Positive electrode precursor material and preparation method therefor, and positive electrode material and use thereof

Abstract

Provided in the present application are a positive electrode precursor material and a preparation method therefor, and a positive electrode material and the use thereof. The preparation method comprises the following steps: adding a first main metal element salt solution, a first precipitant solution and a first complexing agent solution into a base solution in a co-current manner, so as to perform a first co-precipitation reaction, and adding a crystal growth inducer during the first co-precipitation reaction to obtain crystal nuclei; and after the first co-precipitation reaction is completed, adding a second main metal element salt solution, a second precipitant solution and a second complexing agent solution in a co-current manner to perform a second co-precipitation reaction, so as to obtain the positive electrode precursor material. By means of the preparation method provided by the present application, by means of the stepwise growth of precursor particles and the control of the addition timing of a crystal growth inducer, internuclear agglomeration of a precursor material is prevented, the sphericity of the precursor is ensured, and a positive electrode precursor material having a loose and porous inner core, a radial arrangement, and a relatively dense outer portion is obtained, thereby improving the safety performance, cycling performance and rate performance of the positive electrode material.

Description

A positive electrode precursor material, a preparation method thereof, a positive electrode material and application thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and relates to a positive electrode precursor material, a preparation method thereof, a positive electrode material and application thereof. BACKGROUND

[0002] With the decrease of non-renewable fossil energy and environmental problems, the development and utilization of new clean energy have attracted more and more attention. In the rapidly developing new energy vehicle industry, power lithium batteries are a key component. Lithium ion batteries mainly include positive and negative electrode materials, separators, electrolytes and current collectors, etc., wherein the performance of the positive electrode material will directly affect the charge and discharge capacity, cycle performance, rate performance and high temperature thermal stability of the battery.

[0003] With the increasing demand for energy density of power lithium batteries, high-nickel ternary materials with high specific capacity, low cost, good safety and other characteristics are considered to be the most widely used power battery positive electrode materials at present. High-nickel materials have always been the focus of new energy industry to solve the range anxiety, but due to the problems in the industrialization of high-nickel materials, including the serious nickel-lithium mixing phenomenon with the increase of Ni content, hindering the diffusion of Li + , reducing the specific capacity and rate performance, but the phase change of high-nickel materials occurs during the charge and discharge process, the thermal stability and cycle performance decrease, thereby affecting the service life and safety of power lithium batteries for new energy vehicles. These technical barriers restrict the large-scale popularization of high-nickel materials.

[0004] To solve these technical problems, the safety and stability of the material are improved through bulk phase doping, outer layer coating and core-shell design, etc.

[0005] CN106910874A discloses a method for realizing surface coating and surface layer doping of high-nickel material at the same time, which mixes the precursor with tetrabutyl titanate, and then forms a titanium dioxide coating layer on the surface of the precursor through the hydrolysis reaction of tetrabutyl titanate, to form a high-nickel positive electrode material with surface Li2TiO3 coating and surface layer doping Ti in the subsequent lithium mixing-high temperature sintering process. The synergistic effect of the two can effectively inhibit the interface reaction of the material, improve the structural stability and improve the electrochemical performance of the material. Although the synergistic effect of surface doping and coating can effectively improve the interface stability of the material, it often affects the conduction of electrons at the interface.

[0006] CN110429275A discloses a method for realizing carbon coating on the surface of ternary positive electrode material in a low-temperature thermal reduction atmosphere by using an organic carbon source in an organic liquid phase system, which improves the electronic conductivity of the material and enhances its cycle stability and rate performance. However, the increase of coating substances leads to a decrease in the discharge specific capacity under a small current, because the secondary sintering process in an argon atmosphere creates a micro-reduction environment, the carbon captures oxygen in the positive electrode material lattice, leading to an increase in oxygen vacancies and lithium-nickel mixing degree, and a phase transition from layered to spinel to inert rock salt on the particle surface, affecting the deintercalation of lithium ions.

[0007] CN114408988A synthesizes a ternary positive electrode precursor by multi-step co-precipitation, which is divided into a rapid nucleation stage, a uniform growth stage and a slow growth stage. The reaction pH, ammonia concentration and reaction speed are continuously adjusted in the three stages, and the flow of oxidizing gas is also controlled to prepare a loose and porous precursor with a large specific surface area. The process control is relatively complex, and the system is prone to fluctuation, especially when the oxidizing gas is introduced to control the oxidation of the material, it is difficult to control the oxidation degree, which may also cause low production consistency.

[0008] The above-mentioned bulk doping, outer coating and core-shell design schemes have certain limitations for improving high-nickel materials.

[0009] Therefore, how to improve the safety performance, cycle performance and rate performance of the positive electrode material, especially the high-nickel positive electrode material, is a technical problem to be solved. SUMMARY

[0010] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of protection of the claims.

[0011] The present application provides a positive electrode precursor material and a preparation method thereof, a positive electrode material and an application. The preparation method provided by the present application controls the addition time of the crystal growth inducer by step-by-step growth of the precursor particles, prevents the agglomeration of the crystal nuclei of the precursor material, ensures the sphericity of the precursor, and obtains a positive electrode precursor material with a loose and porous inner core, radial arrangement and relatively dense outer part, thereby improving the safety performance, cycle performance and rate performance of the positive electrode material.

