Positive electrode material precursor as well as preparation method therefor and use thereof

Abstract

Disclosed in the present application are a positive electrode material precursor as well as a preparation method therefor and the use thereof, which relate to the technical field of lithium ion battery positive electrode materials. The positive electrode material precursor of the present application comprises precursor particles, the precursor particles being formed by agglomeration of a plurality of first particles, the first particles being of a core-shell structure, the core-shell structure being provided with an inner core and a shell layer, the inner core being provided with a compact seed crystal, the shell layer being provided with a plurality of whiskers, and pores being formed between the adjacent whiskers. Accordingly, the present application forms the large-particle precursor which is highly agglomerated and porous and which has puff-like porous surface morphology, and facilitates industrial production.

Description

Positive electrode material precursor and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311871460.7 and invention name “Positive electrode material precursor, preparation method and application thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of battery materials, and in particular to a positive electrode material precursor and a preparation method and application thereof. Background Art

[0003] With the increase in sales of new energy vehicles and the steady 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) depends largely 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 crystalization. The use of single crystal materials can reduce grain boundaries, reduce the occurrence of side reactions, and increase compaction density, thereby increasing energy density and extending the cycle life of batteries.

[0004] However, the preparation process of single crystal materials is complicated. Compared with the preparation of polycrystalline materials, the preparation of single crystal materials requires a higher sintering temperature, and high temperature can easily cause the mixing of nickel and lithium. At the same time, during the sintering process, the primary particles will grow and the secondary particles will adhere. Therefore, grinding is required after sintering. If the sintering is insufficient and a quasi-single crystal is formed, the material will not achieve the expected effect. In addition, the current single crystal materials are mainly obtained by sintering small particle precursors. Traditional small particle precursors are prone to multi-level agglomeration and poor particle uniformity during the reaction, resulting in high sintering temperatures required for the sintering process, insufficient sintering, increased sintering difficulty, and high temperature processes that easily cause the mixing of nickel and lithium, which in turn causes the performance of the positive electrode material to fail to achieve the expected effect.

[0005] Therefore, there is an urgent need to provide a positive electrode material precursor and a preparation method and application thereof to solve the above problems.

[0006] Application Contents

[0007] One of the purposes of the embodiments of the present application is to provide a positive electrode material precursor and its preparation method and application, to obtain a large-particle precursor with high agglomeration, porosity, loose surface morphology and puff-shaped. The large-particle precursor is formed by the agglomeration and growth of small particles. The small particles have more pores on the surface, which is conducive to the lithium element entering the interior of the particles during the sintering process and making the sintering more complete, 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 breakage can be relatively more uniform.

[0008] The technical solution adopted in the embodiment of this application is:

[0009] In a first aspect, a cathode material precursor is provided, the cathode material precursor comprising precursor particles, the precursor particles being formed by agglomerating a plurality of first particles, the first particles being a core-shell structure having a core and a surface layer;

[0010] The inner core has dense seed crystals;

[0011] The surface layer has a plurality of whiskers, and there are pores between adjacent whiskers.

[0012] In some embodiments, the ratio of the particle size of the seed crystal to the particle size of the first particles is in the range of 30%-40%.

[0013] In some embodiments, the ratio of the particle size of the first particles to the particle size of the precursor particles is in a range of 20%-50%.

[0014] In some embodiments, the whiskers have a thickness ranging from 10 nm to 30 nm.

[0015] In some embodiments, the specific surface area of ​​the precursor particles ranges from 20 m 2 / g-40m 2 / g.

[0016] In some embodiments, each of the precursor particles further includes a shell layer, and the shell layer covers the surface layer of the core-shell structure.

[0017] In some embodiments, the shell layer has a thickness ranging from 0.2 μm to 0.5 μm.

[0018] In some embodiments, the core thickness of the core-shell structure is in the range of 4 μm to 8 μm.

[0019] In a second aspect of the present application, a method for preparing a positive electrode material precursor is provided, which is prepared by the following steps:

[0020] Mixing a plurality of metal ion sources with water to obtain a mixed metal ion solution; and separately preparing a first alkali solution and a complexing agent;

[0021] After adding water into the reactor and introducing protective gas, the first alkali solution and the complexing agent are added to form a reaction base solution;

[0022] The first alkaline solution, the complexing agent, and the mixed metal ion solution are added to the reactor in parallel to perform a nucleation reaction, and the reaction atmosphere is controlled to be a first atmosphere to form seed crystals; when it is detected that the seed crystal content reaches the target, the pH of the reaction solution is reduced, and the reaction atmosphere is controlled to be a second atmosphere to maintain the growth reaction of the seed crystal particles;

[0023] Continuously feeding, filtering when it is detected that the liquid level in the reactor reaches the filtering requirement, and maintaining the liquid level in the reactor stable; and, when it is detected that the particle size of the material in the reactor reaches the target, stopping feeding and discharging the material into a container;

[0024] The material in the container is subjected to solid-liquid separation, and the separated filter cake is processed to obtain the positive electrode material precursor.

[0025] In some embodiments, the first atmosphere includes at least the protective gas, and the second atmosphere includes air and the protective gas.

[0026] In some embodiments, in the second atmosphere, the air flow rate gradually increases with the increase of the solid content of the material.

[0027] In some embodiments, the air flow rate of the first atmosphere ranges from 0 L / h to 800 L / h, and the protective gas flow rate of the first atmosphere ranges from 100 L / h to 800 L / h.

[0028] In some embodiments, the air flow rate of the second atmosphere ranges from 300 L / h to 800 L / h, and the protective gas flow rate of the second atmosphere ranges from 0 L / h to 300 L / h.

[0029] In some embodiments, the concentration of the complexing agent for the nucleation reaction ranges from 2.0 g / L to 10.0 g / L.

[0030] In some embodiments, the concentration of the complexing agent in the growth reaction ranges from 1.0 g / L to 10.0 g / L.

[0031] In some embodiments, the flow rate of the mixed metal ion solution ranges from 0.5 L / h to 40 L / h.

[0032] In some embodiments, the flow ratio of the first alkali solution, the complexing agent, and the mixed metal ion solution ranges from 0-9:3-20:20-133.

[0033] In some embodiments, the pH of the reaction solution is in the range of 10.0-11.5.

[0034] In a third aspect of the present application, a positive electrode material is provided, comprising the positive electrode material precursor described above.

[0035] In a fourth aspect of the present application, a secondary battery is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet contains the above-mentioned positive electrode material.

