Preparation method of modified positive electrode material, modified positive electrode material and application

Abstract

The invention provides a preparation method of a modified positive electrode material, the modified positive electrode material and application. The preparation method comprises the following steps: (1) adding a nickel-cobalt-manganese main metal salt solution, a dopant solution, a precipitator solution and a complexing agent solution in a parallel flow manner, and sequentially carrying out a nucleation coprecipitation reaction, a main growth coprecipitation reaction and a stable growth coprecipitation reaction to obtain a precursor; (2) mixing the precursor with a lithium source, and performing first sintering to obtain a first sintered product; and (3) carrying out coating treatment on the primary sintering product by using a coating material through a magnetron sputtering method to obtain the modified positive electrode material, first protective gas is introduced in the nucleation reaction process, and first air and second protective gas are introduced in the main growth reaction process; second air and third protective gas are introduced in the stable growth reaction process; the flow ratio of the first air to the second protective gas is greater than the flow ratio of the second air to the third protective gas. The modified positive electrode material with excellent physical and chemical properties and electrochemical properties is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries and relates to a preparation method of a modified positive electrode material, the modified positive electrode material and applications. Background Art

[0002] With the booming market for portable electronics, lithium-ion batteries (LIBs) have entered a golden age in the past decade. The next generation of LIBs is expected to be more stable, safer, and have higher energy density to meet the growing demand. With the continuous expansion of application areas, higher requirements are placed on the energy density, rate performance, and cycle performance of lithium-ion batteries. The current methods to improve energy density mainly include increasing the specific capacity of the positive electrode material, and have gradually shifted from lithium iron phosphate to lithium nickel cobalt manganese oxide positive electrode materials, lithium nickel cobalt aluminum oxide positive electrode materials, and lithium-rich manganese-based positive electrode materials. However, due to the poor conductivity and high internal resistance of lithium nickel cobalt manganese oxide positive electrode materials, they will eventually affect the rate performance and cycle performance of lithium-ion batteries.

[0003] To address these issues, surface coating of electrode materials has been widely used. Generally, the interfacial dynamics and electrochemical performance of surface-coated electrodes are highly sensitive to two factors: i) the coating method and ii) the nature and amount of the coating material. Two main coating methods are commonly used in the literature, each of which affects the electrode kinetics during cycling. In most studies, "powder coating" methods are employed, typically through mechanical mixing, solution coating, and vapor deposition. With these methods, the entire powder of the active material is coated with a specific material before fabricating the composite electrode.

[0004] However, the traditional surface coating and lattice ion doping modification technology cannot effectively solve the problem of layered particles in nickel-rich NCM materials. + The high anisotropy of diffusion and lattice expansion / contraction, and morphology modulation will be an effective way to improve their rate performance and cycling stability. However, the structure and morphology controlled synthesis of NCM materials with superior rate and cycling performance remains a huge challenge, especially in a large-scale mass production environment. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a method for preparing a modified cathode material, a modified cathode material, and its use. By limiting the flow ratio of air and protective gas during the different stages of the coprecipitation reaction, and synergistically combining magnetron sputtering with coating of the sintered material, the present invention produces a modified cathode material with excellent physical, chemical, and electrochemical properties.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a modified positive electrode material, the preparation method comprising the following steps:

[0008] (1) adding a nickel-cobalt-manganese main metal salt solution, a dopant solution, a precipitant solution, and a complexing agent solution in parallel, and sequentially performing a nucleation coprecipitation reaction, a main growth coprecipitation reaction, and a stable growth coprecipitation reaction to obtain a positive electrode precursor material;

[0009] (2) mixing the positive electrode precursor material and the lithium source, and first sintering to obtain a sintered product;

[0010] (3) coating the calcined product with a coating material by magnetron sputtering to obtain the modified positive electrode material;

[0011] Wherein, in step (1), the first protective gas is introduced during the nucleation co-precipitation reaction, the first air and the second protective gas are introduced during the main growth co-precipitation reaction; and the second air and the third protective gas are introduced during the stable growth co-precipitation reaction;

[0012] The flow rate ratio of the first air to the second protective gas is greater than the flow rate ratio of the second air to the third protective gas.

[0013] In the preparation method of the present invention, during the positive electrode precursor preparation stage, the type of gas introduced and the relative size of the gas flow rate are regulated, which not only achieves uniform doping of the doping elements, but also adjusts the particle morphology of the positive electrode precursor material, thereby obtaining a loose and porous positive electrode precursor material with excellent physical and chemical properties; the coating obtained by synergistically adopting a specific magnetron sputtering stabilizes the crystal structure, suppresses lithium-nickel mixing, and improves the capacity, rate and cycle performance of the modified positive electrode material; and the process is simple, repeatable, and consistent, and large-scale mass production can be achieved.

[0014] During the preparation stage of the positive electrode precursor, only protective gas is introduced during the nucleation process to achieve the formation of an inner core with a dense structure; on this basis, gas is introduced during the main growth stage to increase the specific surface area of ​​the material; further, the air flow rate is increased during the stable growth stage to ensure that the flow rate ratio of the first air to the second protective gas is greater than the flow rate ratio of the second air to the third protective gas, thereby obtaining a structure with a loose outside and a dense inside that grows uniformly along the radial direction.

[0015] Through surface sputtering, the target material can be evenly coated on all the powders of the sintered product. If the coating material is electrically insulating, the risk of the electron blocking effect of the coating material can also be reduced. The process is more economical, environmentally friendly and controllable, so as to solve the problems in the existing positive electrode material preparation methods, such as the unstable electrochemical properties of the coating layer such as cycle life and rate characteristics, as well as the cumbersome process parameter control, unsatisfactory repeatability and consistency, which make it difficult to achieve mass production.

[0016] Therefore, the present invention can effectively curb the corrosion of the electrolyte, accelerate the rapid transmission of lithium ions, and promote the further release of electrochemical properties through the coordinated cooperation of the positive electrode precursor preparation process and the magnetron sputtering coating method.

[0017] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0018] Preferably, the doping element in the dopant solution in step (1) includes any one or a combination of at least two of aluminum, titanium, niobium, zirconium, tungsten, vanadium, strontium, gallium, cerium, yttrium, lanthanum or antimony, preferably yttrium.

