Ternary positive electrode material, and preparation method therefor and use thereof

Abstract

The present disclosure provides a ternary positive electrode material, and a preparation method therefor and a use thereof. The preparation method comprises the following steps: (1) mixing a nickel source, a cobalt source and a solvent, freezing to obtain a frozen solution A, mixing an aluminum source, a complexing agent and a solvent, freezing to obtain a frozen solution B, crushing the frozen solution A and the frozen solution B at a low temperature, pressing, and freezing to obtain a frozen solution C; (2) placing the frozen solution C in a backflow device, controlling an alkaline backflow liquid to flow back between the backflow device and a reaction device until the frozen liquid C is completely melted to obtain a suspension; and (3) carrying out solid-liquid separation on the suspension, mixing the obtained solid product with a lithium source, and sintering to obtain a ternary positive electrode material. According to the present disclosure, a simple backflow melting operation is used, the proportion of elements of the material can be guaranteed by means of a simple operation, uniform coprecipitation of nickel, cobalt and aluminum is achieved, and an ammonia complexing agent does not need to be used in the method, such that the environmental pollution is reduced, the distribution of the elements of the prepared ternary positive electrode material is uniform, and the lattice order degree is high.

Description

A ternary positive electrode material and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries and relates to a ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are now widely used in various energy storage applications, such as mobile phones, laptops, and new energy vehicles. The representative material, lithium nickel cobalt oxide (LNO3), has good energy density, but suffers from drawbacks such as poor overcharge resistance and thermal stability. To address these issues, domestic and international researchers have conducted extensive experiments, demonstrating that aluminum ion doping can stabilize the material structure, increase the lithium ion diffusion coefficient, and significantly inhibit the material's thermochemical reactions.

[0003] However, there are major problems in the preparation of nickel-cobalt-aluminum hydroxide precursors, making it difficult to mass-produce. This is because the solubility constant of aluminum hydroxide is about 10 -33 The solubility product of nickel and cobalt is 10 -15 This makes the precipitation rate of aluminum ions much greater than that of nickel and cobalt ions. It is difficult for aluminum ions to co-precipitate with nickel and cobalt ions into spherical particles. Therefore, the positive electrode material particles obtained by calcining the precursor doped with aluminum are loose and have poor structural stability.

[0004] CN104425815A uses two or more mixed complexing agents to pre-complex an aluminum salt solution, and then adds the aluminum complex solution, nickel-cobalt-containing solution and precipitant to a reactor at a certain flow rate for reaction. The method of pre-obtaining the aluminum complex solution improves the problem that aluminum ions form Al(OH)3 in aqueous solution significantly faster than nickel-cobalt ions, thereby obtaining a precursor material with uniformly dispersed elements.

[0005] CN115215388A discloses a preparation method of a ternary positive electrode material and a ternary positive electrode material, the method comprising: mixing a manganese salt and / or an aluminum salt with a nickel salt and a cobalt salt, and performing a coprecipitation reaction with an alkaline substance and a complexing agent in a solvent to obtain a coprecipitation slurry having a target median particle size; washing the coprecipitation slurry to obtain a ternary precursor slurry; mixing a lithium source with the ternary precursor slurry in an inert atmosphere to obtain a first mixture; drying the first mixture to obtain a second mixture; and performing a high-temperature sintering treatment on the second mixture to obtain the ternary positive electrode material.

[0006] Complexing agents that can complex with aluminum can usually complex with nickel and cobalt. When the aluminum complex solution and the nickel and cobalt solution are added to the reactor in the above scheme, the excess complexing agent in the aluminum complex solution will complex with the unprecipitated nickel and cobalt, reducing the precipitation rate of nickel and cobalt, increasing the difference in the precipitation rate of nickel and cobalt and aluminum, and is not conducive to the mixing of nickel, cobalt and aluminum elements at the atomic level.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of the present disclosure is to provide a ternary positive electrode material and its preparation method and application. The present disclosure adopts a simple reflux melting operation, which can ensure the element ratio of the material through simple operation and achieve uniform co-precipitation of nickel, cobalt and aluminum. The method does not require the use of an ammonia complexing agent, reduces environmental pollution, and obtains a ternary positive electrode material with uniform element distribution and high lattice order.

