阅读说明：本技术 一种多层铝掺杂的镍钴锰前驱体及其制备方法 (Multilayer aluminum-doped nickel-cobalt-manganese precursor and preparation method thereof ) 是由 谢池朋 陈九华 胡进 杨志 于 2021-08-25 设计创作，主要内容包括：一种多层铝掺杂的镍钴锰前驱体,为核壳结构,以未掺铝的镍钴锰氢氧化物为内核,内核表面依次覆有交替结构的掺铝的镍钴锰氢氧化物层和未掺铝的镍钴锰氢氧化物层,且镍钴锰前驱体的最外层是掺铝的镍钴锰氢氧化物层。其制备方法：先向反应釜中加入氨水作为反应底液,通入氮气,开启搅拌,将金属盐混合液、沉淀剂、络合剂并流加入反应釜中反应,直至生成的颗粒的粒径达到内核粒径；通入偏铝酸钠溶液,在内核表面生成的掺铝的镍钴锰氢氧化物层；停止通入偏铝酸钠溶液,在掺铝的镍钴锰氢氧化物层表面生成未掺铝的镍钴锰氢氧化物层；如此反复,直至生成设计结构的多层铝掺杂的镍钴锰前驱体。本发明中的镍钴锰前驱体具有较好的热稳定性和结构稳定性。(A multi-layer aluminum-doped nickel-cobalt-manganese precursor is of a core-shell structure, wherein a nickel-cobalt-manganese hydroxide which is not doped with aluminum is used as an inner core, the surface of the inner core is sequentially covered with an aluminum-doped nickel-cobalt-manganese hydroxide layer and an aluminum-non-doped nickel-cobalt-manganese hydroxide layer which are of an alternating structure, and the outmost layer of the nickel-cobalt-manganese precursor is the aluminum-doped nickel-cobalt-manganese hydroxide layer. The preparation method comprises the following steps: firstly, adding ammonia water into a reaction kettle to serve as reaction base liquid, introducing nitrogen, starting stirring, adding the metal salt mixed liquid, a precipitator and a complexing agent into the reaction kettle in a parallel flow manner for reaction until the particle size of generated particles reaches the particle size of a kernel; introducing a sodium metaaluminate solution to generate an aluminum-doped nickel-cobalt-manganese hydroxide layer on the surface of the inner core; stopping introducing the sodium metaaluminate solution, and generating an aluminum-undoped nickel-cobalt-manganese hydroxide layer on the surface of the aluminum-doped nickel-cobalt-manganese hydroxide layer; repeating the steps until a multilayer aluminum-doped nickel-cobalt-manganese precursor with a designed structure is generated. The nickel-cobalt-manganese precursor has better thermal stability and structural stability.)

1. The multilayer aluminum-doped nickel-cobalt-manganese precursor is characterized in that the nickel-cobalt-manganese precursor is of a core-shell structure, the nickel-cobalt-manganese precursor takes nickel-cobalt-manganese hydroxide which is not doped with aluminum as an inner core, the surface of the inner core is sequentially covered with aluminum-doped nickel-cobalt-manganese hydroxide layers and nickel-cobalt-manganese hydroxide layers which are not doped with aluminum in an alternating structure, and the outmost layer of the nickel-cobalt-manganese precursor is the aluminum-doped nickel-cobalt-manganese hydroxide layer.

2. The multi-layer aluminum-doped nickel cobalt manganese precursor of claim 1 wherein the total number of layers of aluminum-doped nickel cobalt manganese hydroxide and non-aluminum-doped nickel cobalt manganese hydroxide of the alternating structure is 3 to 9.

3. The multi-layer aluminum-doped nickel cobalt manganese precursor of claim 1 wherein the diameter of the inner core is 1 to 6 μm and the thickness of the aluminum-doped nickel cobalt manganese hydroxide layer and the non-aluminum-doped nickel cobalt manganese hydroxide layer is 0.5 to 4 μm.

4. The multi-layer aluminum-doped nickel-cobalt-manganese precursor of claim 1, wherein the multi-layer aluminum-doped nickel-cobalt-manganese precursor has a formula of Ni_aCo_bMn_cAl_1-a-b-c(OH)₂Wherein a is more than or equal to 0.8 and less than 1, b is more than 0 and less than 0.2, c is more than 0 and less than 0.2, and 1-a-b-c is more than or equal to 0.001 and less than or equal to 0.05; the percentage of nickel element in each layer of material of the multi-layer aluminum-doped nickel-cobalt-manganese precursor to the total number of moles of nickel, cobalt and manganese in each layer of material is not lower than 80%, and the percentage of aluminum element in the aluminum-doped nickel-cobalt-manganese hydroxide layer to the total number of moles of nickel, cobalt, manganese and aluminum in the aluminum-doped nickel-cobalt-manganese hydroxide layer is not higher than 5%; the chemical formula of the inner core is Ni_xCo_yMn_1-x-y(OH)₂Wherein x is more than 0.8 and less than 1, and y is more than 0 and less than 0.2.

5. The multi-layered aluminum-doped nickel-cobalt-manganese precursor of claim 1, wherein the nickel-cobalt-manganese precursor has a secondary particle size D10 of not less than 3 μm, a particle size D50 of 13-20 μm, a particle size D90 of not more than 50 μm, a tap density of 1.8g/cm 0.1 < (D90-D10)/D50 < 1³-2.5g/cm³Specific surface area of 2m²/g-15m²The Na content is less than or equal to 200ppm and the S content is less than or equal to 2000 ppm.

