Precursor and preparation method therefor, positive electrode active material and preparation method therefor, positive electrode and lithium-ion battery

Abstract

The present application provides a precursor of a positive electrode active material. A particle of the precursor comprises a core and a shell covering the core. The material of each of the core and the shell is nickel cobalt manganese oxide or nickel cobalt manganese hydroxide. The core is doped with a fluxing agent, and the fluxing agent is selected from one or more of oxides, carbonic acid compounds, and hydroxides of Sr, Li, Mg, Ni, Co, and Zr. The shell is doped with a reaction inhibitor. The reaction inhibitor is selected from one or more of lithium compounds, oxides, carbonic acid compounds, hydroxides, and other compounds of Ta, W, Al, Mn, Mo, and La. A fluxing agent is disposed in the core of the particle of the precursor, and the reaction inhibitor is disposed in the shell, so that subsequent crystallization of the precursor develops from inside to outside. The present application further provides a positive electrode active material and a preparation method therefor, a positive electrode comprising the positive electrode active material, a lithium-ion battery, and a preparation method for the precursor.

Description

Precursor and preparation method thereof, positive electrode active material and preparation method thereof, positive electrode and lithium ion battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to a Chinese patent application filed with the Patent Office of China on December 12, 2023, with application number 202311705633.8 and application name “Precursor and preparation method thereof, positive electrode active material and preparation method thereof, positive electrode and lithium-ion battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to a precursor of a positive electrode active material and a preparation method thereof, a preparation method of the positive electrode active material, the positive electrode active material prepared by the preparation method, and a positive electrode and a lithium ion battery containing the positive electrode active material. Background Art

[0004] Currently, ternary cathode materials are primarily produced through the coprecipitation method to prepare precursors. This precursor is then mixed with an appropriate amount of lithium source and additives and subjected to high-temperature solid-phase sintering to produce ternary single crystals of a specific particle size. By manipulating the precursor manufacturing process, we can further control the precursor's main element content, trace element content, particle size distribution, specific surface area, tap density, sphericity, density, whisker thickness, and crystal plane parameters, resulting in a variety of ternary precursors that meet project requirements. At present, during the high-temperature solid-phase sintering process, most precursors will form multiple crystal nuclei. Due to ion migration at high temperature, the crystal nuclei further aggregate and develop, and certain micro-agglomerations will be formed during this period. High-intensity airflow crushing and other means must be used to achieve the effect of dispersing single crystals. However, it is impossible to completely avoid the presence of twins, quasi-single crystals and other structural morphologies in the crushed materials. When such morphological materials are prepared into batteries for charging and discharging, they are prone to cracking due to phase change, lattice distortion and other reasons, exposing new surfaces to undergo side reactions with the electrolyte, thereby deteriorating the electrochemical properties of the battery materials.

[0005] Summary of the Invention

[0006] In view of this, the first aspect of the present application provides a precursor of a positive electrode active material, wherein particles of the precursor include a core and a shell covering the core.

[0007] The materials of the core and the shell are both nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide, and the chemical formula of nickel-cobalt-manganese hydroxide is Ni x Co y Mn z (OH)2, the chemical formula of nickel, cobalt and manganese oxide is Ni x Co y Mn zO, where 0.33≤x≤1.0, 0≤y≤0.33, x+y+z=1;

[0008] The core is doped with a flux, and the flux is selected from one or more oxides, carbonate compounds, and hydroxides of Sr, Li, Mg, Ni, Co, and Zr;

[0009] The shell is doped with a reaction restraining agent, and the reaction restraining agent is selected from one or more compounds such as lithium compounds, oxides, carbonate compounds, hydroxides, etc. of Ta, W, Al, Mn, Mo, and La.

[0010] The precursor particles of the present application are provided with a flux in the core and a reaction restraint in the shell, so that the subsequent crystallization of the precursor develops from the inside out, that is, the closer to the center of the core, the better and more complete the crystallization. The shell is added with a high-valent cationic additive as a reaction restraint, which can inhibit the crystallization and ion migration of the precursor, resulting in a large difference in the critical reaction temperature of the core and shell. The precursor using this structure can produce highly dispersed and highly spherical single-crystal ternary positive electrode active materials.

[0011] A second aspect of the present application provides a method for preparing a positive electrode active material, comprising:

[0012] The precursor of the positive electrode active material and the lithium source of the first aspect are subjected to a primary sintering, wherein the primary sintering temperature ranges from 600 to 950° C. and the atmosphere is air or a high-purity oxygen atmosphere;

[0013] The product of the primary sintering is mixed with an active inhibitor and subjected to secondary sintering, wherein the temperature range of the secondary sintering is 300 to 850° C. and the atmosphere is a high-purity oxygen atmosphere;

[0014] The product of the secondary sintering is mixed with a nano coating capable of inhibiting reaction with an electrolyte and improving the kinetics of a material interface reaction, and then sintered for a third time. The temperature range of the third sintering is 300-850° C., and the atmosphere is a high-purity oxygen atmosphere.

