Ternary positive electrode material, secondary battery and preparation method thereof

Abstract

The invention relates to a positive electrode material, in particular to a ternary positive electrode material, a secondary battery and a preparation method of the secondary battery. The preparation method comprises the following steps: (1) mixing a lithium source, a ternary precursor and a metal additive, carrying out first sintering, and crushing and sieving to obtain a sintered material; (2) mixing the sintered material, a water-soluble carbon source, a water-soluble metal salt and water, heating in a closed manner, cooling to room temperature, taking out, and drying to obtain a dried material; and (3) carrying out secondary sintering and sieving on the dried material to obtain the ternary positive electrode material.According to the preparation method of the ternary positive electrode material, the metal additive is firstly added to carry out doping modification on the ternary precursor, then the water-soluble carbon source, the water-soluble metal salt and the water are added at the same time, and the ternary positive electrode material is prepared through the synergistic effect of wet coating and closed heating. The ternary precursor is coated more uniformly, and the ternary positive electrode material is prevented from being corroded by substances such as electrolyte, so that the battery containing the ternary positive electrode material has more excellent electrical properties.

Description

Technical Field

[0001] The invention relates to a positive electrode material, and in particular to a ternary positive electrode material, a secondary battery and a preparation method thereof. Background Art

[0002] Ternary lithium-ion batteries are considered to be the mainstream and future of automotive batteries due to their excellent energy density. High-nickel, low-cobalt ternary cathode materials have become one of the main development directions of ternary cathode materials due to their high theoretical specific capacity. Traditional polycrystalline ternary materials are composed of micron-sized secondary particles (about 1-30μm) composed of densely arranged submicron-sized primary particles (about 50-300nm). However, the capacity and cycle life of polycrystalline ternary cathode materials are challenged by the instability of the layered structure caused by reactions and phase changes during charge and discharge, the mechanical instability between and within the primary particle crystals, and the structural damage caused by oxygen precipitation. High-nickel, low-cobalt ternary cathode materials are more affected due to the lack of the stabilizing effect of cobalt.

[0003] Some functional doping materials and coating materials can improve the above problems to increase capacity and cycle life. For example, carbon-based material coating and various transition metal coatings are cheap, readily available, popular, and commercialized on a large scale. However, when the precursor is doped with a substance and then coated, there is a defect of uneven coating, which causes a decrease in battery performance, and the existing technology needs to be improved.

[0004] Compared with solid phase coating, wet coating can distribute the coating material more evenly, so it can more effectively improve the electrical properties of the positive electrode material. However, the existing improved technology has limited improvement in battery performance and still needs further exploration. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the existing wet coating method has limited improvement on battery performance, thereby providing a ternary positive electrode material, a secondary battery and a preparation method thereof that solve the above-mentioned problem.

[0006] The first aspect of the present invention provides a method for preparing a ternary positive electrode material, which comprises:

[0007] (1) mixing a lithium source, a ternary precursor, and a metal additive, performing a first sintering, and crushing and screening to obtain a sintering material;

[0008] (2) mixing the sintering material, a water-soluble carbon source, a water-soluble metal salt and water, heating in a sealed container, cooling to room temperature, taking out and drying to obtain a dried material;

[0009] (3) The dried material is subjected to a second sintering and sieved to obtain a ternary positive electrode material.

[0010] In the present invention, the room temperature is 25-30°C; when the sintering material, water-soluble carbon source, water-soluble metal salt and water are mixed in step (2), they can be added together, or the water-soluble carbon source, water-soluble metal salt and water can be added first and then the sintering material can be added.

[0011] According to the present invention, the molar ratio of the lithium element in the lithium source to the metal element in the ternary precursor is 1.01-1.09:1, and the metal element in the ternary precursor includes nickel element, cobalt element and manganese element.

[0012] According to the present invention, based on the mass of the ternary precursor, the mass of the metal additive is 0.1-1.5 wt%.

