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

Abstract

The present application provides a precursor of a positive electrode active material. The particles of the precursor include a core and a shell covering the core. The materials of the core and the shell are both nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide. The core is doped with a flux, and the flux is selected from one or more of the oxides, carbonates, and hydroxides of Sr, Li, Mg, Ni, Co, and Zr. The shell is doped with a reaction restraining agent. The reaction restraining agent is selected from one or more of the lithium compounds, oxides, carbonates, and hydroxides of Ta, W, Al, Mn, Mo, and La. The core of the precursor particles is provided with a flux and the shell is provided with a reaction restraining agent, so that the subsequent crystallization of the precursor develops in a direction from the inside to the outside. The present application also provides a positive electrode active material and a preparation method thereof, including a positive electrode of the positive electrode active material and a lithium ion battery, and a preparation method of the precursor.

Description

Technical Field

[0001] The present application relates to a precursor of a positive electrode active material and a preparation method thereof, a preparation method of a positive electrode active material, a 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

[0002] At present, the precursor of ternary cathode materials is mainly prepared by coprecipitation method, and then the precursor is mixed with an appropriate amount of lithium source and additives for high-temperature solid-phase sintering to obtain ternary single crystal materials of a certain particle size. The precursor is regulated by the process technology, and then the main content elements, trace elements, particle size distribution, specific surface area, tap density, sphericity, density, whisker thickness, crystal surface parameters and other indicators of the precursor are regulated to prepare various types of ternary precursors that meet project needs. At present, during the high-temperature solid-phase sintering process of most precursors, multiple crystal nuclei will be formed. Due to the ion migration at high temperature, the crystal nuclei will further aggregate and develop, and certain micro-agglomerations will be formed during this period. It is necessary to use high-intensity airflow crushing and other means 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 changes, lattice distortion and other reasons, exposing new surfaces to undergo side reactions with the electrolyte, thereby deteriorating the electrochemical properties of the battery materials. Summary of the invention

[0003] 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.

[0004] 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;

[0005] 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;

[0006] 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.

[0007] The core of the particles of the precursor of the present application is provided with a flux and the shell is provided with a reaction restraint agent, so that the crystallization of the subsequent precursor develops from the inside to the outside, that is, the closer to the center of the core, the better and more perfect the crystallization. The shell is added with a high-valent cationic additive as a reaction restraint agent, which can inhibit the crystallization and ion migration of the precursor, resulting in a large difference in the critical temperature of the core and shell reaction. The precursor using this structure can produce a highly dispersed and highly spherical single-crystal ternary positive electrode active material.

[0008] The second aspect of the present application provides a method for preparing a positive electrode active material, comprising:

[0009] The precursor of the positive electrode active material and the lithium source of the first aspect are sintered once, the temperature range of the sintering is 600-950° C., and the atmosphere is air or high-purity oxygen atmosphere;

[0010] 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;

[0011] 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.

[0012] Adding an active inhibitor during secondary sintering can reduce the surface energy and prevent ion migration between adjacent precursors to cause secondary crystallization. The surface energy of the core-shell is higher than the surface energy between particles, and the particles grow inward. The precursor with this structure combined with the active inhibitor during secondary sintering can obtain highly dispersed and highly spherical single-crystal ternary positive electrode active materials.

[0013] The third aspect of the present application provides a positive electrode active material, which is prepared by the preparation method described in the second aspect.

[0014] The fourth aspect of the present application provides a positive electrode, which includes a positive electrode collector and a positive electrode active material layer located on the surface of the positive electrode collector, and the positive electrode active material layer includes the positive electrode active material prepared by the preparation method described in the second aspect.

[0015] A fifth aspect of 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.

[0016] The 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:

[0017] Add water to nickel salt, cobalt salt and manganese salt and mix them evenly to obtain solution I;

[0018] Adding precipitated alkali solution into the reaction vessel;

[0019] Continuously introducing the solution I and the complexing agent solution into the reaction container to react and generate precursor particles;

[0020] 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;

[0021] 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;

[0022] 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;

[0023] 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

[0024] Figure 1 Schematic diagram of the precursor particles of the positive electrode active material according to an embodiment of the present application.

[0025] Figure 2 This is a scanning electron microscope image of the positive electrode active material of Example 1 of the present application.