[0010] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a method for preparing a ternary cathode material, the preparation method comprising the following steps:

[0012] (1) A nickel source, a cobalt source, and a solvent are mixed and frozen to obtain a frozen liquid A; an aluminum source, a complexing agent, and a solvent are mixed and the pH is adjusted and then frozen to obtain a frozen liquid B; and the frozen liquids A and B are crushed at low temperature, pressed, and frozen to obtain a frozen liquid C;

[0013] (2) placing the frozen liquid C in a reflux device, controlling the alkaline reflux liquid to reflux between the reflux device and the reaction device, and controlling the temperature and pH in the system until the frozen liquid C is completely melted to obtain a suspension;

[0014] (3) performing solid-liquid separation on the suspension, mixing the obtained solid product with a lithium source, and sintering to obtain the ternary positive electrode material.

[0015] The present invention discloses a method of preparing a Ni / Co mixed solution and a frozen Al 3+ The complexing agent mixed solution is placed in a reflux chamber, and the alkaline solution refluxes and melts, so that the aluminum precipitation reaction proceeds slowly. During this reaction, the alkaline solution and the nickel and cobalt ions precipitate, and the complexing agent only acts on the aluminum ions, thereby avoiding the use of the complexing agent to reduce the precipitation rate of the nickel and cobalt ions.

[0016] In one embodiment, the nickel source in step (1) includes any one of nickel sulfate, nickel nitrate, nickel chloride or nickel acetate, or a combination of at least two thereof.

[0017] In one embodiment, the cobalt source includes any one of cobalt sulfate, cobalt nitrate, cobalt chloride or cobalt acetate, or a combination of at least two thereof.

[0018] In one embodiment, the concentration of the nickel source in the freezing solution A is 0.1 to 1 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L.

[0019] In one embodiment, the concentration of the cobalt source in the freezing solution A is 0.1 to 1 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L.

[0020] In one embodiment, the total concentration of the cobalt source and the nickel source in the freezing solution A is 0.5 to 2 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0021] In one embodiment, the aluminum source in step (1) includes any one of aluminum nitrate, aluminum sulfate, or aluminum chloride, or a combination of at least two thereof.

[0022] In one embodiment, the complexing agent includes any one of acetylacetone, oxalic acid, salicylic acid, or sulfosalicylic acid, or a combination of at least two thereof.

[0023] In one embodiment, the pH adjusting agent includes sulfuric acid and / or hydrochloric acid.

[0024] In one embodiment, the pH is 2 to 5, for example, 2, 2.5, 3, 4 or 5.

[0025] In one embodiment, the concentration of the aluminum source in the freezing solution B is 0.1 to 1 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L.

[0026] In one embodiment, the concentration of the complexing agent in the freezing solution B is 0.1 to 0.5 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L.

[0027] In one embodiment, the freezing temperature in step (1) is -30 to -50°C, for example, -30°C, -35°C, -40°C, -45°C or -50°C.

[0028] In one embodiment, the freezing time is 6 to 12 hours, for example, 6 hours, 7 hours, 8 hours, 10 hours or 12 hours.

[0029] In one embodiment, the temperature of the low temperature crushing treatment is <-10°C.

[0030] In one embodiment, the pressing pressure is 0.1-10 MPa, for example, 0.1 MPa, 0.5 MPa, 1 MPa, 5 MPa or 10 MPa.

[0031] In one embodiment, the molar ratio of nickel, cobalt and aluminum in the freezing liquid C is (0.6-0.9):(0.08-0.3):(0.02-0.1), for example: 0.6:0.08:0.02, 0.7:0.1:0.05, 0.8:0.2:0.08, 0.8:0.25:0.05 or 0.9:0.3:0.1, etc.

[0032] In one embodiment, the alkaline reflux solution in step (2) comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0033] In one embodiment, the pH of the alkaline reflux solution is 10.5-12, for example, 10.5, 11, 11.5, 11.8 or 12.