[0013] According to the present invention, the structural formula of the ternary precursor is Ni x Co y Mn (1-x-y) (OH)2, where 0.90≤x≤0.98, 0.01≤y≤0.09.

[0014] According to the present invention, the average particle size of the ternary precursor is 1-15 μm, and can be optionally 2-5 μm.

[0015] According to the present invention, the lithium source includes lithium hydroxide monohydrate and / or anhydrous lithium hydroxide.

[0016] According to the present invention, the metal additive includes metal oxide and / or metal hydroxide.

[0017] According to the present invention, the metal oxide includes a combination of one to four of magnesium oxide (MgO), aluminum oxide (Al2O3), titanium oxide (TiO2), vanadium oxide (VO, VO2, V2O3, V2O5), gallium oxide (Ga2O3), strontium oxide (SrO), yttrium oxide (Y2O3), zirconium oxide (ZrO2), niobium oxide (NbO, Nb2O2, Nb2O3, Nb2O5), molybdenum oxide (MoO3), antimony oxide (Sb2O3, Sb2O5), lanthanum oxide (La2O3), tantalum oxide (Ta2O5), and tungsten oxide (WO3).

[0018] According to the present invention, the metal hydroxide includes a combination of one to four of aluminum hydroxide, magnesium hydroxide, zirconium hydroxide and titanium hydroxide.

[0019] According to the present invention, the temperature of the first sintering is 600-1000° C., preferably 750-900° C.; the time of the first sintering is 6-20 hours.

[0020] According to the present invention, the gas atmosphere of the first sintering is oxygen.

[0021] According to the present invention, the water-soluble carbon source includes at least one of glucose, sucrose, soluble starch and polyvinyl alcohol, preferably glucose.

[0022] According to the present invention, the water-soluble metal salt includes at least one of sulfate, chloride, and soluble carbonate.

[0023] According to the present invention, the sulfate includes a combination of one to four of cobalt sulfate, zinc sulfate, copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate, vanadium sulfate pentahydrate, gallium sulfate, yttrium sulfate, and zirconium sulfate.

[0024] According to the present invention, the chloride salt includes one to a combination of four of cobalt chloride, zinc chloride, copper chloride, iron chloride, magnesium chloride, antimony trichloride and zirconium chloride.

[0025] According to the present invention, the soluble carbonate includes a combination of one or more of sodium carbonate and potassium carbonate.

[0026] According to the present invention, based on the mass of the sintering material, the mass of the water-soluble carbon source is 0.5-2wt%, the mass of the water-soluble metal salt is 0.2-1wt%; and the mass of water is 0.4-0.8 times.

[0027] According to the present invention, the temperature of the sealed heating is 150-200° C., and the time of the sealed heating is 20-60 minutes.

[0028] In the present invention, any container that can provide a closed environment may be used. Typically but not limitedly, the container is a pressure reaction tank.

[0029] In the present invention, the drying temperature is 80-150° C., and the drying time is not limited as long as the drying is complete.

[0030] According to the present invention, the temperature of the second sintering is 200-700° C., preferably 400-600° C., and the time of the second sintering is 4-10 hours.

[0031] According to the present invention, the gas atmosphere of the second sintering is nitrogen or an inert gas, preferably one of nitrogen, argon and helium.

[0032] The second aspect of the present invention protects a ternary positive electrode material obtained by the aforementioned preparation method.

[0033] A third aspect of the present invention provides a secondary battery, wherein the secondary battery comprises the aforementioned ternary positive electrode material.

[0034] Battery preparation method:

[0035] The mass ratio of positive electrode material: carbon black: PVDF is (90-92): (2.5-5): (2.5-5), N-methylpyrrolidone is used as a dispersant, and the mass ratio of PVDF to N-methylpyrrolidone is 1:10-12. The positive electrode slurry is prepared and placed in a centrifuge for 30-40 minutes. The positive electrode slurry is evenly scraped on the carbon-coated aluminum foil and dried in an oven at 100-120°C for 2-3 hours to obtain a dried electrode sheet. The dried electrode sheet is rolled with a roller at 40-45kN, and then dried in an oven at 100-120°C for 2-3 hours. Finally, it is cut with a corresponding size mold to obtain a positive electrode sheet. In an argon atmosphere of a glove box, a Celgard 2500 diaphragm, a lithium metal sheet as the negative electrode, and an LBC3021C011 electrolyte were used to assemble the battery in the order of negative electrode sheet, electrolyte, diaphragm, electrolyte, and positive electrode sheet.

