A ternary positive electrode material and preparation method thereof

Abstract

The present invention discloses a ternary positive electrode material and a preparation method thereof. The preparation method comprises the following steps: S1, preparing an aqueous solution of a water-soluble metal hydrochloride salt a, a mixed salt b and a complexing agent, which are respectively recorded as solution A, solution B and solution C; S2, adding the complexing agent, the ternary precursor and water into a reactor, stirring to obtain a slurry D; S3, while stirring, simultaneously passing solution A, solution B and solution C into the slurry D for surface deposition to obtain a surface-modified ternary precursor; S4, mixing the surface-modified ternary precursor with a lithium salt, and calcining to obtain a ternary positive electrode material. The present invention utilizes metal acid ions and metal ions to undergo precipitation reaction, and through a simple one-step precipitation method, realizes the simultaneous deposition of multiple fast ion conductor precursors on the surface of the ternary precursor; after the fast ion conductor precursor is mixed with lithium and sintered, a multi-component fast ion conductor can be generated, which can significantly reduce the interfacial lithium ion transmission energy barrier of the positive electrode material, thereby improving the material rate performance.

Description

Technical Field

[0001] The present invention relates to a ternary positive electrode material and a preparation method thereof, belonging to the technical field of lithium ion battery positive electrode materials. Background Art

[0002] Ternary lithium-ion batteries are widely used in the automotive industry due to their high energy density. To further increase energy density, ternary cathode materials are gradually becoming higher in nickel. While increasing nickel content can improve the energy density of ternary materials, it also leads to a number of drawbacks, such as reduced material stability and safety, which deteriorates the material's cycle and rate performance. To improve the performance of high-nickel cathode materials, researchers have proposed various methods, including optimizing the synthesis process, doping, and coating.

[0003] Coating is a common and effective modification method. Common coating materials include Al2O3, ZrO2, MgO2 and H2WO4. A small amount of coating with materials such as Al2O3, ZrO2, H2WO4 can react with residual lithium on the surface of the material to generate fast ion conductors, which can improve the rate performance of the material. At the same time, the generated fast ion conductors and oxides can effectively prevent HF corrosion, isolate the electrolyte from the positive electrode reaction, and improve the material's cycle performance. Currently, most coating methods are dry coating, which cannot coat evenly. Based on this, the present invention is proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a ternary positive electrode material. A surface-modified ternary precursor is prepared by a one-step precipitation method, which realizes the simultaneous deposition of multiple fast ion conductor precursors on the surface of the ternary precursor. The polycrystalline positive electrode material obtained by sintering the modified ternary precursor with mixed lithium has excellent rate and cycle performance.

[0005] The method for preparing the ternary cathode material provided by the present invention comprises the following steps:

[0006] S1. Prepare aqueous solutions of water-soluble metal hydrochloride salt a, mixed salt b and complexing agent, which are respectively referred to as solution A, solution B and solution C;

[0007] S2, adding the complexing agent, ternary precursor and water into a reactor, stirring to obtain slurry D;

[0008] S3. Under stirring, the solution A, the solution B, and the solution C are simultaneously introduced into the slurry D for surface deposition to obtain a surface-modified ternary precursor;

[0009] S4. The surface-modified ternary precursor is mixed with lithium salt and calcined to obtain a ternary positive electrode material.

[0010] In the preparation method of the present invention, the metal hydrochloride salt a is MoO4 2-WO4 2- One or more of potassium salts, sodium salts and water-soluble ammonium salts;

[0011] The mixed salt b includes a main component c and a doping and modification component d;

[0012] The main component c includes at least one of aluminum salt and zirconium salt, and the doping modification component d includes at least one of lanthanum salt and yttrium salt;

[0013] The complexing agent is one of potassium salt and sodium salt of citric acid and tartaric acid.

[0014] In the preparation method of the present invention, the aluminum salt, the zirconium salt, the lanthanum salt and the yttrium salt are all sulfates or nitrates of the corresponding metals.