6. A method of preparing the multilayer aluminum doped nickel cobalt manganese precursor of any of claims 1 to 5 comprising the steps of:

(1) preparing a metal salt mixed solution with the total metal ion concentration of 0.1-2 mol/L from soluble nickel salt, soluble cobalt salt and soluble manganese salt according to the stoichiometric ratio of the inner core;

(2) adding ammonia water into a reaction kettle to serve as reaction base liquid, introducing nitrogen, starting stirring, adding the metal salt mixed liquid prepared in the step (1), a precipitator and a complexing agent into the reaction kettle in a parallel flow manner for reaction until the particle size of particles generated by the reaction reaches the kernel particle size;

(3) keeping the state of continuously introducing the metal salt mixed solution, the precipitator and the complexing agent, and introducing a sodium metaaluminate solution with the aluminum ion concentration of 0.01-0.5 mol/L until the aluminum-doped nickel-cobalt-manganese hydroxide layer generated on the surface of the inner core reaches the designed thickness;

(4) continuously keeping the state of continuously introducing the metal salt mixed solution, the precipitator and the complexing agent, and not introducing the sodium metaaluminate solution until an aluminum-free nickel-cobalt-manganese hydroxide layer with the designed thickness is generated on the surface of the aluminum-doped nickel-cobalt-manganese hydroxide layer;

(5) repeating the operation of the step (3) and the operation of the step (4) for a plurality of times, and finally repeating the operation of the step (3) for one time until an aluminum-doped nickel-cobalt-manganese hydroxide layer of the outermost layer of the nickel-cobalt-manganese precursor with the designed thickness is generated, so as to obtain precursor slurry;

(6) and washing and drying the precursor slurry to obtain the multilayer aluminum-doped nickel-cobalt-manganese precursor.

7. The method according to claim 6, wherein in the step (2), the precipitant is 400g/L NaOH solution and the complexing agent is 40-140g/L ammonia water.

8. The method according to claim 7, wherein in the step (2), the feed flow rate of the metal salt mixture is 1 to 10L/h, the feed flow rate of the sodium hydroxide solution is 0.2 to 3L/h, and the feed flow rate of the aqueous ammonia is 0.1 to 1.5L/h; in the reaction process, the ammonia water concentration in the reaction bottom liquid is controlled to be 2-15g/L, the pH value of the reaction bottom liquid is 11-13, the stirring speed is controlled to be 100-600rpm, and the reaction temperature is 45-65 ℃.

9. The production method according to claim 7, wherein in the step (3), the pH of the reaction system is controlled to 11 to 13.

10. The preparation method according to claim 7, wherein in the step (1), the soluble nickel salt is selected from one or more of nickel sulfate, nickel nitrate, nickel carbonate and nickel acetate; the soluble manganese salt is selected from one or more of manganese sulfate, manganese nitrate, manganese carbonate and manganese acetate; the soluble cobalt salt is selected from one or more of cobalt sulfate, cobalt nitrate and cobalt acetate.

Technical Field

The invention belongs to the field of lithium ion batteries, and particularly relates to a multilayer aluminum-doped nickel-cobalt-manganese precursor and a preparation method thereof.

Background

Compared with other traditional secondary batteries, the lithium ion battery has the advantages of high energy density, long cycle life, environmental protection and the like, and is widely applied to the fields of 3C electronic products and electric automobiles. The nickel-cobalt-manganese ternary cathode material is the most promising lithium ion battery cathode material due to high reversible capacity, long cycle performance and high operating voltage. The capacity of the existing nickel-cobalt-manganese ternary cathode material is further improved by increasing the content of nickel, but the cycle performance is reduced and the thermal stability is deteriorated due to excessive nickel enrichment, so that potential safety hazards exist. At present, in order to eliminate the negative effect caused by high nickel, researchers find that metal ion modification in NCM is a very effective method by technical means of improving structural stability, reducing cation shuffling and the like. In various modified metals, the modification of aluminum can stabilize the crystal structure of NCM, and obviously inhibit the exothermic reaction in the charge-discharge process, thereby improving the cycle performance and the overcharge resistance of the material.

Chinese patent CN107316990A discloses a method for preparing an aluminum hydroxide coated nickel-cobalt positive electrode material precursor, which comprises first synthesizing a spherical nickel-cobalt hydroxide core in a reaction kettle, and then coating a layer of aluminum hydroxide on the surface of the core, wherein although the aluminum coating can inhibit the exothermic reaction during charging and discharging, and improve the structural stability, the aluminum hydroxide shell does not provide effective capacity, and the coating of a certain thickness can prevent the deintercalation of lithium ions in the positive electrode material. Therefore, how to further improve the distribution form of aluminum to further improve the thermal stability and structural stability of the material is a technical problem to be solved.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects and shortcomings in the background technology and provides a multilayer aluminum-doped nickel-cobalt-manganese precursor with good thermal stability and structural stability and a preparation method thereof.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

the utility model provides a multilayer aluminium-doped nickel cobalt manganese precursor, nickel cobalt manganese precursor uses the nickel cobalt manganese hydroxide that does not mix the aluminium as the kernel, the kernel surface covers in proper order has aluminium-doped nickel cobalt manganese hydroxide layer and the nickel cobalt manganese hydroxide layer that does not mix the aluminium, wherein, the outmost of nickel cobalt manganese precursor is aluminium-doped nickel cobalt manganese hydroxide layer.

In the above multilayer aluminum-doped nickel-cobalt-manganese precursor, preferably, the total number of the aluminum-doped nickel-cobalt-manganese hydroxide layers and the non-aluminum-doped nickel-cobalt-manganese hydroxide layers with the alternating structure is 3 to 9.

In the above multilayer aluminum-doped nickel-cobalt-manganese precursor, preferably, the diameter of the inner core is 1 to 6 μm, and the thicknesses of the aluminum-doped nickel-cobalt-manganese hydroxide layer and the non-aluminum-doped nickel-cobalt-manganese hydroxide layer are 0.5 to 4 μm.