[0036] The technical solution of the present invention has the following advantages:

[0037] 1. The present invention provides a method for preparing a ternary positive electrode material, which comprises: (1) mixing a lithium source, a ternary precursor and a metal additive, performing a first sintering, and crushing and screening to obtain a sintered material; (2) mixing the sintered material, a water-soluble carbon source, a water-soluble metal salt and water, heating in a sealed state, cooling to room temperature and drying to obtain a dried material; (3) performing a second sintering and screening on the dried material to obtain a ternary positive electrode material; In the method for preparing a ternary positive electrode material of the present invention, a metal additive is first added to dope and modify the ternary precursor, and then a water-soluble carbon source, a water-soluble metal salt and water are added at the same time, and the ternary precursor is coated more evenly through the synergistic effect of wet coating and sealed heating, thereby isolating the ternary positive electrode material from the corrosion of the electrolyte and other substances, so that the battery containing the ternary positive electrode material has better electrical properties.

[0038] 2. The specific dosage of the metal additives in the present invention can further enable the metal additives to better penetrate into the layered structure, forming a stable layered structure of the positive electrode material, bringing about a change in the primary particle morphology and an improvement in electrical performance.

[0039] 3. The specific types of metal additives in the present invention can further stabilize the layered structure of the primary particles of the positive electrode material at different positions, resulting in changes in the morphology of the primary particles and improved electrical properties. In addition, the inventors unexpectedly discovered that the layered phase positions of the positive electrode material are limited. When more than four metal additives are added, there is a similar competitive relationship between them, which will lead to a decrease in the doping effect. Therefore, the metal additives in the present invention are preferably a combination of no more than four of any metal oxides and / or metal hydroxides.

[0040] 4. The specific dosage of the water-soluble metal salt of the present invention can further obtain a coating layer of suitable thickness, further reduce a series of side reactions of the positive electrode material with the outside air and the electrolyte, such as lithium hydrogen exchange and HF generation, and at the same time participate in the charge and discharge reaction as a reactant to improve the electrical performance.

[0041] 5. The specific types of water-soluble metal salts of the present invention can not only form metal element coatings, but also further improve the performance of the positive electrode material by coating with anions, thereby improving the electrical performance. At the same time, if the types exceed four, a solid solution phenomenon will occur, forming high-entropy oxides and high-entropy compounds with various properties and completely different performances, resulting in a decrease in the coating effect; therefore, the water-soluble metal salts added in the present invention are selected from four or less of sulfates, chlorides and soluble carbonates.

[0042] 6. The specific amount of the water-soluble carbon source of the present invention can form a coating layer of appropriate thickness, further reducing a series of side reactions of the positive electrode material with the outside air and the electrolyte, such as lithium hydrogen exchange and HF generation, and at the same time, assisting the charge and discharge reaction as a conductive medium to improve the electrical performance.

[0043] 7. The specific type of water-soluble carbon source of the present invention can further promote better dispersion and coating of the water-soluble carbon source on the surface of the positive electrode material through the aqueous solution, thereby improving the coating effect.

[0044] 8. The specific closed heating conditions of the present invention can further promote the uniform dispersion and aggregation of the water-soluble carbon source on the surface of the positive electrode material, resulting in a more uniform coating layer.

[0045] 9. The specific first sintering conditions of the present invention can further promote the full growth of the precursor to form primary crystals of positive electrode material of appropriate size, thereby further optimizing and maintaining the electrical performance of the positive electrode material battery.

