CN116588993B

CN116588993B - Ternary precursor, preparation method thereof, lithium battery positive electrode material and lithium battery

Info

Publication number: CN116588993B
Application number: CN202310869692.2A
Authority: CN
Inventors: 李然; 邢王燕; 宋方亨; 李观凤; 陈靖; 左美华
Original assignee: Yibin Guangyuan Lithium Battery Co ltd
Current assignee: Yibin Guangyuan Lithium Battery Co ltd
Priority date: 2023-07-17
Filing date: 2023-07-17
Publication date: 2023-09-26
Anticipated expiration: 2043-07-17
Also published as: CN116588993A

Abstract

The invention discloses a ternary precursor and a preparation method thereof, a lithium battery anode material and a lithium battery, and relates to the technical field of lithium batteries. The structure guiding agent is added into the base solution, and hydrogen peroxide solution is introduced into the nucleation stage as a structure improving agent by utilizing a hierarchical structure adjustment mode, so that primary particles can start to generate weak deformation; the precursor primary particles can be thinned by introducing sodium persulfate solution as a structure improver at the stage of continuous growth after nucleation, and the surface of the precursor primary particles presents staggered distribution, so that a radial porous structure with finer primary particles is obtained. The method can obtain thinner primary particles and larger porosity, and the characteristics ensure that the precursor has larger specific surface area and more ternary precursor surface active sites with high specific surface area, so that the ternary precursor is easier to undergo oxidation-reduction reaction in electrochemical reaction after lithiation, and the reaction rate is greatly improved, thereby improving the electrochemical performance of the battery, such as rate capability, cycle performance and the like.

Description

Ternary precursor, preparation method thereof, lithium battery positive electrode material and lithium battery

Technical Field

The invention relates to the technical field of lithium batteries, in particular to a ternary precursor, a preparation method thereof, a lithium battery anode material and a lithium battery.

Background

Lithium ion batteries have been widely used in electronic devices such as computers, mobile phones, cameras, and new energy automobiles. The positive electrode material of the lithium ion battery influences the price and the performance of the lithium ion battery, and is an important component of the lithium ion battery. The ternary precursor is key for preparing the lithium ion positive electrode material, and the research and the preparation of the ternary precursor link two industries of upstream nonferrous metal (nickel sulfate, cobalt sulfate, manganese sulfate and the like) and downstream positive electrode material.

The ternary precursor material is nickel cobalt manganese hydroxide, and the chemical formula is Ni _x Co _y Mn _1-x-y (OH) ₂ Is generally prepared by a hydroxide coprecipitation method. The coprecipitation method has the advantage that a plurality of metal ions are synchronously precipitated under the action of a precipitator, so that a precipitate with uniform components is obtained. Therefore, the properties are greatly affected by the raw materials and the preparation process, and different preparation processes and conditions directly affect the final properties. Wherein the ratio of nickel to manganese (x: y:1-x-y, x)<1，y<1) The design can be carried out according to the downstream materials and the requirements of battery customers, and the performance of the battery can be changed according to the different proportions of nickel, cobalt and manganese. Wherein, nickel mainly plays a role in increasing the discharge capacity of the positive electrode material, but the excessive Ni content can cause the reduction of the rate performance and the cycle performance of the battery; cobalt can improve the electronic conductivity of the material and improve the cycle performance, but the cobalt has the defects of lack of sources and higher cost; the presence of manganese can reduce the cost and improve the structural stability and safety of the material, but too high a Mn content will reduce the gram capacity of the material and easily break the layered structure of the material.

With the development of technology, the market has a higher demand for the capacity and rate charging of ternary precursors. Many researchers currently improve capacity performance and high rate performance by doping, cladding, increasing operating voltage, single crystal preparation, and the like. However, in these operations, the doping generally requires the addition of noble metal elements, both coating and increasing the operating voltage increase the cost of manufacture, and the process of single crystal preparation is also difficult to control.

In addition, ordered crystal structure and secondary particles of higher specific surface area can also increase the capacity and rate of the battery. Precursors of various morphologies have been reported, including radial, core-shell, petal, hollow, and the like. The radial structure can accelerate the intercalation and deintercalation of lithium ions, and has the advantages of good ploidy and good circularity, but the preparation process is difficult to control, the consistency of products is poor, and the safety is poor. Increasing the specific surface area of the ternary precursor can increase the number of surface active sites of the ternary precursor, so that the ternary precursor is easier to undergo oxidation-reduction reaction in electrochemical reaction, and the electrochemical performance of the battery is improved. The larger specific surface area can also improve the reaction rate of the battery in electrochemical reaction, thereby improving the power output capacity of the battery and making the battery more suitable for high-power application.