Preferably, the multilayer aluminum-doped nickel-cobalt-manganese precursor has a general formula of Ni_aCo_bMn_cAl_1-a-b-c(OH)₂Wherein a is more than or equal to 0.8 and less than 1, b is more than 0 and less than 0.2, c is more than 0 and less than 0.2, and 1-a-b-c is more than or equal to 0.001 and less than or equal to 0.05; the percentage of nickel element in each layer of material of the multi-layer aluminum-doped nickel-cobalt-manganese precursor to the total number of moles of nickel, cobalt and manganese in each layer of material is not lower than 80%, and the percentage of aluminum element in the aluminum-doped nickel-cobalt-manganese hydroxide layer to the total number of moles of nickel, cobalt, manganese and aluminum in the aluminum-doped nickel-cobalt-manganese hydroxide layer is not higher than 5%; the chemical formula of the inner core is Ni_xCo_yMn_1-x-y(OH)₂Wherein x is more than 0.8 and less than 1, and y is more than 0 and less than 0.2.

The above multi-layer Al-doped Ni-Co-Mn precursor preferably has a secondary particle size D10 of not less than 3 μm, a particle size D50 of 13-20 μm, a particle size D90 of not more than 50 μm, 0.1 < (D90-D10)/D50 < 1, and a tap density of 1.8g/cm³-2.5g/cm³Specific surface area of 2m²/g-15m²The Na content is less than or equal to 200ppm and the S content is less than or equal to 2000 ppm.

As a general concept, the present invention also provides a preparation method of the above multilayer aluminum-doped nickel-cobalt-manganese precursor, comprising the steps of:

(1) preparing a metal salt mixed solution with the metal ion concentration of 0.1-2 mol/L from soluble nickel salt, soluble cobalt salt and soluble manganese salt according to the stoichiometric ratio of the inner core;

(2) adding ammonia water into a reaction kettle to serve as reaction base liquid, introducing nitrogen, starting stirring, adding the metal salt mixed liquid prepared in the step (1), a precipitator and a complexing agent into the reaction kettle in a parallel flow manner for reaction until the particle size of particles generated by the reaction reaches the kernel particle size;

(3) keeping the state of continuously introducing the metal salt mixed solution, the precipitator and the complexing agent, and introducing a sodium metaaluminate solution with the aluminum ion concentration of 0.01-0.5 mol/L until the aluminum-doped nickel-cobalt-manganese hydroxide layer generated on the surface of the inner core reaches the designed thickness;

(4) keeping the state of continuously introducing the metal salt mixed solution, the precipitator and the complexing agent, and not introducing the sodium metaaluminate solution until an aluminum-undoped nickel-cobalt-manganese hydroxide layer with a designed thickness is generated on the surface of the aluminum-doped nickel-cobalt-manganese hydroxide layer;

(5) repeating the operation of the step (3) and the operation of the step (4) for a plurality of times, and finally repeating the operation of the step (3) for one time until an aluminum-doped nickel-cobalt-manganese hydroxide layer of the outermost layer of the nickel-cobalt-manganese precursor with the designed thickness is generated, so as to obtain precursor slurry;

(6) and washing and drying the precursor slurry to obtain the multilayer aluminum-doped nickel-cobalt-manganese precursor.

In the preparation method, preferably, in the step (2), the precipitant is a sodium hydroxide solution with a concentration of 100-400g/L, and the complexing agent is ammonia water with a concentration of 40-140 g/L.

In the preparation method, preferably, in the step (2), the feeding flow rate of the metal salt mixed solution is 1-10L/h, the feeding flow rate of the sodium hydroxide solution is 0.2-3L/h, and the feeding flow rate of the ammonia water is 0.1-1.5L/h; in the reaction process, the ammonia water concentration in the reaction bottom liquid is controlled to be 2-15g/L, the pH value of the reaction bottom liquid is 11-13, the stirring speed is controlled to be 100-600rpm, and the reaction temperature is 45-65 ℃.

In the above production method, preferably, in the step (3), the pH of the reaction system is controlled to 11 to 13.

In the above preparation method, preferably, in the step (1), the soluble nickel salt is selected from one or more of nickel sulfate, nickel nitrate, nickel carbonate and nickel acetate; the soluble manganese salt is selected from one or more of manganese sulfate, manganese nitrate, manganese carbonate and manganese acetate; the soluble cobalt salt is selected from one or more of cobalt sulfate, cobalt nitrate and cobalt acetate.

In the above preparation method, preferably, in the step (4), the sodium metaaluminate solution is prepared from soluble aluminum salt, sodium hydroxide and deionized water, the soluble aluminum salt is selected from one or more of aluminum sulfate, aluminum nitrate, aluminum carbonate and aluminum acetate, the sodium hydroxide is in excess, which is beneficial to inhibiting the sodium metaaluminate from hydrolyzing into aluminum hydroxide precipitate, and the excess degree of the sodium hydroxide relative to the soluble aluminum salt is 15 < n (OH) (OH is greater than n)^-1)：n(Al³⁺)＜40。

Compared with the prior art, the invention has the advantages that:

(1) the outermost layer of the nickel-cobalt-manganese precursor is an aluminum-doped nickel-cobalt-manganese hydroxide layer, so that the thermal stability and the structural stability of the precursor can be improved; the middle coating layer relates to an aluminum-doped nickel-cobalt-manganese hydroxide layer and an aluminum-undoped nickel-cobalt-manganese hydroxide layer with an alternate structure, a plurality of aluminum doping layers with stable structures are provided from inside to outside, the aluminum doping layers are dependent on abundant Al-O bonds to inhibit the damage of external force to the structures, even if the aluminum doping layers of the precursor shell are damaged, the aluminum doping layers are still arranged at a plurality of intervals inside, and the thermal stability and the structural stability of the material are improved under the condition that the aluminum doping amount is certain.

(2) The aluminum doping can play a role in inhibiting the dissolution of transition metal elements, but the aluminum-doped anode material has the pulverization and crushing phenomena of secondary particles in long-term circulation, so the invention can reduce the influence of the pulverization and crushing phenomena of the secondary particles on the structural stability of the material in long-term circulation and improve the cycle performance of the anode material prepared by the precursor by arranging the shell structure with the aluminum-doped nickel-cobalt-manganese hydroxide layer and the non-aluminum-doped nickel-cobalt-manganese hydroxide layer on the surface of the inner core material.