[0015] In the preparation method of the present invention, in the mixed salt b, the ratio of the total metal molar amount contained in the main component c to the total metal molar amount contained in the doping modification component d is 1:0.05-0.1.

[0016] In the preparation method of the present invention, in step S1, the total solute concentration in solution A is 0.1-0.5 mol / L, the total solute concentration in solution B is 0.1-1 mol / L, and the total solute concentration in solution C is 0.5-5 mol / L.

[0017] In the preparation method of the present invention, in step S2, the ternary precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.3≤x<1, 0 <y≤0.3,x+y<1;

[0018] In the slurry D, the concentration of the complexing agent is 0.02 to 0.05 mol / L, and the solid concentration of the ternary precursor is 300 to 600 g / L.

[0019] In the preparation method of the present invention, in step S3, the solution A, the solution B, and the solution C are all introduced into the slurry D through flow pumps, and the flow rates of the solution A and the solution B are controlled so that the metal acid radicals introduced into the slurry D can be completely precipitated by the metal ions in the solution B per unit time; and the flow rate of the solution C is controlled so that the concentration of the complexing agent during the reaction is consistent with the initial concentration of the complexing agent in the slurry D;

[0020] The conditions for the surface deposition are as follows:

[0021] The reaction atmosphere is an inert atmosphere, the reaction temperature is 50-70°C, and the stirring speed is 500-700 r / min;

[0022] The mass ratio of the metal acid salt a to the ternary precursor introduced into the slurry D is 0.005 to 0.01:1, such as 0.005:1 or 0.01:1.

[0023] In the preparation method of the present invention, step S3 further includes washing the surface-modified ternary precursor with deionized water until the alkali metal content of the material is less than 100 ppm, and then drying under the following conditions: temperature of 80-120° C. for 5-12 hours.

[0024] In the preparation method of the present invention, in step S4, the lithium salt is one of lithium carbonate and lithium hydroxide;

[0025] The molar ratio of lithium element in the lithium salt to total metal ions in the surface-modified ternary precursor is 1:1.03-1.05;

[0026] The calcination temperature is 800-850° C., the calcination time is 10-20 hours, and the sintering atmosphere is air atmosphere or oxygen atmosphere.

[0027] The ternary positive electrode material prepared by the method of the present invention also falls within the protection scope of the present invention.

[0028] The present invention utilizes metal acid radical ions and metal ions to carry out precipitation reaction, and through a simple one-step precipitation method, realizes the simultaneous deposition of multiple fast ion conductor precursors (such as aluminum tungstate, zirconium tungstate, zirconium molybdate, etc.) on the surface of a ternary precursor; after the fast ion conductor precursor is mixed with lithium and sintered, a multi-component fast ion conductor (such as lithium tungstate, lithium molybdate, lithium aluminate, lithium zirconate, etc.) can be generated, which can significantly reduce the interfacial lithium ion transmission energy barrier of the positive electrode material, thereby improving the material rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the SEM image of the unmodified ternary precursor.

[0030] Figure 2 This is the SEM image of the surface-modified ternary precursor obtained in step (4) of Example 5 of the present invention. DETAILED DESCRIPTION

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0033] Example 1

[0034] (1) Sodium tungstate, a mixed salt of aluminum sulfate and lanthanum nitrate, and sodium citrate were added to deionized water and dissolved to obtain solutions A, B, and C with molar concentrations of 0.1 mol / L, 0.1 mol / L (total molar concentration of aluminum sulfate and lanthanum nitrate), and 0.5 mol / L, respectively; the molar concentration ratio of aluminum sulfate to lanthanum nitrate in solution B was 1:0.05;

[0035] (2) Sodium citrate, Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and deionized water were added to the reactor and stirred to obtain a sodium citrate molar concentration of 0.02 mol / L and Ni 0.8 Co 0.1 Mn 0.1 Slurry D with a (OH)2 solid content of 300 g / L;

[0036] (3) Under nitrogen atmosphere, rotation speed of 500r / min, reaction temperature of 50℃, solution A, solution B and solution C are simultaneously introduced into slurry D for surface deposition reaction. By controlling the flow rate of solution A and B, the metal acid radicals introduced into slurry D can be completely precipitated by the metal ions in solution B according to the stoichiometric ratio per unit time; by controlling the flow rate of solution C, the concentration of the complexing agent is kept at 0.02mol / L during the reaction process; when the mass of sodium tungstate introduced reaches Ni 0.8 Co 0.1 Mn 0.1 When the mass of (OH)2 reaches 0.5%, the feed is stopped and the reaction ends.

