Positive electrode material precursor and preparation method and application thereof

Abstract

The invention discloses a positive electrode material precursor as well as a preparation method and application thereof, and relates to the technical field of lithium ion battery positive electrode materials. The positive electrode material precursor comprises precursor particles, the precursor particles are formed by aggregating a plurality of first particles, each first particle is of a core-shell structure, and each core-shell structure is provided with an inner core and a surface layer; the inner core is provided with a compact seed crystal; the surface layer is provided with a plurality of whiskers, and pores are formed between the adjacent whiskers. Therefore, a large-particle precursor which is high in agglomeration, porous, loose in surface appearance and in a puff shape is formed, and industrial production is facilitated.

Description

Technical Field

[0001] This application belongs to the technical field of cathode materials for lithium-ion batteries, and particularly relates to a cathode material precursor, a preparation method thereof, and an application thereof. Background Art

[0002] With the increase in the sales volume of new energy vehicles and the stable growth of markets such as power tools, the application of ternary cathode materials has maintained rapid growth. The performance of ternary cathode materials (such as lithium nickel cobalt manganese oxide) largely depends on the performance of ternary precursors (such as nickel cobalt manganese hydroxide). Currently, one of the main development trends of ternary cathode materials is single crystallization. Using single crystal materials can reduce grain boundaries, reduce side reactions, and increase the tap density, thereby improving the energy density and making the battery have a higher cycle life.

[0003] However, the preparation process of single crystal materials is complex. Compared with the preparation of polycrystalline materials, preparing single crystal materials requires a higher sintering temperature, and high temperature is prone to cause the mixing of nickel and lithium. At the same time, during the sintering process, primary particles will grow and secondary particles will adhere, so grinding treatment is required after sintering. And if the sintering is insufficient and quasi-single crystals are formed, the material will not achieve the expected effect. Moreover, current single crystal materials are mainly obtained by sintering small particle precursors, and traditional small particle precursors are prone to multi-stage agglomeration and poor particle uniformity during the reaction, resulting in a high sintering temperature required for the sintering process, insufficient sintering, increased sintering difficulty, and the mixing of nickel and lithium during the high temperature process, thereby causing the performance of the cathode material not to achieve the expected effect.

[0004] Therefore, there is an urgent need to provide a ternary precursor and a preparation method thereof to solve the above problems. Summary of the Invention

[0005] The purpose of this application is to overcome the above deficiencies of the prior art, and provide a cathode material precursor, a preparation method thereof, and an application thereof, to prepare a large particle precursor with high agglomeration, porous, and loose surface morphology like a puff. The large particle precursor is formed by the agglomeration growth of small particles, and the surface layer of the small particles has more pores, which is beneficial for lithium elements to enter the interior of the particles during the sintering process, making the sintering more sufficient, thereby reducing the generation of quasi-single crystal particles and reducing the sintering difficulty of the precursor. At the same time, there are relatively dense crystal seeds inside the small particles, which are relatively easier to break after sintering, and the breaking is relatively more uniform.

[0006] To achieve the above application purpose, in the first aspect of this application, a cathode material precursor is provided. The cathode material precursor includes precursor particles, and the precursor particles are agglomerated by a plurality of first particles. The first particles have a core-shell structure, and the core-shell structure has a core and a surface layer;

[0007] The core has dense crystal seeds;

[0008] The surface layer has a plurality of whiskers, and there are pores between adjacent whiskers.

[0009] Further, the ratio range of the particle size of the seed crystal to the particle size of the first particle is 30-40%.

[0010] Further, the ratio range of the particle size of the first particle to the particle size of the precursor particle is 20-50%.

[0011] Further, the thickness range of the whiskers is 10-30 nm.

[0012] Further, the specific surface area range of the precursor particles is 20-40 m 2 / g.

[0013] Further, each of the precursor particles further includes a shell layer, and the shell layer coats the surface layer of the core-shell structure;

[0014] The thickness range of the shell layer is 0.2-0.5 μm.

[0015] Further, the thickness range of the inner core of the core-shell structure is 4-8 μm.

[0016] In the second aspect of the present application, a cathode material is provided, including the above-mentioned cathode material precursor.

[0017] In the third aspect of the present application, a method for preparing a cathode material precursor is provided, which is made by the following steps:

[0018] Mix a variety of metal ion sources with water to obtain a mixed metal ion solution; and, prepare a first lye and a complexing agent respectively;

[0019] After adding water to the reactor and introducing a protective gas, add the first lye and the complexing agent to form a reaction bottom liquid;

[0020] Add the first lye, the complexing agent and the mixed metal ion solution into the reactor in a co-current manner to carry out a nucleation reaction, and control the reaction atmosphere to be a first atmosphere to form seed crystals; when it is detected that the content of the seed crystals reaches the required target, reduce the pH value of the reaction solution, and control the reaction atmosphere to be a second atmosphere to maintain the growth reaction of the seed crystal particles;

[0021] Continue feeding. When it is detected that the liquid level in the reactor reaches the filtration requirement, filter it, and maintain the liquid level in the reactor stable. And, when it is detected that the particle size of the material in the reactor reaches the required target, stop feeding, and discharge the material to a container;

[0022] Solid-liquid separation is performed on the material in the container, and after the separated filter cake is processed, the precursor of the cathode material is obtained.

[0023] Further, the first atmosphere at least includes the protective gas, and the second atmosphere includes air and the protective gas.

[0024] Further, in the second atmosphere, the air flow rate gradually increases as the solid content of the material increases.

[0025] Further, the air flow rate range of the first atmosphere is 0 - 800 L / h, and the protective gas flow rate range of the first atmosphere is 100 - 800 L / h.

[0026] Further, the air flow rate range of the second atmosphere is 300 - 800 L / h, and the protective gas flow rate range of the second atmosphere is 0 - 300 L / h.

[0027] Further, the complexing agent concentration range for the nucleation reaction is 2.0 - 10.0 g / L.

[0028] Further, the complexing agent concentration range for the growth reaction is 1.0 - 10.0 g / L.

[0029] Further, the flow rate range of the mixed metal ion solution is 0.5 - 40 L / h.

[0030] Further, the flow rate ratio range of the first lye, the complexing agent, and the mixed metal ion solution is 0 - 9:3 - 20:20 - 133.

[0031] Further, the pH range of the reaction solution is 10.0 - 11.5.

