阅读说明：本技术 一种高放射状、高振实的镍钴铝酸锂前驱体及其制备方法 (High-radiation and high-tap-density nickel-cobalt lithium aluminate precursor and preparation method thereof ) 是由 张�诚 寇亮 牛瑶 孙静 张超 田占元 邵乐 于 2019-10-23 设计创作，主要内容包括：本发明公开了一种高放射状、高振实的镍钴铝酸锂前驱体及其制备方法,所述的镍钴铝酸锂前驱体为氢氧化镍钴铝,其刨面形貌内到外呈放射状,材料中铝元素由内到外均匀分布,其一次颗粒呈薄片状,具备高振实、高球形度的特点。本发明的制备包括晶种制备、晶体生长的过程,通过严格控制成核、生长的反应条件,实现前驱体均匀定向生长。本发明工艺简单,过程容易稳定控制,产品性能优异,适于大规模工业化生产。(The invention discloses a high-radiation and high-tap density nickel cobalt lithium aluminate precursor and a preparation method thereof. The preparation method comprises the processes of seed crystal preparation and crystal growth, and realizes uniform and directional growth of the precursor by strictly controlling the reaction conditions of nucleation and growth. The invention has simple process, easy and stable control of the process and excellent product performance, and is suitable for large-scale industrial production.)

1. The high-radiation and high-tap-density nickel cobalt lithium aluminate precursor is characterized in that the molecular formula of the nickel cobalt lithium aluminate precursor is Ni_xCo_yAl_z(OH)₂Wherein x + y + z is 1, and x is more than or equal to 0.8 and less than 1.0; the cross section of the nickel-cobalt lithium aluminate precursor is in a radial shape from inside to outside.

2. The lithium nickel cobalt aluminate precursor with high radial performance and high tap density as claimed in claim 1, wherein the aluminum element in the lithium nickel cobalt aluminate precursor is uniformly distributed from inside to outside.

3. The lithium nickel cobalt aluminate precursor with high radial performance and high tap density as claimed in claim 1, wherein the tap density of the lithium nickel cobalt aluminate precursor is not less than 1.9g/cm³A specific surface area of 5 to 35m²/g。

4. The lithium nickel cobalt aluminate precursor of claim 1, wherein the lithium nickel cobalt aluminate precursor has a shape of primary particles in a flake form and a shape of secondary particles in a highly spherical form.

5. A method for preparing a highly radial, high tap lithium nickel cobalt aluminate precursor according to any of claims 1 to 4, comprising the steps of:

(1) preparation of reaction solution: dissolving nickel salt and cobalt salt into a mixed salt solution with the concentration of 1-3 mol/L; preparing aluminum salt into an aluminum salt solution with the concentration of 0.05-0.5 mol/L; dissolving alkali into an alkali solution with the concentration of 4-10 mol/L; preparing an ammonia water solution with the concentration of 5-13 mol/L as a complexing agent;

(2) preparing seed crystals: sequentially adding an ammonia water solution and an alkali solution into a reaction kettle filled with semi-kettle water or full kettle water, adjusting the ammonia concentration in the kettle to be 0.25-0.40M, the pH value to be 11.5-12.5, controlling the temperature in the kettle to be 40-70 ℃, the stirring speed to be 500-800 rpm, achieving a crystal nucleus forming condition, nucleating for 0.5-2h, and controlling the grain size of the nucleated particles to be 1.0-2.0 mu M; maintaining the reaction temperature and the stirring speed in the kettle constant, adding the aqueous alkali and the aqueous ammonia solution into the kettle again, and adjusting the ammonia concentration and the pH value in the kettle to reach the crystal nucleus growth condition; finally, the mixed salt solution and the aluminum salt solution are added into the kettle in parallel according to the designed element proportion of the precursor, meanwhile, the alkali solution and the ammonia water solution are added to maintain the ammonia concentration and the pH value in the kettle to be constant, then the seed crystal preparation time is controlled to reach the set grain size of the seed crystal, and the preparation of the seed crystal solution is completed;