[0037] (4) The obtained slurry was filtered, washed with deionized water, and dried at 80°C for 12 h to obtain a surface-modified ternary precursor. The sodium ion content of the precursor was measured to be 93 ppm;

[0038] (5) The surface-modified ternary precursor is mixed with lithium carbonate salt and calcined at 800°C for 10 h in an air atmosphere to obtain a ternary positive electrode material, wherein the molar ratio of lithium element to the total metal elements (nickel, cobalt, manganese, tungsten, lanthanum, aluminum) in the modified ternary precursor is 1:1.03.

[0039] Example 2

[0040] (1) adding metal acid salts potassium molybdate, zirconium sulfate and yttrium nitrate mixed salt and potassium tartrate to deionized water respectively and dissolving them to obtain solutions A, B and C with molar concentrations of 0.5 mol / L, 1 mol / L (total molar concentration of zirconium sulfate and yttrium nitrate) and 5 mol / L respectively; wherein the molar concentration ratio of zirconium sulfate to yttrium nitrate in solution B is 1:0.1;

[0041] (2) Potassium tartrate, Ni 0.8 Co 0.1Mn 0.1 (OH)2 and deionized water were added to the reactor and stirred to obtain a potassium tartrate molar concentration of 0.05 mol / L, Ni 0.8 Co 0.1 Mn 0.1 Slurry D with a (OH)2 solid content of 600 g / L;

[0042] (3) In a nitrogen atmosphere, at a speed of 700 r / min and a reaction temperature of 70°C, solution A, solution B and solution C are simultaneously introduced into slurry D for surface deposition reaction. By controlling the flow rates of solutions A and B, the metal acid radicals introduced into slurry D can be completely precipitated by the metal ions in solution B according to the stoichiometric ratio per unit time. By controlling the flow rate of solution C, the concentration of the complexing agent is maintained at 0.05 mol / L during the reaction. When the mass of sodium tungstate introduced reaches Ni 0.8 Co 0.1 Mn 0.1 When the mass of (OH)2 reaches 1%, the feed is stopped and the reaction is finished.

[0043] (4) The obtained slurry was filtered, washed with deionized water, and dried at 120°C for 5 h to obtain a surface-modified ternary precursor. The potassium ion content of the precursor was measured to be 87 ppm;

[0044] (5) The surface-modified ternary precursor is mixed with lithium hydroxide and calcined at 850°C for 10 h in an oxygen atmosphere to obtain a ternary positive electrode material, wherein the molar ratio of lithium element to the total metal elements (nickel, cobalt, manganese, tungsten, yttrium, zirconium) in the modified ternary precursor is 1:1.05.

[0045] Example 3

[0046] (1) Sodium tungstate, a mixed salt of aluminum nitrate and lanthanum nitrate, and potassium tartrate were added to deionized water and dissolved to obtain solutions A, B, and C with molar concentrations of 0.5 mol / L, 0.2 mol / L (total molar concentration of aluminum nitrate and lanthanum nitrate), and 5 mol / L, respectively; the molar concentration ratio of aluminum nitrate to lanthanum nitrate in solution B was 1:0.08;

[0047] (2) Sodium tartrate, Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and deionized water were added to the reactor and stirred to obtain a sodium potassium tartrate molar concentration of 0.03 mol / L, Ni 0.8 Co 0.1 Mn 0.1 Slurry D with a (OH)2 solid content of 600 g / L;

[0048] (3) In nitrogen atmosphere, at a speed of 700 r / min and a reaction temperature of 70°C, solution A, solution B and solution C are simultaneously introduced into slurry D for surface deposition reaction. By controlling the flow rates of solution A and B, the metal acid radicals introduced into slurry D can be completely precipitated by the metal ions in solution B according to the stoichiometric ratio per unit time. By controlling the flow rate of solution C, the concentration of the complexing agent is maintained at 0.03 mol / L during the reaction. When the mass of sodium tungstate introduced reaches Ni 0.8 Co 0.1 Mn 0.1 When the mass of (OH)2 reaches 1%, the feed is stopped and the reaction is finished.