Therefore, the preparation of the ternary precursor with the radial crystal phase structure and the large specific surface has great application value in the aspects of improving the capacity and multiplying power of the battery.

In view of this, the present invention has been made.

Disclosure of Invention

The invention aims to provide a ternary precursor, a preparation method thereof, a lithium battery anode material and a lithium battery, and aims to improve the rate capability and the cycle performance of the battery.

The invention is realized in the following way:

in a first aspect, the present invention provides a method for preparing a ternary precursor, comprising: introducing the precipitant solution, the complexing agent solution, the first structure improver and the mixed salt solution containing nickel, cobalt and manganese into the base solution of the reaction kettle for reaction, and when the crystal grains in the reaction kettle grow to the crystal nucleus particle size, replacing the first structure improver with the second structure improver to continuously control the crystal grains to grow to the target particle size;

the first structure improver is hydrogen peroxide solution, and the second structure improver is sodium persulfate solution; the base solution contains a structure directing agent.

In an alternative embodiment, the concentration of the hydrogen peroxide solution is 0.5mol/L to 4.0mol/L and the concentration of the sodium persulfate solution is 0.1mol/L to 1.0mol/L.

In an alternative embodiment, the total concentration of nickel, cobalt and manganese in the mixed salt solution is 1.5mol/L-2.2mol/L, and the volume ratio of the mixed salt solution to the hydrogen peroxide solution which is introduced in one hour is 1000:8-12; the volume ratio of the mixed salt solution to the sodium persulfate solution is 1000:10-15 in one hour;

the molar ratio of nickel, cobalt and manganese in the mixed salt solution is x and y (1-x-y), wherein x is more than 0 and less than 1, y is more than 0 and less than 1, and 0 is more than 1-x-y is more than 1.

In an alternative embodiment, the base fluid contains a structure directing agent selected from at least one of monoethanolamine and diethanolamine;

the concentration of the structure directing agent in the base solution is 0.1g/L-5g/L;

the complexing agent solution is ammonia water, the ammonia value of the base solution is 5g/L-10g/L, and the pH value is 11.8-12.6.

In an alternative embodiment, the crystal nucleus particle size is 3 μm to 5 μm and the target particle size is 9 μm to 13 μm;

controlling the pH value in the system to be 11.8-12.6 in 3-5 h before the reaction by controlling the adding amount of the precipitant solution and the complexing agent solution, and then controlling the pH value in the system to be 10.5-11.8;

in the whole growth process, the ammonia value in the system is controlled to be 5g/L-10g/L, the reaction temperature is 50-70 ℃, and the stirring rotation speed is 500-1000 rpm/min;

the precipitant solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution and sodium carbonate solution.

In an alternative embodiment, the crystal growth is performed using a first reactor and a second reactor, the preparation method comprising:

adding base solution into a first reaction kettle and a second reaction kettle respectively, and respectively introducing a precipitator solution, a complexing agent solution, a first structure improver and a mixed salt solution containing nickel, cobalt and manganese to react under a protective atmosphere;

when the crystal grains in the reaction kettle grow to the crystal nucleus particle size, stopping feeding by the second reaction kettle, replacing the first structure improver with the second structure improver, and continuously introducing the second structure improver into the first reaction kettle to perform crystal grain growth;

when the grain diameter of the crystal in the first reaction kettle reaches 7-9 mu m, introducing crystal nuclei in the second reaction kettle into the first reaction kettle, and controlling the grain growth to the target grain diameter;

the materials in the second reaction kettle are introduced into the first reaction kettle at a flow rate of 5-30 mL/min.

In an alternative embodiment, the method further comprises: after the crystal grain size grows to the target grain size and a sufficient amount of products are prepared, sequentially aging, dehydrating and washing the materials, and then performing a post-treatment procedure;

the post-treatment process comprises iron removal, dehydration, drying and screening which are sequentially carried out.

In a second aspect, the present invention provides a ternary precursor prepared by the method of any one of the preceding embodiments.

In a third aspect, the present invention provides a lithium battery positive electrode material prepared from the ternary precursor of the foregoing embodiment.

In a fourth aspect, the present invention provides a lithium battery, which is prepared from the lithium battery cathode material of the foregoing embodiment.