[0046] 10. The specific second sintering conditions of the present invention can further promote the stable and uniform formation of the coating layer without affecting the layered structure of the positive electrode material, thereby achieving a relatively optimal coating effect under the same formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 is an electron microscope image of the ternary positive electrode material prepared in Example 1;

[0049] Figure 2 This is an electron microscope image of the ternary positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0050] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0051] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0052] Example 1

[0053] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0054] (1) 600.00 g of Ni with an average particle size of 3.5 μm was added. 0.92 Co 0.06 Mn 0.02 (OH)2 ternary precursor, 281.57g of lithium hydroxide monohydrate, 3.648g of aluminum hydroxide and 1.705g of zirconium oxide were mixed in a high-speed mixer, and the product was placed in a muffle furnace and sintered for 10 hours in an oxygen atmosphere at 850°C, and then crushed, pulverized and sieved to obtain a sintered material.

[0055] (2) 6 g of glucose, 4 g of zinc sulfate, and 300 g of water are placed in a pressure reaction tank and stirred until completely dissolved. 600 g of the sintered material obtained in step (1) is poured in, and the sintered material is stirred and dispersed. The pressure reaction tank is sealed and placed in an oven and heated at 180° C. for 40 min. After cooling to room temperature, the pressure tank is opened and the mixture is dried in an oven at 110° C. until completely dry to obtain a dried material.

[0056] (3) 500 g of the dried material was placed in a muffle furnace and sintered at 600 °C for 6 h in a nitrogen atmosphere. After sieving, the ternary positive electrode material was obtained. Figure 1 It can be seen that the ternary positive electrode material prepared in Example 1 is a single crystal material, and the surface is flat and the coating is relatively uniform.

[0057] Example 2

[0058] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0059] (1) 600.00 g of Ni with an average particle size of 3.5 μm was added. 0.92 Co 0.06 Mn 0.02 After (OH)2 ternary precursor, 275.05g of lithium hydroxide monohydrate, 2.045g of aluminum hydroxide and 0.955g of zirconium oxide were mixed in a high-speed mixer, the product was placed in a muffle furnace and sintered for 6h in an oxygen atmosphere at 850°C. After that, the sintered material was obtained by crushing, pulverizing and sieving.

[0060] (2) 3 g of glucose, 1.2 g of zinc sulfate, and 240 g of water were placed in a pressure reaction tank and stirred until completely dissolved. 600 g of the sintered material obtained in step (1) was poured in and the sintered material was stirred and dispersed. The pressure reaction tank was sealed and placed in an oven and heated at 180° C. for 40 min. After cooling to room temperature, the pressure tank was opened and the mixture was dried in an oven at 110° C. until completely dry to obtain a dried material.

[0061] (3) 500 g of the dried material was placed in a muffle furnace, sintered at 400 °C for 4 h in a nitrogen atmosphere, and sieved to obtain a ternary positive electrode material.

[0062] Example 3

[0063] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0064] (1) 600.00 g of Ni with an average particle size of 3.5 μm was added. 0.92 Co 0.06 Mn 0.02 After (OH)2 ternary precursor, 294.26g of lithium hydroxide monohydrate, 6.145g of aluminum hydroxide and 2.854g of zirconium oxide were mixed in a high-speed mixer, the product was placed in a muffle furnace and sintered for 20h in an oxygen atmosphere at 850°C. After that, the sintered material was obtained by crushing, pulverizing and sieving.

[0065] (2) 12 g of glucose, 6 g of zinc sulfate, and 480 g of water were placed in a pressure reaction tank and stirred until completely dissolved. 600 g of the sintered material obtained in step (1) was poured in and the sintered material was stirred and dispersed. The pressure reaction tank was sealed and placed in an oven for heating at 180° C. for 40 min. After cooling to room temperature, the pressure tank was opened and the mixture was dried in an oven at 110° C. until completely dry to obtain a dried material.

[0066] (3) 500 g of the dried material was placed in a muffle furnace, sintered at 600 °C for 10 h in a nitrogen atmosphere, and sieved to obtain a ternary positive electrode material.