[0019] During the preparation of the cathode precursor, yttrium doping is preferably performed through different reaction stages and gas regulation. Yttrium (Y) penetrates into the crystal lattice, replacing some transition metal elements and forming more stable chemical bonds with oxygen. This stabilizes the crystal structure, inhibits Li-Ni mixing, and improves safety during the electrochemical reaction. It also improves the interlayer spacing of metal ions, shortening the distance for lithium ion transmission and improving the material's rate performance.

[0020] Preferably, in the parallel addition process of step (1), the molar amount of the doping element in the dopant solution is 0.05% to 5%, based on the total molar amount of the nickel-cobalt-manganese mixed salt solution as 100%, for example, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., preferably 0.2% to 1%.

[0021] In the present invention, the molar ratio of the doping element in the dopant solution is regulated to be 0.05% to 5%, which is beneficial to expanding the interaxial distance and promoting further diffusion of lithium ions; and is further preferably 0.2% to 1%, which better improves the rate performance of the material and stabilizes the crystal structure.

[0022] Preferably, in step (1), the flow rate of the nickel-cobalt-manganese main metal salt solution during the nucleation co-precipitation reaction is less than the flow rate of the nickel-cobalt-manganese main metal salt solution during the main growth co-precipitation reaction, which is less than the flow rate of the nickel-cobalt-manganese main metal salt solution during the stable growth co-precipitation reaction.

[0023] Preferably, in step (1), the flow rate of the dopant solution during the nucleation co-precipitation reaction is less than the flow rate of the dopant solution during the main growth co-precipitation reaction and less than the flow rate of the dopant solution during the stable growth co-precipitation reaction.

[0024] Preferably, in step (1), the flow rate of the precipitant solution during the nucleation co-precipitation reaction is less than the flow rate of the precipitant solution during the main growth co-precipitation reaction and less than the flow rate of the precipitant solution during the stable growth co-precipitation reaction.

[0025] Preferably, in step (1), the flow rate of the complexing agent solution during the nucleation co-precipitation reaction is less than the flow rate of the complexing agent solution during the main growth co-precipitation reaction and less than the flow rate of the complexing agent solution during the stable growth co-precipitation reaction.

[0026] During the preparation of the positive electrode precursor, the present invention sequentially increases the flow rate of each raw material from the nucleation co-precipitation reaction, the main growth co-precipitation reaction to the stable growth co-precipitation reaction, thereby better improving the uniformity of the particles during the growth process, while shortening the reaction time and reducing costs.

[0027] Preferably, during the nucleation coprecipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution is 6 to 8 L / h, the flow rate of the dopant solution is 100 to 300 mL / h, the flow rate of the precipitant solution is 2.4 to 3 L / h, and the flow rate of the complexing agent solution is 700 to 1000 mL / h.

[0028] For example:

[0029] During the nucleation coprecipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution can be 6 L / h, 6.5 L / h, 7 L / h, 7.5 L / h or 8 L / h, etc.

[0030] During the nucleation coprecipitation reaction in step (1), the flow rate of the dopant solution can be 100 mL / h, 125 mL / h, 150 mL / h, 175 mL / h, 200 mL / h, 225 mL / h, 250 mL / h, 275 mL / h or 300 mL / h, etc.

[0031] During the nucleation co-precipitation reaction in step (1), the flow rate of the precipitant solution can be 2.4 L / h, 2.5 L / h, 2.6 L / h, 2.7 L / h, 2.8 L / h, 2.9 L / h or 3 L / h, etc.

[0032] During the nucleation coprecipitation reaction in step (1), the flow rate of the complexing agent solution can be 700 mL / h, 750 mL / h, 800 mL / h, 850 mL / h, 900 mL / h, 950 mL / h or 1000 mL / h, etc.

[0033] Preferably, during the main growth co-precipitation reaction process in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution is 10 to 15 L / h, the flow rate of the dopant solution is 200 to 500 mL / h, the flow rate of the precipitant solution is 3.5 to 4.5 L / h, and the flow rate of the complexing agent solution is 1 to 1.5 L / h.

[0034] For example:

[0035] During the main growth co-precipitation reaction process in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution can be 10 L / h, 11 L / h, 12 L / h, 13 L / h, 14 L / h or 15 L / h, etc.

[0036] During the main growth co-precipitation reaction process in step (1), the flow rate of the dopant solution can be 200 mL / h, 225 mL / h, 250 mL / h, 275 mL / h, 300 mL / h, 325 mL / h, 350 mL / h, 375 mL / h, 400 mL / h, 425 mL / h, 450 mL / h, 475 mL / h or 500 mL / h, etc.

[0037] During the main growth co-precipitation reaction process in step (1), the flow rate of the precipitant solution can be 3.5 L / h, 3.6 L / h, 3.7 L / h, 3.8 L / h, 3.9 L / h, 4 L / h, 4.1 L / h, 4.2 L / h, 4.3 L / h, 4.4 L / h or 4.5 L / h, etc.

[0038] During the main growth co-precipitation reaction in step (1), the flow rate of the complexing agent solution can be 1 L / h, 1.1 L / h, 1.2 L / h, 1.3 L / h, 1.4 L / h or 1.5 L / h, etc.

[0039] Preferably, during the stable growth co-precipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution is 20 to 30 L / h, the flow rate of the dopant solution is 500 to 800 mL / h, the flow rate of the precipitant solution is 7 to 8 L / h, and the flow rate of the complexing agent solution is 2 to 2.5 L / h.

[0040] For example:

[0041] During the stable growth co-precipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution can be 20 L / h, 21 L / h, 22 L / h, 23 L / h, 24 L / h, 25 L / h, 26 L / h, 27 L / h, 28 L / h, 29 L / h or 30 L / h, etc.

[0042] During the stable growth coprecipitation reaction process in step (1), the flow rate of the dopant solution can be 500 mL / h, 525 mL / h, 550 mL / h, 575 mL / h, 600 mL / h, 625 mL / h, 650 mL / h, 675 mL / h, 700 mL / h, 725 mL / h, 750 mL / h, 775 mL / h or 800 mL / h, etc.

[0043] During the stable growth co-precipitation reaction process in step (1), the flow rate of the precipitant solution can be 7 L / h, 7.1 L / h, 7.2 L / h, 7.3 L / h, 7.4 L / h, 7.5 L / h, 7.6 L / h, 7.7 L / h, 7.8 L / h, 7.9 L / h or 8 L / h, etc.