[0034] In one embodiment, the reflux rate of the alkaline reflux solution is 10 to 200 mL / min, for example, 10 mL / min, 20 mL / min, 50 mL / min, 100 mL / min or 200 mL / min.

[0035] In one embodiment, the method of controlling the pH in the system in step (2) includes adding alkali solution.

[0036] In one embodiment, the pH is 10.5 to 12, for example, 10.5, 11, 11.5, 11.8 or 12.

[0037] In one embodiment, the concentration of the alkali solution is 5 to 10 mol / L, for example, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L or 10 mol / L.

[0038] In one embodiment, the temperature in the system is 40-70°C, for example, 40°C, 50°C, 60°C, 65°C or 70°C.

[0039] In one embodiment, the frozen liquid C is completely melted and then aged.

[0040] In one embodiment, the aging treatment time is 2 to 20 hours, for example, 2 hours, 5 hours, 10 hours, 15 hours or 20 hours.

[0041] In one embodiment, the lithium source in step (3) includes lithium hydroxide and / or lithium carbonate.

[0042] In one embodiment, the total molar ratio of the lithium element in the lithium source to the metal element in the solid product is (1-1.1):1, for example: 1:1, 1.02:1, 1.05:1, 1.08:1 or 1.1:1, etc.

[0043] In one embodiment, the sintering includes one-stage sintering and two-stage sintering.

[0044] In one embodiment, the temperature of the first stage sintering is 300-650°C, for example, 300°C, 350°C, 400°C, 500°C or 650°C.

[0045] In one embodiment, the sintering time is 2 to 10 hours, for example, 2 hours, 5 hours, 6 hours, 8 hours or 10 hours.

[0046] In one embodiment, the temperature of the second stage sintering is 700-850°C, for example, 700°C, 750°C, 780°C, 800°C or 850°C.

[0047] In one embodiment, the second-stage sintering time is 8 to 20 hours, for example, 8 hours, 9 hours, 10 hours, 15 hours or 20 hours.

[0048] In a second aspect, the present disclosure provides a ternary positive electrode material, which is prepared by the method described in the first aspect.

[0049] The three transition metal elements in the ternary positive electrode material disclosed herein are evenly distributed in the spherical particles, which improves the lattice order of the material. The lithium nickel cobalt aluminum oxide positive electrode material has a high tap density and has good electrochemical properties such as discharge specific capacity and cycle stability.

[0050] In a third aspect, the present disclosure provides a positive electrode plate, which comprises the ternary positive electrode material as described in the second aspect.

[0051] In a fourth aspect, the present disclosure provides a lithium-ion battery, comprising the positive electrode sheet as described in the third aspect.

[0052] Compared with the prior art, the present disclosure has the following beneficial effects:

[0053] (1) The present invention is to freeze Ni / Co mixed solution and freeze Al 3+The complexing agent mixed solution is placed in a reflux chamber, where the alkaline solution refluxes and melts, causing the aluminum precipitation reaction to proceed slowly. During this reaction, the alkaline solution and nickel and cobalt ions precipitate, while the complexing agent acts only on the aluminum ions. This prevents the use of the complexing agent from reducing the precipitation rate of nickel and cobalt ions. The three transition metal elements in the resulting ternary positive electrode material are evenly distributed within the spherical particles, improving the material's lattice order. The nickel cobalt aluminum oxide lithium positive electrode material has a high tap density and exhibits excellent electrochemical properties such as discharge specific capacity and cycle stability.

[0054] (2) The preparation method disclosed in this disclosure is applicable to various ternary cathode materials, such as LiNi 0.8 Co 0.1 Mn 0.1 The first discharge capacity of the O2 cathode material can reach more than 203mAh / g, and the LiNi 0.75 Co 0.2 Mn 0.05 The first discharge capacity of the O2 cathode material can reach more than 190mAh / g, and the LiNi 0.6 Co 0.3 Mn 0.1 The initial discharge capacity of the O2 positive electrode material can reach over 180 mAh / g, and the cycle retention rate can reach over 96.8% after 100 cycles.