[0015] Adding an activity inhibitor during secondary sintering reduces surface energy, inhibiting ion migration between adjacent precursors that leads to secondary crystallization. The core-shell surface energy is higher than the interparticle surface energy, leading to inward-directed particle growth. This precursor structure, combined with an activity inhibitor during secondary sintering, yields highly dispersed, spherical, single-crystal ternary cathode active materials.

[0016] The third aspect of the present application provides a positive electrode active material, which is prepared using the preparation method described in the second aspect.

[0017] In a fourth aspect, the present application provides a positive electrode, comprising a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode active material prepared by the preparation method described in the second aspect.

[0018] In a fifth aspect, the present application provides a lithium-ion battery, comprising a positive electrode, a separator, and a negative electrode stacked in sequence, wherein the positive electrode is the positive electrode described in the third aspect.

[0019] A sixth aspect of the present application provides a method for preparing a precursor of the positive electrode active material according to the first aspect, comprising:

[0020] Nickel salt, cobalt salt and manganese salt were mixed with water to obtain solution I;

[0021] Adding the precipitated alkali solution into the reaction vessel;

[0022] Continuously introducing the solution I and the complexing agent solution into the reaction container to react and generate precursor particles;

[0023] Adding a flux metal salt solution into the reaction vessel, wherein the flux metal salt solution is at least one of Sr salt, Li salt, Mg salt, Ni salt, Co salt, and Zr salt;

[0024] When the precursor particles grow to 1.2-1.6 μm, gradually reducing the rate at which the flux metal salt solution is added to the reaction vessel until it stops;

[0025] adding a reaction restraining agent metal salt solution into the reaction vessel, and gradually increasing the rate at which the reaction restraining agent metal salt solution is added dropwise to the reaction vessel, wherein the reaction restraining agent metal salt solution comprises at least one of Ta oxide, W salt, Al salt, Mn salt, Mo salt, and La salt;

[0026] The reaction is stopped, and the slurry in the reaction container is centrifuged, filtered, washed, dried, and sieved to obtain precursor particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic diagram of particles of a precursor of a positive electrode active material according to an embodiment of the present application.

[0028] FIG2 is a scanning electron microscope image of the positive electrode active material of Example 1 of the present application.

[0029] FIG3 is an X-ray diffraction pattern of the positive electrode active material of Example 1 of the present application.

[0030] FIG4 is a scanning electron microscope image of the positive electrode active material of Example 2 of the present application.

[0031] FIG5 is an X-ray diffraction pattern of the positive electrode active material of Example 2 of the present application. DETAILED DESCRIPTION

[0032] The present application provides a precursor for a positive electrode active material for a lithium-ion battery. As shown in Figure 1, the precursor particles 10 include a core 11 and a shell 13 surrounding the core 11. The ternary precursor particles are made of nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide. Specifically, the core 11 and shell 13 primarily contain nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide.

[0033] The chemical formula of nickel, cobalt, manganese hydroxide is Ni x Co y Mn z (OH)2, the chemical formula of nickel, cobalt and manganese oxide is Ni x Co y Mn z O, where 0.33≤x≤1.0, 0≤y≤0.33, x+y+z=1.

[0034] In the present application, the core 11 is doped with a flux. The flux is selected from one or more oxides, carbonates, and hydroxides of Sr, Li, Mg, Ni, Co, and Zr. The weight of the doped flux is 100-2000 ppm based on the weight of the precursor. The flux aids in the crystallization of the precursor.

[0035] In the present application, the shell 13 is doped with a reaction-constraining agent. The reaction-constraining agent is selected from one or more compounds such as lithium compounds, oxides, carbonate compounds, and hydroxides of Ta, W, Al, Mn, Mo, and La. The weight of the doped reaction-constraining agent is 100-4000 ppm based on the weight of the precursor. The reaction-constraining agent is a high-valent cation that inhibits crystallization and ion migration of the precursor.

[0036] As the flux concentration gradually decreases from the center of the core 11 toward the outer shell 13, the concentration of the reaction confinement agent gradually increases. The closer to the center of the core, the higher the concentration of the flux and the lower the concentration of the reaction confinement agent. In this way, by designing the gradient of the flux and reaction confinement agent, the subsequent single crystal growth of the precursor is guided from the inside out.

[0037] The outer surface of the core 11 is uneven and serrated, which can increase the contact area between the core 11 and the shell 13. There are gaps between the serrations of the core 11, and the subsequent lithium source entering the precursor particles can be used to gather some residual lithium.

[0038] The outer diameter of the particles of the ternary precursor is in the range of 3.0 to 8.0 μm. The diameter of the core of the particles of the ternary precursor is greater than or equal to 1.3 μm. The specific surface area of ​​the particles of the ternary precursor is 5 to 50 m 2 / g.

[0039] The present application also provides a method for preparing the precursor of the positive electrode active material, comprising the following steps S1 to S7.