[0026] Figure 3 This is the X-ray diffraction pattern of the positive electrode active material of Example 1 of the present application.

[0027] Figure 4 This is a scanning electron microscope image of the positive electrode active material of Example 2 of the present application.

[0028] Figure 5 This is the X-ray diffraction pattern of the positive electrode active material of Example 2 of the present application. DETAILED DESCRIPTION

[0029] The present application provides a precursor for a positive electrode active material for a lithium ion battery. Figure 1 As shown, the precursor particle 10 includes a core 11 and a shell 13 covering the core 11. The material of the ternary precursor particle is nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide, that is, the main materials in the core 11 and the shell 13 are nickel-cobalt-manganese oxide or nickel-cobalt-manganese hydroxide.

[0030] The chemical formula of nickel, cobalt, manganese hydroxide is Nix 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.

[0031] In the present application, the core 11 is doped with a flux. The flux is selected from one or more of oxides, carbonate compounds, and hydroxides of Sr, Li, Mg, Ni, Co, and Zr. The weight of the doped flux is 100-2000 ppm of the weight of the precursor. The flux helps the crystallization of the precursor.

[0032] In the present application, the shell 13 is doped with a reaction restraining agent. 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. The weight of the doped reaction restraining agent is 100-4000ppm of the weight of the precursor. The reaction restraining agent is a high-valent cation that can inhibit the crystallization and ion migration of the precursor.

[0033] Along the direction from the center of the core 11 to the shell 13, the concentration of the flux gradually decreases, and the concentration of the reaction restraining agent gradually increases. The closer to the center of the core, the higher the concentration of the doped flux, and the lower the concentration of the doped reaction restraining agent. In this way, through the gradient design of the flux and the reaction restraining agent, the single crystal crystallization of the precursor is subsequently guided to grow from the inside to the outside.

[0034] 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 interior of the precursor particles can be used to gather some residual lithium.

[0035] 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 inner 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.

[0036] The present application also provides a method for preparing the precursor of the above-mentioned positive electrode active material, comprising the following steps S1 to S7.

[0037] 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.

[0038] Step S2: adding a precipitating alkali solution into a reaction vessel. The alkali in the precipitating alkali solution is used to react with the nickel salt, cobalt salt, and manganese salt in solution I to generate a hydroxide precipitate. The alkali may be sodium hydroxide, but is not limited thereto.

[0039] Step S3: continuously introducing solution I and complexing agent solution into the reaction container for reaction to 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.

[0040] 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.

[0041] Step S5: When the inner 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.

[0042] 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.

[0043] In the process of step S4 to step S6, solution I and complexing agent solution are also continuously introduced into the reaction vessel. In addition, in the steps of step S3 to step S5, the addition rate of solution I is constant, and when step S6 is reached, the addition rate of solution I can be increased to obtain the outer surface of the uneven, serrated kernel 11.

[0044] 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 can be used in step S6; when the reaction restraining agent is a W compound, ammonium tungstate or sodium tungstate can be used in step S6; when the reaction restraining agent is an Al compound, aluminum nitrate or sodium aluminate can be used in step S6; when the reaction restraining agent is a Mn compound, manganese sulfate can be used in step S6; when the reaction restraining agent is a Zr compound, zirconium nitrate or zirconium oxychloride can be used in step S6; when the reaction restraining agent is a Mo compound, sodium molybdate can be used in step S6; when the reaction restraining agent is a La compound, lanthanum nitrate can be used in step S6.

[0045] Step S7: stop the reaction, centrifuge, filter, wash, dry and sieve the slurry in the reaction container to obtain precursor particles.

[0046] In step S7, the drying temperature is controlled not to exceed 200° C. The material of the precursor particles obtained by this method is 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.

[0047] The present application also provides a method for preparing a positive electrode active material, which comprises the following steps 1 to 3.

[0048] Step 1: Mix the precursor of the positive electrode active material, the lithium source and the additives, and perform a sintering process. The sintering temperature range is 600-950° C., and the atmosphere is air or high-purity oxygen atmosphere.

[0049] Step 2: The product of the primary sintering is mixed with an active inhibitor for secondary sintering. The temperature range of the secondary sintering is 300 to 850° C. and the atmosphere is a high-purity oxygen atmosphere.