[0032] Compared with the prior art, the present application has the following technical effects:

[0033] The precursor of the cathode material provided by the present application is formed by the aggregation and growth of small particles. The surface of the small particles has more pores, which is beneficial for lithium elements to enter the interior of the particles during the sintering process, making the sintering more sufficient. Thus, the generation of quasi-single crystal particles can be reduced, and the sintering difficulty of the precursor can be lowered. At the same time, there are relatively dense crystal seeds inside the small particles, which are relatively easier to break after sintering, and the breaking is relatively more uniform. Therefore, a large-particle precursor of the cathode material with high aggregation, porous, and a loose surface morphology like a puff can be obtained, and this precursor of the cathode material has a super large specific surface area, a large internal porosity, and a low tap density, etc. Description of the Drawings

[0034] To more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 Process flow diagram of a preparation process for a cathode material precursor provided by an embodiment of the present application;

[0036] Figure 2 Structural schematic diagrams of a main reaction kettle, a thickener, a filter rod, a filter pump, and a filter provided by an embodiment of the present application;

[0037] Figures 3 to 8 Electron microscope images of a cathode material precursor at different magnifications provided by Embodiment 1 of the present application;

[0038] Figures 9 to 14 Electron microscope images of a cathode material precursor at different magnifications provided by Embodiment 2 of the present application;

[0039] Figures 15 to 20 Electron microscope images of a cathode material precursor at different magnifications provided by Embodiment 3 of the present application;

[0040] Figures 21 to 26 Electron microscope images of a cathode material precursor at different magnifications provided by Comparative Example 1 of the present application;

[0041] Figures 27 to 32 Electron microscope images of a cathode material precursor at different magnifications provided by Comparative Example 2 of the present application;

[0042] Figures 33 to 38 Electron microscope images of a cathode material precursor at different magnifications provided by Comparative Example 3 of the present application. Specific embodiments

[0043] In order to make the technical problems to be solved, the technical solutions, and the beneficial effects of the present application clearer, the following further details the present application in combination with 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.

[0044] In the present application, the term "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Among them, A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0045] In this application, "at least one" means one or more, and "a plurality of" means two or more. "At least one of the following" or similar expressions mean 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 both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can each be single or multiple.

[0046] It should be understood that in various embodiments of this application, the magnitude of the serial numbers of the various processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0047] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0048] The weight of the relevant components mentioned in the specification of the embodiments of this application can not only refer to the specific content of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of this application is scaled up or down in proportion, it is within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass in the specification of the embodiments of this application can be well-known mass units such as μg, mg, g, kg, etc.

[0049] The terms "first", "second", etc. are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of this application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Thus, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of such features.

[0050] In a first aspect, an embodiment of this application provides a method for preparing a cathode material precursor.

[0051] The method for preparing the cathode material precursor includes the following steps:

[0052] Step 1: Determine the molar ratio of nickel (Ni), cobalt (Co), and manganese (Mn) elements required for the cathode material precursor. After selecting Ni soluble salt, Co soluble salt, and Mn soluble salt according to the molar ratio, mix them with pure water to prepare a mixed metal ion solution with a first concentration; and, respectively prepare a first lye with a second concentration and a complexing agent with a third concentration.

[0053] In practical applications, the mixed metal ion solution includes, but is not limited to, those formed by Ni soluble salt, Co soluble salt, and Mn soluble salt. It can also be from lye or other sources, specifically subject to actual applications.

[0054] The molar ratio range of Ni soluble salt, Co soluble salt, and Mn soluble salt in the above Step 1 can include (88 - 96):(2 - 8):(2 - 8). Exemplarily, the molar ratio of Ni soluble salt, Co soluble salt, and Mn soluble salt can be 88:6:6, 88:4:8, 96:2:2, etc.

[0055] The pure water in the above Step 1 can be deionized water. Further, the deionized water can be hot water.

[0056] The value range of the first concentration in the above Step 1 can include 1.2 - 2.7 mol / L. Exemplarily, the first concentration can be 1.2 mol / L, 1.8 mol / L, 2.3 mol / L, or 2.7 mol / L, etc.

[0057] There is no specific limitation on the first lye in Step 1. Exemplarily, the first lye can be sodium hydroxide (NaOH) solution, etc.

[0058] The value range of the second concentration of the first lye in the above Step 1 can include 1.0 - 13.0 mol / L. Exemplarily, the second concentration can be 1.0 mol / L, 3.0 mol / L, 10.5 mol / L, or 13.0 mol / L, etc.

[0059] There is no specific limitation on the complexing agent in Step 1. Exemplarily, the complexing agent can be ammonia water (NH3·H2O), etc.

[0060] The value range of the third concentration of the complexing agent in the above Step 1 can include 1.0 - 12.0 mol / L. Exemplarily, the third concentration can be 1.0 mol / L, 3.0 mol / L, 6.0 mol / L, or 12 mol / L, etc.

[0061] It should be noted that there is no specific limitation on the order of preparing the mixed metal ion solution with the first concentration, the first alkali solution with the second concentration, and the complexing agent with the third concentration in Step 1. Exemplarily, the mixed metal ion solution with the first concentration can be prepared first, and then the first alkali solution with the second concentration and the complexing agent with the third concentration are respectively prepared; or, the first alkali solution with the second concentration and the complexing agent with the third concentration can be respectively prepared first, and then the mixed metal ion solution with the first concentration is prepared; or, the mixed metal ion solution with the first concentration, the first alkali solution with the second concentration, and the complexing agent with the third concentration can be prepared simultaneously.

[0062] Step 2: Feed water and return water into the reactor.

[0063] There is no specific limitation on the type of reactor in Step 2. Exemplarily, the reactor can be a reaction kettle, etc.

[0064] The above Step 2 of feeding water and returning water into the reactor may include:

[0065] Step 21: Open the jacket of the reaction kettle and feed water and return water.

[0066] Step 3: Add pure water with the first dosage into the reactor, and after introducing a protective gas, add the first alkali solution and the complexing agent at the first temperature and the first stirring speed to form a reaction bottom liquid.

[0067] The value range of the first dosage of pure water in the above Step 3 may include 40 - 200 L. Further, the value range of the first dosage includes 50 - 160 L. Exemplarily, the first dosage can be 50 L, 100 L, or 160 L, etc.

[0068] There is no specific limitation on the protective gas in Step 3. Exemplarily, the protective gas may include nitrogen (N2), etc. The following examples will be described with the protective gas being N2.

[0069] The value range of the pH of the reaction bottom liquid in the above Step 3 may include 11.0 - 12.5 (45 °C). Further, the value range of the pH of the reaction bottom liquid includes 11.5 - 12.3 (45 °C). Exemplarily, the pH value of the reaction bottom liquid can be 11.5 (45 °C), 12.0 (45 °C), or 12.3 (45 °C), etc.

[0070] The value range of the concentration of the complexing agent in the above Step 3 may include 2.0 - 10.0 g / L. Further, the value range of the concentration of the complexing agent includes 4.0 - 9.0 g / L. Exemplarily, the concentration of the complexing agent can be 4.0 g / L, 6.0 g / L, or 9.0 g / L, etc.

[0071] The value range of the first temperature in the above step 3 may include 50 - 70 °C. Exemplarily, the first temperature may be 50 °C, 60 °C, or 70 °C, etc.

[0072] The value range of the first stirring speed in the above step 3 may include 400 - 600 rpm. Exemplarily, the first stirring speed may be 400 rpm, 500 rpm, or 600 rpm, etc.

