CN113373500B

CN113373500B - High-nickel single crystal ternary precursor and preparation method thereof

Info

Publication number: CN113373500B
Application number: CN202110596993.3A
Authority: CN
Inventors: 李加闯; 禇凤辉; 朱用; 孟一鸣; 成鑫丽; 王梁梁; 贺建军
Original assignee: Nantong Kington Energy Storage Power New Material Co ltd
Current assignee: Nantong Kington Energy Storage Power New Material Co ltd
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2022-07-05
Anticipated expiration: 2041-05-31
Also published as: CN113373500A

Abstract

High-nickel single crystal ternary precursor andthe preparation method comprises the following steps: mixing Ni²⁺、Co²⁺、Mn²⁺And potassium manganese (III) oxalate³⁺With Mn²⁺The molar ratio of (a) to (b) is 2-4, so that primary particles of the secondary particles are refined, and the specific surface area is increased. And adding the mixed salt solution, the precipitator solution and the complexing agent solution into a reaction kettle, and reacting to generate the high-nickel single crystal ternary precursor slurry. Then carrying out filter pressing, washing and drying to obtain the high-nickel single crystal ternary precursor. The primary particles are flaky and have a thickness of 50 to 110 nm. The method solves the technical problems of material capacity attenuation and improper primary particle thickness caused by mixed discharge of nickel and lithium cations in the subsequent mixed calcination process of the high-nickel single crystal ternary precursor and a lithium source.

Description

High-nickel single crystal ternary precursor and preparation method thereof

Technical Field

The invention relates to the technical field of lithium ion battery anode materials, in particular to a high-nickel single crystal ternary precursor and a preparation method thereof.

Background

The high-nickel single crystal ternary positive electrode material has the advantages of high specific capacity, small pollution, moderate price, good matching with electrolyte and the like, becomes the focus of attention of the positive electrode material, is considered to be a lithium ion battery positive electrode material with great development prospect, and has a very wide market in the field of power batteries. Compared with the high-nickel polycrystalline ternary cathode material, the high-nickel monocrystalline ternary cathode material has the advantages of few crystal boundaries, low internal resistance and better cycle performance. In addition, the high-nickel single crystal ternary cathode material has higher mechanical strength and higher compaction density than the high-nickel polycrystalline ternary cathode material.

The high-nickel single-crystal ternary cathode material is mainly obtained by mixing and calcining a high-nickel single-crystal ternary precursor and a lithium source (lithium carbonate for NCM333, NCM523 and NCM622, lithium hydroxide for NCM811 and NCA). In the calcining process, oxygen is required to be continuously introduced to oxidize nickel, cobalt and manganese respectively, the contact area of the oxygen and the high-nickel monocrystal ternary precursor is limited, and part of Ni exists²⁺Is not oxidized due to Ni²⁺(0.069nm) and Li⁺(0.076nm) Ni of very close radius, not oxidized²⁺Easily enter Li⁺Position, easily cause Li⁺/Ni²⁺Mixed discharging, and the nickel content in the high nickel precursor is increased, which can cause the increase of mixed discharging of nickel and lithium cations in the sintering stage. Due to Ni²⁺Will be oxidized into Ni during delithiation³⁺Smaller radius (0.056nm) and thus leads to a collapse of the interlayer spacing local structure, partly Li⁺The material is difficult to embed into the original position, and finally, the material capacity is reduced, and the cycle performance is deteriorated. Therefore, some improvement is needed in the precursor stage or the calcination stage, so as to reduce the degree of nickel-lithium cation shuffling and improve the reversible capacity and cycle performance of the material. In order to solve the problem, chinese patent CN108511746A adopts a method of pre-sintering a ternary precursor to achieve the purpose of pre-oxidation modification, but this method needs to add one calcination process, which results in an increase in cost.

The existing method for preparing the high-nickel single crystal ternary precursor has another problem that: the thickness of the primary particles is not suitable, and the prior art ternary precursor primary particles are generally too thick to facilitate the diffusion of lithium ions during sintering, resulting in a decrease in battery capacity.

In view of the above, the present invention provides a method for designing a high nickel single crystal ternary precursor with an appropriate primary particle thickness, which is beneficial to reducing the nickel-lithium cation mixed-out.