[0044] During the stable growth co-precipitation reaction in step (1), the flow rate of the dopant solution can be 2 L / h, 2.1 L / h, 2.2 L / h, 2.3 L / h, 2.4 L / h or 2.5 L / h, etc.

[0045] During the preparation of the positive electrode precursor, the flow rate of each raw material is regulated to increase successively with the reaction stage, and the specific numerical range of the flow rate of the raw materials in each co-precipitation reaction stage is further regulated, so as to better achieve uniform radial growth of primary particles.

[0046] Preferably, in the main growth co-precipitation reaction process of step (1), the flow ratio of the first air to the first protective gas is 0.2 to 0.5, for example, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5.

[0047] In the present invention, during the main growth co-precipitation reaction process in step (1), the flow ratio of the first air to the first protective gas is 0.2 to 0.5, which is more conducive to forming loose and densely arranged primary particles.

[0048] Preferably, in the stable growth co-precipitation reaction process of step (1), the flow rate ratio of the second air to the second protective gas is 0.1 to 0.2, for example, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.2, etc.

[0049] In the present invention, the stable growth coprecipitation reaction process of step (1) is regulated, and the flow ratio of the second air to the second protective gas is 0.1 to 0.2, which more effectively controls the reaction growth rate and forms a precursor with a dense interior and a loose exterior.

[0050] Preferably, the pH value of the nucleation coprecipitation reaction in step (1) is 11 to 11.5, for example, 11, 11.1, 11.2, 11.3, 11.4 or 11.5.

[0051] Preferably, the pH value of the main growth co-precipitation reaction in step (1) is 9.5-10, such as 9.5, 9.6, 9.7, 9.8, 9.9 or 10.

[0052] Preferably, the pH value of the stable growth co-precipitation reaction in step (1) is 10.2-11, for example, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.

[0053] Preferably, the median particle size D50 of the particles obtained by the nucleation co-precipitation reaction in step (1) is 3.5 to 4 μm, for example, 3.5 μm, 3.6, 3.7, 3.8, 3.9 or 4, etc.

[0054] It is understandable that, in the coprecipitation reaction process of step (1) of the present invention, the reaction temperature and the stirring speed are conventional technical solutions; the present invention is applicable to solutions that are reasonably known to those skilled in the art.

[0055] For example, the reaction temperature during the coprecipitation reaction can be 30 to 90° C., for example, 30° C., 40° C., 50° C., 60° C., 70° C., 80° C. or 90° C., and the stirring speed can be 150 to 600 rpm, for example, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 380 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm.

[0056] In addition, before the nickel-cobalt-manganese main metal salt solution, dopant solution, precipitant solution and complexing agent solution are added to the reaction vessel in parallel, a reaction base liquid can be added to the reaction vessel in advance. The present invention does not specifically limit the specific components of the reaction base liquid, and adaptive selection and adjustment can be made according to actual reaction requirements.

[0057] For example, the reaction base liquid includes water, a precipitant and a complexing agent, the temperature of the reaction base liquid is 50-80°C, for example, 50°C, 60°C, 70°C or 80°C, etc., the pH value of the reaction base liquid is 11-12, for example, 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9 or 12, etc.; the concentration of the complexing agent in the reaction base liquid is 4-12 g / L, for example, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L or 12 g / L, etc.

[0058] It should also be noted that the present invention does not specifically limit the specific salt types of the nickel, cobalt and manganese main metal salt solution and the dopant solution, as well as the specific substance types of the precipitant solution and the complexing agent solution. Those skilled in the art can make adaptive selections and adjustments based on actual needs.

[0059] Optionally, the specific salt types of the nickel, cobalt and manganese main metal salt solution and the dopant solution include at least one of sulfate, chloride, nitrate or acetate.

[0060] Optionally, the precipitating agent comprises sodium hydroxide and / or potassium hydroxide.

[0061] Optionally, the complexing agent includes aqueous ammonia.

[0062] Preferably, the median particle size D50 of the particles obtained by the main growth co-precipitation reaction in step (1) is 8 to 10 μm, for example, 8 μm, 8.3 μm, 8.5 μm, 8.8 μm, 9 μm, 9.3 μm, 9.5 μm, 9.8 μm or 10 μm, etc.

[0063] Preferably, the median particle size D50 of the particles obtained by the stable growth co-precipitation reaction in step (1) is 10 to 15 μm, for example, 10 μm, 10.3 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.5 μm, 11.8 μm, 12 μm, 12.3 μm, 12.5 μm, 12.8 μm, 13 μm, 13.3 μm, 13.5 μm, 13.8 μm, 14 μm, 14.3 μm, 14.5 μm, 14.8 μm or 15 μm.

[0064] Further preferably, after the stable growth co-precipitation reaction is completed, the slurry after the reaction is aged, washed and dried in sequence. The above treatment processes are all conventional technical solutions in the prior art to obtain the positive electrode precursor material.

[0065] Preferably, the concentration of the dopant solution is 5 to 30 g / L, for example, 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L or 30 g / L.

[0066] Preferably, the chemical formula of the positive electrode precursor in step (1) is Ni a Co b Mn c M d (OH)2, wherein M is the doping element in the dopant solution, 0.6<a<0.9, 0<b<0.2, 0<c<0.2, 0<d<0.1, a+b+c+d=1.

[0067] The present invention does not limit the specific preparation process of lithium sintering in step (2) of the present invention, and the present invention is applicable to any conventional lithium sintering preparation process for obtaining positive electrode materials from positive electrode precursors.

[0068] Illustratively, the present invention provides a specific preparation process of step (2):

[0069] The positive electrode precursor material and the lithium source are dry-mixed, and the mixed material is first sintered.

[0070] Optionally, the lithium source includes but is not limited to at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate.

[0071] Optionally, the ratio of the total molar amount of all metal elements in the positive electrode precursor material to the molar amount of lithium in the lithium source is 1:(1-1.2), for example, 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2.

[0072] Optionally, the first sintering atmosphere may be an oxygen-containing atmosphere, such as an oxygen atmosphere or an air atmosphere.

[0073] Optionally, the first sintering may be a one-stage sintering or a multi-stage sintering.

[0074] Furthermore, the multi-stage sintering includes performing first-stage sintering and second-stage sintering in sequence.