[0049] (4) The obtained slurry was filtered, washed with deionized water, and dried at 120°C for 5 h to obtain a surface-modified ternary precursor. The sodium ion content of the precursor was measured to be 95 ppm;

[0050] (5) The surface-modified ternary precursor is mixed with lithium carbonate and calcined at 830°C for 15 h in an oxygen atmosphere to obtain a ternary positive electrode material, wherein the molar ratio of lithium element to the total metal elements (nickel, cobalt, manganese, tungsten, lanthanum, and aluminum) in the modified ternary precursor is 1:1.04.

[0051] Example 4

[0052] The difference between Example 4 and Example 3 is that in step (2), Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 solid content is 500g / L.

[0053] Example 5

[0054] The difference between Example 5 and Example 4 is that in step (3), the mass of sodium tungstate introduced is Ni 0.8 Co 0.1 Mn 0.1 0.8% by mass of (OH)2.

[0055] from Figure 1 、 Figure 2 It can be seen that after co-precipitation modification, there is obviously an additional layer of covering on the surface of the particles, indicating that the co-precipitation product is successfully deposited on the surface of the particles.

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 5 is that there is no doped modified component, the aluminum nitrate and lanthanum nitrate mixed salt is replaced by single aluminum nitrate, and the other parameters and steps remain unchanged;

[0058] Comparative Example 2

[0059] Directly unmodified Ni 0.8 Co0.1 Mn 0.1 (OH)2 was mixed with lithium carbonate and calcined at 830°C for 15h in an oxygen atmosphere to obtain a ternary positive electrode material, in which the molar ratio of lithium element to the total metal elements (nickel, cobalt, manganese) in the modified ternary precursor was 1:1.04.

[0060] Comparative Example 3

[0061] The difference between Comparative Example 3 and Example 5 is that in step (1), the molar concentration ratio of aluminum nitrate to lanthanum nitrate in solution B is 1:0.01.

[0062] Comparative Example 4

[0063] The difference between Comparative Example 4 and Example 5 is that in step (1), the molar concentration ratio of aluminum nitrate to lanthanum nitrate in solution B is 1:0.15.

[0064] Electrochemical performance characterization: The cathode materials before and after modification were made into button batteries, in which the active material: conductive agent: binder = 90:5:5 (mass ratio), the conductive agent was Super P, the binder was PVDF, and the electrolyte was 1M LiPF6 dissolved in a mixed solvent of EC, DEC and DMC (volume ratio of 1:1:1). The test voltage range was 2.8-4.25V; the first cycle of charge and discharge was tested at 0.1C / 0.1C, and the cycle retention was measured at 1C / 1C charge and discharge conditions.

[0065] Table 1 Electrical performance data of samples in each example

[0066]

[0067] From the charge and discharge capacity data of Examples 1-5 and Comparative Example 1, it can be seen that the surface modification of the precursor has little effect on the charge and discharge capacity of the positive electrode material under 0.1C conditions, but has a greater impact on the discharge capacity of the material under high rate conditions, significantly improving the capacity of the material under 1C and 2C discharge rates. This is because the coating layer deposited on the surface of the precursor can generate a multi-component fast ion conductor (such as tungsten / lithium aluminate, molybdenum / lithium zirconium, etc.) after mixed lithium sintering, which can significantly reduce the interfacial lithium ion transmission energy barrier of the positive electrode material, thereby improving the material rate performance. At the same time, the surface fast ion conductor component weakens the reaction between the positive electrode material and the electrolyte, and also improves the cycle performance of the material.

