Single crystal positive electrode material precursor, and preparation method therefor and use thereof

Abstract

The present application relates to the technical field of battery materials, and provides a single crystal positive electrode material precursor, and a preparation method therefor and a use thereof. The chemical general formula of the single crystal positive electrode material precursor comprises MnxNiyMe1-x-y(OH)2 or MnxNiyMe1-x-yCO3, wherein 0≤x<1, 0≤y<0.7, and 0≤1-x-y<0.6. The single crystal positive electrode material precursor comprises an inner core and a shell coating the inner core, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of the inner core is higher than the specific surface area of the outer shell. The single crystal positive electrode material precursor provided by the present application has different inner and outer morphology structures, and the dense outer shell can greatly reduce the overall specific surface area of the precursor material and increase the tap density of the precursor material while effectively protecting the loose structure of the inner core, thereby reducing the internal stress in the sintering process of the precursor, and avoiding the problems of generation of micro-powder and oxidation in the postprocess. In addition, the characteristics of the precursor effectively reduce extra high temperature required in the synthesis of a single crystal positive electrode material, large single crystal positive electrode particles can be obtained by means of conventional high-temperature calcination, and the problem of high energy consumption due to high temperature required in the calcination of existing single crystal positive electrode materials is solved.

Description

A single crystal positive electrode material precursor and its preparation method and application Technical Field

[0001] The present application belongs to the field of battery material technology, and in particular relates to a single crystal positive electrode material precursor and its preparation method and application. Background Art

[0002] Single-crystal cathode materials are widely used in lithium / sodium secondary batteries due to their excellent cycle performance, thermal stability, and safety. However, in large-scale industrial production, the temperature required for calcining single-crystal cathode materials is higher than that of conventional polycrystalline cathode materials, resulting in significantly higher production costs than conventional polycrystalline cathodes, which has affected their larger-scale industrialization process. Precursors with loose, large-scale structures are the first choice for sintering single-crystal particles. However, their large-scale characteristics make them easily oxidized to form fine powders during post-processing, reducing the quality of the precursor and making this type of precursor difficult to use in the production of single-crystal cathodes.

[0003] To this end, in order to address the difficulties of producing and processing the above-mentioned single-crystal positive electrode material precursors and the high energy consumption of single-crystal positive electrode preparation, a simple, low-cost, easy-to-operate, and large-scale application-friendly method for the controllable preparation of single-crystal positive electrodes and their precursors has been developed, which is of great significance to the development of new energy materials.

[0004] Summary of the Invention

[0005] The purpose of the present application is to provide a single crystal positive electrode material precursor and a preparation method thereof, aiming to solve the problem that the existing single crystal positive electrode material precursor is easily oxidized to form fine powder during post-processing.

[0006] Another object of the present application is to provide a single crystal positive electrode material and a secondary battery containing the single crystal positive electrode material, aiming to solve the problem that the existing single crystal positive electrode material requires a high calcination temperature and has unsatisfactory cycle performance.

[0007] To achieve the above application objectives, the technical solutions adopted in this application are as follows:

[0008] In the first aspect, the present application provides a single crystal positive electrode material precursor, the chemical formula of the single crystal positive electrode material precursor includes Mn x Ni y Me 1-x-y (OH)2 or Mn x Ni y Me 1-x-y CO3, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb, and Zr, and 0≤x<1, 0≤y<0.7, and 0≤1-xy<0.6;

[0009] The single crystal positive electrode material precursor includes a core and a shell covering the core, wherein the shell is formed by a plurality of needle-shaped primary particles, wherein the tap density of the core is lower than the tap density of the shell, and the specific surface area of ​​the core is higher than the specific surface area of ​​the shell.

[0010] In a second aspect, the present application provides a method for preparing a single crystal cathode material precursor, comprising the following steps:

[0011] Step S10, preparing a metal mixed salt solution, a complexing agent solution and a precipitant solution, wherein the metal mixed salt solution contains nickel, manganese and Me, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb and Zr;

[0012] Step S20, mixing the metal mixed salt solution, the complexing agent solution, and the precipitant solution independently at a first predetermined flow rate and performing a first coprecipitation reaction, and obtaining a first reaction solution containing the core when the product of the first coprecipitation reaction reaches a first predetermined particle size;

[0013] Step S30: adding the remaining metal mixed salt solution, the remaining complexing agent solution, and the remaining precipitant solution to the first reaction solution at a second predetermined flow rate to perform a second co-precipitation reaction, coating the inner core with an outer shell, and obtaining a single crystal cathode material precursor when the product of the second co-precipitation reaction reaches a second predetermined particle size;

[0014] The first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction is less than the second predetermined flow rate of the remaining complexing agent solution in the second coprecipitation reaction.

[0015] In a third aspect, the present application provides a single crystal positive electrode material, which is prepared by calcining a mixture of the single crystal positive electrode material precursor of the present application and / or the single crystal positive electrode material precursor obtained by the preparation method of the single crystal positive electrode material precursor of the present application and a lithium salt or sodium salt.

[0016] In a fourth aspect, the present application provides a secondary battery comprising the single crystal positive electrode material of the present application.

[0017] The single crystal positive electrode material precursor provided in the first aspect of the present application includes an inner core with a loose structure having low tap density and large surface area, and a dense outer shell with high tap density and small specific surface area formed by stacking multiple needle-shaped primary particles. The outer shell can effectively protect the morphology and structure of the inner core while significantly reducing the overall specific surface area of ​​the precursor material and increasing its tap density, thereby helping to reduce the internal stress of the precursor during sintering and avoiding the problems of fine powder, oxidation, and too low tap density during post-processing. In addition, the gaps between adjacent primary particles in the outer shell are conducive to promoting the rapid entry of lithium salt or sodium salt into the inner core, so that the inner core with an internal loose structure still promotes the formation of a single crystal structure during calcination.

[0018] The preparation method of the single crystal positive electrode material precursor provided in the second aspect of the present application is to form a low tap density, a large surface area, and a core with a loose morphology structure by a first coprecipitation reaction, and to adjust the second predetermined flow rate of the complexing agent solution in the second coprecipitation reaction so that the density of the precursor core and the shell is different during the second coprecipitation reaction, and to promote the rapid growth of the precursor particles, and to form a dense shell formed by a plurality of needle-shaped primary particles with uniform morphology on the surface of the core, thereby effectively preparing a precursor material with different internal and external morphological structures, so that the precursor material has a core with a large specific surface area and a low tap density, and a shell with a large specific surface area and a high tap density. In addition, the preparation method is simple, reliable and controllable, and is more conducive to large-scale industrial production.

[0019] The single crystal positive electrode material provided in the third aspect of the present application is prepared by using the single crystal positive electrode material precursor of the present application. The single crystal positive electrode material precursor has different internal and external morphological structures, so that the precursor can obtain single crystal positive electrode particles under calcination conditions with lithium salt or sodium salt at conventional temperature, which effectively reduces production costs and is more conducive to promotion and development.

[0020] The secondary battery provided in the fourth aspect of the present application contains the single crystal positive electrode material of the present application, and the single crystal positive electrode material is sintered from an inner-loose and outer-tight precursor, so that the secondary battery has more stable safety and longer service life, thereby effectively improving the cycle performance of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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 descriptions of the prior art. 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.

[0022] FIG1 is a scanning electron microscope photograph of a single crystal cathode material precursor provided in Example A1 of the present application;

[0023] FIG2 is a scanning electron microscope photograph of a single crystal cathode material precursor provided in Comparative Example D1 of the present application;

[0024] FIG3 is a scanning electron microscope photograph of a single crystal cathode material precursor provided in Comparative Example D2 of the present application;

[0025] FIG4 is a scanning electron microscope photograph of a single crystal cathode material provided in Example B1 of the present application;

[0026] FIG5 is a scanning electron microscope photograph of the single crystal positive electrode material provided in Comparative Example E2 of the present application. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0028] 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 represent: 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.

