample pores and sample gap volume.

[0031] Specific surface area refers to the surface area per unit mass of a porous solid material. It is usually measured by low-temperature nitrogen adsorption method, using the BET theory.

[0032] "D50" refers to the particle size corresponding to 50% of the cumulative volume distribution percentage in the particle size distribution, calculated from the small particle size side. Similarly, "D10" and "D90" refer to the particle sizes corresponding to 10% and 90% of the cumulative volume distribution percentage in the particle size distribution, calculated from the small particle size side. The determination method of D10, D50 and D90 particle sizes can refer to GB / T19077-2016 particle size distribution laser diffraction method, such as using Malvern 2000 (MasterSizer 2000) laser particle size analyzer for testing.

[0033] The base liquid refers to the solution system that serves as the reaction medium during the coprecipitation reaction.

[0034] A first aspect of an embodiment of the present application provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0035] Step S10, preparing a metal mixed salt solution, a zinc salt solution, a complexing agent solution and a precipitant solution, wherein the metal mixed salt solution contains nickel, iron and manganese, and the zinc salt solution includes a first zinc salt solution and a second zinc salt solution, and the concentration of the first zinc salt solution is greater than that of the second zinc salt solution;

[0036] Step S20, adding the metal mixed salt solution, the second zinc salt solution, the complexing agent solution and the precipitant solution into the bottom liquid to carry out a first co-precipitation reaction to obtain a first nucleation slurry;

[0037] Step S30, adjusting the pH value of the first nucleation slurry to a first preset pH value, stopping the addition of the second zinc salt solution, adding the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution to the first nucleation slurry, performing a second coprecipitation reaction, and obtaining a first growth slurry;

[0038] The second growth slurry is separated into solid and liquid to obtain a first positive electrode material precursor.

[0039] The preparation method of the positive electrode material precursor provided by the first aspect of the embodiment of the present application, after preparing a metal mixed salt solution containing nickel, iron and manganese and a zinc salt solution of different concentrations, the metal mixed salt solution, the zinc salt solution with a lower concentration, the precipitant solution and the complexing agent solution are added to the bottom liquid for coprecipitation reaction, and the zinc ions and the nickel, iron and manganese salt are converted into hydroxides to form initial crystal nuclei by the complexing action of the complexing agent and the coprecipitation action of the precipitant during the reaction. Since a relatively low concentration of zinc salt solution is used, the zinc ions are not easy to precipitate prematurely, and can be precipitated synchronously with other metal ions, so that the zinc ions are evenly distributed in the initial crystal nuclei. After the initial nucleation is completed, the pH value of the reaction slurry is adjusted, and the zinc salt solution with a lower concentration is switched to a zinc salt solution with a higher concentration to continue the coprecipitation reaction, so that the zinc ions can be precipitated synchronously and rapidly with other metal ions, and the rapid growth of the crystal nucleus is achieved, while also facilitating the accumulation of the precipitate particles in a denser manner, thereby effectively improving the tap density of the first positive electrode material precursor. Therefore, the present application adopts a lower concentration zinc salt solution for nucleation and a higher concentration zinc salt solution for growth, so that zinc ions are not easily precipitated during the coprecipitation process, thereby obtaining a first positive electrode material precursor with uniformly distributed zinc ions.

[0040] In some embodiments, before the first growth slurry is separated into solid and liquid, the following steps are further included:

[0041] Step S40, when the precipitate in the first growth slurry reaches a first predetermined particle size, adjusting the pH value of the first growth slurry to a second preset pH value, stopping the addition of the first zinc salt solution, adding the second zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution to the first growth slurry, performing a third coprecipitation reaction, and obtaining a second nucleation slurry;

[0042] Step S50, adjusting the pH value of the second nucleation slurry to a third preset pH value, stopping the addition of the second zinc salt solution, adding the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution to the second nucleation slurry, and performing a fourth coprecipitation reaction, and when the precipitate reaches a second predetermined particle size, stopping the addition of the metal mixed salt solution, the complexing agent solution, the precipitant solution and the first zinc salt solution to obtain a second growth slurry;

[0043] The second growth slurry is separated into solid and liquid to obtain a second positive electrode material precursor.

[0044] By real-time monitoring of the particle size of the precipitate in the reaction system, when the precipitate reaches a certain particle size, switching to a zinc salt solution with a lower concentration to continue the co-precipitation reaction, at this time, the crystal nuclei after one growth show a trend of agglomeration, gradual dispersion, particle adsorption, and re-nucleation, thereby obtaining a second crystal nucleus with a wider particle size distribution, which is beneficial to the accumulation of the second crystal nucleus particles. Finally, a zinc salt solution with a higher concentration is used for the co-precipitation reaction, which not only allows the second crystal nucleus to grow smoothly, but also because the second crystal nucleus has a wider particle size distribution, it is beneficial to the accumulation of the second crystal nucleus particles, such as the second crystal nucleus with a smaller particle size is filled in the pores of the second crystal nucleus with a larger particle size, or multiple second crystal nuclei are accumulated, thereby obtaining a second positive electrode material precursor with a compact structure, high tap density and wide particle size distribution.

[0045] In the embodiment of the present application, a low-concentration zinc salt solution is used for a coprecipitation reaction to obtain an initial crystal nucleus, and then a high-concentration zinc salt solution is used for a coprecipitation reaction to achieve the growth of the initial crystal nucleus, and then a low-concentration zinc salt solution is used for secondary nucleation to obtain a second crystal nucleus, and finally a high-concentration zinc salt solution is used for a coprecipitation reaction to achieve the growth of the second crystal nucleus, thereby making the nickel, zinc, iron and manganese elements evenly distributed, especially the zinc ions are evenly distributed in the precursor particles, thereby obtaining a positive electrode material precursor with a wide particle size distribution and a high tap density.

[0046] In some embodiments, in step S10, the total concentration of nickel, iron and manganese in the metal mixed salt solution is 1mol / L-2.5mol / L. The metal mixed salt solution is a mixed solution of nickel salt, iron salt and manganese salt. The embodiment of the present application controls the concentration of the metal mixed salt solution within the above range, so that the nucleation rate and growth rate of the precursor particles can be regulated. Within this concentration range, it is beneficial for each metal raw material to fully contact and react with the complexing agent and the precipitant to generate a precursor nucleus, and to achieve the synchronous precipitation of zinc ions and other metal ions. Specifically, the total molar concentration of the nickel source, iron source and manganese source in the metal mixed salt solution can be 1mol / L, 1.5mol / L, 1.8mol / L, 2mol / L, 2.3mol / L, 2.5mol / L and other typical but non-restrictive values.

[0047] The nickel salt is a soluble nickel salt, which may be at least one of nickel sulfate, nickel nitrate, nickel acetate, and nickel chlorate; the iron salt is a soluble iron salt, which may be at least one of ferrous sulfate, ferrous nitrate, and ferrous chlorate; the manganese salt is a soluble manganese salt, which may be at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chlorate. Specifically, the corresponding soluble salts may be dissolved in water to form a metal mixed salt solution. In order to further improve the compatibility of the coprecipitation reaction, the types of soluble salts in the metal mixed salt solution are also the same, and the nickel salt in the metal mixed salt solution is selected as nickel sulfate, and the iron salt is selected as ferrous sulfate.