[0073] Step 4: At the second stirring speed, add the first lye, complexing agent, and mixed metal ion solution into the reactor in a co-current manner according to the first flow ratio to carry out nucleation reaction, and control the reaction temperature to be the first temperature, the reaction atmosphere to be the first atmosphere, the pH value of the reaction solution to be the first pH value, and the concentration of the complexing agent to be the fourth concentration to form crystal seeds; when it is detected that the content of crystal seeds reaches the required target, reduce the first pH value, and control the reaction temperature to be the second temperature, the reaction atmosphere to be the second atmosphere, the pH value of the reaction solution to be the second pH value, and the concentration of the complexing agent to be the fifth concentration to maintain the growth reaction of crystal seed particles in the reactor.

[0074] The first atmosphere in the above step 4 includes at least a protective gas, and the second atmosphere includes a protective gas and air.

[0075] The value range of the addition amount of the mixed metal ion solution in the above step 4 may include 0.5 - 40 L / h. Further, the value range of the addition amount of the mixed metal ion solution includes 1 - 30 L / h. Exemplarily, the addition amount of the mixed metal ion solution may be 1 L / h, 10 L / h, 20 L / h, or 30 L / h, etc.

[0076] The value range of the second stirring speed in the above step 4 may include 50 - 600 rpm. Further, the value range of the second stirring speed includes 100 - 550 rpm. Exemplarily, the second stirring speed may be 100 rpm, 200 rpm, 300 rpm, 400 rpm, or 550 rpm, etc.

[0077] The value range of the first temperature in the above step 4 may include 40.0 - 75.0 °C. Further, the value range of the first temperature includes 45.0 - 65.0 °C. Exemplarily, the first temperature may be 45.0 °C, 55.0 °C, or 65.0 °C, etc.

[0078] The value range of the pH of the reaction solution for the nucleation reaction in the above step 4 may include 11.0 - 12.5 (45 °C). Further, the value range of the pH of the reaction solution for the nucleation reaction includes 11.5 - 12.3 (45 °C). Exemplarily, the pH value of the reaction solution for the nucleation reaction may be 11.5 (45 °C), 12.0 (45 °C), or 12.3 (45 °C), etc.

[0079] The value range of the complexing agent concentration in the nucleation reaction in Step 4 above may include 2.0 - 10.0 g / L. Further, the value range of the complexing agent concentration in the nucleation reaction includes 4.0 - 9.0 g / L. Exemplarily, the complexing agent concentration in the nucleation reaction may be 4.0 g / L, 6.0 g / L, 7.0 g / L, or 9.0 g / L, etc.

[0080] There is no specific limitation on the first atmosphere in Step 4. Exemplarily, the first atmosphere may include N2; or, the first atmosphere may include N2 and air, etc., where air mainly refers to oxygen (O2).

[0081] The value range of the sub - liquid - level nitrogen flow rate of the first atmosphere in Step 4 above may include 100 - 800 L / h. Further, the value range of the sub - liquid - level nitrogen flow rate of the first atmosphere includes 150 - 700 L / h. Exemplarily, the sub - liquid - level nitrogen flow rate of the first atmosphere may be 150 L / h, 300 L / h, 600 L / h, or 700 L / h, etc.

[0082] The value range of the sub - liquid - level air flow rate of the first atmosphere in Step 4 above may include 0 - 800 L / h. Further, the value range of the sub - liquid - level air flow rate of the first atmosphere includes 0 - 700 L / h. Exemplarily, the sub - liquid - level air flow rate of the first atmosphere may be 0 L / h, 300 L / h, 600 L / h, or 700 L / h, etc.

[0083] The value range of the pH of the reaction solution in the growth reaction in Step 4 above may include 10.0 - 11.5 (at 45 °C). Further, the value range of the pH of the reaction solution in the growth reaction includes 10.2 - 11.3 (at 45 °C). Exemplarily, the pH of the reaction solution in the growth reaction may be 10.2 (at 45 °C), 11.0 (at 45 °C), or 11.3 (at 45 °C), etc.

[0084] The value range of the complexing agent concentration in the growth reaction in Step 4 above may include 1.0 - 10.0 g / L. Further, the value range of the complexing agent concentration in the growth reaction includes 3.0 - 9.0 g / L. Exemplarily, the complexing agent concentration in the growth reaction may be 3.0 g / L, 5.0 g / L, 8.0 g / L, or 9.0 g / L.

[0085] The value range of the sub - liquid - level nitrogen flow rate of the second atmosphere in the growth reaction in Step 4 above may include 0 - 300 L / h. Further, the value range of the sub - liquid - level nitrogen flow rate of the second atmosphere includes 0 - 250 L / h. Exemplarily, the sub - liquid - level nitrogen flow rate of the second atmosphere may be 0 L / h, 50 L / h, 100 L / h, or 250 L / h, etc.

[0086] The value range of the sub-surface air flow rate of the second atmosphere in step 4 above may include 300 - 800 L / h. Further, the value range of the sub-surface air flow rate of the second atmosphere includes 350 - 750 L / h. Exemplarily, the sub-surface air flow rate of the second atmosphere may be 350 L / h, 500 L / h, 600 L / h, or 750 L / h, etc.

[0087] Step 4 can control the feeding amounts of N2 and air through an intermittent process to regulate the proportion of the oxidant (air), making the whiskers on the particle surface thinner and the particle porosity higher. In this way, as the synthesis time increases, the oxidation amount can be increased, making the pores inside the particles uniform, and the morphology being a porous puff shape.

[0088] Moreover, since the surface whisker laths are thinner, the particle strength is reduced. During the reaction process, according to the particle size, the stirring speed is reduced to avoid particle breakage caused by stirring.

[0089] Furthermore, during the synthesis process, the reaction pH value, temperature, metal liquid flow rate, alkali flow rate, and complexing agent flow rate are kept stable.

[0090] Step 5, continue feeding according to step 4. When it is detected that the liquid level in the reactor reaches the filtration requirement, start the filter to filter and maintain the liquid level in the reactor stable; when it is detected that the particle size of the material in the reactor reaches the required target, stop feeding the reactor, and continue to stir and age for the first period of time, then discharge the material into the container.

[0091] There is no specific limitation on the type of the above filter. Exemplarily, the filter can be a thickener, etc.

[0092] There is no specific limitation on the type of the above container. Exemplarily, the container can be a qualified slurry tank, a transfer tank, etc.

[0093] The value range of the particle size of the material in the reactor in step 5 above may include 10 - 20 μm. Exemplarily, the particle size of the material may be 10 μm, 15 μm, or 20 μm, etc.

[0094] The value range of the above first period of time may include 1 - 2 h. Exemplarily, the first period of time may be 1 h, 1.5 h, or 2 h, etc.

[0095] Step 6, perform solid-liquid separation on the material in the container, wash the separated filter cake with a second alkali solution, and then rinse it with pure water to obtain a washed filter cake.

[0096] There is no specific limitation on the second alkali solution in step 6. Exemplarily, the second alkali solution can be a NaOH solution, a potassium hydroxide (KOH) solution, etc.

[0097] Step 7: Dry the washed filter cake, and then pass it through a sieve and demagnetize it in sequence to obtain the precursor of the cathode material.

[0098] The embodiment of the present application provides a method for preparing a precursor of a cathode material. By adopting an intermittent process, controlling the feeding amounts of nitrogen and air in the growth reaction stage, and combining with the stirring speed in the reaction process, a large-particle precursor of the cathode material with high agglomeration, porous, and loose surface morphology in the shape of a puff is formed.

[0099] In the related art, when preparing polycrystalline materials, sometimes a mixture of large particles and small particles is considered, while when preparing single-crystalline materials, small particles are often used to avoid problems such as uncertainty about uniformity after processes such as sintering and crushing of large particles. In the embodiment of the present application, large-particle precursors are formed by the agglomeration of small particles with a core-shell structure during the preparation of the precursor. Then, during the sintering process, lithium ions can penetrate into the precursor particles more fully, and the sintering is more complete. When crushed, the large-particle precursors are more likely to be broken into multiple small particles. Thus, not only can the sintering difficulty be reduced, and the nickel-lithium mixing phenomenon during the sintering process be improved, but also, after the large-particle precursors are sintered and crushed for preparing small-particle single-crystalline materials, the sintering process is more complete, the formation of quasi-single crystals can be reduced, side reactions can be reduced, and thus single-crystalline materials with a higher tap density can be obtained. That is, problems such as high sintering difficulty of the precursor of the single-crystallized ternary material and reduction of the generation of quasi-single-crystalline particles can be solved, which is beneficial to industrial production.

[0100] Further, in the growth reaction stage in Step 4, the air flow rate in the second atmosphere in the reaction kettle gradually increases as the solid content of the system increases.

[0101] Thus, by controlling the contents of nitrogen and oxygen in the growth reaction stage, the growth of the seed crystals can be better realized.

[0102] Further, in Step 5, continue feeding according to Step 4. When it is detected that the liquid level in the reactor reaches the filtration requirement, start the filter to filter, and maintain the liquid level in the reactor stable; when it is detected that the particle size of the material in the reactor reaches the required target, stop feeding the reactor, and continue stirring and aging for the first period of time, and then discharge the material into the container, which may include:

[0103] Step 51: Continue feeding according to Step 4. When it is detected that the liquid level in the reactor reaches the filtration requirement, start the filter to filter, and maintain the liquid level in the reactor stable while introducing air; when it is detected that the particle size of the material in the reactor reaches the required target, stop feeding the reactor, and continue stirring and aging for the first period of time, and then discharge the material into the container.

[0104] Thus, by introducing air into the reactor before detecting that the particle size of the material in the reactor reaches the target, a shell layer with a certain thickness can be formed on the precursor of the cathode material, which can improve the surface strength of the precursor of the cathode material, avoid particle breakage of the precursor of the cathode material due to equipment reasons during processes such as washing and drying, and improve the preparation success rate of the precursor of the cathode material.

[0105] In a second aspect, an embodiment of the present application provides a precursor of a cathode material. The precursor of the cathode material includes precursor particles, and the precursor particles are aggregated by a plurality of first particles. The first particles have a core-shell structure, the core-shell structure has a core and a surface layer, the core has dense crystal seeds, the surface layer has a plurality of whiskers, and there are pores between adjacent whiskers.

[0106] The precursor of the cathode material in the embodiment of the present application is applicable to products such as binary cathode material precursors and ternary cathode material precursors.

[0107] In applications, the value range of the ratio of the crystal seed particle size to the first particle size includes 30-40%. There is no specific limitation on the ratio of the crystal seed particle size to the first particle size. Exemplarily, the ratio of the crystal seed particle size to the first particle size can be 30%, 35% or 40%, etc.

[0108] In applications, the value range of the ratio of the particle size of a plurality of aggregated first particles to the particle size of the precursor particles includes 20-50%. There is no specific limitation on the ratio of the particle size of a plurality of aggregated first particles to the particle size of the precursor particles. Exemplarily, the ratio of the particle size of a plurality of aggregated first particles to the particle size of the precursor particles can be 20%, 40% or 50%, etc.

[0109] In practical applications, the precursor particles in the embodiment of the present application are formed by the aggregation and growth of small particles. There are relatively dense crystal seeds inside the aggregated small particles, which are relatively easier to break after sintering, and the breakage can be relatively more uniform.

[0110] The molecular general formula of the above precursor of the cathode material can be Ni x Co y Mn z (OH)2; where x + y + z = 1, and 0.6 ≤ x ≤ 1.0, 0 < y ≤ 0.20, 0 < z ≤ 0.40.

[0111] The thickness range of the core of the above core-shell structure can include 4-8 μm. Exemplarily, the core of the core-shell structure can be 4 μm, 5 μm, 6 μm, 7 μm or 8 μm, etc.

[0112] In practical applications, the surface layer of the small particles in the embodiment of the present application has more pores, which is beneficial to the entry of lithium elements into the particle interior during the sintering process, making the sintering more sufficient, thereby reducing the generation of quasi-single crystal particles and reducing the sintering difficulty of the precursor.

[0113] An embodiment of the present application provides a precursor of a cathode material. The precursor particles are formed by the agglomeration growth of small particles. The surface layer of the small particles has more pores, which is beneficial for lithium elements to enter the interior of the particles during the sintering process, making the sintering more sufficient. Thus, the generation of quasi-single crystal particles can be reduced, and the sintering difficulty of the precursor can be lowered. At the same time, relatively dense crystal seeds exist inside the small particles, and after sintering, they are relatively easier to break, and the breakage can be relatively more uniform. Therefore, a large-particle cathode material precursor with high agglomeration, porous, and loose surface morphology in the shape of a puff can be obtained, and this cathode material precursor has characteristics such as a super-large specific surface area, a large internal porosity, and a low tap density. Thus, a single crystal material with a high compaction density can be obtained, and the energy density can be increased, making the battery cycle life higher.

[0114] Furthermore, the value range of the whisker thickness includes 10 - 30 nm; the value range of the specific surface area of the precursor particles includes 20 - 40 m 2 / g.

[0115] There is no specific limitation on the above-mentioned whisker thickness. Exemplarily, the whisker thickness can be 10 nm, 20 nm, or 30 nm, etc.

[0116] There is no specific limitation on the specific surface area of the above-mentioned precursor particles. Exemplarily, the specific surface area of the precursor particles can be 20 m 2 / g, 30 m 2 / g, or 40 m 2 / g, etc.

[0117] An embodiment of the present application provides a precursor of a cathode material. The whiskers on the surface layer of the small particles of this cathode material precursor are relatively thin, and the morphology is in the shape of a porous puff. The relatively thin whiskers and the relatively large specific surface area reduce the particle strength, thereby reducing the sintering difficulty. Thus, the sintering can be made more sufficient; and due to the reduction of the particle strength, the breakage difficulty after sintering is reduced, so that the particles are easy to break.

[0118] Furthermore, the precursor particles further include a shell layer, and the shell layer coats the surface layer of the core-shell structure; the value range of the shell layer thickness includes 0.2 - 0.5 μm.

[0119] There is no specific limitation on the above-mentioned shell layer thickness. Exemplarily, the shell layer thickness can be 0.2 μm, 0.3 μm, or 0.5 μm, etc.

[0120] An embodiment of the present application provides a precursor of a cathode material. The shell layer outside the surface layer can provide the strength of the surface of the large precursor particles, avoiding the breakage of the cathode material precursor particles caused by equipment reasons during processes such as washing and drying, thereby being able to improve the preparation success rate of the cathode material precursor particles; and since the shell layer is relatively thin, the influence on the normal material sintering and performance is relatively low.

[0121] In a third aspect, an embodiment of the present application provides a cathode material, which includes the above-mentioned cathode material precursor.

[0122] An embodiment of the present application provides a cathode material. During the sintering process, lithium ions can penetrate into the precursor particles more fully, and the sintering is more complete. When crushing, large particle precursors are more likely to be broken into multiple small particles. Therefore, not only can the sintering difficulty be reduced, and the nickel-lithium mixing phenomenon during the sintering process can be improved, but also, after the large particle precursors are sintered and crushed to prepare small particle single crystal materials, the sintering process is more complete, the formation of quasi single crystals can be reduced, side reactions can be reduced, thereby obtaining a cathode material with a higher tap density, and it is conducive to industrial production.

[0123] In a fourth aspect, an embodiment of the present application provides a secondary battery, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. Among them, the positive electrode plate includes a current collector and a cathode material coated on the current collector. The cathode material includes the above-mentioned cathode material precursor. The separator is arranged between the positive electrode plate and the negative electrode plate, and the electrolyte is filled in the secondary battery.

[0124] An embodiment of the present application provides a secondary battery, which has a relatively high cycle life and very good performance.

[0125] The following provides a specific preparation method of a cathode material precursor, as Figure 1 shown, including the following steps:

[0126] Step 1, solution preparation stage.

[0127] According to the molar ratio of Ni element, Co element, and Mn element in the required nickel cobalt manganese hydroxide, Ni soluble salt, Co soluble salt, and Mn soluble salt are selected as raw materials, and then pure water is added to prepare a nickel cobalt manganese salt mixed solution with a concentration range of 1.2 - 2.7 mol / L.

[0128] Among them, the molar ratio range of the Ni soluble salt, Co soluble salt, and Mn soluble salt is (88 - 96):(2 - 8):(2 - 8).

[0129] Prepare a NaOH solution with a concentration range of 1.0 - 13.0 mol / L as the alkali solution.

[0130] Prepare NH₃·H₂O with a concentration range of 1.0 - 12.0 mol / L as the complexing agent.

[0131] Step 2, open the jacket of the main reaction kettle with a volume range of 180 - 220 L, and let water in and out.

[0132] Step 3, formation of the reaction bottom liquid stage.

[0133] Add pure water with a volume range of 90 - 110 L to the main reaction kettle, and introduce N2 into the main reaction kettle. Control the temperature range of the main reaction kettle to be 50 - 70 °C, and the stirring speed range to be 400 - 600 rpm. Then add the NaOH solution and NH3·H2O solution prepared in Step 1 to form a reaction bottom liquid.

[0134] Step 4: Preparation stage of the cathode material precursor particles.

[0135] Step 41: Under continuous stirring, add the NaOH solution, NH3·H2O solution, and mixed metal ion solution prepared in Step 1 into the main reaction kettle in a co-current manner according to the first flow rate ratio. React under a stirring speed range of 450 - 550 rpm, and control the reaction temperature, reaction atmosphere, pH of the reaction solution, and ammonia concentration to form seeds in the reaction kettle.

[0136] Among them, the first flow rate ratio range is (0 - 9):(3 - 20):(20 - 133).

[0137] Step 42: pH reduction and stable growth stage: When the amount of seeds reaches the required target, reduce the pH of the reaction solution, and continue to control the reaction temperature, reaction atmosphere, pH of the reaction solution, and ammonia concentration to maintain the growth of seed particles in the main reaction kettle.

[0138] Step 5: Continue feeding according to Step 4. As Figure 2 shown, when the liquid level in the main reaction kettle reaches the filtration requirement, start the thickener to start filtration, maintain the liquid level in the main reaction kettle stable. When it is detected that the particle size of the material in the main reaction kettle reaches the required requirement, stop feeding the main reaction kettle, and continue stirring and aging for 1 - 2 h. Then discharge the seeds into the qualified slurry tank.

[0139] Step 6: Perform solid-liquid separation on the slurry in the qualified slurry tank in Step 5. Wash the separated filter cake with NaOH solution or KOH solution, and then rinse it with pure water to obtain a washed filter cake.

[0140] Step 7: After drying the washed filter cake in Step 6 with a drying device, pass it through a sieve and demagnetization in sequence to obtain porous, puff-shaped nickel cobalt manganese hydroxide.

[0141] The following uses multiple specific examples to illustrate the cathode material precursor and its preparation method and application in the embodiments of the present application.

[0142] Example 1

[0143] This example provides a preparation method of a cathode material precursor, including the following steps:

[0144] Step 1: Select nickel soluble sulfate, cobalt soluble sulfate, and manganese soluble sulfate in a molar ratio of 88:6:6, mix them with deionized water, and prepare a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0145] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0146] Prepare an NH₃·H₂O solution with a concentration of 6 mol / L.

[0147] Maintain the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution at a constant temperature of 25 °C.

[0148] Step 2: Open the jacket of the reactor with a volume of 180 L, and let water in and out.

[0149] Step 3: Add 100 L of hot pure water into a reactor with a volume of 200 L, control the reactor temperature at 60 °C, and the stirring speed at 500 rpm. Then pump the NaOH solution and the NH₃·H₂O solution into the reactor. The concentration of the NH₃·H₂O solution is maintained at 6.0 g / L before adding alkali, and the initial pH at 45 °C is 11.60 to prepare the reaction bottom liquid of the reactor.

[0150] After the reaction starts, set the flow rates of the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution to 9 mL / min, 3 mL / min, and 20 mL / min respectively, and continuously pump them into the 60 °C constant temperature reactor through the feeding tank for reaction. At a stirring speed of 500 rpm, adjust the flow rate of the NaOH solution to make the pH value of the synthesis system stable at 11.5, adjust the flow rate of the NH₃·H₂O solution to maintain the NH₃·H₂O concentration in the synthesis system at 4.0 g / L, adjust the flow rate of N₂ under the liquid in the reactor atmosphere to 150 L / h and the flow rate of air under the liquid to 100 L / h, and maintain the nucleation time for 3 min.

[0151] At a stirring speed of 500 rpm, close the flow rate of the NaOH solution, quickly adjust the pH value to 10.2 and then restore it, adjust the flow rate of the NH₃·H₂O solution to maintain the NH₃·H₂O concentration in the synthesis system at 4.0 g / L, and adjust the flow rate of N₂ under the liquid in the reactor atmosphere to 150 L / h and the flow rate of air under the liquid to 100 L / h.

[0152] After the reaction starts for 1 h, adjust the flow rate of the mixed metal sulfate solution, and slowly increase it to 267 mL / min in 6 h. Synchronously adjust the flow rates of the NaOH solution and the NH₃·H₂O solution to stabilize the pH value at 10.2 and the ammonia value at 3.0. After the reaction starts for 4 h, adjust the flow rate of the submersible N₂ in the reaction kettle atmosphere to 100 L / h and the submersible air flow rate to 150 L / h. Increase the oxygen content in the reaction atmosphere by 1% every 4 h. Gradually reduce the stirring speed according to the particle size D50 of the material. When D50 reaches 8 μm, reduce the stirring speed and maintain it at 200 rpm. When D50 reaches 13.5 - 13.6 μm, stop the reaction to obtain a porous, puffy large-particle ternary precursor slurry.

[0153] Step 5: Discharge the ternary precursor slurry that meets the particle size requirements into a transfer tank and stir it.

[0154] Step 6: Wash the ternary precursor slurry alternately with alkali and pure water.

[0155] Step 7: Uniformly distribute the ternary precursor slurry in a drying device for drying. The drying temperature is 120 °C, the drying time is 12 h, and the number of mesh of the sieve is 325 - mesh double - layer.

[0156] Through the above steps, a Figures 3 to 8 positive electrode material precursor with high agglomeration, a porous puffy morphology, and an average particle size of 10 - 20 μm can be obtained.

[0157] Example 2

[0158] This example provides a method for preparing a positive electrode material precursor, which includes the following steps:

[0159] Step 1: Select Ni soluble sulfate, Co soluble sulfate, and Mn soluble sulfate according to a molar ratio of 88:4:8, and mix them with deionized water to prepare a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0160] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0161] Prepare an NH₃·H₂O solution with a concentration of 6 mol / L.

[0162] Maintain the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution at a constant temperature of 25 °C.

[0163] Step 2: Open the jacket of the reaction kettle with a volume of 180 L, and let water in and out.

[0164] Step 3: Add 100 L of hot pure water into a reactor with a volume of 200 L, control the temperature of the reactor at 60 °C, and the stirring speed at 500 rpm. Then pump the NaOH solution and the NH₃·H₂O solution into the reactor. The concentration of the NH₃·H₂O solution is maintained at 6.0 g / L before adding the alkali, and the initial pH at 45 °C is 11.60 to prepare the reaction bottom liquid of the reactor.

[0165] Step 4: After starting the reaction, set the flow rates of the NaOH solution, the NH₃·H₂O solution, and the mixed metal sulfate solution to 0 mL / min, 20 mL / min, and 133 mL / min respectively, and continuously pump them into the 60 °C constant-temperature reactor through the feeding tank for reaction. Under the stirring speed of 500 rpm, quickly adjust the pH value to 10.8, adjust the flow rate of the NaOH solution to keep the pH value of the synthesis system stable at 10.8, adjust the flow rate of the NH₃·H₂O solution to maintain the NH₃·H₂O concentration in the synthesis system at 6.0 g / L, and adjust the flow rate of N₂ under the liquid level in the reactor atmosphere to 400 L / h and the flow rate of air under the liquid level to 400 L / h.

[0166] After starting the reaction for 1 h, adjust the flow rate of the mixed metal sulfate solution, and slowly increase it to 417 mL / min in 6 h. Synchronously adjust the flow rates of the NaOH solution and the NH₃·H₂O solution to keep the pH value stable at 10.8 and the ammonia value at 6.0; after starting the reaction for 4 h, adjust the flow rate of N₂ under the liquid level in the reactor atmosphere to 180 L / h and the flow rate of air under the liquid level to 400 L / h, and increase the oxygen content in the reaction atmosphere by 1% every 4 h. Gradually reduce the stirring speed according to the particle size D50 of the material. When D50 reaches 8 μm, the stirring speed is reduced and maintained at 200 rpm. When D50 reaches 13.5 - 13.6 μm, stop the reaction to obtain a porous, puffy large-particle ternary precursor slurry.

[0167] Step 5: Discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0168] Step 6: Wash the ternary precursor slurry alternately with alkali and pure water.

[0169] Step 7: Uniformly distribute the ternary precursor slurry in the drying device for drying. The drying temperature is 120 °C, the drying time is 12 h, and the number of meshes of the sieve is 325 - mesh double layer.

[0170] Through the above steps, a positive electrode material precursor can be obtained as Figures 9 to 14 shown, with high agglomeration, a porous puffy morphology, and an average particle size of 10 - 20 μm.

[0171] Example 3

[0172] This embodiment provides a method for preparing a cathode material precursor, comprising the following steps:

[0173] Step 1: Select nickel soluble sulfate, cobalt soluble sulfate, and manganese soluble sulfate in a molar ratio of 96:2:2, mix them with deionized water, and prepare a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0174] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0175] Prepare an NH₃·H₂O solution with a concentration of 6 mol / L.

[0176] Maintain the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution at a constant temperature of 25 °C.

[0177] Step 2: Open the jacket of a 180 L reactor, and let water in and out.

[0178] Step 3: Add 100 L of hot pure water into a 200 L reactor, control the reactor temperature at 60 °C, and the stirring speed at 500 rpm. Then pump the NaOH solution and the NH₃·H₂O solution into the reactor. The concentration of the NH₃·H₂O solution is maintained at 6.0 g / L before adding alkali, and the initial pH at 45 °C is 11.60 to prepare the reaction bottom liquid of the reactor.

[0179] After the reaction starts, set the flow rates of the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution to 0 mL / min, 20 mL / min, and 133 mL / min respectively, and continuously pump them into the 60 °C constant temperature reactor through the feeding tank for reaction. Under a stirring speed of 500 rpm, quickly adjust the pH value to 11.3, and adjust the flow rate of the NaOH solution to make the pH value of the synthesis system stable at 11.3. Adjust the flow rate of the NH₃·H₂O solution to maintain the NH₃·H₂O concentration in the synthesis system at 9.0 g / L. Adjust the N₂ flow rate under the liquid in the reactor atmosphere to 700 L / h and the air flow rate under the liquid to 700 L / h.

[0180] After 1 h of starting the reaction, adjust the flow rate of the mixed metal sulfate solution, and slowly increase it to 417 mL / min in 6 h. Synchronously adjust the flow rates of the NaOH solution and the NH₃·H₂O solution to stabilize the pH value at 11.3 and the ammonia value at 9.0. After 4 h of starting the reaction, adjust the sub-liquid N₂ flow rate in the reaction kettle atmosphere to 250 L / h and the sub-liquid air flow rate to 750 L / h. The oxygen content in the reaction atmosphere is increased by 1% every 4 h. Steplessly reduce the stirring speed according to the particle size D50 of the material. When D50 reaches 8 μm, the stirring speed is reduced and maintained at 200 rpm. When D50 reaches 13.5 - 13.6 μm, stop the reaction to obtain a porous, puffy large-particle ternary precursor slurry.

[0181] Step 5: Discharge the ternary precursor slurry that meets the particle size requirements into a transfer tank and stir it.

[0182] Step 6: Wash the ternary precursor slurry alternately with alkali and pure water.

[0183] Step 7: Uniformly distribute the ternary precursor slurry in a drying device for drying. The drying temperature is 120 °C, the drying time is 12 h, and the number of meshes of the sieve is 325 - mesh double - layer.

[0184] Through the above steps, a cathode material precursor can be obtained as Figures 15 to 20 shown, with high agglomeration, a porous puffy morphology, and an average particle size of 10 - 20 μm.

[0185] Comparative Example 1

[0186] This comparative example provides a method for preparing a cathode material precursor, including the following steps:

[0187] Step 1: Select Ni soluble sulfate, Co soluble sulfate, and Mn soluble sulfate according to a molar ratio of 88:6:6, and mix them with deionized water to prepare a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0188] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0189] Prepare an NH₃·H₂O solution with a concentration of 6 mol / L.

[0190] Maintain the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution at a constant temperature of 25 °C.

[0191] Step 2: Open the jacket of a reaction kettle with a volume of 180 L, and let water in and out.

[0192] Step 3: Add 100 L of hot pure water into a reactor with a volume of 200 L. Control the temperature of the reactor at 60 °C and the stirring speed at 500 rpm. Then pump the NaOH solution and the NH₃·H₂O solution into the reactor. The concentration of the NH₃·H₂O solution is maintained at 6.0 g / L before adding the alkali, and the initial pH at 45 °C is 11.60 to prepare the reaction bottom liquid of the reactor.

[0193] Step 4: After starting the reaction, set the flow rates of the NaOH solution, the NH₃·H₂O solution, and the mixed metal sulfate solution to 0 mL / min, 20 mL / min, and 133 mL / min respectively, and continuously pump them into a 60 °C constant-temperature reactor through the feeding tank for reaction. Under a stirring speed of 500 rpm, quickly adjust the pH value to 10.2, adjust the flow rate of the NaOH solution to keep the pH value of the synthesis system stable at 10.2, adjust the flow rate of the NH₃·H₂O solution to maintain the NH₃·H₂O concentration in the synthesis system at 4.0 g / L, and adjust the N₂ flow rate under the liquid level in the reactor atmosphere to 150 L / h.

[0194] After starting the reaction for 1 h, adjust the flow rate of the mixed metal sulfate solution, and slowly increase it to 417 mL / min in 6 h. Synchronously adjust the flow rates of the NaOH solution and the NH₃·H₂O solution to keep the pH value stable at 10.2, and the ammonia value at 3.0; maintain the N₂ flow rate under the liquid level in the reactor atmosphere at 150 L / h; reduce the stirring speed step by step according to the particle size D50 of the material. When D50 reaches 8 μm, the stirring speed is reduced and maintained at 200 rpm. When D50 reaches 13.5 - 13.6 μm, stop the reaction to obtain a ternary precursor slurry with an average particle size of 10 - 20 μm.

[0195] Step 5: Discharge the ternary precursor slurry that meets the particle size requirements into a transfer tank and stir it.

[0196] Step 6: Wash the ternary precursor slurry alternately with alkali washing and pure water washing.

[0197] Step 7: Uniformly distribute the ternary precursor slurry in a drying device for drying. The drying temperature is 120 °C, the drying time is 12 h, and the number of meshes of the sieve is 325 - mesh double - layer.

[0198] Through the above steps, a large - particle cathode material precursor with a dense surface morphology as shown in Figures 21 to 26 can be obtained.

[0199] Comparative Example 2

[0200] This comparative example provides a method for preparing a cathode material precursor, including the following steps:

[0201] Step 1: Select nickel soluble sulfate, cobalt soluble sulfate, and manganese soluble sulfate according to a molar ratio of 88:4:8, and mix them with deionized water to prepare a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0202] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0203] Prepare an NH₃·H₂O solution with a concentration of 6 mol / L.

[0204] Maintain the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution at a constant temperature of 25 °C.

[0205] Step 2: Open the jacket of the reactor with a volume of 180 L, and let water in and out.

[0206] Step 3: Add 100 L of hot pure water into the reactor with a volume of 200 L, control the reactor temperature at 60 °C, and the stirring speed at 500 rpm. Then pump the NaOH solution and NH₃·H₂O solution into the reactor. The concentration of the NH₃·H₂O solution is maintained at 6.0 g / L before adding alkali, and the initial pH at 45 °C is 11.60 to prepare the reaction bottom liquid of the reactor.

[0207] After starting the reaction, set the flow rates of the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution to 0 mL / min, 20 mL / min, and 133 mL / min respectively, and continuously pump them into the 60 °C constant temperature reactor through the feeding tank for reaction. Under the stirring speed of 500 rpm, quickly adjust the pH value to 10.8, adjust the flow rate of the NaOH solution to make the pH value of the synthesis system stable at 10.8, adjust the flow rate of the NH₃·H₂O solution to maintain the NH₃·H₂O concentration in the synthesis system at 6.0 g / L, and adjust the N₂ flow rate in the gas-liquid phase of the reactor to 400 L / h.

[0208] After starting the reaction for 1 h, adjust the flow rate of the mixed metal sulfate solution, and slowly increase it to 417 mL / min in 6 h. Synchronously adjust the flow rates of the NaOH solution and NH₃·H₂O solution to keep the pH value stable at 10.8 and the ammonia value at 6.0; maintain the N₂ flow rate in the gas-liquid phase of the reactor at 400 L / h; reduce the stirring speed step by step according to the particle size D50 of the material. When D50 reaches 8 μm, the stirring speed is reduced and maintained at 200 rpm. When D50 reaches 13.5 - 13.6 μm, stop the reaction to obtain a ternary precursor slurry with an average particle size of 10 - 20 μm.

[0209] Step 5: Discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0210] Step 6: Alternately wash the ternary precursor slurry with alkali solution and pure water.

[0211] Step 7: Uniformly distribute the ternary precursor slurry in a drying device for drying. The drying temperature is 120 °C, the drying time is 12 h, and the number of meshes of the sieve is 325 - mesh double - layer.

[0212] Through the above steps, a large - particle cathode material precursor with a dense surface morphology as Figures 27 to 32 shown can be obtained.

[0213] Comparative Example 3

[0214] This comparative example provides a method for preparing a cathode material precursor, which includes the following steps:

[0215] Step 1: Select nickel soluble sulfate, cobalt soluble sulfate, and manganese soluble sulfate according to a molar ratio of 96:2:2, and mix them with deionized water to prepare a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0216] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0217] Prepare an NH₃·H₂O solution with a concentration of 6 mol / L.

[0218] Maintain the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution at a constant temperature of 25 °C.

[0219] Step 2: Open the jacket of a reaction kettle with a volume of 180 L, and let water in and out.

[0220] Step 3: Add 100 L of hot pure water into a reaction kettle with a volume of 200 L, control the temperature of the reaction kettle at 60 °C, and the stirring speed at 500 rpm. Then pump the NaOH solution and the NH₃·H₂O solution into the reaction kettle. The concentration of the NH₃·H₂O solution is maintained at 6.0 g / L before adding alkali, and the initial pH at 45 °C is 11.60 to prepare the reaction bottom liquid of the reaction kettle.

[0221] Step 4: After starting the reaction, set the flow rates of the NaOH solution, NH₃·H₂O solution, and mixed metal sulfate solution to 0 mL / min, 20 mL / min, and 133 mL / min respectively, and continuously pump them into a 60 - °C constant - temperature reaction kettle through a feeding tank for reaction. Under a stirring speed of 500 rpm, quickly adjust the pH value to 11.3, adjust the flow rate of the NaOH solution to keep the pH value of the synthesis system stable at 11.3, adjust the flow rate of the NH₃·H₂O solution to keep the NH₃·H₂O concentration in the synthesis system at 9.0 g / L, and adjust the N₂ flow rate in the gas - liquid phase of the reaction kettle to 700 L / h.

[0222] After 1 h of the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted, and it was slowly increased to 417 mL / min in 6 h. Meanwhile, the flow rates of the NaOH solution and the NH₃·H₂O solution were adjusted to stabilize the pH value at 11.3 and the ammonia value at 9.0. The flow rate of N₂ under the liquid level in the reaction kettle atmosphere was maintained at 700 L / h. The stirring speed was decreased step by step according to the particle size D50 of the materials. When D50 reached 8 μm, the stirring speed was decreased and maintained at 200 rpm. When D50 reached 13.5 - 13.6 μm, the reaction was stopped to obtain a ternary precursor slurry with an average particle size of 10 - 20 μm.

[0223] Step 5: Discharge the ternary precursor slurry that meets the particle size requirements into a transfer tank and stir it.

[0224] Step 6: Wash the ternary precursor slurry alternately with alkali washing and pure water.

[0225] Step 7: Uniformly distribute the ternary precursor slurry in a drying device for drying. The drying temperature was 120 °C, the drying time was 12 h, and the number of mesh of the sieve was 325 - mesh double - layer.

[0226] Through the above steps, a large - particle cathode material precursor with a dense surface morphology as shown in Figures 33 to 38 can be obtained.

[0227] The Ni content, Co content, Mn content, sodium (Na) content, sulfur (S) content, specific surface area test (BET), and thermal desorption test (TD) were respectively carried out on the cathode material precursors prepared in Examples 1 - 3 and Comparative Examples 1 - 3 of the present application. The results are shown in Table 1 below.

[0228] Table 1

[0229]

[0230] As can be seen from Table 1, the main content results of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 are similar. The specific surface areas of Examples 1 - 3 are larger, the sodium contents are lower, the sulfur contents are lower, and the thermal desorptions are smaller than those in Comparative Examples 1 - 3 respectively.

[0231] From Figures 3 to 38 the electron microscope images, it can be seen that under the oxidation conditions, the surface whiskers of the particles in Examples 1 - 3 are thinner and more porous. During the washing process, impurities such as sodium and sulfur are more easily removed. Moreover, due to the porous surface whiskers of the particles in Examples 1 - 3, the strength of the precursor is reduced, the particles are more easily broken, the cathode sintering difficulty is reduced, and the sintering is more complete.

[0232] It should be noted that Figure 5 the dark color in

[0233] Only the content related to the inventive points is introduced here. The rest can be obtained by referring to the related art and will not be elaborated here.

[0234] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A precursor of a cathode material, characterized in that, It includes precursor particles, which are formed by agglomeration of a plurality of first particles. The first particles have a core-shell structure, and the core-shell structure has a core and a surface layer. The core has dense seeds. The surface layer has a plurality of whiskers, and there are pores between adjacent whiskers.

2. The precursor of the cathode material according to claim 1, wherein The ratio of the particle size of the seeds to the particle size of the first particles ranges from 30% to 40%. And / or The ratio of the particle size of the first particles to the particle size of the precursor particles ranges from 20% to 50%.

3. The precursor of the cathode material according to claim 1, characterized in that, The thickness of the whiskers ranges from 10 nm to 30 nm. And / or The specific surface area of the precursor particles ranges from 20 to 40 m 2 / g.

4. The precursor of the cathode material according to claim 2 or 3, characterized in that, The precursor particles further include a shell layer, which coats the surface layer of the core-shell structure. The thickness of the shell layer ranges from 0.2 μm to 0.5 μm. And / or The thickness of the core of the core-shell structure ranges from 4 μm to 8 μm.

5. A cathode material, characterized in that, It includes the precursor of the cathode material as described in any one of claims 1-4.

6. A method for preparing a precursor of a cathode material, characterized in that, It is made by the following steps: Mix a variety of metal ion sources with water to obtain a mixed metal ion solution; and separately prepare a first lye and a complexing agent. After adding water and introducing a protective gas into the reactor, add the first lye and the complexing agent to form a reaction bottom liquid. Add the first lye, the complexing agent and the mixed metal ion solution into the reactor in a co-current manner for nucleation reaction, and control the reaction atmosphere to be the first atmosphere to form seeds; when it is detected that the seed content reaches the required target, reduce the pH value of the reaction solution, and control the reaction atmosphere to be the second atmosphere to maintain the growth reaction of the seed particles. Continue feeding. When it is detected that the liquid level in the reactor reaches the filtration requirement, filter it and maintain the liquid level in the reactor stable. And when it is detected that the particle size of the material in the reactor reaches the required target, stop feeding and discharge the material to a container. Perform solid-liquid separation on the material in the container, and after treating the separated filter cake, obtain the precursor of the cathode material.

7. The method for preparing the precursor of the cathode material according to claim 6, wherein The first atmosphere at least includes the protective gas, and the second atmosphere includes air and the protective gas. In the second atmosphere, the air flow rate gradually increases as the solid content of the material increases.

8. The method for preparing the precursor of the cathode material according to claim 7, wherein The air flow rate range of the first atmosphere is 0-800 L / h, and the protective gas flow rate range of the first atmosphere is 100-800 L / h. And / or The air flow rate range of the second atmosphere is 300-800 L / h, and the protective gas flow rate range of the second atmosphere is 0-300 L / h.

9. The method for preparing the precursor of the cathode material according to claim 8, wherein The concentration range of the complexing agent in the nucleation reaction is 2.0-10.0 g / L. And / or The concentration range of the complexing agent in the growth reaction is 1.0-10.0 g / L.

10. The method for preparing the precursor of the cathode material according to claim 8, wherein The flow rate range of the mixed metal ion solution is 0.5-40 L / h. And / or The flow rate ratio range of the first lye, the complexing agent and the mixed metal ion solution is 0-9:3-20:20-133. And / or The pH value range of the reaction solution is 10.0-11.5.

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