The invention has the following beneficial effects: the structure guiding agent is added into the base solution, so that the dispersibility can be enhanced, and initial nucleation agglomeration is reduced; in the early stage of reaction, the crystal grain grows to the crystal nucleus granularity by utilizing a hierarchical structure adjustment mode, and hydrogen peroxide solution is introduced as a structure improver, so that primary particles can start to generate weak deformation, a precursor is slightly changed in structure, and a grown inner core is loose and porous; in the later stage of the reaction, the particle size grows to the particle size of the target product, and the precursor primary particles can be thinned by using sodium persulfate solution as a structure improver, and the precursor growing to the target particle size can obtain a radial porous structure with finer primary particles, wherein the precursor primary particles are distributed in a staggered manner on the surface. The preparation method provided by the invention can obtain thinner primary particles and larger porosity, and the characteristics of the preparation method enable the precursor to have larger specific surface area and more surface active sites of the ternary precursor with high specific surface area, so that the ternary precursor is easier to undergo oxidation-reduction reaction in electrochemical reaction after lithiation, so that the reaction rate is greatly improved, and the electrochemical performance of the battery, such as rate performance, cycle performance and the like, is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a cross-sectional view of a precursor obtained in example 1;

FIG. 2 is a scanning electron microscope image of the precursor obtained in comparative example 1;

FIG. 3 is a cross-sectional view of the precursor of comparative example 2;

FIG. 4 is a cross-sectional view of the precursor obtained in comparative example 3;

fig. 5 is a graph showing the rate performance of the products prepared in examples and comparative examples.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

The embodiment of the invention provides a preparation method of a ternary precursor, which comprises the following steps:

s1, batching

Respectively preparing a precipitator solution, a complexing agent solution, a mixed salt solution containing nickel, cobalt and manganese, a base solution, a first structure improver and a second structure improver for standby.

The precipitant solution is used for adjusting the pH value of the base solution or the reaction system, and the precipitant solution is at least one selected from sodium hydroxide solution, potassium hydroxide solution and sodium carbonate solution, and can be any one or more of the above. Preferably 10% -25% by mass of sodium hydroxide solution.

The complexing agent solution may be, but is not limited to, aqueous ammonia, and may have a mass concentration of 5% to 21%.

The mixed salt solution contains nickel, cobalt and manganese at the same time, the specific proportion of the nickel, cobalt and manganese is not limited, the proportion of the nickel, cobalt and manganese in the target product can be adjusted, and the mixed salt solution can be controlledThe molar ratio of nickel, cobalt and manganese is x, y (1-x-y), wherein x is more than 0 and less than 1, y is more than 0 and less than 1, x-y is less than 1, and the chemical formula of the obtained ternary precursor product is Ni _x Co _y Mn _1-x-y (OH) ₂ 。

In some embodiments, the total concentration of nickel cobalt manganese in the mixed salt solution is 1.5mol/L to 2.2mol/L, such as may be 1.5mol/L, 1.6mol/L, 1.7mol/L, 1.8mol/L, 1.9mol/L, 2.0mol/L, 2.1mol/L, 2.2mol/L, and the like. If the concentration of the metal ions is too low, the subsequent precipitation process is not facilitated, and if the concentration of the metal ions is too high, the complete dissolution of the metal salts is not facilitated.

Specifically, the preparation process of the mixed salt solution comprises the following steps: according to the stoichiometric ratio of the designed precursor, the mass of the soluble nickel salt, cobalt salt and manganese salt required by preparing a certain volume of mixed salt solution is calculated, and then the salt is put into a salt preparation kettle for constant volume. And after the salt is dissolved, detecting the main content of the salt solution, and ensuring the accuracy and the qualitative of the proportion and the concentration. The soluble nickel salt, cobalt salt and manganese salt can be any one of sulfate, nitrate and hydrochloride thereof, for example, the nickel salt can be any one of nickel sulfate, nickel nitrate and nickel chloride.

Preparing a base solution according to the designed ammonia value and pH, wherein the preparation process of the base solution comprises the following steps: adding pure water, adding a structure directing agent, stirring for dissolution, adding a complexing agent to adjust the ammonia value, and adding a precipitant to adjust the pH. The complexing agent can be the complexing agent solution, the precipitant can be the precipitant solution, and the aggregation of particles in the nucleation period can be effectively avoided by adding the structure directing agent, so that reaction conditions are provided for the growth of crystal nuclei into single spherical products.