[0029] In this application, "at least one" means one or more, and "more than one" 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, and c can be single or multiple.

[0030] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. 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.

[0031] 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.

[0032] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0033] The terms "first" and "second" 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 quantity of the 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" or "second" may explicitly or implicitly include one or more of such features.

[0034] It should be noted that:

[0035] Tap density refers to the mass per unit volume of powder in a container measured after tapping under specified conditions. Tap density is defined as the mass of the sample divided by its volume, which includes the sample itself and the volume of the sample's pores and interstitial spaces.

[0036] Specific surface area refers to the surface area per unit mass of a porous solid material. It is usually measured by low-temperature nitrogen adsorption method using the BET theory.

[0037] In a first aspect, an embodiment of the present application provides a single crystal positive electrode material precursor, the chemical formula of which includes Mn x Ni y Me 1-x-y (OH)2 or Mn x Ni y Me 1-x-y CO3, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb, and Zr, and 0≤x<1, 0≤y<0.7, and 0≤1-xy<0.6;

[0038] The single crystal positive electrode material precursor includes a core and a shell covering the core, wherein the shell is formed by a plurality of needle-shaped primary particles, wherein the tap density of the core is lower than the tap density of the shell, and the specific surface area of ​​the core is higher than the specific surface area of ​​the shell.

[0039] The single crystal positive electrode material precursor provided in the first aspect of the embodiment of the present application includes an inner core with a loose structure having low tap density and large surface area, and a dense outer shell with high tap density and small specific surface area formed by stacking multiple needle-shaped primary particles. The outer shell can effectively protect the morphology and structure of the inner core while significantly reducing the overall specific surface area of ​​the precursor material and increasing its tap density, thereby helping to reduce the internal stress of the precursor during sintering and avoiding the problems of fine powder, oxidation, and too low tap density during post-processing. In addition, the gaps between adjacent primary particles in the outer shell are conducive to promoting the rapid entry of lithium salt or sodium salt into the inner core, so that the inner core with an internal loose structure still promotes the formation of a single crystal structure during calcination.

[0040] The single crystal positive electrode material precursor provided in the embodiment of the present application has better structural stability by regulating the ratio of the various metal elements it contains. When it is applied to single crystal positive electrode materials and secondary batteries, the secondary batteries have more stable safety and longer service life, thereby making the secondary batteries exhibit better cycle stability.

[0041] In some specific embodiments, the single crystal positive electrode material precursor can be a precursor containing only nickel and manganese elements, that is, a nickel-manganese binary single crystal positive electrode material precursor, or a precursor containing only manganese and Me elements, that is, a manganese-Me single crystal positive electrode material precursor, or a precursor containing nickel and Me elements, that is, a nickel-Me single crystal positive electrode material precursor. Of course, it can also contain Me elements in addition to nickel and manganese elements, that is, a nickel-manganese-Me single crystal positive electrode material precursor. It should be noted that the Me element includes at least one element. Therefore, in the embodiments of the present application, the single crystal positive electrode material precursor can also be a quaternary precursor, a quinary precursor, etc.

[0042] In some embodiments, the single crystal positive electrode material precursor provided in the embodiments of the present application has a spherical or quasi-spherical morphology, which is conducive to subsequent uniform mixing with lithium salt and sodium salt.

[0043] In some embodiments, the tap density of the core is 0.4 to 1.2 g / cm 3 The tap density of the shell is 1.25~1.6g / cm 3 The inner core has a loose structure with low tap density, which can effectively relieve the internal stress during the sintering process, avoid the micro-powder and oxidation of the precursor during the post-processing process, and is also conducive to the penetration of active ions, thereby promoting the formation of single crystal positive electrode materials when the precursor is calcined. The outer shell has a dense structure with high tap density, which can effectively protect the loose inner core it covers, and can also increase the overall tap density of the precursor material. The tap density is the key to increasing the capacity. In this way, the high-density outer shell can also greatly increase the capacity of the single crystal positive electrode material. Specifically, the tap density of the inner core can be 0.4g / cm3 , 0.5g / cm 3 , 0.6g / cm 3 、 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 Or within the range of any of the above values. Specifically, the tap density of the shell includes but is not limited to 1.25g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 .

[0044] In some embodiments, the specific surface area of ​​the core is 18 to 100 m 2 / g, the specific surface area of ​​the shell is 3 to 15m 2 / g. The dense shell with a small specific surface area can effectively protect the loose structure of the core inside, while promoting the formation of single crystal positive electrode particles during calcination, effectively improving the structural stability of the single crystal positive electrode material, thereby improving its cycle performance and service life. Specifically, the specific surface area of ​​the core includes but is not limited to 18m 2 / g, 25m 2 / g、30m 2 / g, 40m 2 / g, 50m 2 / g, 60m 2 / g、70m 2 / g、80m 2 / g、90m 2 / g、100m 2 / g. Specifically, the specific surface area of ​​the shell includes but is not limited to 3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g、15m 2 / g.

[0045] In some embodiments, the radius R of the inner core and the ring diameter D of the outer shell satisfy: 1 / 10R≤D≤1 / 3R. The ring diameter refers to the absolute value of the difference between the radii of two circles in a ring figure. A ring is a ring-shaped geometric figure, or more generally, a ring-shaped object. In geometry, a ring is usually referred to as a circular ring, which is the part left after a small concentric disk is dug out from a large disk. It should be understood that in the present application, the single crystal positive electrode material precursor is spherical or quasi-spherical, and its section or cross-section along the center of the sphere is annular or quasi-annular. If the radius of the inner core is too large, the tap density of the precursor material will be low, the specific surface area will be large, and the overall strength of the particles will be insufficient, thereby making the cycle performance of the secondary battery prepared from the precursor low; if the radius of the inner core is too small, it will be unfavorable for the formation of single crystal positive electrode particles under low temperature conditions. Specifically, the ring diameter D of the housing may include but is not limited to satisfying the following conditions: D=1 / 10R, D=1 / 9R, D=1 / 8R, D=1 / 6R, D=1 / 5R, D=1 / 4R, and D=1 / 3R.

[0046] In some embodiments, the particle size of the single crystal positive electrode material precursor is 3 to 17 μm. The macroscopic particles of the single crystal positive electrode material precursor provided in the embodiment of the present application are micron-sized, which is beneficial to shorten the diffusion distance of active ions in the single crystal positive electrode material precursor and is more conducive to the formation of single crystal positive electrode materials during low temperature calcination. Specifically, the particle size of the single crystal positive electrode material precursor can be 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 15 μm, 17 μm or within the range of any of the above values.

[0047] In some embodiments, the specific surface area of ​​the single crystal cathode material precursor is 4 to 15 g / cm 3 If the specific surface area is too low, it means that there are too few pores in the precursor material, which makes the active ion transmission rate in the single crystal positive electrode material precursor material low; if the specific surface area is too high, it means that there are too many pores in the single crystal positive electrode material precursor material, which affects its structural stability and makes the positive electrode precursor material have a lower tap density. Specifically, the specific surface area of ​​the single crystal positive electrode material precursor includes but is not limited to 4m 2 / g、6m 2 / g、8m 2 / g、10m 2 / g、12m 2 / g、15m 2 / g or within the range consisting of any of the above values.

[0048] In some embodiments, the tap density of the single crystal cathode material precursor is 0.8 to 1.4 g / cm 3. Generally speaking, the higher the tap density, the higher the capacity and energy density of the battery. However, in the prior art, a higher calcination temperature must be used to prepare a precursor with too high a tap density into a single crystal positive electrode material. Within the tap density range of the single crystal positive electrode material precursor provided in the embodiment of the present application, when the single crystal positive electrode material precursor is applied to the single crystal positive electrode material, not only can lower calcination conditions be adopted, but also a higher capacity can be given while ensuring the safety and stability of its structure. Specifically, the tap density of the single crystal positive electrode material precursor can be 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 Or within the range of any of the above values.