[0012] In a first aspect, the present application provides a preparation method of a positive electrode precursor material, which comprises the following steps:

[0013] The first main metal element salt solution, the first precipitant solution and the first complexing agent solution are added into the bottom liquid in parallel, and a first co-precipitation reaction is carried out. During the first co-precipitation reaction, a crystal growth inducer is added to obtain a crystal nucleus;

[0014] After the first co-precipitation reaction is completed, the second main metal element salt solution, the second precipitant solution and the second complexing agent solution are added in parallel, and the second co-precipitation reaction is continued to obtain the positive electrode precursor material.

[0015] It should be noted that the types and concentrations of substances in the first main metal element salt solution and the second main metal element salt solution, the first precipitant solution and the second precipitant solution, and the first complexing agent solution and the second complexing agent solution provided in the present application can be the same or different; if different, after the first co-precipitation reaction is completed, the addition of raw materials in the stage of the first co-precipitation reaction is stopped, and the raw materials in the stage of the second co-precipitation reaction are added; if the same, the feeding flow rate and reaction conditions of each raw material in the stage of the second co-precipitation reaction can be controlled; the skilled person in the art can select and control according to the actual needs.

[0016] The preparation method provided in the present application prevents agglomeration between crystal nuclei by stepwise growth of precursor particles and control of the timing of addition of the crystal growth inducer, and ensures the sphericity of the precursor; the crystal growth inducer is added during the first co-precipitation reaction, which allows directional growth of the crystal at the initial stage of crystal nucleation and growth, forms a structure in which the inner core primary particles are arranged radially and stacked loosely and porous, and have a divergent morphology; during the second co-precipitation reaction, no crystal growth inducer is added, and the primary particles grown in this stage are relatively thicker than the crystal nucleus primary particles in the first co-precipitation reaction, and the obtained outer particles are relatively dense, thereby reducing the reaction of the positive electrode with the electrolyte during the cycle process, reducing gas production, and improving the safety and cycle performance of the material; and the inner core is loosely porous and arranged radially, which allows Li + Fast deintercalation, which increases the rate performance of the material.

[0017] In the present application, if no crystal growth inducer is added and only stage preparation is performed, it is difficult to achieve controllable growth of the crystal inside the particle, and thus it is impossible to obtain a precursor morphology structure in which the inner core is arranged radially; and if the addition sequence of the crystal growth inducer is adjusted, i.e., the crystal growth inducer is added in the second co-precipitation reaction stage, the crystal seeds will agglomerate more severely at the initial stage of nucleation, the sphericity will be poor, and thus the various indicators of the final product will be affected.

[0018] The following is an optional technical solution of the present application, but is not a limitation on the technical solutions provided in the present application. Through the following optional technical solution, the technical purposes and beneficial effects of the present application can be better achieved and realized.

[0019] In one embodiment, the first main metal element includes nickel, and further includes any one or a combination of at least two of cobalt, manganese or aluminum.

[0020] In one embodiment, the molar percentage of nickel in the first main metal element is 30-99%, for example 30%, 40%, 50%, 60%, 70%, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98%, or 99%, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0021] The preparation method provided in the application can solve the problem of various nickel contents, especially high-nickel materials (molar percentage of nickel ≥80%); effectively suppresses the lithium-nickel mixing phenomenon, and also solves the phase change problem of high-nickel materials in the charging and discharging process; thereby improving the discharge capacity, rate performance, safety performance, and cycle performance of high-nickel positive electrode materials.

[0022] In one embodiment, the concentration of the first main metal element salt solution is 1-4 mol / L, for example 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0023] In one embodiment, the concentration of the first precipitant solution is 1-3 mol / L, for example 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0024] In one embodiment, the concentration of the first complexing agent solution is 1-3 mol / L, for example 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0025] In one embodiment, the feeding flow rate of the first main metal element salt solution is 15-30 kg / h, for example 15 kg / h, 18 kg / h, 20 kg / h, 24 kg / h, 25 kg / h, 28 kg / h, or 30 kg / h, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0026] In one embodiment, the feeding flow rate of the first precipitant solution is 5-10 kg / h, for example 5 kg / h, 6 kg / h, 7 kg / h, 8 kg / h, 9 kg / h, or 10 kg / h, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0027] In one embodiment, the first complexing agent solution is fed at a flow rate of 2 to 5 kg / h, such as 2 kg / h, 3 kg / h, 4 kg / h, or 5 kg / h, and the like, but not limited to the listed values, and other values within the range are also applicable.

[0028] In one embodiment, the base solution includes a solvent and a crystal growth inducer.

[0029] The application adds a crystal growth inducer to the base solution, which is more conducive to the oriented growth of precursor particles from the beginning of the reaction, ensures the sphericity of the particles, and also realizes the radial arrangement of primary particles inside the particles, showing a loose and porous structure inside.

[0030] In one embodiment, the concentration of the crystal growth inducer in the base solution is 0.5 to 1 g / L, such as 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, or 1 g / L, and the like, but not limited to the listed values, and other values within the range are also applicable.