[0055] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0057] Figure 1 is a schematic diagram of the device used in the preparation method of the ternary positive electrode material according to an embodiment of the present disclosure, 1-freezing liquid C, 2-reflux device, 3-pump, 4-reaction device, 5-stirring rod, 6-alkaline reflux liquid, 7-feeding port.

[0058] FIG2 is an EDS graph of the ternary positive electrode material prepared in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0059] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0060] Example 1

[0061] This embodiment provides a ternary cathode material. A schematic diagram of an apparatus used in a method for preparing the ternary cathode material is shown in FIG1 , wherein 1 is a freezing liquid C, 2 is a reflux device, 3 is a pump, 4 is a reaction device, 5 is a stirring rod, 6 is an alkaline reflux liquid, and 7 is a feeding port. The preparation method comprises the following steps:

[0062] (1) Nickel sulfate, cobalt sulfate and deionized water are mixed and frozen in a spherical mold at -35°C for 8 hours to obtain a frozen liquid A with a nickel concentration of 0.8 mol / L, a cobalt concentration of 0.1 mol / L and a total metal concentration of 0.9 mol / L. Aluminum sulfate and acetylacetone are dissolved in deionized water and frozen at -35°C for 8 hours to obtain a frozen liquid B with an aluminum ion concentration of 1 mol / L and an acetylacetone concentration of 0.2 mol / L. The frozen liquids A and B are crushed at below -10°C, and then the shaved (particle size <2 mm) frozen liquids A and B are mixed evenly and pressed into a square or circular mold at a pressure of 2 MPa, and then frozen at -40°C for 6 hours to obtain a frozen liquid C. The ratio of nickel, cobalt and aluminum in the frozen liquid C is 0.8:0.1:0.1;

[0063] (2) A sodium hydroxide solution with a pH of 11 was used as the reflux liquid, and the reflux liquid was controlled to reflux at a rate of 40 mL / min between the reflux device and the reaction device. A sodium hydroxide solution with a concentration of 6 mol / L was added to the feed port to control the pH in the system to 11. After the reaction was carried out at 50°C until the frozen liquid C was completely melted, the mixed solution in the reactor was heated to 60°C as a whole, kept warm and aged for 10 hours to obtain a suspension;

[0064] (3) Separating the suspension, washing the precipitate with deionized water three times, and then drying at 80° C. to obtain nickel cobalt aluminum hydroxide, grinding the nickel cobalt aluminum hydroxide and lithium hydroxide (Li / M=1.02) in ethanol using a ball mill, and calcining in two stages under an oxygen atmosphere, the first stage temperature is 450° C., calcining for 6 hours, and the second stage temperature is 800° C., calcining for 15 hours, to obtain the ternary positive electrode material. The EDS graph of the ternary positive electrode material is shown in FIG2 , as can be seen from FIG2 , the three transition metal elements in the ternary positive electrode material prepared by the method disclosed in the present invention are uniformly distributed.

[0065] Example 2

[0066] This embodiment provides a ternary positive electrode material. A schematic diagram of an apparatus used in a method for preparing the ternary positive electrode material is shown in FIG1 . The preparation method includes the following steps:

[0067] (1) Nickel sulfate, cobalt sulfate and deionized water are mixed and frozen in a spherical mold at -30°C for 12 hours to obtain a frozen liquid A with a nickel concentration of 0.75 mol / L, a cobalt concentration of 0.2 mol / L and a total metal concentration of 0.95 mol / L. Aluminum sulfate and acetylacetone are dissolved in deionized water and frozen at -30°C for 12 hours to obtain a frozen liquid B with an aluminum ion concentration of 0.5 mol / L and an acetylacetone concentration of 0.1 mol / L. The frozen liquids A and B are crushed below -10°C, and then the shaved (particle size <2 mm) frozen liquids A and B are mixed evenly and pressed into a square or circular mold at a pressure of 2 MPa, and then frozen at -30°C for 12 hours to obtain a frozen liquid C. The ratio of nickel element, cobalt element and aluminum element in the frozen liquid C is 0.75:0.2:0.05;