Disclosure of Invention

The invention aims to provide a high-nickel single crystal ternary precursor and a preparation method thereof, and aims to solve the technical problems of material capacity attenuation and improper primary particle thickness caused by mixed discharge of nickel and lithium cations in the subsequent mixed calcination process of the high-nickel single crystal ternary precursor and a lithium source.

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

a preparation method of a high-nickel single crystal ternary precursor comprises the following steps:

step one, a pretreatment stage: mixing Ni²⁺、Co²⁺、Mn²⁺And potassium mangano-manganic (III) oxalate with the general formula Ni_xCo_yMn_z(OH)₂Preparing soluble mixed salt solution with the molar ratio of the corresponding elements in the solution, wherein x + y + z is 1, x is more than or equal to 0.85 and less than 1.0, y is more than 0 and less than 0.15, z is more than 0.01 and less than 0.15, and Mn of potassium manganous (III) oxalate is³⁺With Mn²⁺The molar ratio of (2) to (4) is 2-4, so that primary particles of the secondary particles are refined, and the specific surface area is increased; the pH value of the mixed salt solution is 4.5-5.5.

Preparing sodium hydroxide or potassium hydroxide solution as precipitant solution and ammonia water solution as complexing agent solution.

Step two, reaction stage: and (2) adding the mixed salt solution, the precipitant solution and the complexing agent solution prepared in the step (I) into a reaction kettle under the condition of stirring, controlling the reaction temperature to be 50-70 ℃, the pH value to be 11.50-12.50 and the rotating speed of the reaction kettle to be 350-600 r/min, and reacting to generate the high-nickel single crystal ternary precursor slurry.

Step three, post-treatment stage: and (4) carrying out filter pressing, washing and drying on the high-nickel single crystal ternary precursor slurry prepared in the step two to prepare the high-nickel single crystal ternary precursor.

The high-nickel single crystal ternary precursor is secondary particles formed by gathering primary particles, and the primary particles are flaky and have the thickness of 50-110 nm; d50 of the high-nickel single crystal ternary precursor is 3.2-3.8 um, and the tap density is 1.65-1.90 g/cm³The specific surface area is 8 to 18 m²/g。

The high-nickel single crystal ternary precursor prepared by the preparation method is adopted.

The relevant content in the above technical solution is explained as follows:

1. in the above scheme, Ni²⁺、Co²⁺、Mn²⁺And potassium manganese (III) oxalate according to the formula Ni_xCo_yMn_z(OH)₂Preparing soluble mixed salt solution according to the molar ratio of the corresponding elements. Introduction of Mn by addition of Potassium manganese (III) Trioxalate³⁺The potassium manganese (III) oxalate can be directly mixed with a nickel-cobalt-manganese metal salt solution, manganese in the mixed salt solution contains +2 and +3 valence states at the same time, a finished high-nickel monocrystal ternary precursor contains +2 and +3 valence states at the same time, and Mn³⁺With Mn²⁺The molar ratio of (a) to (b) is 2 to 4.

In the reaction stage, Mn³⁺Specific Mn²⁺The ternary precursor is easier to react with sodium hydroxide to generate precipitates, the formation of crystal nuclei is facilitated, primary particles of secondary particles can be refined to a certain degree, and the specific surface area of the finished ternary precursor can be increased by small primary particles. In the subsequent process of preparing the ternary cathode material, the large specific surface area of the ternary precursor is beneficial to increasing the contact area of the ternary precursor and oxygen, so that Ni is promoted²⁺Is fully oxidized into Ni³⁺Improving the oxidation efficiency and reducing Li⁺/Ni²⁺Degree of mixing. In addition, the refinement of the primary particles of the secondary particles is also beneficial to lithium ion diffusion in the sintering process, improves the crystallinity of the cathode material, and improves the cycle performance and the rate capability of the cathode material.

2. In the above scheme, Mn of potassium manganese (III) oxalate³⁺With Mn²⁺The molar ratio of (a) to (b) is 2 to 4, so as to realize the refinement of primary particles of secondary particles. More potassium manganese (III) oxalate than this range leads to Mn³⁺The content is too high, so that primary particles of the product are too fine, and the phenomenon of overburning is easy to occur in the sintering of the anode material, so that the performance is poor; less than this range of potassium manganese (III) oxalate results in Mn³⁺The content is too low, so that primary particles of the product are too coarse, and sintering of the positive electrode material is not facilitated.