[0048] In some embodiments, in step S10, the concentration of zinc ions in the first zinc salt solution is 0.35mol / L-0.65mol / L, and the molar concentration ratio of zinc ions in the first zinc salt solution to the molar concentration ratio of zinc ions in the second zinc salt solution is 1:0.1-0.5. Exemplarily, the concentration of zinc ions in the first zinc salt solution can be 0.35mol / L, 0.4mol / L, 0.45mol / L, 0.5mol / L, 0.55mol / L, 0.6mol / L, 0.65mol / L and other typical but non-limiting values. The molar concentration ratio of zinc ions in the first zinc salt solution to the molar concentration ratio of zinc ions in the second zinc salt solution can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5 and other typical but non-limiting values.

[0049] In the first zinc salt solution and the second zinc salt solution provided in the embodiment of the present application, the zinc salt is a soluble zinc salt, which can be at least one of zinc sulfate, zinc nitrate, and zinc chlorate. In order to further improve the compatibility of the coprecipitation reaction, the types of soluble salts in the first zinc salt solution and the second zinc salt solution are also the same, for example, the zinc salt in the first zinc salt solution is zinc sulfate, and the corresponding zinc salt in the second zinc salt solution is zinc sulfate.

[0050] In the embodiment of the present application, zinc salt solutions of different concentrations are used alternately for coprecipitation reaction. Specifically, a low-solubility zinc salt solution is used for coprecipitation reaction to promote nucleation. In this way, the premature precipitation of zinc ions is reduced in the process of forming crystal nuclei, which is beneficial to the synchronous precipitation of zinc ions and other metal ions; a high-concentration zinc salt solution is used for coprecipitation reaction to promote the growth of crystal nuclei, and the synchronous precipitation of zinc ions and other metal ions is achieved, so as to obtain a positive electrode material precursor with a wide particle size distribution and a high tap density.

[0051] In some embodiments, in step S10, the precipitant contained in the precipitant solution includes at least one of sodium hydroxide, potassium hydroxide and sodium carbonate.

[0052] Coprecipitation refers to the presence of two or more cations in a solution, which exist in a homogeneous phase in the solution. After adding a precipitant, a uniform precipitate of various components can be obtained after a coprecipitation reaction. In this application, the OH of the metal cation in alkaline conditions - Under the action of ions, it dissociates and precipitates to form hydroxide.

[0053] In some embodiments, in step S10, the concentration of the precipitant solution is 5-10.5 mol / L. Exemplarily, the concentration of the precipitant solution can be 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 10.5 mol / L, and other typical but non-limiting values.

[0054] The precipitant can react with metal ions to generate a quaternary cathode material precursor. The embodiment of the present application optimizes and controls the concentration of the precipitant solution to adjust the nucleation rate and growth rate of the precursor, thereby obtaining dense precursor particles. If the concentration is too low, it is not conducive to the contact reaction between the various metal raw material components and the precipitant to form crystal nuclei; if the concentration is too high, it will cause premature nucleation of the grains, which is not conducive to the control of the precursor crystal structure.

[0055] In some embodiments, in step S10, the complexing agent contained in the complexing agent solution includes at least one of ammonia water, citric acid and sodium oxalate.

[0056] The complexing agent provided in the present application can undergo a complexing reaction with metal ions, thereby adjusting the growth rate of the precursor crystal nucleus, and further obtaining precursor particles with a wide particle size distribution and a high tap density.

[0057] In some embodiments, in step S10, the concentration of the complexing agent solution is 4-15 mol / L. Exemplarily, the concentration of the complexing agent solution can be 4 mol / L, 5 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, 12 mol / L, 15 mol / L, etc., which are typical but non-limiting values.

[0058] In the coprecipitation reaction process, the metal ions first react with the complexing agent, and then react with the precipitant to form a nickel-zinc-iron-manganese quaternary positive electrode material precursor. The embodiment of the present application adjusts the concentration of the complexing agent solution to adjust the nucleation rate and growth rate of the precursor, thereby obtaining dense precursor particles.

[0059] In some embodiments, in step S10, the molar ratio of nickel ions, ferrous ions, manganese ions in the metal mixed salt solution to zinc ions in the zinc salt solution is 20-30: 30-40: 35-45: 2-15. Exemplarily, the molar ratio of nickel ions can be 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, etc. Typical but non-limiting values. The molar ratio of ferrous ions can be 30, 31, 32, 33, 34, 35, 36, 37, 28, 39, 40, etc. Typical but non-limiting values. The molar ratio of manganese ions can be 35, 36, 37, 28, 39, 40, 41, 42, 43, 44, 45, etc. Typical but non-limiting values. The molar ratio of zinc ions can be 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 15, etc. Typical but non-limiting values.

[0060] By controlling the molar ratios of nickel ions, ferrous ions, manganese ions and zinc ions, nickel-zinc-iron-manganese precursors with different ratios can be prepared.

[0061] In some embodiments, in step S10, the concentration of ammonium ions in the base solution is 1-3 g / L, and the pH is 11-12.5. Exemplarily, the concentration of ammonium ions can be typical but non-limiting values ​​such as 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, etc. The pH value of the base solution can be typical but non-limiting values ​​such as 11, 11.5, 12, 12.5, etc.

[0062] The base liquid can provide a stable pH environment, which not only enables the coprecipitation reaction to proceed stably and controllably, but also facilitates the uniform dispersion and mixing of the component materials, provides a buffering effect, and prepares precursor particles with high tap density and wide particle size distribution.

[0063] In some embodiments, in step S10, the base liquid is placed in a reaction container with a certain accommodation space, and specifically, the volume of the base liquid can be 1 / 5-1 / 2 of the effective volume of the reaction container. Specifically, the amount of base liquid added can be typical but non-limiting values ​​such as 1 / 5, 1 / 4, 1 / 3, and 1 / 2 of the effective volume of the reaction container.

[0064] In some embodiments, in step S20, the metal mixed salt solution, the second zinc salt solution, the precipitant solution, and the complexing agent solution are added to the bottom liquid of the reaction container at a certain flow rate to perform a co-precipitation reaction to form a stable initial crystal nucleus.

[0065] The metal mixed salt solution, the second zinc salt solution, the precipitant solution and the complexing agent solution are fed independently, for example, four peristaltic pumps can be used to feed them separately.

[0066] In some embodiments, in step S20, the conditions of the first coprecipitation reaction include: a reaction temperature of 30°C-60°C, a stirring speed of 150rpm-500rpm, a reaction time of 4h-10h, and a pH value of 11-12.5. Exemplarily, the reaction temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and other typical but non-limiting values. The stirring speed can be 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, and other typical but non-limiting values. The pH value is 11, 11.2, 11.5, 11.7, 12, 12.5, and other typical but non-limiting values. The reaction time can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, and other typical but non-limiting values.

[0067] Under the above conditions, the metal mixed salt solution containing nickel, iron and manganese, the second zinc salt solution containing zinc, the precipitant and the complexing agent fully react to generate the initial crystal nuclei of the positive electrode material precursor containing nickel, zinc, iron and manganese.

[0068] In some embodiments, in step S20, in the first co-precipitation reaction, the flow rate of the metal mixed salt solution is the same as the flow rate of the second zinc salt solution.