(3) In the preparation process of the invention, mixed metal salt is continuously pumped into ammonia water base solution, and coprecipitation reaction is carried out in inert gas environment by taking sodium hydroxide as precipitator and ammonia water as complexing agent,then, sodium metaaluminate solution is added in stages according to the increase of the particle size D50, the aluminum metaaluminate is slowly hydrolyzed to release Al³⁺Slow down Al³⁺Thereby precipitating Ni²⁺、Co^{2 +}、Mn²⁺、Al³⁺The aim of coprecipitation is achieved at the plurality of intermediate layers and the shell layers, the nickel-cobalt-manganese precursor with a plurality of layers of aluminum doping is finally synthesized, particles are tightly connected from inside to outside, and the structural stability of the material is improved.

(4) The nickel-cobalt-manganese precursor has a shell layer with a multilayer structure, the outmost layer is an aluminum-doped nickel-cobalt-manganese hydroxide layer, compared with aluminum oxide coating, the lithium ion conduction is more facilitated, the nickel element in each layer of material accounts for not less than 80% of the total mole number of nickel, cobalt and manganese in each layer of material, the integral nickel content is high, and meanwhile, the nickel-cobalt-manganese precursor is convenient to design into a structure with uniform nickel distribution, so that the further prepared anode material has high capacity.

(5) The preparation process is simple, and the precursor with the initially designed metal element ratio can be produced more stably.

Drawings

Fig. 1 is a scanning electron microscope image of a three-layer aluminum-doped nickel-cobalt-manganese precursor material prepared in example 1.

Fig. 2 is a cross-sectional scanning electron microscope image of the three-layer aluminum-doped nickel-cobalt-manganese precursor material prepared in example 1.

Fig. 3 is a TG weight versus DSC heat curve for the three-layer aluminum-doped nickel-cobalt-manganese precursor material prepared in example 1.

Fig. 4 is a scanning electron microscope image of the two-layer aluminum-doped nickel-cobalt-manganese precursor material prepared in example 2.

Fig. 5 is a cross-sectional scanning electron microscope image of the two-layer aluminum-doped nickel-cobalt-manganese precursor material prepared in example 2.

Fig. 6 is a TG weight versus DSC heat curve for the two-layer aluminum-doped nickel-cobalt-manganese precursor material prepared in example 2.

Fig. 7 is a scanning electron microscope image of the nickel-cobalt-manganese precursor material with the core-shell structure prepared in comparative example 1.

Fig. 8 is a cross-sectional scanning electron microscope image of the nickel-cobalt-manganese precursor material with a uniform core-shell structure prepared in comparative example 1.

Fig. 9 is a graph of TG weight versus DSC heat for the nickel-cobalt-manganese precursor material of core-shell structure prepared in comparative example 1.

Fig. 10 is a scanning electron micrograph of an undoped nickel-cobalt-manganese precursor material prepared in comparative example 2.

Fig. 11 is a cross-sectional scanning electron micrograph of an undoped nickel cobalt manganese precursor material prepared in comparative example 2.

Fig. 12 is a graph of TG weight versus DSC heat for an undoped nickel cobalt manganese precursor material prepared in comparative example 2.

Detailed Description

In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1:

a multi-layer Al-doped Ni-Co-Mn precursor is prepared from Ni-Co-Mn hydroxide Ni not doped with Al_0.885Co_0.09Mn_0.025(OH)₂The core was about 4.5 μm D50, and the surface of the core was coated with a first layer of aluminum-doped NiCoMnOH Ni of about 1.5 μm thickness_0.867Co_0.088Mn_0.025Al_0.002(OH)₂A first non-doped Ni-Co-Mn-OH layer Ni with a thickness of about 2 μm_0.885Co_0.09Mn_0.025(OH)₂A second Al-doped NiCoMn hydroxide layer Ni with a thickness of about 2 μm_0.867Co_0.088Mn_0.025Al_0.002(OH)₂A second non-doped Ni-Co-Mn-OH layer Ni with a thickness of about 2 μm_0.885Co_0.09Mn_0.025(OH)₂And an outermost layer of about 1.5 μm thickness, a third aluminum-doped nickel cobalt manganese hydroxide layer Ni_0.867Co_0.088Mn_0.025Al_0.002(OH)₂(ii) a Wherein the secondary particle size D10 of the multi-layer aluminum-doped nickel-cobalt-manganese precursor is 8.69 mu m, the particle size D50 is 13.56 mu m, the particle size D90 is 16.94 mu m, the particle size distribution (D90-D10)/D50 is 0.6, and the tap density is 1.94g/cm³A specific surface area of 12.2m²And g, the Na content is 65ppm, and the S content is 1123 ppm.

The preparation method of the multilayer aluminum-doped nickel-cobalt-manganese precursor of the embodiment comprises the following steps:

(1) preparation of raw materials:

mixing nickel sulfate, cobalt sulfate and manganese sulfate, adding deionized water, and preparing into 1.8mol/L metal mixed salt solution, wherein the element molar ratio of nickel, cobalt and manganese in the metal mixed salt solution is 88.5:9: 2.5;

adding aluminum sulfate octadecahydrate into a mixed solution of pure water and sodium hydroxide to prepare a 5mol/L sodium metaaluminate solution, wherein the excessive degree of the sodium hydroxide relative to the aluminum sulfate octadecahydrate is n (OH)^-1)：n(Al³⁺)＝25；

Adding ammonia water into deionized water to prepare an ammonia water solution with the concentration of 100 g/L;

sodium hydroxide was added to deionized water to prepare a 300g/L sodium hydroxide solution.