[0049] A second aspect of the present invention provides a method for preparing a single crystal cathode material precursor, comprising the following steps:

[0050] Step S10, preparing a metal mixed salt solution, a complexing agent solution and a precipitant solution, wherein the metal mixed salt solution contains nickel, manganese and Me, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb and Zr;

[0051] Step S20, mixing the metal mixed salt solution, the complexing agent solution, and the precipitant solution independently at a first predetermined flow rate and performing a first coprecipitation reaction, and obtaining a first reaction solution containing the core when the product of the first coprecipitation reaction reaches a first predetermined particle size;

[0052] Step S30: adding the remaining metal mixed salt solution, the remaining complexing agent solution, and the remaining precipitant solution to the first reaction solution at a second predetermined flow rate to perform a second co-precipitation reaction, coating the inner core with an outer shell, and obtaining a single crystal cathode material precursor when the product of the second co-precipitation reaction reaches a second predetermined particle size;

[0053] The first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction is less than the second predetermined flow rate of the remaining complexing agent solution in the second coprecipitation reaction.

[0054] The preparation method of the single crystal positive electrode material precursor provided in the second aspect of the embodiment of the present application is to form a low tap density, a large surface area, and a core with a loose morphology structure by a first coprecipitation reaction, and to adjust the second predetermined flow rate of the complexing agent solution in the second coprecipitation reaction so that the density of the precursor core and the shell are different during the second coprecipitation reaction, and to promote the rapid growth of the precursor particles, and to form a dense shell formed by a plurality of needle-shaped primary particles with uniform morphology on the surface of the core, thereby effectively preparing a precursor material with different internal and external morphological structures, so that the precursor material has a core with a large specific surface area and a low tap density, and a shell with a large specific surface area and a high tap density. In addition, the preparation method is simple, reliable and controllable, and is more conducive to large-scale industrial production.

[0055] The preparation method provided in the embodiment of the present application is beneficial to increasing the growth rate of the shell precursor particles by increasing the flow rate of the complexing agent solution in the second co-precipitation reaction, so that the density of the precursor core is lower than the density of the shell. In this way, the structure and morphology of the core and shell of the single crystal positive electrode material precursor can be controlled. By maintaining the flow rate of the precipitant solution and the metal mixed salt solution during the first co-precipitation reaction and the second co-precipitation reaction, while ensuring the same chemical composition of the precursor core and shell, the morphology of the primary particles of the precursor shell is ensured to remain unchanged, thereby ensuring that a single crystal positive electrode material precursor with a low degree of oxidation, uniform element distribution, no segregation, uniform particle size distribution, and high tap density is obtained.

[0056] In some embodiments, in step S10, the concentration of the metal ions in the metal mixed salt solution is 100-130 g / L. Specifically, the concentration of the metal ions in the metal mixed salt solution can be 100 g / L, 105 g / L, 110 g / L, 115 g / L, 120 g / L, 125 g / L, 130 g / L, or any range thereof.

[0057] In some embodiments, in step S10, according to the chemical formula of the single crystal cathode material precursor Mn x Ni y Me 1-x-y (OH)2 or Mn x Ni y Me 1-x-y The values ​​of x and y in CO3 are respectively measured, and the manganese salt, nickel salt and Me salt are added into appropriate amount of pure water to dissolve to obtain a mixed metal salt solution containing nickel, manganese and Me.

[0058] In some specific embodiments, in step S10, the metal mixed salt solution is at least one of sulfate, chloride, nitrate, and acetate.

[0059] In some specific embodiments, in step S10, the metal mixed salt solution may also be a single metal salt solution.

[0060] Exemplarily, a nickel salt soluble solution, a cobalt salt soluble solution, and a Me salt soluble solution are prepared, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb, and Zr.

[0061] In some embodiments, in step S10, the molar concentration of the precipitant solution is 5 to 10 mol / L. Specifically, the molar concentration of the precipitant solution can be 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, or any range thereof.

[0062] In some embodiments, in step S10, the precipitant in the precipitant solution includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, ammonium bicarbonate, sodium oxalate, ammonium oxalate, and oxalic acid.

[0063] In some embodiments, in step S10, the molar concentration of the complexing agent solution is 5 to 10 mol / L. Specifically, the molar concentration of the complexing agent solution can be 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, or any range thereof.

[0064] In some embodiments, in step S10, the complexing agent in the complexing agent solution includes at least one of ammonium sulfate, ammonium nitrate, ammonia water, oxalic acid, citric acid, sodium citrate, disodium edetate, carbonamide, and ammonium fluoride. The complexing agents provided in the embodiments of the present application can be complexed with metal ions during the coprecipitation reaction to form metal ion complexes, which then react with the precipitant and decomplex. The main purpose is to achieve simultaneous homogeneous precipitation of different metal ions, control the growth direction of the seed crystals, and improve the sphericity and tap density of the product.

[0065] In some embodiments, in step S20, the conditions of the first coprecipitation reaction include: a reaction temperature of 25 to 48°C, a pH value of 10.2 to 10.9, and a reaction time of 30 to 50 hours. For example, the reaction temperature may be 25°C, 30°C, 35°C, 40°C, 45°C, 48°C, or within the range of any of the above values. The pH value may be 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, or within the range of any of the above values. The reaction time may be 30 hours, 32 hours, 35 hours, 38 hours, 40 hours, 42 hours, 45 hours, 50 hours, or within the range of any of the above values. Within the range of the first coprecipitation reaction conditions provided in the embodiments of the present application, a core with a loose morphology structure may be obtained.

[0066] In some embodiments, in step S20 and step S30, the first predetermined flow rate of the metal mixed salt solution in the first coprecipitation reaction is 200-450 L / h, and the second predetermined flow rate of the metal mixed salt solution remaining in the second coprecipitation reaction is the same as the first predetermined flow rate of the metal mixed salt solution in the first coprecipitation reaction. In an embodiment of the present application, the flow rate of the metal mixed salt solution in the first coprecipitation reaction is the same as that in the second coprecipitation reaction, that is, the content of the metal ions to be reacted is the same within the same time, ensuring that the chemical composition of the core and shell of the precursor material is the same, and also ensuring that the elements in the precursor material are uniformly distributed. Specifically, the first predetermined flow rate of the mixed metal salt solution in the first coprecipitation reaction can be 200 L / h, 230 L / h, 250 L / h, 270 L / h, 300 L / h, 320 L / h, 350 L / h, 370 L / h, 400 L / h, 45 L / h0 or within the range of any of the above values.

[0067] In some embodiments, in step S20, the first predetermined flow rate of the precipitant solution in the first coprecipitation reaction is 70 to 140 L / h, and the second predetermined flow rate of the precipitant solution remaining in the second coprecipitation reaction is the same as the first predetermined flow rate of the precipitant solution in the first coprecipitation reaction. In an embodiment of the present application, the flow rate of the precipitant solution in the first coprecipitation reaction is the same as that in the second coprecipitation reaction, that is, the content of the precipitant to be reacted is the same within the same time, ensuring that the chemical composition of the core and shell of the precursor material is the same, and also ensuring that the elements in the precursor material are uniformly distributed. Specifically, the first predetermined flow rate of the precipitant solution in the first coprecipitation reaction can be 70 L / h, 80 L / h, 90 L / h, 100 L / h, 110 L / h, 120 L / h, 130 L / h, 140 L / h or within the range of any of the above values.

[0068] In some embodiments, in step S20, the first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction is 8 to 25 L / h, and the second predetermined flow rate of the remaining complexing agent solution in the second coprecipitation reaction is 30 to 70 L / h. In the embodiment of the present application, the second predetermined flow rate of the remaining complexing agent solution in the second coprecipitation reaction is required to be higher than the first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction, so that the metal ion complexation rate in the second coprecipitation reaction is accelerated, thereby increasing the reaction rate of the metal ions and the precipitant, and then forming a dense shell on the surface of the inner core. The first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction can be 8 L / h, 10 L / h, 12 L / h, 15 L / h, 18 L / h, 20 L / h, 22 L / h, 25 L / h or within the range of any of the above values. The second predetermined flow rate of the remaining complexing agent solution in the second coprecipitation reaction can be 30L / h, 35L / h, 38L / h, 40L / h, 50L / h, 55L / h, 60L / h, 70L / h or within a range consisting of any of the above values.