3. In the scheme, the reaction temperature is controlled to be 50-70 ℃, the pH value is controlled to be 11.50-12.50, and the rotating speed of the reaction kettle is controlled to be 350-600 r/min in the reaction stage. In the whole reaction process, the pH value range, a certain rotating speed and temperature are kept, so that a stable dynamic balance can be provided, the uniform growth of primary particles is facilitated, and the nickel-cobalt-manganese hydroxide sediment containing trivalent manganese ions is generated by adding the potassium manganeisoxalato (III), so that the primary particles of secondary particles are refined.

4. In the scheme, the high-nickel single crystal ternary precursor is secondary particles formed by aggregation of primary particles, the thickness of the primary particles is 50-110 nm, the D50 of the high-nickel single crystal ternary precursor is 3.2-3.8 um, and the tap density is 1.65-1.90 g/cm³The specific surface area is 8 to 18 m²(iv) g. The thickness of the ternary precursor primary particle prepared by the technical scheme is 50-110 nm, the thickness is proper, and if the thickness of the primary particle is higher than the thickness range, the diffusion of lithium ions in the subsequent sintering process is not facilitated, so that the capacity of the battery is reduced; if the thickness of the primary particles is less than the thickness range, overburning is likely to occur, which affects the safety performance of the battery. The inventor finds that the thickness of the primary particles is limited to 50-110 nm, so that the lithium ion diffusion in the subsequent sintering process can be met, and the safety performance of the battery can be guaranteed. The amount of potassium manganeisoxalato (III) directly influences the amount of trivalent manganese ions, and further influences the primary particle size of secondary particles when Mn is added³⁺The content is too low, so that the thickness of primary particles of the product is too large, the tap density is improved, and the specific surface area is reduced; when Mn is present³⁺The content is too high, the thickness of primary particles of the prepared product is too small, the tap density is low, and the specific surface area is too large.

5. In the above scheme, in the reaction stage, Ni²⁺、Co²⁺、Mn²⁺Mn in potassium manganous (III) oxalate³⁺Reacting with hydroxyl to produce Ni_xCo_yMn_z(OH)₂。

6. In the above scheme, Ni in the mixed salt solution of the first step²⁺The concentration is 100-113 g/L, Co²⁺The concentration is 1-18 g/L, Mn²⁺Ni in a concentration of 1 to 16 g/L²⁺、Co²⁺And Mn²⁺The total concentration of the three metal ions is 117-120 g/L.

7. In the scheme, a sodium hydroxide or potassium hydroxide solution with the mass fraction of 20-40% is prepared to be used as a precipitator solution.

8. In the scheme, an ammonia water solution with the mass fraction of 3% -6% is prepared to serve as a complexing agent.

9. In the scheme, the mixed salt solution, the precipitator solution and the complexing agent solution in the step two are added into the reaction kettle at the flow rate of 80-150 mL/min.

10. In the scheme, nickel sulfate, cobalt sulfate and manganese sulfate are selected to prepare a soluble mixed salt solution in the step one.

The working principle of the invention is as follows: in order to solve the technical problem of mixed discharge of nickel and lithium cations in the subsequent mixed calcination process of the high-nickel single crystal ternary precursor and a lithium source, the invention adds potassium manganous oxalate (III) to introduce Mn in the pretreatment stage³⁺And controlling Mn³⁺With Mn²⁺Has a molar ratio of 2-4, Mn³⁺Specific Mn to Mn²⁺The sodium hydroxide is easier to react to generate precipitate, which is beneficial to the formation of crystal nucleus and can refine the primary particles of the secondary particles to a certain extent. In order to solve the technical problem that the thickness of primary particles of the high-nickel single crystal ternary precursor is not proper, the addition amount of potassium manganeisoxalate (III) and Mn are controlled³⁺With Mn²⁺The molar ratio of (a) is 2-4, and the process conditions in the reaction stage are controlled to control the thickness of the primary particles to be 50-110 nm.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages and effects:

1. the invention introduces Mn by adding potassium manganous (III) oxalate³⁺The primary particles of the secondary particles are refined, and in the subsequent preparation process of the ternary cathode material, the large specific surface area of the ternary precursor is beneficial to increasing the contact area of the ternary precursor and oxygen, so that Ni is promoted²⁺Is fully oxidized into Ni³⁺Improving the oxidation efficiency and reducing Li⁺/Ni²⁺Degree of mixing. The refinement of the primary particles of the secondary particles is also beneficial to lithium ion diffusion in the sintering process, improves the crystallinity of the anode material, and improves the cycle performance and the rate capability of the anode material.