(2) Preparing a multilayer core-shell structure NCM ternary precursor material:

adding 80L of deionized water, 100mL of sodium hydroxide solution and 4L of ammonia water into a 100L reaction kettle, opening and stirring at the rotation speed of 400r/min and the constant temperature of 52 ℃ to obtain a base solution with the pH value of 11.75 +/-0.5, and continuously introducing nitrogen with the flow of 4L/min;

the first stage of growth: respectively introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle with prepared base solution at the flow rates of 30mL/min, 10mL/min and 5mL/min for reaction for 3 hours, wherein the rotating speed of a stirrer of the reaction kettle is 400r/min in the reaction process, the pH value is 11.8-11.9 in the reaction process, and the ammonia value is 7-8 g/L; after the reaction is finished, discharging the mother liquor, treating the mother liquor by using concentration equipment, and returning the mother liquor to the reaction kettle to obtain a nickel-cobalt-manganese hydroxide inner core with the medium particle size D50 of 4.5 +/-0.5 mu m;

and a second growth stage: changing the flow rates of a metal salt solution, a sodium hydroxide solution and ammonia water, introducing a sodium metaaluminate solution, wherein the flow rates of the metal salt solution, the sodium metaaluminate solution, the sodium hydroxide solution and the ammonia water are respectively 50mL/min, 17mL/min, 16mL/min and 6mL/min, introducing the raw materials into a reaction kettle for continuous reaction and precipitation, wherein the rotating speed of a stirrer is 380r/min until the medium particle diameter D50 of the materials in the reaction kettle is 6 +/-0.3 mu m, discharging a mother solution, treating the mother solution by a concentration device, and returning the mother solution to the reaction kettle;

and a third growth stage: stopping introducing the sodium metaaluminate solution, introducing the metal salt solution, the sodium hydroxide solution and the ammonia water into the reaction kettle at 50mL/min, 18mL/min and 6mL/min respectively to continue reaction and precipitation, controlling the rotating speed of a stirrer to be 260r/min until the medium particle size D50 of the reaction material is 8 +/-0.3 mu m, discharging the mother liquor, treating the mother liquor by using concentration equipment, and returning the mother liquor to the reaction kettle;

and a fourth stage of growth: introducing the sodium metaaluminate solution again, introducing the metal salt solution, the sodium metaaluminate, the sodium hydroxide solution and the ammonia water into the reaction kettle at the speed of 50mL/min, 17mL/min, 16mL/min and 6mL/min respectively to continue reaction and precipitation, controlling the rotating speed of a stirrer to be 200r/min until the medium particle size D50 of the reaction material is 10 +/-0.3 mu m, discharging the mother liquor, treating the mother liquor by using concentration equipment and returning the mother liquor to the reaction kettle;

and a fifth growth stage: stopping introducing the sodium metaaluminate solution, introducing the metal salt solution, the sodium hydroxide solution and the ammonia water into the reaction kettle at the speed of 100mL/min, 40mL/min and 15mL/min respectively to continue reaction and precipitation, controlling the rotating speed of the stirrer to be 140r/min until the median particle size D50 of the reaction material is 12 +/-0.3 mu m, discharging the mother liquor, treating the mother liquor by using concentration equipment, and returning the mother liquor to the reaction kettle;

and a sixth growth stage: introducing the sodium metaaluminate solution again, introducing the metal salt solution, the sodium metaaluminate, the sodium hydroxide solution and the ammonia water into the reaction kettle at the speed of 100mL/min, 35mL/min, 30mL/min and 10mL/min respectively to continue reaction and precipitation, controlling the rotating speed of the stirrer to be 120r/min until the medium particle size D50 of the reaction material is 13.5 +/-0.5 mu m, and stopping feeding to ensure that the solid content of the reaction kettle is lower than 500 g/L; after the reaction is finished, discharging the mother liquor, treating the mother liquor by using concentration equipment, and returning the mother liquor to the reaction kettle to obtain nickel-cobalt-manganese precursor slurry;

putting the nickel-cobalt-manganese precursor slurry into a slurry washing kettle, draining supernatant, soaking for 3h by using 3mol/L alkali liquor, washing 1kg of solid product with 0.5L of 3mol/L alkali liquor twice, washing for many times until the washing conductivity is lower than 50us/cm, then carrying out filter pressing, loading a filter cake into a tray, carrying out vacuum drying at the drying temperature of 130 ℃, the drying time of 24h, and the moisture of the dried material is lower than 0.05%, and screening for removing iron to obtain the multilayer aluminum-doped nickel-cobalt-manganese precursor.

The scanning electron microscope image of the multilayer aluminum-doped nickel-cobalt-manganese precursor prepared in the embodiment is shown in fig. 1, the cross-sectional scanning electron microscope image is shown in fig. 2, and the cross-sectional scanning electron microscope image shows that the precursor material has a radially-arranged internal structure; the graph of TG weight versus DSC heat is shown in fig. 3, the test condition is air atmosphere, data are collected at a scanning rate of 10 ℃/min within a temperature range from room temperature to 700 ℃, analysis is performed according to the TG weight curve, a free water loss process occurs before 270 ℃, decomposition of a substance into an oxide precursor starts to occur at 270 ℃, analysis is performed according to the DSC heat curve, the peak temperature of thermal failure of the precursor material is 298.12 ℃, indicating that the multilayer aluminum-doped nickel-cobalt-manganese precursor of the present invention has better thermal stability.