[0069] In some embodiments, in step S20, the first coprecipitation reaction can be determined to be complete based on whether the product of the first coprecipitation reaction reaches a first predetermined particle size. The first predetermined particle size D1 and the second predetermined particle size D2 satisfy the following conditions:

[0070] (1) 1 / 2(D2-D1) is equivalent to the ring diameter D of the shell mentioned above, and 1 / 2D1 is equivalent to the radius R of the core mentioned above, which satisfies 1 / 10R≤D≤1 / 3R;

[0071] (2)3μm≤D2≤17μm.

[0072] It is understandable that the completion of the reaction can also be determined based on the reaction time of the first coprecipitation reaction.

[0073] In some embodiments, in step S30, the conditions for the second coprecipitation reaction include: a reaction temperature of 60 to 75° C., a pH value of 10.9 to 12.6, and a reaction time of 20 to 50 hours. For example, the reaction temperature can be 60° C., 62° C., 64° C., 65° C., 67° C., 68° C., 70° C., 72° C., 75° C., or within a range thereof. The pH value can be 10.9, 11.0, 11.2, 11.5, 11.7, 12.0, 12.2, 12.5, 12.6, or within a range thereof. The reaction time can be 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, or within a range thereof. Under the conditions of the second coprecipitation reaction provided in the embodiment of the present application, the precursor particles can be induced to grow in an oriented manner during the coprecipitation reaction, so that multiple needle-shaped primary particles are stacked into a shell with a higher density, and the overall sphericity of the precursor material can also be improved.

[0074] In some embodiments, in step S30, after stopping the feeding, the slurry containing the single crystal positive electrode material precursor is further subjected to a treatment process of filtering, washing, drying, screening, and demagnetizing to obtain the single crystal positive electrode material precursor.

[0075] A third aspect of an embodiment of the present application provides a single crystal positive electrode material, which is prepared by calcining a mixture of a single crystal positive electrode material precursor of the present application and / or a single crystal positive electrode material precursor obtained by the preparation method of the single crystal positive electrode material precursor of the present application and a lithium salt or sodium salt.

[0076] The single crystal positive electrode material provided in the third aspect of the embodiment of the present application is prepared using the single crystal positive electrode material precursor of the present application. The single crystal positive electrode material precursor has different internal and external morphological structures, so that the precursor can obtain single crystal positive electrode particles under calcination conditions with lithium salt or sodium salt at conventional temperature, which effectively reduces production costs and is more conducive to promotion and development.

[0077] In some specific embodiments, the lithium salt includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium oxalate, and lithium sulfate.

[0078] In some specific embodiments, the sodium salt includes one or more of sodium hydroxide, sodium carbonate, sodium nitrate, sodium acetate, sodium oxalate, and sodium sulfate.

[0079] In some embodiments, the molar ratio of lithium ions in the lithium salt to the single crystal cathode material precursor is 0.55 to 1.27: 1. Specifically, the molar ratio of lithium ions to the single crystal cathode material precursor may include, but is not limited to, 0.55: 1, 0.65: 1, 0.75: 1, 0.9: 1, 1: 1, and 1.27: 1.

[0080] In some embodiments, the molar ratio of sodium ions in the sodium salt to the single crystal cathode material precursor is 0.6 to 1.1: 1. Specifically, the molar ratio of sodium ions to the single crystal cathode material precursor may include, but is not limited to, 0.6: 1, 0.7: 1, 0.8: 1, 0.9: 1, 0.95: 1, 1: 1, and 1.1: 1.

[0081] In some embodiments, a method for preparing a single crystal cathode material comprises the following steps:

[0082] A10. Mix the single crystal positive electrode material precursor with lithium salt or sodium salt, sinter at 400-650°C for 3-8 hours, and then sinter at 650-950°C for 7-13 hours to obtain a single crystal positive electrode material.

[0083] The method for preparing a single-crystal cathode material provided in the embodiments of the present application utilizes a single-crystal cathode material precursor comprising a core having a low tap density and a large surface area with a loose structure, and an outer shell having a high tap density and a small specific surface area as raw materials. This allows for a two-stage calcination process during the cathode material preparation process, resulting in a single-crystal cathode material being obtained at low temperatures. This preparation method is simple, reduces the difficulty and cost of calcination, and is more conducive to large-scale industrial production.

[0084] A fourth aspect of an embodiment of the present application provides a secondary battery, comprising the single crystal positive electrode material of the present application.

[0085] The secondary battery provided in the fourth aspect of the embodiment of the present application contains the single crystal positive electrode material of the present application, and the single crystal positive electrode material is sintered from an inner-loose and outer-tight precursor, so that the secondary battery has more stable safety and longer service life, thereby effectively improving the cycle performance of the secondary battery.

[0086] The following describes the details in conjunction with specific embodiments.

[0087] Example A1

[0088] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0089] A single crystal cathode material precursor with the chemical formula Ni 0.34 Fe 0.33 Mn 0.33 (OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0090] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0091] Step S1, prepare the following solution:

[0092] Mixed metal salt solution: obtained by dissolving nickel sulfate, ferrous sulfate, and manganese sulfate crystals in water; wherein the total concentration of nickel, iron, and manganese is 100 g / L, and the molar ratio of nickel, iron, and manganese is 0.34:0.33:0.33;

[0093] Complexing agent solvent: obtained by adding ammonia water to water, with a molar concentration of 4.5 mol / L;

[0094] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 10 mol / L.

[0095] Step S2, first coprecipitation reaction:

[0096] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for a first coprecipitation reaction. The conditions for controlling the first coprecipitation reaction are: pH value of 10.5, temperature of 40°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 127 L / h, and the flow rate of the complexing agent solution is 13 L / h. When the particle size D50 of the precipitate reaches 9.5 μm, the feeding is stopped to obtain a first reaction solution containing the core.

[0097] Step S3, second coprecipitation reaction:

[0098] The pH of the first reaction solution prepared in the above step S1 is adjusted to 11.5, and the temperature is adjusted to 60°C. Then, the remaining metal mixed salt solution, complexing agent solution and precipitant are fed at a uniform speed through metering pumps respectively to carry out a second coprecipitation reaction. In the second coprecipitation reaction, the flow rate of the complexing agent solution is controlled to be 31 L / h, and the flow rates of the metal mixed salt solution and the precipitant remain unchanged (the same as their respective flow rates in the first coprecipitation reaction). When the particle size D50 of the precipitate reaches 12 μm, the feeding is stopped to obtain a slurry containing a single crystal positive electrode material precursor.

[0099] Step S4, post-processing:

[0100] The slurry containing the single crystal cathode material precursor is filtered, washed, dried, batched, sieved, and demagnetized to obtain a single crystal cathode material precursor, denoted as NFM111. The washing includes alkali washing and water washing. The alkali washing is performed using a sodium hydroxide solution with a concentration of 0.8 mol / L, and the water washing is performed using pure water.

[0101] Example A2

[0102] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0103] A single crystal cathode material precursor, chemical formula Ni 0.2 Co 0.1 Mn 0.7 (OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0104] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0105] Step S1, prepare the following solution:

[0106] Mixed metal salt solution: obtained by dissolving nickel sulfate, cobalt chloride, and manganese sulfate crystals in water; wherein the total concentration of nickel, cobalt, and manganese is 100 g / L, and the molar ratio of nickel, cobalt, and manganese is 2:1:7;

[0107] Complexing agent solvent: obtained by adding ammonia water to water, with a molar concentration of 4.8 mol / L;

[0108] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 9 mol / L.