[0068] From the data of Example 5 and Comparative Example 2, it can be seen that the doping modification component plays an important role in improving the rate performance of the material, and can further improve the rate performance of the positive electrode material. At the same time, the presence or absence of the doping component has little effect on the cycling performance of the material.

[0069] From the data of Comparative Examples 3, 4, Example 5, 2 and 1, it can be seen that coating can significantly improve the cycle performance of the material, but when the content of the doped modified component in the coating layer is too much or too little, the improvement of the rate performance of the material by the coating layer will be significantly weakened.

Claims

1. A method for preparing a ternary cathode material, comprising the following steps: S1. Prepare aqueous solutions of water-soluble metal hydrochloride salt a, mixed salt b and complexing agent, which are respectively referred to as solution A, solution B and solution C; The metal hydrochloride salt a is MoO4 2- WO4 2- One or more of potassium salts, sodium salts and water-soluble ammonium salts; The mixed salt b includes a main component c and a doping and modification component d; In the mixed salt b, the ratio of the total metal molar amount contained in the main component c to the total metal molar amount contained in the doping and modification component d is 1:0.05-0.1; The main component c includes at least one of aluminum salt and zirconium salt, and the doping modification component d includes at least one of lanthanum salt and yttrium salt; S2, adding the complexing agent, ternary precursor and water into a reactor, stirring to obtain slurry D; The complexing agent is one of the potassium salt and sodium salt of citric acid and tartaric acid; S3. Under stirring, the solution A, the solution B, and the solution C are simultaneously introduced into the slurry D for surface deposition to obtain a surface-modified ternary precursor; S4. The surface-modified ternary precursor is mixed with lithium salt and calcined to obtain a ternary positive electrode material.

2. The preparation method according to claim 1, wherein: The aluminum salt, the zirconium salt, the lanthanum salt and the yttrium salt are all sulfates or nitrates of corresponding metals.

3. The preparation method according to claim 1 or 2, characterized in that: In step S1, the total solute concentration in the solution A is 0.1-0.5 mol / L, the total solute concentration in the solution B is 0.1-1 mol / L, and the total solute concentration in the solution C is 0.5-5 mol / L.

4. The preparation method according to claim 1 or 2, characterized in that: In step S2, the ternary precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.3≤x<1, 0 <y≤0.3,x+y<1; In the slurry D, the concentration of the complexing agent is 0.02 to 0.05 mol / L, and the solid concentration of the ternary precursor is 300 to 600 g / L.

5. The preparation method according to claim 1 or 2, characterized in that: In step S3, the solution A, the solution B, and the solution C are all introduced into the slurry D through flow pumps. The flow rates of the solution A and the solution B are controlled so that the metal acid radicals introduced into the slurry D can be completely precipitated by the metal ions in the solution B per unit time. The flow rate of the solution C is controlled so that the concentration of the complexing agent during the reaction is consistent with the initial concentration of the complexing agent in the slurry D. The conditions for the surface deposition are as follows: The reaction atmosphere is an inert atmosphere, the reaction temperature is 50-70° C.; the stirring speed is 500-700 r / min; and the mass ratio of the metal acid salt a to the ternary precursor introduced into the slurry D is 0.005-0.01:

1.

6. The preparation method according to claim 1 or 2, characterized in that: Step S3 also includes the step of washing the surface-modified ternary precursor with deionized water until the alkali metal content of the material is less than 100 ppm, and then drying it under the following conditions: temperature of 80-120° C. for 5-12 hours.

7. The preparation method according to claim 1 or 2, characterized in that: In step S4, the lithium salt is one of lithium carbonate and lithium hydroxide; The molar ratio of lithium element in the lithium salt to total metal ions in the surface-modified ternary precursor is 1:1.03-1.05; The calcination temperature is 800-850° C., the calcination time is 10-20 hours, and the sintering atmosphere is air atmosphere or oxygen atmosphere.

8. A ternary positive electrode material prepared by the method according to any one of claims 1 to 7.

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