[0068] (2) A sodium hydroxide solution with a pH of 10.5 was used as the reflux liquid. The reflux liquid was controlled to reflux at a rate of 10 mL / min between the reflux device and the reaction device. A sodium hydroxide solution with a concentration of 5 mol / L was added to the feed port to control the pH in the system to 10.5. After the reaction was carried out at 50°C until the frozen solution C was completely melted, the mixed solution in the reactor was heated to 70°C as a whole and kept warm for 2 hours to obtain a suspension;

[0069] (3) Separating the suspension, washing the precipitate with deionized water three times, and then drying it at 80°C to obtain nickel cobalt aluminum hydroxide, grinding the nickel cobalt aluminum hydroxide and lithium hydroxide (Li / M=1.02) in ethanol using a ball mill, and calcining them in two stages under an oxygen atmosphere, the first stage temperature being 300°C for 10 hours, and the second stage temperature being 750°C for 20 hours, to obtain the ternary positive electrode material.

[0070] Example 3

[0071] This embodiment provides a ternary positive electrode material. A schematic diagram of an apparatus used in a method for preparing the ternary positive electrode material is shown in FIG1 . The preparation method includes the following steps:

[0072] (1) nickel sulfate, cobalt sulfate and deionized water are mixed and frozen in a spherical mold at -50°C for 5 hours to obtain a frozen liquid A with a nickel concentration of 0.6 mol / L, a cobalt concentration of 0.3 mol / L and a total metal concentration of 0.9 mol / L; aluminum sulfate and acetylacetone are dissolved in deionized water and frozen at -50°C for 5 hours to obtain a frozen liquid B with an aluminum ion concentration of 1 mol / L and an acetylacetone concentration of 0.2 mol / L; the frozen liquids A and B are crushed at below -10°C; then the shaved (particle size <2 mm) frozen liquids A and B are mixed evenly and pressed into a square or circular mold at a pressure of 2 MPa; and then frozen at -30°C for 12 hours to obtain a frozen liquid C. The ratio of nickel, cobalt and aluminum in the frozen liquid C is 0.6:0.3:0.1;

[0073] (2) A sodium hydroxide solution with a pH of 12 was used as the reflux liquid, and the reflux liquid was controlled to reflux at a rate of 200 mL / min between the reflux device and the reaction device. A sodium hydroxide solution with a concentration of 10 mol / L was added to the feed port to control the pH in the system to 12. After the reaction was carried out at 70°C until the frozen liquid C was completely melted, the mixed solution in the reactor was kept warm and aged for 2 hours to obtain a suspension;

[0074] (3) Separating the suspension, washing the precipitate with deionized water three times, and then drying it at 80°C to obtain nickel cobalt aluminum hydroxide, grinding the nickel cobalt aluminum hydroxide and lithium hydroxide (Li / M=1.02) in ethanol using a ball mill, and calcining them in two stages under an oxygen atmosphere, the first stage temperature being 650°C for 2 hours, and the second stage temperature being 850°C for 8 hours, to obtain the ternary positive electrode material.

[0075] Example 4

[0076] The only difference between this embodiment and embodiment 1 is that the concentration of the complexing agent in the freezing liquid B in step (1) is 0.05 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0077] Example 5

[0078] The only difference between this embodiment and embodiment 1 is that the concentration of the complexing agent in the freezing liquid B in step (1) is 0.8 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0079] Example 6

[0080] The only difference between this embodiment and embodiment 1 is that the reaction temperature of step (2) is 30° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0081] Example 7

[0082] The only difference between this embodiment and embodiment 1 is that the reaction temperature of step (2) is 80° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0083] Comparative Example 1

[0084] This comparative example provides a ternary positive electrode material, and the preparation method of the ternary positive electrode material is as follows:

[0085] (1) nickel sulfate and cobalt sulfate were prepared into 2 mol / L solutions, and a 6 mol / L sodium hydroxide solution was prepared. Acetylacetone was added to a 0.2 mol / L aluminum sulfate solution to obtain a 0.2 mol / L acetylacetone concentration. Nickel sulfate and cobalt sulfate were mixed in a volume ratio of 8:1 to obtain a nickel-cobalt mixed solution;