[0031] In the application, the concentration of the crystal growth inducer in the base solution is adjusted to 0.5 to 1 g / L, which can better control the directional growth of crystals and form a loose and porous structure inside the particles.

[0032] In one embodiment, the crystal growth inducer includes triethylamine.

[0033] In one embodiment, the crystal growth inducer is intermittently added during the first co-precipitation reaction.

[0034] In the application, the crystal growth inducer is intermittently added during the first co-precipitation reaction, which can improve the utilization rate of the crystal growth inducer, avoid safety hazards caused by high triethylamine concentration in the reaction kettle, and also avoid the possibility of reducing the concentration of the crystal growth inducer as the reaction time increases.

[0035] In one embodiment, the crystal growth inducer is added every 4 hours during the first co-precipitation reaction.

[0036] In one embodiment, the crystal growth inducer is added every 4 hours during the first co-precipitation reaction.

[0037] The application improves the ability of the crystal growth inducer to react and complex with the precipitator at the initial stage of the reaction by the synergistic cooperation of the interval time and the amount of the crystal growth inducer added in the first coprecipitation reaction, so that the crystal presents directional growth, ensures the concentration of the crystal growth inducer in the system, and also makes the operation more simple.

[0038] In one embodiment, the reaction temperature of the first coprecipitation reaction is 40-70℃, such as 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or 70℃, etc., but not only limited to the listed values, and other values not listed in this range are also applicable.

[0039] In one embodiment, the pH value of the first coprecipitation reaction is 10-12, such as 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8 or 12, etc., but not only limited to the listed values, and other values not listed in this range are also applicable.

[0040] In one embodiment, the stirring speed of the first coprecipitation reaction is 200-380 r / min, such as 200 r / min, 230 r / min, 250 r / min, 280 r / min, 300 r / min, 330 r / min, 350 r / min or 380 r / min, etc., but not only limited to the listed values, and other values not listed in this range are also applicable.

[0041] In one embodiment, the average particle size of the crystal nucleus is 3-8 μm, such as 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm, etc., but not only limited to the listed values, and other values not listed in this range are also applicable.

[0042] The average particle size of the crystal nucleus provided by the application is controlled to 3-8 μm, which on the one hand improves the sphericity of the obtained precursor material, and on the other hand also ensures the structural stability of the complete particles of the precursor material, so as not to affect the sphericity of the final precursor due to too large particle size, and affect the growth speed of the second stage precursor due to too small particle size.

[0043] In one embodiment, the second main metal element includes nickel, and also includes any one or a combination of at least two of cobalt, manganese or aluminum.

[0044] In one embodiment, the molar percentage of the nickel in the second main metal element is 30-99%, such as 30%, 40%, 50%, 60%, 70%, 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98%, or 99%, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0045] In one embodiment, the co-precipitation process further comprises adding a doping salt solution.

[0046] The application in the second co-precipitation process, the doping of the doping element, further improves the electrochemical performance of the positive electrode material; and the type and amount of doping elements are selected by conventional technology, and the person skilled in the art can select and adjust according to the actual demand, and the doping elements include but are not limited to zirconium, magnesium, ammonium or molybdenum, etc.

[0047] In one embodiment, the concentration of the second main metal element salt solution is 1-4 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, or 4 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0048] In one embodiment, the concentration of the second precipitant solution is 1-3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0049] In one embodiment, the concentration of the second complexing agent solution is 1-3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0050] In one embodiment, the concentration of the doping salt solution is 1-4 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, or 4 mol / L, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0051] In one embodiment, the feed flow rate of the first main metal element salt solution is 30-50 kg / h, for example 30 kg / h, 33 kg / h, 35 kg / h, 38 kg / h, 40 kg / h, 43 kg / h, 45 kg / h, 48 kg / h, or 50 kg / h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0052] In one embodiment, the feed flow rate of the first precipitant solution is 10-20 kg / h, for example 10 kg / h, 11 kg / h, 12 kg / h, 13 kg / h, 14 kg / h, 15 kg / h, 16 kg / h, 17 kg / h, 18 kg / h, 19 kg / h, or 20 kg / h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0053] In one embodiment, the feed flow rate of the first complexing agent solution is 5-10 kg / h, for example 5 kg / h, 6 kg / h, 7 kg / h, 8 kg / h, 9 kg / h, or 10 kg / h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0054] In one embodiment, the feed flow rate of the doping salt solution is 1-10 kg / h, for example 1 kg / h, 2 kg / h, 3 kg / h, 4 kg / h, 5 kg / h, 6 kg / h, 7 kg / h, 8 kg / h, 9 kg / h, or 10 kg / h, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0055] In one embodiment, the reaction temperature of the second co-precipitation reaction is 40-70 °C, for example 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, or 70 °C, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0056] In one embodiment, the pH value of the second co-precipitation reaction is 9-11, for example 9, 9.3, 9.5, 9.8, 10, 10.3, 10.5, 10.8, or 11, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0057] In one embodiment, the stirring speed of the second co-precipitation reaction is 150-300 r / min, for example 150 r / min, 180 r / min, 200 r / min, 230 r / min, 250 r / min, 280 r / min, or 300 r / min, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0058] In one embodiment, the average particle size of the positive electrode precursor material is 5-18 μm, for example 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm or 18 μm, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0059] The preparation method provided in the application, under the action of the crystal growth inducer, by adjusting the concentration, feed flow and reaction conditions of the raw materials in different reaction stages, ensures the sphericity of the positive electrode precursor material particles and the stability of the structure, so that a positive electrode material with stable structure and excellent performance can be obtained subsequently.