[0050] Step 3: The product of the secondary sintering and the nano-coating are 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.

[0051] 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, and the inner core develops preferentially due to the presence of flux to form seed crystals, and the outer shell develops at a low level 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 molar ratio of precursor, lithium source, and additive is 1: (1.02-1.06): (0.001-0.01).

[0052] In step 2, after the product of the primary sintering is cooled, an active inhibitor is added for high-speed mixing. A secondary high-temperature sintering is performed, and the sintering temperature is higher than the sintering temperature of step 1, and the 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 shell gradually develop each precursor particle 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).

[0053] In step 3, after the product of step 2 is cooled, it is mixed with a nano-coating that can inhibit the reaction with the electrolyte and improve the kinetics of the material interface reaction, and is sintered three times at low temperature in an oxygen atmosphere to obtain a highly dispersed and highly spherical ternary positive electrode material after composite modification. The nano-coating can be nano-alumina, titanium oxide, aluminum hydroxide, aluminum oxyhydroxide, tungsten oxide, etc. In some embodiments, the product of step 2 is mixed with the nano-coating at a mass ratio of 1: (0.001-0.02).

[0054] The present application also provides a positive electrode active material, which is prepared by the above-mentioned method for preparing the positive electrode active material.

[0055] The core of the precursor particles of the present application is provided with a flux with a concentration gradient distribution and the shell is provided with a reaction restraint with a concentration gradient distribution, so that the subsequent crystallization of the precursor develops from the inside to the outside, that is, the closer to the center of the core, the better and more perfect the crystallization. High-valent cations are added to the shell as reaction restraints, which can inhibit the crystallization and ion migration of the precursor, resulting in a large difference in the critical temperature of the core and shell reactions.

[0056] Adding an active inhibitor during secondary sintering can reduce the surface energy and prevent ion migration between adjacent precursors to cause secondary crystallization. The surface energy of the core-shell is higher than the surface energy between particles, and the particles grow inward. The precursor with this structure combined with the active inhibitor during secondary sintering can obtain highly dispersed and highly spherical single-crystal ternary positive electrode active materials.

[0057] 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.

[0058] The positive electrode active material layer includes not only the positive electrode active material but also a conductive agent, a binder, and the like.

[0059] 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.

[0060] The following is a detailed description through Examples 1 to 5.

[0061] Example 1

[0062] (1) Precursor synthesis: nickel sulfate, cobalt sulfate and manganese sulfate are selected as the main materials, 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.

[0063] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution, add it to the reactor, add appropriate amount of deionized water and stir evenly, adjust the pH ratio to 11.75. Add ammonia water, control the ammonia concentration to 4 g / L, maintain the solution temperature at 40°C, and continuously introduce nitrogen as a protective gas.

[0064] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 4 L / h. The stirring frequency of the reactor was 40 Hz. Ammonia water was continuously added as a complexing agent. Nitrogen was introduced to maintain the pH value of the reaction system stable at 11.50. 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. The particle size data of the dried material was tested using a Malvern particle size tester.

[0065] (4) When the precursor D50 grows horizontally to 1.5 μm, the rate of introduction of magnesium sulfate is reduced by 0.02 L / h until it stops, thereby obtaining a precursor core doped with gradient Mg, with a core D50 of 1.7 μm.

[0066] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 8 L / h, the stirring frequency was maintained at 40 Hz, the pH value of the reactor solution was adjusted to 11.0, and 2 mol / L ammonium tungstate solution was added at the same time, the initial addition rate was 0.02 L / h, and the rate was increased by 0.03 L / h every hour until it reached 0.2 L / h and 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, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0067] (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 concentration element distribution, and tungsten exists in the shell in the form of tungstate.

[0068] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at a high speed, loaded into a sagger, placed in a muffle furnace, introduced with oxygen, and the oxygen concentration in the furnace was controlled to reach 95%, sintered at a high temperature of 820° C. for 8 hours, and removed from the furnace after cooling.

[0069] (8) The above materials were mixed with nano-vanadium pentoxide at a mass ratio of 1:0.005, 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 880° C. for 10 hours, and then removed from the furnace after cooling. A mechanical pulverizer was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0070] (9) The above materials and nano-alumina are mixed at a high speed in a mass ratio of 1:0.003, loaded into a sagger, placed in a muffle furnace, introduced with oxygen, and the oxygen concentration in the furnace is controlled to reach 85%, sintered at a constant temperature of 600°C for 10 hours, and removed from the furnace after cooling. A highly dispersed single crystal NCM811 ternary material is obtained.