[0040] Step S1: Add water to nickel salt, cobalt salt, and manganese salt and mix them evenly to obtain solution I. The molar ratio of nickel, cobalt, and manganese is x:y:z, wherein 0.33≤x≤1.0, 0≤y≤0.33, and x+y+z=1.

[0041] Step S2: Adding a precipitating alkaline solution to a reaction vessel. The alkali in the precipitating alkaline solution is used to react with the nickel salt, cobalt salt, and manganese salt in Solution I to form a hydroxide precipitate. The alkali may be, but is not limited to, sodium hydroxide.

[0042] Step S3: Continuously introduce solution I and the complexing agent solution into the reaction vessel to react and generate precursor particles. The complexing agent solution is ammonia water, and the complexing agent is used to complex the reactants to enable nucleation and growth.

[0043] Step S4: adding a flux metal salt solution into the reaction container, wherein the flux metal salt solution is selected from at least one of Sr salt, Li salt, Mg salt, Ni salt, Co salt and Zr salt.

[0044] Step S5: When the core of the precursor particle grows to 1.3-1.6 μm, the rate of dripping the flux metal salt solution into the reaction container is gradually reduced until it stops.

[0045] Step S6: adding a metal salt / oxide solution of a reaction restraining agent into the reaction container, and gradually increasing the speed of dripping the metal salt solution of the reaction restraining agent into the reaction container.

[0046] During the process of step S4 to step S6, solution I and the complexing agent solution are also continuously fed into the reaction vessel. In addition, during the process of step S3 to step S5, the rate of addition of solution I is constant. When proceeding to step S6, the rate of addition of solution I can be increased to obtain the outer surface of the kernel 11 with an uneven, jagged shape.

[0047] The metal salt / oxide solution of the reaction restraining agent is selected from at least one of Ta oxide, W salt, Al salt, Mn salt, Mo salt, and La salt. For example, when the reaction restraining agent is a Ta compound, tantalum pentoxide may be used in step S6; when the reaction restraining agent is a W compound, ammonium tungstate or sodium tungstate may be used in step S6; when the reaction restraining agent is an Al compound, aluminum nitrate or sodium metaaluminate may be used in step S6; when the reaction restraining agent is a Mn compound, manganese sulfate may be used in step S6; when the reaction restraining agent is a Zr compound, zirconium nitrate or zirconium oxychloride may be used in step S6; when the reaction restraining agent is a Mo compound, sodium molybdate may be used in step S6; and when the reaction restraining agent is a La compound, lanthanum nitrate may be used in step S6.

[0048] Step S7: Stop the reaction, and centrifuge, filter, wash, dry, and sieve the slurry in the reaction container to obtain precursor particles.

[0049] In step S7, the drying temperature is controlled to not exceed 200°C. The precursor particles obtained by this method are made of nickel-cobalt-manganese hydroxide. If nickel-cobalt-manganese oxide is to be obtained, the drying temperature can be controlled to reach 400-500°C to dehydrate the nickel-cobalt-manganese hydroxide and convert it into nickel-cobalt-manganese oxide.

[0050] The present application also provides a method for preparing a positive electrode active material, which includes the following steps 1 to 3.

[0051] Step 1: Mix the precursor of the positive electrode active material, lithium source, and additives, and perform a sintering process. The sintering temperature range is 600-950° C., and the atmosphere is air or high-purity oxygen atmosphere.

[0052] Step 2: The product of the primary sintering is mixed with an active inhibitor and subjected to secondary sintering. The temperature range of the secondary sintering is 300-850° C., and the atmosphere is a high-purity oxygen atmosphere.

[0053] Step 3: The product of the secondary sintering and the nano-coating are subjected to a third sintering, wherein the temperature range of the third sintering is 300-850° C. and the atmosphere is a high-purity oxygen atmosphere.

[0054] In step 1, the precursor, lithium source and additive are prepared in a certain proportion, and the additive is a high-valent structural stabilizing additive. During the high-temperature process of primary sintering, the lithium source and additive penetrate into the interior of the precursor particles. The inner core develops preferentially due to the presence of flux to form crystal seeds, and the outer shell develops to a lower degree due to the presence of reaction-constraining elements. The lithium source can be lithium hydroxide, lithium carbonate, lithium nitrate, etc., but is not limited thereto. In some embodiments, the precursor, lithium source, and additive are in a molar ratio of 1: (1.02-1.06): (0.001-0.01).

[0055] In step 2, after the product of the primary sintering is cooled, an active inhibitor is added and mixed at high speed. A secondary high-temperature sintering is performed, and the sintering temperature is higher than the sintering temperature of step 1. The outer shell of the precursor forms a layered ternary oxide under a solid-phase reaction. Since a layer of active inhibitor is coated on the outside, the active inhibitor is used to reduce the surface energy of the material. Under the influence of the surface energy of the inner core, the elements of the outer shell cause each precursor particle to gradually develop into a single single crystal ternary material. The active inhibitor is selected from one or more of B2O3, V2O5, V2O4, Bi2O3, MnO2, MoO3, LaNO3, La2O, and NbNO3. In some embodiments, the product of step 1 is mixed with the active inhibitor in a mass ratio of 1: (0.0005-0.01).