[0069] The second zinc salt solution is used to carry out a coprecipitation reaction with the metal mixed salt, so that the zinc ions can be precipitated simultaneously with the nickel, iron and manganese, and a crystal nucleus with uniform zinc ion distribution is obtained. The main reason for this is that the concentration of the second zinc salt solution is relatively low, and the flow rate of the metal mixed salt solution is controlled to be the same as the flow rate of the second zinc salt solution, so that the total amount of zinc ions per unit time remains unchanged, and the zinc ions are not easy to precipitate prematurely under the pH condition. In this way, the initial crystal nucleus of the precursor with uniform zinc ion distribution can be obtained.

[0070] In some embodiments, in step S20, in the first coprecipitation reaction, the flow rate of the metal mixed salt solution is 150-200mL / min, the flow rate of the complexing agent solution is 5-15mL / min, and the flow rate of the precipitant solution is 100-150mL / min. Exemplarily, the flow rate of the mixed metal salt solution can be 150mL / min, 160mL / min, 170mL / min, 180mL / min, 190mL / min, 200mL / min and other typical but non-limiting values, the flow rate of the complexing agent solution can be 5mL / min, 6mL / min, 7mL / min, 8mL / min, 10mL / min, 12mL / min, 15mL / min and other typical but non-limiting values, and the flow rate of the precipitant solution can be 100mL / min, 110mL / min, 120mL / min, 130mL / min, 140mL / min, 150mL / min and other typical but non-limiting values.

[0071] The flow rate of the precipitant solution can be automatically adjusted according to the pH value of the reaction system, and the flow rate of the complexing agent solution can be adjusted according to the ammonia concentration of the reaction system. For example, the flow rate of the precipitant solution can be adjusted so that the pH value of the reaction system is within the condition of 11-12.5 to achieve the first coprecipitation reaction.

[0072] In some embodiments, in step S30, the pH value of the first nucleation slurry is adjusted to a first preset pH value, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first nucleation slurry to carry out a second co-precipitation reaction to obtain a first growth slurry.

[0073] After the first coprecipitation reaction is carried out for a period of time, the pH value of the reaction system is adjusted to the first pH preset value, the first coprecipitation reaction is terminated, the second zinc salt solution is switched to the first zinc salt solution, and the coprecipitation reaction is continued. During the reaction, due to the change in the pH environment, the precipitation rate of zinc ions is reduced. Therefore, a higher concentration of zinc salt solution is used for the coprecipitation reaction, so that the zinc ions participating in the coprecipitation reaction per unit time match the precipitation amount of nickel, iron and manganese ions, thereby stably and continuously accumulating nickel, zinc, iron and manganese precipitates on the surface of the initial crystal nucleus, thereby achieving a continuous increase in the size of the initial crystal nucleus particles.

[0074] In some embodiments, in step S30, the first preset pH value is 10-11.5. For example, the first preset pH value can be 10, 10.2, 10.4, 10.6, 10.8, 11, 11.2, 11.5, etc., which are typical but non-limiting values.

[0075] Under this pH environment, the precipitation rate of zinc ions decreases. As the concentration of zinc ions increases, the precipitation rates of zinc ions and nickel-iron-manganese ions match, causing the crystal nuclei to grow steadily and obtaining precursor particles with a wide particle size distribution and high density.

[0076] In some embodiments, in step S30, in the second co-precipitation reaction, the flow rate of the metal mixed salt solution is greater than the flow rate of the first zinc salt solution.

[0077] Switching to a higher concentration of the first zinc salt solution for the second coprecipitation reaction allows the crystal nuclei to grow stably and orderly. During the reaction, the solubility of the zinc salt solution is increased and its addition rate is reduced, so that the precipitation rate of zinc ions matches the precipitation rate of nickel, iron and manganese, thereby obtaining precursor particles with uniform distribution of each element.

[0078] In some embodiments, in step S30, in the second coprecipitation reaction, the flow rate ratio of the metal mixed salt solution to the first zinc salt solution is 1:0.1-0.5. Exemplarily, the flow rate ratio of the metal mixed salt solution to the first zinc salt solution is 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc., which are typical but non-limiting values.

[0079] The flow rates of the metal mixed salt solution and the first zinc salt solution are controlled within the above range so that the precipitation rates of zinc ions and nickel iron manganese match, thereby facilitating uniform distribution of each element in the precursor particles.

[0080] In some embodiments, in step S30, in the second coprecipitation reaction, the flow rate of the metal mixed salt solution is 150-200mL / min, the flow rate of the complexing agent solution is 5-15mL / min, and the flow rate of the precipitant solution is 100-150mL / min. Exemplarily, the flow rate of the mixed metal salt solution can be 150mL / min, 160mL / min, 170mL / min, 180mL / min, 190mL / min, 200mL / min and other typical but non-limiting values, the flow rate of the complexing agent solution can be 5mL / min, 6mL / min, 7mL / min, 8mL / min, 10mL / min, 12mL / min, 15mL / min and other typical but non-limiting values, and the flow rate of the precipitant solution can be 100mL / min, 110mL / min, 120mL / min, 130mL / min, 140mL / min, 150mL / min and other typical but non-limiting values.

[0081] The flow rate of the precipitant solution can be automatically adjusted according to the pH value of the reaction system, and the flow rate of the complexing agent solution can be adjusted according to the ammonia concentration of the reaction system. For example, the pH value of the reaction system can be adjusted to 10-11.5 by adjusting the flow rate of the precipitant solution to achieve the second coprecipitation reaction.

[0082] In some embodiments, in step S30, the conditions of the second coprecipitation reaction include: a reaction temperature of 30°C-60°C, and a stirring speed of 150rpm-500rpm. Exemplarily, the reaction temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and other typical but non-limiting values. The stirring speed can be 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, and other typical but non-limiting values.

[0083] By adjusting the temperature, pH, rotation speed, and the speed of adding each raw material liquid during the second co-precipitation process, the growth of the initial crystal nucleus is achieved. The final nickel-zinc-iron-manganese hydroxide precursor not only has a wide particle size distribution and regular morphology, but also has a significantly improved tap density.

[0084] In some embodiments, in step S40, when the precipitate in the first growth slurry reaches a first predetermined particle size, the pH value of the first growth slurry is adjusted to a second preset pH value, the addition of the first zinc salt solution is stopped, and the second zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first growth slurry to perform a third co-precipitation reaction to obtain a second nucleation slurry.

[0085] The reaction is regulated by monitoring the D50 particle size of the precipitate during the coprecipitation reaction. When the D50 particle size of the precipitate meets the first predetermined particle size range, the growth process of the initial crystal nucleus is terminated, the pH environment of the system is adjusted, and the second zinc salt solution with a lower concentration is switched to carry out the coprecipitation reaction. In this process, the crystal nucleus presents a change process of agglomeration-gradual dispersion-particle adsorption-re-nucleation, that is, the crystal nucleus first agglomerates during the reaction to increase the particle size and density of the crystal nucleus, and then due to the continuous reaction, some of the crystal nuclei gradually disperse to make their particle size distribution wider; as the coprecipitation reaction continues, the particles adsorb each other. At this time, due to the wide particle size distribution of the crystal nucleus, the crystal nucleus particles with smaller particle size gradually fill the pores of the crystal nucleus particles with larger particles, thereby realizing the densest packing of the crystal nucleus, so that the re-nucleated crystal nucleus has a higher density, giving the precursor particles a higher tap density.