[0071] The scanning electron microscope image of NCM811 ternary material is as follows Figure 2 The X-ray diffraction pattern is shown in Figure 3 As shown. Figure 2 It can be seen that the single crystal particles of NCM811 ternary material are clearly dispersed and have a high degree of single crystal characteristics. Figure 3 It can be seen that each diffraction peak is sharp and the (018)(110) peaks are obviously split, indicating that the material has typical layered characteristics of positive electrode materials.

[0072] (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 applying the slurry on an aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain a positive electrode sheet; 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.

[0073] Example 2

[0074] (1) Precursor synthesis: nickel sulfate, cobalt sulfate and manganese sulfate are selected as the main materials, 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.

[0075] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution, add it to the reactor, add appropriate amount of deionized water and stir evenly, adjust the pH ratio to 12.00. Add ammonia water, control the ammonia concentration to 2 g / L, maintain the solution temperature at 40°C, and continuously introduce nitrogen as a protective gas.

[0076] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h. The stirring frequency of the reactor was 40 Hz. Ammonia water was continuously added as a complexing agent. Nitrogen was introduced to maintain the pH value of the reaction system stable at 11.50. 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. The particle size data of the dried material was tested using a Malvern particle size tester.

[0077] (4) When the precursor D50 grows horizontally to 1.5 μm, the rate of introduction of magnesium sulfate is reduced by 0.01 L / h until it stops, thereby obtaining a precursor core doped with Mg in a gradient manner, with the core D50 = 1.7 μm, and magnesium exists in the core in the form of magnesium hydroxide.

[0078] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 7 L / h, 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, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0079] (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 concentration element distribution, in which aluminum exists in the shell in the form of aluminum hydroxide.

[0080] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at a high speed, loaded into a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%, and sintered at a high temperature of 810° C. for 8 hours, and then taken out of the furnace after cooling.

[0081] (8) The above materials were mixed with nano-vanadium pentoxide at 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, cooled and removed from the furnace, and a mechanical pulverizer was used for simple mechanical dispersion to dissociate the soft agglomerates generated at high temperature.

[0082] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.004 at high speed, loaded into a sagger, placed in a muffle furnace, introduced with oxygen, controlled to have an oxygen concentration of 80%, sintered at 450°C for 10 hours, and removed from the furnace after cooling to obtain a highly dispersed single crystal NCM811 ternary material.

[0083] The scanning electron microscope image of single crystal NCM811 ternary material is as follows Figure 4 The X-ray diffraction pattern is shown in Figure 5 As shown. Figure 4 It can be seen that the single crystal particles of NCM811 ternary material are clearly dispersed and have a high degree of single crystal characteristics. Figure 5 It can be seen that each diffraction peak is sharp and the (018)(110) peaks are obviously split, indicating that the material has typical layered characteristics of positive electrode materials.

[0084] (10) Screening single crystal NCM811 ternary material, and after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly applying the slurry on an aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain a positive electrode sheet; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring them 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.

[0085] Example 3

[0086] (1) Precursor synthesis: nickel sulfate, cobalt sulfate and manganese sulfate are selected as the main materials, 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.

[0087] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution, add it to the reactor, add appropriate amount of deionized water and stir evenly, adjust the pH ratio to 12.00. Add ammonia water, control the ammonia concentration to 2 g / L, maintain the solution temperature at 40°C, and continuously introduce nitrogen as a protective gas.

[0088] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h. The stirring frequency of the reactor was 40 Hz. Ammonia water was continuously added as a complexing agent. Nitrogen was introduced to maintain the pH value of the reaction system stable at 11.70. 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.

[0089] (4) When the precursor D50 grows horizontally to 1.5 μm, the introduction rate of zirconium oxychloride is reduced by 0.01 L / h until it stops, thereby obtaining a precursor core doped with Zr in a gradient manner, with the core D50 = 1.7 μm, and zirconium exists in the core in the form of zirconium hydroxide.