[0056] In step 3, after cooling, the product from step 2 is mixed with a nano-coating that inhibits reaction with the electrolyte and improves the kinetics of the material interface reaction. The mixture is then sintered three times at low temperatures in an oxygen atmosphere to produce a highly dispersed, spherical, composite-modified ternary cathode material. The nano-coating can be nano-alumina, titanium oxide, aluminum hydroxide, aluminum oxyhydroxide, tungsten oxide, or the like. In some embodiments, the product from step 2 is mixed with the nano-coating at a mass ratio of 1:(0.001-0.02).

[0057] The present application also provides a positive electrode active material, which is prepared using the above-mentioned method for preparing the positive electrode active material.

[0058] The precursor particles of this application have a flux concentration gradient in the core and a reaction-constraining agent concentration gradient in the shell, which allows subsequent precursor crystallization to develop from the inside out, with better and more complete crystallization occurring closer to the center of the core. High-valent cations are added to the shell as reaction-constraining agents, inhibiting precursor crystallization and ion migration, resulting in a significant difference in the critical reaction temperatures between the core and shell.

[0059] Adding an activity inhibitor during secondary sintering reduces surface energy, inhibiting ion migration between adjacent precursors that leads to secondary crystallization. The core-shell surface energy is higher than the interparticle surface energy, leading to inward-directed particle growth. This precursor structure, combined with an activity inhibitor during secondary sintering, yields highly dispersed, spherical, single-crystal ternary cathode active materials.

[0060] The present application also provides a positive electrode, which includes a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material prepared by the above preparation method.

[0061] The positive electrode active material layer includes not only the positive electrode active material but also a conductive agent, a binder, and the like.

[0062] The present application also provides a lithium-ion battery, comprising a positive electrode, a separator, and a negative electrode stacked in sequence, wherein the positive electrode is the positive electrode described above.

[0063] The following is a detailed description through Examples 1 to 5.

[0064] Example 1

[0065] (1) The main materials for precursor synthesis are nickel sulfate, cobalt sulfate, and manganese sulfate, which are mixed in a nickel-cobalt-manganese metal molar ratio of 8:1:1, and deionized water is added and stirred to prepare a salt solution with a salt concentration of 2.0 mol / L.

[0066] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution and add it to the reactor. Add an appropriate amount of deionized water and stir evenly. Adjust the pH ratio to 11.75. Add ammonia water to control the ammonia concentration to 4 g / L. Maintain the solution temperature at 40°C. During this period, continuously introduce nitrogen as a protective gas.

[0067] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 4 L / h, the reactor was stirred at a frequency of 40 Hz, ammonia water was continuously added as a complexing agent, nitrogen was introduced, the pH value of the reaction system was maintained stable at 11.50, and at the same time, 1 mol / L magnesium sulfate solution was introduced at a flow rate of 0.1 L / h to carry out a coprecipitation reaction; an appropriate amount of slurry was taken from the reactor every 2 hours, and the slurry was centrifuged, filtered, washed, dried, and sieved to obtain a dried material, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0068] (4) When the precursor D50 grows horizontally to 1.5 μm, the rate of magnesium sulfate introduction is reduced by 0.02 L / h until it stops, thereby obtaining a precursor core with gradient Mg doping and a core D50 of 1.7 μm.

[0069] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 8 L / h, and the stirring frequency was maintained at 40 Hz. The pH value of the solution in the reactor was adjusted to 11.0. At the same time, 2 mol / L ammonium tungstate solution was added at an initial rate of 0.02 L / h. The rate was increased by 0.03 L / h every hour until it reached 0.2 L / h and then stopped increasing. Every 2 hours, an appropriate amount of slurry was taken from the reactor, centrifuged, filtered, washed, dried, and sieved to obtain a dried material. The particle size data of the dried material was tested using a Malvern particle size tester.

[0070] (6) When the D50 of the precursor is 2.0 μm, the reaction is stopped. The slurry in the reactor is centrifuged, filtered, washed, dried, and sieved to obtain a ternary precursor with a special structure and a double gradient element concentration distribution. Tungsten exists in the form of tungstate in the shell.

[0071] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at high speed, put into a sagger, placed in a muffle furnace, introduced with oxygen, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 820°C for 8 hours, and then taken out of the furnace after cooling.

[0072] (8) The above materials were mixed with nano-vanadium pentoxide in a mass ratio of 1:0.005, loaded into a sagger, placed in a muffle furnace, and oxygen was introduced to control the oxygen concentration in the furnace to reach 95%. The mixture was sintered at a high temperature of 880°C for 10 hours, and then removed from the furnace after cooling. A mechanical crusher was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0073] (9) The above materials were mixed with nano-alumina at a mass ratio of 1:0.003 at high speed, placed in a sagger, and placed in a muffle furnace. Oxygen was introduced to control the oxygen concentration in the furnace to 85%. The mixture was sintered at 600°C for 10 hours and then removed from the furnace after cooling. A highly dispersed single crystal NCM811 ternary material was obtained.