[0067] Example 4

[0068] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0069] The method of Example 1 is followed, except that in step (1), "3.648 g of aluminum hydroxide, 1.705 g of zirconium oxide" is changed to "2.769 g of aluminum hydroxide, 2.584 g of zirconium oxide".

[0070] Example 5

[0071] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0072] The method of Example 1 is followed, except that in step (1), "3.648 g of aluminum hydroxide, 1.705 g of zirconium oxide" is changed to "2.782 g of magnesium hydroxide, 0.854 g of aluminum hydroxide, 0.620 g of magnesium oxide, 1.097 g of molybdenum oxide".

[0073] Example 6

[0074] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0075] The method of Example 1 is the same, except that in step (2), "4 g of zinc sulfate" is changed to "2.5 g of zinc sulfate".

[0076] Example 7

[0077] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0078] The method of Example 1 is the same, except that in step (2), "4 g of zinc sulfate" is changed to "1.2 g of zinc sulfate, 1.4 g of magnesium chloride and 1.4 g of sodium carbonate".

[0079] Example 8

[0080] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0081] The method of Example 1 is followed, except that in step (2), "6 g of glucose" is changed to "4.5 g of glucose".

[0082] Example 9

[0083] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0084] The method of Example 1 is followed, except that in step (2), "6 g of glucose" is replaced by "3 g of sucrose and 3 g of polyvinyl alcohol".

[0085] Example 10

[0086] This embodiment provides a method for preparing a ternary positive electrode material, which is as follows:

[0087] The method of Example 1 is the same, except that in step (2), "the pressure reaction tank is placed in an oven and heated at 180° C. for 40 minutes" is changed to "the pressure reaction tank is placed in an oven and heated at 150° C. for 20 minutes".

[0088] Comparative Example 1

[0089] This comparative example provides a method for preparing a ternary positive electrode material, which is as follows:

[0090] (1) 600.00 g of Ni with an average particle size of 3.5 μm was added. 0.92 Co 0.06 Mn 0.02 After (OH)2 ternary precursor, 281.57g of lithium hydroxide monohydrate, 3.648g of aluminum hydroxide and 1.705g of zirconium oxide were mixed in a high-speed mixer, the product was placed in a muffle furnace and sintered for 10 hours in an oxygen atmosphere at 850°C. After that, the sintered material was obtained by crushing, pulverizing and sieving.

[0091] (2) 600 g of the sintered material prepared in step (1) is placed in 300 g of water, stirred and dispersed, washed with water, filtered, and dried in an oven at 110° C. until completely dry to obtain a dried material.

[0092] (3) 500 g of the dried material and 5 g of glucose were mixed in a high-speed mixer, placed in a muffle furnace, sintered for 6 h at 600 °C in a nitrogen atmosphere, and sieved to obtain a ternary positive electrode material; Figure 2 It can be seen that the ternary positive electrode material prepared in Comparative Example 1 has a large number of obvious island-shaped coated particles on the surface.

[0093] Comparative Example 2

[0094] This comparative example provides a method for preparing a ternary positive electrode material, which is as follows:

[0095] (1) 600.00 g of Ni with an average particle size of 3.5 μm was added. 0.92 Co 0.06 Mn 0.02 After (OH)2 ternary precursor, 281.57g of lithium hydroxide monohydrate, 3.648g of aluminum hydroxide and 1.705g of zirconium oxide were mixed in a high-speed mixer, the product was placed in a muffle furnace and sintered for 10 hours in an oxygen atmosphere at 850°C. After that, the sintered material was obtained by crushing, pulverizing and sieving.

[0096] (2) 600 g of the sintered material prepared in step (1) is placed in 300 g of water, stirred and dispersed, washed with water, filtered, and dried in an oven at 110° C. until completely dry to obtain a dried material.

[0097] (3) 500 g of dried material and 2.5 g of zinc oxide were mixed in a high-speed mixer, placed in a muffle furnace, sintered for 6 h under compressed air at 500 °C, and sieved to obtain a ternary positive electrode material.