[0086] In some embodiments, in step S40, the first predetermined particle size D50 is 2 μm-4 μm. For example, the first predetermined particle size D50 can be 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, etc., which are typical but non-limiting values.

[0087] When the particle size of the precipitate particles is within the above range, a secondary nucleation reaction of the precipitate particles is performed, which is beneficial to adjusting the particle size distribution of the precipitate particles, thereby obtaining crystal nuclei with high packing density.

[0088] In some embodiments, in step S40, the second preset pH value is 11.2-11.8. For example, the second preset pH value can be 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, etc., which are typical but non-limiting values.

[0089] Under this pH condition, the morphology of the precipitate particles contained in the reaction system changes, showing a tendency to agglomerate, disperse, re-adsorb, and nucleate, thereby obtaining a second crystal nucleus with a wider particle size distribution and higher density.

[0090] The pH environment of the reaction system is adjusted by increasing the flow rate of the precipitant solution. In the embodiment of the present application, the flow rate of the precipitant solution is increased to 110%-120% of the original flow rate, and the pH value of the reaction system is adjusted to within the second pH preset value range within 30 minutes.

[0091] In some embodiments, in step S40, in the third co-precipitation reaction, the flow rate of the metal mixed salt solution is the same as the flow rate of the second zinc salt solution.

[0092] A second zinc salt solution with a lower concentration is used for coprecipitation reaction, and the flow rate of the metal mixed salt solution is controlled to be the same as the flow rate of the second zinc salt solution. In this way, the total amount of zinc ions per unit time remains unchanged, and the zinc ions are not easy to precipitate prematurely under the pH condition, so that the zinc ions and the nickel-iron-manganese ions are precipitated synchronously, thereby obtaining a precursor second crystal nucleus with uniform zinc ion distribution.

[0093] In some embodiments, in step S40, the conditions of the third coprecipitation reaction include: a reaction temperature of 30°C-60°C, a stirring speed of 150rpm-500rpm, and a reaction time of 2h-15h. Exemplarily, the reaction temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and other typical but non-limiting values. The stirring speed can be 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, and other typical but non-limiting values. The reaction time can be 2h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 12h, 15h, and other typical but non-limiting values.

[0094] The purpose of the first coprecipitation reaction is to form the primary crystal nucleus, the purpose of the second coprecipitation reaction is to grow the primary crystal nucleus, the purpose of the third coprecipitation reaction is to form the second crystal nucleus, and the purpose of the fourth coprecipitation reaction is to grow the second crystal nucleus, thereby obtaining precursor particles with a wider particle size distribution and a higher tap density. In this reaction process, the reaction time T3 of the third coprecipitation reaction and the reaction time T1 of the first coprecipitation are controlled to satisfy: T3 = (0.5-1.5) * T1. Meeting this reaction time allows the crystal nucleus to meet the particle size classification, which is more conducive to the accumulation of the precursor particles, so as to effectively improve the tap density of the precursor particles.

[0095] In some embodiments, in step S40, in the third coprecipitation reaction, the flow rate of the metal mixed salt solution is 150-200mL / min, the flow rate of the complexing agent solution is 5-15mL / min, and the flow rate of the precipitant solution is 100-150mL / min. Exemplarily, the flow rate of the mixed metal salt solution can be 150mL / min, 160mL / min, 170mL / min, 180mL / min, 190mL / min, 200mL / min and other typical but non-limiting values, the flow rate of the complexing agent solution can be 5mL / min, 6mL / min, 7mL / min, 8mL / min, 10mL / min, 12mL / min, 15mL / min and other typical but non-limiting values, and the flow rate of the precipitant solution can be 100mL / min, 110mL / min, 120mL / min, 130mL / min, 140mL / min, 150mL / min and other typical but non-limiting values.

[0096] The flow rate of the precipitant solution can be automatically adjusted according to the pH value of the reaction system, and the flow rate of the complexing agent solution can be adjusted according to the ammonia concentration of the reaction system. For example, the flow rate of the precipitant solution can be adjusted so that the pH value of the reaction system is within the condition of 11.2-11.8 to achieve the third coprecipitation reaction.

[0097] In some embodiments, in step S50, the pH value of the second nucleation slurry is adjusted to a third preset pH value, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the second nucleation slurry to carry out a fourth co-precipitation reaction. When the precipitate reaches a second predetermined particle size, the addition of the metal mixed salt solution, the complexing agent solution, the precipitant solution and the first zinc salt solution is stopped to obtain a second growth slurry.

[0098] After the third coprecipitation reaction is carried out for a period of time, the third coprecipitation reaction is terminated, the pH value of the reaction system is adjusted to the third pH preset value, and the second zinc salt solution is switched to the first zinc salt solution, and the coprecipitation reaction is continued to realize the growth of the second crystal nucleus. In this reaction process, due to the change of pH environment, and the concentration of zinc ions increases, the zinc ions participating in the coprecipitation reaction are matched with the precipitation amount of nickel-iron-manganese ions per unit time, and a stable growth environment is provided for the second crystal nucleus, and the continuous increase of the second crystal nucleus particle size is realized. In addition, due to the wide particle size distribution of the second crystal nucleus, in the crystal nucleus growth process, the pores on the crystal nucleus surface can be filled / grown sediment particles, or the crystal nucleus with a smaller particle size is adsorbed or filled in the pores of the crystal nucleus with a larger particle size, or the crystal nucleus with a smaller particle size is filled in the gap formed by the agglomeration of multiple crystal nuclei, so that the tap density of the precursor particles is effectively improved.

[0099] In some embodiments, in step S50, the third preset pH value is 10.2-11.7. For example, the third preset pH value can be 10.2, 10.5, 10.7, 11, 11.2, 11.5, 11.7, etc., which are typical but non-limiting values.

[0100] After the third coprecipitation reaction is completed, the pH value of the reaction system is lowered to a third preset pH value, so that the second crystal nucleus enters a growth stage.

[0101] In some embodiments, in step S50, the third preset pH value is less than the second preset pH value, and the difference between the third preset pH value and the second preset pH value is 0.1-1, that is, relative to the second preset pH value, the pH drop of the reaction system is 0.1-1.

[0102] In the embodiment of the present application, the pH value of the fourth co-precipitation reaction is reduced within the above range, thereby reducing the precipitation rate of zinc ions and switching to a zinc salt solution with a higher concentration for the co-precipitation reaction, thereby matching the precipitation rate of zinc ions with the precipitation rates of other metal ions, thereby obtaining precursor particles in which each element is uniformly distributed.

[0103] In some embodiments, in step S50, the second predetermined particle size D50 is 4 μm-7 μm. For example, the second predetermined particle size D50 can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc., which are typical but non-limiting values.

[0104] In the embodiment of the present application, the reaction activity and tap density of the positive electrode material precursor particles are ensured by regulating the second predetermined particle size D50 within the above range.

[0105] In some embodiments, in step S50, in the fourth co-precipitation reaction, the flow rate of the metal mixed salt solution is greater than the flow rate of the first zinc salt solution.