In some embodiments, the ammonia and pH are controlled within the above ranges, preferably at a pH of 11.8-12.6, at a pH of 5g/L to 10g/L in the base fluid, to nucleate at higher pH. Specifically, the ammonia value in the base solution can be 5g/L, 6g/L, 7g/L, 8g/L, 9g/L, 10g/L, etc., and the pH value can be 11.8, 12.0, 12.2, 12.4, 12.6, etc.

If the first reaction vessel and the second reaction vessel are used for crystal growth, the same two portions of the base solution are required to be prepared and placed in the two reaction vessels, respectively.

In some embodiments, the structure directing agent is at least one selected from monoethanolamine and diethanolamine, and can be any one or two of the above, and the concentration of the structure directing agent in the base solution is 0.1g/L to 5g/L, so as to effectively avoid agglomeration of particles during nucleation. Specifically, the concentration of the structure directing agent in the base liquid may be 0.1g/L, 0.5g/L, 1.0g/L, 2.0g/L, 3.0g/L, 4.0g/L, 5.0g/L, etc.

The first structure-improving agent may weakly deform the precursor, and a hydrogen peroxide solution may be used as the first structure-improving agent. The preparation process of the first structure improver comprises the following steps: the hydrogen peroxide is diluted to control the concentration of the hydrogen peroxide solution to be 0.5mol/L to 4.0mol/L, for example, 0.5mol/L, 1.0mol/L, 2.0mol/L, 3.0mol/L, 4.0mol/L, etc.

The second structure-improving agent may be a sodium persulfate solution as the second structure-improving agent, in which primary particles of the precursor are thinned and the surface of the precursor is alternately distributed. The preparation process of the second structure improver comprises the following steps: sodium persulfate and water are mixed, and the concentration of the sodium persulfate solution is controlled to be 0.1mol/L to 1.0mol/L, for example, 0.1mol/L, 0.3mol/L, 0.5mol/L, 0.7mol/L, 1.0mol/L, etc.

S2, crystal growth

The crystal growth mode is crystal nucleus-growth, specifically: and introducing the precipitant solution, the complexing agent solution, the first structure improver and the mixed salt solution containing nickel, cobalt and manganese into the base solution of the reaction kettle for reaction, and when the crystal grains in the reaction kettle grow to the crystal nucleus particle size, replacing the first structure improver with the second structure improver to continuously control the crystal grains to grow to the target particle size. The first stage is filled with weaker hydrogen peroxide, the second stage is filled with stronger sodium persulfate, the form of weak deformation and strong deformation can enable the crystal structure to change gradually in the growth process, the stable structure can be maintained after lithiation sintering, the structure can be still kept stable after charging and discharging, and therefore a better circulating effect is achieved.

The first stage is filled with weaker hydrogen peroxide solution, so that primary particles can start to generate weak deformation, the precursor achieves slight structural change, and the grown inner core is loose and porous; when the grain size grows to the crystal nucleus grain size, the structure improvement reagent is replaced by a strong sodium persulfate solution, so that primary particles of the precursor can be thinned, staggered distribution is shown on the surface, and the precursor growing to the target grain size can obtain a radial porous structure with finer primary particles.

In some embodiments, the volume ratio of mixed salt solution to hydrogen peroxide solution introduced within one hour is 1000:8-12; the volume ratio of the mixed salt solution to the sodium persulfate solution is 1000:10-15 in one hour. On the premise that the concentration of the mixed salt solution, the hydrogen peroxide solution and the sodium persulfate solution are controlled within the above range, the better structure improvement effect is achieved by controlling the dosage of the structure improver in the two-step growth stage, and the volume ratio is controlled on the basis of the concentration range of the solution.

Specifically, the volume ratio of the mixed salt solution to the hydrogen peroxide solution introduced in one hour can be 1000:8, 1000:9, 1000:10, 1000:11, 1000:12 and the like; the volume ratio of the mixed salt solution to the sodium persulfate solution introduced within one hour can be 1000:10, 1000:11, 1000:12, 1000:13, 1000:14, 1000:15, etc.

In some embodiments, the crystal nucleus particle size is 3 μm to 5 μm, the target particle size is 9 μm to 13 μm, and the target particle size may be adjusted according to the product requirements, not limited to the above range. Specifically, the crystal nucleus particle diameter may be 3 μm, 4 μm, 5 μm, etc., and the target particle diameter may be 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, etc.