[0060] As an optional technical solution, the preparation method comprises the following steps:

[0061] The first main metal element salt solution with a feed flow of 15-30 kg / h and a concentration of 1-4 mol / L, the first precipitant solution with a feed flow of 5-10 kg / h and a concentration of 1-3 mol / L, and the first complexing agent solution with a feed flow of 2-5 kg / h and a concentration of 1-3 mol / L are added into the bottom liquid in parallel, the bottom liquid comprises the crystal growth inducer with a concentration of 0.5-1 g / L, the first co-precipitation reaction is carried out at 40-70 °C at 200-380 r / min in an environment with a pH value of 10-12, during the first co-precipitation reaction, the crystal growth inducer is added every 4 h, and the addition amount of each time is 0.1-0.5 kg, and a crystal nucleus with an average particle size of 3-8 μm is obtained;

[0062] After the first co-precipitation reaction, the second main metal element salt solution with a feed flow of 30-50 kg / h and a concentration of 1-4 mol / L, the second precipitant solution with a feed flow of 10-20 kg / h and a concentration of 1-3 mol / L, the second complexing agent solution with a feed flow of 5-10 kg / h and a concentration of 1-3 mol / L, and the dopant solution with a feed flow of 1-10 kg / h and a concentration of 1-4 mol / L are added in parallel, the second co-precipitation reaction is continued at 40-70 °C at 150-300 r / min in an environment with a pH value of 9-11, and the positive electrode precursor material with an average particle size of 5-18 μm is obtained.

[0063] It should be further pointed out that:

[0064] The types of the first precipitant and the second precipitant in the application are conventional technical choices, including but not limited to liquid alkali, such as sodium hydroxide or potassium hydroxide, etc.

[0065] The types of the first complexing agent and the second complexing agent in the present application are conventional technical choices, including but not limited to ammonia and the like;

[0066] The types of the salts in the first main metal salt and the second main metal salt in the present application are also conventional technical choices, including but not limited to sulfate, chloride or nitrate and the like;

[0067] The precipitating agent and the complexing agent in the present application can also be included in the bottom liquid, and the types and amounts of the precipitating agent and the complexing agent can be adaptively selected and adjusted.

[0068] In a second aspect, the present application provides a positive electrode precursor material, which is prepared by the preparation method according to the first aspect; the positive electrode precursor material comprises an inner core and an outer shell; the inner core is a porous structure; and the compactness of the outer shell is higher than that of the inner core.

[0069] The inner core in the present application is the crystal nucleus in the precursor material.

[0070] In a third aspect, the present application provides a positive electrode material, which is prepared by mixing and sintering the positive electrode precursor material according to the second aspect with a lithium source.

[0071] In the present application, the method for preparing the positive electrode material from the positive electrode precursor material is a conventional technical means. For example, the present application provides a preparation process of a positive electrode material:

[0072] The positive electrode precursor material according to the second aspect is mixed with a lithium source at a molar ratio of Me:Li of 1:(1-1.5) and uniformly, and is high-temperature sintered at a sintering temperature of 500-1000 under an oxygen-containing atmosphere for 6-20 hours, and is naturally cooled to room temperature, so that the positive electrode material is obtained;

[0073] Optionally, the lithium source includes but is not limited to at least one of lithium hydroxide, lithium carbonate or lithium acetate; and the oxygen-containing atmosphere includes an air atmosphere or an oxygen atmosphere and the like.

[0074] The above preparation process and parameters can be adaptively selected and adjusted by those skilled in the art according to actual needs.

[0075] In a fourth aspect, the present application further provides a battery, which comprises the positive electrode material according to the third aspect.

[0076] Compared with the related art, the present application has the following beneficial effects:

[0077] The preparation method provided in the application prevents agglomeration between crystal nuclei by step-by-step growth of precursor particles and controlling the timing of adding a crystal growth inducer, thereby ensuring the sphericity of the precursor; the crystal growth inducer is added in the first coprecipitation reaction process, which allows directional growth of the crystal at the initial stage of crystal nucleation and growth, forming a structure in which the inner core primary particles are arranged radially, and the structure is loose, porous and has a divergent morphology; no crystal growth inducer is added in the second coprecipitation reaction process, and the primary particles grown in this stage are relatively thicker than the crystal nucleus primary particles in the first coprecipitation reaction, and the obtained outer particles are relatively dense, thereby reducing the reaction of the positive electrode with the electrolyte during the cycle process, reducing gas production, and improving the safety and cycle performance of the material; and the inner core is loose and porous and arranged radially, which allows rapid extraction of Li+ during the cycle process, thereby increasing the rate performance of the material.