[0075] The heating rate of the first stage sintering is 3 to 5°C / min, for example, 3°C / min, 4°C / min or 5°C / min, the holding temperature of the first stage sintering is 450 to 650°C, for example, 450°C, 500°C, 550°C, 600°C or 650°C, and the holding time of the first stage sintering is 4 to 6h, for example, 4h, 5h or 6h.

[0076] The heating rate of the second stage sintering is 2 to 6°C / min, for example, 2°C / min, 3°C / min, 4°C / min, 5°C / min or 6°C / min, the holding temperature of the second stage sintering is 800 to 950°C, for example, 800°C, 850°C, 900°C or 950°C, and the sintering time of the second stage is 8 to 15h, for example, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, etc.

[0077] Preferably, the coating in step (3) comprises a metal compound, and preferably the metal compound comprises a bimetallic sulfide.

[0078] In the present invention, bimetallic sulfide is selected for magnetron sputtering coating, which can better play a synergistic role with the doping element Y in the sintered material; it plays a role in improving the lithium ion transport efficiency and inhibiting the occurrence of interface side reactions.

[0079] For example, the metal compound includes at least one of ZnO, MgO, Al2O3, SnO2, ZrO2, MgF2, LaF3, Li3PO4, LiPON, Li2CO3 or NiCo2S4, preferably NiCo2S4.

[0080] Preferably, the atmosphere of the magnetron sputtering in step (3) includes a protective gas, such as helium, argon, etc.

[0081] In the present invention, the atmosphere during the magnetron sputtering process can be controlled according to actual needs. In addition to the protective atmosphere, it can also be an oxygen-containing atmosphere, such as an air atmosphere or a mixed atmosphere of protective gas and oxygen.

[0082] Preferably, the working pressure of the magnetron sputtering in step (3) is 0.1-10 Pa, for example, 0.10.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa, 1 Pa, 1.1 Pa, 1.2 Pa, 1.3 Pa, 1.4 Pa, 1.5 Pa, 1.6 Pa, 1.7 Pa, 1.8 Pa, 1.9 Pa, 2 Pa, 3 Pa, 4 Pa, 5 Pa, 6 Pa, 7 Pa, 8 Pa, 9 Pa or 10 Pa, etc., preferably 0.5-2 Pa.

[0083] In the present invention, regulating the working pressure plays a role in regulating the plasma density and the mean free path of ions, and is further preferably 0.5-2 Pa, which better improves the quality and effect of magnetron sputtering.

[0084] Preferably, the power of the magnetron sputtering in step (3) is 10 to 500 W, for example, 10 W, 50 W, 100 W, 110 W, 120 W, 130 W, 140 W, 150 W, 160 W, 170 W, 180 W, 190 W, 200 W, 250 W, 300 W, 350 W, 400 W, 450 W or 500 W, etc., preferably 100 to 200 W.

[0085] In the present invention, the appropriate magnetron sputtering power can reasonably control the energy of ions in the plasma, thereby affecting the deposition rate and film quality, and is further preferably 100-200W, which is more conducive to obtaining a dense coating layer and a more uniform coating layer structure.

[0086] Preferably, the deposition rate of the magnetron sputtering in step (3) is 1 to 5 nm / min, for example, 1 nm / min, 2 nm / min, 3 nm / min, 4 nm / min or 5 nm / min.

[0087] In the present invention, the deposition rate of the magnetron sputtering in step (3) is regulated to be 1 to 5 nm / min, thereby further improving the accuracy of coating deposition.

[0088] In a second aspect, the present invention provides a modified positive electrode material, which is prepared by the preparation method described in the first aspect.

[0089] The modified positive electrode material provided by the present invention comprises a core containing a doping element and a coating structure obtained by magnetron sputtering and coated on the surface of the core.

[0090] In a third aspect, the present invention further provides a lithium-ion battery, comprising the modified positive electrode material as described in the second aspect.

[0091] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] In the preparation method of the present invention, during the positive electrode precursor preparation stage, the type of gas introduced and the relative size of the gas flow rate are regulated, which not only achieves uniform doping of the doping elements, but also adjusts the particle morphology of the positive electrode precursor material, thereby obtaining a loose and porous positive electrode precursor material with excellent physical and chemical properties; the coating obtained by synergistically adopting a specific magnetron sputtering stabilizes the crystal structure, suppresses lithium-nickel mixing, and improves the capacity, rate and cycle performance of the modified positive electrode material; and the process is simple, repeatable, and consistent, and large-scale mass production can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 This is the SEM image of the positive electrode precursor material prepared in Example 1. DETAILED DESCRIPTION

[0095] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0096] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0097] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0098] Example 1

[0099] This embodiment provides a method for preparing a modified positive electrode material, and the preparation method is as follows:

[0100] (1) preparing a mixed ternary metal sulfate solution with a total metal element concentration of 150 g / L and a molar ratio of Ni, Co, and Mn of 80:10:10, a precipitant NaOH solution with a mass concentration of 20%, and a complexing agent ammonia solution with a mass concentration of 10%, and preparing a 30 g / L yttrium trichloride dopant solution;

[0101] (2) Preparation of base solution: Add 300L of pure water and a certain amount of NaOH solution and ammonia water to a 600L reactor, and add 1.5m 3 Nitrogen was introduced into the bottom liquid at a rate of / h, and the mixture was stirred at a speed of 200r / min to mix uniformly. The temperature was then raised to 70°C, and the pH value of the reaction bottom liquid was controlled to be 11.5, the ammonia concentration was controlled to be 10g / L, and the total alkalinity was controlled to be 20g / L;

[0102] (3) Coprecipitation reaction: The reaction temperature was controlled at 80°C, the stirring speed was 300 r / min, the flow rates of ammonia water, alkali solution, ternary solution, and yttrium chloride solution were stabilized, and the following stage reactions were carried out:

[0103] a. Nucleation coprecipitation reaction: Ammonia water, alkali solution, ternary solution and yttrium chloride solution are flowed into the reactor for reaction, so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and the pH value is controlled to be 11-11.2, and the ammonia concentration is controlled to be 8g / L. The flow rate of the ternary metal salt solution is 6L / h, the flow rate of ammonia water is 800mL / h, the flow rate of the alkali solution is 2.5L / h, and the flow rate of the yttrium solution is 150mL / h. When the internal nucleation is completed and the growth reaches 4μm, the core solution is obtained, and the first stage of the reaction is completed. No air is passed through this reaction stage, and nitrogen is kept unobstructed. The nitrogen flow rate is adjusted to 1.5m3 / h;