[0090] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 7 L / h, 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 0.1 L / h, and the rate was increased by 0.1 L / h every hour until it reached 0.7 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, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0091] (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 concentration element distribution, in which aluminum exists in the shell in the form of aluminum hydroxide.

[0092] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at a high speed, loaded into a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%, and sintered at a high temperature of 810° C. for 8 hours, and then taken out of the furnace after cooling.

[0093] (8) The above materials were mixed with nano-vanadium pentoxide at 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, cooled and removed from the furnace, and a mechanical pulverizer was used for simple mechanical dispersion to dissociate the soft agglomerates generated at high temperature.

[0094] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.002 at high speed, put into a sagger, placed in a muffle furnace, introduced with oxygen, controlled to have an oxygen concentration of 80%, sintered at 450°C for 10 hours, and removed from the furnace after cooling to obtain a highly dispersed single crystal NCM811 ternary material.

[0095] (10) Screening single crystal NCM811 ternary material, and after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly applying the slurry on an aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain a positive electrode sheet; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring them 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.

[0096] Example 4

[0097] (1) Precursor synthesis: nickel sulfate, cobalt sulfate and manganese sulfate are selected as the main materials, 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.

[0098] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution, add it to the reactor, add appropriate amount of deionized water and stir evenly, adjust the pH ratio to 12.00. Add ammonia water, control the ammonia concentration to 2 g / L, maintain the solution temperature at 40°C, and continuously introduce nitrogen as a protective gas.

[0099] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h. The stirring frequency of the reactor was 40 Hz. Ammonia water was continuously added as a complexing agent. Nitrogen was introduced to maintain the pH value of the reaction system stable at 11.50. 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. The particle size data of the dried material was tested using a Malvern particle size tester.

[0100] (4) When the precursor D50 grows horizontally to 1.4 μm, the introduction rate of zirconium oxychloride is reduced by 0.01 L / h until it stops, thereby obtaining a precursor core doped with Zr in a gradient manner, with the core D50 = 1.6 μm, and zirconium exists in the core in the form of zirconium hydroxide.

[0101] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 7 L / h, the stirring frequency was maintained at 40 Hz, the pH value of the reactor solution was adjusted to 11.0, and 1 mol / L sodium tungstate 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 1.0 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, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0102] (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, and tungsten exists in the shell in the form of tungstate.

[0103] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at a high speed, loaded into a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%, and sintered at a high temperature of 810° C. for 8 hours, and then taken out of the furnace after cooling.

[0104] (8) The above materials were mixed with nano-B2O3 at a mass ratio of 1:0.002, 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 pulverizer was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0105] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.002 at high speed, put into a sagger, placed in a muffle furnace, introduced with oxygen, controlled to have an oxygen concentration of 80%, sintered at 450°C for 10 hours, and removed from the furnace after cooling to obtain a highly dispersed single crystal NCM811 ternary material.

[0106] (10) Screening single crystal NCM811 ternary material, and after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly applying the slurry on an aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain a positive electrode sheet; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring them 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.

[0107] Example 5

[0108] (1) Precursor synthesis: nickel sulfate, cobalt sulfate and manganese sulfate are selected as the main materials, 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.

[0109] (2) Precipitation alkali solution: Select 9 mol / L sodium hydroxide solution, add it to the reactor, add appropriate amount of deionized water and stir evenly, adjust the pH ratio to 12.00. Add ammonia water, control the ammonia concentration to 2 g / L, maintain the solution temperature at 40°C, and continuously introduce nitrogen as a protective gas.

[0110] (3) The metal salt solution described in (1) above was added to the reactor at a flow rate of 3.5 L / h. The stirring frequency of the reactor was 40 Hz. Ammonia water was continuously added as a complexing agent. Nitrogen was introduced to maintain the pH value of the reaction system stable at 11.50. 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. The particle size data of the dried material was tested using a Malvern particle size tester.

[0111] (4) When the precursor D50 grows horizontally to 1.4 μm, the introduction rate of zirconium oxychloride is reduced by 0.01 L / h until it stops, thereby obtaining a precursor core doped with Zr in a gradient manner, with the core D50 = 1.6 μm, and zirconium exists in the core in the form of zirconium hydroxide.