[0086] (2) mixing the aluminum sulfate mixed solution, the nickel-cobalt mixed solution, and the sodium hydroxide solution at flow rates of 0.2 L / h and 0.1 L / h, while simultaneously opening the sodium hydroxide solution and adjusting the flow rate of the sodium hydroxide solution so that the pH of the reactor system is 11. After the solution fills the reactor to 60%, the feed is stopped, and the temperature is controlled at 60° C. for 10 hours to obtain a suspension;

[0087] (3) The suspension was separated, and the precipitate was washed three times with deionized water and then dried at 80°C to obtain nickel-cobalt-aluminum hydroxide. The nickel-cobalt-aluminum hydroxide and lithium hydroxide were ground in ethanol using a ball mill and calcined in two stages under an oxygen atmosphere, the first stage at 450°C for 6 hours and the second stage at 800°C for 15 hours to obtain a ternary cathode material.

[0088] Performance testing:

[0089] The ternary cathode materials prepared in the examples and comparative examples were made into 2032 button batteries and performance tests were performed at a current density of 0.1C and 3.0-4.3V. The test results are shown in Table 1:

[0090] Table 1

[0091] As can be seen from Table 1, from Examples 1-3, the preparation method disclosed in this disclosure is applicable to various ternary positive electrode materials, and LiNi 0.8 Co 0.1 Mn 0.1 The first discharge capacity of the O2 cathode material can reach more than 203mAh / g, and the LiNi 0.75 Co 0.2 Mn 0.05 The first discharge capacity of the O2 cathode material can reach more than 190mAh / g, and the LiNi 0.6 Co 0.3 Mn 0.1The initial discharge capacity of the O2 positive electrode material can reach over 180 mAh / g, and the cycle retention rate can reach over 96.8% after 100 cycles.

[0092] A comparison of Example 1 and Examples 4-5 shows that during the preparation of the ternary cathode material disclosed herein, the concentration of the complexing agent in the frozen solution B affects its performance. Controlling the concentration of the complexing agent in the frozen solution B to 0.1 to 0.5 mol / L results in a cathode material with better performance. If the concentration of the complexing agent is too high, the complexing agent content will be too high when the frozen solution melts, causing the complexing agent to complex the aluminum ions and failing to effectively control the difference in precipitation rates between the nickel-cobalt ions and the aluminum ions. If the concentration of the complexing agent is too low, the precipitation rate of the nickel-cobalt ions cannot be effectively reduced, resulting in difficulty in uniform precipitation of the nickel-cobalt-aluminum ions.

[0093] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the ternary positive electrode material disclosed in the present invention, the reaction temperature will affect its performance. When the reaction temperature is controlled at 40-70°C, the performance of the positive electrode material obtained is better. If the reaction temperature is too high, the melting rate is too fast, and it is difficult to ensure uniform precipitation of nickel, cobalt, and aluminum. If the reaction temperature is too low, the reaction rate is too slow, the core of the generated particles is too dense, and lithium ions are difficult to enter, affecting the gram capacity of the material.

[0094] From the comparison between Example 1 and Comparative Example 1, it can be seen that the present invention can be achieved by mixing the frozen Ni / Co mixed solution with the frozen Al 3+ The complexing agent mixed solution is placed in a reflux chamber, and the alkaline solution refluxes and melts, so that the aluminum precipitation reaction proceeds slowly. During this reaction, the alkaline solution and the nickel and cobalt ions precipitate, and the complexing agent only acts on the aluminum ions, thereby avoiding the use of the complexing agent to reduce the precipitation rate of the nickel and cobalt ions.

Claims

1. A method for preparing a ternary positive electrode material, the preparation method comprising the following steps: (1) mixing a nickel source, a cobalt source and a solvent, freezing to obtain a frozen liquid A, mixing an aluminum source, a complexing agent and a solvent, adjusting the pH and freezing to obtain a frozen liquid B, and crushing the frozen liquid A and the frozen liquid B at low temperature, pressing and freezing to obtain a frozen liquid C; (2) placing the frozen liquid C in a reflux device, controlling the alkaline reflux liquid to reflux between the reflux device and the reaction device, and controlling the temperature and pH in the system until the frozen liquid C is completely melted to obtain a suspension; (3) performing solid-liquid separation on the suspension, mixing the obtained solid product with a lithium source, and sintering to obtain the ternary positive electrode material.