[0109] Step S2, first coprecipitation reaction:

[0110] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for a first coprecipitation reaction. The conditions for controlling the first coprecipitation reaction are: pH value of 10.2, temperature of 35°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 90 L / h, and the flow rate of the complexing agent solution is 19 L / h. When the particle size D50 of the precipitate reaches 4 μm, the feeding is stopped to obtain a first reaction solution containing the core.

[0111] Step S3, second coprecipitation reaction:

[0112] The pH of the first reaction solution prepared in the above step S1 is adjusted to 11.5, and the temperature is adjusted to 65°C. Then, the remaining metal mixed salt solution, complexing agent solution and precipitant are fed at a uniform speed through metering pumps respectively to carry out a second coprecipitation reaction. In the second coprecipitation reaction, the flow rate of the complexing agent solution is controlled to be 35 L / h, and the flow rates of the metal mixed salt solution and the precipitant remain unchanged (the same as their respective flow rates in the first coprecipitation reaction). When the particle size D50 of the precipitate reaches 5 μm, the feeding is stopped to obtain a slurry containing a single crystal positive electrode material precursor.

[0113] Step S4 is the same as step S4 in embodiment A1, except that the single crystal positive electrode material precursor is denoted as NCM.

[0114] Example A3

[0115] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0116] A single crystal cathode material precursor with the chemical formula Ni 0.38 Mn 0.62 (OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0117] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0118] Step S1, prepare the following solution:

[0119] Metal mixed salt solution: obtained by dissolving nickel sulfate and manganese sulfate crystals in water; wherein the total concentration of nickel and manganese is 120g / L, and the molar ratio of nickel to manganese is 38:62;

[0120] Complexing agent solvent: obtained by adding ammonia water to water, with a molar concentration of 4.5 mol / L;

[0121] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 10 mol / L.

[0122] Step S2, first coprecipitation reaction:

[0123] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for a first coprecipitation reaction. The conditions for controlling the first coprecipitation reaction are: pH value of 10.2, temperature of 35°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 90 L / h, and the flow rate of the complexing agent solution is 17 L / h. When the particle size D50 of the precipitate reaches 3.5 μm, the feeding is stopped to obtain a first reaction solution containing the core.

[0124] Step S3, second coprecipitation reaction:

[0125] The pH of the first reaction solution prepared in the above step S1 is adjusted to 11.6, and the temperature is adjusted to 68°C. Then, the remaining metal mixed salt solution, complexing agent solution and precipitant are fed at a uniform speed through metering pumps respectively to carry out a second coprecipitation reaction. In the second coprecipitation reaction, the flow rate of the complexing agent solution is controlled to be 55 L / h, and the flow rates of the metal mixed salt solution and the precipitant remain unchanged (the same as their respective flow rates in the first coprecipitation reaction). When the particle size D50 of the precipitate reaches 4.5 μm, the feeding is stopped to obtain a slurry containing a single crystal positive electrode material precursor.

[0126] Step S4 is the same as step S4 in embodiment A1, except that the single crystal positive electrode material precursor is denoted as NM3862.

[0127] Example A4

[0128] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0129] A single crystal cathode material precursor with the chemical formula Ni 0.25 Mn 0.75 (OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0130] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0131] Step S1, prepare the following solution:

[0132] Metal mixed salt solution: obtained by dissolving nickel sulfate and manganese sulfate crystals in water; wherein the total concentration of nickel and manganese is 100g / L, and the molar ratio of nickel to manganese is 1:3;

[0133] Complexing agent solvent: obtained by adding ammonia water to water, with a molar concentration of 4.8 mol / L;

[0134] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 9 mol / L.

[0135] Step S2 is different from step S2 of Example A2 in that the temperature of the first coprecipitation reaction is 38°C.

[0136] Step S3 is different from step S3 of Example A2 in that the pH of the first reaction solution is adjusted to 12 and the temperature is adjusted to 70°C.

[0137] Step S4 is the same as step S4 in embodiment A1, except that the single crystal positive electrode material precursor is recorded as spinel NM.

[0138] Example A5

[0139] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0140] A single crystal cathode material precursor with the chemical formula Ni 0.5 Co 0.2 Mn 0.3(OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0141] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0142] Step S1, prepare the following solution:

[0143] Mixed metal salt solution: obtained by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate crystals in water; wherein the total concentration of nickel, cobalt, and manganese is 108 g / L, and the molar ratio of nickel, cobalt, and manganese is 5:2:3;

[0144] Complexing agent solvent: obtained by adding ammonia water to water, with a molar concentration of 4.8 mol / L;

[0145] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 9 mol / L.

[0146] Step S2 is different from step S2 of Example A2 in that the temperature of the first coprecipitation reaction is 40°C.

[0147] Step S3 is different from step S3 of Example A2 in that the pH of the first reaction solution is adjusted to 10.9 and the temperature is adjusted to 70°C.

[0148] Step S4 is the same as step S4 in embodiment A1, except that the single crystal positive electrode material precursor is recorded as NCM523.

[0149] Example A6

[0150] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0151] A single crystal cathode material precursor with the chemical formula Ni 0.33 Co 0.34 Mn 0.33 (OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0152] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0153] Step S1, prepare the following solution:

[0154] Mixed metal salt solution: obtained by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate crystals in water; wherein the total concentration of nickel, cobalt, and manganese is 100 g / L, and the molar ratio of nickel, cobalt, and manganese is 1:1:1;

[0155] Complexing agent solvent: obtained by adding ammonia water to water, with a molar concentration of 4.8 mol / L;

[0156] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 9 mol / L.

[0157] Step S2 differs from step S2 of Example A2 in that the conditions for the first coprecipitation reaction are: pH 10.7, temperature 45° C., and flow rate of the complexing agent solution 13 L / h.

[0158] Step S3 is different from step S3 of Example A2 in that the conditions for the second coprecipitation reaction are: pH 11 and temperature 70°C.

[0159] Step S4 is the same as step S4 in embodiment A1, except that the single crystal positive electrode material precursor is denoted as NCM111.

[0160] Example A7

[0161] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0162] A single crystal cathode material precursor with the chemical formula Ni 0.3 Cu 0.1 Fe 0.3 Mn 0.3 (OH)2, including an inner core and an outer shell stacked on the outer surface of the inner core, the outer shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the inner core is lower than the tap density of the outer shell, and the specific surface area of ​​the inner core is higher than the specific surface area of ​​the outer shell.

[0163] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0164] Step S1, prepare the following solution:

[0165] Metal mixed salt solution: obtained by dissolving nickel sulfate, copper sulfate, ferrous sulfate, and manganese sulfate crystals in water; wherein the total concentration of nickel, copper, iron, and manganese is 110 g / L, and the molar ratio of nickel, copper, iron, and manganese is 0.3:0.1:0.3:0.3;

[0166] Complexing agent solvent: obtained by adding oxalic acid to water, with a molar concentration of 4 mol / L;

[0167] Precipitant solution: prepared by dissolving sodium hydroxide in water, with a molar concentration of 6 mol / L.

[0168] Step S2, first coprecipitation reaction:

[0169] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for a first coprecipitation reaction. The conditions for controlling the first coprecipitation reaction are: pH value of 10.2, temperature of 48°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 196 L / h, and the flow rate of the complexing agent solution is 15 L / h. When the particle size D50 of the precipitate reaches 8.5 μm, the feeding is stopped to obtain a first reaction solution containing the core.

[0170] Step S3, second coprecipitation reaction:

[0171] The pH of the first reaction solution prepared in the above step S1 is adjusted to 11.9, and the temperature is adjusted to 70°C. Then, the remaining metal mixed salt solution, complexing agent solution and precipitant are fed at a uniform speed through metering pumps respectively to carry out a second coprecipitation reaction. In the second coprecipitation reaction, the flow rate of the complexing agent solution is controlled to be 50 L / h, and the flow rates of the metal mixed salt solution and the precipitant remain unchanged (the same as their respective flow rates in the first coprecipitation reaction). When the particle size D50 of the precipitate reaches 10 μm, the feeding is stopped to obtain a slurry containing a single crystal positive electrode material precursor.