(3) crystal growth: taking out part of the seed crystal solution, adding the seed crystal solution into another reaction kettle added with half kettle water, adjusting the solid content of the solution in the kettle to a certain value, adjusting the reaction temperature and the stirring speed in the kettle to a certain value, adjusting the ammonia concentration and the pH value in the kettle to the crystal growth condition, adding the mixed salt solution and the aluminum salt solution into the kettle in parallel according to the designed element proportion of the precursor, and simultaneously adding the alkali solution and the ammonia water solution to maintain the ammonia concentration and the pH value in the kettle constant, so that the crystal grows directionally and uniformly;

(4) aging of the crystals: when the granularity of the crystals in the step (3) reaches a preset size, overflowing the crystals to an aging kettle for aging;

(5) and (3) washing and drying the crystals: discharging the material aged in the step (4) into a centrifuge, and washing the material with hot water and 1-4 mol/L hot alkali for multiple times until the pH value of washing water is less than 10.0; and drying the washed materials to obtain the high-radiation and high-tap-density nickel cobalt lithium aluminate precursor.

6. The method of claim 5, wherein the nickel salt is one of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the cobalt salt is one of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate; the aluminum salt is sodium metaaluminate; the alkali is sodium hydroxide.

7. The method of claim 5, wherein the crystal nucleus growth in step (2) has a pH of 11.0-12.0, an ammonia concentration of 0.35-0.55M, the seed crystal preparation time is 5-40 h, and the seed crystal has a particle size D50-3.0-4.5 μ M.

8. The method for preparing high-radiation and high-tap nickel cobalt lithium aluminate precursor according to claim 5, wherein in the step (3), the solid content of the solution in the kettle is adjusted to be 3-10%, the reaction temperature in the kettle is adjusted to be 40-70 ℃, the stirring speed in the kettle is adjusted to be 300-600 rpm, the pH value in the kettle is adjusted to be 10.5-12.0, the ammonia concentration in the kettle is adjusted to be 0.35-0.70M, and the crystal directional growth rate is 0.05-0.25 μ M/h.

9. The method for preparing a lithium nickel cobalt aluminate precursor with high radiation performance and high tap density as claimed in claim 5, wherein when the grain size of the crystal in step (3) reaches 6-15 μm, the crystal is overflowed to an aging kettle and aged at a rotation speed of 50-150rpm, wherein the aging temperature is 40-70 ℃ and the aging time is 2-30 hours.

10. The method for preparing the lithium nickel cobalt aluminate precursor with high radiation performance and high tap density according to claim 5, wherein the volume ratio of the hot alkali to the hot water in the step (5) is 1:1, the mass ratio of the aged material to the hot water is 1: 5-1: 10, and the temperatures of the hot water and the hot alkali are 40-70 ℃.

Technical Field

The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a high-radiation and high-tap density nickel cobalt lithium aluminate precursor and a preparation method thereof.

Background

The layered nickel-cobalt-aluminum ternary material (NCA) has the advantages of excellent electrochemical performance, higher specific capacity, lower production cost and the like, and becomes one of the most promising lithium ion battery materials. The most key technology of the nickel-cobalt-aluminum ternary material is in the precursor process, and the physicochemical indexes of the final sintered product are directly determined by the quality (morphology, particle size distribution, specific surface area, impurity content, tap density and the like) of the precursor.

At present, the main preparation process of the nickel-cobalt-aluminum ternary precursor is a cocrystallization method, while the reaction process of the precursor is a very complex process, and parameters to be controlled are many, including the concentrations of salt and alkali, the concentration of ammonia water, the feeding speed, the reaction temperature, the stirring speed, the solid content and the like. The shape, the specific surface, the particle size distribution, the tap density and the electrochemical performance after sintering of the precursor prepared under different process conditions are obviously different. At present, the technology of the lithium nickel cobalt aluminate in China is not mature enough, and NCA products in the industry mainly come from Japanese and Korean. The main reasons are that the NCA precursor is difficult to prepare, the process route is immature, the product consistency is poor, and particularly, the difference between the precipitation coefficient of aluminum and nickel and cobalt is large, so that the tap density of the precursor is low, and the aluminum is unevenly distributed. In addition, most of the existing NCA precursors are in internal disordered distribution, so that sintered finished products are easy to pulverize in the circulating process and poor in electrochemical performance.