[0078] Other aspects can become apparent from the following description, which, when taken in conjunction with the drawings, set forth various embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0079] The accompanying drawings are included to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0080] FIG. 1 is an SEM image of the positive electrode precursor material provided in Example 1.

[0081] FIG. 2 is an SEM image of the cross section of the positive electrode precursor material provided in Example 1. DETAILED DESCRIPTION

[0082] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0083] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the present application are intended to cover non-exclusive inclusion.

[0084] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0085] Example 1

[0086] The present embodiment provides a preparation method of a positive electrode precursor material, and the preparation method is as follows:

[0087] (1) Prepare a nickel-cobalt-manganese metal salt solution A with a total concentration of 2 mol / L of nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 0.98:0.01:0.01, prepare an ammonia complexing agent solution with a concentration of 1 mol / L, prepare an OH - concentration of 2 mol / L (sodium hydroxide), and prepare a zirconium sulfate solution (doping salt solution) with a concentration of 2 mol / L;

[0088] (2) Add 400 L of pure water, ammonia water and alkali solution and 0.5 kg of crystal growth inducer triethylamine as a bottom liquid to maintain the stability of the system in a 1000 L reactor;

[0089] The mixed solution A, the ammonia complexing agent and the liquid alkali solution are added to the reactor at a flow rate of 15 kg / h, 5 kg / h and 2 kg / h respectively, and the first co-precipitation reaction is carried out at 40°C. The pH of the reaction is maintained at 10.5, the ammonia concentration is 11 g / L, and the stirring speed is 300 r / min. When the average particle size of the precursor reaches 6 μm, the first co-precipitation reaction is stopped, and the crystal nucleus is obtained;

[0090] (3) Change the feeding flow rate, continue to add the mixed solution A, the ammonia complexing agent, the precipitant solution and the zirconium sulfate solution to the reactor at a flow rate of 30 kg / h, 10 kg / h, 5 kg / h and 1.5 kg / h respectively, and carry out the second co-precipitation reaction at 50°C (without adding crystal growth inducer), maintain the pH of the reaction at 9.8, the ammonia concentration at 9 g / L, and the stirring speed at 200 r / min. The reaction is stopped when the average particle size of the particles reaches 15 μm, and the spherical precursor Ni 0.97 Co 0.01 Mn 0.01 Zr 0.01 (OH)2with an average particle size of 15 μm is obtained after filtration, washing and drying. The inner core (i.e. the crystal nucleus) is in a divergent shape and has a loose accumulation, and the outer part has a dense structure.

[0091] Figure 1 shows the SEM image of the positive electrode precursor material provided in Example 1. As can be seen from Figure 1, the positive electrode precursor material prepared by the preparation method provided in the application has high sphericity and uniform particle size.

[0092] Figure 2 shows the SEM image of the cross section of the positive electrode precursor material provided in Example 1. As can be seen from Figure 2, the internal grains of the positive electrode precursor material prepared by the preparation method provided in the application are arranged radially, loose and porous, and the outer structure is more dense.

[0093] Example 2

[0094] The embodiment provides a preparation method of a positive electrode precursor material, and the preparation method is as follows:

[0095] (1) nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a nickel-cobalt-manganese metal salt solution A with a total metal ion concentration of 3 mol / L according to a molar ratio of 0.88:0.05:0.07, an ammonia complexing agent solution with a concentration of 2 mol / L is prepared, an OH - concentration of 2 mol / L is prepared, a zirconium sulfate solution (doping salt solution) with a concentration of 2 mol / L is prepared;

[0096] (2) 400 L of pure water, ammonia water and alkali solution and 0.8 kg of crystal growth inducer triethylamine are added into a 1000 L reactor as a bottom liquid to maintain the stability of the system;

[0097] The mixed solution A, the ammonia complexing agent and the liquid alkali solution are added into the reactor at flow rates of 20 kg / h, 7.5 kg / h and 3 kg / h respectively, a first co-precipitation reaction is carried out at 45 DEG C, 300 g of triethylamine is added every 4 h to maintain the pH of the reaction at 11.8 and the ammonia concentration at 9 g / L, and the stirring speed is 350 r / min; when the average particle size of the precursor reaches 4 μm, the first co-precipitation reaction is stopped, and a crystal nucleus is obtained;

[0098] (3) the feeding flow rate is changed, the mixed solution A, the ammonia complexing agent, the precipitant solution and the magnesium sulfate solution are continuously added into the reactor at flow rates of 40 kg / h, 15 kg / h, 7 kg / h and 5 kg / h respectively, a second co-precipitation reaction is carried out at 50 DEG C (without adding a crystal growth inducer), the pH of the reaction is maintained at 10.5, the ammonia concentration is maintained at 7 g / L, the stirring speed is 280 r / min, and the reaction is stopped when the average particle size of the particles reaches 10 μm; after filtration, washing and drying, a spherical precursor Ni 0.87 Co 0.04 Mn 0.06 Mg 0.03 (OH)2 with an average particle size of 10 μm is obtained, the inner core (i.e. the crystal nucleus) has a divergent shape and a loose stacking structure, and the outer part has a dense stacking structure.