[0172] Step S4 is the same as step S4 in Example A1, except that: the alkaline washing is performed using a sodium hydroxide solution with a concentration of 0.4 mol / L, and the single crystal positive electrode material precursor is recorded as NCFM3133.

[0173] Example A8

[0174] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0175] A single crystal cathode material precursor with the chemical formula Cu 0.2 Fe 0.4 Mn 0.4 CO3 includes a core and a shell stacked on the outer surface of the core, the shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the core is lower than the tap density of the shell, and the specific surface area of ​​the core is higher than the specific surface area of ​​the shell.

[0176] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0177] Step S1, prepare the following solution:

[0178] Mixed metal salt solution: obtained by dissolving copper sulfate, ferrous sulfate, and manganese sulfate crystals in water; wherein the total concentration of copper, iron, and manganese is 100 g / L, and the molar ratio of copper, iron, and manganese is 2:4:4;

[0179] Complexing agent solvent: obtained by adding oxalic acid to water, with a molar concentration of 4 mol / L;

[0180] Precipitant solution: prepared by dissolving sodium carbonate in water, with a molar concentration of 3 mol / L.

[0181] Step S2, first coprecipitation reaction:

[0182] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for a first coprecipitation reaction. The conditions for controlling the first coprecipitation reaction are: pH value of 10.8, temperature of 45°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 102 L / h, and the flow rate of the complexing agent solution is 15 L / h. When the particle size D50 of the precipitate reaches 10 μm, the feeding is stopped to obtain a first reaction solution containing the core.

[0183] Step S3, second coprecipitation reaction:

[0184] The pH of the first reaction solution prepared in the above step S1 is adjusted to 10.9, and the temperature is adjusted to 65°C. Then, the remaining metal mixed salt solution, complexing agent solution and precipitant are fed at a uniform speed through metering pumps respectively to carry out a second coprecipitation reaction. In the second coprecipitation reaction, the flow rate of the complexing agent solution is controlled to be 40 L / h, and the flow rates of the metal mixed salt solution and the precipitant remain unchanged (the same as their respective flow rates in the first coprecipitation reaction). When the particle size D50 of the precipitate reaches 12 μm, the feeding is stopped to obtain a slurry containing a single crystal positive electrode material precursor.

[0185] Step S4 is the same as step S4 in embodiment A7, except that the single crystal positive electrode material precursor is denoted as CFM244.

[0186] Example A9

[0187] This embodiment provides a single crystal positive electrode material precursor and a preparation method thereof.

[0188] A single crystal cathode material precursor with the chemical formula Ni 0.4 Fe 0.2 Mn 0.4 CO3 includes a core and a shell stacked on the outer surface of the core, the shell is formed by stacking multiple needle-shaped primary particles, wherein the tap density of the core is lower than the tap density of the shell, and the specific surface area of ​​the core is higher than the specific surface area of ​​the shell.

[0189] A method for preparing a single crystal positive electrode material precursor comprises the following steps:

[0190] Step S1, prepare the following solution:

[0191] Mixed metal salt solution: obtained by dissolving nickel sulfate, ferrous sulfate, and manganese sulfate crystals in water; wherein the total concentration of nickel, iron, and manganese is 120 g / L, and the molar ratio of copper, iron, and manganese is 2:4:4;

[0192] Complexing agent solvent: obtained by adding oxalic acid to water, with a molar concentration of 2 mol / L;

[0193] Precipitant solution: prepared by dissolving sodium carbonate in water, with a molar concentration of 3 mol / L.

[0194] Step S2, first coprecipitation reaction:

[0195] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for a first coprecipitation reaction. The conditions for controlling the first coprecipitation reaction are: pH value of 10.5, temperature of 48°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 122 L / h, and the flow rate of the complexing agent solution is 20 L / h. When the particle size D50 of the precipitate reaches 4.5 μm, the feeding is stopped to obtain a first reaction solution containing the core.

[0196] Step S3, second coprecipitation reaction:

[0197] The pH of the first reaction solution prepared in the above step S1 is adjusted to 11.5, and the temperature is adjusted to 70°C. Then, the remaining metal mixed salt solution, complexing agent solution and precipitant are fed at a uniform speed through metering pumps respectively to carry out a second coprecipitation reaction. In the second coprecipitation reaction, the flow rate of the complexing agent solution is controlled to be 47 L / h, and the flow rates of the metal mixed salt solution and the precipitant remain unchanged (the same as their respective flow rates in the first coprecipitation reaction). When the particle size D50 of the precipitate reaches 6 μm, the feeding is stopped to obtain a slurry containing a single crystal positive electrode material precursor.

[0198] Step S4 is the same as step S4 in Example A1, except that: the alkaline washing is performed using a sodium hydroxide solution with a concentration of 0.9 mol / L, and the single crystal positive electrode material precursor is recorded as NFM424.

[0199] Comparative Example D1

[0200] This comparative example provides a positive electrode precursor and a preparation method thereof.

[0201] A cathode precursor NFM111, the chemical formula is Ni 0.34 Fe 0.33 Mn 0.33 (OH)2.

[0202] A method for preparing a positive electrode precursor comprises the following steps:

[0203] Step S1 is the same as step S1 of embodiment A1.

[0204] Step S2, coprecipitation reaction:

[0205] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for co-precipitation reaction. The conditions for controlling the co-precipitation reaction are: pH value of 10.5, temperature of 40°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 127 L / h, and the flow rate of the complexing agent solution is 13 L / h. When the particle size D50 of the precipitate reaches 12 μm, the feeding is stopped to obtain a slurry containing the precursor.

[0206] Step S3 is the same as step S4 in embodiment A1.

[0207] Comparative Example D2

[0208] This comparative example provides a positive electrode precursor and a preparation method thereof.

[0209] A cathode precursor NFM111, the chemical formula is Ni 0.34 Fe 0.33 Mn 0.33 (OH)2.

[0210] A method for preparing a positive electrode precursor comprises the following steps:

[0211] Step S1 is the same as step S1 of embodiment A1.

[0212] Step S2, coprecipitation reaction:

[0213] The metal mixed salt solution, complexing agent solution and precipitant solution prepared in the above step S1 are fed at a uniform speed by metering pumps respectively and added to the reaction vessel for co-precipitation reaction. The conditions for controlling the co-precipitation reaction are: pH value 11.5, temperature 60°C, wherein the flow rate of the metal mixed salt solution is 330 L / h, the flow rate of the precipitant solution is 127 L / h, and the flow rate of the complexing agent solution is 31 L / h. When the particle size D50 of the precipitate reaches 12 μm, the feeding is stopped to obtain a slurry containing the precursor.

[0214] Step S3 is the same as step S4 in embodiment A1.

[0215] Example B1

[0216] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0217] A single crystal positive electrode material includes sodium carbonate and the single crystal positive electrode material precursor NFM111 prepared in Example A1, wherein the molar ratio of sodium ions to NFM111 is 0.9:1.

[0218] A method for preparing a single crystal positive electrode material comprises the following steps:

[0219] Step 1: Mix the single crystal cathode material precursor NFM111 with sodium carbonate, then sinter at 500°C for 4 hours, and then sinter at 880°C for 10 hours to obtain the NFM111 single crystal cathode material.

[0220] Example B2

[0221] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0222] A single crystal positive electrode material comprises lithium carbonate and the single crystal positive electrode material precursor NCM prepared in Example A2, wherein the molar ratio of lithium ions to NCM is 1.25:1.

[0223] A method for preparing a single crystal positive electrode material comprises the following steps:

[0224] Step 1: Mix the single crystal positive electrode material precursor NCM with lithium carbonate, then sinter at 500°C for 5 hours, and then sinter at 870°C for 13 hours to obtain the NCM single crystal positive electrode material.