Disclosure of Invention

Aiming at the problems of low tap density, uneven distribution of aluminum elements, poorer electrochemical performance of sintered finished products and the like of the nickel-cobalt lithium aluminate precursor, the invention provides the nickel-cobalt lithium aluminate precursor with high radiation and high tap density and the preparation method thereof, aiming at overcoming the defects in the prior art, and the invention provides the nickel-cobalt lithium aluminate precursor with excellent physical and chemical properties, good stability and simple process.

In order to achieve the purpose, the invention adopts the following technical scheme:

high-radiation and high-tap-density nickel-cobalt lithium aluminate precursorThe molecular formula of the nickel cobalt lithium aluminate precursor is Ni_xCo_yAl_z(OH)₂Wherein x + y + z is 1, and x is more than or equal to 0.8 and less than 1.0; the cross section of the nickel-cobalt lithium aluminate precursor is in a radial shape from inside to outside.

Further, the aluminum element in the nickel cobalt lithium aluminate precursor is uniformly distributed from inside to outside.

Further, the tap density of the nickel cobalt lithium aluminate precursor is more than or equal to 1.9g/cm³A specific surface area of 5 to 35m²/g。

Furthermore, the nickel cobalt lithium aluminate precursor primary particles are in a flake shape, and the secondary particles are in a highly spherical shape.

A preparation method of a high-radial and high-tap nickel cobalt lithium aluminate precursor comprises the following steps:

(1) preparation of reaction solution: dissolving nickel salt and cobalt salt into a mixed salt solution with the concentration of 1-3 mol/L; preparing aluminum salt into an aluminum salt solution with the concentration of 0.05-0.5 mol/L; dissolving alkali into an alkali solution with the concentration of 4-10 mol/L; preparing an ammonia water solution with the concentration of 5-13 mol/L as a complexing agent;

(2) preparing seed crystals: sequentially adding an ammonia water solution and an alkali solution into a reaction kettle filled with semi-kettle water or full kettle water, adjusting the ammonia concentration in the kettle to be 0.25-0.40M, the pH value to be 11.5-12.5, controlling the temperature in the kettle to be 40-70 ℃, the stirring speed to be 500-800 rpm, achieving a crystal nucleus forming condition, nucleating for 0.5-2h, and controlling the grain size of the nucleated particles to be 1.0-2.0 mu M; maintaining the reaction temperature and the stirring speed in the kettle constant, adding the aqueous alkali and the aqueous ammonia solution into the kettle again, and adjusting the ammonia concentration and the pH value in the kettle to reach the crystal nucleus growth condition; finally, the mixed salt solution and the aluminum salt solution are added into the kettle in parallel according to the designed element proportion of the precursor, meanwhile, the alkali solution and the ammonia water solution are added to maintain the ammonia concentration and the pH value in the kettle to be constant, then the seed crystal preparation time is controlled to reach the set grain size of the seed crystal, and the preparation of the seed crystal solution is completed;

(3) crystal growth: taking out part of the seed crystal solution, adding the seed crystal solution into another reaction kettle added with half kettle water, adjusting the solid content of the solution in the kettle to a certain value, adjusting the reaction temperature and the stirring speed in the kettle to a certain value, adjusting the ammonia concentration and the pH value in the kettle to the crystal growth condition, adding the mixed salt solution and the aluminum salt solution into the kettle in parallel according to the designed element proportion of the precursor, and simultaneously adding the alkali solution and the ammonia water solution to maintain the ammonia concentration and the pH value in the kettle constant, so that the crystal grows directionally and uniformly;

(4) aging of the crystals: when the granularity of the crystals in the step (3) reaches a preset size, overflowing the crystals to an aging kettle for aging;

(5) and (3) washing and drying the crystals: discharging the material aged in the step (4) into a centrifuge, and washing the material with hot water and 1-4 mol/L hot alkali for multiple times until the pH value of washing water is less than 10.0; and drying the washed materials to obtain the high-radiation and high-tap-density nickel cobalt lithium aluminate precursor.