[0074] The scanning electron microscope image of the NCM811 ternary material is shown in Figure 2, and the X-ray diffraction pattern is shown in Figure 3. As shown in Figure 2, the single crystal particles of the NCM811 ternary material are clearly dispersed and have a high degree of single crystal characteristics. As shown in Figure 3, the diffraction peaks are sharp, and the (018)(110) peaks are clearly split, indicating that the material has the typical layered characteristics of a cathode material.

[0075] (10) Screening single crystal NCM811 ternary material, after screening, uniformly mixing it with binder (PVDF) and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly spreading the slurry on aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain positive electrode sheets; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring it to a glove box; in the glove box, making button batteries together with lithium sheets, gaskets, positive electrode shells, polypropylene diaphragms, and 1 mol / L lithium hexafluorophosphate electrolyte.

[0076] Example 2

[0077] (1) The main materials for precursor synthesis are nickel sulfate, cobalt sulfate, and manganese sulfate, which are mixed in a nickel-cobalt-manganese metal molar ratio of 8:1:1, and deionized water is added and stirred to prepare a salt solution with a salt concentration of 2.0 mol / L.

[0078] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution and add it to the reactor. Add an appropriate amount of deionized water and stir evenly. Adjust the pH ratio to 12.00. Add ammonia water to control the ammonia concentration to 2 g / L. Maintain the solution temperature at 40°C. During this period, continuously introduce nitrogen as a protective gas.

[0079] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h, the reactor was stirred at a frequency of 40 Hz, ammonia water was continuously added as a complexing agent, nitrogen was introduced, the pH value of the reaction system was maintained stable at 11.50, and at the same time, 1 mol / L magnesium sulfate solution was introduced at a flow rate of 0.07 L / h to carry out a coprecipitation reaction; an appropriate amount of slurry was taken from the reactor every 2 hours, and the slurry was centrifuged, filtered, washed, dried, and sieved to obtain a dried material, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0080] (4) When the precursor D50 grows horizontally to 1.5 μm, the rate of magnesium sulfate introduction is reduced by 0.01 L / h until it stops. This results in a gradient-doped Mg precursor core with a D50 of 1.7 μm. Magnesium exists in the core as magnesium hydroxide.

[0081] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 7 L / h, and the stirring frequency was maintained at 40 Hz. The pH value of the reactor solution was adjusted to 11.0, and 2 mol / L aluminum nitrate solution was added at the same time. The initial addition rate was 0.02 L / h, and the rate was increased by 0.02 L / h every hour until it reached 0.12 L / h and then stopped increasing. Every 2 hours, an appropriate amount of slurry was taken from the reactor, centrifuged, filtered, washed, dried, and sieved to obtain a dried material. The particle size data of the dried material was tested using a Malvern particle size tester.

[0082] (6) When the D50 of the precursor is 2.0 μm, the reaction is stopped. The slurry in the reactor is centrifuged, filtered, washed, dried, and sieved to obtain a ternary precursor with a special structure and a double gradient element concentration distribution, in which aluminum exists in the form of aluminum hydroxide in the shell.

[0083] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at high speed, placed in a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 810°C for 8 hours and then removed from the furnace after cooling.

[0084] (8) The above materials were mixed with nano-vanadium pentoxide in a mass ratio of 1:0.001, loaded into a sagger, placed in a muffle furnace, introduced with oxygen, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 870°C for 10 hours, and then removed from the furnace after cooling. A mechanical crusher was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0085] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.004 at high speed, placed in a sagger, and placed in a muffle furnace. Oxygen was introduced to control the oxygen concentration in the furnace to 80%. The mixture was sintered at 450°C for 10 hours and then removed from the furnace after cooling. A highly dispersed single-crystal NCM811 ternary material was obtained.

[0086] The scanning electron microscope image of the single crystal NCM811 ternary material is shown in Figure 4, and the X-ray diffraction pattern is shown in Figure 5. As shown in Figure 4, the single crystal particles of the NCM811 ternary material are clearly dispersed and have a high degree of single crystal characteristics. As shown in Figure 5, the diffraction peaks are sharp, and the (018)(110) peaks are clearly split, indicating that the material has the typical layered characteristics of a cathode material.

[0087] (10) Screening single crystal NCM811 ternary material, after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly spreading the slurry on aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain positive electrode sheets; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring it to a glove box; in the glove box, making button batteries together with lithium sheets, gaskets, positive electrode shells, polypropylene diaphragms, and 1 mol / L lithium hexafluorophosphate electrolyte.

[0088] Example 3

[0089] (1) The main materials for precursor synthesis are nickel sulfate, cobalt sulfate, and manganese sulfate, which are mixed in a nickel-cobalt-manganese metal molar ratio of 8:1:1, and deionized water is added and stirred to prepare a salt solution with a salt concentration of 2.0 mol / L.