2. According to the invention, the thickness of the primary particles of the high-nickel single crystal ternary precursor is controlled to be 50-110 nm by controlling the addition amount of potassium manganese (III) oxalate and reaction process conditions, so that the ternary precursor has a proper tap density and a proper specific surface area, lithium ion diffusion in the subsequent sintering process for preparing the ternary cathode material can be met, and the safety performance of the battery can be ensured.

In a word, the high-nickel single crystal ternary precursor prepared by the method has the advantages of low nickel-lithium cation mixing and discharging degree in the subsequent mixing and calcining process with a lithium source, full lithium ion diffusion, high crystallinity of a positive electrode material, and good cycle performance and rate capability. The thickness of the primary particles of the high-nickel single crystal ternary precursor is appropriate, so that the lithium ion diffusion in the sintering process of the subsequent preparation of the ternary cathode material can be met, and the safety performance of the battery can be ensured. The whole preparation method is simple and accurate, and large-scale industrial mass production is realized.

Drawings

FIG. 1 is an SEM image of a ternary precursor of a high-nickel single crystal obtained in example 1 of the present invention;

FIG. 2 is a first charge-discharge curve diagram of a ternary cathode material prepared from the high-nickel single crystal ternary precursor in example 1 of the present invention;

FIG. 3 is an SEM photograph of the ternary precursor prepared in comparative example 1;

FIG. 4 is an SEM photograph of the ternary precursor prepared in comparative example 2;

FIG. 5 is an SEM image of a high-nickel single crystal ternary precursor obtained in example 2 of the present invention;

FIG. 6 is a first charge-discharge curve diagram of a ternary cathode material prepared from the high-nickel single crystal ternary precursor in example 2 of the present invention;

FIG. 7 is an SEM photograph of the ternary precursor prepared in comparative example 3;

FIG. 8 is an SEM photograph of the ternary precursor prepared in comparative example 4.

Detailed Description

The invention is further described below with reference to the following figures and examples:

example 1:

step one, a pretreatment stage: mixing Ni²⁺、Co²⁺、Mn²⁺And potassium mangano-manganic (III) oxalate with the general formula Ni_0.85Co_0.09Mn_0.06(OH)₂Preparing soluble mixed salt solution with the molar ratio of the corresponding elements, wherein Mn of potassium manganese (III) oxalate³⁺With Mn²⁺The molar ratio of (a) to (b) is 3, so as to realize the refinement of primary particles of secondary particles and improve the specific surface area; the pH value of the mixed salt solution is 4.5-5.5.

Step one Ni in the mixed salt solution²⁺The concentration is 100g/L, Co²⁺The concentration is 10.5 g/L, Mn²⁺Concentration of 6.5 g/L, Ni²⁺、Co²⁺And Mn²⁺The total concentration of the three metal ions is 117 g/L.

Preparing a sodium hydroxide solution with the mass fraction of 32% as a precipitator solution, and an ammonia water solution with the mass fraction of 4.8% as a complexing agent solution.

Step two, reaction stage: and (2) adding the mixed salt solution, the precipitator solution and the complexing agent solution prepared in the step one into a reaction kettle at the flow rate of 100mL/min under the stirring condition, controlling the reaction temperature to be 55 ℃, the pH value to be 11.50-12.50 and the rotation speed of the reaction kettle to be 550r/min, and reacting to generate the high-nickel single crystal ternary precursor slurry.