[0099] Example 3

[0100] The embodiment provides a preparation method of a positive electrode precursor material, and the preparation method is as follows:

[0101] (1) nickel sulfate, cobalt sulfate and manganese sulfate are prepared into a nickel-cobalt-manganese metal salt solution A with a total metal ion concentration of 1 mol / L according to a molar ratio of 0.98:0.01:0.01, an ammonia complexing agent solution with a concentration of 1 mol / L is prepared, an OH -Liquid alkali solution (sodium hydroxide) with a concentration of 1 mol / L; zirconium sulfate solution (doping salt solution) with a concentration of 1 mol / L was prepared;

[0102] (2) 400 L of pure water, ammonia water and alkali solution and 1 kg of crystal growth inducer triethylamine were added into a 1000 L reactor as a bottom liquid to maintain the stability of the system;

[0103] The mixed solution A, ammonia water complexing agent and liquid alkali solution were added into the reactor at a flow rate of 30 kg / h, 10 kg / h and 5 kg / h respectively, and the first co-precipitation reaction was carried out at 55°C. 500 g of triethylamine was added every 4 h to maintain the pH of the reaction at 10.5 and the ammonia concentration at 10 g / L, and the stirring speed was 250 r / min. When the average particle size of the precursor reached 3 μm, the first co-precipitation reaction was stopped, and the crystal nucleus was obtained;

[0104] (3) The flow rate was changed, and the mixed solution A, ammonia water complexing agent, precipitant solution and zirconium sulfate solution were continuously added into the reactor at a flow rate of 50 kg / h, 20 kg / h, 10 kg / h and 10 kg / h respectively, and the second co-precipitation reaction was carried out at 55°C (without adding crystal growth inducer). The pH of the reaction was maintained at 9.8, the ammonia concentration was 8 g / L, the stirring speed was 150 r / min, and the reaction was stopped when the average particle size of the particles reached 5 μm. After filtration, washing and drying, the spherical precursor Ni 0.97 Co 0.01 Mn 0.01 Zr 0.01 (OH)2, the inner core (i.e. the crystal nucleus) was in a divergent shape and the accumulation was loose, and the outside was in a dense structure.

[0105] Example 4

[0106] The difference between this example and Example 1 is that no crystal growth inducer is added to the bottom liquid in step (2) of this example.

[0107] The rest of the preparation method and parameters are consistent with those of Example 1.

[0108] Example 5

[0109] The difference between this example and Example 1 is that the amount of crystal growth inducer added to the bottom liquid in step (2) of this example is 1.5 kg.

[0110] The rest of the preparation method and parameters are consistent with those of Example 1.

[0111] Example 6

[0112] The difference between this example and Example 1 is that in step (2) of this example, the crystal growth inducer is continuously added during the first co-precipitation reaction process at a feed rate of 50 g / h.

[0113] The remaining preparation methods and parameters are consistent with those of Example 1.

[0114] Example 7

[0115] The difference between this example and Example 1 is that in step (2) of this example, the crystal growth inducer is added in 200 g portions every 10 h during the first co-precipitation reaction process.

[0116] The remaining preparation methods and parameters are consistent with those of Example 1.

[0117] Example 8

[0118] The difference between this example and Example 1 is that in step (2) of this example, no crystal growth inducer is added in addition to the base solution during the first co-precipitation reaction process.

[0119] The remaining preparation methods and parameters are consistent with those of Example 1.

[0120] Example 9

[0121] The difference between this example and Example 1 is that in step (2) of this example, the crystal growth inducer is added in 50 g portions every 4 h during the first co-precipitation reaction process.

[0122] The remaining preparation methods and parameters are consistent with those of Example 1.

[0123] Example 10

[0124] The difference between this example and Example 1 is that in step (2) of this example, the crystal growth inducer is added in 1 kg portions every 4 h during the first co-precipitation reaction process.

[0125] The remaining preparation methods and parameters are consistent with those of Example 1.

[0126] Example 11

[0127] The difference between this example and Example 1 is that in step (3) of this example, the feed rates of the mixed solution A and the ammonia complexing agent solution and the precipitant solution during the second co-precipitation reaction process are consistent with those during the first co-precipitation reaction process.

[0128] The remaining preparation methods and parameters are consistent with those of Example 1.

[0129] Comparative Example 1

[0130] The difference between the present comparative example and Example 1 is that, in the preparation method provided by the present comparative example, no crystal growth inducer is added in the stage of the first coprecipitation reaction in the base solution.

[0131] The rest of the preparation method and parameters remain the same as those in Example 1.

[0132] Comparative Example 2

[0133] The difference between the present comparative example and Example 1 is that, in the preparation method provided by the present comparative example, the crystal growth inducer is added in the stage of the second coprecipitation reaction, and still 30 mL of the crystal growth inducer is added every 5 h, and the base solution does not contain the crystal growth inducer.

[0134] The rest of the preparation method and parameters remain the same as those in Example 1.