[0104] b. Main growth co-precipitation reaction - rapid growth phase: Increase the flow rate of ammonia, alkali solution, ternary solution and yttrium chloride solution so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and control the pH value to 9.8-10, the ammonia concentration is controlled to 3g / L, the flow rate of the ternary metal salt solution is 12L / h, the flow rate of ammonia is 1000mL / h, the flow rate of the alkali solution is 4L / h, the flow rate of the yttrium solution is 400mL / h, and on the basis of nitrogen gas introduction, air is introduced synchronously so that the ratio of air flow rate to nitrogen flow rate is maintained at 0.4. When the rapid growth phase grows to 10μm, the second stage of the reaction ends;

[0105] c. Stable growth coprecipitation reaction - stable growth period: continue to increase the flow rate of ammonia water, alkali solution, ternary solution and yttrium chloride solution, so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and control the pH value to 10.2-10.5, the ammonia concentration is controlled to 6g / L, the flow rate of the ternary metal salt solution is 25L / h, the flow rate of ammonia water is 2000mL / h, the flow rate of the alkali solution is 8L / h, and the flow rate of the yttrium solution is 600mL / h. Reduce the air flow rate so that the ratio of the air flow rate to the nitrogen flow rate is maintained at 0.2. When the growth particle size reaches 12μm, stop the feeding reaction to obtain a slurry;

[0106] (4) washing and drying the obtained qualified slurry, wherein the washing is performed by alkali washing twice and water washing five times, and drying is performed at a relatively low temperature of 120° C., thereby finally forming a Y-doped modified loose ternary positive electrode precursor material;

[0107] (5) The Y-doped modified loose ternary precursor product prepared in step (4) and lithium hydroxide are batch-mixed in a high-pressure mixer to obtain a mixture, wherein the molar ratio of the total molar amount of the metal elements contained in the ternary precursor to the molar ratio of the lithium element contained in the lithium source is 1:1.05, and the mixture is sintered in two stages in a box furnace, wherein the first stage is sintered at a heating rate of 5°C / min to 550°C and then kept warm for 4 hours, and then the second stage is continued to sinter, at a heating rate of 5°C / min to 900°C and then kept warm for 12 hours, to obtain a fired material;

[0108] (6) The sintered material prepared in step (5) was subjected to magnetron sputtering using bimetallic sulfide NiCo2S4, wherein a mixture of Ar (with a flow rate of 40 sccm) and O2 (with a flow rate of 10 sccm) was introduced into the magnetron sputtering step as a working gas, the working pressure and the sputtering power were set to 1.0 Pa and 120 W, respectively, the target material was NiCo2S4, the deposition rate of the target material was controlled to be 2 nm / min, and the deposition was carried out for 5 min to obtain a modified positive electrode material with a 10 nm bimetallic sulfide NiCo2S4 coating.

[0109] Figure 1 The SEM image of the positive electrode precursor material prepared in Example 1 is shown. Figure 1 It can be seen that the primary particles of the positive electrode precursor material prepared in Example 1 of the present invention are relatively loose and needle-shaped.

[0110] Example 2

[0111] This embodiment provides a method for preparing a modified positive electrode material, and the preparation method is as follows:

[0112] (1) preparing a mixed ternary metal sulfate solution with a total metal element concentration of 100 g / L and a molar ratio of Ni, Co, and Mn of 80:10:10, a precipitant NaOH solution with a mass concentration of 20%, and a complexing agent ammonia solution with a mass concentration of 10%, and preparing a 5 g / L yttrium trichloride dopant solution;

[0113] (2) Preparation of base solution: Add 300L of pure water and a certain amount of NaOH solution and ammonia water to a 600L reactor, and add 1.5m 3 Nitrogen was introduced into the bottom liquid at a rate of / h, and the mixture was stirred at a speed of 200r / min to mix uniformly. The temperature was then raised to 70°C, and the pH value of the reaction bottom liquid was controlled to be 11.5, the ammonia concentration was controlled to be 10g / L, and the total alkalinity was controlled to be 20g / L;

[0114] (3) Coprecipitation reaction: The reaction temperature was controlled at 60°C, the stirring speed was 380 r / min, the flow rates of ammonia water, alkali solution, ternary solution, and yttrium chloride solution were stabilized, and the following stage reactions were carried out:

[0115] a. Nucleation coprecipitation reaction: Ammonia water, alkali solution, ternary solution and yttrium chloride solution are flowed into the reactor for reaction, so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and the pH value is controlled to be 11.5, and the ammonia concentration is controlled to be 10g / L. The flow rate of the ternary metal salt solution is 8L / h, the flow rate of ammonia water is 1000mL / h, the flow rate of the alkali solution is 3L / h, and the flow rate of the yttrium solution is 300mL / h. When the internal nucleation is completed and the growth reaches 4μm, the core solution is obtained, and the first stage of the reaction is completed. No air is passed through this reaction stage, and nitrogen is kept unobstructed. The nitrogen flow rate is adjusted to 1.5m 3 / h;

[0116] b. Main growth co-precipitation reaction - rapid growth phase: Increase the flow rate of ammonia, alkali solution, ternary solution and yttrium chloride solution so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and control the pH value to 9.5, the ammonia concentration is controlled to 4g / L, the flow rate of the ternary metal salt solution is 15L / h, the flow rate of ammonia is 1500mL / h, the flow rate of the alkali solution is 3.5L / h, the flow rate of the yttrium solution is 500mL / h, and on the basis of nitrogen gas introduction, air is introduced synchronously so that the ratio of air flow rate to nitrogen flow rate is maintained at 0.5. When the rapid growth phase grows to 10μm, the second stage of the reaction ends;

[0117] c. Stable growth coprecipitation reaction - stable growth period: continue to increase the flow rate of ammonia water, alkali solution, ternary solution and yttrium chloride solution, so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and control the pH value to 11, the ammonia control concentration is 8g / L, the flow rate of the ternary metal salt solution is 30L / h, the flow rate of ammonia water is 2500mL / h, the flow rate of the alkali solution is 7L / h, and the flow rate of the yttrium solution is 800mL / h. Reduce the air flow rate so that the ratio of the air flow rate to the nitrogen flow rate is maintained at 0.1. When the growth particle size reaches 12μm, stop the feeding reaction to obtain a slurry;