[0106] The fourth coprecipitation reaction is carried out by switching to a higher concentration of the first zinc salt solution, so that the second crystal nucleus grows stably and orderly. During the reaction, the solubility of the zinc salt solution is increased and its addition rate is reduced, so that the precipitation rate of zinc ions matches the precipitation rate of nickel, iron and manganese, thereby obtaining precursor particles with uniform distribution of each element.

[0107] In some embodiments, in step S50, in the fourth coprecipitation reaction, the flow rate ratio of the metal mixed salt solution to the first zinc salt solution is 1:0.1-0.5. Exemplarily, the flow rate ratio of the metal mixed salt solution to the first zinc salt solution is 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, etc., which are typical but non-limiting values.

[0108] In some embodiments, in step S50, in the fourth coprecipitation reaction, the flow rate of the metal mixed salt solution is 150-200mL / min, the flow rate of the complexing agent solution is 5-15mL / min, and the flow rate of the precipitant solution is 100-150mL / min. Exemplarily, the flow rate of the mixed metal salt solution can be 150mL / min, 160mL / min, 170mL / min, 180mL / min, 190mL / min, 200mL / min and other typical but non-limiting values, the flow rate of the complexing agent solution can be 5mL / min, 6mL / min, 7mL / min, 8mL / min, 10mL / min, 12mL / min, 15mL / min and other typical but non-limiting values, and the flow rate of the precipitant solution can be 100mL / min, 110mL / min, 120mL / min, 130mL / min, 140mL / min, 150mL / min and other typical but non-limiting values.

[0109] In some embodiments, in step S50, the conditions of the fourth coprecipitation reaction include: a reaction temperature of 30°C-60°C, and a stirring speed of 150rpm-500rpm. Exemplarily, the reaction temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, and other typical but non-limiting values. The stirring speed can be 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, and other typical but non-limiting values.

[0110] By controlling the conditions of the fourth coprecipitation reaction such as temperature, rotation speed, and flow rate of each raw material liquid, a stable growth environment is provided, thereby obtaining precursor particles with regular morphology and high tap density.

[0111] In some embodiments, in step S60, the aging treatment time is 1 hour to 2 hours. For example, the aging treatment time can be 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, and other typical but non-limiting values.

[0112] Aging treatment can provide sufficient time for the precursor particles to adjust and improve their structure, thereby increasing the crystallinity and making the morphology more regular.

[0113] In some embodiments, in step S60, the washing treatment is carried out with a detergent solution. Specifically, the detergent includes at least one of sodium hydroxide, potassium hydroxide, and sodium carbonate. The concentration of the detergent solution is 20-200 g / L. Exemplarily, the concentration of the detergent solution can be 20 g / L, 50 g / L, 80 g / L, 100 g / L, 120 g / L, 150 g / L, 180 g / L, 200 g / L, etc., which are typical but non-limiting values.

[0114] The washing treatment conditions include: washing temperature of 25°C-80°C, and washing time of 2h-10h.

[0115] In some embodiments, in step S60, a drying process is further included after washing, and the drying process is performed at a temperature of 80°C-180°C.

[0116] The second aspect of the embodiment of the present application provides a positive electrode material precursor, which is a secondary particle formed by stacking needle-shaped primary particles, and has a chemical formula of Ni a Fe b Mn c Zn d (OH)2, where: 0.2≤a≤0.3, 0.3≤b≤0.4, 0.35≤c≤0.45, 0.02≤d≤0.15.

[0117] It is understandable that the cathode material precursor in the present application may be the first cathode material precursor, or the second cathode material precursor, or of course, may be a mixture of the first cathode material precursor and the second cathode material precursor.

[0118] The cathode material precursor provided in the second aspect of the embodiment of the present application is nickel-zinc-iron-manganese hydroxide, which has the characteristics of good sphericity and uniform distribution of zinc ions, which is beneficial to improving the electrochemical performance of the prepared cathode material.

[0119] In some embodiments, the positive electrode material precursor is prepared using the method for preparing the positive electrode material precursor in the first aspect.

[0120] In some embodiments, the tap density of the cathode material precursor is 1.5 g / m 3 -2g / m 3 For example, the tap density of the cathode material precursor may be 1.5 g / m 3 , 1.6g / m 3 , 1.7g / m 3 , 1.8g / m 3 , 1.9g / m 3 , 2g / m 3 etc. are typical but not limiting values.

[0121] Since the positive electrode material precursor is prepared by the preparation method provided in the first aspect of the present application, the tap density of the positive electrode material precursor is within the above range, which means that the content of the positive electrode material precursor per unit volume is relatively high, which is beneficial to improving the specific capacity of the positive electrode material.

[0122] In some embodiments, the tap density of the cathode material precursor is 1.7 g / m3 -2g / m 3 For example, the tap density of the cathode material precursor may be 1.7 g / m 3 , 1.8g / m 3 , 1.9g / m 3 , 2g / m 3 etc. are typical but not limiting values.

[0123] Controlling the tap density of the positive electrode material precursor within the above range means that a good stacking structure is formed between the positive electrode material precursor particles, which is conducive to a higher content of the positive electrode material precursor per unit volume, and the particles are in closer contact and support each other more strongly, and the active material is not easy to fall off, thereby improving the structural stability and deformation resistance of the material.

[0124] In some embodiments, the specific surface area of ​​the cathode material precursor is 10 m 2 / g-15m 2 / g. Exemplarily, the specific surface area of ​​the cathode material precursor may be 10m 2 / g, 11m 2 / g, 12m 2 / g, 13m 2 / g, 14m 2 / g, 15m 2 / g and other typical but non-limiting values.

[0125] In some embodiments, the particle size distribution of the cathode material precursor satisfies: For example, the particle size distribution It can be 0.6, 0.65, 0.7, 0.75, 0.8 or within a range consisting of any of the above point values.

[0126] In this embodiment, the particle size distribution of the positive electrode material precursor can be used to characterize the degree of dispersion of the particle size of all particles in the precursor particles from the volume distribution particle size D150, which can reflect the uniformity of the particle size distribution of the precursor particles. The precursor particles in the embodiment of the present application are selected by controlling the particle size distribution within the above range, so that the particle size distribution of the precursor particles is more dispersed, so that small-sized particles can be filled in the gaps generated when multiple precursor particles are piled up, or filled in the pores of larger particles, thereby effectively improving the tap density of the precursor particles.

[0127] In some embodiments, the D50 particle size of the cathode material precursor is 4 μm-7 μm. For example, the D50 particle size of the cathode material precursor can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, etc., which are typical but non-limiting values.

[0128] The embodiments of the present application provide a cathode material precursor whose macroscopic particles are in the micrometer scale, which is beneficial to shortening the diffusion distance of active ions in the cathode material precursor.

[0129] A third aspect of an embodiment of the present application provides a positive electrode material, which is prepared by mixing the positive electrode material precursor provided by the preparation method of the positive electrode material precursor provided by the first aspect and / or the positive electrode material precursor provided by the second aspect with sodium salt.

[0130] The third aspect of the embodiment of the present application provides a positive electrode precursor material obtained by sintering a sodium source and the above-mentioned positive electrode precursor material. The positive electrode precursor material is nickel-zinc-iron-manganese hydroxide, which has the characteristics of good sphericity and uniform distribution of zinc ions. Therefore, the positive electrode material obtained by sintering it with a sodium source has higher specific capacity, cycle stability, structural stability and other characteristics.