Example 2:

a multi-layer Al-doped Ni-Co-Mn precursor is prepared from Ni-Co-Mn hydroxide Ni not doped with Al_0.885Co_0.09Mn_0.025(OH)₂The core was about 4.5 μm D50, and the surface of the core was coated with a first Ni-Co-Mn hydroxide layer of about 3.5 μm thickness_0.867Co_0.088Mn_0.025Al_0.002(OH)₂A first non-doped Ni-Co-Mn-OH layer Ni with a thickness of about 3 μm_0.885Co_0.09Mn_0.025(OH)₂A second aluminum-doped layer having a thickness of about 2.5 μmNi-Co-Mn-hydroxide layer Ni_0.867Co_0.088Mn_0.025Al_0.002(OH)₂(ii) a The secondary particle size D10 of the multilayer aluminum-doped nickel-cobalt-manganese precursor is 8.67 mu m, the particle size D50 is 13.73 mu m, the particle size D90 is 17.41 mu m, the particle size distribution (D90-D10)/D50 is 0.64, and the tap density is 2.04g/cm³Specific surface area of 8.67m²And g, the Na content is 87ppm, and the S content is 1250 ppm.

The preparation method of the multilayer aluminum-doped nickel-cobalt-manganese precursor of the embodiment comprises the following steps:

(1) preparation of raw materials:

mixing nickel sulfate, cobalt sulfate and manganese sulfate, adding deionized water, and preparing into 1.8mol/L metal mixed salt solution, wherein the element molar ratio of nickel, cobalt and manganese is 88.5:9: 2.5;

adding aluminum sulfate octadecahydrate into a mixed solution of pure water and sodium hydroxide to prepare a sodium metaaluminate solution with the concentration of 5mol/L, wherein the excessive degree of the sodium hydroxide relative to the aluminum sulfate octadecahydrate is n (OH)^-1)：n(Al³⁺)＝25；

Adding ammonia water into deionized water to prepare an ammonia water solution with the concentration of 100 g/L; adding sodium hydroxide into deionized water to prepare a 300g/L sodium hydroxide solution;

(2) preparing a multilayer core-shell structure NCM ternary precursor material:

adding 80L of deionized water, 60mL of sodium hydroxide solution and 6L of ammonia water into a 100L reaction kettle, opening and stirring at the rotation speed of 450r/min and the constant temperature of 60 ℃ to obtain a base solution with the pH value of 11.55 +/-0.5, and continuously introducing nitrogen at the flow rate of 4L/min;

the first stage of growth: respectively introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle with prepared base solution at the flow rates of 30mL/min, 10mL/min and 5mL/min for reaction for 3 hours, wherein the rotating speed of a stirrer is controlled to be 450r/min, the pH value is 11.5-11.6, and the ammonia value is 7-8g/L in the reaction process; discharging the reaction mother liquor, carrying out solid-liquid separation by using concentration equipment, and returning the solid to the reaction kettle to obtain a nickel-cobalt-manganese hydroxide inner core with the medium particle size D50 of 4.5 +/-0.5 mu m;

and a second growth stage: changing the flow rates of a metal salt solution, a sodium hydroxide solution and ammonia water, introducing a sodium metaaluminate solution, introducing the metal salt solution, the sodium metaaluminate, the sodium hydroxide solution and the ammonia water into a reaction kettle at 50mL/min, 17mL/min, 16mL/min and 6mL/min respectively to continue reaction and precipitation, controlling the rotating speed of a stirrer to be 380r/min, discharging a reaction mother liquor when the medium particle size D50 is 6 +/-0.3 mu m, performing solid-liquid separation through a concentration device, returning the solid to the reaction kettle, and continuing stirring at the rotating speed of 260r/min until the medium particle size D50 is 8 +/-0.3 mu m;

and a third growth stage: stopping introducing the sodium metaaluminate solution, introducing the metal salt solution, the sodium hydroxide solution and the ammonia water into the reaction kettle at 100mL/min, 40mL/min and 15mL/min respectively to continue reaction and precipitation, controlling the rotating speed of the stirrer to be 200r/min, discharging the reaction mother liquor when the medium particle diameter D50 is 9.5 +/-0.3 mu m, performing solid-liquid separation through concentration equipment, returning the solid to the reaction kettle, continuously stirring at the rotating speed of 160r/min, discharging the mother liquor through the concentration equipment, and reacting until the medium particle diameter D50 is 11 +/-0.3 mu m;

and a fourth stage of growth: and continuously introducing a sodium metaaluminate solution, introducing a metal salt solution, the sodium metaaluminate solution, a sodium hydroxide solution and ammonia water into the reaction kettle at the speed of 100mL/min, 35mL/min, 30mL/min and 10mL/min respectively for continuous reaction and precipitation, discharging the mother liquor through concentration equipment, reacting until the medium particle diameter D50 is 13.5 +/-0.5 mu m, stopping feeding, and enabling the solid content of the stopped kettle to be lower than 400g/L to obtain the nickel-cobalt-manganese precursor slurry.

Putting the nickel-cobalt-manganese precursor slurry into a slurry washing kettle, draining supernatant, soaking for 3h by using 3mol/L alkali liquor, washing 1kg of solid product with 1L of 3mol/L alkali liquor twice, washing for many times until the washing conductivity is lower than 50us/cm, then carrying out filter pressing, loading filter cakes into a tray, drying in a vacuum oven at the drying temperature of 130 ℃ for 24h, and screening for removing iron after the moisture of the dried material is lower than 0.05%, thereby obtaining the multilayer aluminum-doped nickel-cobalt-manganese precursor.

The scanning electron microscope image of the multilayer aluminum-doped nickel-cobalt-manganese precursor prepared in this example is shown in fig. 4, the cross-sectional scanning electron microscope image is shown in fig. 5, and the cross-sectional scanning electron microscope image shows that the precursor material has a radially-arranged internal structure. The TG weight versus DSC thermogram is shown in fig. 6, with the test conditions being air atmosphere, data collected at a scan rate of 10 ℃/min over the temperature range from room temperature to 700 ℃, analyzed according to the TG weight curve, a free water loss process before 270 ℃, a material decomposition to an oxide precursor starting at 270 ℃, analyzed according to the DSC thermogram, the thermal failure peak temperature of the precursor material is 292.87 ℃.