[0118] (4) washing and drying the obtained qualified slurry, wherein the washing is performed by alkali washing twice and water washing five times, and drying is performed at a relatively low temperature of 120° C., thereby finally forming a Y-doped modified loose ternary positive electrode precursor material;

[0119] (5) The Y-doped modified loose ternary precursor product prepared in step (4) and lithium hydroxide are batch-mixed in a high-pressure mixer to obtain a mixture, wherein the molar ratio of the total molar amount of the metal elements contained in the ternary precursor to the molar ratio of the lithium element contained in the lithium source is 1:1.05, and the mixture is sintered in two stages in a box furnace, wherein the first stage is sintered at a heating rate of 5°C / min to 450°C and then kept warm for 6 hours, and then the second stage is continued to sinter, at a heating rate of 5°C / min to 800°C and then kept warm for 15 hours, to obtain a fired material;

[0120] (6) The sintered material prepared in step (5) was subjected to magnetron sputtering using bimetallic sulfide NiCo2S4, wherein a mixture of Ar (with an inlet flow rate of 40 sccm) and O2 (with an inlet flow rate of 10 sccm) was introduced into the magnetron sputtering step as a working gas, the working pressure and the sputtering power were set to 1.0 Pa and 120 W, respectively, the target material was NiCo2S4, the deposition rate of the target material was controlled to be 5 nm / min, and the deposition was carried out for 2 min to obtain a modified positive electrode material with a 10 nm bimetallic sulfide NiCo2S4 coating.

[0121] Example 3

[0122] This embodiment provides a method for preparing a modified positive electrode material, and the preparation method is as follows:

[0123] (1) preparing a mixed ternary metal sulfate solution with a total metal element concentration of 125 g / L and a molar ratio of Ni, Co, and Mn of 80:10:10, a precipitant NaOH solution with a mass concentration of 20%, and a complexing agent ammonia solution with a mass concentration of 10%, and preparing a 15 g / L yttrium trichloride dopant solution;

[0124] (2) Preparation of base solution: Add 300L of pure water and a certain amount of NaOH solution and ammonia water to a 600L reactor, and add 1.5m 3 Nitrogen was introduced into the bottom liquid at a rate of / h, and the mixture was stirred at a speed of 200r / min to mix uniformly. The temperature was then raised to 70°C, and the pH value of the reaction bottom liquid was controlled to be 11.5, the ammonia concentration was controlled to be 10g / L, and the total alkalinity was controlled to be 20g / L;

[0125] (3) Coprecipitation reaction: The reaction temperature was controlled at 80°C, the stirring speed was 300 r / min, the flow rates of ammonia water, alkali solution, ternary solution, and yttrium chloride solution were stabilized, and the following stage reactions were carried out:

[0126] a. Nucleation coprecipitation reaction: Ammonia water, alkali solution, ternary solution and yttrium chloride solution are flowed into the reactor for reaction, so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and the pH value is controlled to 11.3, and the ammonia concentration is controlled to 8g / L. The flow rate of the ternary metal salt solution is 7L / h, the flow rate of ammonia water is 850mL / h, the flow rate of the alkali solution is 2.7L / h, and the flow rate of the yttrium solution is 100mL / h. When the internal nucleation is completed and the growth reaches 3.5μm, the core solution is obtained, and the first stage of the reaction is completed. No air is passed through this reaction stage, and nitrogen is kept unobstructed. The nitrogen flow rate is adjusted to 1.5m 3 / h;

[0127] b. Main growth co-precipitation reaction - rapid growth phase: Increase the flow rate of ammonia, alkali solution, ternary solution and yttrium chloride solution so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and control the pH value to 9.5, the ammonia concentration is controlled to 3g / L, the flow rate of the ternary metal salt solution is 10L / h, the flow rate of ammonia is 1200mL / h, the flow rate of the alkali solution is 3.5L / h, the flow rate of the yttrium solution is 200mL / h, and on the basis of nitrogen gas introduction, air is introduced synchronously so that the ratio of air flow to nitrogen flow is maintained at 0.3. When the rapid growth phase grows to 11μm, the second stage of the reaction ends;

[0128] c. Stable growth coprecipitation reaction - stable growth period: continue to increase the flow rate of ammonia water, alkali solution, ternary solution and yttrium chloride solution, so that the molar percentage of yttrium added in the yttrium solution accounts for 0.5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and control the pH value to 10.7, the ammonia concentration is controlled to 6 g / L, the flow rate of the ternary metal salt solution is 20 L / h, the flow rate of ammonia water is 2200 mL / h, the flow rate of the alkali solution is 7 L / h, and the flow rate of the yttrium solution is 500 mL / h, reduce the air flow rate, so that the ratio of air flow rate to nitrogen flow rate is maintained at 0.15, and stop the feeding reaction when the growth particle size reaches 15 μm to obtain a slurry;

[0129] (4) washing and drying the obtained qualified slurry, wherein the washing is performed by alkali washing twice and water washing five times, and drying is performed at a relatively low temperature of 120° C., thereby finally forming a Y-doped modified loose ternary positive electrode precursor material;

[0130] (5) The Y-doped modified loose ternary precursor product prepared in step (4) and lithium hydroxide are batch-mixed in a high-pressure mixer to obtain a mixture, wherein the molar ratio of the total molar amount of the metal elements contained in the ternary precursor to the molar ratio of the lithium element contained in the lithium source is 1:1.05, and the mixture is sintered in two stages in a box furnace, wherein the first stage sintering is carried out by heating the temperature to 600°C at a heating rate of 5°C / min and then keeping the temperature for 4 hours, and then continuing the second stage sintering, heating the temperature to 950°C at a heating rate of 5°C / min and then keeping the temperature for 12 hours to obtain a fired material;

[0131] (6) The sintered material prepared in step (5) was subjected to magnetron sputtering using bimetallic sulfide NiCo2S4, wherein a mixture of Ar (with a flow rate of 40 sccm) and O2 (with a flow rate of 10 sccm) was introduced into the magnetron sputtering step as a working gas, the working pressure and the sputtering power were set to 1.0 Pa and 120 W, respectively, the target material was NiCo2S4, the deposition rate of the target material was controlled to be 3 nm / min, and the deposition was carried out for 5 min to obtain a modified positive electrode material with a 15 nm bimetallic sulfide NiCo2S4 coating.