[0090] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution and add it to the reactor. Add an appropriate amount of deionized water and stir evenly. Adjust the pH ratio to 12.00. Add ammonia water to control the ammonia concentration to 2 g / L. Maintain the solution temperature at 40°C. During this period, continuously introduce nitrogen as a protective gas.

[0091] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h, the reactor was stirred at a frequency of 40 Hz, ammonia water was continuously added as a complexing agent, nitrogen was introduced, the pH value of the reaction system was maintained stable at 11.70, and at the same time, 1 mol / L zirconium oxychloride solution was introduced at a flow rate of 0.07 L / h to carry out a coprecipitation reaction; an appropriate amount of slurry was taken from the reactor every 2 hours, and the slurry was centrifuged, filtered, washed, dried, and sieved to obtain a dried material, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0092] (4) When the precursor D50 grows horizontally to 1.5 μm, the rate of introduction of zirconium oxychloride is reduced by 0.01 L / h until it stops. This results in a precursor core with a gradient doping of Zr, with a core D50 of 1.7 μm, in which zirconium exists in the form of zirconium hydroxide.

[0093] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 7 L / h, and the stirring frequency was maintained at 40 Hz. The pH value of the solution in the reactor was adjusted to 11.0, and 2 mol / L aluminum nitrate solution was added at the same time. The initial addition rate was 0.1 L / h, and the rate was increased by 0.1 L / h every hour until it reached 0.7 L / h and then no longer increased. Every 2 hours, an appropriate amount of slurry was taken from the reactor, centrifuged, filtered, washed, dried, and sieved to obtain a dried material. The particle size data of the dried material was tested using a Malvern particle size tester.

[0094] (6) When the D50 of the precursor is 2.0 μm, the reaction is stopped. The slurry in the reactor is centrifuged, filtered, washed, dried, and sieved to obtain a ternary precursor with a special structure and a double gradient element concentration distribution, in which aluminum exists in the form of aluminum hydroxide in the shell.

[0095] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at high speed, placed in a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 810°C for 8 hours and then removed from the furnace after cooling.

[0096] (8) The above materials were mixed with nano-vanadium pentoxide in a mass ratio of 1:0.001, loaded into a sagger, placed in a muffle furnace, introduced with oxygen, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 870°C for 10 hours, and then removed from the furnace after cooling. A mechanical crusher was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0097] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.002 at high speed, placed in a sagger, and placed in a muffle furnace. Oxygen was introduced to control the oxygen concentration in the furnace to 80%. The mixture was sintered at a constant temperature of 450°C for 10 hours and then removed from the furnace after cooling. A highly dispersed single crystal NCM811 ternary material was obtained.

[0098] (10) Screening single crystal NCM811 ternary material, after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly spreading the slurry on aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain positive electrode sheets; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring it to a glove box; in the glove box, making button batteries together with lithium sheets, gaskets, positive electrode shells, polypropylene diaphragms, and 1 mol / L lithium hexafluorophosphate electrolyte.

[0099] Example 4

[0100] (1) The main materials for precursor synthesis are nickel sulfate, cobalt sulfate, and manganese sulfate, which are mixed in a nickel-cobalt-manganese metal molar ratio of 8:1:1, and deionized water is added and stirred to prepare a salt solution with a salt concentration of 2.0 mol / L.

[0101] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution and add it to the reactor. Add an appropriate amount of deionized water and stir evenly. Adjust the pH ratio to 12.00. Add ammonia water to control the ammonia concentration to 2 g / L. Maintain the solution temperature at 40°C. During this period, continuously introduce nitrogen as a protective gas.

[0102] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h, the reactor was stirred at a frequency of 40 Hz, ammonia water was continuously added as a complexing agent, nitrogen was introduced, the pH value of the reaction system was maintained stable at 11.50, and at the same time, 1 mol / L zirconium oxychloride solution was introduced at a flow rate of 0.07 L / h to carry out a coprecipitation reaction; an appropriate amount of slurry was taken from the reactor every 2 hours, and the slurry was centrifuged, filtered, washed, dried, and sieved to obtain a dried material, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0103] (4) When the precursor D50 grows horizontally to 1.4 μm, the rate of introduction of zirconium oxychloride is reduced by 0.01 L / h until it stops. This results in a precursor core with a gradient doping of Zr, with a core D50 of 1.6 μm, in which zirconium exists in the form of zirconium hydroxide.

[0104] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 7 L / h, and the stirring frequency was maintained at 40 Hz. The pH value of the solution in the reactor was adjusted to 11.0. At the same time, 1 mol / L sodium tungstate solution was added. The initial addition rate was 0.1 L / h, and the rate was increased by 0.1 L / h every hour until it reached 1.0 L / h and then no longer increased. Every 2 hours, an appropriate amount of slurry was taken from the reactor, centrifuged, filtered, washed, dried, and sieved to obtain a dried material. The particle size data of the dried material was tested using a Malvern particle size tester.