Comparative example 1:

the nickel-cobalt-manganese precursor with the core-shell structure comprises a core and a plurality of layers of aluminum-doped shells, wherein the chemical formula of the core is Ni_0.885Co_0.09Mn_0.025(OH)₂The chemical formula of the aluminum-doped shell layer is Ni_0.867Co_0.088Mn_0.025Al_0.002(OH)₂The secondary particle size D10 was 10.4 μm, the particle size D50 was 13.53 μm, the particle size D90 was 17.55 μm, and the particle size distribution (D90-D10)/D50 was 0.53. The tap density is 2.08g/cm³Specific surface area of 7.92m²And g, the Na content is 76ppm, and the S content is 1143 ppm.

The method of the nickel cobalt manganese precursor of the present comparative example comprises the steps of:

(1) preparing raw materials:

mixing nickel sulfate, cobalt sulfate and manganese sulfate, adding deionized water, and preparing into 1.8mol/L metal mixed salt solution, wherein the element molar ratio of nickel, cobalt and manganese is 88.5:9: 2.5;

adding aluminum sulfate octadecahydrate into a mixed solution of pure water and sodium hydroxide to prepare a 5mol/L sodium metaaluminate solution, wherein the excessive degree of the sodium hydroxide relative to the aluminum sulfate octadecahydrate is n (OH)^-1)：n(Al³⁺)＝25；

Adding ammonia water into deionized water to prepare an ammonia water solution with the concentration of 100 g/L;

sodium hydroxide was added to deionized water to prepare a 300g/L sodium hydroxide solution.

(2) Preparing a core-shell structure NCM ternary precursor material:

adding 80L of deionized water, 80mL of sodium hydroxide solution and 8L of ammonia water into a 100L reaction kettle, opening and stirring at the rotation speed of 450r/min and the constant temperature of 60 ℃ to obtain a base solution with the pH value of 11.55 +/-0.5, and continuously introducing nitrogen with the flow of 5L/min.

The first stage of growth: respectively introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle with prepared base solution at the speed of 30mL/min, 10mL/min and 5mL/min for reaction and precipitation for 3 hours, controlling the rotating speed of a stirrer to be 380r/min, controlling the pH value to be 11.5-11.6 and controlling the ammonia value to be 10-11 g/L; discharging the reaction mother liquor, carrying out solid-liquid separation by concentration equipment, and returning the solid to the reaction kettle to obtain the nickel-cobalt-manganese hydroxide core with the medium particle size D50 of 4.5 +/-0.5 mu m.

And a second growth stage: respectively introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle at 50mL/min, 18mL/min and 6mL/min for continuous reaction and precipitation, discharging a reaction mother solution when the reaction kettle is full of materials, performing solid-liquid separation by using concentration equipment, returning solids into the reaction kettle for continuous reaction, wherein the rotating speed of a stirrer in the reaction process is reduced along with the increase of the medium particle diameter D50, and when the medium particle diameter D50 is more than 4.5 +/-0.5 mu m and less than 6 +/-0.3 mu m, the rotating speed is 340 r/min; when the particle size is more than 6 +/-0.3 mu m and less than 8 +/-0.3 mu m, the rotating speed is 260 r/min; when the particle size is more than 8 +/-0.3 mu m and less than 10 +/-0.3 mu m, the rotating speed is 200 r/min.

And a third growth stage: introducing a metal salt solution, sodium metaaluminate, a sodium hydroxide solution and ammonia water into a reaction kettle at the speed of 50mL/min, 17mL/min, 16mL/min and 6mL/min respectively to continue reaction and precipitation, discharging a reaction mother solution, performing solid-liquid separation by a concentration device, returning solids into the reaction kettle to continue reaction, wherein the rotating speed of a stirrer is reduced along with the increase of D50 in the reaction process, and when the middle particle diameter D50 is more than 10 +/-0.3 mu m and less than 12 +/-0.3 mu m, the rotating speed is 160 r/min; when the grain diameter D50 is less than 13.5 +/-0.5 mu m and is more than 12 +/-0.3 mu m, the rotating speed is 120 r/min; stopping feeding when the particle size D50 reaches 13.5 +/-0.5 mu m, so that the solid content of the stopped kettle is lower than 400g/L, and obtaining the nickel-cobalt-manganese precursor slurry with the aluminum-doped shell.

Putting the nickel-cobalt-manganese precursor slurry with the aluminum-doped shell into a slurry washing kettle, draining supernatant, soaking for 3 hours by using 3mol/L alkali liquor, washing with alkali twice by using 1kg of solid product corresponding to 1.5L of 3mol/L alkali liquor, washing for many times until the washing conductivity is lower than 50us/cm, dishing filter cakes after filter pressing, drying in a vacuum oven at the drying temperature of 130 ℃ for 24 hours, and screening for deironing to obtain the multilayer aluminum-doped nickel-cobalt-manganese precursor, wherein the water content of the dried material is lower than 0.05%.

The scanning electron microscope image of the nickel-cobalt-manganese precursor of the comparative example is shown in fig. 7, the cross-sectional scanning electron microscope image is shown in fig. 8, and the cross-sectional scanning electron microscope image shows that the precursor material has a radially arranged internal structure. The TG weight versus DSC thermogram is shown in fig. 9, with the test conditions being air atmosphere, data collected at a scan rate of 10 ℃/min over the temperature range from room temperature to 700 ℃, analyzed according to the TG weight curve, a free water loss process before 270 ℃, a material decomposition to an oxide precursor starting at 270 ℃, analyzed according to the DSC thermogram, the thermal failure peak temperature of the precursor material is 290.98 ℃.

Comparative example 2:

the Ni-Co-Mn precursor of this comparative example has the chemical formula Ni_0.885Co_0.09Mn_0.025(OH)₂The secondary particle size D10 was 10.36 μm, the particle size D50 was 13.53 μm, the particle size D90 was 17.66 μm, the particle size distribution (D90-D10)/D50 was 0.54, and the tap density was 1.97g/cm³The specific surface area is 7.73m²And g, the Na content is 79ppm, and the S content is 1267 ppm.