[0131] A fourth aspect of an embodiment of the present application provides a secondary battery, wherein the secondary battery includes the positive electrode material of the present application.

[0132] The secondary battery provided in the fourth aspect of the embodiment of the present application includes the above-mentioned positive electrode material, which has high gram capacity, cycle stability, structural stability and other characteristics, thereby improving the energy density, cycle stability and safety performance of the secondary battery.

[0133] The following describes the invention in conjunction with specific embodiments.

[0134] Example 1

[0135] This embodiment provides a positive electrode material precursor and a preparation method thereof.

[0136] A method for preparing a positive electrode material precursor comprises the following steps:

[0137] Step S1, prepare the following solution:

[0138] Metal mixed salt solution: obtained by dissolving nickel sulfate, ferrous sulfate and manganese sulfate in water; wherein the total molar concentration of the three elements of nickel, iron and manganese is 1.85 mol / L.

[0139] The zinc salt solution includes a first zinc salt solution and a second zinc salt solution:

[0140] The first zinc salt solution is obtained by dissolving zinc sulfate in water, and the molar concentration thereof is 0.5 mol / L.

[0141] The second zinc salt solution is obtained by dissolving zinc sulfate in water, and the molar concentration thereof is 0.05 mol / L.

[0142] The molar ratio of nickel ions, ferrous ions, manganese ions in the metal mixed salt solution to zinc ions in the zinc salt solution is 25:33:37:5.

[0143] Complexing agent solution: obtained by adding ammonia water into water, with a molar concentration of 4 mol / L.

[0144] Precipitant solution: obtained by dissolving sodium hydroxide in water, with a molar concentration of 5 mol / L.

[0145] S2. First coprecipitation reaction

[0146] In a nitrogen atmosphere, the metal mixed salt solution, complexing agent solution, precipitant solution and second zinc salt solution prepared in step S1 are fed at a uniform speed respectively by metering pumps, and are simultaneously added into a reaction vessel containing a base liquid (the volume of the base liquid is 1 / 3 of the effective volume of the reaction vessel, the base liquid contains sodium hydroxide and ammonia water, wherein the mass concentration of ammonium ions is 3 g / L, and the pH value of the base liquid is 11.9-12.1) to carry out a first coprecipitation reaction to obtain a first nucleation slurry; the conditions for controlling the first coprecipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the second zinc salt solution is 150 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the pH value is 11.17-11.23, the stirring speed is 350 rpm, the ammonium ion concentration is 2.7-3.3 g / L, and the reaction time is 8 h.

[0147] S3. Second coprecipitation reaction

[0148] The pH value of the first nucleation slurry obtained in the above step S2 is adjusted to 10.5-10.7, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first nucleation slurry at the same time to carry out a second coprecipitation reaction. The conditions for controlling the second coprecipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the first zinc salt solution is 70 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and when the particle size D50 of the precipitate reaches 3 μm, the addition of the first zinc salt solution is stopped to obtain the first growth slurry.

[0149] S4. The third coprecipitation reaction

[0150] The flow rate of the precipitant solution is adjusted to 170 ml / min, the pH value of the reaction slurry is adjusted to 11.2-11.3, the second zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are simultaneously added to the first growth slurry to carry out a third coprecipitation reaction to obtain a second nucleation slurry; the conditions for controlling the third coprecipitation reaction are: the flow rate of the metal mixed salt solution is 170 ml / min, the flow rate of the second zinc salt solution is 170 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and the reaction time is 10 hours.

[0151] S5. Fourth coprecipitation reaction

[0152] After the pH of the reaction system is reduced by 0.1, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are simultaneously added to the second nucleation slurry to carry out a fourth coprecipitation reaction. The conditions for controlling the fourth coprecipitation reaction are as follows: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the first zinc salt solution is 70 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and when the particle size D50 of the precipitate reaches 5 μm, the addition of the metal mixed salt solution, the complexing agent solution, the precipitant solution and the first zinc salt solution is stopped to obtain a second growth slurry.

[0153] S6. The second growth slurry is aged for 2 hours, filtered, washed with a sodium hydroxide solution having a concentration of 50 g / L, and dried at 120° C. to obtain a positive electrode material precursor.

[0154] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0155] Example 2

[0156] This embodiment provides a positive electrode material precursor and a preparation method thereof.

[0157] A method for preparing a positive electrode material precursor, which differs from Example 1 in that the reaction time in step S4 is 8 hours.

[0158] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05(OH)2 is prepared by the above-mentioned preparation method.

[0159] Example 3

[0160] This embodiment provides a positive electrode material precursor and a preparation method thereof.

[0161] A method for preparing a positive electrode material precursor, which differs from Example 1 in that the conditions for the co-precipitation reaction in step S2 and step S4 are different.

[0162] Step S2 is specifically as follows:

[0163] In a nitrogen atmosphere, the metal mixed salt solution, complexing agent solution, precipitant solution and second zinc salt solution prepared in step S1 are fed at a uniform speed respectively by metering pumps, and are simultaneously added into a reaction vessel containing a base liquid (the volume of the base liquid is 1 / 3 of the effective volume of the reaction vessel, the base liquid contains sodium hydroxide and ammonia water, wherein the mass concentration of ammonium ions is 3 g / L, and the pH value of the base liquid is 11.9-12.1) to carry out a first coprecipitation reaction to obtain a first nucleation slurry; the conditions for controlling the first coprecipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the second zinc salt solution is 150 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the pH value is 10.8-10.9, the stirring speed is 350 rpm, the ammonium ion concentration is 2.7-3.3 g / L, and the reaction time is 4 h.

[0164] Step S4 is specifically as follows:

[0165] The flow rate of the precipitant solution is adjusted to 170 ml / min, the pH value of the reaction slurry is adjusted to 11.2-11.3, and the second zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are simultaneously added to the first growth slurry to carry out a third coprecipitation reaction to obtain a second nucleation slurry; the conditions for controlling the third coprecipitation reaction are: the flow rate of the metal mixed salt solution is 170 ml / min, the flow rate of the second zinc salt solution is 170 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and the reaction time is 8 hours.

[0166] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0167] Example 4

[0168] This embodiment provides a positive electrode material precursor and a preparation method thereof.

[0169] A method for preparing a positive electrode material precursor, which differs from Example 1 in that the conditions for the co-precipitation reaction in step S2 and step S3 are different.

[0170] Step S2 is specifically as follows:

[0171] In a nitrogen atmosphere, the metal mixed salt solution, complexing agent solution, precipitant solution and second zinc salt solution prepared in step S1 are fed at a uniform speed respectively by metering pumps, and are simultaneously added into a reaction vessel containing a base liquid (the volume of the base liquid is 1 / 3 of the effective volume of the reaction vessel, the base liquid contains sodium hydroxide and ammonia water, wherein the mass concentration of ammonium ions is 3 g / L, and the pH value of the base liquid is 11.9-12.1) to carry out a first coprecipitation reaction to obtain a first nucleation slurry; the conditions for controlling the first coprecipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the second zinc salt solution is 150 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the pH value is 10.8-10.9, the stirring speed is 350 rpm, the ammonium ion concentration is 2.7-3.3 g / L, and the reaction time is 8 h.