[0132] Example 4

[0133] The difference between this embodiment and embodiment 1 is that during the entire coprecipitation reaction process of step (3) of this embodiment, the molar percentage of yttrium added to the yttrium solution is made to account for 0.2% of the total molar percentage of Ni, Co, and Mn in the ternary precursor.

[0134] The rest of the preparation methods are consistent with those in Example 1.

[0135] Example 5

[0136] The difference between this embodiment and embodiment 1 is that during the entire coprecipitation reaction process of step (3) of this embodiment, the molar percentage of yttrium added to the yttrium solution is made to account for 1% of the total molar percentage of Ni, Co, and Mn in the ternary precursor.

[0137] The rest of the preparation methods are consistent with those in Example 1.

[0138] Example 6

[0139] The difference between this embodiment and embodiment 1 is that during the entire coprecipitation reaction process of step (3) of this embodiment, the molar percentage of yttrium added to the yttrium solution is made to account for 5% of the total molar percentage of Ni, Co, and Mn in the ternary precursor.

[0140] The rest of the preparation methods are consistent with those in Example 1.

[0141] Example 7

[0142] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, during the main growth co-precipitation reaction, the ratio of air flow rate to nitrogen flow rate is maintained at 0.15; during the stable growth co-precipitation reaction, the ratio of air flow rate to nitrogen flow rate is maintained at 0.1.

[0143] The rest of the preparation methods are consistent with those in Example 1.

[0144] Example 8

[0145] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, during the main growth co-precipitation reaction, the ratio of air flow rate to nitrogen flow rate is maintained at 0.6.

[0146] The rest of the preparation methods are consistent with those in Example 1.

[0147] Example 9

[0148] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, during the stable growth co-precipitation reaction, the ratio of air flow rate to nitrogen flow rate is maintained at 0.05.

[0149] The rest of the preparation methods are consistent with those in Example 1.

[0150] Example 10

[0151] The difference between this embodiment and embodiment 1 is that in step (3) of this embodiment, during the main growth co-precipitation reaction and the stable growth co-precipitation reaction, the flow rate of each raw material is consistent with the flow rate of the nucleation co-precipitation reaction, that is, they are exactly the same.

[0152] The rest of the preparation methods are consistent with those in Example 1.

[0153] Example 11

[0154] The difference between this embodiment and embodiment 1 is that the dopant solution in step (1) of this embodiment is a cerium sulfate solution.

[0155] The rest of the preparation methods are consistent with those in Example 1.

[0156] Example 12

[0157] The difference between this embodiment and embodiment 1 is that in step (6) of this embodiment, the deposition rate is 0.5 nm / min.

[0158] The rest of the preparation methods are consistent with those in Example 1.

[0159] Example 13

[0160] The difference between this embodiment and embodiment 1 is that in step (6) of this embodiment, the deposition rate is 5.5 nm / min.

[0161] The rest of the preparation methods are consistent with those in Example 1.

[0162] Example 14

[0163] The difference between this embodiment and embodiment 1 is that the deposition material in step (6) of this embodiment is Li3PO4, that is, the target material is also Li3PO4.

[0164] The rest of the preparation methods are consistent with those in Example 1.

[0165] Comparative Example 1

[0166] The difference between this comparative example and Example 1 is that in the preparation process of step (3) of this comparative example, air is also introduced during the nucleation stage, and the amount of air introduced is consistent with that in the main reaction co-precipitation reaction stage.

[0167] The rest of the preparation methods are consistent with those in Example 1.

[0168] Comparative Example 2

[0169] The difference between this comparative example and Example 1 is that in the preparation process of step (3) of this comparative example, during the main growth co-precipitation reaction, the ratio of air flow rate to nitrogen flow rate is maintained at 0.2; while during the stable growth co-precipitation reaction, the ratio of air flow rate to nitrogen flow rate is maintained at 0.4; that is, the flow ratio of the first air and the second protective gas in the main reaction stage is less than the flow ratio of the second air and the third protective gas in the stable growth stage.

[0170] The rest of the preparation methods are consistent with those in Example 1.

[0171] Comparative Example 3

[0172] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, the yttrium trichloride dopant solution is not prepared, that is, no doping is performed.

[0173] The rest of the preparation methods are consistent with those in Example 1.

[0174] Comparative Example 4

[0175] The difference between this comparative example and Example 1 is that step (6) is not performed in this comparative example.

[0176] The rest of the preparation methods are consistent with those in Example 1.

[0177] Comparative Example 5

[0178] The difference between this comparative example and Example 1 is that step (6) of this comparative example is adjusted to traditional physical coating: the bimetallic sulfide NiCo2S4 is dry-mixed with the calcined material and heat-treated at 300°C to obtain a modified positive electrode material.

[0179] The rest of the preparation methods are consistent with those in Example 1.

[0180] [Battery preparation and performance testing]

[0181] (1) Battery preparation:

[0182] The positive electrode material obtained in the above examples and comparative examples was used as the positive electrode active material and mixed with conductive carbon and PVDF in a ratio of 95:2.5:2.5. The mixture was then dispersed in methyl pyrrolidone (NMP) as a solvent to obtain a positive electrode slurry, which was evenly coated on an aluminum foil. After coating, the current collector was punched to obtain a coin-shaped electrode, which was vacuum-dried at 120°C overnight to obtain a positive electrode sheet. Metallic lithium was selected as the negative electrode, and 1M LiPF6 was dissolved in EC and DMC solvents (volume ratio 3:7) as the electrolyte. The positive electrode, negative electrode, and separator (PP separator) were wound to prepare a battery cell, which was then assembled into a lithium-ion battery through packaging, liquid injection, formation, and volume separation.

[0183] (2) Performance testing:

[0184] Capacity and Cycles: The prepared lithium-ion battery was subjected to electrochemical performance testing at 25°C. CR2032 coin-type half-cells were cycled between 3.0 and 4.4 v (vs Li / Li+) at 0.2 C to measure the initial discharge capacity and efficiency. The discharge capacity at the 100th cycle was used to obtain the capacity retention rate after 100 cycles.