The high-nickel single crystal ternary precursor is a secondary particle formed by aggregation of primary particles, and the primary particles are flaky and have the thickness of 98.7 nm; the D50 of the high-nickel single crystal ternary precursor is 3.718um, and the tap density is 1.69 g/cm³A specific surface area of 14.572 m²/g。

Comparative example 1:

a method for preparing a ternary precursor, which is different from that of example 1 in that no potassium manganese (iii) oxalate is added in the step one, and the rest of the reaction conditions and parameters are the same as those of example 1.

Comparative example 2:

a method for preparing a ternary precursor, which is different from that of example 1 in the proportion of potassium manganese (III) oxalate added in the step one, wherein Mn of the potassium manganese (III) oxalate is different³⁺With Mn²⁺The molar ratio of (a) to (b) was 5, and the remaining reaction conditions and parameters were the same as in example 1.

Example 2:

step one, a pretreatment stage: mixing Ni²⁺、Co²⁺、Mn²⁺And potassium manganese (III) oxalate according to the formula Ni_0.92Co_0.05Mn_0.03(OH)₂Preparing soluble mixed salt solution with the molar ratio of the corresponding elements, wherein Mn of potassium manganese (III) oxalate³⁺With Mn²⁺The molar ratio of (2) to refine the primary particles of the secondary particles and improve the specific surface area; the pH value of the mixed salt solution is 4.5-5.5.

Step one Ni in the mixed salt solution²⁺The concentration is 108 g/L, Co²⁺The concentration is 6 g/L, Mn²⁺Concentration of 3 g/L, Ni²⁺、Co²⁺And Mn²⁺The total concentration of the three metal ions is 117 g/L.

Step two, reaction stage: and (2) under the condition of stirring, adding the mixed salt solution, the precipitator solution and the complexing agent solution prepared in the step one into a reaction kettle at the flow rate of 100mL/min, controlling the reaction temperature to be 60 ℃, the pH value to be 11.50-12.50 and the rotation speed of the reaction kettle to be 450r/min, and reacting to generate the high-nickel single crystal ternary precursor slurry.

Step three, post-treatment stage: and D, performing filter pressing, washing and drying on the high-nickel single crystal ternary precursor slurry prepared in the step two to prepare the high-nickel single crystal ternary precursor.

The high-nickel single crystal ternary precursor is secondary particles formed by aggregation of primary particles, and the primary particles are flaky and 75.7 of the thicknessThe nm, high nickel single crystal ternary precursor D50 is 3.613um, and the tap density is 1.69 g/cm³The specific surface area of the powder was 13.759 m²/g。

Comparative example 3:

a method for preparing a ternary precursor, which is different from that of example 2 in that no potassium manganese (iii) oxalate is added in the step one, and the rest of the reaction conditions and parameters are the same as those of example 2.

Comparative example 4:

a method for preparing a ternary precursor, which is different from that of example 2 in the proportion of potassium manganese (III) oxalate added in the first step, wherein Mn of the potassium manganese (III) oxalate is different from that of the potassium manganese (III) oxalate³⁺With Mn²⁺The molar ratio of (a) to (b) was 5, and the remaining reaction conditions and parameters were the same as in example 2.

The data of the ternary precursor finished products prepared in the embodiments 1-2 and the comparative examples 1-4 are shown in a table 1, and the data of the related electrochemical performance of the ternary cathode material prepared by adopting the finished product are shown in a table 2:

TABLE 1 ternary precursor product data for the examples and comparative examples

	D50(um)	Thickness of primary particle (nm)	Tap density (g/cm)³）	Specific surface area (m)²/g）
					Example 1	3.713	98.7	1.69	13.57
Comparative example 1	3.786	263.6	1.93	6.87
					Comparative example 2	3.695	18.7	1.50	20.57
Example 2	3.618	75.7	1.69	14.76
					Comparative example 3	3.654	153.2	1.91	6.10
Comparative example 4	3.691	30.9	1.56	19.53

TABLE 2 electrochemical performance data of ternary cathode materials prepared from ternary precursors of examples and comparative examples

	Capacity retention rate after 100 cycles at 45 ℃, 1C
		Example 1	92.00%
Comparative example 1	88.00%
		Comparative example 2	86.00%
Example 2	88.40%
		Comparative example 3	83.90%
Comparative example 4	82.00%

As can be seen from Table 1, under the conditions similar to those of the finished product D50, as the addition amount of potassium manganese (III) oxalate is increased, the thickness of the primary particles of the obtained product is gradually reduced, the corresponding tap density is reduced, and the specific surface area is increased. As can be seen from Table 2, when the thickness of the primary particles of the precursor reaches 50-110 nm, the single crystal cathode material prepared from the precursor has the best high-temperature cycle performance. Therefore, the primary particles of the high-nickel single crystal ternary precursor can be effectively refined by controlling the adding amount of the potassium manganese (III) oxalate, and the high-nickel single crystal ternary cathode material with the optimal performance is obtained.