In some embodiments, the pH in the system during growth to the seed particle size is controlled to be 11.8-12.6 and the pH in the system during growth from the seed particle size to the target particle size is controlled to be 10.5-11.8 by controlling the amount of precipitant solution added. Nucleation at a higher pH is controlled and then growth at a lower pH is controlled to improve product grain uniformity.

Specifically, the pH in the system during growth to the crystal nucleus particle size may be 11.8, 12.0, 12.2, 12.4, 12.6, etc., and the pH in the system during growth from the crystal nucleus particle size to the target particle size may be 10.5, 10.8, 11.0, 11.2, 11.4, 11.6, 11.8, etc.

In some embodiments, the ammonia value in the system is controlled to be 5g/L-10g/L in the whole growth process by adjusting the addition amount of ammonia water, and the ammonia value is consistent with the base solution, such as 5g/L, 6g/L, 7g/L, 8g/L, 9g/L, 10g/L and the like. By strictly controlling the pH value and the ammonia value in the reaction process, newly generated primary particles can grow orderly, and finally a radial structure is formed.

In the whole growth process, the reaction temperature is 50-70 ℃, and the stirring rotation speed is 500-1000 rpm/min. Specifically, the reaction temperature may be 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃ and the like, and the stirring rotation speed may be 500rpm/min, 600rpm/min, 700rpm/min, 800rpm/min, 900rpm/min, 1000rpm/min and the like.

In some embodiments, the precursor product may be prepared using a continuous process to increase production efficiency, and crystal growth may be performed using a first reactor and a second reactor, the preparation process comprising: (1) Adding base solution into a first reaction kettle and a second reaction kettle respectively, and respectively introducing a precipitator solution, a complexing agent solution, a first structure improver and a mixed salt solution containing nickel, cobalt and manganese to react under a protective atmosphere, so as to control the ammonia value and the pH value of the reaction solution; (2) When the crystal grains in the reaction kettle grow to the crystal nucleus particle size, stopping feeding the second reaction kettle, wherein the reaction kettle material is crystal nucleus, replacing the first structure improver with the second structure improver, and continuously introducing the second structure improver into the first reaction kettle for crystal grain growth; (3) When the grain size of the crystals in the first reaction kettle reaches 7-9 mu m (such as 7 mu m, 8 mu m, 9 mu m and the like), the materials in the second reaction kettle are introduced into the first reaction kettle, and the grain size of the products in the first reaction kettle is regulated, so that the first reaction kettle for continuous reaction can continuously discharge.

Specifically, the materials in the second reaction kettle are introduced into the first reaction kettle, and the flow is controlled to be 5mL/min-30mL/min, for example, 5mL/min, 10mL/min, 15mL/min, 20mL/min, 25mL/min, 30mL/min and the like.

It is added that before the reaction, a protective gas is introduced into the closed reaction vessel to replace air, so as to prevent uncontrolled natural oxidation, and the protective atmosphere can be nitrogen, but is not limited to the method.

S3, aging and washing

And after the crystal grain size grows to the target grain size and can be stably discharged, starting overflow products to an ageing kettle for ageing, and then centrifugally dehydrating and washing to remove impurities such as sodium, sulfur and the like.

Specifically, the precursor can be continuously dissolved and recrystallized in the solution in the aging process, so that sodium and sulfur coated in the crystal are released, and impurity ions are effectively reduced. Meanwhile, the precursor rearranges according to the inherent lattice orientation, so that the precursor has better crystallinity.

S4, post-treatment process

The post-treatment process is adjusted according to the product requirement, and can comprise iron removal, dehydration, drying, screening and the like, so as to obtain a target ternary precursor, and finally sub-packaging.

Specifically, the product with qualified impurity content is subjected to post-treatment procedures, the means of deironing and dehydrating are not limited, and the existing treatment method can be adopted. Drying can be carried out at 60-140 ℃ for 10-24 hours.

The embodiment of the invention also provides a ternary precursor which is prepared by the preparation method and has good electrochemical performance.

It should be noted that the prepared ternary positive electrode material precursor has good sphericity, no agglomerated secondary particles and the product morphology is as follows: the surface presents staggered elongated primary particles, the porosity is high, and the section surface presents radial shape with complete crystal structure. The radial crystalline phase structure can accelerate the intercalation and deintercalation of lithium ions, and has the advantages of good ploidy and good circularity.

The embodiment of the invention also provides a lithium battery positive electrode material which is prepared from the ternary precursor, has good cycle performance and multiplying power performance, can be further prepared into a lithium battery, and has wide application prospect due to excellent electrochemical performance.

The features and capabilities of the present invention are described in further detail below in connection with the examples.

Example 1

The embodiment provides a preparation method of a ternary precursor, which comprises the following steps:

(1) Proportioning materials

Preparing three metal sulfates corresponding to Ni: co: mn=98:1:1 into a metal salt solution a with the total concentration of nickel, cobalt and manganese of 2mol/L by using pure water;

preparing ammonia water with the mass concentration of 21% as a complexing agent b;

sodium hydroxide with the mass concentration of 32% is used as a precipitator c;

diluting hydrogen peroxide into a solution d of 0.5mol/L by pure water;

sodium persulfate was formulated as a solution e of 0.8 mol/L.

(2) Crystal growth

Adding half-kettle pure water into a A, B reaction kettle, adding diethanolamine to the concentration of 0.5g/L, introducing nitrogen to perform air replacement, opening stirring and heating, designing the rotating speed to be 900rpm/min, adding ammonia water and liquid alkali to adjust the ammonia concentration of the bottom solution of the reaction kettle to be 5.5 g/L and the pH value to be 11.9. And after the base solution is qualified, introducing a, b, c, d solution into a reaction kettle, wherein the flow rate of a is 2000 mL/h, the flow rate of b is 150 mL/h, c is PID control, and the flow rate of d is 20 mL/h. After maintaining this pH and ammonia value for 3 hours, the pH was slowly lowered to 11.65, entering the growth phase.

When D50 in the A, B reaction kettle grows to 4 mu m, the reaction kettle B stops feeding, the flow rate of a lifted by the reaction kettle A is 4000 mL/h, the flow rate of B is 280 mL/h, the solution D is replaced by the solution e, the flow rate is 50 mL/h until D50 grows to 8 mu m, crystal nuclei in the reaction kettle B are introduced into the reaction kettle A at the flow rate of 10mL/min, the flow rate of the crystal nuclei is regulated according to the grain size growth condition at the later stage (if the grain size in the reaction kettle A is too large and exceeds 10 mu m, the flow rate of the crystal nuclei is increased, if the grain size in the reaction kettle A is too small and is smaller than 10 mu m, the flow rate of the crystal nuclei is properly reduced), and the feeding is stopped until the target weight product is produced.

(3) Post-treatment

And (3) ageing the product overflowed from the kettle A in the step (2) in an ageing kettle for 5h, then dehydrating in a reflux centrifugation mode, washing Na and S in the precursor by dilute alkali and hot pure water respectively, then demagnetizing, drying at 60 ℃ for 24 hours, sieving after moisture is qualified, and obtaining a precursor with a radial crystal phase structure and a large specific surface, wherein the sectional view is shown in figure 1.

As can be seen from fig. 1, the ternary precursor has a cross section with an obvious radial structure, the inner core is compact, and after the granularity is 4 μm, the thickness of the primary particles is gradually thinned due to the change of sodium peroxide with strong chemical property, the formed lamellar radial structure is more obvious, and the primary particles on the surface are in slender staggered distribution.

Comparative example 1

The only difference from example 1 is that: the base solution was not added with the structure directing agent diethanolamine, and the other steps were described in example 1.

The precursor prepared in this comparative example was similar to the surface of example 1, and the electron microscopy image thereof was shown in fig. 2. As can be seen from FIG. 2, the electron microscope image shows uniform distribution of large, medium and small spheres, which is a typical continuous product, and the dispersion is poor due to the fact that no structure directing agent is added in the base solution in the case, and the finally prepared product has more aggregation and twinning phenomena. The hierarchical structure adjustment process is identical to that of example 1, so that the surface primary particles have similar shapes and pore distribution to those of example 1, and the surface primary particles exhibit staggered elongated primary particles and good porosity.

Comparative example 2

The only difference from example 1 is that: in the step (2), only the solution d is adopted in the crystal growth process, and the operation of replacing the solution d with the solution e is not performed. The method comprises the following steps:

(1) Proportioning materials

hydrogen peroxide was diluted with pure water to a solution d of 0.5 mol/L.

(2) Crystal growth

Adding half-kettle pure water into a A, B reaction kettle, adding diethanolamine to ensure that the concentration is 0.5g/L, introducing nitrogen to perform air replacement, opening stirring and heating, designing the rotating speed to be 900rpm/min, the temperature to be 60 ℃, adding ammonia water and liquid alkali to regulate the ammonia concentration of the bottom solution of the reaction kettle to be 5.5 g/L, and the pH value to be 11.9. And after the base solution is qualified, introducing a, b, c, d solution into a reaction kettle, wherein the flow rate of a is 2000 mL/h, the flow rate of b is 150 mL/h, c is PID control, and the flow rate of d is 20 mL/h. After maintaining this pH and ammonia value for 3 hours, the pH was slowly lowered to 11.65, entering the growth phase.

When D50 grows to 4 mu m, the reaction kettle B stops feeding, the flow rate of the lifting a of the reaction kettle A is 4000 mL/h, the flow rate of the B of the reaction kettle A is 280 mL/h, the flow rate of the D of the reaction kettle is 50 mL/h, the flow rate of the solution D is regulated according to the actual structural change condition in the later stage until D50 grows to 8 mu m, crystal nuclei in the reaction kettle B are introduced into the reaction kettle A at the flow rate of 10mL/min, the flow rate of the crystal nuclei is regulated according to the particle size growth condition in the later stage until the target weight product is produced, and the feeding is stopped.

(3) Post-treatment

And (3) ageing the product overflowed from the kettle A in the step (2) in an ageing kettle for 5h, then dehydrating in a reflux centrifugation mode, washing Na and S in the precursor by dilute alkali and hot pure water respectively, then demagnetizing, drying at 60 ℃ for 24 hours, sieving after moisture is qualified, and obtaining a precursor with a radial crystal phase structure and a large specific surface, wherein the sectional view is shown in figure 3.

As can be seen from FIG. 3, the ternary precursor has a cross section with an obvious radial structure, the inner core is compact, and compared with the method in example 1, the single-stage weak deformation method is adopted, so that the prepared precursor has thicker primary particles and larger pores.

Comparative example 3

The only difference from example 1 is that: only solution e is used in the crystal growth process of step (2). The method comprises the following steps:

(1) Proportioning materials

sodium persulfate was formulated as a solution e of 0.8 mol/L.

(2) Crystal growth

Adding half-kettle pure water into a A, B reaction kettle, adding diethanolamine to ensure that the concentration is 0.5g/L, introducing nitrogen to perform air replacement, opening stirring and heating, designing the rotating speed to be 900rpm/min, the temperature to be 60 ℃, adding ammonia water and liquid alkali to regulate the ammonia concentration of the bottom solution of the reaction kettle to be 5.5 g/L, and the pH value to be 11.9. And after the base solution is qualified, introducing a, b, c, e solution into the reaction kettle. Wherein, the flow rate of a is 2000 mL/h, the flow rate of b is 150 mL/h, c is PID control, and the flow rate of e is 20 mL/h. After maintaining this pH and ammonia value for 3 hours, the pH was slowly lowered to 11.65, entering the growth phase.

When D50 grows to 4 mu m, the reaction kettle B stops feeding, the flow rate of the lifting a of the reaction kettle A is 4000 mL/h, the flow rate of the B of the reaction kettle A is 280 mL/h, the flow rate of the e of the reaction kettle is 50 mL/h, the flow rate of the solution e is regulated according to the actual structural change condition in the later stage until D50 grows to 8 mu m, crystal nuclei in the reaction kettle B are introduced into the reaction kettle A at the flow rate of 10mL/min, the flow rate of the crystal nuclei is regulated according to the particle size growth condition in the later stage until the target weight product is produced, and the feeding is stopped.

(3) Post-treatment

And (3) ageing the product overflowed from the kettle A in the step (2) in an ageing kettle for 5h, then dehydrating in a reflux centrifugation mode, washing Na and S in the precursor by dilute alkali and hot pure water respectively, then demagnetizing, drying at 60 ℃ for 24 hours, sieving after moisture is qualified, and obtaining a precursor with a radial crystal phase structure and a large specific surface, wherein the sectional view is shown in figure 4.

As can be seen from fig. 4, the cross section of the ternary precursor shows an obvious radial structure, the inner core is compact, and compared with the embodiment 1, the comparative example adopts a single-stage strong deformation method, so that the thickness of primary particles of the prepared precursor is thinner, the pores are smaller, and the porosity is high.

Test example 1

The precursors prepared in example 1, comparative example 2, and comparative example 3 were subjected to physical index test and electrical property test, respectively, and the physical indexes of the tests are shown in table 1.

TABLE 1 physical Properties of four precursors

Test example 2

The precursors prepared in the examples and comparative examples were tested for electrochemical properties and the structures are shown in fig. 5 and table 2.

The testing method comprises the following steps: mixing the precursor and lithium carbonate according to a ratio of 1:1.05, calcining at 700 ℃ for 15 h, taking out, grinding and crushing to finally obtain a positive electrode material (A, A, A2 and A3, A represents the positive electrode material obtained by preparing the precursor of the example 1, and A1-A3 represent the positive electrode materials obtained by preparing the precursors of the comparative examples 1-3 respectively), and then performing electrochemical performance measurement.

Electrochemical performance testing method: four positive electrode materials were subjected to rate and cycle performance tests (test temperature 30 ℃) at current densities of 0.1C, 0.5C, 1.0C, 2.0C, 5.0C (1.0C =180 mA h/g), respectively.

As can be seen from the magnification graph of fig. 5, the release capacities of the products A, A, A2, A3 at high magnification (5.0C) are 82.9%, 63.3%, 76.6%, 69.8% at 0.1C, respectively. Therefore, the precursor prepared in example 1 has the best rate performance.

Table 2A, A, A2, A3 cycle performance parameter table

As can be seen from table 2, the positive electrode materials prepared in examples and comparative examples have initial specific capacities in the range of 220 to 235 mAh/g in the charge-discharge performance test of the first round 0.1 to C, wherein the active material obtained in example 1 has the highest initial specific discharge capacity and the highest capacity retention after 50 cycles of 0.5C, and the best performance. Therefore, the dispersibility is improved by adding the structure directing agent into the base solution, the reaction condition is strictly controlled, and the ternary precursor prepared by hierarchical structure adjustment has high sphericity, better radial crystal phase structure and larger specific surface area, and can effectively improve the cycle performance of the anode material, thereby improving the electrochemical performance of the material.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method of preparing a ternary precursor comprising: introducing a precipitant solution, a complexing agent solution, a first structure improver and a mixed salt solution containing nickel, cobalt and manganese into a base solution of a reaction kettle for reaction, and when crystal grains in the reaction kettle grow to the grain size of crystal nuclei, replacing the first structure improver with a second structure improver to continuously control the crystal grains to grow to the target grain size;

wherein the first structure improving agent is hydrogen peroxide solution, and the second structure improving agent is sodium persulfate solution; the base solution contains a structure guiding agent;

the structure directing agent is at least one selected from monoethanolamine and diethanolamine;

the grain size of the crystal nucleus is 3 μm-5 μm.

2. The method according to claim 1, wherein the concentration of the hydrogen peroxide solution is 0.5mol/L to 4.0mol/L, and the concentration of the sodium persulfate solution is 0.1mol/L to 1.0mol/L.

3. The preparation method according to claim 2, wherein the total concentration of nickel, cobalt and manganese in the mixed salt solution is 1.5mol/L-2.2mol/L, and the volume ratio of the mixed salt solution to the hydrogen peroxide solution which is introduced in one hour is 1000:8-12; the volume ratio of the mixed salt solution to the sodium persulfate solution is 1000:10-15 in one hour;

the molar ratio of nickel, cobalt and manganese in the mixed salt solution is x:y (1-x-y), wherein x is more than 0 and less than 1, y is more than 0 and less than 1, and 0 is more than 1-x-y is more than 1.

4. The method of claim 1, wherein the concentration of the structure directing agent in the base fluid is 0.1g/L to 5g/L;

5. The method according to claim 4, wherein the target particle diameter is 9 μm to 13 μm;

controlling the pH value in a system within 3-5 h before reaction to be 11.8-12.6 by controlling the adding amount of the precipitant solution, and then controlling the pH value in the system to be 10.5-11.8;

6. The method according to claim 4, wherein the crystal growth is performed using a first reaction vessel and a second reaction vessel, the method comprising:

adding the base solution into the first reaction kettle and the second reaction kettle respectively, and respectively introducing the precipitator solution, the complexing agent solution, the first structure improver and the mixed salt solution containing nickel, cobalt and manganese for reaction under a protective atmosphere;

and the materials in the second reaction kettle are introduced into the first reaction kettle at a flow rate of 5-30 mL/min.

7. The method of manufacturing according to claim 1, further comprising: after the crystal grain size grows to the target grain size and a sufficient amount of products are prepared, sequentially aging, dehydrating and washing the materials, and then performing a post-treatment procedure;

8. A ternary precursor prepared by the preparation method of any one of claims 1-7.

9. A lithium battery cathode material prepared by the ternary precursor of claim 8.

10. A lithium battery prepared by the lithium battery cathode material of claim 9.