[0036] The cathode material precursor provided by the present application is formed by the aggregation and growth of small particles. The surface pores of the small particles are relatively large, which is conducive to the lithium element entering the interior of the particles during the sintering process and making the sintering more complete, 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 breakage can be relatively more uniform. Thus, a large-particle cathode material precursor with high agglomeration, porosity, and loose puff-shaped surface morphology can be obtained, and the cathode material precursor has an ultra-large specific surface area, large internal porosity, and low tap density. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] FIG1 is a flow chart of a process for preparing a cathode material precursor according to an embodiment of the present application;

[0039] FIG2 is a schematic structural diagram of a main reactor, a concentrator, a filter rod, a filter pump, and a filter provided in an embodiment of the present application;

[0040] Figures 3 to 8 are electron microscope images of a cathode material precursor provided in Example 1 of the present application at different magnifications;

[0041] Figures 9 to 14 are electron microscope images of a cathode material precursor provided in Example 2 of the present application at different magnifications;

[0042] Figures 15 to 20 are electron microscope images of a cathode material precursor provided in Example 3 of the present application at different magnifications;

[0043] Figures 21 to 26 are electron microscope images of a cathode material precursor provided in Comparative Example 1 of the present application at different magnifications;

[0044] Figures 27 to 32 are electron microscope images of a cathode material precursor provided in Comparative Example 2 of the present application at different magnifications;

[0045] Figures 33 to 38 are electron microscope images of a positive electrode material precursor provided in Comparative Example 3 of the present application at different magnifications. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit this application.

[0047] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0048] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c" or "at least one of a, b and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc or abc, where a, b, c can be single or multiple.

[0049] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. Some or all 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 on the implementation process of the embodiments of the present application.

[0050] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0051] The terms "first," "second," etc., are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the number of technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first," "second," etc., may explicitly or implicitly include one or more of such features.

[0052] In order to illustrate the technical solution described in this application, the following is a detailed description with reference to specific drawings and embodiments.

[0053] In the first aspect, an embodiment of the present application provides a positive electrode material precursor, which includes precursor particles, which are formed by agglomeration of multiple first particles, and the first particles are a core-shell structure, the core-shell structure has an inner core and a surface layer, the inner core has dense crystal seeds, the surface layer has multiple whiskers, and there are pores between adjacent whiskers.

[0054] The embodiment of the present application provides a positive electrode material precursor, in which the precursor particles are formed by the agglomeration and growth of small particles, and the surface pores of the small particles are relatively large, which is conducive to the lithium element entering the interior of the particles during the sintering process and making the sintering more complete, 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 breakage can be relatively more uniform. Thus, a large-particle positive electrode material precursor with high agglomeration, porosity, and loose puff-shaped surface morphology can be obtained, and the positive electrode material precursor has the characteristics of ultra-large specific surface area, large internal porosity, and low tap density, so that a single crystal material with a higher compaction density can be obtained, and the energy density is improved, so that the battery cycle life is higher.

[0055] The positive electrode material precursor in the embodiment of the present application is applicable to products such as binary positive electrode material precursor and ternary positive electrode material precursor.

[0056] In some embodiments, the ratio of the seed particle size to the first particle size ranges from 30% to 40%. The ratio of the seed particle size to the first particle size is not specifically limited. For example, the ratio of the seed particle size to the first particle size can be 30%, 35%, or 40%.

[0057] In some embodiments, the ratio of the particle size of the first particles of the plurality of agglomerated particles to the particle size of the precursor particles ranges from 20% to 50%. The ratio of the particle size of the first particles of the plurality of agglomerated particles to the particle size of the precursor particles is not specifically limited. For example, the ratio of the particle size of the first particles of the plurality of agglomerated particles to the particle size of the precursor particles can be 20%, 40%, or 50%.

[0058] In some embodiments, the precursor particles of the embodiments of the present application are formed by the agglomeration and growth of small particles. There are relatively dense crystal seeds inside the agglomerated small particles, which are relatively easier to break after sintering, and the breakage can be relatively more uniform.

[0059] In some embodiments, the molecular formula of the positive electrode material precursor 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。

[0060] In some embodiments, the core thickness of the core-shell structure may range from 4 μm to 8 μm. For example, the core of the core-shell structure may be 4 μm, 5 μm, 6 μm, 7 μm or 8 μm.

[0061] In some embodiments, the small particles of the embodiments of the present application have more surface pores, which is beneficial for lithium elements to enter the interior of the particles during the sintering process, making the sintering more complete, thereby reducing the generation of quasi-single crystal particles and reducing the sintering difficulty of the precursor.

[0062] In some embodiments, the whisker thickness ranges from 10 nm to 30 nm. There is no specific limitation on the whisker thickness, and for example, the whisker thickness can be 10 nm, 20 nm, or 30 nm.

[0063] In some embodiments, the specific surface area of ​​the precursor particles ranges from 20 m 2 / g-40m 2 / g. There is no specific limitation on the specific surface area of ​​the precursor particles. For example, the specific surface area of ​​the precursor particles can be 20m 2 / g、30m 2 / g or 40m 2 / g, etc.

[0064] An embodiment of the present application provides a positive electrode material precursor, in which the whiskers on the surface of the small particles are relatively thin and have a porous puff-like morphology. The thin whiskers and large specific surface area reduce the strength of the particles, thereby reducing the difficulty of sintering, thereby enabling more complete sintering; and since the strength of the particles is reduced, the difficulty of crushing after sintering is reduced, making the particles easy to crush.

[0065] In some embodiments, the precursor particles further include a shell layer that covers the surface layer of the core-shell structure; the shell layer thickness ranges from 0.2 μm to 0.5 μm. The shell layer thickness is not specifically limited, and illustratively, the shell layer thickness can be 0.2 μm, 0.3 μm, or 0.5 μm.

[0066] In some embodiments, the core thickness of the core-shell structure ranges from 4 μm to 8 μm. For example, the core thickness can be 4 μm, 5 μm, 6 μm, 7 μm, or 9 μm.

[0067] An embodiment of the present application provides a positive electrode material precursor, which can provide surface strength of large precursor particles through the shell layer outside the surface layer, thereby preventing the positive electrode material precursor particles from being broken due to equipment reasons during washing, drying and other processes, thereby improving the success rate of preparing positive electrode material precursor particles; and, because the shell layer is relatively thin, it has less impact on normal material sintering and performance.