[0135] [Preparation of positive electrode material]

[0136] The positive electrode precursor materials provided by Examples 1-11 and Comparative Examples 1-2 are respectively calcined with lithium hydroxide, the ratio of the precursor to the lithium source is 1:1.5, and they are uniformly mixed by a high-speed mixer, sintered in a box furnace under an air atmosphere, the sintering temperature is 800°C, the high-temperature sintering time is 12 h, and after cooling to room temperature, they are crushed and sieved to obtain the positive electrode materials.

[0137] [Preparation and performance test of lithium ion battery]

[0138] Preparation of lithium ion battery:

[0139] The positive electrode materials provided by Examples 1-11 and Comparative Examples 1-2, conductive carbon black SP (TIMCAL), and polyvinylidene fluoride PVDF (HSV900) are mixed in a mass ratio of 90:5:5, a solvent is N-methyl pyrrolidone, and the mixture is stirred to form a slurry. The slurry is uniformly coated on an aluminum foil by using a doctor blade with a coating gap of 100 μm. After coating, the coated foil is first dried by blowing air at 120°C, then rolled, and finally the dried electrode sheet is cut into a Φ12 circular electrode sheet. After vacuum drying at 120°C, the weight of the electrode sheet is measured to obtain the positive electrode sheet of the button half battery. The negative electrode is a Φ14 metal lithium sheet, the separator is a Φ19 PP microporous membrane (Celgard 2400), and the electrolyte is a lithium battery basic electrolyte, i.e., EC and DEC are mixed as a mixed solvent in a volume ratio of 1:1, and 1.1 mol / L of LiPF6 is added. The positive electrode sheet, the metal lithium sheet, the separator, and the electrolyte are assembled to obtain the button cell.

[0140] Performance test of button cell: The charge and discharge test capacity is carried out at 0.1C, and the charge and discharge cycle test is carried out at 1C. The test results are shown in Table 1.

[0141] Table 1

[0142] From Table 1, it can be seen that:

[0143] From the data results of Example 1 and Example 4, it can be seen that the addition of no crystal growth inducer in the base solution is not conducive to the formation of the loose and porous structure inside the precursor particles, thereby causing the capacity and cycle performance to decrease.

[0144] From the data results of Example 1 and Example 5, it can be seen that the addition of too much crystal growth inducer in the base solution will also affect the structural stability of the material, thereby causing the performance to decrease.

[0145] From the data results of Example 1 and Example 6, it can be seen that during the first coprecipitation reaction process, the continuous addition of the crystal growth inducer cannot guarantee the concentration of the crystal growth inducer in the system, thereby affecting the exertion of the electrochemical performance.

[0146] From the data results of Example 1 and Examples 7-10, it can be seen that by adjusting the addition time and amount of the crystal growth inducer in addition to the base solution in the first coprecipitation reaction process, the ability of the crystal growth inducer to react and complex with the precipitator at the initial stage of the reaction can be further improved, thereby causing the crystal to present directional growth, guaranteeing the concentration of the crystal growth inducer in the system, and further improving the electrochemical performance of the battery.

[0147] From the data results of Example 1 and Example 11, it can be seen that by adjusting the feed flow of the raw materials in different reaction stages, the sphericity of the positive electrode precursor material particles can be guaranteed, and the structural stability can also be guaranteed, thereby obtaining a positive electrode material with stable structure and excellent performance.

[0148] From the data results of Example 1 and Comparative Examples 1 and 2, it can be seen that without the addition of the crystal growth inducer, it is difficult to realize the structure of the precursor material with a loose and porous interior and a relatively dense exterior, thereby failing to improve the safety performance, cycle performance, and rate performance of the positive electrode material; and if the addition time of the crystal growth inducer is adjusted, the positive electrode precursor will have a more loose exterior, and the problem of gas generation of the positive electrode material cannot be solved.

[0149] In summary, the preparation method provided in the application prevents agglomeration between crystal nuclei by step-by-step growth of precursor particles and controlling the timing of adding the crystal growth inducer, ensuring the sphericity of the precursor; the crystal growth inducer is added in the first coprecipitation reaction process, allowing directional growth of the crystal at the initial stage of crystal nucleation and growth, forming a structure of the inner core primary particles arranged in a radial direction, and the structure is loose, porous and in a divergent morphology; no crystal growth inducer is added in the second coprecipitation reaction process, and the primary particles grown in this stage are relatively thicker than the crystal nucleus primary particles in the first coprecipitation reaction, and the obtained outer particles are relatively dense, so that the positive electrode reduces the reaction with the electrolyte during the cycle process, reduces gas production, and improves the safety and cycle performance of the material; and the inner core is loose and porous, and arranged in a radial direction, allowing fast deintercalation of Li+ during the cycle process, and increasing the rate performance of the material.

[0150] The applicant declares that the above description is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed in the application, which can be easily thought of by any person skilled in the art, falls within the protection scope and disclosure scope of the application.

Claims

1. A method for preparing a positive electrode precursor material, comprising the following steps: adding a first main metal element salt solution, a first precipitant solution and a first complexing agent solution into a bottom liquid in parallel, and performing a first co-precipitation reaction, wherein a crystal growth inducer is added during the first co-precipitation reaction to obtain crystal nuclei; after the first co-precipitation reaction, adding a second main metal element salt solution, a second precipitant solution and a second complexing agent solution in parallel to continue the second co-precipitation reaction, thereby obtaining the positive electrode precursor material.