[0225] Example B3

[0226] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0227] A single crystal positive electrode material includes sodium carbonate and the single crystal positive electrode material precursor NM3862 prepared in Example A3, wherein the molar ratio of sodium ions to NM3862 is 0.95:1.

[0228] A method for preparing a single crystal positive electrode material comprises the following steps:

[0229] Step 1: Mix the single crystal positive electrode material precursor NM3862 with sodium carbonate, then sinter at 500°C for 4 hours, and then sinter at 900°C for 10 hours to obtain the NM3862 single crystal positive electrode material.

[0230] Example B4

[0231] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0232] A single crystal positive electrode material comprises lithium carbonate and the single crystal positive electrode material precursor spinel NM prepared in Example A4, wherein the molar ratio of lithium ions to spinel NM is 0.55:1.

[0233] A method for preparing a single crystal positive electrode material comprises the following steps:

[0234] Step 1: Mix the single crystal positive electrode material precursor spinel NM with lithium carbonate, then sinter at 540°C for 5 hours and then sinter at 920°C for 13 hours to obtain the spinel NM single crystal positive electrode material.

[0235] Example B5

[0236] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0237] A single crystal positive electrode material includes lithium hydroxide and the single crystal positive electrode material precursor NCM523 prepared in Example A5, wherein the molar ratio of lithium ions to NCM523 is 0.55:1.

[0238] A method for preparing a single crystal positive electrode material comprises the following steps:

[0239] Step 1: Mix the single crystal cathode material precursor NCM523 with lithium hydroxide, then sinter at 540°C for 5 hours and then sinter at 880°C for 15 hours to obtain a ternary NCM523 single crystal cathode material.

[0240] Example B6

[0241] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0242] A single crystal positive electrode material includes lithium hydroxide and the single crystal positive electrode material precursor NCM111 prepared in Example A6, wherein the molar ratio of lithium ions to NCM111 is 0.55:1.

[0243] A method for preparing a single crystal positive electrode material comprises the following steps:

[0244] Step 1: Mix the single crystal cathode material precursor NCM523 with lithium hydroxide, then sinter at 550°C for 5 hours and then sinter at 780°C for 13 hours to obtain the ternary NCM111 single crystal cathode material.

[0245] Example B7

[0246] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0247] A single crystal positive electrode material includes sodium carbonate and the single crystal positive electrode material precursor NCFM3133 prepared in Example A7, wherein the molar ratio of sodium ions to NCFM3133 is 0.95:1.

[0248] A method for preparing a single crystal positive electrode material comprises the following steps:

[0249] Step 1: Mix the single crystal positive electrode material precursor NCFM3133 with sodium carbonate, then sinter at 500°C for 4 hours, and then sinter at 860°C for 11 hours to obtain the NCFM3133 single crystal positive electrode material.

[0250] Example B8

[0251] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0252] A single crystal positive electrode material includes sodium carbonate and the single crystal positive electrode material precursor CFM244 prepared in Example A8, wherein the molar ratio of sodium ions to CFM244 is 0.95:1.

[0253] A method for preparing a single crystal positive electrode material comprises the following steps:

[0254] Step 1: Mix the single crystal positive electrode material precursor CFM244 with sodium carbonate, then sinter at 550°C for 4 hours, and then sinter at 850°C for 10 hours to obtain the CFM244 single crystal positive electrode material.

[0255] Example B9

[0256] This embodiment provides a single crystal positive electrode material and a preparation method thereof.

[0257] A single crystal positive electrode material includes sodium carbonate and the single crystal positive electrode material precursor CFM424 prepared in Example A9, wherein the molar ratio of sodium ions to CFM424 is 0.95:1.

[0258] A method for preparing a single crystal positive electrode material comprises the following steps:

[0259] Step 1 is the same as step S1 in Example B8.

[0260] Comparative Example E1

[0261] This comparative example provides a positive electrode material and a preparation method thereof.

[0262] A positive electrode material, which differs from Example B1 in that the single crystal positive electrode material precursor NFM111 prepared in Example A1 is replaced by the single crystal positive electrode material precursor NFM111 prepared in Comparative Example D1, and its component selection, proportions between the components and preparation process are consistent with Example B1.

[0263] Comparative Example E2

[0264] This comparative example provides a positive electrode material and a preparation method thereof.

[0265] A positive electrode material, which differs from Example B1 in that the single crystal positive electrode material precursor NFM111 prepared in Example A1 is replaced by the single crystal positive electrode material precursor NFM111 prepared in Comparative Example D2, and its component selection, proportions between the components, and preparation process are consistent with Example B1.

[0266] Assembly of secondary batteries

[0267] The positive electrode materials prepared in Examples B1 to B9 and Comparative Examples E1 to E2 were used to prepare positive electrodes for secondary batteries, and the secondary batteries were assembled into button batteries according to the following method.

[0268] Assembly method of lithium secondary battery:

[0269] Positive electrode sheet: The positive electrode material, binder (polyvinylidene fluoride), and conductive agent (acetylene black) are dispersed in a solvent (N-methylpyrrolidone solution) in a mass ratio of 9:0.5:0.5 to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on aluminum foil, dried in a vacuum drying oven at 120°C for 12 hours, rolled, and then punched into 14 mm discs as positive electrode sheets.

[0270] Counter electrode: metallic lithium sheet.

[0271] Membrane: Celgard 2400 microporous polypropylene membrane.

[0272] Lithium battery electrolyte: 1mo1 / L LiPF6 / EC+DMC (volume ratio 1:1).

[0273] Assembly of button cells: Assemble button-type lithium-ion batteries in an argon atmosphere glove box in the order of positive electrode sheet-diaphragm-electrolyte-metal lithium sheet.

[0274] Assembly method of sodium secondary battery:

[0275] Positive electrode sheet: The positive electrode material, binder (polyvinylidene fluoride), and conductive agent (acetylene black) are dispersed in a solvent (N-methylpyrrolidone solution) in a mass ratio of 9:0.5:0.5 to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on aluminum foil, dried in a vacuum drying oven at 120°C for 12 hours, rolled, and then punched into 14 mm discs as positive electrode sheets.

[0276] Counter electrode: sodium metal sheet.

[0277] Separator: Use 20μm PP / PE / PP separator.

[0278] Lithium battery electrolyte: 1.0M NaPF6 / EC:DEC=1:1 Vol%.

[0279] Assembly of button cells: Assemble button-type sodium-ion batteries in an argon atmosphere glove box in the order of positive electrode sheet-diaphragm-electrolyte-metal sodium sheet.

[0280] Performance Testing

[0281] (1) Physical property test

[0282] The single crystal positive electrode material precursor materials prepared in Examples A1 to A9 and the positive electrode precursor materials prepared in Comparative Examples D1 to D2 were tested for specific surface area and tap density, respectively. The results are shown in Table 1 below.

[0283] According to Table 1, by controlling the conditions of the first coprecipitation reaction and the second coprecipitation reaction, precursor materials with different core and shell morphologies can be formed. More specifically, the cores obtained by the first coprecipitation reaction in this embodiment all have the characteristics of large specific surface area and low tap density. The specific surface area of ​​the precursor obtained by the second coprecipitation reaction clearly shows a downward trend, and the tap density is significantly increased. In addition, in combination with Example A1 and Comparative Example D1, it can be seen that the first coprecipitation reaction can obtain a morphology structure with a large specific surface area and low tap density. In combination with Example A1 and Comparative Example D2, it is shown that the second coprecipitation reaction can form a morphology structure with a low specific surface area and high tap density.

[0284] Table 1

[0285] (2) Physical property characterization

[0286] The cathode precursor materials prepared in Example A1, Comparative Example D1, and Comparative Example D2 were analyzed by scanning electron microscopy (SEM), and the results are shown in Figures 1 to 3.