[0172] S3. Second coprecipitation reaction

[0173] The pH value of the first nucleation slurry obtained in the above step S2 is adjusted to 10.2-10.3, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first nucleation slurry at the same time to carry out a second coprecipitation reaction. The conditions for controlling the second coprecipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the first zinc salt solution is 70 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and when the particle size D50 of the precipitate reaches 3.5 μm, the addition of the first zinc salt solution is stopped to obtain the first growth slurry.

[0174] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0175] Example 5

[0176] This embodiment provides a positive electrode material precursor and a preparation method thereof.

[0177] A method for preparing a positive electrode material precursor, which differs from Example 1 in that the conditions for the co-precipitation reaction in step S4 and step S5 are different.

[0178] Step S4 is specifically as follows:

[0179] The flow rate of the precipitant solution is adjusted to 180 ml / min, the pH value of the reaction slurry is adjusted to 11.6-11.7, and the second zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are simultaneously added to the first growth slurry to carry out a third coprecipitation reaction to obtain a second nucleation slurry; the conditions for controlling the third coprecipitation reaction are: the flow rate of the metal mixed salt solution is 170 ml / min, the flow rate of the second zinc salt solution is 170 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and the reaction time is 8 hours.

[0180] S5. Fourth coprecipitation reaction

[0181] After the pH of the reaction system is reduced by 1, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are simultaneously added to the second nucleation slurry to carry out a fourth coprecipitation reaction. The conditions for controlling the fourth coprecipitation reaction are as follows: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the first zinc salt solution is 70 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and when the particle size D50 of the precipitate reaches 6.5 μm, the addition of the metal mixed salt solution, the complexing agent solution, the precipitant solution and the first zinc salt solution is stopped to obtain a second growth slurry.

[0182] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0183] Example 6

[0184] This embodiment provides a positive electrode material precursor and a preparation method thereof.

[0185] A method for preparing a positive electrode material precursor, which differs from Example 1 in that:

[0186] When the particle size D50 of the precipitate reaches 5 μm in step S3, the feeding is stopped;

[0187] Delete steps S4 and S5;

[0188] The slurry obtained in step S3 is subjected to an aging treatment to obtain a positive electrode material precursor.

[0189] Specifically, steps S3 and S6 are:

[0190] Step S3, adjusting the pH value of the first nucleation slurry obtained in the above step S2 to 10.5-10.7, stopping the addition of the second zinc salt solution, and adding the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution to the first nucleation slurry at the same time to carry out a second coprecipitation reaction, wherein the conditions for controlling the second coprecipitation reaction are as follows: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the first zinc salt solution is 70 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50° C., the stirring speed is 350 rpm, and when the particle size D50 of the precipitate reaches 5 μm, stopping the addition of the metal mixed salt solution, the complexing agent solution, the precipitant solution and the first zinc salt solution to obtain a growth slurry;

[0191] Step S6, aging the growth slurry obtained in the above step S3 for 2 hours, filtering, washing with a sodium hydroxide solution with a concentration of 50 g / L, and drying at 120° C. to obtain a positive electrode material precursor.

[0192] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0193] Comparative Example 1

[0194] This comparative example provides a positive electrode material precursor and a preparation method thereof.

[0195] A method for preparing a positive electrode material precursor, which differs from Example 1 in that: a second zinc salt solution is used for the first coprecipitation reaction, a second coprecipitation reaction, and a third coprecipitation reaction, that is, a second zinc salt solution is used for the second coprecipitation reaction in step S3, and a second zinc salt solution is used for the fourth coprecipitation reaction in step S5.

[0196] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0197] Comparative Example 2

[0198] This comparative example provides a positive electrode material precursor and a preparation method thereof.

[0199] A method for preparing a positive electrode material precursor, which differs from Example 1 in that: a first zinc salt solution is used for the first coprecipitation reaction, a second coprecipitation reaction, a third coprecipitation reaction, and a third coprecipitation reaction, that is, the first zinc salt solution is used for the first coprecipitation reaction in step S2, and the first zinc salt solution is used for the third coprecipitation reaction in step S4.

[0200] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0201] Comparative Example 3

[0202] This comparative example provides a positive electrode material precursor and a preparation method thereof.

[0203] A method for preparing a positive electrode material precursor comprises the following steps:

[0204] Step S1, prepare the following solution:

[0205] Metal mixed salt solution: obtained by dissolving nickel sulfate, ferrous sulfate, manganese sulfate and zinc sulfate in water; wherein the molar ratio of nickel, iron, manganese and zinc is 25:33:37:5, and the total molar concentration of the four elements is 2.5 mol / L.

[0206] Complexing agent solution: obtained by adding ammonia water into water, with a molar concentration of 4 mol / L.

[0207] Precipitant solution: obtained by dissolving sodium hydroxide in water, with a molar concentration of 5 mol / L.

[0208] S2. First coprecipitation reaction

[0209] In a nitrogen atmosphere, the metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed respectively through metering pumps, and are simultaneously added into a reaction vessel containing a base liquid (the volume of the base liquid is 1 / 3 of the effective volume of the reaction vessel, the base liquid contains sodium hydroxide and ammonia water, wherein the mass concentration of ammonium ions is 3 g / L, and the pH of the base liquid is 11.9-12.1) to carry out a first coprecipitation reaction to obtain a first nucleation slurry; the conditions for controlling the first coprecipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the pH is 11.17-11.23, the stirring speed is 350 rpm, the ammonium ion concentration is 2.7-3.3 g / L, and the reaction time is 8 h.

[0210] S3. Second coprecipitation reaction

[0211] The pH value of the first nucleation slurry obtained in the above step S2 is adjusted to 10.5-10.7, and the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first nucleation slurry at the same time to carry out a second co-precipitation reaction. The conditions for controlling the second co-precipitation reaction are: the flow rate of the metal mixed salt solution is 150 ml / min, the flow rate of the first zinc salt solution is 70 ml / min, the flow rate of the precipitant solution is 150 ml / min, the flow rate of the complexing agent solution is 10 ml / min, the temperature is 50°C, the stirring speed is 350 rpm, and when the particle size D50 of the precipitate reaches 5 μm, stop adding the metal mixed salt solution, the complexing agent solution and the precipitant solution to obtain a growth slurry.

[0212] Step S4, aging the growth slurry obtained in the above step S3 for 2 hours, filtering, washing with a sodium hydroxide solution with a concentration of 50 g / L, and drying at 120° C. to obtain a positive electrode material precursor.

[0213] A positive electrode material precursor, whose molecular formula is Ni 0.25 Fe 0.33 Mn 0.37 Zn 0.05 (OH)2 is prepared by the above-mentioned preparation method.

[0214] Performance Testing

[0215] (1) SEM analysis

[0216] The cathode material precursors prepared in Example 1 were subjected to scanning electron microscope analysis (SEM analysis), and the results are as follows: Figure 1 The cathode material precursors prepared in Example 2 were subjected to scanning electron microscopy analysis (SEM analysis), and the results were as follows: Figure 2The cathode material precursors prepared in Example 6 were subjected to scanning electron microscopy analysis (SEM analysis), and the results were as follows Figure 3 shown.