[0105] (6) When the D50 of the precursor is 1.9 μm, the reaction is stopped. The slurry in the reactor is centrifuged, filtered, washed, dried, and sieved to obtain a ternary precursor with a special structure and a double gradient element concentration distribution. Tungsten exists in the form of tungstate in the shell.

[0106] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at high speed, placed in a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 810°C for 8 hours and then removed from the furnace after cooling.

[0107] (8) The above materials were mixed with nano-B2O3 in a mass ratio of 1:0.002, loaded into a sagger, placed in a muffle furnace, and oxygen was introduced to control the oxygen concentration in the furnace to reach 95%. The mixture was sintered at a high temperature of 870°C for 10 hours, and then removed from the furnace after cooling. A mechanical crusher was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0108] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.002 at high speed, placed in a sagger, and placed in a muffle furnace. Oxygen was introduced to control the oxygen concentration in the furnace to 80%. The mixture was sintered at a constant temperature of 450°C for 10 hours and then removed from the furnace after cooling. A highly dispersed single crystal NCM811 ternary material was obtained.

[0109] (10) Screening single crystal NCM811 ternary material, after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly spreading the slurry on aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain positive electrode sheets; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring it to a glove box; in the glove box, making button batteries together with lithium sheets, gaskets, positive electrode shells, polypropylene diaphragms, and 1 mol / L lithium hexafluorophosphate electrolyte.

[0110] Example 5

[0111] (1) The main materials for precursor synthesis are nickel sulfate, cobalt sulfate, and manganese sulfate, which are mixed in a nickel-cobalt-manganese metal molar ratio of 8:1:1, and deionized water is added and stirred to prepare a salt solution with a salt concentration of 2.0 mol / L.

[0112] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution and add it to the reactor. Add an appropriate amount of deionized water and stir evenly. Adjust the pH ratio to 12.00. Add ammonia water to control the ammonia concentration to 2 g / L. Maintain the solution temperature at 40°C. During this period, continuously introduce nitrogen as a protective gas.

[0113] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h, the reactor was stirred at a frequency of 40 Hz, ammonia water was continuously added as a complexing agent, nitrogen was introduced, the pH value of the reaction system was maintained stable at 11.50, and at the same time, 1 mol / L zirconium oxychloride solution was introduced at a flow rate of 0.07 L / h to carry out a coprecipitation reaction; an appropriate amount of slurry was taken from the reactor every 2 hours, and the slurry was centrifuged, filtered, washed, dried, and sieved to obtain a dried material, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0114] (4) When the precursor D50 grows horizontally to 1.4 μm, the rate of introduction of zirconium oxychloride is reduced by 0.01 L / h until it stops. This results in a precursor core with a gradient doping of Zr, with a core D50 of 1.6 μm, in which zirconium exists in the form of zirconium hydroxide.

[0115] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 6 L / h, and the stirring frequency was maintained at 40 Hz. The pH value of the solution in the reactor was adjusted to 11.0, and 2 mol / L sodium molybdate solution was added at the same time. The initial addition rate was 0.08 L / h, and the rate was increased by 0.02 L / h every hour until it reached 0.24 L / h and then stopped increasing. Every 2 hours, an appropriate amount of slurry was taken from the reactor, centrifuged, filtered, washed, dried, and sieved to obtain a dried material. The particle size data of the dried material was tested using a Malvern particle size tester.

[0116] (6) When the D50 of the precursor is 1.9 μm, the reaction is stopped. The slurry in the reactor is centrifuged, filtered, washed, dried, and sieved to obtain a ternary precursor with a special structure and a double gradient concentration element distribution.

[0117] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at high speed, placed in a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at a high temperature of 810°C for 8 hours and then removed from the furnace after cooling.

[0118] (8) The above materials were mixed with nano-B2O3 at a mass ratio of 1:0.003, loaded into a sagger, placed in a muffle furnace, and oxygen was introduced to control the oxygen concentration in the furnace to reach 95%. The mixture was sintered at a high temperature of 870°C for 10 hours, and then removed from the furnace after cooling. A mechanical crusher was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0119] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.0015 at high speed, placed in a sagger, and placed in a muffle furnace. Oxygen was introduced to control the oxygen concentration in the furnace to 80%. The mixture was sintered at a constant temperature of 450°C for 10 hours and then removed from the furnace after cooling. A highly dispersed single crystal NCM811 ternary material was obtained.

[0120] (10) Screening single crystal NCM811 ternary material, after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly spreading the slurry on aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain positive electrode sheets; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring it to a glove box; in the glove box, making button batteries together with lithium sheets, gaskets, positive electrode shells, polypropylene diaphragms, and 1 mol / L lithium hexafluorophosphate electrolyte.

[0121] Performance testing:

[0122] The button cells of Examples 1 to 5 were evaluated for electrical performance using a Wuhan Blue Power Battery Testing System (Model: CT3001A). Discharge capacity was measured by charge-discharge testing at a voltage of 3.0 to 4.30 V at a 0.1C rate. Capacity retention after 50 cycles was measured by cyclic charge-discharge testing at a 0.1C rate at room temperature. The test results for Examples 1 to 5 are shown in the table below.