The preparation method of the nickel-cobalt-manganese precursor comprises the following steps:

(1) preparing raw materials:

mixing nickel sulfate, cobalt sulfate and manganese sulfate, adding deionized water, and preparing into a 2mol/L metal mixed salt solution, wherein the element molar ratio of nickel, cobalt and manganese is 88.5:9: 2.5;

adding ammonia water into deionized water to prepare an ammonia water solution with the concentration of 100 g/L;

sodium hydroxide was added to deionized water to prepare a 300g/L sodium hydroxide solution.

(2) Nickel cobalt manganese precursor:

adding 80L of deionized water, 60mL of sodium hydroxide solution and 6L of ammonia water into a 100L reaction kettle, opening and stirring at the rotation speed of 450r/min and the constant temperature of 45 ℃ to obtain a base solution with the pH value of 11.15 +/-0.5, and continuously introducing nitrogen with the flow of 5L/min.

The first stage of growth: respectively introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle with prepared base solution at the speed of 30mL/min, 10mL/min and 5mL/min for reaction and precipitation for 3 hours, wherein the rotating speed is 450r/min, the rotating speed of a stirrer is controlled to be 450r/min, the pH value is 11.3-11.4, and the ammonia value is 7-8 g/L; discharging the reaction mother liquor, carrying out solid-liquid separation by concentration equipment, and returning the solid to the reaction kettle to obtain the nickel-cobalt-manganese hydroxide core with the medium particle size D50 of 4.5 +/-0.5 mu m.

And a second growth stage: introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle at a rate of 50mL/min, 18mL/min and 6mL/min respectively to continue reaction and precipitation, discharging a reaction mother liquor, performing solid-liquid separation by using concentration equipment, and returning solids to the reaction kettle; the rotating speed of the stirrer is reduced along with the increase of the medium particle size D50 in the reaction process, and when the particle size D50 is more than 4.5 +/-0.5 mu m and less than 6 +/-0.3 mu m; the rotating speed is 380 r/min; when the particle size is more than 6 +/-0.3 mu m and less than 8 +/-0.3 mu m, the rotating speed is 260 r/min; when the particle size is more than 8 +/-0.3 mu m and less than 10 +/-0.3 mu m, the rotating speed is 200 r/min.

And a third growth stage: introducing a metal salt solution, a sodium hydroxide solution and ammonia water into a reaction kettle at the speed of 100mL/min, 40mL/min and 15mL/min respectively to continue reaction and precipitation, discharging a reaction mother solution, performing solid-liquid separation by using concentration equipment, returning a solid into the reaction kettle, wherein the rotating speed of a stirrer is reduced along with the increase of D50 in the reaction process, and when the particle size is more than 10 +/-0.3 mu m and less than medium particle size D50 and less than 12 +/-0.3 mu m, the rotating speed is 160 r/min; when the grain diameter D50 is less than 13.5 +/-0.5 mu m and is more than 12 +/-0.3 mu m, the rotating speed is 120 r/min; and stopping feeding when the particle size D50 reaches 13.5 +/-0.5 mu m, so that the solid content of the stopped reactor is lower than 400g/L, and obtaining the nickel-cobalt-manganese precursor slurry without aluminum doping.

Putting the nickel-cobalt-manganese precursor slurry which is not doped with aluminum into a slurry washing kettle, draining supernatant, soaking for 3 hours by using 3mol/L alkali liquor, washing with alkali twice by using 1kg of solid product corresponding to 2.8L of 3mol/L alkali liquor, washing with water for many times until the washing conductivity is lower than 50us/cm, loading a filter cake into a tray after filter pressing, drying by using a vacuum oven at the drying temperature of 110 ℃ for 24 hours, and screening for removing iron after the moisture of the dried material is lower than 0.05%, thereby obtaining the nickel-cobalt-manganese precursor which is not doped with aluminum.

The scanning electron microscope image of the non-aluminum-doped nickel cobalt manganese precursor of the comparative example is shown in fig. 10, the cross-sectional scanning electron microscope image is shown in fig. 11, and the cross-sectional scanning electron microscope image shows that the precursor material has a radially-arranged internal structure. Fig. 12 shows a graph of TG weight versus DSC heat, with the test conditions being air atmosphere, data collected at a scan rate of 10 ℃/min over the temperature range from room temperature to 700 ℃, analyzed according to the TG weight curve, a free water loss process before 270 ℃, and decomposition of species to oxide precursors beginning at 270 ℃. The peak thermal failure temperature of the precursor material was 285.75 ℃ as analyzed by DSC thermogram.

According to the DSC thermogram analysis, the thermal failure peak temperature of the Al-Ni-Co-Mn-doped precursor in the stage of example 1 is 298.12 ℃, the thermal failure peak temperature of the Al-Ni-Co-Mn-doped precursor of the outer shell in comparative example 1 is 290.98 ℃ with a difference of about 7.14 ℃, and the thermal failure peak temperature of the non-Al-Ni-Co-Mn-doped precursor in comparative example 2 is 285.75 ℃ with a difference of about 12.37 ℃. This indicates that the multi-stage aluminum-doped multilayer structure can provide higher thermal stability for the high nickel-cobalt-manganese precursor than a core-shell structure in which only the shell is doped with aluminum. From electron microscope images of the nickel-cobalt-manganese precursors of the examples 1 and 2 and the comparative example 2, it can be seen that the nickel-cobalt-manganese precursor which is not doped with aluminum in the comparative example 2 has a plurality of cracking cracks, while the design of doping aluminum in the nuclear shell layer inhibits the cracking of the nickel-cobalt-manganese precursor in the growth process in the examples 1 and 2, which shows that the structural stability of the nickel-cobalt-manganese precursor is improved through the design of multi-layer doping of aluminum.