[0068] In a second aspect, an embodiment of the present application provides a method for preparing a cathode material precursor, comprising the following steps:

[0069] Mixing a plurality of metal ion sources with water to obtain a mixed metal ion solution; and separately preparing a first alkali solution and a complexing agent;

[0070] After adding water into the reactor and introducing protective gas, the first alkali solution and the complexing agent are added to form a reaction base solution;

[0071] The first alkaline solution, the complexing agent, and the mixed metal ion solution are added to the reactor in parallel to perform a nucleation reaction, and the reaction atmosphere is controlled to be a first atmosphere to form seed crystals; when it is detected that the seed crystal content reaches the target, the pH of the reaction solution is reduced, and the reaction atmosphere is controlled to be a second atmosphere to maintain the growth reaction of the seed crystal particles;

[0072] Continuously feeding, filtering when it is detected that the liquid level in the reactor reaches the filtering requirement, and maintaining the liquid level in the reactor stable; and stopping feeding when it is detected that the particle size of the material in the reactor reaches the target, and discharging the material into a container;

[0073] The material in the container is subjected to solid-liquid separation, and the separated filter cake is processed to obtain the positive electrode material precursor.

[0074] An embodiment of the present application provides a method for preparing a positive electrode material precursor. By adopting an intermittent process, controlling the amount of nitrogen and air introduced during the growth reaction stage, and combining the stirring speed during the reaction process, a large-particle positive electrode material precursor with high agglomeration, porosity, and loose puff-shaped surface morphology is formed.

[0075] In some embodiments, the cathode material precursor is a ternary cathode precursor material, and the preparation method includes the following specific steps:

[0076] Step 1: According to the molar ratio of nickel (Ni), cobalt (Co) and manganese (Mn) elements required for the positive electrode material precursor, Ni soluble salt, Co soluble salt and Mn soluble salt are selected according to the molar ratio, and then mixed with pure water to prepare a mixed metal ion solution with a first concentration; and, respectively, prepare a first alkali solution with a second concentration and a complexing agent with a third concentration.

[0077] In some embodiments, the mixed metal ion solution includes but is not limited to Ni soluble salt, Co soluble salt and Mn soluble salt, and can also be alkali solution or other sources, depending on the actual application.

[0078] In some embodiments, the molar ratio of the Ni soluble salt, the Co soluble salt, and the Mn soluble salt in step 1 may range from (88-96):(2-8):(2-8). For example, the molar ratio of the Ni soluble salt, the Co soluble salt, and the Mn soluble salt may be 88:6:6, 88:4:8, 96:2:2, etc.

[0079] In some embodiments, the pure water in step 1 can be deionized water. In some embodiments, the deionized water can be hot water.

[0080] In some embodiments, the first concentration in step 1 may be in the range of 1.2-2.7 mol / L. For example, the first concentration may be 1.2 mol / L, 1.8 mol / L, 2.3 mol / L, or 2.7 mol / L.

[0081] In some embodiments, the first alkali solution in step 1 is not particularly limited. For example, the first alkali solution can be a sodium hydroxide (NaOH) solution.

[0082] In some embodiments, the second concentration of the first alkali solution in step 1 may range from 1.0 to 13.0 mol / L. For example, the second concentration may be 1.0 mol / L, 3.0 mol / L, 10.5 mol / L, or 13.0 mol / L.

[0083] In some embodiments, the complexing agent in step 1 is not particularly limited. For example, the complexing agent can be ammonia water (NH 3 ·H 2 O) or the like.

[0084] In some embodiments, the third concentration of the complexing agent in step 1 may be in the range of 1.0-12.0 mol / L. For example, the third concentration may be 1.0 mol / L, 3.0 mol / L, 6.0 mol / L, or 12 mol / L.

[0085] It should be noted that, for the preparation of the mixed metal ion solution having the first concentration in step 1, and the order of preparing the first alkali solution having the second concentration and the complexing agent having the third concentration, respectively, there is no specific limitation. For example, the mixed metal ion solution having the first concentration can be prepared first, and then the first alkali solution having the second concentration and the complexing agent having the third concentration can be prepared respectively; or, the first alkali solution having the second concentration and the complexing agent having the third concentration can be prepared respectively first, and then the mixed metal ion solution having the first concentration can be prepared; or, the mixed metal ion solution having the first concentration, the first alkali solution having the second concentration, and the complexing agent having the third concentration can be prepared at the same time.

[0086] Step 2: Adding water to and returning water to the reactor. Specifically, after adding water and introducing protective gas into the reactor, the first alkali solution and the complexing agent are added to form a reaction bottom solution.

[0087] In some embodiments, the type of reactor in step 2 is not particularly limited. For example, the reactor can be a reactor, etc.

[0088] In some embodiments, the above step 2, introducing water into and returning water to the reactor may include: opening the jacket of the reactor, introducing water into and returning water to the reactor.

[0089] In some embodiments, after adding a first amount of pure water into the reactor and introducing a protective gas, a first alkali solution and a complexing agent are added at a first temperature and a first stirring speed to form a reaction base liquid.

[0090] In some embodiments, the first amount of pure water may range from 40 to 200 L. In some embodiments, the first amount may range from 50 to 160 L. For example, the first amount may be 50 L, 100 L, or 160 L.

[0091] In some embodiments, the protective gas is not particularly limited, and illustratively, the protective gas may include nitrogen (N2), etc. The following embodiments are all described with N2 as the protective gas.

[0092] In some embodiments, the pH value of the reaction base solution may range from 11.0 to 12.5 (at 45° C.). In some embodiments, the pH value of the reaction base solution may range from 11.5 to 12.3 (at 45° C.). For example, the pH value of the reaction base solution may be 11.5 (at 45° C.), 12.0 (at 45° C.), or 12.3 (at 45° C.).

[0093] In some embodiments, the complexing agent concentration ranges from 2.0 g / L to 10.0 g / L. In some embodiments, the complexing agent concentration ranges from 4.0 to 9.0 g / L. For example, the complexing agent concentration can be 4.0 g / L, 6.0 g / L, or 9.0 g / L.

[0094] In some embodiments, the first temperature may be in the range of 50-70° C. For example, the first temperature may be 50° C., 60° C., or 70° C.

[0095] In some embodiments, the first stirring speed may be in the range of 400-600 rpm. For example, the first stirring speed may be 400 rpm, 500 rpm, or 600 rpm.

[0096] Step 3, at a second stirring speed, adding the first alkali solution, the complexing agent and the mixed metal ion solution into the reactor in a first flow ratio and flowing in parallel to carry out a nucleation reaction, and controlling the reaction temperature to the first temperature, the reaction atmosphere to the first atmosphere, the pH of the reaction liquid to the first pH and the concentration of the complexing agent to the fourth concentration to form seed crystals; when it is detected that the seed crystal content reaches the target, lowering the first pH, and controlling the reaction temperature to the second temperature, the reaction atmosphere to the second atmosphere, the pH of the reaction liquid to the second pH and the concentration of the complexing agent to the fifth concentration to maintain the growth reaction of the seed crystal particles in the reactor.