[0217] from Figure 1 It can be seen that the cathode material precursor prepared in Example 1 is secondary spherical particles formed by assembling needle-shaped primary particles, with regular morphology, wide particle size distribution and dense particles.

[0218] from Figure 2 It can be seen that the cathode material precursor prepared in Example 2 is secondary spherical particles formed by assembling needle-shaped primary particles, with regular morphology, wide particle size distribution and dense particles.

[0219] from Figure 3 It can be seen that the positive electrode material precursor prepared in Example 6 has a regular morphology.

[0220] (2) Physical property characterization

[0221] The performance of the positive electrode material precursors prepared in Examples 1-6 and Comparative Examples 1-3 was analyzed, and the results are shown in Table 1 below.

[0222] Table 1

[0223]

[0224] The particle size distribution in Table 1 refers to

[0225] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a positive electrode material precursor, characterized in that: The following steps are involved: Prepare a metal mixed salt solution, a zinc salt solution, a complexing agent solution and a precipitant solution, wherein the metal mixed salt solution contains nickel, iron and manganese, and the zinc salt solution includes a first zinc salt solution and a second zinc salt solution, wherein the concentration of the first zinc salt solution is greater than that of the second zinc salt solution; Adding the metal mixed salt solution, the second zinc salt solution, the complexing agent solution and the precipitant solution into the bottom liquid to carry out a first coprecipitation reaction to obtain a first nucleation slurry; The pH value of the first nucleation slurry is adjusted to a first preset pH value, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first nucleation slurry to perform a second coprecipitation reaction to obtain a first growth slurry; The first growth slurry is separated into solid and liquid to obtain a first positive electrode material precursor.

2. The method for preparing a cathode material precursor according to claim 1, characterized in that: Before the solid-liquid separation of the first growth slurry, the following steps are also included: When the precipitate in the first growth slurry reaches a first predetermined particle size, the pH value of the first growth slurry is adjusted to a second preset pH value, the addition of the first zinc salt solution is stopped, and the second zinc salt solution, the metal mixed salt solution, the complexing agent solution and the precipitant solution are added to the first growth slurry to perform a third coprecipitation reaction to obtain a second nucleation slurry; The pH value of the second nucleation slurry is adjusted to a third preset pH value, the addition of the second zinc salt solution is stopped, and the first zinc salt solution, the metal mixed salt solution, the complexing agent solution, and the precipitant solution are added to the second nucleation slurry to perform a fourth coprecipitation reaction, and when the precipitate reaches a second predetermined particle size, the addition of the metal mixed salt solution, the complexing agent solution, the precipitant solution, and the first zinc salt solution is stopped to obtain a second growth slurry; The second growth slurry is separated into solid and liquid to obtain a second positive electrode material precursor.

3. The method for preparing a positive electrode material precursor according to claim 2, characterized in that: The first preset pH value is 10-11.5; and / or The second preset pH value is 11.2-11.8; and / or The third preset pH value is 10.2-11.7; and / or The D50 of the first predetermined particle size is 2 μm-4 μm; and / or The D50 of the second predetermined particle size is 4 μm-7 μm.

4. The method for preparing a cathode material precursor according to claim 2, characterized in that: In the first coprecipitation reaction, the flow rate of the metal mixed salt solution is the same as the flow rate of the second zinc salt solution; and / or In the second coprecipitation reaction, the flow rate of the metal mixed salt solution is greater than the flow rate of the first zinc salt solution; and / or In the third coprecipitation reaction, the flow rate of the metal mixed salt solution is the same as the flow rate of the second zinc salt solution; and / or In the fourth coprecipitation reaction, the flow rate of the metal mixed salt solution is greater than the flow rate of the first zinc salt solution.

5. The method for preparing a cathode material precursor according to claim 4, characterized in that: In the first coprecipitation reaction, the second coprecipitation reaction, the third coprecipitation reaction and the fourth coprecipitation reaction, the flow rate of the metal mixed salt solution is 150-200 mL / min, the flow rate of the complexing agent solution is 5-15 mL / min, and the flow rate of the precipitant solution is 100-150 mL / min; and / or In the second coprecipitation reaction and the fourth coprecipitation reaction, the flow rate ratio of the metal mixed salt solution to the first zinc salt solution is 1:0.1-0.

5.

6. The method for preparing a cathode material precursor according to claim 1, characterized in that: The total concentration of nickel, iron and manganese in the metal mixed salt solution is 1 mol / L-2.5 mol / L; and / or The concentration of zinc ions in the first zinc salt solution is 0.35 mol / L-0.65 mol / L, and the molar concentration ratio of zinc ions in the first zinc salt solution to the molar concentration of zinc ions in the second zinc salt solution is 1:0.1-0.5; and / or The molar ratio of nickel ions, ferrous ions, and manganese ions in the metal mixed salt solution to zinc ions in the zinc salt solution is 20-30:30-40:35-45:2-15.

7. The method for preparing a cathode material precursor according to claim 2, characterized in that: The conditions of the first coprecipitation reaction include: reaction temperature of 30°C-60°C, stirring speed of 150rpm-500rpm, reaction time of 4h-10h, pH value of 11-12.5; and / or The conditions of the second coprecipitation reaction include: reaction temperature of 30°C-60°C, stirring speed of 150rpm-500rpm; and / or The conditions of the third coprecipitation reaction include: reaction temperature of 30°C-60°C, stirring speed of 150rpm-500rpm, reaction time of 2h-15h; and / or The conditions of the fourth coprecipitation reaction include: reaction temperature of 30° C.-60° C., and stirring speed of 150 rpm-500 rpm.

8. The method for preparing a cathode material precursor according to any one of claims 1 to 7, characterized in that: The concentration of ammonium ions in the base solution is 1-3 g / L, and the pH value is 11-12.5; and / or The precipitant contained in the precipitant solution includes at least one of sodium hydroxide, potassium hydroxide and sodium carbonate; and / or The complexing agent contained in the complexing agent solution includes at least one of ammonia water, citric acid and sodium oxalate.

9. A positive electrode material precursor, characterized in that: The positive electrode material precursor is a secondary particle formed by stacking needle-shaped primary particles. The chemical formula of the positive electrode material precursor is Ni a Fe b Mn c Zn d (OH)2, where: 0.2≤a≤0.3, 0.3≤b≤0.4, 0.35≤c≤0.45, 0.02≤d≤0.

15.

10. The cathode material precursor according to claim 9, characterized in that: The positive electrode material precursor is prepared by the method for preparing the positive electrode material precursor according to any one of claims 1 to 8.

11. The cathode material precursor according to claim 9 or 10, characterized in that: The positive electrode material precursor satisfies at least one of the following (1)-(4): (1) Tap density is 1.5g / m 3 -2g / m 3 ; (2) Specific surface area is 10m 2 / g-15m 2 / g; (3) Particle size distribution meets the following requirements: (4) D50 particle size is 4μm-7μm.

12. A positive electrode material, characterized in that: The positive electrode material is prepared by mixing the positive electrode material precursor obtained by the preparation method of the positive electrode material precursor according to any one of claims 1 to 8 and / or the positive electrode material precursor according to any one of claims 9 to 11 with a sodium salt.

13. A secondary battery, characterized in that: The secondary battery comprises the positive electrode material according to claim 12.

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