[0112] (5) The flow rate of the nickel-cobalt-manganese salt solution was increased to 6 L / h, the stirring frequency was maintained at 40 Hz, the pH value of the reactor solution 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, and the particle size data of the dried material was tested using a Malvern particle size tester.

[0113] (6) When the D50 of the precursor is 1.9 μm, the reaction is stopped. The slurry in the reaction kettle is centrifuged, filtered, washed, dried, and sieved to obtain a ternary precursor with a special structure and a double gradient concentration element distribution.

[0114] (7) The obtained precursor was mixed with lithium hydroxide and zirconium dioxide at a molar ratio of 1:1.03:0.001 at a high speed, loaded into a sagger and placed in a muffle furnace, oxygen was introduced, and the oxygen concentration in the furnace was controlled to reach 95%, and sintered at a high temperature of 810° C. for 8 hours, and then taken out of the furnace after cooling.

[0115] (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, introduced with oxygen, and the oxygen concentration in the furnace was controlled to reach 95%. The mixture was sintered at 870°C for 10 hours, cooled and removed from the furnace, and a mechanical pulverizer was used for simple mechanical dispersion to dissociate the soft agglomerates produced at high temperature.

[0116] (9) The above materials were mixed with nano-titanium dioxide at a molar ratio of 1:0.0015 at high speed, put into a sagger, placed in a muffle furnace, introduced with oxygen, controlled to have an oxygen concentration of 80%, sintered at 450°C for 10 hours, and removed from the furnace after cooling to obtain a highly dispersed single crystal NCM811 ternary material.

[0117] (10) Screening single crystal NCM811 ternary material, and after screening, uniformly mixing it with PVDF and conductive carbon black in a ratio of 94:3:3 to obtain positive electrode slurry, evenly applying the slurry on an aluminum foil, drying it in an oven at a temperature of 130°C, and then rolling it to obtain a positive electrode sheet; using a cutting machine to cut out discs with a diameter of 14 mm, vacuum drying for 14 hours, and then transferring them 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.

[0118] Performance Testing:

[0119] The button cells of Examples 1 to 5 were evaluated for electrical performance using the Wuhan Blue Electric Battery Test System (Model: CT3001A), and the discharge capacity was tested at a voltage of 3.0 to 4.30 V at a rate of 0.1C; the capacity retention rate was tested after 50 cycles of cyclic charge and discharge at a rate of 0.1C at room temperature. The test results of Examples 1 to 5 are shown in the following table.

[0120] project Discharge capacity Capacity retention after 50 cycles Example 1 200.3mAh / g 97.9％ Example 2 199.2mAh / g 97.4％ Example 3 200.5mAh / g 96.8％ Example 4 198.8mAh / g 97.1％ Example 5 198.3mAh / g 97.5％

[0121] 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.

[0122] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

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 oxides or hydroxides of nickel cobalt manganese. The chemical formula of the hydroxide of nickel cobalt manganese is Ni x Co y Mn z (OH)2, and the chemical formula of the oxide of nickel cobalt manganese is Ni x Co y Mn z O, where 0.33 ≤ x < 1.0, 0 < y ≤ 0.33, x + y + z = 1, and z is not equal to 0; 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; 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. A method for preparing a positive electrode active material, characterized in that: include: The precursor of the positive electrode active material according to any one of claims 1 to 5 and the lithium source are sintered once, the temperature range of the primary sintering is 600-950° C., and the atmosphere is air or a high-purity oxygen atmosphere; The product of the primary sintering is mixed with an active inhibitor for secondary sintering, wherein the temperature range of the secondary sintering is 300-850° C. and the atmosphere is a high-purity oxygen atmosphere; 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.

7. The method for preparing the positive electrode active material according to claim 6, 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).

8. The method for preparing a positive electrode active material according to claim 6, 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).

9. A positive electrode active material, characterized in that: The method according to claim 6 is used to prepare the product.

10. 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 6.

11. 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 10.

12. A method for preparing a precursor of a positive electrode active material according to any one of claims 1 to 5, 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; Stop the reaction, centrifuge, filter, wash, dry and screen the slurry in the reaction container to obtain precursor particles. When the material of the precursor particles is nickel-cobalt-manganese hydroxide, the drying temperature does not exceed 200°C. When the material of the precursor particles is nickel-cobalt-manganese oxide, the drying temperature reaches 400-500°C.

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