[0123] According to the test results of Examples 1 to 5, it can be seen that the battery made of the positive electrode active material prepared using the precursor of the present application has better performance.

[0124] It should be noted that the above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application; the embodiments of the present application and the features of the embodiments can be combined with each other unless there is a conflict. Therefore, the scope of protection of the present application shall be based on the scope of protection of the claims.

Claims

1. A precursor of a positive electrode active material, wherein the precursor particles include a core and a shell covering the core, characterized in that: The materials of the core and the shell are both nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide, and the chemical formula of nickel-cobalt-manganese hydroxide is Ni x Co y Mn z (OH)2, the chemical formula of nickel-cobalt-manganese oxide is Ni x Co y Mn z O, where 0.33≤x≤1.0, 0≤y≤0.33, x+y+z=1; The core is doped with a flux, and the flux is selected from one or more of oxides, carbonate compounds, and hydroxides of Sr, Li, Mg, Ni, Co, and Zr; The shell is doped with a reaction restraining agent, and the reaction restraining agent is selected from one or more compounds such as lithium compounds, oxides, carbonate compounds, hydroxides, etc. of Ta, W, Al, Mn, Mo, and La.

2. The precursor of the positive electrode active material according to claim 1, characterized in that: Along the direction from the center of the core to the shell, the concentration of the flux gradually decreases, and the concentration of the reaction confinement agent gradually increases.

3. The precursor of the positive electrode active material according to claim 1, characterized in that: The weight of the flux is 100-2000 ppm of the weight of the precursor; the weight of the reaction restraining agent is 100-4000 ppm of the weight of the precursor.

4. The precursor of the positive electrode active material according to claim 1, characterized in that: The outer diameter of the precursor particles ranges from 3.0 to 8.0 μm.

5. The precursor of the positive electrode active material according to claim 1, characterized in that: The specific surface area of ​​the precursor particles is 5 to 50 m 2 / g.

6. The precursor of the positive electrode active material according to claim 1, characterized in that: The diameter of the core is greater than or equal to 1.3 μm.

7. A method for preparing a positive electrode active material, characterized in that: include: The precursor of the positive electrode active material and the lithium source according to any one of claims 1 to 6 are subjected to a primary sintering, wherein the primary sintering temperature ranges from 600 to 950° C. and the atmosphere is air or a high-purity oxygen atmosphere; The product of the primary sintering is mixed with an active inhibitor and subjected to secondary sintering, wherein the temperature range of the secondary sintering is 300 to 850° C. and the atmosphere is a high-purity oxygen atmosphere; The product of the secondary sintering is mixed with a nano-coating material capable of inhibiting reaction with an electrolyte and improving the kinetics of a material interface reaction, and then sintered for a third time. The temperature range of the third sintering is 300-850° C., and the atmosphere is a high-purity oxygen atmosphere.

8. The method for preparing the positive electrode active material according to claim 7, characterized in that: The active inhibitor is one or more of B2O3, V2O5, V2O4, Bi2O3, MnO2, MoO3, LaNO3, La2O, and NbNO3; the mass ratio of the product of the primary sintering to the active inhibitor is 1:(0.0005-0.01).

9. The method for preparing a positive electrode active material according to claim 7, characterized in that: The nano coating is selected from at least one of nano aluminum oxide, titanium oxide, aluminum hydroxide, aluminum hydroxide, and tungsten oxide. The mass ratio of the secondary sintered product to the nano coating is 1:(0.001-0.02).

10. A positive electrode active material, characterized in that: The method according to claim 7 is used to prepare the product.

11. A positive electrode, characterized in that: The positive electrode comprises a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, and the positive electrode active material layer comprises the positive electrode active material prepared by the preparation method according to claim 7.

12. A lithium ion battery comprising a positive electrode, a separator, and a negative electrode stacked in sequence, characterized in that: The positive electrode is the positive electrode as claimed in claim 11.

13. A method for preparing a precursor of a positive electrode active material according to any one of claims 1 to 6, characterized in that: include: Add water to nickel salt, cobalt salt and manganese salt and mix them evenly to obtain solution I; Adding precipitated alkali solution into the reaction vessel; Continuously introducing the solution I and the complexing agent solution into the reaction container to react and generate precursor particles; Adding a flux metal salt solution into the reaction container, wherein the flux metal salt solution is at least one of Sr salt, Li salt, Mg salt, Ni salt, Co salt, and Zr salt; When the precursor particles grow to 1.2-1.6 μm, gradually reducing the rate at which the flux metal salt solution is added to the reaction container until it stops; Adding a reaction restraining agent metal salt solution into the reaction container, and gradually increasing the speed of dripping the reaction restraining agent metal salt solution into the reaction container, wherein the reaction restraining agent metal salt solution comprises at least one of Ta oxide, W salt, Al salt, Mn salt, Mo salt, and La salt; The reaction is stopped, and the slurry in the reaction container is centrifuged, filtered, washed, dried, and sieved to obtain precursor particles.

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