2. The preparation method according to claim 1, wherein The nickel source in step (1) includes any one of nickel sulfate, nickel nitrate, nickel chloride or nickel acetate, or a combination of at least two of them.

3. The preparation method according to claim 1 or 2, wherein: The cobalt source includes any one of cobalt sulfate, cobalt nitrate, cobalt chloride or cobalt acetate, or a combination of at least two of them.

4. The preparation method according to any one of claims 1 to 3, wherein The concentration of the nickel source in the freezing liquid A is 0.1-1 mol / L.

5. The preparation method according to any one of claims 1 to 4, wherein: The concentration of the cobalt source in the freezing liquid A is 0.1-1 mol / L.

6. The preparation method according to any one of claims 1 to 5, wherein: The total concentration of the nickel source and the cobalt source in the freezing liquid A is 0.5-2 mol / L.

7. The preparation method according to any one of claims 1 to 6, wherein: The aluminum source in step (1) includes any one of aluminum nitrate, aluminum sulfate or aluminum chloride, or a combination of at least two of them.

8. The preparation method according to any one of claims 1 to 7, wherein: The complexing agent includes any one of acetylacetone, oxalic acid, salicylic acid or sulfosalicylic acid or a combination of at least two thereof.

9. The preparation method according to any one of claims 1 to 8, wherein: Adjusters for adjusting pH include sulfuric acid and / or hydrochloric acid.

10. The preparation method according to any one of claims 1 to 9, wherein: The pH is adjusted to 2-5.

11. The preparation method according to any one of claims 1 to 10, wherein: The concentration of the aluminum source in the freezing liquid B is 0.1-1 mol / L.

12. The preparation method according to any one of claims 1 to 11, wherein: The concentration of the complexing agent in the freezing liquid B is 0.1-0.5 mol / L.

13. The preparation method according to any one of claims 1 to 12, wherein: The freezing temperature in step (1) is -30 to -50°C; Optionally, the freezing time is 6 to 12 hours; Optionally, the temperature of the low-temperature crushing treatment is <-10°C; Optionally, the pressing pressure is 0.1 to 10 MPa; Optionally, the molar ratio of nickel element, cobalt element and aluminum element in the refrigerant C is (0.6-0.9):(0.08-0.3):(0.02-0.1).

14. The preparation method according to any one of claims 1 to 13, wherein: The alkaline reflux solution in step (2) comprises sodium hydroxide solution and / or potassium hydroxide solution; Optionally, the pH of the alkaline reflux solution is 10.5 to 12; Optionally, the reflux rate of the alkaline reflux liquid is 10 to 200 mL / min.

15. The preparation method according to any one of claims 1 to 14, wherein: The method of controlling the pH in the system in step (2) includes adding alkali solution; Optionally, the pH in the control system is 10.5 to 12; Optionally, the concentration of the alkali solution is 5 to 10 mol / L; Optionally, the temperature in the system is 40 to 70°C; Optionally, the frozen liquid C is subjected to aging treatment after being completely melted; Optionally, the aging treatment time is 2 to 20 hours.

16. The preparation method according to any one of claims 1 to 15, wherein: The lithium source in step (3) includes lithium hydroxide and / or lithium carbonate; Optionally, the total molar ratio of the lithium element in the lithium source to the metal element in the solid product is (1-1.1):1; Optionally, the sintering includes one-stage sintering and two-stage sintering; Optionally, the temperature of the first stage sintering is 300-650°C; Optionally, the sintering time is 2 to 10 hours; Optionally, the temperature of the second stage sintering is 700-850°C; Optionally, the second-stage sintering time is 8 to 20 hours.

17. A ternary positive electrode material, wherein the ternary positive electrode material is prepared by the method according to any one of claims 1 to 16.

18. A positive electrode plate, comprising the ternary positive electrode material according to claim 17.

19. A lithium ion battery, comprising the positive electrode sheet according to claim 18.

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