2. The production method according to claim 1, wherein The first main metal element comprises nickel, and further comprises any one or a combination of at least two of cobalt, manganese or aluminum. Optionally, the molar proportion of nickel in the first main metal element is 30-99%. Optionally, the concentration of the first main metal element salt solution is 1-4 mol / L. Optionally, the concentration of the first precipitant solution is 1-3 mol / L. Optionally, the concentration of the first complexing agent solution is 1-3 mol / L. Optionally, the feeding flow rate of the first main metal element salt solution is 15-30 kg / h. Optionally, the feeding flow rate of the first precipitant solution is 5-10 kg / h. Optionally, the feeding flow rate of the first complexing agent solution is 2-5 kg / h.

3. The production method according to claim 1 or 2, wherein The bottom liquid comprises a solvent and a crystal growth inducer. Optionally, the concentration of the crystal growth inducer in the bottom liquid is 0.5-1 g / L. Optionally, the crystal growth inducer comprises triethylamine. Optionally, the crystal growth inducer is added intermittently during the first co-precipitation reaction. Optionally, the crystal growth inducer is added every 4 h during the first co-precipitation reaction. Optionally, the amount of the crystal growth inducer added each time during the first co-precipitation reaction is 0.1-0.5 kg.

4. The production process according to any one of claims 1 to 3, wherein The reaction temperature of the first co-precipitation reaction is 40-70℃. Optionally, the pH value of the first co-precipitation reaction is 10-12. Optionally, the stirring speed of the first co-precipitation reaction is 200-380 r / min. Optionally, the average particle size of the crystal nuclei is 3-8 μm.

5. The production process according to any one of claims 1 to 4, wherein The second main metal element comprises nickel, and further comprises any one or a combination of at least two of cobalt, manganese or aluminum. Optionally, the molar proportion of nickel in the second main metal element is 30-99%. Optionally, the second co-precipitation process further comprises adding a doping salt solution in parallel. Optionally, the concentration of the second main metal element salt solution is 1-4 mol / L. Optionally, the concentration of the second precipitant solution is 1-3 mol / L. Optionally, the concentration of the second complexing agent solution is 1-3 mol / L. Optionally, the concentration of the doping salt solution is 1-4 mol / L. Optionally, the feeding flow rate of the first main metal element salt solution is 30-50 kg / h. Optionally, the feeding flow rate of the first precipitant solution is 10-20 kg / h. Optionally, the feeding flow rate of the first complexing agent solution is 5-10 kg / h. Optionally, the feeding flow rate of the doping salt solution is 1-10 kg / h.

6. The method of making according to any one of claims 1-5, wherein, The reaction temperature of the second co-precipitation reaction is 40-70°C; Optionally, the pH value of the second co-precipitation reaction is 9-11; Optionally, the stirring speed of the second co-precipitation reaction is 150-300 r / min; Optionally, the average particle size of the positive electrode precursor material is 5-18 μm.

7. The preparation method according to any one of claims 1-6, comprising the following steps: The first main metal element salt solution with a flow rate of 15-30 kg / h and a concentration of 1-4 mol / L, the first precipitant solution with a flow rate of 5-10 kg / h and a concentration of 1-3 mol / L, and the first complexing agent solution with a flow rate of 2-5 kg / h and a concentration of 1-3 mol / L are added into a bottom liquid in parallel, the bottom liquid comprises a crystal growth inducer with a concentration of 0.5-1 g / L, and the first co-precipitation reaction is carried out at 40-70°C and at a speed of 200-380 r / min in an environment with a pH value of 10-12; during the first co-precipitation reaction, the crystal growth inducer is added every 4 h, and the amount of each addition is 0.1-0.5 kg, so as to obtain crystal nuclei with an average particle size of 3-8 μm; After the first co-precipitation reaction, the second main metal element salt solution with a flow rate of 30-50 kg / h and a concentration of 1-4 mol / L, the second precipitant solution with a flow rate of 10-20 kg / h and a concentration of 1-3 mol / L, the second complexing agent solution with a flow rate of 5-10 kg / h and a concentration of 1-3 mol / L, and the dopant solution with a flow rate of 1-10 kg / h and a concentration of 1-4 mol / L are added in parallel, and the second co-precipitation reaction is continued at 40-70°C and at a speed of 150-300 r / min in an environment with a pH value of 9-11, so as to obtain the positive electrode precursor material with an average particle size of 5-18 μm.

8. A positive electrode precursor material, wherein the positive electrode precursor material is prepared by the preparation method according to any one of claims 1-7; the positive electrode precursor material comprises an inner core and an outer shell; the inner core is a porous structure; and the compactness of the outer shell is higher than that of the inner core.

9. A positive electrode material, wherein, The positive electrode material is obtained by mixing and sintering the positive electrode precursor material according to claim 8 and a lithium source.

10. A battery comprising the positive electrode material according to claim 9.

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