[0098] Comparative Example 3

[0099] This comparative example provides a method for preparing a ternary positive electrode material, which is as follows:

[0100] The method of Example 1 is the same, except that in step (2), "the pressure reaction tank is placed in an oven and heated at 180°C for 40 minutes" is changed to "all materials are poured into a beaker, stirred thoroughly, and stirred and heated at 70°C in an open environment for 40 minutes".

[0101] Comparative Example 4

[0102] This comparative example provides a method for preparing a ternary positive electrode material, which is as follows:

[0103] The method of Example 1 is the same as that of Example 1, except that in step (1), 600.00 g of Ni with an average particle size of 3.5 μm is added. 0.92 Co 0.06 Mn 0.02 The (OH)2 ternary precursor and 281.57 g of lithium hydroxide monohydrate were mixed in a high-speed mixer, and the product was placed in a muffle furnace and sintered for 10 h in an oxygen atmosphere at 850°C. The sintered material was then crushed, pulverized and sieved.

[0104] Comparative Example 5

[0105] This comparative example provides a method for preparing a ternary positive electrode material, which is as follows:

[0106] The method of Example 1 is the same, except that in step (2), 10 g of zinc sulfate and 300 g of water are placed in a pressure reaction tank and stirred until completely dissolved, 600 g of the sintered material obtained in step (1) is poured into it, the sintered material is stirred and dispersed, the pressure reaction tank is sealed, and the pressure reaction tank is placed in an oven and heated at 180° C. for 40 min. After cooling to room temperature, the pressure tank is opened, and the mixture is dried in an oven at 110° C. until it is completely dry to obtain a dried material.

[0107] Comparative Example 6

[0108] This comparative example provides a method for preparing a ternary positive electrode material, which is as follows:

[0109] The method of Example 1 is the same, except that in step (2), 10 g of glucose and 300 g of water are placed in a pressure reaction tank and stirred until completely dissolved, 600 g of the sintering material obtained in step (1) is poured into it, and the sintering material is stirred and dispersed, the pressure reaction tank is sealed, and the pressure reaction tank is placed in an oven and heated at 180° C. for 40 min. After cooling to room temperature, the pressure tank is opened, and the mixture is dried in an oven at 110° C. until it is completely dry to obtain a dried material.

[0110] The ternary lithium prepared in the embodiment and the comparative example is used to prepare a lithium ion battery (CR2032 type button half-cell), and the specific method is as follows:

[0111] The mass ratio of positive electrode material: carbon black: PVDF is 90:5:5, N-methylpyrrolidone is used as a dispersant, and the mass ratio of PVDF to N-methylpyrrolidone is 1:10. The positive electrode slurry is prepared and placed in a centrifuge for 30 minutes. The positive electrode slurry is evenly scraped on the carbon-coated aluminum foil and dried in an oven at 100°C for 2 hours to obtain a dried electrode sheet. The dried electrode sheet is rolled at 40kN with a roller press, and then dried in an oven at 100°C for 2 hours. Finally, the positive electrode sheet is obtained by pressing and cutting with a corresponding size mold. In the argon atmosphere of the glove box, Celgard 2500 diaphragm, lithium metal sheet as the negative electrode sheet, LBC3021C011 electrolyte, and the battery is assembled in the order of negative electrode sheet, electrolyte, diaphragm, electrolyte, and positive electrode sheet.

[0112] Then at a temperature of 25°C, charge to 4.25V at a rate of 0.2C, and then discharge to 2.8V at a rate of 0.2C. This is a cycle process.

[0113] First cycle charge and discharge specific capacity = first cycle discharge capacity / mass;

[0114] First-cycle efficiency = first-cycle discharge capacity / first-cycle charge capacity × 100%;

[0115] After 2 cycles, charge to 4.25V at a rate of 0.5C, discharge to 2.8V at a rate of 1C, cycle 52 times, record the charge and discharge capacity of the 3rd cycle and the charge and discharge capacity of the 52nd cycle, and the 1C nominal specific capacity is 180mAh / g;

[0116] 1C discharge specific capacity = discharge capacity at the 52nd cycle / mass;

[0117] Cycle retention rate = (discharge capacity at the 52nd cycle / discharge capacity at the 3rd cycle) × 100%.