[0185] Rate performance: At 25°C, charge at a constant current of 1C to a cut-off voltage of 4.4V, then switch to constant voltage charging until the current is ≤0.05C, let it stand for 5 minutes, and discharge at a constant current of 1C to a cut-off voltage of 3.0V. Record the discharge capacity, repeat 2-3 times, and take the average value as the initial capacity C0;

[0186] Then charge at a constant current of 1C to a cut-off voltage of 4.4V, switch to constant voltage charging to a current ≤ 0.05C, and discharge at a constant current of 5C to a cut-off voltage of 3.0V. After 100 cycles, the capacity retention rate at 5C was obtained.

[0187] The test results of the above tests are shown in Table 1.

[0188] Table 1

[0189]

[0190]

[0191] To sum up, in the preparation method of the present invention, during the preparation stage of the positive electrode precursor, the type of gas introduced and the relative size of the gas flow rate are regulated, which not only achieves uniform doping of the doping elements, but also adjusts the particle morphology of the positive electrode precursor material, thereby obtaining a loose and porous positive electrode precursor material with excellent physical and chemical properties; the coating obtained by synergistically adopting a specific magnetron sputtering stabilizes the crystal structure, inhibits lithium-nickel mixing, and improves the capacity, rate and cycle performance of the modified positive electrode material; and the process is simple, repeatable, and consistent, and large-scale mass production can be achieved.

[0192] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a modified positive electrode material, characterized in that: The preparation method comprises the following steps: (1) adding a nickel-cobalt-manganese main metal salt solution, a dopant solution, a precipitant solution, and a complexing agent solution in parallel, and sequentially performing a nucleation coprecipitation reaction, a main growth coprecipitation reaction, and a stable growth coprecipitation reaction to obtain a positive electrode precursor material; (2) mixing the positive electrode precursor material and the lithium source, and first sintering to obtain a sintered product; (3) coating the calcined product with a coating material by magnetron sputtering to obtain the modified positive electrode material; Wherein, in step (1), the first protective gas is introduced during the nucleation co-precipitation reaction, the first air and the second protective gas are introduced during the main growth co-precipitation reaction; and the second air and the third protective gas are introduced during the stable growth co-precipitation reaction; The flow rate ratio of the first air to the second protective gas is greater than the flow rate ratio of the second air to the third protective gas.

2. The preparation method according to claim 1, characterized in that The doping element in the dopant solution of step (1) includes any one or a combination of at least two of aluminum, titanium, niobium, zirconium, tungsten, vanadium, strontium, gallium, cerium, yttrium, lanthanum or antimony, preferably yttrium; Preferably, in the parallel addition process of step (1), the molar amount of the doping element in the dopant solution accounts for 0.05% to 5%, preferably 0.2% to 1%, based on the total molar amount of the nickel-cobalt-manganese mixed salt solution as 100%.

3. The preparation method according to claim 1, characterized in that In step (1), the flow rate of the nickel-cobalt-manganese main metal salt solution during the nucleation co-precipitation reaction is less than the flow rate of the nickel-cobalt-manganese main metal salt solution during the main growth co-precipitation reaction and less than the flow rate of the nickel-cobalt-manganese main metal salt solution during the stable growth co-precipitation reaction; Preferably, in step (1), the flow rate of the dopant solution during the nucleation co-precipitation reaction is less than the flow rate of the dopant solution during the main growth co-precipitation reaction and less than the flow rate of the dopant solution during the stable growth co-precipitation reaction; Preferably, in step (1), the flow rate of the precipitant solution during the nucleation co-precipitation reaction is less than the flow rate of the precipitant solution during the main growth co-precipitation reaction and less than the flow rate of the precipitant solution during the stable growth co-precipitation reaction; Preferably, in step (1), the flow rate of the complexing agent solution during the nucleation co-precipitation reaction is less than the flow rate of the complexing agent solution during the main growth co-precipitation reaction and less than the flow rate of the complexing agent solution during the stable growth co-precipitation reaction.

4. The preparation method according to claim 1 or 3, characterized in that During the nucleation coprecipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution is 6 to 8 L / h, the flow rate of the dopant solution is 100 to 300 mL / h, the flow rate of the precipitant solution is 2.4 to 3 L / h, and the flow rate of the complexing agent solution is 700 to 1000 mL / h; Preferably, during the main growth co-precipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution is 10 to 15 L / h, the flow rate of the dopant solution is 200 to 500 mL / h, the flow rate of the precipitant solution is 3.5 to 4.5 L / h, and the flow rate of the complexing agent solution is 1 to 1.5 L / h; Preferably, during the stable growth co-precipitation reaction in step (1), the flow rate of the nickel, cobalt and manganese main metal salt solution is 20 to 30 L / h, the flow rate of the dopant solution is 500 to 800 mL / h, the flow rate of the precipitant solution is 7 to 8 L / h, and the flow rate of the complexing agent solution is 2 to 2.5 L / h.

5. The preparation method according to claim 1, characterized in that In the main growth co-precipitation reaction process of step (1), the flow ratio of the first air to the first protective gas is 0.2 to 0.5; Preferably, in the stable growth co-precipitation reaction process of step (1), the flow rate ratio of the second air to the second protective gas is 0.1 to 0.

2.

6. The preparation method according to claim 1, characterized in that The pH value of the nucleation coprecipitation reaction in step (1) is 11 to 11.5; Preferably, the pH value of the main growth co-precipitation reaction in step (1) is 9.5-10; Preferably, the pH value of the stable growth co-precipitation reaction in step (1) is 10.2-11.

7. The preparation method according to claim 1, characterized in that The median particle size D50 of the particles obtained by the nucleation co-precipitation reaction in step (1) is 3.5 to 4 μm; Preferably, the median particle size D50 of the particles obtained by the main growth co-precipitation reaction in step (1) is 8 to 10 μm; Preferably, the median particle size D50 of the particles obtained by the stable growth co-precipitation reaction in step (1) is 10 to 15 μm.

8. The preparation method according to claim 1, characterized in that The coating in step (3) comprises a metal compound, preferably a bimetallic sulfide; Preferably, the power of the magnetron sputtering in step (3) can be 10 to 500 W, preferably 100 to 200 W; Preferably, the working pressure of the magnetron sputtering in step (3) can be 0.1 to 10 Pa, preferably 0.5 to 2 Pa; Preferably, the deposition rate of the magnetron sputtering in step (3) is 1 to 5 nm / min.

9. A modified positive electrode material, characterized in that The modified positive electrode material is prepared by the preparation method according to any one of claims 1 to 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the modified positive electrode material according to claim 9.

Images