[0097] In some embodiments, the first atmosphere in step 3 above includes at least a protective gas, and the second atmosphere includes a protective gas and air.

[0098] In some embodiments, the amount of the mixed metal ion solution added in step 3 may range from 0.5 L / h to 40 L / h. In some embodiments, the amount of the mixed metal ion solution added may range from 1 to 30 L / h. For example, the amount of the mixed metal ion solution added may be 1 L / h, 10 L / h, 20 L / h, or 30 L / h, etc.

[0099] In some embodiments, the second stirring speed in step 3 may range from 50 to 600 rpm. In some embodiments, the second stirring speed may range from 100 to 550 rpm. For example, the second stirring speed may be 100 rpm, 200 rpm, 300 rpm, 400 rpm, or 550 rpm.

[0100] In some embodiments, the first temperature in step 3 may range from 40.0 to 75.0° C. In some embodiments, the first temperature may range from 45.0 to 65.0° C. For example, the first temperature may be 45.0° C., 55.0° C., or 65.0° C.

[0101] In some embodiments, the pH value of the reaction solution of the nucleation reaction in step 3 may range from 11.0 to 12.5 (at 45° C.). In some embodiments, the pH value of the reaction solution of the nucleation reaction may range from 11.5 to 12.3 (at 45° C.). For example, the pH value of the reaction solution of the nucleation reaction may be 11.5 (at 45° C.), 12.0 (at 45° C.), or 12.3 (at 45° C.).

[0102] In some embodiments, the concentration of the complexing agent in the nucleation reaction in step 3 may range from 2.0 g / L to 10.0 g / L. In some embodiments, the concentration of the complexing agent in the nucleation reaction may range from 4.0 to 9.0 g / L. For example, the concentration of the complexing agent in the nucleation reaction may be 4.0 g / L, 6.0 g / L, 7.0 g / L, or 9.0 g / L.

[0103] In some embodiments, the first atmosphere in step 3 is not specifically limited. For example, the first atmosphere may include N2; or, the first atmosphere may include N2 and air, etc., wherein the air mainly refers to oxygen (O2).

[0104] In some embodiments, the first atmosphere submerged nitrogen flow rate in step 3 may range from 100 L / h to 800 L / h. In some embodiments, the first atmosphere submerged nitrogen flow rate may range from 150 to 700 L / h. For example, the first atmosphere submerged nitrogen flow rate may be 150 L / h, 300 L / h, 600 L / h, or 700 L / h.

[0105] In some embodiments, the first atmosphere submerged air flow rate in step 3 may range from 0 L / h to 800 L / h. In some embodiments, the first atmosphere submerged air flow rate may range from 0 to 700 L / h. For example, the first atmosphere submerged air flow rate may be 0 L / h, 300 L / h, 600 L / h, or 700 L / h.

[0106] In some embodiments, the pH value of the reaction solution of the growth reaction in step 3 may range from 10.0 to 11.5 (at 45° C.). In some embodiments, the pH value of the reaction solution of the growth reaction may range from 10.2 to 11.3 (at 45° C.). For example, the pH value of the reaction solution of the growth reaction may be 10.2 (at 45° C.), 11.0 (at 45° C.), or 11.3 (at 45° C.).

[0107] In some embodiments, the concentration of the complexing agent in the growth reaction in step 3 may range from 1.0 g / L to 10.0 g / L. In some embodiments, the concentration of the complexing agent in the growth reaction may range from 3.0 to 9.0 g / L. For example, the concentration of the complexing agent in the growth reaction may be 3.0 g / L, 5.0 g / L, 8.0 g / L, or 9.0 g / L.

[0108] In some embodiments, the nitrogen flow rate of the second atmosphere submerged in liquid for the growth reaction in step 3 may range from 0 L / h to 300 L / h. In some embodiments, the nitrogen flow rate of the second atmosphere submerged in liquid may range from 0 to 250 L / h. For example, the nitrogen flow rate of the second atmosphere submerged in liquid may be 0 L / h, 50 L / h, 100 L / h, or 250 L / h.

[0109] In some embodiments, the second atmosphere submerged air flow rate in step 3 may range from 300 L / h to 800 L / h. In some embodiments, the second atmosphere submerged air flow rate may range from 350 L / h to 750 L / h. For example, the second atmosphere submerged air flow rate may be 350 L / h, 500 L / h, 600 L / h, or 750 L / h.

[0110] In some embodiments, step 3 can control the amount of N2 and air introduced through an intermittent process to regulate the proportion of the oxidant (air), so that the surface whiskers of the particles become thinner and the porosity of the particles increases. In this way, the oxidation amount can be increased as the synthesis time increases, so that the pores inside the particles are uniform and the morphology is porous puff-shaped. In addition, since the surface whisker strips are thinner and the particle strength is reduced, the stirring speed is reduced according to the particle size during the reaction to avoid the phenomenon of particle breakage caused by stirring. In addition, the reaction pH value, temperature, metal liquid flow, alkali flow and complexing agent flow are kept stable during the synthesis process.

[0111] In some embodiments, during the growth reaction phase in step 3, the air flow rate of the second atmosphere in the reactor is gradually increased as the solid content of the system increases. Thus, by controlling the nitrogen and oxygen content during the growth reaction phase, the growth of the seed crystal can be better achieved.

[0112] Step 4, continue feeding according to step 3. When it is detected that the liquid level in the reactor reaches the filtration requirement, start the filter to start filtration 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 target, stop feeding into the reactor, continue stirring and aging for the first time, and then discharge the material into the container.

[0113] In some embodiments, there is no specific limitation on the type of the filter. For example, the filter can be a concentrator, etc.

[0114] In some embodiments, there is no specific limitation on the type of the above-mentioned container. For example, the container can be a qualified slurry tank, a transfer tank, etc.

[0115] In some embodiments, the particle size of the material in the reactor in step 4 may range from 10 to 20 μm. For example, the particle size of the material may be 10 μm, 15 μm, or 20 μm.

[0116] In some embodiments, the value range of the first time may include 1-2 hours. For example, the first time may be 1 hour, 1.5 hours or 2 hours.

[0117] In some embodiments, in step 4, continuing to feed the material according to step 3, and when it is detected that the liquid level in the reactor reaches the filtering requirement, starting the filter to start filtering, and maintaining the liquid level in the reactor stable; when it is detected that the particle size of the material in the reactor reaches the target, stopping feeding the material to the reactor, and continuing to stir and age for the first time, discharging the material into the container may include:

[0118] Step 41, continue feeding according to step 3. When it is detected that the liquid level in the reactor reaches the filtering requirement, start the filter to start filtering, maintain the liquid level in the reactor stable, and introduce air at the same time; when it is detected that the particle size of the material in the reactor reaches the target, stop feeding into the reactor, continue stirring and aging for the first time, and then discharge the material into the container.