[0118] The test results are shown in Table 1.

[0119] Table 1

[0120]

[0121]

[0122] In the preparation method of the ternary positive electrode material of the present invention, a metal additive is first added to dope and modify the ternary precursor, and then a water-soluble carbon source, a water-soluble metal salt and water are added at the same time. Through the synergistic effect of wet coating and closed heating, the ternary precursor is coated more evenly, and the corrosion of the ternary positive electrode material by substances such as the electrolyte is isolated, so that the battery containing the ternary positive electrode material has better electrical properties.

[0123] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing a ternary positive electrode material, characterized in that: include: (1) mixing a lithium source, a ternary precursor, and a metal additive, performing a first sintering, and crushing and screening to obtain a sintering material; (2) mixing the sintering material, a water-soluble carbon source, a water-soluble metal salt and water, heating in a sealed container, cooling to room temperature, taking out and drying to obtain a dried material; (3) The dried material is subjected to a second sintering and sieved to obtain a ternary positive electrode material.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the lithium element in the lithium source to the metal element in the ternary precursor is 1.01-1.09:1; And / or, based on the mass of the ternary precursor, the mass of the metal additive is 0.1-1.5wt%.

3. The preparation method according to claim 1 or 2, characterized in that: The structural formula of the ternary precursor is Ni x Co y Mn (1-x-y) (OH)2, where 0.90≤x≤0.98, 0.01≤y≤0.09; And / or, the average particle size of the ternary precursor is 1-15 μm, optionally 2-5 μm; And / or, the lithium source includes lithium hydroxide monohydrate and / or anhydrous lithium hydroxide; And / or, the metal additive includes metal oxide and / or metal hydroxide; Optionally, the metal oxide includes a combination of one to four of magnesium oxide, aluminum oxide, titanium oxide, vanadium oxide, gallium oxide, strontium oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, antimony oxide, lanthanum oxide, tantalum oxide, and tungsten oxide; Optionally, the metal hydroxide includes a combination of one to four of aluminum hydroxide, magnesium hydroxide, zirconium hydroxide and titanium hydroxide.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature of the first sintering is 600-1000°C, preferably 750-900°C; the time of the first sintering is 6-20h; And / or, the gas atmosphere of the first sintering is oxygen.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The water-soluble carbon source includes at least one of glucose, sucrose, soluble starch and polyvinyl alcohol, preferably glucose.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The water-soluble metal salt includes at least one of sulfate, chloride, and soluble carbonate; Optionally, the sulfate includes a combination of one to four of cobalt sulfate, zinc sulfate, copper sulfate, iron sulfate, magnesium sulfate, aluminum sulfate, vanadium sulfate pentahydrate, gallium sulfate, yttrium sulfate, and zirconium sulfate; Optionally, the chloride salt includes one to four of cobalt chloride, zinc chloride, copper chloride, ferric chloride, magnesium chloride, antimony trichloride, and zirconium chloride; Optionally, the soluble carbonate includes a combination of one or more of sodium carbonate and potassium carbonate; Optionally, based on the mass of the sintering material, the mass of the water-soluble carbon source is 0.5-2wt%, the mass of the water-soluble metal salt is 0.2-1wt%; and the mass of water is 0.4-0.8 times.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The temperature of the sealed heating is 150-200° C., and the time of the sealed heating is 20-60 minutes.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The second sintering temperature is 200-700°C, preferably 400-600°C, and the second sintering time is 4-10h; And / or, the gas atmosphere of the second sintering is nitrogen or an inert gas, preferably one of nitrogen, argon and helium.

9. The ternary positive electrode material obtained by the preparation method according to any one of claims 1 to 8.

10. A secondary battery, characterized in that: The secondary battery comprises the ternary positive electrode material according to claim 9.

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