Referring to the attached drawings 1-8, it can be seen that the thickness of the primary particles of the precursor prepared by mixing potassium manganese (III) oxalate with the molten metal is uniform, and the pre-oxidation effect is achieved. With the increase of the addition amount of potassium manganese (III) oxalate, the primary particles of the precursor become thinner and the porosity is increased, which corresponds to the detection results of the ratio table in the first table.

The above embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention by this means. All equivalent changes and modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.

Claims

1. A preparation method of a high-nickel single crystal ternary precursor is characterized by comprising the following steps: the preparation method comprises the following steps:

step one, a pretreatment stage: mixing Ni²⁺、Co²⁺、Mn²⁺And potassium manganese (III) oxalate according to the formula Ni_xCo_yMn_z(OH)₂Preparing soluble mixed salt solution with the molar ratio of the corresponding elements in the solution, wherein x + y + z is 1, x is more than or equal to 0.85 and less than 1.0, y is more than 0 and less than 0.15, z is more than 0.01 and less than 0.15, and Mn of potassium manganous (III) oxalate is³⁺With Mn²⁺The molar ratio of (a) to (b) is 2-4, so that primary particles of secondary particles are refined, and the specific surface area is increased; the pH value of the mixed salt solution is 4.5-5.5;

preparing a sodium hydroxide solution or a potassium hydroxide solution as a precipitator solution, and an ammonia water solution as a complexing agent solution;

step two, reaction stage: adding the mixed salt solution, the precipitator solution and the complexing agent solution prepared in the step one into a reaction kettle under the stirring condition, controlling the reaction temperature to be 50-70 ℃, the pH value to be 11.50-12.50 and the rotating speed of the reaction kettle to be 350-600 r/min, and reacting to generate high-nickel single crystal ternary precursor slurry;

step three, post-treatment stage: carrying out filter pressing, washing and drying on the high-nickel single crystal ternary precursor slurry prepared in the step two to prepare a high-nickel single crystal ternary precursor;

the high-nickel single crystal ternary precursor is secondary particles formed by aggregation of primary particles, the primary particles are flaky and have the thickness of 50-110 nm, the D50 of the high-nickel single crystal ternary precursor is 3.2-3.8 um, and the tap density is 1.65-1.90 g/cm³The specific surface area is 8 to 18 m²/g。

2. The method for preparing a high-nickel single-crystal ternary precursor according to claim 1, characterized in that: step one Ni in the mixed salt solution²⁺The concentration is 100-113 g/L, Co²⁺The concentration is 1-18 g/L, Mn²⁺Ni in a concentration of 1 to 16 g/L²⁺、Co²⁺And Mn²⁺The total concentration of the three metal ions is 117-120 g/L.

3. The method for preparing a high-nickel single-crystal ternary precursor according to claim 1, characterized in that: in the first step, 20-40% by mass of sodium hydroxide or potassium hydroxide solution is prepared as a precipitant solution.

4. The method for preparing a high-nickel single-crystal ternary precursor according to claim 1, characterized in that: and step one, preparing an ammonia water solution with the mass fraction of 3-6% as a complexing agent solution.

5. The method for preparing a high-nickel single-crystal ternary precursor according to claim 1, characterized in that: and in the second step, the mixed salt solution, the precipitator solution and the complexing agent solution are added into the reaction kettle at a flow rate of 80-150 mL/min.

6. The method for preparing a high-nickel single-crystal ternary precursor according to claim 1, characterized in that: in the first step, nickel sulfate, cobalt sulfate and manganese sulfate are selected to prepare a soluble mixed salt solution.

7. The high-nickel single crystal ternary precursor prepared by the preparation method according to any one of claims 1 to 6.