[0119] Therefore, by introducing air into the reactor before detecting that the particle size of the material in the reactor reaches the target, the positive electrode material precursor can form a shell layer with a certain thickness, which can improve the strength of the surface of the positive electrode material precursor, avoid the particle breakage of the positive electrode material precursor due to equipment reasons during the washing, drying and other processes, and improve the success rate of the preparation of the positive electrode material precursor.

[0120] Step 5: performing solid-liquid separation on the material in the container, washing the separated filter cake with a second alkaline solution, and then rinsing with pure water to obtain a washed filter cake.

[0121] In some embodiments, the second alkali solution in step 5 is not particularly limited. For example, the second alkali solution can be a NaOH solution, a potassium hydroxide (KOH) solution, or the like.

[0122] In some embodiments, the washed filter cake is dried, and then sieved and demagnetized in sequence to obtain a cathode material precursor.

[0123] In the related art, the preparation of polycrystalline materials sometimes considers the use of a mixture of large particles and small particles, while the preparation of single crystal materials often uses small particles to avoid the problem of uncertainty about whether the large particles are uniform after sintering, crushing and other processes. In the embodiment of the present application, a large particle precursor is formed by agglomerating small particles of a core-shell structure during the preparation of the precursor. Then, during the sintering process, lithium ions can more fully penetrate the precursor particles, and the sintering is more complete. Then, during the crushing, the large particle precursor is more easily broken into multiple small particles, which not only reduces the sintering difficulty and improves the nickel-lithium mixing phenomenon during the sintering process, but also, after sintering, the large particle precursor is crushed to prepare small particle single crystal materials. The sintering process is more complete, which can reduce the formation of quasi-single crystals and reduce side reactions, thereby obtaining single crystal materials with higher compaction density. That is, it can solve the current problems of high sintering difficulty of single crystal ternary material precursors and reduce the generation of quasi-single crystal particles, which is conducive to industrial production.

[0124] A specific preparation method of a positive electrode material precursor is provided below, as shown in FIG1 , comprising the following steps:

[0125] Step 1, solution preparation stage.

[0126] According to the molar ratio of Ni, Co and Mn in the required nickel-cobalt-manganese hydroxide, Ni soluble salt, Co soluble salt and Mn soluble salt are selected as raw materials, and pure water is added to prepare a nickel-cobalt-manganese salt mixture with a concentration range of 1.2-2.7 mol / L.

[0127] The molar ratio of nickel soluble salt, cobalt soluble salt and manganese soluble salt is (88-96):(2-8):(2-8).

[0128] Prepare a NaOH solution with a concentration range of 1.0-13.0 mol / L as the alkali solution.

[0129] NH3·H2O with a concentration range of 1.0-12.0 mol / L was prepared as a complexing agent.

[0130] Step 2: Open the jacket of the main reactor with a volume range of 180-220L to allow water to flow in and out.

[0131] Step 3, forming the reaction base liquid stage.

[0132] Add 90-110 L of pure water to the main reactor, introduce N2 into the main reactor, control the temperature of the main reactor to be in the range of 50-70°C, and the stirring speed to be in the range of 400-600 rpm. Then add the NaOH solution and NH3·H2O solution prepared in step 1 to form a reaction base solution.

[0133] Step 4, the preparation stage of the positive electrode material precursor particles.

[0134] In step 41, the NaOH solution, NH3·H2O solution, and mixed metal ion solution prepared in step 1 are added to the main reactor in parallel at a first flow ratio under continuous stirring to carry out a reaction. The reaction temperature, reaction atmosphere, reaction solution pH, and ammonia concentration are controlled at a stirring speed range of 450-550 rpm to form seed crystals in the reactor.

[0135] Among them, the first flow ratio range is (0-9):(3-20):(20-133).

[0136] Step 42, pH reduction and stable growth stage: When the seed crystal amount reaches the target, the pH of the reaction solution is reduced, and the reaction temperature, reaction atmosphere, reaction solution pH and ammonia concentration are continuously controlled to maintain the growth of the seed crystal particles in the main reactor.

[0137] Step 5, continue feeding according to step 4, as shown in Figure 2. When the liquid level in the main reactor reaches the filtration requirement, start the concentrator to start filtration, maintain the liquid level in the main reactor stable, and when it is detected that the particle size of the material in the main reactor reaches the required requirement, stop feeding the main reactor, continue stirring and aging for 1-2 hours, and then discharge the seed crystals into the qualified slurry tank.

[0138] Step 6: performing solid-liquid separation on the slurry in the qualified slurry tank in step 5, washing the separated filter cake with NaOH solution or KOH solution, and then rinsing with pure water to obtain a washed filter cake.

[0139] In step 7, the filter cake washed in step 6 is dried using a drying device, and then sieved and demagnetized in sequence to obtain porous, puff-shaped nickel-cobalt-manganese hydroxide.

[0140] In a third aspect, an embodiment of the present application provides a positive electrode material, which includes the above-mentioned positive electrode material precursor.

[0141] In the positive electrode material provided in the embodiment of the present application, during the sintering process, lithium ions can more fully penetrate into the precursor particles and sinter more fully. When crushed, the large-particle precursor is more easily broken into multiple small particles, which not only reduces the difficulty of sintering and improves the nickel-lithium mixing phenomenon during the sintering process, but also, the large-particle precursor is crushed after sintering to prepare small-particle single crystal material. The sintering process is more complete, which can reduce the formation of quasi-single crystals and reduce side reactions, thereby obtaining a positive electrode material with a higher compaction density and facilitating industrial production.

[0142] In a fourth aspect, an embodiment of the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; wherein the positive electrode sheet contains the above-mentioned positive electrode material.

[0143] The secondary battery provided in the embodiments of the present application has a long cycle life and excellent performance.

[0144] In some embodiments, the positive electrode plate includes a current collector and a positive electrode material coated on the current collector. The positive electrode material is prepared by sintering the above-mentioned positive electrode material precursor. The isolation membrane is arranged between the positive electrode plate and the negative electrode plate, and the electrolyte is filled in the secondary battery.

[0145] The following describes the cathode material precursor, preparation method, and application of the cathode material precursor in the embodiments of the present application through a number of specific embodiments.