Further, the nickel salt is one of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the cobalt salt is one of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate; the aluminum salt is sodium metaaluminate; the alkali is sodium hydroxide.

Further, the pH value of the crystal nucleus growth in the step (2) is 11.0-12.0, the ammonia concentration is 0.35-0.55M, the seed crystal preparation time is 5-40 h, and the particle size of the seed crystal is set to be D50-3.0-4.5 mu M.

Further, in the step (3), the solid content of the solution in the kettle is adjusted to be 3-10%, the reaction temperature in the kettle is adjusted to be 40-70 ℃, the stirring speed in the kettle is adjusted to be 300-600 rpm, the pH value in the kettle is adjusted to be 10.5-12.0, the ammonia concentration in the kettle is adjusted to be 0.35-0.70M, and the oriented growth rate of the crystal is 0.05-0.25 mu M/h.

Further, when the grain size of the crystal in the step (3) reaches 6-15 μm, overflowing the crystal to an aging kettle to age at the rotating speed of 50-150rpm, wherein the aging temperature is 40-70 ℃, and the time is 2-30 h.

Further, in the step (5), the volume ratio of hot alkali to hot water is 1:1, the mass ratio of the aged material to the hot water is 1: 5-1: 10, and the temperatures of the hot water and the hot alkali are 40-70 ℃.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention increases the seed crystal preparation, strictly controls the nucleation particle size, the seed crystal preparation and the crystal growth conditions, ensures the stability of the process on one hand, and ensures the high radial arrangement of the precursor from inside to outside on the other hand. The sintered finished product inherits the high radial arrangement of the precursor, is beneficial to the rapid migration of lithium ions into the material in the circulation process, and reduces the pulverization caused by the volume change in the charge and discharge process.

In addition, sodium metaaluminate is adopted as aluminum salt, and the ammonia concentration and pH condition are optimized, so that the uniform distribution of aluminum element in the precursor from inside to outside is ensured; and by controlling the growth speed of the precursor, the compact internal structure, high sphericity and tap density of the precursor are ensured.

Drawings

FIG. 1 shows Ni obtained in example 1 of the present invention_0.82Co_0.15Al_0.03(OH)₂Schematic representation of samples under 5000 x electron microscope.

FIG. 2 shows Ni obtained in example 1 of the present invention_0.82Co_0.15Al_0.03(OH)₂Schematic representation of the sample under a 50000 fold electron microscope.

FIG. 3 shows Ni obtained in example 1 of the present invention_0.82Co_0.15Al_0.03(OH)₂Schematic of sample planing surface.

FIG. 4 shows Ni obtained in example 1 of the present invention_0.82Co_0.15Al_0.03(OH)₂The scanning electron microscope energy spectrogram of the sample section, wherein (A) is the scanning electron microscope image of the prepared sample, and (B), (C) and (D) are distribution diagrams of three elements of nickel, cobalt and aluminum respectively.

Detailed Description

Embodiments of the invention are described in further detail below:

the high-radiation and high-tap-density nickel cobalt lithium aluminate precursor has a molecular formula of Ni_xCo_yAl_z(OH)₂Wherein x + y + z is 1, and x is more than or equal to 0.8 and less than 1.0; the cross section of the nickel-cobalt lithium aluminate precursor is in a radial shape from inside to outside; the aluminum element in the nickel-cobalt lithium aluminate precursor is uniformly distributed from inside to outside; the tap density of the nickel cobalt lithium aluminate precursor≥1.9g/cm³A specific surface area of 5 to 35m²(ii)/g; the nickel cobalt lithium aluminate precursor is in a flake shape, and the secondary particles are in a highly spherical shape.