[0287] As can be seen from Figure 1, the shell of the single-crystal positive electrode material precursor is formed by a stack of multiple needle-shaped primary particles. Combining Figures 1 and 2, it can be clearly observed that the precursor of Comparative Example D1, obtained using the first coprecipitation reaction alone, exhibits a loose structure and a large number of micropowder particles with inconsistent morphology on the particle surface. In contrast, the precursor prepared in Example A1 in Figure 1 exhibits a uniform primary particle morphology with no micropowder particles observed. This indicates that this compact external structure can effectively protect the existence of the loose internal structure, suppressing the formation of the disordered precursor particle morphology in Comparative Example D1.

[0288] Comparing FIG1 and FIG3, it can be seen that the precursor of comparative example D2 obtained by using the second coprecipitation reaction alone exhibits the characteristics of uniformity, no fine powder, and a tight surface.

[0289] Therefore, to address the problems of loose, large-surface-area precursors, such as easy particle adhesion, surface oxidation to produce fine powder, and difficulty in sieving during post-processing, while the harsh conditions exceeding conventional high-temperature calcination required to prepare single-crystal positive electrode materials from small-surface-area, compact precursors, the corresponding examples employ a precursor core with a loose, large-surface-area core and a compact, small-surface-area shell, combining the complementary advantages of both for easy sintering and simple post-processing. This negative electrode material exhibits a three-dimensional skeleton structure and a small amount of macroporous structure.

[0290] Furthermore, in order to verify the superiority of the morphological structure of the precursor prepared in this embodiment (the inner core is prepared as a loose large specific surface area, and the outer shell is prepared as a compact small specific surface area), the precursors in Example A1 and Comparative Example D2 are mixed with sodium and calcined, and the positive electrode morphology obtained after calcination is shown in Figures 4-5. It can be clearly observed from Figure 4 that the precursor prepared in Example A1, which is loose inside and compact outside, exhibits the characteristics of large single crystal particles after calcination. However, the compact precursor prepared in Comparative Example D2 corresponding to Figure 5 still maintains a polycrystalline structure after calcination, and the size of the primary particles is significantly smaller than that in Figure 4, indicating that the precursor with a loose interior and a compact exterior is more suitable for obtaining large single crystal particles at a lower calcination temperature.

[0291] It should be noted that the precursor morphologies and structures prepared in the remaining embodiments (Examples A2 to A9) are all loose inside, large specific surface area, and low tap density, and compact outside, small specific surface area, and high tap density. In addition, the positive electrode materials after sintering are all single crystal particles, and no phenomenon such as micropowder particles generated on the surface of the precursor that affects the quality of the precursor is observed.

[0292] (3) Electrochemical performance

[0293] The secondary batteries prepared in Examples B1 to B9 and Comparative Examples D1 to D2 were subjected to the following performance tests, and the results are shown in Table 2 below.

[0294] Table 2

[0295] Table 2 shows the electrochemical performance data of the samples. It shows that the single-crystal particles obtained in Examples B1-B9 exhibit more stable cycling performance, with capacity retention rates generally maintained above 80% after 150 cycles. In contrast, the polycrystalline particles obtained in Comparative Examples E1-E2 exhibit significantly lower cycling stability, with capacity retention rates significantly lower after 150 cycles than the single-crystal particles in Example 1. Therefore, the single-crystal particle samples obtained through the internally loose, externally tight precursor sintering method proposed in this invention exhibit more stable safety and service life.

[0296] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A single crystal cathode material precursor, characterized in that: The chemical formula of the single crystal cathode material precursor includes Mn x Ni y Me 1-x-y (OH)2 or Mn x Ni y Me 1-x-y CO3, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb, and Zr, 0≤x<1, 0≤y<0.7, 0≤1-xy<0.6; The single crystal positive electrode material precursor comprises a core and a shell covering the core, wherein the shell is composed of a plurality of needle-shaped primary particles, wherein the tap density of the core is lower than the tap density of the shell, and the specific surface area of ​​the core is higher than the specific surface area of ​​the shell.

2. The single crystal cathode material precursor according to claim 1, characterized in that: The tap density of the inner core is 0.4 to 1.2 g / cm 3 The tap density of the shell is 1.25 to 1.6 g / cm 3 ; and / or The specific surface area of ​​the core is 18 to 100 m 2 / g, the specific surface area of ​​the shell is 3 to 15m 2 / g.

3. The single crystal cathode material precursor according to claim 1, characterized in that: The radius R of the inner core and the ring diameter D of the outer shell satisfy: 1 / 10R≤D≤1 / 3R; and / or The particle size of the single crystal positive electrode material precursor is 3 to 17 μm; and / or The specific surface area of ​​the single crystal positive electrode material precursor is 4 to 15 g / cm 3 ; and / or The tap density of the single crystal positive electrode material precursor is 0.8 to 1.4 g / cm 3 .

4. A method for preparing a single crystal positive electrode material precursor, characterized in that: The following steps are involved: A metal mixed salt solution, a complexing agent solution and a precipitant solution are prepared, wherein the metal mixed salt solution contains nickel, manganese and Me, wherein Me includes at least one of Cu, Fe, Co, Sr, Ca, Zn, Al, Ti, Ta, Mg, Nd, Sn, La, W, Nb and Zr; The metal mixed salt solution, the complexing agent solution and the precipitant solution are mixed separately at a first predetermined flow rate to perform a first coprecipitation reaction, and when the product of the first coprecipitation reaction reaches a first predetermined particle size, a first reaction solution containing a core is obtained; The remaining metal mixed salt solution, the remaining complexing agent solution and the remaining precipitant solution are added to the first reaction solution at a second predetermined flow rate to perform a second coprecipitation reaction, and the outer shell is coated on the surface of the inner core. When the product of the second coprecipitation reaction reaches a second predetermined particle size, When the temperature reaches 10000 °C, a single crystal cathode material precursor is obtained; Wherein, a first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction is less than a second predetermined flow rate of the complexing agent solution remaining in the second coprecipitation reaction.

6. The method for preparing a single crystal cathode material precursor according to claim 5, characterized in that: The conditions of the first coprecipitation reaction include: reaction temperature of 25-48° C., pH value of 10.2-10.9, reaction time of 30-50 h; and / or The conditions of the second coprecipitation reaction include: reaction temperature of 60-75° C., pH value of 10.9-12.6, and reaction time of 20-50 h.

7. The method for preparing a single crystal cathode material precursor according to claim 5, characterized in that: The first predetermined flow rate of the metal mixed salt solution in the first coprecipitation reaction is 200-450 L / h, and the second predetermined flow rate of the metal mixed salt solution remaining in the second coprecipitation reaction is the same as the first predetermined flow rate of the metal mixed salt solution in the first coprecipitation reaction; and / or The first predetermined flow rate of the precipitant solution in the first coprecipitation reaction is 70 to 140 L / h, and the second predetermined flow rate of the remaining precipitant solution in the second coprecipitation reaction is the same as the first predetermined flow rate of the precipitant solution in the first coprecipitation reaction; and / or The first predetermined flow rate of the complexing agent solution in the first coprecipitation reaction is 8 to 25 L / h, and the second predetermined flow rate of the remaining complexing agent solution in the second coprecipitation reaction is 30 to 70 L / h.

8. The method for preparing a single crystal cathode material precursor according to any one of claims 5 to 7, characterized in that: The concentration of metal ions in the metal mixed salt solution is 100-130 g / L; and / or The molar concentration of the precipitant solution is 5 to 10 mol / L; and / or The molar concentration of the complexing agent solution is 5-10 mol / L.

9. A single crystal positive electrode material, characterized in that: The single crystal positive electrode material is prepared by calcining a mixture of the single crystal positive electrode material precursor described in any one of claims 1 to 4 and / or the single crystal positive electrode material precursor obtained by the preparation method of the single crystal positive electrode material precursor described in any one of claims 5 to 8 and a lithium salt or a sodium salt.

10. A secondary battery, characterized in that: Comprising the single crystal positive electrode material as claimed in claim 9.

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