[0146] Example 1

[0147] This embodiment provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0148] Step 1: Ni-soluble sulfate, Co-soluble sulfate and Mn-soluble sulfate are selected in a molar ratio of 88:6:6, mixed with deionized water, and prepared into a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0149] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0150] Prepare 6 mol / L NH3·H2O solution.

[0151] The NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were maintained at a constant temperature of 25°C.

[0152] Step 2: Open the jacket of the reactor with a volume of 180 L and allow water to flow in and out.

[0153] Step 3: Add 100 L of hot pure water to a 200 L reactor, control the reactor temperature to 60 ° C, and the stirring speed to 500 rpm. Then pump NaOH solution and NH3·H2O solution into the reactor. The concentration of 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 base liquid of the reactor.

[0154] Step 4: After the reaction begins, the flow rates of the NaOH solution, NH3·H2O solution, and mixed metal sulfate solution are set to 9 mL / min, 3 mL / min, and 20 mL / min, respectively, and continuously pumped into a 60°C constant temperature reactor through a feeding trough for reaction. With a stirring speed of 500 rpm, the flow rate of the NaOH solution is adjusted to stabilize the pH value of the synthesis system at 11.5, the flow rate of the NH3·H2O solution is adjusted to maintain the NH3·H2O concentration in the synthesis system at 4.0 g / L, the submerged N2 flow rate in the reactor atmosphere is adjusted to 150 L / h, and the submerged air flow rate is adjusted to 100 L / h. The nucleation time is maintained for 3 minutes.

[0155] At a stirring speed of 500 rpm, the flow of NaOH solution was turned off, the pH value was quickly adjusted to 10.2 and then restored, the flow of NH3·H2O solution was adjusted to maintain the NH3·H2O concentration of the synthesis system at 4.0 g / L, and the submerged N2 flow rate of the reactor atmosphere was adjusted to 150 L / h and the submerged air flow rate to 100 L / h.

[0156] One hour after the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted and slowly increased to 267 mL / min over 6 hours. The flow rates of the NaOH solution and the NH3·H2O solution were simultaneously adjusted to stabilize the pH value at 10.2 and the ammonia value at 3.0. Four hours after the start of the reaction, the N2 flow rate in the reactor atmosphere was adjusted to 100 L / h and the air flow rate in the reactor atmosphere was adjusted to 150 L / h. The oxygen content in the reaction atmosphere was increased by 1% every 4 hours. The stirring speed was reduced in steps according to the particle size D50 of the material. When D50 reached 8 μm, the stirring speed was reduced and maintained at 200 rpm. When D50 reached 13.5-13.6 μm, the reaction was stopped to obtain a porous, puff-shaped large-particle ternary precursor slurry.

[0157] Step 5: discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0158] Step 6: Alternately wash the ternary precursor slurry with alkali and pure water.

[0159] Step 7: Evenly distribute the ternary precursor slurry in a drying device for drying at a drying temperature of 120° C., a drying time of 12 h, and a 325-mesh double-layer screen.

[0160] Through the above steps, a cathode material precursor with high agglomeration, porous puff-like morphology and an average particle size of 10-20 μm can be obtained as shown in Figures 3 to 8.

[0161] Example 2

[0162] This embodiment provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0163] Step 1: Ni-soluble sulfate, Co-soluble sulfate and Mn-soluble sulfate are selected in a molar ratio of 88:4:8, mixed with deionized water, and prepared into a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0164] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0165] Prepare 6 mol / L NH3·H2O solution.

[0166] The NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were maintained at a constant temperature of 25°C.

[0167] Step 2: Open the jacket of the reactor with a volume of 180 L and allow water to flow in and out.

[0168] Step 3: Add 100 L of hot pure water to a 200 L reactor, control the reactor temperature to 60 ° C, and the stirring speed to 500 rpm. Then pump NaOH solution and NH3·H2O solution into the reactor. The concentration of 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 base liquid of the reactor.

[0169] Step 4: After starting the reaction, the flow rates of NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were set to 0 mL / min, 20 mL / min, and 133 mL / min, respectively, and continuously pumped into a 60°C constant temperature reactor through a feeding trough for reaction. With a stirring speed of 500 rpm, the pH value was quickly adjusted to 10.8. The flow rate of NaOH solution was adjusted to stabilize the pH value of the synthesis system at 10.8. The flow rate of NH3·H2O solution was adjusted to maintain the NH3·H2O concentration of the synthesis system at 6.0 g / L. The submerged N2 flow rate of the reactor atmosphere was adjusted to 400 L / h, and the submerged air flow rate was adjusted to 400 L / h.

[0170] One hour after the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted and slowly increased to 417 mL / min over 6 hours. The flow rates of the NaOH solution and the NH3·H2O solution were simultaneously adjusted to stabilize the pH value at 10.8 and the ammonia value at 6.0. Four hours after the start of the reaction, the N2 flow rate in the reactor atmosphere was adjusted to 180 L / h and the air flow rate in the reactor atmosphere was adjusted to 400 L / h. The oxygen content in the reaction atmosphere was increased by 1% every 4 hours. The stirring speed was reduced in steps according to the particle size D50 of the material. When D50 reached 8 μm, the stirring speed was reduced and maintained at 200 rpm. When D50 reached 13.5-13.6 μm, the reaction was stopped to obtain a porous, puff-shaped large-particle ternary precursor slurry.

[0171] Step 5: discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0172] Step 6: Alternately wash the ternary precursor slurry with alkali and pure water.

[0173] Step 7: Evenly distribute the ternary precursor slurry in a drying device for drying at a drying temperature of 120° C., a drying time of 12 h, and a 325-mesh double-layer screen.

[0174] Through the above steps, a cathode material precursor with high agglomeration, porous puff-like morphology and an average particle size of 10-20 μm can be obtained as shown in Figures 9 to 14.

[0175] Example 3

[0176] This embodiment provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0177] Step 1: Ni-soluble sulfate, Co-soluble sulfate and Mn-soluble sulfate are selected in a molar ratio of 96:2:2, mixed with deionized water, and prepared into a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0178] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0179] Prepare 6 mol / L NH3·H2O solution.

[0180] The NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were maintained at a constant temperature of 25°C.

[0181] Step 2: Open the jacket of the reactor with a volume of 180 L and allow water to flow in and out.

[0182] Step 3: Add 100 L of hot pure water to a 200 L reactor, control the reactor temperature to 60 ° C, and the stirring speed to 500 rpm. Then pump NaOH solution and NH3·H2O solution into the reactor. The concentration of 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 base liquid of the reactor.

[0183] Step 4: After starting the reaction, the flow rates of NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were set to 0 mL / min, 20 mL / min, and 133 mL / min, respectively, and continuously pumped into a 60°C constant temperature reactor through a feeding trough for reaction. At a stirring speed of 500 rpm, the pH value was quickly adjusted to 11.3, and the flow rate of NaOH solution was adjusted to stabilize the pH value of the synthesis system at 11.3. The flow rate of NH3·H2O solution was adjusted to maintain the NH3·H2O concentration of the synthesis system at 9.0 g / L. The submerged N2 flow rate of the reactor atmosphere was adjusted to 700 L / h, and the submerged air flow rate was adjusted to 700 L / h.

[0184] One hour after the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted and slowly increased to 417 mL / min over 6 hours. The flow rates of the NaOH solution and the NH3·H2O solution were simultaneously adjusted to stabilize the pH value at 11.3 and the ammonia value at 9.0. Four hours after the start of the reaction, the N2 flow rate in the reactor atmosphere was adjusted to 250 L / h and the air flow rate in the reactor atmosphere was adjusted to 750 L / h. The oxygen content in the reaction atmosphere was increased by 1% every 4 hours. The stirring speed was reduced in steps according to the particle size D50 of the material. When D50 reached 8 μm, the stirring speed was reduced and maintained at 200 rpm. When D50 reached 13.5-13.6 μm, the reaction was stopped to obtain a porous, puff-shaped large-particle ternary precursor slurry.

[0185] Step 5: discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0186] Step 6: Alternately wash the ternary precursor slurry with alkali and pure water.

[0187] Step 7: Evenly distribute the ternary precursor slurry in a drying device for drying at a drying temperature of 120° C., a drying time of 12 h, and a 325-mesh double-layer screen.

[0188] Through the above steps, a cathode material precursor with high agglomeration, porous puff-like morphology and an average particle size of 10-20 μm can be obtained as shown in Figures 15 to 20.

[0189] Comparative Example 1

[0190] This comparative example provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0191] Step 1: Ni-soluble sulfate, Co-soluble sulfate and Mn-soluble sulfate are selected in a molar ratio of 88:6:6, mixed with deionized water, and prepared into a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0192] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0193] Prepare 6 mol / L NH3·H2O solution.

[0194] The NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were maintained at a constant temperature of 25°C.

[0195] Step 2: Open the jacket of the reactor with a volume of 180 L and allow water to flow in and out.

[0196] Step 3: Add 100 L of hot pure water to a 200 L reactor, control the reactor temperature to 60 ° C, and the stirring speed to 500 rpm. Then pump NaOH solution and NH3·H2O solution into the reactor. The concentration of 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 base liquid of the reactor.

[0197] Step 4: After starting the reaction, the flow rates of NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were set to 0 mL / min, 20 mL / min, and 133 mL / min, respectively, and continuously pumped into a 60°C constant temperature reactor through a feeding trough for reaction. With a stirring speed of 500 rpm, the pH value was quickly adjusted to 10.2. The flow rate of NaOH solution was adjusted to stabilize the pH value of the synthesis system at 10.2. The flow rate of NH3·H2O solution was adjusted to maintain the NH3·H2O concentration of the synthesis system at 4.0 g / L. The N2 flow rate in the reactor atmosphere was adjusted to 150 L / h.

[0198] One hour after the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted and slowly increased to 417 mL / min over 6 hours. The flow rates of the NaOH solution and the NH3·H2O solution were simultaneously adjusted to stabilize the pH value at 10.2 and the ammonia value at 3.0. The N2 flow rate in the reactor atmosphere was maintained at 150 L / h. The stirring speed was reduced in steps according to the material particle size D50. When D50 reached 8 μm, the stirring speed was reduced 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.

[0199] Step 5: discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0200] Step 6: Alternately wash the ternary precursor slurry with alkali and pure water.

[0201] Step 7: Evenly distribute the ternary precursor slurry in a drying device for drying at a drying temperature of 120° C., a drying time of 12 h, and a 325-mesh double-layer screen.

[0202] Through the above steps, a large-particle positive electrode material precursor with dense surface morphology as shown in Figures 21 to 26 can be obtained.

[0203] Comparative Example 2

[0204] This comparative example provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0205] Step 1: Ni-soluble sulfate, Co-soluble sulfate and Mn-soluble sulfate are selected in a molar ratio of 88:4:8, mixed with deionized water, and prepared into a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0206] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0207] Prepare 6 mol / L NH3·H2O solution.

[0208] The NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were maintained at a constant temperature of 25°C.

[0209] Step 2: Open the jacket of the reactor with a volume of 180 L and allow water to flow in and out.

[0210] Step 3: Add 100 L of hot pure water to a 200 L reactor, control the reactor temperature to 60 ° C, and the stirring speed to 500 rpm. Then pump NaOH solution and NH3·H2O solution into the reactor. The concentration of 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 base liquid of the reactor.

[0211] Step 4: After starting the reaction, the flow rates of NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were set to 0 mL / min, 20 mL / min, and 133 mL / min, respectively, and continuously pumped into a 60°C constant temperature reactor through a feeding trough for reaction. With a stirring speed of 500 rpm, the pH value was quickly adjusted to 10.8. The flow rate of NaOH solution was adjusted to stabilize the pH value of the synthesis system at 10.8. The flow rate of NH3·H2O solution was adjusted to maintain the NH3·H2O concentration of the synthesis system at 6.0 g / L. The N2 flow rate in the reactor atmosphere was adjusted to 400 L / h.

[0212] One hour after the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted and slowly increased to 417 mL / min over 6 hours. The flow rates of the NaOH solution and the NH3·H2O solution were simultaneously adjusted to stabilize the pH value at 10.8 and the ammonia value at 6.0. The N2 flow rate under the reactor atmosphere was maintained at 400 L / h. The stirring speed was reduced in steps according to the material particle size D50. When D50 reached 8 μm, the stirring speed was reduced 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.

[0213] Step 5: discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0214] Step 6: Alternately wash the ternary precursor slurry with alkali and pure water.

[0215] Step 7: Evenly distribute the ternary precursor slurry in a drying device for drying at a drying temperature of 120° C., a drying time of 12 h, and a 325-mesh double-layer screen.

[0216] Through the above steps, a large-particle positive electrode material precursor with dense surface morphology as shown in Figures 27 to 32 can be obtained.

[0217] Comparative Example 3

[0218] This comparative example provides a method for preparing a positive electrode material precursor, comprising the following steps:

[0219] Step 1: Ni-soluble sulfate, Co-soluble sulfate and Mn-soluble sulfate are selected in a molar ratio of 96:2:2, mixed with deionized water, and prepared into a mixed metal sulfate solution with a concentration of 2.3 mol / L.

[0220] Prepare a NaOH solution with a concentration of 10.5 mol / L.

[0221] Prepare 6 mol / L NH3·H2O solution.

[0222] The NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were maintained at a constant temperature of 25°C.

[0223] Step 2: Open the jacket of the reactor with a volume of 180 L and allow water to flow in and out.

[0224] Step 3: Add 100 L of hot pure water to a 200 L reactor, control the reactor temperature to 60 ° C, and the stirring speed to 500 rpm. Then pump NaOH solution and NH3·H2O solution into the reactor. The concentration of 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 base liquid of the reactor.

[0225] Step 4: After starting the reaction, the flow rates of NaOH solution, NH3·H2O solution, and mixed metal sulfate solution were set to 0 mL / min, 20 mL / min, and 133 mL / min, respectively, and continuously pumped into a 60°C constant temperature reactor through a feeding trough for reaction. With a stirring speed of 500 rpm, the pH value was quickly adjusted to 11.3. The flow rate of NaOH solution was adjusted to stabilize the pH value of the synthesis system at 11.3. The flow rate of NH3·H2O solution was adjusted to maintain the NH3·H2O concentration of the synthesis system at 9.0 g / L. The N2 flow rate in the reactor atmosphere was adjusted to 700 L / h.

[0226] One hour after the start of the reaction, the flow rate of the mixed metal sulfate solution was adjusted and slowly increased to 417 mL / min over 6 hours. The flow rates of the NaOH solution and the NH3·H2O solution were simultaneously adjusted to stabilize the pH value at 11.3 and the ammonia value at 9.0. The N2 flow rate in the reactor atmosphere was maintained at 700 L / h. The stirring speed was reduced in steps according to the particle size D50 of the material. When D50 reached 8 μm, the stirring speed was reduced 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.

[0227] Step 5: discharge the ternary precursor slurry that meets the particle size requirements into the transfer tank and stir it.

[0228] Step 6: Alternately wash the ternary precursor slurry with alkali and pure water.

[0229] Step 7: Evenly distribute the ternary precursor slurry in a drying device for drying at a drying temperature of 120° C., a drying time of 12 h, and a 325-mesh double-layer screen.

[0230] Through the above steps, a large-particle positive electrode material precursor with dense surface morphology as shown in Figures 33 to 38 can be obtained.

[0231] The positive electrode material precursors prepared in Examples 1-3 and Comparative Examples 1-3 of the present application were respectively subjected to Ni content, Co content, Mn content, sodium (Na) content, sulfur (S) content, specific surface area test (BET) and thermal desorption test (TD), and the results are shown in Table 1 below.

[0232] Table 1

[0233] 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, and Examples 1-3 have larger specific surface area, lower sodium content, lower sulfur content, and smaller thermal desorption than Comparative Examples 1-3, respectively.

[0234] As can be seen from the electron micrographs of Figures 3 through 38 , under oxidizing conditions, the surface whiskers of the particles in Examples 1-3 are relatively thin and loose, making impurities such as sodium and sulfur easier to remove during the washing process. Furthermore, the loose surface whiskers of the particles in Examples 1-3 reduce the strength of the precursor, making the particles more easily broken, reducing the difficulty of positive electrode sintering and ensuring more complete sintering.

[0235] It should be noted that the dark color in Figure 5 indicates that the particle density is high, and the lithium ions move into the large particles and are relatively evenly distributed.

[0236] Only the contents related to the invention are introduced here. The rest can be obtained by referring to the relevant technologies and will not be described in detail here.

[0237] The above are merely optional embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A 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%.

3. The precursor of the cathode material according to claim 1, characterized in that, The ratio of the particle size of the first particles to the particle size of the precursor particles ranges from 20% to 50%.

4. 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.

5. The precursor of the cathode material according to claim 1, characterized in that, The specific surface area of the precursor particles ranges from 20 m 2 / g to 40 m 2 / g.

6. The precursor of the cathode material according to any one of claims 2 to 5, characterized in that, The precursor particles further include a shell layer, and the shell layer coats the surface layer of the core-shell structure.

7. The precursor of the cathode material according to claim 6, characterized in that, The thickness of the shell layer ranges from 0.2 μm to 0.5 μm.

8. The precursor of the cathode material according to any one of claims 2 to 5, characterized in that, The thickness of the core of the core-shell structure ranges from 4 μm to 8 μm.

9. 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, respectively prepare a first alkali solution and a complexing agent; After adding water into the reactor and introducing a protective gas, add the first alkali solution and the complexing agent to form a reaction bottom solution; Add the first alkali solution, 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 as 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 as 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.

10. The method for preparing the precursor of the cathode material according to claim 9, wherein, The first atmosphere at least includes the protective gas, and the second atmosphere includes air and the protective gas.

11. The method for preparing the precursor of the cathode material according to claim 9, wherein In the second atmosphere, the air flow rate gradually increases as the solid content of the material increases.

12. The method for preparing the precursor of the cathode material according to claim 10, wherein, The air flow rate range of the first atmosphere is 0 L / h to 800 L / h, and the protective gas flow rate range of the first atmosphere is 100 L / h to 800 L / h.

13. The method for preparing the precursor of the cathode material according to claim 10, wherein The air flow rate range of the second atmosphere is 300 L / h to 800 L / h, and the protective gas flow rate range of the second atmosphere is 0 L / h to 300 L / h.

14. The method for preparing the precursor of the cathode material according to claim 12 or 13, characterized in that, The concentration range of the complexing agent for the nucleation reaction is 2.0 g / L to 10.0 g / L.

15. The method for preparing the precursor of the cathode material according to claim 12 or 13, characterized in that, The concentration range of the complexing agent for the growth reaction is 1.0 g / L to 10.0 g / L.

16. The method for preparing the precursor of the cathode material according to claim 12 or 13, characterized in that, The flow rate range of the mixed metal ion solution is 0.5 L / h to 40 L / h.

17. The method for preparing the precursor of the cathode material according to claim 12 or 13, characterized in that, The flow rate ratio range of the first alkali solution, the complexing agent and the mixed metal ion solution is 0-9:3-20:20-133.

18. The method for preparing the precursor of the cathode material according to claim 12 or 13, characterized in that, The pH value range of the reaction solution is 10.0 to 11.

5.

19. A cathode material, characterized in that, It includes the precursor of the cathode material according to any one of claims 1-8, or the precursor of the cathode material prepared by the method according to any one of claims 9-18.

20. A secondary battery, characterized in that, The secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte; wherein, the positive electrode plate contains the positive electrode material as described in Claim 19.

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