A preparation method of a high-radial and high-tap nickel cobalt lithium aluminate precursor comprises the following steps:

(1) preparation of reaction solution: dissolving nickel salt and cobalt salt into a mixed salt solution with the concentration of 1-3 mol/L, and preparing aluminum salt into an aluminum salt solution with the concentration of 0.05-0.5 mol/L (a proper amount of sodium hydroxide can be selectively added as a cosolvent when preparing the aluminum salt solution); dissolving alkali into an alkali solution with the concentration of 4-10 mol/L; 5-13 mol/L ammonia water solution is used as a complexing agent.

Wherein the nickel salt is one of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the cobalt salt is one of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate; the aluminum salt is sodium metaaluminate; the alkali is sodium hydroxide.

(2) Preparing seed crystals: sequentially adding an ammonia water solution and an alkali solution into a reaction kettle filled with semi-kettle water or full kettle water, adjusting the ammonia concentration in the kettle to be 0.25-0.40M, the pH value to be 11.5-12.5, controlling the temperature in the kettle to be 40-70 ℃, and the stirring speed to be 500-800 rpm, so as to achieve the condition of crystal nucleus formation, nucleating for 0.5-2h, and controlling the grain size of the nucleated particles to be 1.0-2.0 mu M. And (3) maintaining the reaction temperature and the stirring speed in the kettle constant, adding an alkali solution and an ammonia water solution into the kettle, and adjusting the ammonia concentration and the pH value in the kettle to reach the crystal nucleus growth condition. And (3) adding the mixed salt solution and the aluminum salt solution into the kettle in parallel according to the designed element proportion of the precursor, simultaneously adding the alkali solution and the ammonia water solution to maintain the ammonia concentration and the pH value in the kettle to be constant, and then controlling the seed crystal preparation time to reach the set particle size of the seed crystal to finish the preparation of the seed crystal solution.

Wherein the crystal nucleus growth pH value is 11.0-12.0, the ammonia concentration is 0.25-0.55M, the seed crystal preparation time is 5-40 h, and the particle size of the seed crystal is D50-3.0-4.5 mu M.

(3) Crystal growth: taking out part of the crystal seed solution, adding the crystal seed solution into another reaction kettle added with half kettle water, adjusting the solid content of the solution in the kettle to a certain value, adjusting the reaction temperature and the stirring speed in the kettle to a certain value, adjusting the ammonia concentration and the pH value in the kettle to the crystal growth condition, adding the mixed salt solution and the aluminum salt solution into the kettle in parallel according to the designed element proportion of the precursor, and simultaneously adding the alkali solution and the ammonia water solution to maintain the ammonia concentration and the pH value in the kettle constant so as to ensure that the mixed salt solution and the aluminum salt solution grow directionally and uniformly.

The solid content in the kettle after part of the seed crystals are taken out is 3-10%, the reaction temperature of crystal growth is 40-70 ℃, the stirring speed of the crystal growth is 300-600 rpm, the pH value is 10.5-12.0, the concentration of ammonia water is 0.35-0.70M, and the oriented uniform growth rate of the crystals is 0.05-0.25 mu M/h.

(4) Aging of the crystals: and (4) overflowing the crystal of the step (3) to an aging kettle when the grain size of the crystal reaches a preset size, and aging for 2-30 h.

Wherein the predetermined size of the precursor crystal is 6-15 μm. The aging process is low-speed stirring, and the aging temperature is 40-70 ℃.

(5) And (3) washing and drying the crystals: discharging the material aged in the step (4) into a centrifuge, and washing the material with 1-4 mol/L hot alkali and hot water for multiple times until the pH value of the washing water is less than 10.0; and drying the washed materials to obtain the high-radiation and high-tap-density nickel cobalt lithium aluminate precursor.

Wherein the volume ratio of the thermokalite to the hot water is 1:1, the mass ratio of the aged material to the hot water is 1: 5-1: 10, and the temperature of the hot water and the thermokalite is 40-70 ℃.

The present invention is described in further detail below with reference to examples: