A nickel-cobalt-manganese ternary cathode material, its preparation method and application

Abstract

The present invention discloses a nickel-cobalt-manganese ternary cathode material, a preparation method thereof and an application thereof, belonging to the technical field of lithium ion battery materials. The preparation method of the material comprises the following steps: dissolving nickel salts, cobalt salts and manganese salts in a solvent, adding a mixed solution composed of an organic carboxylic acid and ammonia water to obtain a solution B; preparing a solution C containing lithium bicarbonate and ammonium bicarbonate; mixing the solution B and the solution C and then carrying out a hydrothermal reaction to obtain a precursor of the ternary cathode material, and roasting the precursor to obtain the nickel-cobalt-manganese ternary cathode material. During the above hydrothermal reaction process, the pyrolysis of bicarbonate and the precipitation of four metal ions of nickel, cobalt, manganese and lithium occur simultaneously in the whole system, so that nickel, cobalt, manganese and lithium are uniformly distributed in the prepared precursor, and the migration paths of various elements in the subsequent calcination process of the precursor with uniform distribution of each component are short, which is beneficial to the formation of a lamellar phase and the integrity of the material lattice, thereby playing a role in improving the electrochemical performance of the material.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and particularly relates to a nickel-cobalt-manganese ternary cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] The nickel-cobalt-manganese ternary cathode material is a key lithium-ion battery material with the chemical formula LiNi x Co y Mn 1-x-y O2, where x and y represent the proportions of nickel, cobalt, and manganese, which can be adjusted according to actual needs. It is used for the cathode of lithium-ion batteries and has various advantages, including high voltage resistance, high specific capacity, and low cobalt content, etc. This makes it have broad prospects in electronic products and power applications and become an important pillar in the field of new energy materials. In recent years, due to the rapid rise and continuous expansion of the electric vehicle market, the demand for nickel-cobalt-manganese ternary cathode materials has also shown a rapid growth trend and is expected to maintain high-speed growth in the next few years.

[0003] Meanwhile, the nickel-cobalt-manganese ternary cathode material industry has also achieved remarkable results in technological innovation. On the one hand, by optimizing the material ratio and preparation process, the energy density and cycle stability of the material have been improved; on the other hand, by introducing new additives and modification technologies, the thermal stability and safety of the material have been improved. These technological innovations not only promote industrial upgrading but also lay a solid foundation for the sustainable development of the industry.

[0004] Currently, the mainstream method for preparing the cathode of ternary cathode materials is to mix two powders, namely a ternary cathode precursor, generally hydroxide of nickel, cobalt, and manganese, and lithium carbonate or lithium hydroxide, at high speed to obtain a mixed powder containing four elements of lithium, nickel, cobalt, and manganese, and then subject the mixed powder to aerobic calcination and pulverization to obtain the ternary cathode material. The disadvantage of this method is that it is difficult to make the components in the cathode material distribute evenly during powder mixing, thus restricting the performance of the material. In view of the defect of powder mixing, there are also studies in the prior art to prepare ternary materials in a wet environment, but there are still some problems, such as: in order to ensure the sufficiency and uniformity of the reaction between raw materials, the required environment often needs high temperature and high pressure, resulting in harsh preparation process conditions, high equipment investment, and high cost investment; when using coprecipitation for raw material mixing, it is difficult to control the precipitation rate between reactants, resulting in too fast precipitation and thus causing the problem of uneven phase dispersion, etc. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a nickel-cobalt-manganese ternary cathode material, a preparation method thereof, and an application thereof. By improving the preparation process of the ternary cathode material, the present invention makes the phase of the ternary cathode material more uniform and obtains a product with good electrochemical performance.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for preparing a nickel-cobalt-manganese ternary cathode material, comprising the following steps:

[0008] (1) Preparation of transition metal solution: Using soluble salts of nickel, cobalt, and manganese, such as nickel sulfate, cobalt sulfate, manganese sulfate, or nickel chloride, cobalt chloride, manganese chloride, etc., as the source of nickel, cobalt, and manganese metal ions, dissolve them in a solvent to obtain solution A (transition metal salt solution). The solvent can be pure water, a mixed solvent composed of pure water and an alcohol reagent such as ethanol or ethylene glycol. The total concentration of nickel, cobalt, and manganese metal ions in solution A is 1 - 2.5 mol / L. When the concentration of nickel, cobalt, and manganese metal ions in solution A is too low, the metal nucleation and growth processes in the liquid phase will be slow, and at the same time, the solid content of the resulting slurry will also be low, resulting in poor economic efficiency. If the metal ion concentration is too high, on the one hand, it will cause more metal salts to be insoluble, and on the other hand, it will cause the nucleation and growth processes in the liquid phase to be too fast to effectively control the reaction process.

[0009] (2) Solution complexation and pH adjustment: Add a mixed solution composed of an organic carboxylic acid and ammonia water to solution A to obtain solution B with a pH of 6 - 8. Preferably, the organic carboxylic acid is citric acid or acetic acid, and the molar ratio of NH₃·H₂O to the organic carboxylic acid in the mixed solution is (1.5 - 3):1, that is, the amount of ammonia water used is more than that of the organic carboxylic acid. This is because when citric acid and ammonia water are mixed in equal moles, the pH can be considered neutral and will not affect the pH of the system. In the present invention, the transition metal salt solution is generally acidic. In order to adjust its pH to neutral, ammonia water is required to be more than citric acid. Preferably, the molar ratio of NH₃·H₂O to citric acid is limited to (1.5 - 3):1. The mixed solution plays a role in complexing transition metal ions and adjusting the pH range. Its principle of action is as follows: Citric acid or acetic acid contains carboxyl groups and is itself an organic substance, which can be completely removed from the material under the action of high temperature during the subsequent calcination process and will not affect the material properties due to residual products. The principle of complexation of the mixed solution is as follows: It contains carboxylic acid groups and amino groups. The carboxylic acid groups and amino groups can form multidentate coordination bonds with metal ions. Compared with using ammonia water alone as a complexing agent, the mixed solution containing an organic carboxylic acid has a stronger metal ion chelating ability and can form stable complexes with metal ions (Ni 2+ , Co 2+ , Mn 2+ ). Through the synergistic effect of the organic carboxylic acid and ammonia water, the complexation efficiency is improved, laying a foundation for obtaining a product with uniform phase dispersion in the subsequent preparation.

[0010] (3) Preparation of precipitation solution: After adding battery-grade lithium carbonate or industrial-grade lithium carbonate into water to make a slurry, carbon dioxide is introduced to obtain a lithium bicarbonate solution, and then ammonium bicarbonate is added to obtain solution C. Since lithium carbonate has low solubility in water, it is difficult to disperse it with a solvent, which is why the solid-phase mixing method is basically used to prepare ternary materials using lithium carbonate as the lithium source in the prior art. In this patent, by introducing carbon dioxide into the solution of lithium carbonate, carbon dioxide reacts with water to form carbonic acid, which further promotes the conversion of lithium carbonate into lithium bicarbonate with greater solubility, effectively increasing the lithium content in the solution. The ratio of the amount of substance of lithium element in solution C to the total amount of substance of nickel, cobalt, and manganese metal ions is (1.1 - 1.2):1, that is, there is a certain excess coefficient of lithium. The ratio of the amount of substance of ammonium bicarbonate in solution C to the total amount of substance of nickel, cobalt, and manganese metal ions is (1.5 - 3.0):1. During the reaction process, the system temperature needs to be strictly controlled. Preferably, the temperatures of the lithium bicarbonate solution and solution C are controlled at 25 - 30 °C. If the temperature is too high, the solubility of carbon dioxide will decrease, and lithium bicarbonate is easily decomposed by heat, which will affect the progress of the reaction. If the temperature is too low, it will also affect the solubility of carbon dioxide in water, and then affect the concentration of the obtained lithium bicarbonate solution.

[0011] (4) Pyrolysis precipitation: Mix solution B and solution C into a kettle to obtain a mixed solution D, transfer it into a hydrothermal reaction kettle, and slowly heat it under stirring conditions. The heating rate is not higher than 1 °C / min, and heat it to 60 - 95 °C for hydrothermal reaction for 1 - 6 h. After the reaction is completed, the obtained product is filtered, washed, dried, and crushed, and then the precursor of the nickel-cobalt-manganese ternary cathode material is obtained through screening.

[0012] (5) Preparation of ternary cathode material: The precursor of the nickel-cobalt-manganese ternary cathode material is further heated to 700 - 950 °C at a heating rate of 3 - 5 °C / min in an oxidizing atmosphere such as air or oxygen, and then calcined and crushed to obtain the ternary cathode material.

[0013] The present invention also provides a nickel-cobalt-manganese ternary cathode material, which is prepared by the preparation method as described above. This nickel-cobalt-manganese ternary cathode material has good electrochemical performance and has good application prospects in lithium-ion batteries.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The preparation method of the ternary cathode material provided by the present invention is as follows: First, soluble salts of nickel, cobalt, and manganese are dissolved in a solvent, and a mixed solution containing nickel, cobalt, manganese, and lithium ions is obtained under the dual complexation of an organic carboxylic acid and ammonia water; lithium carbonate is converted into lithium bicarbonate and ammonium bicarbonate is used in combination. During the subsequent hydrothermal reaction process, the thermal decomposition of ammonium bicarbonate and lithium bicarbonate is caused by slow heating to release carbonate ions. At this time, the carbonate ions will cause the precipitation of nickel, cobalt, manganese, and lithium to obtain a mixed salt of lithium nickel cobalt manganese carbonate, that is, the precursor of the ternary cathode material; finally, the precursor is calcined at high temperature to obtain the ternary cathode material. During the above reaction process, the thermal decomposition of bicarbonate and the precipitation of metal ions occur simultaneously in the system, and the four metal ions of nickel, cobalt, manganese, and lithium in the solution co-precipitate. Compared with the traditional method of co-precipitation by mixing two solutions, the method provided by this patent will not cause segregation due to inconsistent local solution components. In the precursor prepared by the present invention, the elements of nickel, cobalt, manganese, and lithium are evenly distributed. The nickel cobalt manganese ternary cathode material can be obtained by subjecting this precursor to high-temperature aerobic calcination. In the subsequent calcination process of this precursor with evenly distributed elements, the migration paths of each element are short, which is conducive to the formation of a layered phase and the integrity of the material lattice, thereby improving the electrochemical performance of the material. The preparation method provided by the present invention provides new methods and ideas for technological innovation in the nickel cobalt manganese ternary cathode material industry. Description of the Drawings

[0016] Figure 1 SEM pattern of the nickel cobalt manganese ternary cathode material prepared in Example 1 of the present invention. Detailed Embodiments

[0017] The following further illustrates the present invention with reference to embodiments, so that those skilled in the art can better understand the present invention and implement it, but the embodiments given are not intended to limit the present invention.

[0018] In addition, during the preparation process in the following embodiments, unless otherwise specified, they are all conventional means in the prior art in this field, and therefore will not be described in detail; the raw materials used in the following embodiments are all commercially available products and can be obtained through purchase.

[0019] Example 1

[0020] A preparation method of a nickel cobalt manganese ternary cathode material includes the following steps:

[0021] (1) Preparation of the transition metal solution: Nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved in pure water to obtain solution A. At this time, the solution contains Ni 2+ , Co 2+ , Mn 2+ and SO4 2- , Ni 2+ , Co 2+ , Mn2+ The molar ratio of the substances is 55:10:35, and the total concentration of nickel, cobalt, and manganese metal ions is 1.5 mol / L;

[0022] (2) Solution complexation and pH adjustment: Mix NH₃·H₂O and citric acid in a molar ratio of 1.5:1 to obtain a mixed solution; add this mixed solution to solution A to complex transition metal ions and adjust the pH to 6.5, obtaining solution B;

[0023] (3) Preparation of precipitation solution: Battery-grade lithium carbonate is added to pure water to make a slurry, and then carbon dioxide is introduced to obtain a lithium bicarbonate solution. Control the temperature of the lithium bicarbonate solution at 25 °C. The ratio of the amount of lithium element to the total amount of nickel, cobalt, and manganese metal ion substances is 1.2:1. Then add ammonium bicarbonate, and the ratio of the amount of ammonium bicarbonate to the total amount of nickel, cobalt, and manganese metal ion substances is 2.0:1, obtaining solution C;

[0024] (4) Pyrolysis precipitation: Mix solution B and solution C into a kettle to obtain a mixed solution D. Transfer it into a hydrothermal reaction kettle and slowly heat it under stirring conditions. The heating rate is 0.5 °C / min. Heat it to 70 °C and carry out a hydrothermal reaction for 2 h, and then filter, wash, dry, and crush it. Pass through a 200-mesh sieve to obtain the precursor;

[0025] (5) Preparation of ternary cathode material: Heat the precursor powder in an air atmosphere to 950 °C at a rate of 3 °C / min and calcine for 9 h, and obtain the ternary cathode material after pulverization.

[0026] Figure 1 FIG. 17 is the SEM pattern of the nickel-cobalt-manganese ternary cathode material prepared in Example 1. It can be seen that the obtained single-crystal ternary material is uniformly micron-sized particles microscopically, and the surface of the micron-sized particles is round. This is due to the uniform distribution of nickel, cobalt, manganese, and lithium elements in the basic particles of the prepared precursor. Further, high-temperature aerobic calcination and pulverization of the precursor can obtain the nickel-cobalt-manganese lithium-ion ternary cathode material. The short migration paths of each element of this precursor with uniform element distribution are beneficial to the formation of lamellar phases and the integrity of the material lattice during the subsequent calcination process, thus playing a role in improving the electrochemical performance of the material.

[0027] Example 2

[0028] A preparation method of a nickel-cobalt-manganese ternary cathode material, comprising the following steps:

[0029] (1) Preparation of transition metal solution: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in pure water to obtain solution A. At this time, the solution contains Ni 2+ , Co 2+ , Mn 2+ and SO₄ 2- , Ni2+ ,Co 2+ ,Mn 2+ The molar ratio of the substances is 65:7:28, and the total concentration of nickel, cobalt, and manganese metal ions is 2 mol / L;

[0030] (2) Solution complexation and pH adjustment: NH3·H2O and citric acid are mixed in a molar ratio of 2:1 to obtain a mixed solution; this mixed solution is added to solution A to complex the transition metal ions and adjust the pH to 7, obtaining solution B;

[0031] (3) Preparation of the precipitation solution: Industrial-grade lithium carbonate is added to pure water to make a slurry, and then carbon dioxide is introduced to obtain a lithium bicarbonate solution. The temperature of the lithium bicarbonate solution is controlled at 25 °C. The ratio of the amount of lithium element to the total amount of nickel, cobalt, and manganese metal ions is 1.15:1. Then ammonium bicarbonate is added, and the ratio of the amount of ammonium bicarbonate to the total amount of nickel, cobalt, and manganese metal ions is 2.2:1, obtaining solution C;

[0032] (4) Pyrolysis precipitation: Solution B and solution C are mixed in a kettle to obtain a mixed solution D, which is transferred to a hydrothermal reaction kettle and slowly heated under stirring conditions. The heating rate is 0.6 °C / min, and the temperature is raised to 80 °C for a hydrothermal reaction for 3 h. Then it is filtered, washed, dried, and crushed through a 200-mesh sieve to obtain powder E;

[0033] (5) Preparation of the ternary cathode material: Powder E is further calcined at 900 °C at a heating rate of 4 °C / min in an air atmosphere and then pulverized to obtain the ternary cathode material.

[0034] Example 3

[0035] A method for preparing a nickel-cobalt-manganese ternary cathode material, comprising the following steps:

[0036] (1) Preparation of the transition metal solution: Soluble salts of nickel, cobalt, and manganese, namely nickel chloride, cobalt chloride, and manganese chloride, are dissolved in pure water to obtain solution A. At this time, the solution contains Ni 2+ ,Co 2+ ,Mn 2+ and Cl - etc. The molar ratio of Ni 2+ ,Co 2+ ,Mn 2+ is 88:07:05, and the total concentration of nickel, cobalt, and manganese metal ions is 2.5 mol / L;

[0037] (2) Solution Complexation and pH Adjustment: Mix NH₃·H₂O and citric acid in a molar ratio of 2.5:1 to obtain a mixed solution; add this mixed solution to Solution A to complex transition metal ions and adjust the pH to 7.5, obtaining Solution B;

[0038] (3) Precipitation Solution Preparation: Pulverize battery-grade lithium carbonate with pure water and then introduce carbon dioxide to obtain a lithium bicarbonate solution. Control the temperature of the lithium bicarbonate solution at 25 °C, where the molar ratio of lithium element to the total molar amount of nickel, cobalt, and manganese metal ions is 1.1:1. Then add ammonium bicarbonate, where the molar ratio of ammonium bicarbonate to the total molar amount of nickel, cobalt, and manganese metal ions is 2.5:1, obtaining Solution C;

[0039] (4) Pyrolytic Precipitation: Mix Solution B and Solution C into a kettle to obtain a mixed solution D. Transfer it into a hydrothermal reaction kettle and slowly raise the temperature under stirring conditions at a heating rate of 0.7 °C / min. Raise the temperature to 85 °C and conduct a hydrothermal reaction for 4 h, and then filter, wash, dry, and crush it through a 200-mesh sieve to obtain powder E;

[0040] (5) Preparation of Ternary Cathode Material: Further calcine powder E in an oxygen atmosphere at a heating rate of 5 °C / min to 850 °C and then crush it to obtain the ternary cathode material.

[0041] Performance Test and Results

[0042] Use the ternary cathode materials prepared in Examples 1, 2, and 3 as the cathode materials of the battery, and make them into button cells. The specific preparation method is as follows: Mix the cathode material, carbon-based conductive agent Super P, and polyvinylidene fluoride in a mass ratio of 80:10:10 in N-methylpyrrolidone to make a slurry, coat the slurry on aluminum foil, dry it, and slice it to prepare a working electrode. Among them, the areal density of the composite electrode material is 1 mg / cm 2 ; Test Method: Use a lithium sheet as the reference electrode in a lithium-ion half-cell, and select a mixed solution of ethylene carbonate / dimethyl carbonate (mass ratio 1:1) with 1 M lithium hexafluorophosphate as the electrolyte; conduct battery charge and discharge tests on a Neware battery test system, and select a voltage range of 2.75 - 4.35 V (vs Li + / Li). The results are shown in Table 1. At the same time, purchase conventional method ternary cathode materials (obtained by high-speed mixing of nickel-cobalt-manganese precursor and lithium carbonate and then calcining and crushing) with the same components as those in Examples 1, 2, and 3 in the market and compare them with the ternary cathode materials prepared in the present invention, which are respectively recorded as Comparative Example 1, Comparative Example 2, and Comparative Example 3. The obtained results are as follows in Table 1:

[0043] Table 1

[0044]

[0045] It can be seen that compared with the conventional ternary cathode materials with the same components on the market, the batteries assembled with the materials prepared in the present invention have certain improvements in the electrical performance in terms of the 0.2C and 1C capacities and the first efficiency. The increase in capacity means that the batteries prepared with this material will have a higher energy density. Among them, the increase in the first efficiency (the first efficiency) is more practically significant. The first efficiency reflects the degree of side reactions and the proportion of available lithium ions during the charge and discharge process, and is an important indicator of the material performance. The first efficiency of the batteries composed of the materials prepared in this patent exceeds 88%, and the highest can reach 89.12%, which is very difficult to achieve in the prior art and has a leading level in the industry.

[0046] Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A preparation method of a nickel-cobalt-manganese ternary cathode material, characterized in that: It includes the following steps: Dissolve nickel salt, cobalt salt and manganese salt in a solvent to obtain solution A; Add a mixed solution composed of organic carboxylic acid and ammonia water to solution A to obtain solution B with a pH of 6 - 8; After adding lithium carbonate to water, pass carbon dioxide through to obtain a lithium bicarbonate solution; Then add ammonium bicarbonate to obtain solution C; Mix solution B and solution C and carry out a hydrothermal reaction. The obtained product is separated, dried and crushed to obtain a precursor; After calcining the precursor in an oxygen-containing atmosphere, the nickel cobalt manganese ternary cathode material is obtained; The ratio of the amount of substance of lithium element in solution C to the total amount of substance of nickel, cobalt and manganese metal ions is (1.1 - 1.2):1; the ratio of the amount of substance of ammonium bicarbonate in solution C to the total amount of substance of nickel, cobalt and manganese metal ions is (1.5 - 3.0):

1.

2. The preparation method of the nickel-cobalt-manganese ternary cathode material according to claim 1, wherein: The nickel salt is nickel sulfate or nickel chloride; the cobalt salt is cobalt sulfate or cobalt chloride; the manganese salt is manganese sulfate or manganese chloride.

3. The preparation method of the nickel-cobalt-manganese ternary cathode material according to claim 1, characterized in that: The solvent is water or a mixed solvent composed of water and an alcohol reagent; the alcohol reagent is ethanol or ethylene glycol.

4. The preparation method of the nickel-cobalt-manganese ternary cathode material according to claim 1, characterized in that: The organic carboxylic acid is citric acid or acetic acid.

5. The preparation method of the nickel-cobalt-manganese ternary cathode material according to claim 1, wherein: The temperature of the lithium bicarbonate solution and solution C is 25 - 30 °C.

6. The preparation method of the nickel cobalt manganese ternary cathode material according to claim 1, wherein: The temperature of the hydrothermal reaction is 60 - 95 °C and the time is 1 - 6 h.

7. The preparation method of the nickel-cobalt-manganese ternary cathode material according to claim 1, wherein: The temperature of the calcination is 700 - 950 °C.

8. A nickel-cobalt-manganese ternary cathode material, characterized in that: The nickel cobalt manganese ternary cathode material is prepared by using the preparation method described in any one of claims 1 to 7.

9. A lithium-ion battery, characterized in that: The lithium ion battery contains the nickel cobalt manganese ternary cathode material described in claim 8.

Images